A Conformable Shape-Stable Self-Healing Polymer Platform for Continuous Wireless Arterial Pulse Monitoring

A Conformable Shape-Stable Self-Healing Polymer Platform for Continuous Wireless Arterial Pulse Monitoring | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article A Conformable Shape-Stable Self-Healing Polymer Platform for Continuous Wireless Arterial Pulse Monitoring Wonryung Lee, Haechang Lee, Joohyuk Kang, Jaewoo Kim This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6919168/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Self-healing polymers offer softness and conformability suitable for skin-interfaced electronics. However, their flowable nature often leads to gradual shape deformation, making them unsuitable for circuit-integrated devices that require structural stability. Here, we introduce a shape-stable self-healing polymer (SS-SHP) featuring a branched polymer network reinforced with reversible imine and hydrogen bonds. The SS-SHP maintained its original shape for 20 days with less than a 5% reduction in storage modulus. In addition, its low Young’s modulus of 576 kPa, comparable to that of skin, allowed conformal contact with microtextured skin surfaces. By embedding Ag flakes into the SS-SHP matrix, we developed a self-healing conductor that showed stable surface resistance over time, avoiding the conductivity degradation typically observed in conventional SHPs. Utilizing the SS-SHP as both the substrate and the electrode matrix, we fabricated a wireless arterial pressure sensor integrated with an optical signal transmission circuit. Due to the skin-like softness of the SS-SHP, the device conformed intimately to the wrist without external contact pressure, enabling precise detection of arterial pulse signals and distinguishing between pulse waveforms from a healthy subject and a pregnant individual. The system successfully translated dynamic pressure fluctuations into real-time optical signals, allowing continuous monitoring of physiological activity through a compact and skin-conformal platform. Physical sciences/Materials science/Soft materials/Polymers Physical sciences/Materials science/Materials for devices/Electronic devices Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Conformal electronics represent a significant advancement in wearable and flexible technology, enabling the seamless integration of electronic functions with the human body. Their high adaptability to complex biological surfaces is essential for next-generation applications that record physiological signals, such as electrocorticogram 1 , 2 , electrocardiogram 3 , electroencephalogram 4 , and arterial pulse 5 . Close conformal contact between electronics and biological tissue minimizes motion artifacts 6 , thereby reducing contact impedance and improving the signal-to-noise ratio. These improvements enhance the accuracy and reliability of physiological signal acquisition 7 , 8 . Traditionally, device conformability has been improved by reducing material thickness, engineering structural design, or employing materials with a low Young’s modulus 2 , 3 , 7 , 9 – 11 . For example, a 1.3 µm thick polydimethylsiloxane (PDMS)-based conductor was used to fabricate a cuff-type ultrathin neural electrode, which exhibited lower noise levels compared to thicker electrodes during neural signal recording 12 . A combinatorial strategy has been proposed to integrate ultra-thin substrates with structural design or soft materials. For instance, a 2.6 µm-thick multielectrode array combined with a mesh structure enabled motion artifact-free electroanatomical mapping on the dynamically moving surface of a rat’s heart 3 . Moreover, a 7 µm-thick hydrogel with a low Young’s modulus of 12.9 kPa was used to fabricate a biocompatible cardiac patch capable of long-term physiological monitoring 11 . Recently, self-healing polymers (SHPs) have emerged as promising materials for conformal bioelectronics, due to their ability to dynamically reconstruct their soft polymer networks to adapt to contact surfaces. The high conformability of SHPs is attributed to their linear molecular structure and dynamic supramolecular networks, which induce a low Young’s modulus and high flowability 13 – 18 , thereby enabling efficient adaptation to irregular topographies 19 , 20 . Unlike highly crosslinked polymers, where covalent bonds restrict molecular flexibility, SHPs rely on dynamic hydrogen bonds (H-bonds) 21 – 23 . These reversible, non-covalent interactions enable rapid polymer chain rearrangement, allowing SHP-based devices to conform instantly to dynamically changing biological surfaces. For example, to minimize mechanical mismatch at the tissue-device interface, a cuff-type neural interface was developed using SHPs, whose intrinsic self-healing and adaptive properties allowed conformal, suture-free integration with peripheral nerves 24 . Furthermore, a self-healing electronic device designed for the urinary bladder was developed to conform to dynamically expanding tissue, enabling continuous physiological monitoring and electrical stimulation 25 . However, applying SHPs to electronic devices remains challenging due to the inherent trade-off between shape-adaptability and shape-stability 26 , 27 . While their flowable nature enables intimate contact with irregular biological surfaces, it also leads to time-dependent deformation that compromises shape-stability. In particular, linear structures of SHPs exhibit high water vapor permeability, enabling water molecules to infiltrate the polymer network, break H-bonds between polymer chains, and form new H-bonds with the infiltrated water 28 – 31 . This progressive bond disruption gradually weakens the shape-stability of the SHPs over time, accelerates structural collapse, and ultimately leads to electrical short circuits, impairing the reliable operation of SHP-integrated circuits 32 , 33 . Various studies have attempted to reduce flowable behavior of SHPs to improve mechanical robustness 34 – 36 ; however, such approaches often lead to an increase in Young’s modulus to the range of 3–50 MPa 37 – 39 , which compromises their conformal integration with biological tissues such as skin (~ 600 kPa 40 ). Moreover, excessive suppression of viscous flow adversely affects self-healing time and stretchability 32 , 41 . Thus, the intrinsic trade-off makes it difficult to design SHPs that maintain high shape-adaptability while suppressing flowable nature, thereby limiting their integration into robust and long-term functional electronic systems. In this work, we developed a shape-stable self-healing polymer platform (SS-SHP) that combines long-term shape retention with skin-like mechanical softness, enabling its use in conformal, circuit-integrated wearable electronics. The SS-SHP features a branched polymer network constructed through reversible imine bonds and H-bonds, which effectively suppress water diffusion into the matrix and enhance resistance to shape deformation. The SS-SHP preserved its original shape without dimensional change, and its storage modulus decreased by less than 5%, confirming long-term structural and mechanical stability over a 20-day period. Notably, the SS-SHP exhibited a mechanically stable structure with a low Young’s modulus of 576 kPa, comparable to that of human skin (~ 600 kPa) 40 , enabling high conformability to microscale wrinkles on the fingertip. Beyond serving as a substrate, the SS-SHP was also utilized as a polymer matrix for conductive electrodes by incorporating Ag flakes. Unlike conventional SHP-based conductors, which showed conductivity degradation due to sedimentation of Ag flakes, the SS-SHP-based conductors exhibited time-independent resistance over 2 weeks. To demonstrate the practical utility of the SS-SHP platform, we fabricated a wireless arterial pressure monitoring system designed to minimize the use of rigid components and preserve the intrinsic conformability of the SS-SHP. Instead of integrating bulky electronic chips, a single infrared light-emitting diode (IR LED) was employed for wireless optical signal transmission 6 . The resulting device conformed intimately to the curved surface of the wrist, enabling accurate arterial pulse detection without external contact pressure and successfully distinguishing pulse waveforms between healthy individuals and pregnant women 42 . Notably, dynamic pressure fluctuations generated by arterial pulses were converted into real-time optical signals through modulation of IR LED brightness, enabling continuous monitoring of physiological signals using a skin-conformal wireless sensing system. 2. Results and discussion Figure 1 a, b schematically illustrates the differences between a conventional shape-flowable self-healing platform and a newly developed shape-stable self-healing platform. Figure 1 a shows the conventional self-healing polymer (SHP), which consists of linear polymer chains interconnected solely through hydrogen bonds (H-bonds) 21 , 23 . These weak intermolecular interactions result in a highly dynamic and flowable material that can adapt to irregular surfaces. However, this flowable behavior poses significant challenges in constructing integrated circuits 33 , as continuous deformation can distort electrode geometry, increasing the risk of electrical short circuits and ultimately compromising the reliable operation of electronics. The shape-stable self-healing polymer (SS-SHP) developed in this study, as shown in Fig. 1 b, features a branched molecular architecture reinforced by a dual-network structure of reversible covalent imine bonds and H-bonds. This architecture significantly enhances mechanical robustness, suppressing undesirable deformation while preserving self-healing capabilities. The dual-network design not only prevents structural collapse but also ensures long-term shape-stability, enabling reliable mechanical performance and seamless integration into electronic systems. As a result, the SS-SHP provides a mechanically stable platform for self-healing electronic devices, preserving electrode geometry and preventing electrical short circuits and performance degradation. The shape-stability of the SS-SHP facilitated the construction of an integrated circuit for wireless pulse pressure monitoring. As shown in Fig. 1 c, a fully assembled device was conformally mounted on the wrist, consisting of a wireless power receiver, a pressure sensor for pulse detection, and an optical data transmission component. Each component was seamlessly integrated to form a compact, skin-conformal platform. The corresponding schematic illustration in Fig. 1 d details the materials and functional components of the system. The substrate was composed of the SS-SHP, while the electrodes were made of a shape-stable self-healing conductor (SS-SHC) incorporating Ag flakes (AgFs) within the same SS-SHP matrix. The pressure sensing unit consisted of a piezoresistive sensor fabricated by coating poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) onto sandpaper-imprinted PDMS 42 , enabling the detection of subtle pressure changes induced by arterial pulsation. The wireless circuitry included inductive coupling for power transmission 43 , 44 and optical signal transmission via an infrared light-emitting diode (IR LED), which operates in a wavelength range minimally affected by ambient visible light, thus reducing optical noise and enabling stable signal readout under various lighting conditions 45 , 46 . The entire system demonstrated high skin conformability, emphasizing the potential of the SS-SHP-based platform for robust and wearable self-healing bioelectronic applications. To facilitate a comparison based on molecular architecture, the conventional SHP used in this study was designed as a PDMS-based linear elastomer, which is widely employed in skin-interfaced biomedical devices due to its biocompatibility and flexibility 13 , 47 , 48 . As shown in Fig. 2 a and Supplementary Fig. 1a , this material was synthesized by reacting bis(3-aminopropyl)-terminated PDMS (H 2 N-PDMS-NH 2 ) with 4,4'-Methylenebis(cyclohexyl isocyanate) (MCI) to form linear PDMS-MCI chains. The formation of urea groups from this reaction was confirmed by a new Fourier-transform infrared (FT-IR) absorption peak at 1630 cm − 1 , corresponding to C = O stretching ( Supplementary Fig. 1b ). The resulting elastomer is crosslinked via urea bonds 49 , which form H-bonds serving as dynamic self-healing sites. However, the linear structure of the conventional SHP exhibits high water permeability, allowing water molecules to diffuse into the polymer network. This diffusion breaks existing interchain H-bonds, leading to the formation of water-polymer H-bonds instead. This progressive bond disruption weakens intermolecular interactions, thereby degrading the polymer network, ultimately leading to mechanical instability over time. To suppress progressive shape deformation, we developed the SS-SHP featuring a branched architecture, as illustrated in Fig. 2 b. In this design, the linear PDMS-MCI chains are covalently linked via reversible imine bonds formed through a Schiff base reaction with 1,3,5-triformylbenzene (TFB), a trifunctional aldehyde ( Supplementary Fig. 1a ). The reaction between the –NH 2 groups of PDMS-MCI and the –CHO groups of TFB results in C = N imine bonds, confirmed by a new FT-IR peak at 1645 cm − 1 ( Supplementary Fig. 1b ). Each TFB molecule connects with up to three PDMS-MCI chains, yielding a branched polymer network. Within the SS-SHP, both H-bonds and imine bonds function as self-healing sites. Unlike the linear molecular system, however, the branched structure significantly restricts water diffusion, effectively preventing moisture-induced degradation. This architecture confers enhanced mechanical robustness and long-term shape-stability, addressing the limitations of conventional H-bonded linear SHPs. To compare the water permeability of the conventional SHP (PDMS-MCI) and the SS-SHP (PDMS-MCI-TFB), FT-IR spectroscopy was performed on both materials before and after immersion in phosphate-buffered saline (PBS) for 1 day (Fig. 2 c). After immersion, the samples were dried under ambient conditions (defined throughout this study as 20°C and 40% relative humidity) for 10 hr to remove surface moisture while retaining absorbed water within the polymer networks. The FT-IR spectra revealed changes in the hydroxyl (–OH) stretching vibration band near 3330 cm − 1 , which serves as a key indicator of water absorption. As shown in the magnified graphs of Fig. 2 c, the conventional SHP exhibited a pronounced increase in the –OH peak intensity following PBS immersion, while the SS-SHP showed minimal change. This result suggests that the conventional SHP absorbs significantly more water due to its high moisture permeability and low network integrity 28 – 30 , which can lead to gradual deformation over time. In contrast, the branched-chain architecture of the SS-SHP effectively limits water diffusion into the network, thereby enhancing water resistance and preserving long-term shape retention. To assess the long-term shape-stability of the materials, we first measured the storage modulus, which indicates the elastic stiffness of a material and its ability to resist shape deformation under stress. A time-independent storage modulus is indicative of superior shape-stability. Samples were stored for 20 days under ambient conditions and analyzed using a rheometer (Fig. 2 d). The SS-SHP exhibited a moderate decrease in storage modulus from 3 × 10 4 Pa to 5 × 10 3 Pa, while the conventional SHP showed a sharp drop from 10 5 Pa to 10 3 Pa after 20 days. This result indicates that the SS-SHP maintains its structural form more effectively under prolonged environmental exposure. To further evaluate the shape retention against structural collapse at the macroscopic level, we assessed the deformation of the SS-SHP and the conventional SHP samples over time by measuring the shape angle formed between the sample and a flat glass substrate. Samples (~ 300 µm thick) were placed on a glass surface and stored under ambient conditions for 20 days ( Supplementary Fig. 2 ). As shown in Fig. 2 e, side-view photographs revealed that the SS-SHP maintained an upright shape with a shape angle near 90°, whereas the conventional SHP exhibited significant collapse. Quantitative analysis of shape angle over 20 days showed a gradual decline from 90° to 58° in the conventional SHP (Fig. 2 f), whereas the SS-SHP maintained a stable angle of 90° throughout the period. Together, these results demonstrate that the branched network of the SS-SHP, incorporating imine bonds derived from TFB and H-bonds introduced by MCI, significantly enhances long-term shape-stability compared to the conventional linear SHPs. To characterize the robustness of the SS-SHP, mechanical tensile tests were performed. Figure 3 a presents photographs of the optimized SS-SHP (PDMS-MCI 0.7 -TFB 0.3 ) being stretched to over 1000% strain without mechanical failure, visually highlighting its exceptional stretchability. The mechanical properties of the SS-SHPs could be tuned by varying the molar ratio of MCI to TFB. Figure 3 b shows the stress-strain curves for PDMS-MCI x -TFB 1 − x compositions, while the corresponding toughness values calculated from the area under each curve are shown in Fig. 3 c. Among the tested formulations, PDMS-MCI 0.7 -TFB 0.3 exhibited the highest ultimate tensile strength (> 2 MPa at 1000% strain) and toughness (9.75 MJ/m 3 ), making it the most mechanically robust composition. This enhanced mechanical performance is attributed to the incorporation of TFB, a trifunctional aldehyde that promotes the formation of a branched network via reversible imine bonding. Notably, the mechanical properties exhibit a strong dependence on the TFB content. When the amount of TFB exceeded the optimized ratio, excess TFB led to an increased number of unreacted aldehyde groups due to the limited availability of amine groups in PDMS, thereby reducing the effective crosslinking density and diminishing mechanical strength. This was confirmed by FT-IR analysis, which revealed a stronger C–H stretching vibration peak (2824 cm − 1 ) 50,51 of the aldehyde groups in PDMS-MCI 0.6 -TFB 0.4 and PDMS-MCI 0.5 -TFB 0.5 compared to samples with lower TFB content ( Supplementary Fig. 3 ), indicating a higher concentration of unreacted aldehydes. Based on its superior toughness and optimized crosslinking, PDMS-MCI 0.7 -TFB 0.3 was selected for all subsequent experiments. To evaluate durability under cyclic mechanical loading, the optimized SS-SHP was subjected to 100 cycles of 100% stretching ( Supplementary Fig. 4 ). The material retained its mechanical resilience without noticeable performance degradation, confirming its suitability for long-term use in stretchable electronic applications. The self-healing capability of PDMS-MCI 0.7 -TFB 0.3 was assessed through tensile recovery experiments. As shown in Fig. 3 d, the sample was cut and left to self-heal under ambient conditions for 24 hr. After healing, the sample recovered an ultimate tensile strength of 1.78 MPa and a stretchability of 1026%, compared to pristine values of 2.05 MPa and 1032%, respectively. To quantify healing efficiency over time, stress-strain curves were obtained after 6, 12, and 24 hr of healing (Fig. 3 e), and the recovery ratios in tensile strength and stretchability were calculated (Fig. 3 f). After 24 hr, the sample recovered 86.8% of its original tensile strength and 99.4% of its stretchability, demonstrating efficient self-healing performance enabled by dynamic imine and H-bond interactions. Figure 4 a compares the conformability of the SS-SHP and PDMS (Sylgard 184, base:curing agent = 10:1, Dow Corning), both fabricated with a similar thickness of approximately 50 µm, when placed on a human fingertip. The SS-SHP (Fig. 4 a, left) conforms closely to the skin wrinkles, demonstrating superior surface adaptability, whereas the PDMS (Fig. 4 a, right) fails to follow the curved skin features, resulting in visible interfacial gaps. This difference arises from the mechanical properties of the materials: the SS-SHP exhibits a much lower Young’s modulus (~ 576 kPa) compared to PDMS (~ 1.47 MPa), enabling it to deform more easily and adhere intimately to soft, curved skin surface ( Supplementary Fig. 5 ). To quantitatively compare surface adaptation performance, a skin replica mimicking the wrinkled texture of a fingertip was fabricated (Fig. 4 b, left), and both materials were placed on its surface (Fig. 4 b, middle and right; Supplementary Fig. 6 ). The SS-SHP adhered tightly to the replica, reproducing fine wrinkle patterns, while PDMS floated above the surface without capturing the contour features. Quantitative analysis of surface adaptation was performed using a 3D measuring laser microscope. The surface profiles at the material-replica interface were extracted (Fig. 4 c), and the total contour length ( L ) of each material was calculated. This value was then normalized against the contour length of the skin replica ( L 0 ) to determine conformability (Fig. 4 d). The SS-SHP exhibited a normalized contour length of 90%, indicating excellent surface adaptation. The conventional SHP showed a comparable value with only a 2% difference, while PDMS exhibited a significantly lower normalized length of 42%, reflecting its limited ability to adapt to the replica’s micro-texture. These results demonstrate that the SS-SHP offers significantly enhanced conformability compared to PDMS, making it a more suitable substrate for skin-interfaced devices. To implement functional circuits on the self-healing platform, a shape-stable self-healing conductor (SS-SHC) was developed by embedding AgFs into the SS-SHP matrix (Fig. 5 a and Supplementary Fig. 7 ), ensuring consistent material properties and cohesive integration. To evaluate its mechanical durability and self-healing performance, stress-strain behavior was examined through tensile testing (Fig. 5 b). Dog-bone-shaped samples were fabricated by screen-printing SS-SHC ink onto the SS-SHP substrate using a polyimide (PI) mask with a dog-bone-shaped opening (Supplementary Fig. 8a ). The printed SS-SHC samples were then cut and allowed to self-heal under ambient conditions. After 24 hr, the self-healed SS-SHC exhibited a tensile strength of 1.3 MPa at 900% strain. Compared to the pristine sample (1.76 MPa at 980% strain), the fracture strain was restored to 91.8% and the tensile strength to 78.7%, demonstrating the material’s excellent mechanical self-healing performance. During the tensile test, electrical resistance was measured to assess the recovery of electrical properties after self-healing (Fig. 5 c). The samples maintained electrical conductivity under strains up to ~ 700%, and the resistance increased by only 11% after 24 hr of healing and recovered to within 0.2% of the original value after 48 hr, confirming the effective re-establishment of conductive pathways. To evaluate the recovery of electrical performance after damage, an IR LED was integrated into the SS-SHC electrode and operated under a constant 1 V (Fig. 5 d and Supplementary Fig. 8b ). In the pristine state, the IR LED remained turned on, indicating continuous electrical conduction. When the SS-SHC electrode connected to the anode side of the IR LED was cut, the conductive path was interrupted, and the IR LED immediately turned off. After 24 hr of self-healing under ambient conditions, the IR LED turned on again, demonstrating successful restoration of electrical connectivity. This recovery behavior was further confirmed by scanning electron microscopy (SEM) imaging of the cut region before and after healing (Fig. 5 e). After cutting, a distinct rupture was observed with separated AgFs, indicating disruption of the conductive network. After 24 hr, the AgFs were redistributed and reconnected across the previously cut region, re-establishing a continuous conductive pathway. The time-dependent electrical recovery was quantified by monitoring the current through the IR LED (Fig. 5 f). Approximately 60% of the original current was restored within 10 s (Fig. 5 f, inset), and 94% was recovered after 24 hr, confirming the rapid and efficient electrical self-healing capability of the SS-SHC. To compare the effect of matrix structure on the dispersion stability of AgFs, conventional SHP and SS-SHP were each used to fabricate composite conductors (conventional SHC and SS-SHC) by incorporating AgFs under identical weight ratios. Tilted cross-sectional SEM images were analyzed after 2 weeks of aging to observe both surface and subsurface changes in the distribution of AgFs (Fig. 5 g). Initially, both SHCs exhibited uniform dispersion of AgFs throughout the matrix ( Supplementary Fig. 9 ). However, after 2 weeks, distinct differences emerged: in the conventional SHC, AgFs gradually sank toward the bottom, indicating sedimentation due to the flowable nature of the linear SHP (Fig. 5 h, bottom). In contrast, the SS-SHC maintained a consistent distribution of AgFs, demonstrating that its shape-stable matrix effectively prevents long-term morphological changes (Fig. 5 h, top). This dispersion stability of AgFs is directly linked to the electrical reliability of the conductor. In practical electronic systems, resistance drift over time can lead to signal distortion, reduced sensor sensitivity, or circuit malfunction 52 . To assess this, the surface resistances of both SHCs were measured daily over 2 weeks (Fig. 5 i). The SS-SHC exhibited excellent stability, with only a 3% increase ( R / R 0 = 1.03), whereas the conventional SHC showed severe degradation 53 , with resistance rising to R / R 0 = 7.7. These results confirm that the SS-SHP matrix effectively suppresses sedimentation of AgFs, preserving conductive pathways and ensuring long-term electrical performance, making the SS-SHC suited for use in integrated, durable soft electronics. To demonstrate the practical application of the SS-SHP platform in wearable sensing systems, a piezoresistive pressure sensor was fabricated by integrating the SS-SHC as the electrode on the SS-SHP substrate. The pressure-sensing layer was formed by coating PEDOT:PSS onto a sandpaper-imprinted PDMS surface ( Supplementary Fig. 10 ). For comparison, a control sensor using PDMS substrate was also fabricated. As illustrated in Fig. 6 a, the SS-SHP-based sensor conformed intimately to the curved surface of the wrist, ensuring tight contact and effective transmission of arterial pulse pressure to the sensor. In contrast, the PDMS-based sensor exhibited poor conformal contact with the skin, resulting in interfacial gaps that reduced pulse signal transmission efficiency. To evaluate sensing performance, wrist pulse signals were recorded without applying external pressure. As shown in Fig. 6 b, the SS-SHP-based sensor successfully detected regular pulse patterns, whereas the PDMS-based sensor failed to capture any discernible signal due to poor contact. The PDMS sensor required an external pressure of 20 kPa to enable pulse detection, indicating that adequate conformal contact is a prerequisite for accurate signal measurement ( Supplementary Fig. 11 ). Furthermore, the SS-SHP-based pressure sensor was used to differentiate between physiological pulse patterns of a healthy individual and a pregnant woman (Fig. 6 c). The healthy subject displayed a stable and periodic pulse waveform, while the pregnant subject exhibited irregular and fluctuating signals, consistent with prior studies indicating altered cardiovascular dynamics during pregnancy 54 , 55 . To evaluate the wearable applicability of the highly conformable pressure sensor, a wireless pulse pressure sensor was fabricated by integrating all functional components—including the pressure sensor, wireless power receiver, and optical transmitter—onto the SS-SHP substrate (Fig. 6 d). The device incorporated SS-SHC electrodes, a pressure-sensing layer composed of imprinted PDMS coated with PEDOT:PSS, and an IR LED for optical signal transmission (Fig. 6 e). The IR LED was selected to enable real-time wireless data communication with a single component, thereby avoiding bulky or rigid circuit elements and preserving the overall conformability of the device. The corresponding circuit diagram is presented in Fig. 6 f; the system was wirelessly activated via inductive coupling using an alternating current (AC) power source operating in the MHz frequency range. The overall fabrication process is detailed in Supplementary Fig. 12 . After fabrication, the device was folded to ensure direct contact between the pressure-sensing region and the wrist. To operate the system, an external transmitting coil was placed above the device for wireless power delivery, and real-time changes in IR LED brightness—modulated by pulse-induced resistance variation—were captured using an IR camera (Fig. 6 g). As shown in Fig. 6 h, the pressure-induced resistance changes modulated the current through the IR LED, resulting in brightness variations that were quantified by extracting gray values from IR camera images. The sensor demonstrated a high sensitivity of approximately 0.075 kPa⁻¹ (Δ( R / R 0 )/Δ P ) under 15 kPa, which corresponds to the typical range of pulse pressure at the wrist 56 . This confirms its suitability for detecting subtle physiological pressure variations during pulse monitoring. Supplementary Fig. 13 validates the visual emission stability of the IR LED under AC power. When the IR LED was powered using AC signals from 1 Hz to 1 MHz, the IR camera captured alternating brightness at low frequencies ( 10 3 Hz), the frame-to-frame brightness appeared visually constant due to temporal averaging by the camera, resulting in stable output similar to that of direct current (DC) operation. This is because the frequency of the wireless power signal exceeds the shutter speed of the IR camera (196 frames/s), making the LED flickering imperceptible and enabling continuous brightness capture. Optically acquired pulse waveforms are presented in Fig. 6 i, showing clear brightness fluctuations that correspond to systolic and diastolic phases; higher brightness during low resistance (systole) and lower brightness during high resistance (diastole). The full video of this measurement is provided in Supplementary Video 1 , where real-time fluctuating pulse signals can be visually observed via IR LED flickering. Additionally, Supplementary Fig. 14 compares the pulse signals acquired optically (gray value) with those obtained from electrical measurements (resistance), showing strong correlation between the two methods, as the optically observed P 1 and P 2 peaks closely matched those from electrical signals. These results confirm the reliability of the optical readout and highlights the system’s potential for continuous, non-invasive cardiovascular monitoring. 3. Conclusion In this study, we established a highly stable and skin-conformal materials platform for self-healing electronics by developing a shape-stable self-healing polymer (SS-SHP) and integrating it into a wireless pulse pressure sensing system. This platform overcomes major limitations of conventional self-healing electronics by: (1) improving shape retention through a dual-network polymer design comprising reversible imine and hydrogen bonds, (2) enabling the fabrication of a shape-stable self-healing conductor (SS-SHC) with long-term electrical reliability, and (3) demonstrating a fully integrated, wireless, and conformable sensor capable of real-time and continuous monitoring of dynamic physiological signals. The SS-SHP maintained its original shape over 20 days under ambient conditions, while the SS-SHC exhibited time-independent electrical resistance by suppressing the sedimentation of Ag flakes, unlike conventional SHC. The wireless device incorporated a pressure sensor, inductive power receiver, and IR LED-based optical transmitter, all integrated into the SS-SHP substrate. This configuration enabled the detection of arterial pulse signals without external pressure and distinguished physiological differences between healthy and pregnant individuals. Moreover, real-time monitoring of pulse waveforms was successfully achieved via optical signal transmission, enabling wireless and continuous physiological sensing. The platform’s mechanical stability, electrical reliability, and wireless integration offer a promising foundation for next-generation soft bioelectronic systems designed for long-term health monitoring and therapeutic applications. 4. Experimental Section Materials : Aminopropyl-terminated polydimethylsiloxane (NH 2 -PDMS-NH 2 , DMS-A21, Mn ~ 5000 g/mol) was obtained from Gelest, Inc. 4,4'-Methylenebis(cyclohexyl isocyanate) (MCI, 90%) and 1,3,5-triformylbenzene (TFB, 98%) were purchased from Sigma-Aldrich and Tokyo Chemical Industry Co., respectively. 1X phosphate-buffered saline (PBS) was purchased from WELGENE. Sylgard 184 PDMS was purchased from Dow Corning. Methyl isobutyl ketone (MIBK) was purchased from Daejung Chemicals. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS, Clevios PH 1000) was provided by Heraeus. Ag flakes (AgFs, DSF-500MWZ-S) were from Daejoo Electronics. Sandpaper (#320 mesh) was purchased from DEERFOS. Novec 7100 and Novec 1700 were obtained from 3M. (3-Glycidyloxypropyl)trimethoxysilane (GOPS), dodecylbenzenesulfonic acid (DBSA), and ethylene glycol were used as PEDOT:PSS additives. Synthesis of SS-SHP : The shape-stable self-healing polymer (SS-SHP) was synthesized in a two-step process. First, NH 2 -PDMS-NH 2 (12 g) was dissolved in MIBK (30 mL), and MCI (0.1 g) was added. The mixture was stirred at room temperature (20°C) for 24 hr to yield linear PDMS-MCI (conventional SHP). Then, TFB (0.0154 g) was added, followed by 10 min ultrasonication and 6 hr magnetic stirring. The resulting solution was cast or doctor-bladed onto antiadhesive-treated glass substrates (pre-treated with Novec 7100 and Novec 1700, 3:1 vol ratio) and dried at room temperature for 24 hr to form a transparent elastomer. The final composition PDMS-MCI 0.7 -TFB 0.3 was identified as the optimized SS-SHP based on mechanical testing. Variants with different MCI:TFB molar ratios (0.9:0.1 to 0.5:0.5) were also prepared for comparison. Chemical and mechanical characterization of SS-SHP : To evaluate the chemical structure and water permeability, Fourier-transform infrared (FT-IR) spectroscopy (Nicolet iS20, Thermo Scientific) was performed on SS-SHP and conventional SHP samples. To investigate shape-stability, rectangular films of SS-SHP and conventional SHP (2 cm × 2 cm, ~ 300 µm thick) were placed on a flat glass substrate and stored under ambient conditions (20°C, 40% relative humidity) for 20 days. Contact angle measurements (Smartdrop, Femtofab) were conducted by capturing side-view images before and after aging. The angle between the vertical edge of the film and the glass surface was analyzed using ImageJ software to evaluate macroscopic collapse over time. Tensile stress-strain tests were conducted using a universal testing machine (5966, Instron Corporation) to evaluate mechanical robustness. Samples with dimensions of 10 mm × 5 mm × ~0.5 mm were stretched at a rate of 200%/min under ambient conditions. To assess self-healing performance, samples were completely cut and gently realigned, then self-healed under ambient conditions for 6, 12, or 24 hr. After healing, tensile testing was repeated, and self-healing efficiency was calculated as the ratio of recovered stretchability to that of the pristine film. Fabrication of SS-SHC and IR LED integration : To fabricate the shape-stable self-healing conductor (SS-SHC) electrode, a conductive ink was prepared by mixing AgFs (5 g) with the SS-SHP solution (3 g). The mixture was magnetically stirred for 3 hr at room temperature to ensure uniform dispersion of the AgFs within the polymer matrix. For patterning, a polyimide (PI) stencil mask featuring a dog-bone-shaped opening was placed on the SS-SHP film (thickness ~ 140 µm), and the SS-SHC ink was applied over the mask using a blade. After removing the stencil, the patterned conductor was dried at room temperature to yield the dog-bone-shaped SS-SHC electrode. Following electrode fabrication, an infrared light-emitting diode (IR LED, QBLP650-IR3, QT Brightek) was integrated into the SS-SHC to evaluate electrical self-healing performance. Ethanol was dropped onto the printed SS-SHC electrode to slightly soften the surface and improve contact, and the IR LED terminal was gently pressed into place to form an electrical junction. The assembly was then left at room temperature to allow stable bonding between the LED and the self-healing conductor. The full fabrication process, including dog-bone electrode formation and IR LED integration, is illustrated in Supplementary Fig. 8 . Electrical characterization of SS-SHC : Stretchability and resistance were measured using an automatic stretch-testing machine (Jaeil Optical System) while continuously monitoring electrical resistance with a digital multimeter (DMM6500, Keithley). For self-healing assessment, the SS-SHC samples were completely cut and left to heal under ambient conditions. Resistance recovery and stretchability were evaluated after healing. Electrical reliability was further analyzed by measuring surface resistance daily over a 2-week period. Changes in AgF distribution were characterized using tilted cross-sectional scanning electron microscope (SEM, Inspect F50, FEI) imaging, while time-dependent resistance ( R / R 0 ) was plotted to compare the SS-SHC with conventional SHC formulations. Fabrication of PEDOT:PSS-based microstructured pressure sensor : An antiadhesive layer was formed by treating sandpaper with Novec 7100:1700 (3:1). PDMS was spin-coated onto the sandpaper at 300 rpm for 100 s, vacuum degassed, and cured at 100°C for 30 min. The microstructured PDMS layer was peeled and placed upside down on an antiadhesive-treated glass. After O 2 plasma treatment (50 W, 30 s), a PEDOT:PSS mixture (10 g PEDOT:PSS, 0.1 g GOPS, 0.01 g DBSA, 0.5 g ethylene glycol) was spin-coated at 700 rpm for 100 s and cured at 150°C for 30 min to form a pressure-sensitive layer. The fabrication process is shown in Supplementary Fig. 10 . Fabrication of wireless pulse pressure monitoring device : A 50 µm-thick SS-SHP substrate was fabricated by doctor blade coating the SS-SHP solution onto an antiadhesive-treated slide glass. The wireless circuit—comprising the power receiving coil, pressure sensor electrodes, and the interconnects for the IR LED—was patterned onto the substrate by screen-printing the SS-SHC ink through a stencil PI mask. Before the printed SS-SHC ink was fully dried, two critical components were integrated: (1) the IR LED was placed onto the patterned electrode area to form direct electrical contact, and (2) the pressure-sensing layer—consisting of sandpaper-imprinted PDMS coated with PEDOT:PSS—was laminated onto the designated region to complete the sensor assembly. After all components were integrated, the device was gently detached from the glass substrate and folded so that the IR LED faced outward and the pressure sensor faced inward, enabling tight, conformal contact with the skin during pulse monitoring. The full fabrication process is illustrated in Supplementary Fig. 12 . Wireless power transmission and optical signal monitoring : A transmitting coil resonant at 3.67 MHz was designed using a vector network analyzer (ZNLE4, Rohde & Schwarz). A function generator (AFG1062, Tektronix) was used to apply a sinusoidal AC voltage to the coil, enabling wireless power transfer via inductive coupling to the IR LED integrated within the sensor device. To evaluate optical signal transmission, the IR LED emission was recorded using an IR camera (BFS-U3-17S7M-C, FLIR) equipped with a lens (V2528-MPY, Computar). The NIR camera was configured with a resolution of 1600 × 1100 pixels, an f/8 aperture, and a shutter speed of 196 frames/s. To enhance measurement accuracy and eliminate interference from ambient light sources, an IR long-pass filter (LP780, Midwest Optical Systems) was mounted on the camera, allowing only wavelengths above 780 nm to pass. Captured images were processed using ImageJ software. Regions of interest corresponding to the IR LED were cropped, and grayscale pixel values were extracted from each frame to track brightness variations over time. These time-dependent gray values reflect current-induced optical output fluctuations, thereby enabling quantitative assessment of pressure-induced signal changes. Human pulse monitoring in healthy and pregnant individuals : All procedures involving human participants were approved by the Institutional Review Board (IRB) of the Korea Institute of Science and Technology (IRB No. KIST-202306-HR-001) and conducted in accordance with institutional guidelines. Pulse monitoring experiments were performed on two subjects: a healthy male in his 20s and a pregnant woman in her 8th month of gestation. The pressure sensor was conformably attached to the wrist, specifically over the radial artery. Pulse signals were measured under resting conditions after ensuring stable respiration and heart rate. Declarations Acknowledgments This research was supported through the Industry Technology Alchemist Project (20025702, “Development of smart manufacturing multiverse platform based on multisensory fusion avatar and interactive AI”) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea). This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (Grant No. RS-2025-00519762). This research was supported by Korea Institute of Science and Technology (KIST) project (Grant No. 2E33831). Author contributions H.L. and J.H.K. (Joohyuk Kang) contributed equally to this work. H.L., J.H.K., and W.L. conceived and designed the project and experiments. H.L. and J.W.K. (Jaewoo Kim) developed the SS-SHP and SS-SHC materials. H.L. and J.H.K. conducted the chemical and mechanical characterizations. H.L. fabricated the wireless pressure sensor. H.L. and J.W.K. performed the human subject experiments. H.L., J.H.K., and W.L. wrote the manuscript, and all authors discussed the results and revised the manuscript. W.L. supervised the overall project. Competing interests The authors declare no competing interests. Received: ((will be filled in by the editorial staff)) Revised: ((will be filled in by the editorial staff)) Published online: ((will be filled in by the editorial staff)) References Wei S et al (2024) Shape-changing electrode array for minimally invasive large-scale intracranial brain activity mapping. Nat Commun 15 Lee W et al (2017) Transparent, conformable, active multielectrode array using organic electrochemical transistors. Proc Natl Acad Sci U S A 114:10554–10559 Lee W et al (2018) Nonthrombogenic, stretchable, active multielectrode array for electroanatomical mapping. Sci Adv 4:2–8 Norton JJS et al (2015) Soft, curved electrode systems capable of integration on the auricle as a persistent brain-computer interface. Proc Natl Acad Sci U S A 112:3920–3925 Park DY et al (2017) Self-Powered Real-Time Arterial Pulse Monitoring Using Ultrathin Epidermal Piezoelectric Sensors. Adv Mater 29:1–9 Kim KY et al (2024) An ultrathin organic–inorganic integrated device for optical biomarker monitoring. Nat Electron 7 Jeong JW et al (2013) Materials and optimized designs for human-machine interfaces via epidermal electronics. Adv Mater 25:6839–6846 Kabiri Ameri S et al (2017) Graphene Electronic Tattoo Sensors. ACS Nano 11:7634–7641 Keum H, Mccormick M, Liu P, Zhang Y, Omenetto FG (2011) Res ARTICLES Epidermal Electron 333:838–844 Peng J (2019) Jeffrey Snyder, G. A figure of merit for flexibility. Sci (1979) 366:690–691 Lu Y et al (2024) Stretchable graphene–hydrogel interfaces for wearable and implantable bioelectronics. Nat Electron 7:51–65 Jiang Z et al (2022) A 1.3-micrometre-thick elastic conductor for seamless on-skin and implantable sensors. Nat Electron 5:784–793 Döhler D et al (2020) Tuning the Self-Healing Response of Poly(dimethylsiloxane)-Based Elastomers. ACS Appl Polym Mater 2:4127–4139 Kim SH et al (2019) An Ultrastretchable and Self-Healable Nanocomposite Conductor Enabled by Autonomously Percolative Electrical Pathways. ACS Nano 13:6531–6539 Kang J et al (2018) Tough and Water-Insensitive Self-Healing Elastomer for Robust Electronic Skin. Adv Mater 30:1–8 Wu X, Wang J, Huang J, Yang S, Robust (2019) Stretchable, and Self-Healable Supramolecular Elastomers Synergistically Cross-Linked by Hydrogen Bonds and Coordination Bonds. ACS Appl Mater Interfaces 11:7387–7396 Yan X et al (2018) Quadruple H-Bonding cross-linked supramolecular polymeric materials as substrates for stretchable, antitearing, and self-healable thin film electrodes. J Am Chem Soc 140:5280–5289 Liu T et al (2023) Extremely strengthening fatigue resistance, elastic restorability and thermodynamic stability of a soft transparent self-healing network based on a dynamic molecular confinement-induced bioinspired nanostructure. Mater Horiz 10:2968–2979 Kim S, Jeon H, Koo JM, Oh DX, Park J (2024) Practical Applications of Self-Healing Polymers Beyond Mechanical and Electrical Recovery. Adv Sci 11:1–22 Yang Y, Urban MW (2018) Self-Healing of Polymers via Supramolecular Chemistry. Adv Mater Interfaces 5:1–19 Ikura R et al (2022) Design of self-healing and self-restoring materials utilizing reversible and movable crosslinks. NPG Asia Mater 14:1–17 Li J et al (2024) Hydrogen-bonded polymeric materials with high mechanical properties and high self-healing capacity. Mater Chem Front 3828–3858. 10.1039/d4qm00472h Xie Z, Hu BL, Li RW, Zhang Q (2021) Hydrogen Bonding in Self-Healing Elastomers. ACS Omega 6:9319–9333 Song K, Il et al (2020) Adaptive self-healing electronic epineurium for chronic bidirectional neural interfaces. Nat Commun 11 Jang TM et al (2024) Stretchable and biodegradable self-healing conductors for multifunctional electronics. Sci Adv 10:1–10 Park H et al (2023) Toughening self-healing elastomer crosslinked by metal–ligand coordination through mixed counter anion dynamics. Nat Commun 14:1–10 Padhan AK et al (2024) Rapid self-healing and superior toughness in ionically crosslinked polymer ionogels and strain sensing applications. J Mater Chem Mater 12:9508–9517 Yao H et al (2023) Water-Insensitive Self-Healing Materials: From Network Structure Design to Advanced Soft Electronics. Adv Funct Mater 33:1–25 Chen L et al (2023) Self-healing polymers through hydrogen-bond cross-linking: synthesis and electronic applications. Mater Horiz 10:4000–4032 Dawelbeit A, Yu M (2021) Transient confinement of the quaternary tetramethylammonium tetrafluoroborate salt in nylon 6,6 fibres: Structural developments for high performance properties. Materials 14 Hu J, Wu Y, Zhang C, Tang BZ, Chen S (2017) Self-adaptive water vapor permeability and its hydrogen bonding switches of bio-inspired polymer thin films. Mater Chem Front 1:2027–2030 Milkin P, Danzer M, Ionov L (2022) Self-Healing and Electrical Properties of Viscoelastic Polymer–Carbon Blends. Macromol Rapid Commun 43:1–12 El Choufi N, Mustapha S, Tehrani B, A., Grady BP (2022) An Overview of Self-Healable Polymers and Recent Advances in the Field. Macromol Rapid Commun 43:1–24 Wu J, Cai LH, Weitz DA (2017) Tough Self-Healing Elastomers by Molecular Enforced Integration of Covalent and Reversible Networks. Adv Mater 29:1702616 Ehrhardt D et al (2020) Self-Healing in Mobility-Restricted Conditions Maintaining Mechanical Robustness: Furan–Maleimide Diels–Alder Cycloadditions in Polymer Networks for Ambient Applications. Polym 2020 12(12):2543 Park H et al (2023) Toughening self-healing elastomer crosslinked by metal–ligand coordination through mixed counter anion dynamics. Nature Communications 2023 14:1 14, 1–10 Liang C et al (2025) Stiff and self-healing hydrogels by polymer entanglements in co-planar nanoconfinement. Nat Mater 24:599–606 Park H et al (2023) Toughening self-healing elastomer crosslinked by metal–ligand coordination through mixed counter anion dynamics. Nat Commun 14:1–10 Jiang Z et al (2020) Self-Healable, and Recyclable Visible-Light-Responsive Hydrogel Actuators. Angew Chem 132:7115–7122Strong Agache PG, Monneur C, Leveque JL, De Rigal J (1980) Original Contributions Mechanical Properties and Young’s Modulus of Human Skin in Vivo. Arch Dermatol Res 269:221–232 Mei JF et al (2016) A Highly Stretchable and Autonomous Self-Healing Polymer Based on Combination of Pt···Pt and π–π Interactions. Macromol Rapid Commun 37:1667–1675 Wang Z et al (2016) High Sensitivity, Wearable, Piezoresistive Pressure Sensors Based on Irregular Microhump Structures and Its Applications in Body Motion Sensing. Small 12, 3827–3836 Matsuhisa N et al (2021) High-frequency and intrinsically stretchable polymer diodes. Nature 600:246–252 Park J et al (2018) Soft, smart contact lenses with integrations of wireless circuits, glucose sensors, and displays. Sci Adv 4:1–11 Adiono T, Fuada S (2017) Investigation of Optical Interference Noise Characteristics in Visible Light Communication System. 126:612–615 Moreira AJC, Valadas RT (1996) & De Oliveira Duarte, A. M. Performance of infrared transmission systems under ambient light interference. IEE Proceedings: Optoelectronics 143, 339–346 Liu C, Kelley SO, Wang Z (2024) Self-Healing Materials for Bioelectronic Devices. Adv Mater 36:1–11 Zhang K et al (2021) Self-healing and stretchable PDMS-based bifunctional sensor enabled by synergistic dynamic interactions. Chem Eng J 412:128734 Ying H, Zhang Y, Cheng J (2014) Dynamic urea bond for the design of reversible and self-healing polymers. Nat Commun 5:1–9 Ronald C, HortonJr., † TM, Herne (1997) *,‡ and & David C. Myles*, †. Aldehyde-Terminated Self-Assembled Monolayers on Gold: Immobilization of Amines onto Gold Surfaces. J Am Chem Soc 119:12980–12981 Matyshak VA et al (2009) Properties of surface compounds in methanol conversion on γ-Al 2O3: Data of in situ IR spectroscopy. Kinet Catal 50:111–121 Shi C, Liu X, Chuai R, Piezoresistive Sensitivity (2009) Linearity and Resistance Time Drift of Polysilicon Nanofilms with Different Deposition Temperatures. Sensors 2009, Vol. 9, Pages 1141–1166 9, 1141–1166 Milkin P, Danzer M, Ionov L (2022) Self-Healing and Electrical Properties of Viscoelastic Polymer–Carbon Blends. Macromol Rapid Commun 43:2200307 Wang Z et al (2016) High Sensitivity, Wearable, Piezoresistive Pressure Sensors Based on Irregular Microhump Structures and Its Applications in Body Motion Sensing. Small 12, 3827–3836 Wang X et al (2014) Silk-Molded Flexible, Ultrasensitive, and Highly Stable Electronic Skin for Monitoring Human Physiological Signals. Adv Mater 26:1336–1342 Khoshdel AR, Carney S, Gillies A (2010) The impact of arm position and pulse pressure on the validation of a wrist-cuff blood pressure measurement device in a high risk population. Int J Gen Med 3:119 Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryVideo1.mp4 Supplementary Video 1 SupplementaryInformation.docx Supplementary_Information Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6919168","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":478613504,"identity":"3f2a04d2-50fe-467f-99c1-d42d76a14d53","order_by":0,"name":"Wonryung Lee","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAwElEQVRIiWNgGAWjYFAC5gYGhooEHigvgRgtjEAtZ4Ba2EjSwtgGVEm0FoPbBxsffJyXJiM/v4HtwweGtHzCWs4lNhvO3JbDY3CMgXnmDIYcywZCWszOMLZJ826r4DFgY2Bm5mGoMCBoC1BL+++/cyp45NuAWv4QqaWNmbEhh4cB6DBmBoYcwlrszzA2S/YcSwP6JbGZsccgjbAWyR7mgx9+1CTbyzcfPszwoyKZsBYkAIpTkjSMglEwCkbBKMAJADdKNLJiDG04AAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0003-0527-023X","institution":"Korea Institute of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Wonryung","middleName":"","lastName":"Lee","suffix":""},{"id":478613505,"identity":"de318131-9698-422b-9209-28eca7271265","order_by":1,"name":"Haechang Lee","email":"","orcid":"","institution":"Korea Institute of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Haechang","middleName":"","lastName":"Lee","suffix":""},{"id":478613506,"identity":"4afc0e5c-489f-41c0-b421-adcb24f92a4f","order_by":2,"name":"Joohyuk Kang","email":"","orcid":"","institution":"Korea Institute of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Joohyuk","middleName":"","lastName":"Kang","suffix":""},{"id":478613507,"identity":"774d7cfe-81bc-4d78-9934-230879e1d79a","order_by":3,"name":"Jaewoo Kim","email":"","orcid":"","institution":"Seoul National University","correspondingAuthor":false,"prefix":"","firstName":"Jaewoo","middleName":"","lastName":"Kim","suffix":""}],"badges":[],"createdAt":"2025-06-18 05:05:33","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6919168/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6919168/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":85848245,"identity":"e36c9855-a371-46c1-96f8-e2f8c9e7cc14","added_by":"auto","created_at":"2025-07-02 09:55:24","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1055229,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCircuit-integrated shape-stable self-healing polymer (SS-SHP) platform a\u003c/strong\u003e, Illustration of a conventional shape-flowable self-healing platform applied to a wireless pressure sensor for wrist pulse monitoring. The device transmits pulse signals via an LED indicator. Due to its linear polymer network connected by hydrogen bonds (H-bonds), the material's viscous nature causes deformation over time, merging the separated electrodes and resulting in an electrical short, turning off the LED. \u003cstrong\u003eb\u003c/strong\u003e, Illustration of the proposed SS-SHP platform with the same device architecture but enhanced material stability. The branched polymer network, reinforced by reversible imine bonds and H-bonds, prevents flow-induced deformation, maintaining stable LED pulse signal transmission. \u003cstrong\u003ec\u003c/strong\u003e, Photograph of the wireless pulse sensor integrated on the shape-stable self-healing platform. Scale bar, 5 mm. \u003cstrong\u003ed\u003c/strong\u003e, Schematic illustration of the wireless pulse sensor. The sensor is constructed on a SS-SHP with patterned self-healing conductive electrodes (SS-SHC) and is folded so that the pressure sensor contacts the pulse area.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-6919168/v1/afd1e96a8bf4bc6beb01bd1e.png"},{"id":85848261,"identity":"f62dfc2b-148f-46b9-9477-71571a472a84","added_by":"auto","created_at":"2025-07-02 09:55:24","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1182822,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eStructural characteristics and shape-stability of conventional SHP and SS-SHPs. a,\u003c/strong\u003e Chemical structure and schematic diagram of the conventional SHP (PDMS-MCI). The polymer consists of linear chains interconnected by H-bonds. Water molecules diffuse into the structure, breaking interchain H-bonds and replacing them with water-polymer H-bonds. \u003cstrong\u003eb\u003c/strong\u003e, Chemical structure and schematic diagram of the SS-SHP (PDMS-MCI-TFB). The polymer features a branched network formed by reversible imine bonds, which prevent water diffusion into the material, maintaining structural stability. \u003cstrong\u003ec\u003c/strong\u003e, FT-IR spectra of PDMS-MCI and PDMS-MCI-TFB before and after PBS immersion (left) and magnified OH peak region (right). Water infiltration increased the OH peak in PDMS-MCI, whereas PDMS-MCI-TFB remained unchanged. \u003cstrong\u003ed\u003c/strong\u003e, Storage modulus of PDMS-MCI and PDMS-MCI-TFB before and after 20 days under ambient conditions (20 °C, 40% relative humidity). PDMS-MCI showed a significant decrease, while PDMS-MCI-TFB retained its modulus with minimal change (\u0026lt; 5%).\u003cstrong\u003e e\u003c/strong\u003e, Side-view images of PDMS-MCI and PDMS-MCI-TFB before and after 20 days under ambient conditions, captured for contact angle measurement. Scale bars, 300 μm. \u003cstrong\u003ef\u003c/strong\u003e, Shape angle variation over time. Stable angles indicate that the shape remains intact, reflecting the material’s resistance to deformation. Values in \u003cstrong\u003ef\u003c/strong\u003erepresent means ± standard deviation (n = 3).\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-6919168/v1/8d4acd3ef446bfdd9e557bc0.png"},{"id":85848247,"identity":"35cebc83-26ad-472f-8501-b581f21e4639","added_by":"auto","created_at":"2025-07-02 09:55:24","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":603601,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMechanical properties and self-healing performance of SS-SHPs (PDMS-MCI-TFB). a\u003c/strong\u003e, Photographs of the SS-SHP (PDMS-MCI\u003csub\u003e0.7\u003c/sub\u003e-TFB\u003csub\u003e0.3\u003c/sub\u003e) sample before (left) and under (right) applying tensile stress using a universal testing machine. The sample withstands a strain of 1032% at a tensile stress of 2 MPa. Scale bars, 5 mm (left); 1 cm (right). \u003cstrong\u003eb\u003c/strong\u003e, Stress–strain curves of SHP samples with varying MCI and TFB molar ratios. \u003cstrong\u003ec\u003c/strong\u003e, Toughness of SHPs as a function of MCI and TFB composition, calculated from the area under the stress–strain curves. Maximum toughness was achieved at an MCI/(MCI+TFB) ratio of 0.3, while a notable decrease occurred when the TFB content exceeded 40%. Values in \u003cstrong\u003ec\u003c/strong\u003e represent means ± standard deviation (n = 5).\u0026nbsp; \u003cstrong\u003ed\u003c/strong\u003e, Photographs showing the mechanical recovery of the SS-SHP after self-healing. The sample was cut and healed under ambient conditions (20 °C, 40% relative humidity) for 24 h. Scale bars, 5 mm (left); 1 cm (right). \u003cstrong\u003ee\u003c/strong\u003e, Stress–strain curves of pristine and self-healed SS-SHP samples after 6, 12, and 24 hr of healing under ambient conditions. After 24 hr, the healed sample reached a strain of 1026% and a tensile stress of 2 MPa, indicating near-complete recovery. \u003cstrong\u003ef\u003c/strong\u003e, Self-healing efficiency of SS-SHPs over time, showing recovery of ~70% stretchability after 6 hr and ~99% after 24 hr under ambient conditions.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-6919168/v1/91c2a388d1dac2129e610341.png"},{"id":85849850,"identity":"dd26603a-7837-48e0-8909-b78e8180695c","added_by":"auto","created_at":"2025-07-02 10:11:24","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":840296,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMechanical properties and self-healing performance of SS-SHPs (PDMS-MCI-TFB). a\u003c/strong\u003e, Photographs of the SS-SHP (PDMS-MCI\u003csub\u003e0.7\u003c/sub\u003e-TFB\u003csub\u003e0.3\u003c/sub\u003e) sample before (left) and under (right) applying tensile stress using a universal testing machine. The sample withstands a strain of 1032% at a tensile stress of 2 MPa. Scale bars, 5 mm (left); 1 cm (right). \u003cstrong\u003eb\u003c/strong\u003e, Stress–strain curves of SHP samples with varying MCI and TFB molar ratios. \u003cstrong\u003ec\u003c/strong\u003e, Toughness of SHPs as a function of MCI and TFB composition, calculated from the area under the stress–strain curves. Maximum toughness was achieved at an MCI/(MCI+TFB) ratio of 0.3, while a notable decrease occurred when the TFB content exceeded 40%. Values in \u003cstrong\u003ec\u003c/strong\u003e represent means ± standard deviation (n = 5).\u0026nbsp; \u003cstrong\u003ed\u003c/strong\u003e, Photographs showing the mechanical recovery of the SS-SHP after self-healing. The sample was cut and healed under ambient conditions (20 °C, 40% relative humidity) for 24 h. Scale bars, 5 mm (left); 1 cm (right). \u003cstrong\u003ee\u003c/strong\u003e, Stress–strain curves of pristine and self-healed SS-SHP samples after 6, 12, and 24 hr of healing under ambient conditions. After 24 hr, the healed sample reached a strain of 1026% and a tensile stress of 2 MPa, indicating near-complete recovery. \u003cstrong\u003ef\u003c/strong\u003e, Self-healing efficiency of SS-SHPs over time, showing recovery of ~70% stretchability after 6 hr and ~99% after 24 hr under ambient conditions.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-6919168/v1/211b8cb114280bec8753fa04.png"},{"id":85848272,"identity":"59077b63-e152-4221-9fee-eedcabf673ba","added_by":"auto","created_at":"2025-07-02 09:55:24","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":2762620,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eElectrical and mechanical performance of shape-stable self-healing conductor (SS-SHC). a\u003c/strong\u003e, Schematic illustration of SS-SHC. The SS-SHC was fabricated by embedding Ag flakes (AgFs) into the SS-SHP matrix. \u003cstrong\u003eb\u003c/strong\u003e, Stress–strain curves of pristine and self-healed SS-SHC samples after 24 hr and 48 hr of healing under ambient conditions (20 °C, 40% relative humidity). \u003cstrong\u003ec\u003c/strong\u003e,\u003cstrong\u003e \u003c/strong\u003eResistance–strain curves of pristine and self-healed (24 hr and 48 hr) SS-SHC samples. \u003cstrong\u003ed\u003c/strong\u003e, Photographs showing an infrared LED (IR LED) connected with SS-SHC used as both anode and cathode. The restoration of IR LED operation after healing confirms recovery of electrical connectivity. Scale bars, 1 mm. \u003cstrong\u003ee\u003c/strong\u003e, SEM images of the SS-SHC surface after cutting and after 24 hr. The cut interface was visibly restored after healing. Scale bars, 50 μm. \u003cstrong\u003ef\u003c/strong\u003e, Recovery of current through the IR LED over time. No current was detected immediately after cutting, but ~60% of the original current was recovered after 10 s and ~94% after 24 hr. \u003cstrong\u003eg\u003c/strong\u003e, Illustration showing a tilted cross-sectional view of a 2-week-aged SHC. \u003cstrong\u003eh\u003c/strong\u003e, SEM cross-sectional images of 2-week-aged SS-SHC and conventional SHC. The SS-SHC maintained a uniform distribution of AgFs, whereas in the conventional SHC, AgFs gradually settled downward over time. Scale bars, 10 μm. \u003cstrong\u003ei\u003c/strong\u003e, Surface resistance of SS-SHC and conventional SHC measured over 14 days under ambient conditions. Inset: Illustration of the measurements.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-6919168/v1/332f0b113aa74cf0d567c6ac.png"},{"id":85848716,"identity":"639c1631-fdcc-44a9-9c33-acf80f494f48","added_by":"auto","created_at":"2025-07-02 10:03:24","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":868878,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSkin conformability and wireless pulse monitoring using SS-SHP-based pressure sensors. a\u003c/strong\u003e, Illustrations of wrist-mounted pressure sensors based on SS-SHP and PDMS. The SS-SHP-based sensor forms a seamless skin interface for efficient pulse pressure transfer, whereas the PDMS-based sensor shows poor conformability, causing interfacial gaps and signal loss. \u003cstrong\u003eb\u003c/strong\u003e, Pulse signals measured from the wrist using SS-SHP and PDMS-based piezoresistive sensors. The SS-SHP sensor enabled stable and clear pulse detection, whereas the PDMS sensor failed to capture reliable signals due to poor skin contact. Inset: Illustration of the sensors. \u003cstrong\u003ec\u003c/strong\u003e, Pulse signal graphs comparing a healthy individual and a pregnant woman, recorded using the SS-SHP-based pressure sensor. The healthy subject showed regular pulse intervals, whereas the pregnant subject displayed irregular pulse patterns. \u003cstrong\u003ed\u003c/strong\u003e, Photograph of a fully integrated wireless pulse sensor mounted on the skin. The system features a skin-conformal, self-healing platform for real-time physiological signal monitoring. Scale bar, 5 mm. \u003cstrong\u003ee\u003c/strong\u003e, Schematic illustration of the wireless pulse sensor. The system consists of an SS-SHP substrate, patterned SS-SHC electrodes, a pressure-sensing layer made of imprinted PDMS coated with PEDOT:PSS, a receiving coil for wireless power transfer via inductive coupling, and an IR LED for optical signal transmission. \u003cstrong\u003ef\u003c/strong\u003e,\u003cstrong\u003e \u003c/strong\u003eCircuit schematic of the wireless pressure sensor system. \u003cstrong\u003eg\u003c/strong\u003e, Photograph of pulse detection using the wireless sensor. Brightness fluctuations of the IR LED, captured by an IR camera, are used to monitor pulse pressure changes. Scale bar, 1 cm. \u003cstrong\u003eh\u003c/strong\u003e, Correlation between applied pressure, resistance, and IR LED gray value. The gray value, extracted from IR camera images, increased with LED brightness, which is modulated by pressure-induced resistance changes. \u003cstrong\u003ei\u003c/strong\u003e, Real-time pulse signal recorded wirelessly via changes in IR LED brightness (gray value), demonstrating successful optical transmission of physiological signals.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-6919168/v1/7b5215c2a1b8b14fca5c3625.png"},{"id":85852168,"identity":"50ff3c0e-52f3-4b72-b026-6d8fd77b3592","added_by":"auto","created_at":"2025-07-02 10:27:27","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":8436253,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6919168/v1/72a2e757-f0ba-4371-aa38-0b5182f90f6f.pdf"},{"id":85848269,"identity":"b6c1b643-fcdc-445f-9ad1-fe1b3254646d","added_by":"auto","created_at":"2025-07-02 09:55:24","extension":"mp4","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":457544,"visible":true,"origin":"","legend":"Supplementary Video 1","description":"","filename":"SupplementaryVideo1.mp4","url":"https://assets-eu.researchsquare.com/files/rs-6919168/v1/bdbb03bfdae86d19d7c70357.mp4"},{"id":85850777,"identity":"7bc4bc49-1b4e-472a-95d9-3c9b80f70743","added_by":"auto","created_at":"2025-07-02 10:19:24","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":5002826,"visible":true,"origin":"","legend":"Supplementary_Information","description":"","filename":"SupplementaryInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-6919168/v1/e69acc0c641977861ecc4e2c.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"A Conformable Shape-Stable Self-Healing Polymer Platform for Continuous Wireless Arterial Pulse Monitoring","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eConformal electronics represent a significant advancement in wearable and flexible technology, enabling the seamless integration of electronic functions with the human body. Their high adaptability to complex biological surfaces is essential for next-generation applications that record physiological signals, such as electrocorticogram\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e, electrocardiogram\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e, electroencephalogram\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e, and arterial pulse\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. Close conformal contact between electronics and biological tissue minimizes motion artifacts\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e, thereby reducing contact impedance and improving the signal-to-noise ratio. These improvements enhance the accuracy and reliability of physiological signal acquisition\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eTraditionally, device conformability has been improved by reducing material thickness, engineering structural design, or employing materials with a low Young\u0026rsquo;s modulus\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. For example, a 1.3 \u0026micro;m thick polydimethylsiloxane (PDMS)-based conductor was used to fabricate a cuff-type ultrathin neural electrode, which exhibited lower noise levels compared to thicker electrodes during neural signal recording\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. A combinatorial strategy has been proposed to integrate ultra-thin substrates with structural design or soft materials. For instance, a 2.6 \u0026micro;m-thick multielectrode array combined with a mesh structure enabled motion artifact-free electroanatomical mapping on the dynamically moving surface of a rat\u0026rsquo;s heart\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. Moreover, a 7 \u0026micro;m-thick hydrogel with a low Young\u0026rsquo;s modulus of 12.9 kPa was used to fabricate a biocompatible cardiac patch capable of long-term physiological monitoring\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eRecently, self-healing polymers (SHPs) have emerged as promising materials for conformal bioelectronics, due to their ability to dynamically reconstruct their soft polymer networks to adapt to contact surfaces. The high conformability of SHPs is attributed to their linear molecular structure and dynamic supramolecular networks, which induce a low Young\u0026rsquo;s modulus and high flowability\u003csup\u003e\u003cspan additionalcitationids=\"CR14 CR15 CR16 CR17\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e, thereby enabling efficient adaptation to irregular topographies\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. Unlike highly crosslinked polymers, where covalent bonds restrict molecular flexibility, SHPs rely on dynamic hydrogen bonds (H-bonds)\u003csup\u003e\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. These reversible, non-covalent interactions enable rapid polymer chain rearrangement, allowing SHP-based devices to conform instantly to dynamically changing biological surfaces. For example, to minimize mechanical mismatch at the tissue-device interface, a cuff-type neural interface was developed using SHPs, whose intrinsic self-healing and adaptive properties allowed conformal, suture-free integration with peripheral nerves\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. Furthermore, a self-healing electronic device designed for the urinary bladder was developed to conform to dynamically expanding tissue, enabling continuous physiological monitoring and electrical stimulation\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eHowever, applying SHPs to electronic devices remains challenging due to the inherent trade-off between shape-adaptability and shape-stability\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e,\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. While their flowable nature enables intimate contact with irregular biological surfaces, it also leads to time-dependent deformation that compromises shape-stability. In particular, linear structures of SHPs exhibit high water vapor permeability, enabling water molecules to infiltrate the polymer network, break H-bonds between polymer chains, and form new H-bonds with the infiltrated water\u003csup\u003e\u003cspan additionalcitationids=\"CR29 CR30\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. This progressive bond disruption gradually weakens the shape-stability of the SHPs over time, accelerates structural collapse, and ultimately leads to electrical short circuits, impairing the reliable operation of SHP-integrated circuits\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e,\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. Various studies have attempted to reduce flowable behavior of SHPs to improve mechanical robustness\u003csup\u003e\u003cspan additionalcitationids=\"CR35\" citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e; however, such approaches often lead to an increase in Young\u0026rsquo;s modulus to the range of 3\u0026ndash;50 MPa\u003csup\u003e\u003cspan additionalcitationids=\"CR38\" citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e, which compromises their conformal integration with biological tissues such as skin (~\u0026thinsp;600 kPa\u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e). Moreover, excessive suppression of viscous flow adversely affects self-healing time and stretchability\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e,\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. Thus, the intrinsic trade-off makes it difficult to design SHPs that maintain high shape-adaptability while suppressing flowable nature, thereby limiting their integration into robust and long-term functional electronic systems.\u003c/p\u003e \u003cp\u003eIn this work, we developed a shape-stable self-healing polymer platform (SS-SHP) that combines long-term shape retention with skin-like mechanical softness, enabling its use in conformal, circuit-integrated wearable electronics. The SS-SHP features a branched polymer network constructed through reversible imine bonds and H-bonds, which effectively suppress water diffusion into the matrix and enhance resistance to shape deformation. The SS-SHP preserved its original shape without dimensional change, and its storage modulus decreased by less than 5%, confirming long-term structural and mechanical stability over a 20-day period. Notably, the SS-SHP exhibited a mechanically stable structure with a low Young\u0026rsquo;s modulus of 576 kPa, comparable to that of human skin (~\u0026thinsp;600 kPa)\u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e, enabling high conformability to microscale wrinkles on the fingertip. Beyond serving as a substrate, the SS-SHP was also utilized as a polymer matrix for conductive electrodes by incorporating Ag flakes. Unlike conventional SHP-based conductors, which showed conductivity degradation due to sedimentation of Ag flakes, the SS-SHP-based conductors exhibited time-independent resistance over 2 weeks. To demonstrate the practical utility of the SS-SHP platform, we fabricated a wireless arterial pressure monitoring system designed to minimize the use of rigid components and preserve the intrinsic conformability of the SS-SHP. Instead of integrating bulky electronic chips, a single infrared light-emitting diode (IR LED) was employed for wireless optical signal transmission\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. The resulting device conformed intimately to the curved surface of the wrist, enabling accurate arterial pulse detection without external contact pressure and successfully distinguishing pulse waveforms between healthy individuals and pregnant women\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. Notably, dynamic pressure fluctuations generated by arterial pulses were converted into real-time optical signals through modulation of IR LED brightness, enabling continuous monitoring of physiological signals using a skin-conformal wireless sensing system.\u003c/p\u003e"},{"header":"2. Results and discussion","content":"\u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea, b schematically illustrates the differences between a conventional shape-flowable self-healing platform and a newly developed shape-stable self-healing platform. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea shows the conventional self-healing polymer (SHP), which consists of linear polymer chains interconnected solely through hydrogen bonds (H-bonds)\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. These weak intermolecular interactions result in a highly dynamic and flowable material that can adapt to irregular surfaces. However, this flowable behavior poses significant challenges in constructing integrated circuits\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e, as continuous deformation can distort electrode geometry, increasing the risk of electrical short circuits and ultimately compromising the reliable operation of electronics.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe shape-stable self-healing polymer (SS-SHP) developed in this study, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb, features a branched molecular architecture reinforced by a dual-network structure of reversible covalent imine bonds and H-bonds. This architecture significantly enhances mechanical robustness, suppressing undesirable deformation while preserving self-healing capabilities. The dual-network design not only prevents structural collapse but also ensures long-term shape-stability, enabling reliable mechanical performance and seamless integration into electronic systems. As a result, the SS-SHP provides a mechanically stable platform for self-healing electronic devices, preserving electrode geometry and preventing electrical short circuits and performance degradation.\u003c/p\u003e \u003cp\u003eThe shape-stability of the SS-SHP facilitated the construction of an integrated circuit for wireless pulse pressure monitoring. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec, a fully assembled device was conformally mounted on the wrist, consisting of a wireless power receiver, a pressure sensor for pulse detection, and an optical data transmission component. Each component was seamlessly integrated to form a compact, skin-conformal platform. The corresponding schematic illustration in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed details the materials and functional components of the system. The substrate was composed of the SS-SHP, while the electrodes were made of a shape-stable self-healing conductor (SS-SHC) incorporating Ag flakes (AgFs) within the same SS-SHP matrix. The pressure sensing unit consisted of a piezoresistive sensor fabricated by coating poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) onto sandpaper-imprinted PDMS\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e, enabling the detection of subtle pressure changes induced by arterial pulsation. The wireless circuitry included inductive coupling for power transmission\u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e,\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e and optical signal transmission via an infrared light-emitting diode (IR LED), which operates in a wavelength range minimally affected by ambient visible light, thus reducing optical noise and enabling stable signal readout under various lighting conditions\u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e,\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e. The entire system demonstrated high skin conformability, emphasizing the potential of the SS-SHP-based platform for robust and wearable self-healing bioelectronic applications.\u003c/p\u003e \u003cp\u003eTo facilitate a comparison based on molecular architecture, the conventional SHP used in this study was designed as a PDMS-based linear elastomer, which is widely employed in skin-interfaced biomedical devices due to its biocompatibility and flexibility\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e,\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea and \u003cb\u003eSupplementary Fig.\u0026nbsp;1a\u003c/b\u003e, this material was synthesized by reacting bis(3-aminopropyl)-terminated PDMS (H\u003csub\u003e2\u003c/sub\u003eN-PDMS-NH\u003csub\u003e2\u003c/sub\u003e) with 4,4'-Methylenebis(cyclohexyl isocyanate) (MCI) to form linear PDMS-MCI chains. The formation of urea groups from this reaction was confirmed by a new Fourier-transform infrared (FT-IR) absorption peak at 1630 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, corresponding to C\u0026thinsp;=\u0026thinsp;O stretching (\u003cb\u003eSupplementary Fig.\u0026nbsp;1b\u003c/b\u003e). The resulting elastomer is crosslinked via urea bonds\u003csup\u003e\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e, which form H-bonds serving as dynamic self-healing sites. However, the linear structure of the conventional SHP exhibits high water permeability, allowing water molecules to diffuse into the polymer network. This diffusion breaks existing interchain H-bonds, leading to the formation of water-polymer H-bonds instead. This progressive bond disruption weakens intermolecular interactions, thereby degrading the polymer network, ultimately leading to mechanical instability over time.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo suppress progressive shape deformation, we developed the SS-SHP featuring a branched architecture, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb. In this design, the linear PDMS-MCI chains are covalently linked via reversible imine bonds formed through a Schiff base reaction with 1,3,5-triformylbenzene (TFB), a trifunctional aldehyde (\u003cb\u003eSupplementary Fig.\u0026nbsp;1a\u003c/b\u003e). The reaction between the \u0026ndash;NH\u003csub\u003e2\u003c/sub\u003e groups of PDMS-MCI and the \u0026ndash;CHO groups of TFB results in C\u0026thinsp;=\u0026thinsp;N imine bonds, confirmed by a new FT-IR peak at 1645 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (\u003cb\u003eSupplementary Fig.\u0026nbsp;1b\u003c/b\u003e). Each TFB molecule connects with up to three PDMS-MCI chains, yielding a branched polymer network. Within the SS-SHP, both H-bonds and imine bonds function as self-healing sites. Unlike the linear molecular system, however, the branched structure significantly restricts water diffusion, effectively preventing moisture-induced degradation. This architecture confers enhanced mechanical robustness and long-term shape-stability, addressing the limitations of conventional H-bonded linear SHPs.\u003c/p\u003e \u003cp\u003eTo compare the water permeability of the conventional SHP (PDMS-MCI) and the SS-SHP (PDMS-MCI-TFB), FT-IR spectroscopy was performed on both materials before and after immersion in phosphate-buffered saline (PBS) for 1 day (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec). After immersion, the samples were dried under ambient conditions (defined throughout this study as 20\u0026deg;C and 40% relative humidity) for 10 hr to remove surface moisture while retaining absorbed water within the polymer networks. The FT-IR spectra revealed changes in the hydroxyl (\u0026ndash;OH) stretching vibration band near 3330 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which serves as a key indicator of water absorption. As shown in the magnified graphs of Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec, the conventional SHP exhibited a pronounced increase in the \u0026ndash;OH peak intensity following PBS immersion, while the SS-SHP showed minimal change. This result suggests that the conventional SHP absorbs significantly more water due to its high moisture permeability and low network integrity\u003csup\u003e\u003cspan additionalcitationids=\"CR29\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e, which can lead to gradual deformation over time. In contrast, the branched-chain architecture of the SS-SHP effectively limits water diffusion into the network, thereby enhancing water resistance and preserving long-term shape retention.\u003c/p\u003e \u003cp\u003eTo assess the long-term shape-stability of the materials, we first measured the storage modulus, which indicates the elastic stiffness of a material and its ability to resist shape deformation under stress. A time-independent storage modulus is indicative of superior shape-stability. Samples were stored for 20 days under ambient conditions and analyzed using a rheometer (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed). The SS-SHP exhibited a moderate decrease in storage modulus from 3 \u0026times; 10\u003csup\u003e4\u003c/sup\u003e Pa to 5 \u0026times; 10\u003csup\u003e3\u003c/sup\u003e Pa, while the conventional SHP showed a sharp drop from 10\u003csup\u003e5\u003c/sup\u003e Pa to 10\u003csup\u003e3\u003c/sup\u003e Pa after 20 days. This result indicates that the SS-SHP maintains its structural form more effectively under prolonged environmental exposure. To further evaluate the shape retention against structural collapse at the macroscopic level, we assessed the deformation of the SS-SHP and the conventional SHP samples over time by measuring the shape angle formed between the sample and a flat glass substrate. Samples (~\u0026thinsp;300 \u0026micro;m thick) were placed on a glass surface and stored under ambient conditions for 20 days (\u003cb\u003eSupplementary Fig.\u0026nbsp;2\u003c/b\u003e). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee, side-view photographs revealed that the SS-SHP maintained an upright shape with a shape angle near 90\u0026deg;, whereas the conventional SHP exhibited significant collapse. Quantitative analysis of shape angle over 20 days showed a gradual decline from 90\u0026deg; to 58\u0026deg; in the conventional SHP (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef), whereas the SS-SHP maintained a stable angle of 90\u0026deg; throughout the period. Together, these results demonstrate that the branched network of the SS-SHP, incorporating imine bonds derived from TFB and H-bonds introduced by MCI, significantly enhances long-term shape-stability compared to the conventional linear SHPs.\u003c/p\u003e \u003cp\u003eTo characterize the robustness of the SS-SHP, mechanical tensile tests were performed. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea presents photographs of the optimized SS-SHP (PDMS-MCI\u003csub\u003e0.7\u003c/sub\u003e-TFB\u003csub\u003e0.3\u003c/sub\u003e) being stretched to over 1000% strain without mechanical failure, visually highlighting its exceptional stretchability. The mechanical properties of the SS-SHPs could be tuned by varying the molar ratio of MCI to TFB. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb shows the stress-strain curves for PDMS-MCI\u003csub\u003ex\u003c/sub\u003e-TFB\u003csub\u003e1\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e compositions, while the corresponding toughness values calculated from the area under each curve are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec. Among the tested formulations, PDMS-MCI\u003csub\u003e0.7\u003c/sub\u003e-TFB\u003csub\u003e0.3\u003c/sub\u003e exhibited the highest ultimate tensile strength (\u0026gt;\u0026thinsp;2 MPa at 1000% strain) and toughness (9.75 MJ/m\u003csup\u003e3\u003c/sup\u003e), making it the most mechanically robust composition. This enhanced mechanical performance is attributed to the incorporation of TFB, a trifunctional aldehyde that promotes the formation of a branched network via reversible imine bonding. Notably, the mechanical properties exhibit a strong dependence on the TFB content. When the amount of TFB exceeded the optimized ratio, excess TFB led to an increased number of unreacted aldehyde groups due to the limited availability of amine groups in PDMS, thereby reducing the effective crosslinking density and diminishing mechanical strength. This was confirmed by FT-IR analysis, which revealed a stronger C\u0026ndash;H stretching vibration peak (2824 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003csup\u003e50,51\u003c/sup\u003e of the aldehyde groups in PDMS-MCI\u003csub\u003e0.6\u003c/sub\u003e-TFB\u003csub\u003e0.4\u003c/sub\u003e and PDMS-MCI\u003csub\u003e0.5\u003c/sub\u003e-TFB\u003csub\u003e0.5\u003c/sub\u003e compared to samples with lower TFB content (\u003cb\u003eSupplementary Fig.\u0026nbsp;3\u003c/b\u003e), indicating a higher concentration of unreacted aldehydes. Based on its superior toughness and optimized crosslinking, PDMS-MCI\u003csub\u003e0.7\u003c/sub\u003e-TFB\u003csub\u003e0.3\u003c/sub\u003e was selected for all subsequent experiments. To evaluate durability under cyclic mechanical loading, the optimized SS-SHP was subjected to 100 cycles of 100% stretching (\u003cb\u003eSupplementary Fig.\u0026nbsp;4\u003c/b\u003e). The material retained its mechanical resilience without noticeable performance degradation, confirming its suitability for long-term use in stretchable electronic applications.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe self-healing capability of PDMS-MCI\u003csub\u003e0.7\u003c/sub\u003e-TFB\u003csub\u003e0.3\u003c/sub\u003e was assessed through tensile recovery experiments. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed, the sample was cut and left to self-heal under ambient conditions for 24 hr. After healing, the sample recovered an ultimate tensile strength of 1.78 MPa and a stretchability of 1026%, compared to pristine values of 2.05 MPa and 1032%, respectively. To quantify healing efficiency over time, stress-strain curves were obtained after 6, 12, and 24 hr of healing (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee), and the recovery ratios in tensile strength and stretchability were calculated (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef). After 24 hr, the sample recovered 86.8% of its original tensile strength and 99.4% of its stretchability, demonstrating efficient self-healing performance enabled by dynamic imine and H-bond interactions.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea compares the conformability of the SS-SHP and PDMS (Sylgard 184, base:curing agent\u0026thinsp;=\u0026thinsp;10:1, Dow Corning), both fabricated with a similar thickness of approximately 50 \u0026micro;m, when placed on a human fingertip. The SS-SHP (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, left) conforms closely to the skin wrinkles, demonstrating superior surface adaptability, whereas the PDMS (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, right) fails to follow the curved skin features, resulting in visible interfacial gaps. This difference arises from the mechanical properties of the materials: the SS-SHP exhibits a much lower Young\u0026rsquo;s modulus (~\u0026thinsp;576 kPa) compared to PDMS (~\u0026thinsp;1.47 MPa), enabling it to deform more easily and adhere intimately to soft, curved skin surface (\u003cb\u003eSupplementary Fig.\u0026nbsp;5\u003c/b\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo quantitatively compare surface adaptation performance, a skin replica mimicking the wrinkled texture of a fingertip was fabricated (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb, left), and both materials were placed on its surface (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb, middle and right; \u003cb\u003eSupplementary Fig.\u0026nbsp;6\u003c/b\u003e). The SS-SHP adhered tightly to the replica, reproducing fine wrinkle patterns, while PDMS floated above the surface without capturing the contour features. Quantitative analysis of surface adaptation was performed using a 3D measuring laser microscope. The surface profiles at the material-replica interface were extracted (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec), and the total contour length (\u003cem\u003eL\u003c/em\u003e) of each material was calculated. This value was then normalized against the contour length of the skin replica (\u003cem\u003eL\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e) to determine conformability (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed). The SS-SHP exhibited a normalized contour length of 90%, indicating excellent surface adaptation. The conventional SHP showed a comparable value with only a 2% difference, while PDMS exhibited a significantly lower normalized length of 42%, reflecting its limited ability to adapt to the replica\u0026rsquo;s micro-texture. These results demonstrate that the SS-SHP offers significantly enhanced conformability compared to PDMS, making it a more suitable substrate for skin-interfaced devices.\u003c/p\u003e \u003cp\u003eTo implement functional circuits on the self-healing platform, a shape-stable self-healing conductor (SS-SHC) was developed by embedding AgFs into the SS-SHP matrix (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea and \u003cb\u003eSupplementary Fig.\u0026nbsp;7\u003c/b\u003e), ensuring consistent material properties and cohesive integration. To evaluate its mechanical durability and self-healing performance, stress-strain behavior was examined through tensile testing (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). Dog-bone-shaped samples were fabricated by screen-printing SS-SHC ink onto the SS-SHP substrate using a polyimide (PI) mask with a dog-bone-shaped opening \u003cb\u003e(Supplementary Fig.\u0026nbsp;8a\u003c/b\u003e). The printed SS-SHC samples were then cut and allowed to self-heal under ambient conditions. After 24 hr, the self-healed SS-SHC exhibited a tensile strength of 1.3 MPa at 900% strain. Compared to the pristine sample (1.76 MPa at 980% strain), the fracture strain was restored to 91.8% and the tensile strength to 78.7%, demonstrating the material\u0026rsquo;s excellent mechanical self-healing performance. During the tensile test, electrical resistance was measured to assess the recovery of electrical properties after self-healing (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec). The samples maintained electrical conductivity under strains up to ~\u0026thinsp;700%, and the resistance increased by only 11% after 24 hr of healing and recovered to within 0.2% of the original value after 48 hr, confirming the effective re-establishment of conductive pathways.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo evaluate the recovery of electrical performance after damage, an IR LED was integrated into the SS-SHC electrode and operated under a constant 1 V (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed and \u003cb\u003eSupplementary Fig.\u0026nbsp;8b\u003c/b\u003e). In the pristine state, the IR LED remained turned on, indicating continuous electrical conduction. When the SS-SHC electrode connected to the anode side of the IR LED was cut, the conductive path was interrupted, and the IR LED immediately turned off. After 24 hr of self-healing under ambient conditions, the IR LED turned on again, demonstrating successful restoration of electrical connectivity. This recovery behavior was further confirmed by scanning electron microscopy (SEM) imaging of the cut region before and after healing (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee). After cutting, a distinct rupture was observed with separated AgFs, indicating disruption of the conductive network. After 24 hr, the AgFs were redistributed and reconnected across the previously cut region, re-establishing a continuous conductive pathway. The time-dependent electrical recovery was quantified by monitoring the current through the IR LED (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef). Approximately 60% of the original current was restored within 10 s (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef, inset), and 94% was recovered after 24 hr, confirming the rapid and efficient electrical self-healing capability of the SS-SHC.\u003c/p\u003e \u003cp\u003eTo compare the effect of matrix structure on the dispersion stability of AgFs, conventional SHP and SS-SHP were each used to fabricate composite conductors (conventional SHC and SS-SHC) by incorporating AgFs under identical weight ratios. Tilted cross-sectional SEM images were analyzed after 2 weeks of aging to observe both surface and subsurface changes in the distribution of AgFs (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eg). Initially, both SHCs exhibited uniform dispersion of AgFs throughout the matrix (\u003cb\u003eSupplementary Fig.\u0026nbsp;9\u003c/b\u003e). However, after 2 weeks, distinct differences emerged: in the conventional SHC, AgFs gradually sank toward the bottom, indicating sedimentation due to the flowable nature of the linear SHP (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eh, bottom). In contrast, the SS-SHC maintained a consistent distribution of AgFs, demonstrating that its shape-stable matrix effectively prevents long-term morphological changes (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eh, top). This dispersion stability of AgFs is directly linked to the electrical reliability of the conductor. In practical electronic systems, resistance drift over time can lead to signal distortion, reduced sensor sensitivity, or circuit malfunction\u003csup\u003e\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e\u003c/sup\u003e. To assess this, the surface resistances of both SHCs were measured daily over 2 weeks (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ei). The SS-SHC exhibited excellent stability, with only a 3% increase (\u003cem\u003eR\u003c/em\u003e/\u003cem\u003eR\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;1.03), whereas the conventional SHC showed severe degradation\u003csup\u003e\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e\u003c/sup\u003e, with resistance rising to \u003cem\u003eR\u003c/em\u003e/\u003cem\u003eR\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;7.7. These results confirm that the SS-SHP matrix effectively suppresses sedimentation of AgFs, preserving conductive pathways and ensuring long-term electrical performance, making the SS-SHC suited for use in integrated, durable soft electronics.\u003c/p\u003e \u003cp\u003eTo demonstrate the practical application of the SS-SHP platform in wearable sensing systems, a piezoresistive pressure sensor was fabricated by integrating the SS-SHC as the electrode on the SS-SHP substrate. The pressure-sensing layer was formed by coating PEDOT:PSS onto a sandpaper-imprinted PDMS surface (\u003cb\u003eSupplementary Fig.\u0026nbsp;10\u003c/b\u003e). For comparison, a control sensor using PDMS substrate was also fabricated. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea, the SS-SHP-based sensor conformed intimately to the curved surface of the wrist, ensuring tight contact and effective transmission of arterial pulse pressure to the sensor. In contrast, the PDMS-based sensor exhibited poor conformal contact with the skin, resulting in interfacial gaps that reduced pulse signal transmission efficiency. To evaluate sensing performance, wrist pulse signals were recorded without applying external pressure. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb, the SS-SHP-based sensor successfully detected regular pulse patterns, whereas the PDMS-based sensor failed to capture any discernible signal due to poor contact. The PDMS sensor required an external pressure of 20 kPa to enable pulse detection, indicating that adequate conformal contact is a prerequisite for accurate signal measurement (\u003cb\u003eSupplementary Fig.\u0026nbsp;11\u003c/b\u003e). Furthermore, the SS-SHP-based pressure sensor was used to differentiate between physiological pulse patterns of a healthy individual and a pregnant woman (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec). The healthy subject displayed a stable and periodic pulse waveform, while the pregnant subject exhibited irregular and fluctuating signals, consistent with prior studies indicating altered cardiovascular dynamics during pregnancy\u003csup\u003e\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e,\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo evaluate the wearable applicability of the highly conformable pressure sensor, a wireless pulse pressure sensor was fabricated by integrating all functional components\u0026mdash;including the pressure sensor, wireless power receiver, and optical transmitter\u0026mdash;onto the SS-SHP substrate (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed). The device incorporated SS-SHC electrodes, a pressure-sensing layer composed of imprinted PDMS coated with PEDOT:PSS, and an IR LED for optical signal transmission (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ee). The IR LED was selected to enable real-time wireless data communication with a single component, thereby avoiding bulky or rigid circuit elements and preserving the overall conformability of the device. The corresponding circuit diagram is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ef; the system was wirelessly activated via inductive coupling using an alternating current (AC) power source operating in the MHz frequency range. The overall fabrication process is detailed in \u003cb\u003eSupplementary Fig.\u0026nbsp;12\u003c/b\u003e. After fabrication, the device was folded to ensure direct contact between the pressure-sensing region and the wrist.\u003c/p\u003e \u003cp\u003eTo operate the system, an external transmitting coil was placed above the device for wireless power delivery, and real-time changes in IR LED brightness\u0026mdash;modulated by pulse-induced resistance variation\u0026mdash;were captured using an IR camera (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eg). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eh, the pressure-induced resistance changes modulated the current through the IR LED, resulting in brightness variations that were quantified by extracting gray values from IR camera images. The sensor demonstrated a high sensitivity of approximately 0.075 kPa⁻\u0026sup1; (Δ(\u003cem\u003eR\u003c/em\u003e/\u003cem\u003eR\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e)/Δ\u003cem\u003eP\u003c/em\u003e) under 15 kPa, which corresponds to the typical range of pulse pressure at the wrist\u003csup\u003e\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e\u003c/sup\u003e. This confirms its suitability for detecting subtle physiological pressure variations during pulse monitoring. \u003cb\u003eSupplementary Fig.\u0026nbsp;13\u003c/b\u003e validates the visual emission stability of the IR LED under AC power. When the IR LED was powered using AC signals from 1 Hz to 1 MHz, the IR camera captured alternating brightness at low frequencies (\u0026lt;\u0026thinsp;10\u003csup\u003e2\u003c/sup\u003e Hz). However, at higher frequencies (\u0026gt;\u0026thinsp;10\u003csup\u003e3\u003c/sup\u003e Hz), the frame-to-frame brightness appeared visually constant due to temporal averaging by the camera, resulting in stable output similar to that of direct current (DC) operation. This is because the frequency of the wireless power signal exceeds the shutter speed of the IR camera (196 frames/s), making the LED flickering imperceptible and enabling continuous brightness capture. Optically acquired pulse waveforms are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ei, showing clear brightness fluctuations that correspond to systolic and diastolic phases; higher brightness during low resistance (systole) and lower brightness during high resistance (diastole). The full video of this measurement is provided in \u003cb\u003eSupplementary Video 1\u003c/b\u003e, where real-time fluctuating pulse signals can be visually observed via IR LED flickering. Additionally, \u003cb\u003eSupplementary Fig.\u0026nbsp;14\u003c/b\u003e compares the pulse signals acquired optically (gray value) with those obtained from electrical measurements (resistance), showing strong correlation between the two methods, as the optically observed P\u003csub\u003e1\u003c/sub\u003e and P\u003csub\u003e2\u003c/sub\u003e peaks closely matched those from electrical signals. These results confirm the reliability of the optical readout and highlights the system\u0026rsquo;s potential for continuous, non-invasive cardiovascular monitoring.\u003c/p\u003e"},{"header":"3. Conclusion","content":"\u003cp\u003eIn this study, we established a highly stable and skin-conformal materials platform for self-healing electronics by developing a shape-stable self-healing polymer (SS-SHP) and integrating it into a wireless pulse pressure sensing system. This platform overcomes major limitations of conventional self-healing electronics by: (1) improving shape retention through a dual-network polymer design comprising reversible imine and hydrogen bonds, (2) enabling the fabrication of a shape-stable self-healing conductor (SS-SHC) with long-term electrical reliability, and (3) demonstrating a fully integrated, wireless, and conformable sensor capable of real-time and continuous monitoring of dynamic physiological signals. The SS-SHP maintained its original shape over 20 days under ambient conditions, while the SS-SHC exhibited time-independent electrical resistance by suppressing the sedimentation of Ag flakes, unlike conventional SHC. The wireless device incorporated a pressure sensor, inductive power receiver, and IR LED-based optical transmitter, all integrated into the SS-SHP substrate. This configuration enabled the detection of arterial pulse signals without external pressure and distinguished physiological differences between healthy and pregnant individuals. Moreover, real-time monitoring of pulse waveforms was successfully achieved via optical signal transmission, enabling wireless and continuous physiological sensing. The platform\u0026rsquo;s mechanical stability, electrical reliability, and wireless integration offer a promising foundation for next-generation soft bioelectronic systems designed for long-term health monitoring and therapeutic applications.\u003c/p\u003e"},{"header":"4. Experimental Section","content":"\u003cp\u003e \u003cb\u003eMaterials\u003c/b\u003e: Aminopropyl-terminated polydimethylsiloxane (NH\u003csub\u003e2\u003c/sub\u003e-PDMS-NH\u003csub\u003e2\u003c/sub\u003e, DMS-A21, Mn\u0026thinsp;~\u0026thinsp;5000 g/mol) was obtained from Gelest, Inc. 4,4'-Methylenebis(cyclohexyl isocyanate) (MCI, 90%) and 1,3,5-triformylbenzene (TFB, 98%) were purchased from Sigma-Aldrich and Tokyo Chemical Industry Co., respectively. 1X phosphate-buffered saline (PBS) was purchased from WELGENE. Sylgard 184 PDMS was purchased from Dow Corning. Methyl isobutyl ketone (MIBK) was purchased from Daejung Chemicals. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS, Clevios PH 1000) was provided by Heraeus. Ag flakes (AgFs, DSF-500MWZ-S) were from Daejoo Electronics. Sandpaper (#320 mesh) was purchased from DEERFOS. Novec 7100 and Novec 1700 were obtained from 3M. (3-Glycidyloxypropyl)trimethoxysilane (GOPS), dodecylbenzenesulfonic acid (DBSA), and ethylene glycol were used as PEDOT:PSS additives.\u003c/p\u003e \u003cp\u003e \u003cb\u003eSynthesis of SS-SHP\u003c/b\u003e:\u003c/p\u003e \u003cp\u003eThe shape-stable self-healing polymer (SS-SHP) was synthesized in a two-step process. First, NH\u003csub\u003e2\u003c/sub\u003e-PDMS-NH\u003csub\u003e2\u003c/sub\u003e (12 g) was dissolved in MIBK (30 mL), and MCI (0.1 g) was added. The mixture was stirred at room temperature (20\u0026deg;C) for 24 hr to yield linear PDMS-MCI (conventional SHP). Then, TFB (0.0154 g) was added, followed by 10 min ultrasonication and 6 hr magnetic stirring. The resulting solution was cast or doctor-bladed onto antiadhesive-treated glass substrates (pre-treated with Novec 7100 and Novec 1700, 3:1 vol ratio) and dried at room temperature for 24 hr to form a transparent elastomer. The final composition PDMS-MCI\u003csub\u003e0.7\u003c/sub\u003e-TFB\u003csub\u003e0.3\u003c/sub\u003e was identified as the optimized SS-SHP based on mechanical testing. Variants with different MCI:TFB molar ratios (0.9:0.1 to 0.5:0.5) were also prepared for comparison.\u003c/p\u003e \u003cp\u003e \u003cb\u003eChemical and mechanical characterization of SS-SHP\u003c/b\u003e:\u003c/p\u003e \u003cp\u003eTo evaluate the chemical structure and water permeability, Fourier-transform infrared (FT-IR) spectroscopy (Nicolet iS20, Thermo Scientific) was performed on SS-SHP and conventional SHP samples. To investigate shape-stability, rectangular films of SS-SHP and conventional SHP (2 cm \u0026times; 2 cm, ~\u0026thinsp;300 \u0026micro;m thick) were placed on a flat glass substrate and stored under ambient conditions (20\u0026deg;C, 40% relative humidity) for 20 days. Contact angle measurements (Smartdrop, Femtofab) were conducted by capturing side-view images before and after aging. The angle between the vertical edge of the film and the glass surface was analyzed using ImageJ software to evaluate macroscopic collapse over time. Tensile stress-strain tests were conducted using a universal testing machine (5966, Instron Corporation) to evaluate mechanical robustness. Samples with dimensions of 10 mm \u0026times; 5 mm \u0026times; ~0.5 mm were stretched at a rate of 200%/min under ambient conditions. To assess self-healing performance, samples were completely cut and gently realigned, then self-healed under ambient conditions for 6, 12, or 24 hr. After healing, tensile testing was repeated, and self-healing efficiency was calculated as the ratio of recovered stretchability to that of the pristine film.\u003c/p\u003e \u003cp\u003e \u003cb\u003eFabrication of SS-SHC and IR LED integration\u003c/b\u003e:\u003c/p\u003e \u003cp\u003eTo fabricate the shape-stable self-healing conductor (SS-SHC) electrode, a conductive ink was prepared by mixing AgFs (5 g) with the SS-SHP solution (3 g). The mixture was magnetically stirred for 3 hr at room temperature to ensure uniform dispersion of the AgFs within the polymer matrix. For patterning, a polyimide (PI) stencil mask featuring a dog-bone-shaped opening was placed on the SS-SHP film (thickness\u0026thinsp;~\u0026thinsp;140 \u0026micro;m), and the SS-SHC ink was applied over the mask using a blade. After removing the stencil, the patterned conductor was dried at room temperature to yield the dog-bone-shaped SS-SHC electrode. Following electrode fabrication, an infrared light-emitting diode (IR LED, QBLP650-IR3, QT Brightek) was integrated into the SS-SHC to evaluate electrical self-healing performance. Ethanol was dropped onto the printed SS-SHC electrode to slightly soften the surface and improve contact, and the IR LED terminal was gently pressed into place to form an electrical junction. The assembly was then left at room temperature to allow stable bonding between the LED and the self-healing conductor. The full fabrication process, including dog-bone electrode formation and IR LED integration, is illustrated in \u003cb\u003eSupplementary Fig.\u0026nbsp;8\u003c/b\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003eElectrical characterization of SS-SHC\u003c/b\u003e:\u003c/p\u003e \u003cp\u003eStretchability and resistance were measured using an automatic stretch-testing machine (Jaeil Optical System) while continuously monitoring electrical resistance with a digital multimeter (DMM6500, Keithley). For self-healing assessment, the SS-SHC samples were completely cut and left to heal under ambient conditions. Resistance recovery and stretchability were evaluated after healing. Electrical reliability was further analyzed by measuring surface resistance daily over a 2-week period. Changes in AgF distribution were characterized using tilted cross-sectional scanning electron microscope (SEM, Inspect F50, FEI) imaging, while time-dependent resistance (\u003cem\u003eR\u003c/em\u003e/\u003cem\u003eR\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e) was plotted to compare the SS-SHC with conventional SHC formulations.\u003c/p\u003e \u003cp\u003e \u003cb\u003eFabrication of PEDOT:PSS-based microstructured pressure sensor\u003c/b\u003e:\u003c/p\u003e \u003cp\u003eAn antiadhesive layer was formed by treating sandpaper with Novec 7100:1700 (3:1). PDMS was spin-coated onto the sandpaper at 300 rpm for 100 s, vacuum degassed, and cured at 100\u0026deg;C for 30 min. The microstructured PDMS layer was peeled and placed upside down on an antiadhesive-treated glass. After O\u003csub\u003e2\u003c/sub\u003e plasma treatment (50 W, 30 s), a PEDOT:PSS mixture (10 g PEDOT:PSS, 0.1 g GOPS, 0.01 g DBSA, 0.5 g ethylene glycol) was spin-coated at 700 rpm for 100 s and cured at 150\u0026deg;C for 30 min to form a pressure-sensitive layer. The fabrication process is shown in \u003cb\u003eSupplementary Fig.\u0026nbsp;10\u003c/b\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003eFabrication of wireless pulse pressure monitoring device\u003c/b\u003e:\u003c/p\u003e \u003cp\u003eA 50 \u0026micro;m-thick SS-SHP substrate was fabricated by doctor blade coating the SS-SHP solution onto an antiadhesive-treated slide glass. The wireless circuit\u0026mdash;comprising the power receiving coil, pressure sensor electrodes, and the interconnects for the IR LED\u0026mdash;was patterned onto the substrate by screen-printing the SS-SHC ink through a stencil PI mask. Before the printed SS-SHC ink was fully dried, two critical components were integrated: (1) the IR LED was placed onto the patterned electrode area to form direct electrical contact, and (2) the pressure-sensing layer\u0026mdash;consisting of sandpaper-imprinted PDMS coated with PEDOT:PSS\u0026mdash;was laminated onto the designated region to complete the sensor assembly. After all components were integrated, the device was gently detached from the glass substrate and folded so that the IR LED faced outward and the pressure sensor faced inward, enabling tight, conformal contact with the skin during pulse monitoring. The full fabrication process is illustrated in \u003cb\u003eSupplementary Fig.\u0026nbsp;12\u003c/b\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003eWireless power transmission and optical signal monitoring\u003c/b\u003e:\u003c/p\u003e \u003cp\u003eA transmitting coil resonant at 3.67 MHz was designed using a vector network analyzer (ZNLE4, Rohde \u0026amp; Schwarz). A function generator (AFG1062, Tektronix) was used to apply a sinusoidal AC voltage to the coil, enabling wireless power transfer via inductive coupling to the IR LED integrated within the sensor device. To evaluate optical signal transmission, the IR LED emission was recorded using an IR camera (BFS-U3-17S7M-C, FLIR) equipped with a lens (V2528-MPY, Computar). The NIR camera was configured with a resolution of 1600 \u0026times; 1100 pixels, an f/8 aperture, and a shutter speed of 196 frames/s. To enhance measurement accuracy and eliminate interference from ambient light sources, an IR long-pass filter (LP780, Midwest Optical Systems) was mounted on the camera, allowing only wavelengths above 780 nm to pass. Captured images were processed using ImageJ software. Regions of interest corresponding to the IR LED were cropped, and grayscale pixel values were extracted from each frame to track brightness variations over time. These time-dependent gray values reflect current-induced optical output fluctuations, thereby enabling quantitative assessment of pressure-induced signal changes.\u003c/p\u003e \u003cp\u003e \u003cb\u003eHuman pulse monitoring in healthy and pregnant individuals\u003c/b\u003e:\u003c/p\u003e \u003cp\u003eAll procedures involving human participants were approved by the Institutional Review Board (IRB) of the Korea Institute of Science and Technology (IRB No. KIST-202306-HR-001) and conducted in accordance with institutional guidelines. Pulse monitoring experiments were performed on two subjects: a healthy male in his 20s and a pregnant woman in her 8th month of gestation. The pressure sensor was conformably attached to the wrist, specifically over the radial artery. Pulse signals were measured under resting conditions after ensuring stable respiration and heart rate.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAcknowledgments\u003c/h2\u003e\n\u003cp\u003eThis research was supported through the Industry Technology Alchemist Project (20025702, \u0026ldquo;Development of smart manufacturing multiverse platform based on multisensory fusion avatar and interactive AI\u0026rdquo;) funded by the Ministry of Trade, Industry \u0026amp; Energy (MOTIE, Korea). This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (Grant No. RS-2025-00519762). This research was supported by Korea Institute of Science and Technology (KIST) project (Grant No. 2E33831).\u003c/p\u003e\n\u003ch2\u003eAuthor contributions\u003c/h2\u003e\n\u003cp\u003eH.L. and J.H.K. (Joohyuk Kang) contributed equally to this work. H.L., J.H.K., and W.L. conceived and designed the project and experiments. H.L. and J.W.K. (Jaewoo Kim) developed the SS-SHP and SS-SHC materials. H.L. and J.H.K. conducted the chemical and mechanical characterizations. H.L. fabricated the wireless pressure sensor. H.L. and J.W.K. performed the human subject experiments. H.L., J.H.K., and W.L. wrote the manuscript, and all authors discussed the results and revised the manuscript. W.L. supervised the overall project.\u003c/p\u003e\n\u003ch2\u003eCompeting interests\u003c/h2\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003eReceived: ((will be filled in by the editorial staff))\u003c/p\u003e\u003cp\u003eRevised: ((will be filled in by the editorial staff))\u003c/p\u003e\u003cp\u003ePublished online: ((will be filled in by the editorial staff))\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eWei S et al (2024) Shape-changing electrode array for minimally invasive large-scale intracranial brain activity mapping. Nat Commun 15\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLee W et al (2017) Transparent, conformable, active multielectrode array using organic electrochemical transistors. Proc Natl Acad Sci U S A 114:10554\u0026ndash;10559\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLee W et al (2018) Nonthrombogenic, stretchable, active multielectrode array for electroanatomical mapping. Sci Adv 4:2\u0026ndash;8\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNorton JJS et al (2015) Soft, curved electrode systems capable of integration on the auricle as a persistent brain-computer interface. Proc Natl Acad Sci U S A 112:3920\u0026ndash;3925\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePark DY et al (2017) Self-Powered Real-Time Arterial Pulse Monitoring Using Ultrathin Epidermal Piezoelectric Sensors. Adv Mater 29:1\u0026ndash;9\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKim KY et al (2024) An ultrathin organic\u0026ndash;inorganic integrated device for optical biomarker monitoring. Nat Electron 7\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJeong JW et al (2013) Materials and optimized designs for human-machine interfaces via epidermal electronics. Adv Mater 25:6839\u0026ndash;6846\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKabiri Ameri S et al (2017) Graphene Electronic Tattoo Sensors. ACS Nano 11:7634\u0026ndash;7641\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKeum H, Mccormick M, Liu P, Zhang Y, Omenetto FG (2011) Res ARTICLES Epidermal Electron 333:838\u0026ndash;844\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePeng J (2019) Jeffrey Snyder, G. A figure of merit for flexibility. Sci (1979) 366:690\u0026ndash;691\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLu Y et al (2024) Stretchable graphene\u0026ndash;hydrogel interfaces for wearable and implantable bioelectronics. Nat Electron 7:51\u0026ndash;65\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJiang Z et al (2022) A 1.3-micrometre-thick elastic conductor for seamless on-skin and implantable sensors. Nat Electron 5:784\u0026ndash;793\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eD\u0026ouml;hler D et al (2020) Tuning the Self-Healing Response of Poly(dimethylsiloxane)-Based Elastomers. ACS Appl Polym Mater 2:4127\u0026ndash;4139\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKim SH et al (2019) An Ultrastretchable and Self-Healable Nanocomposite Conductor Enabled by Autonomously Percolative Electrical Pathways. ACS Nano 13:6531\u0026ndash;6539\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKang J et al (2018) Tough and Water-Insensitive Self-Healing Elastomer for Robust Electronic Skin. Adv Mater 30:1\u0026ndash;8\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWu X, Wang J, Huang J, Yang S, Robust (2019) Stretchable, and Self-Healable Supramolecular Elastomers Synergistically Cross-Linked by Hydrogen Bonds and Coordination Bonds. ACS Appl Mater Interfaces 11:7387\u0026ndash;7396\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYan X et al (2018) Quadruple H-Bonding cross-linked supramolecular polymeric materials as substrates for stretchable, antitearing, and self-healable thin film electrodes. J Am Chem Soc 140:5280\u0026ndash;5289\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu T et al (2023) Extremely strengthening fatigue resistance, elastic restorability and thermodynamic stability of a soft transparent self-healing network based on a dynamic molecular confinement-induced bioinspired nanostructure. Mater Horiz 10:2968\u0026ndash;2979\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKim S, Jeon H, Koo JM, Oh DX, Park J (2024) Practical Applications of Self-Healing Polymers Beyond Mechanical and Electrical Recovery. Adv Sci 11:1\u0026ndash;22\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang Y, Urban MW (2018) Self-Healing of Polymers via Supramolecular Chemistry. Adv Mater Interfaces 5:1\u0026ndash;19\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIkura R et al (2022) Design of self-healing and self-restoring materials utilizing reversible and movable crosslinks. NPG Asia Mater 14:1\u0026ndash;17\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi J et al (2024) Hydrogen-bonded polymeric materials with high mechanical properties and high self-healing capacity. Mater Chem Front 3828\u0026ndash;3858. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1039/d4qm00472h\u003c/span\u003e\u003cspan address=\"10.1039/d4qm00472h\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXie Z, Hu BL, Li RW, Zhang Q (2021) Hydrogen Bonding in Self-Healing Elastomers. ACS Omega 6:9319\u0026ndash;9333\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSong K, Il et al (2020) Adaptive self-healing electronic epineurium for chronic bidirectional neural interfaces. Nat Commun 11\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJang TM et al (2024) Stretchable and biodegradable self-healing conductors for multifunctional electronics. Sci Adv 10:1\u0026ndash;10\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePark H et al (2023) Toughening self-healing elastomer crosslinked by metal\u0026ndash;ligand coordination through mixed counter anion dynamics. Nat Commun 14:1\u0026ndash;10\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePadhan AK et al (2024) Rapid self-healing and superior toughness in ionically crosslinked polymer ionogels and strain sensing applications. J Mater Chem Mater 12:9508\u0026ndash;9517\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYao H et al (2023) Water-Insensitive Self-Healing Materials: From Network Structure Design to Advanced Soft Electronics. Adv Funct Mater 33:1\u0026ndash;25\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen L et al (2023) Self-healing polymers through hydrogen-bond cross-linking: synthesis and electronic applications. Mater Horiz 10:4000\u0026ndash;4032\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDawelbeit A, Yu M (2021) Transient confinement of the quaternary tetramethylammonium tetrafluoroborate salt in nylon 6,6 fibres: Structural developments for high performance properties. Materials 14\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHu J, Wu Y, Zhang C, Tang BZ, Chen S (2017) Self-adaptive water vapor permeability and its hydrogen bonding switches of bio-inspired polymer thin films. Mater Chem Front 1:2027\u0026ndash;2030\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMilkin P, Danzer M, Ionov L (2022) Self-Healing and Electrical Properties of Viscoelastic Polymer\u0026ndash;Carbon Blends. Macromol Rapid Commun 43:1\u0026ndash;12\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEl Choufi N, Mustapha S, Tehrani B, A., Grady BP (2022) An Overview of Self-Healable Polymers and Recent Advances in the Field. Macromol Rapid Commun 43:1\u0026ndash;24\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWu J, Cai LH, Weitz DA (2017) Tough Self-Healing Elastomers by Molecular Enforced Integration of Covalent and Reversible Networks. Adv Mater 29:1702616\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEhrhardt D et al (2020) Self-Healing in Mobility-Restricted Conditions Maintaining Mechanical Robustness: Furan\u0026ndash;Maleimide Diels\u0026ndash;Alder Cycloadditions in Polymer Networks for Ambient Applications. Polym 2020 12(12):2543\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePark H et al (2023) Toughening self-healing elastomer crosslinked by metal\u0026ndash;ligand coordination through mixed counter anion dynamics. \u003cem\u003eNature Communications 2023 14:1\u003c/em\u003e 14, 1\u0026ndash;10\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiang C et al (2025) Stiff and self-healing hydrogels by polymer entanglements in co-planar nanoconfinement. Nat Mater 24:599\u0026ndash;606\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePark H et al (2023) Toughening self-healing elastomer crosslinked by metal\u0026ndash;ligand coordination through mixed counter anion dynamics. Nat Commun 14:1\u0026ndash;10\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJiang Z et al (2020) Self-Healable, and Recyclable Visible-Light-Responsive Hydrogel Actuators. Angew Chem 132:7115\u0026ndash;7122Strong\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAgache PG, Monneur C, Leveque JL, De Rigal J (1980) Original Contributions Mechanical Properties and Young\u0026rsquo;s Modulus of Human Skin in Vivo. Arch Dermatol Res 269:221\u0026ndash;232\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMei JF et al (2016) A Highly Stretchable and Autonomous Self-Healing Polymer Based on Combination of Pt\u0026middot;\u0026middot;\u0026middot;Pt and π\u0026ndash;π Interactions. Macromol Rapid Commun 37:1667\u0026ndash;1675\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang Z et al (2016) High Sensitivity, Wearable, Piezoresistive Pressure Sensors Based on Irregular Microhump Structures and Its Applications in Body Motion Sensing. \u003cem\u003eSmall\u003c/em\u003e 12, 3827\u0026ndash;3836\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMatsuhisa N et al (2021) High-frequency and intrinsically stretchable polymer diodes. Nature 600:246\u0026ndash;252\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePark J et al (2018) Soft, smart contact lenses with integrations of wireless circuits, glucose sensors, and displays. Sci Adv 4:1\u0026ndash;11\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAdiono T, Fuada S (2017) Investigation of Optical Interference Noise Characteristics in Visible Light Communication System. 126:612\u0026ndash;615\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMoreira AJC, Valadas RT (1996) \u0026amp; De Oliveira Duarte, A. M. Performance of infrared transmission systems under ambient light interference. \u003cem\u003eIEE Proceedings: Optoelectronics\u003c/em\u003e 143, 339\u0026ndash;346\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu C, Kelley SO, Wang Z (2024) Self-Healing Materials for Bioelectronic Devices. Adv Mater 36:1\u0026ndash;11\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang K et al (2021) Self-healing and stretchable PDMS-based bifunctional sensor enabled by synergistic dynamic interactions. Chem Eng J 412:128734\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYing H, Zhang Y, Cheng J (2014) Dynamic urea bond for the design of reversible and self-healing polymers. Nat Commun 5:1\u0026ndash;9\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRonald C, HortonJr., \u0026dagger; TM, Herne (1997) *,\u0026Dagger; and \u0026amp; David C. Myles*, \u0026dagger;. Aldehyde-Terminated Self-Assembled Monolayers on Gold: Immobilization of Amines onto Gold Surfaces. J Am Chem Soc 119:12980\u0026ndash;12981\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMatyshak VA et al (2009) Properties of surface compounds in methanol conversion on γ-Al 2O3: Data of in situ IR spectroscopy. Kinet Catal 50:111\u0026ndash;121\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShi C, Liu X, Chuai R, Piezoresistive Sensitivity (2009) Linearity and Resistance Time Drift of Polysilicon Nanofilms with Different Deposition Temperatures. \u003cem\u003eSensors 2009, Vol. 9, Pages 1141\u0026ndash;1166\u003c/em\u003e 9, 1141\u0026ndash;1166\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMilkin P, Danzer M, Ionov L (2022) Self-Healing and Electrical Properties of Viscoelastic Polymer\u0026ndash;Carbon Blends. Macromol Rapid Commun 43:2200307\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang Z et al (2016) High Sensitivity, Wearable, Piezoresistive Pressure Sensors Based on Irregular Microhump Structures and Its Applications in Body Motion Sensing. \u003cem\u003eSmall\u003c/em\u003e 12, 3827\u0026ndash;3836\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang X et al (2014) Silk-Molded Flexible, Ultrasensitive, and Highly Stable Electronic Skin for Monitoring Human Physiological Signals. Adv Mater 26:1336\u0026ndash;1342\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKhoshdel AR, Carney S, Gillies A (2010) The impact of arm position and pulse pressure on the validation of a wrist-cuff blood pressure measurement device in a high risk population. Int J Gen Med 3:119\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6919168/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6919168/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSelf-healing polymers offer softness and conformability suitable for skin-interfaced electronics. However, their flowable nature often leads to gradual shape deformation, making them unsuitable for circuit-integrated devices that require structural stability. Here, we introduce a shape-stable self-healing polymer (SS-SHP) featuring a branched polymer network reinforced with reversible imine and hydrogen bonds. The SS-SHP maintained its original shape for 20 days with less than a 5% reduction in storage modulus. In addition, its low Young\u0026rsquo;s modulus of 576 kPa, comparable to that of skin, allowed conformal contact with microtextured skin surfaces. By embedding Ag flakes into the SS-SHP matrix, we developed a self-healing conductor that showed stable surface resistance over time, avoiding the conductivity degradation typically observed in conventional SHPs. Utilizing the SS-SHP as both the substrate and the electrode matrix, we fabricated a wireless arterial pressure sensor integrated with an optical signal transmission circuit. Due to the skin-like softness of the SS-SHP, the device conformed intimately to the wrist without external contact pressure, enabling precise detection of arterial pulse signals and distinguishing between pulse waveforms from a healthy subject and a pregnant individual. The system successfully translated dynamic pressure fluctuations into real-time optical signals, allowing continuous monitoring of physiological activity through a compact and skin-conformal platform.\u003c/p\u003e","manuscriptTitle":"A Conformable Shape-Stable Self-Healing Polymer Platform for Continuous Wireless Arterial Pulse Monitoring","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-02 09:55:20","doi":"10.21203/rs.3.rs-6919168/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"058b7876-106e-48a0-84ec-88dc1b0fa089","owner":[],"postedDate":"July 2nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":50817896,"name":"Physical sciences/Materials science/Soft materials/Polymers"},{"id":50817897,"name":"Physical sciences/Materials science/Materials for devices/Electronic devices"}],"tags":[],"updatedAt":"2026-04-20T17:05:18+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-02 09:55:20","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6919168","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6919168","identity":"rs-6919168","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}