A Reconfigurable Piezo-Ionotropic Polymer Membrane for Sustainable Multi-Resonance Acoustic Sensing

A Reconfigurable Piezo-Ionotropic Polymer Membrane for Sustainable Multi-Resonance Acoustic Sensing | 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 Reconfigurable Piezo-Ionotropic Polymer Membrane for Sustainable Multi-Resonance Acoustic Sensing Do Hwan Kim, Wu Bin Ying, Joo Sung Kim, zhe YU, Zhengyang Kong, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5810151/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 02 Sep, 2025 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Abstract Sensorineural hearing loss is the most common form of deafness, typically resulting from the loss of sensory cells on the basilar membrane, which cannot regenerate and thus lose sensitivity to sound vibrations. Here, we report a reconfigurable piezo-ionotropic polymer membrane engineered for biomimetic sustainable multi-resonance acoustic sensing, offering exceptional sensitivity (530 kPa⁻¹) and broadband frequency discrimination (20 to 3300 Hz) while remaining resistant to "dying." The acoustic sensing capability is driven by an ion hitching-in cage effect intrinsic to the ion gel combined with fluorinated polyurethane. In this platform, the engineered ionotropic polymer stretches under acoustic vibrations, allowing cations to penetrate the widened hard segments and engage in strong ion-dipole interactions (cation···F), thereby restricting ion flux and amplifying impedance changes. Additionally, the sensor’s sustainability is ensured through its self-healing properties and hydrophobic components, which enable effective self-repair in both conventional and aqueous environments without ion leakage, achieving a room-temperature healing speed of 0.3–0.4 µm/min. Leveraging this newly developed sustainable acoustic sensing technology, our devices demonstrate high proficiency in identifying specific sounds in everyday environments (e.g., human voices, piano notes), underscoring their potential as artificial basilar membranes. Physical sciences/Materials science/Soft materials/Gels and hydrogels Physical sciences/Materials science/Materials for devices/Sensors and biosensors Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Main Human sensory tissues are constantly exposed to the external environment that facilitates the effective capture of necessary physical inputs (e.g., touch, sound, heat, light, and chemicals) for sensory function 1 – 3 . However, prolonged overstimulation and exposure to physical hazards can lead to damage to sensory receptors. To protect the uniform distribution and function of these receptors from damage, sensory tissues directly exposed to the environment, including the epidermis, olfactory epithelium and gustatory cells, undergo continuous regeneration after injury 4 – 6 . In contrast, hair cells and the basilar membranes in the auditory system exhibit an extremely limited regenerative capacity in mammals 7 , 8 . Moreover, the intricate structure of hair cells makes them particularly susceptible to damage from aging or disease, leading to irreversible sensorineural hearing loss (SNHL), the most prevalent form of sensory impairment in humans 9 , 10 . Currently, cochlear implants are the primary therapeutic option for SNHL. However, these devices require invasive surgical procedures that substitute the natural auditory system, posing significant risks, including tissue necrosis, facial paralysis and meningitis, as well as significant financial burdens for patients 11 – 13 . Addressing the underlying cause of SNHL could revolutionize treatment strategies. Since SNHL primarily results from damage to hair cells on the basilar membrane while other auditory tissues remain intact, the development of an artificial basilar membrane could substantially reduce the scope and complexity of necessary surgical interventions. To meet the requirements for constructing an artificial basilar membrane, multi-resonant acoustic sensors have been developed by mimicking the biological auditory system based on piezoelectric 14 – 16 , triboelectric 17 , 18 , capacitive 19 – 21 and resistive materials 22 , 23 , achieving the required sensitivity. Despite these advances, a significant challenge remains due to the use of rigid materials in these sensors, which are prone to cracking under prolonged acoustic vibrations and could potentially cause SNHL anew. Additionally, the mechanical mismatch between the rigid electronic components and the soft biological tissues frequently leads to tissue damage 24 , 25 . More importantly, conventional electronic conduction-driven sensors, unlike the ionic conduction in biological systems, can induce redox reactions that result in corrosion and gas evolution when exposed to wet environments (e.g., biofluid) during operation 26 . To address these mechanical and electrochemical mismatches, an ideal design for an artificial basilar membrane would use entirely soft materials that mimic the ionotropic mechanotransduction mechanisms observed in biological sensory systems. Furthermore, considering the non-regenerative properties of hair cells and the high water content (98–99%) of the lymph fluid in the inner ear 27 , it is crucial that the artificial basilar membrane possesses self-healing capability in humid environments, ensuring its durability and functionality for in vivo implantability. Here, inspired by the ionotropic mechanotransduction mechanism and structural features of the basilar membrane in the human auditory system, we report a reconfigurable piezo-ionotropic polymer membrane engineered for biomimetic, sustainable, multi-resonance acoustic sensing, offering exceptional sensitivity and frequency discrimination while being immune to “dying.” To achieve this, hydrophobic fluorine groups were initially incorporated into the polyurethane molecular chain along with units of high electronegativity and dynamic covalent bonds in the hard segments, resulting in underwater self-healing properties. Subsequently, ionic liquid ([BMIM] + [TFSI] - ) was employed as an ion donor and combined with self-healable fluorinated polyurethane (SFPU) to develop the self-healing piezo-ionotropic polymer (ShPiP), the key sensing material in the piezo-ionotropic multi-resonance acoustic sensor (PiMAS). PiMAS demonstrates significant advancements in both sensitivity and frequency discrimination. The ion hitching-in cage effect, enabled by the dynamic reconfiguration of polymer networks, efficiently regulates ion flux under acoustic pressure, thereby enhancing PiMAS’s acoustic sensitivity. Acoustic pressure causes the polymer chains in ShPiP to stretch, creating interstitial passages between hard segments-akin to unlocking a sealed cage. This ion hitching-in cage mechanism, combined with reversible ion-dipole interactions from the highly electronegative fluorine groups within the hard segments, enables cations to access the unlocked cage structure, effectively hitching ions and increasing impedance. As a result, PiMAS can accurately identify sound frequencies from 20 to 3200 Hz, particularly within the human speech frequency range (men: 64–523 Hz; women: 160–1200 Hz), demonstrating high sensitivity to both sound pressure and strain. Furthermore, the dynamic and reconfigurable properties of ShPiP enable PiMAS to maintain its waterproof and self-healing capabilities across diverse environments, including air, water, and even lymphatic fluids, offering substantial potential for preventing sensorineural hearing loss (SNHL). Design of piezo-ionotropic multi-resonance acoustic sensor Sound transmission in the human auditory system involves several stages: vibration of the tympanic membrane, conduction through the ossicles, and generation of pressure waves within the cochlea, which displace the basilar membrane (Fig. 1 a) 8 , 28 . The basilar membrane plays a critical role in auditory perception, varying in width and stiffness along its length to decompose complex acoustic signals into their constituent frequencies. This frequency decomposition is essential for the next stage of auditory perception, where ionotropic mechanotransduction occurs in hair cells located on the basilar membrane. Vibrations of the basilar membrane cause the bending of cilia on these hair cells, which stretches the tip links and activates ion channels (Fig. 1 b). This sequence allows cations to enter the hair cells, generating the receptor potential necessary for sound detection. Despite the efficiency of this mechanism, hair cells are extremely delicate, and because they cannot regenerate, any damage leads to irreversible sensorineural hearing loss (SNHL) (Fig. 1 b, rightmost). Inspired by this human ionotropic mechanotransduction mechanism and the structural features of basilar membranes, we have developed a sustainable PiMAS, comprising eight channels, each formed by ShPiP and AgNWs interdigitated electrodes. These channels, with thicknesses ranging from 100 to 700 µm, effectively detect sounds in the 20–3300 Hz range, covering almost the entire conventional sound frequency range of 20–4000 Hz (Fig. 1 c). ShPiP, the key material for sensing functionality, consists of SFPU and ionic liquid ([BMIM] + [TFSI] - ). The structure of SFPUs features hard segments introduced by dynamic disulfide bonds and fluorine groups, with varying soft/hard segment ratios (Z = 0.6–0.78) and similar molecular weights (6.9–7.1 × 10 4 g/mol) as shown in Fig. 1 d. Their synthesis steps, structural characterization and analysis of mechanical properties were detailed in the Supporting Information (Supplementary Figs. 1–4, Supplementary Note 1, and Supplementary Tables 1, 2). A series of ShPiPs were prepared by blending a certain proportion of [BMIM] + [TFSI] - with SFPUs (Supplementary Figs. 5–9 and Supplementary Note 2). Independent gradient model (IGM) analysis revealed that the initial binding energy between [BMIM] + and [TFSI] - was − 87.60 kcal/mol (Fig. 1 d, right). Attraction between the fluorine group and [BMIM] + reduced the binding energy between [BMIM] + and [TFSI] - to -81.04 kcal/mol, indicating that the fluorine group in SFPU acts as an ion-hitching site, capable of forming ion-dipole interactions with [BMIM] + 29,30 . Subsequently, we validated the aforementioned calculations by characterizing the asymmetric stretching bands of S = O and N-S of [TFSI] - in ShPiP, as well as the associated and free carbonyl groups, using infrared spectroscopy (detailed description in Supplementary Fig. 10a, b and Supplementary Note 2). X-ray diffraction (XRD) spectra result further supported these analyses (detailed description in Supplementary Fig. 10c, d) 31 . Under the influence of ion-dipole interactions, PiMAS will possess a perceptual mechanism and high sensitivity akin to that of the basilar membrane (Fig. 1 e). In its quiescent state, the hard segments of the SFPU are associated through dipole-dipole interactions among fluorine groups and hydrogen-bonding, forming a closed hard domain where ions maintain a dynamic equilibrium both inside and outside. When sound vibrations bend PiMAS channels, the resulting stretch causes the associated hard segments of the ShPiP to separate, creating interstitial passages within the hard domains where ions are captured under the effect of ion-dipole interactions. This process further restricts the ions and accentuates the impedance increase induced by stretching, thereby enhancing sensitivity. In addition, to overcome the limitations of non-regenerative hair cells and SNHL, the acoustic sensor is designed to possess self-healing capabilities in conventional environments, water and lymphatic fluid. This self-healing capability is driven by the synergistic effects of dynamic disulfide bond exchange, dipole-dipole interactions among fluorine groups and the enhanced chain mobility due to the plasticizing effect of the ionic liquid (Fig. 1 e rightmost). Additionally, the strong hydrophobic properties conferred by the polybutadiene structure and fluorine groups within the ShPiP, coupled with the weak miscibility of [BMIM] + [TFSI] - with water, ensure that these driving forces remain unaffected by water molecules, facilitating underwater self-healing capabilities. Discrimination ability of the PiMAS for sound frequency and sound pressure We first assessed the resolution of the PiMAS with respect to sound pressure and frequency. The PiMAS was positioned between a speaker and a laser vibrometer and concurrently connected to an LCR meter for synchronous monitoring of impedance and amplitude changes (Fig. 2 a). The distribution of ShPiP and AgNW interdigitated electrodes within each channel of the PiMAS is depicted in Fig. 2 b, with the fabrication method detailed in Supplementary Fig. 11. When sound vibrations induce deformation in the channel, the impedance changed because of variations in ion flux within the ShPiP. As shown in Fig. 2 c, Channel 1 exhibited its maximum response impedance at 110 Hz and its maximum sound response limit at 805 Hz; similarly, it demonstrated its maximum amplitude at 106 Hz, the peak resonant frequency. Beyond 803 Hz, the amplitude of Channel 1 remained unchanged. A comparison of the impedance and amplitude profiles revealed a close correspondence in their characteristic response frequencies to acoustic stimuli. This indicated that the impedance signals originated from the channel vibrations and that PiMAS successfully converted mechanical sound stimuli into electrical signals, mimicking the function of the human basilar membrane. Subsequently, to verify whether these electrical signal changes originated from impedance alterations in the AgNW electrodes during vibration, a dedicated sound frequency scan ranging from 20 Hz to 4000 Hz was performed on the AgNW electrodes alone (Supplementary Fig. 12 and Supplementary Note 3). The AgNW electrodes demonstrated remarkably stable impedance throughout the test due to their inherent stretchability, confirming that the conversion of mechanical sound stimuli into electrical signals was primarily facilitated by the ShPiP. Furthermore, we tested the sensitivity of Channel 1 at its maximum resonant frequency by varying the sound pressure (Fig. 2 d). As the sound pressure gradually increased from 65 dB to 91 dB, the response impedance also increased correspondingly, yielding a sensitivity of 530 kPa - 1 (inset in Fig. 2 d). The responses of channels 1–8 in PiMAS to acoustic sources in terms of impedance signals and amplitude have been aggregated in Fig. 2 e and Supplementary Fig. 13. The trends in impedance and amplitude responses were consistent across all channels. Moreover, as the thickness of the channels increased, their maximum response frequencies shifted from approximately 110 Hz to 680 Hz, and the upper limits of their response frequencies extended from around 800 Hz to 3300 Hz (Supplementary Fig. 14). This indicates a gradual shift in their response frequencies from the low to high frequency regions, consistent with the response characteristics of the basilar membrane to sound and conforming to the resonant frequency formula defined in Eq. 1 32 : $$\:{f}_{R}\:\propto\:\:t/{l}^{2}\bullet\:\sqrt{E/\rho\:}$$ , where f R represented the resonant frequency, t and l denoted the thickness and length of the ShPiP, E and ρ signified the elastic modulus and density, respectively. The sound pressure sensitivity of channels 1–8 at their maximum resonant frequencies was summarized in Fig. 2 f. An increase in thickness resulted in a slight decrease in sensitivity, as the channel thickness influenced its deformation magnitude under same sound pressure according to Newton’s second law 33 . Nevertheless, all channels exhibited sufficiently high-pressure sensitivity (350–530 kPa - 1 ). As sound vibration induced elongation in the channels, we also calculated the gauge factor (GF) for these channels, summarized in Fig. 2 g and Supplementary Fig. 15. Similar to sound pressure sensitivity, the tensile sensitivity decreased slightly with increasing channel thickness, yet all channels demonstrated sufficiently high tensile sensitivity (49.2–53.6). Sensing mechanism of PiMAS under acoustically induced vibration The exceptional sensitivity of the PiMAS is attributed to the inherent ionotropic mechanotransduction mechanism, termed the ion hitching-in cage effect. The driving force for ion flux stemmed from the stretching induced by acoustic pressure. Such tensile stress separates the hard domains of the SFPU and increases their d-spacing 34 , 35 , enabling ion-dipole interactions between [BMIM] + [TFSI] - and fluorine groups of hard segments. Simultaneously, an external electric field prompts the migration of ions towards the electrodes. Consequently, the total ion flux driven by tensile stress is governed by the competitive relationship between the strength of ion-dipole interactions and electric field-induced ion migration. To explore this complex ion flux pathway, we utilized in-situ Raman spectroscopy for ionic intensity mapping at three distinct locations in the ShPiP samples: adjacent to the anode (Position-1#), intermediate (Position-2#), and adjacent to the cathode (Position-3#). The testing and data analysis methods are shown in Supplementary Fig. 16 and described in Supplementary Note 4. Additionally, we prepared a variant of pristine PU-based iongel (PU-iongel) without fluorine in the hard segments of self-healing polyurethane (SPU), while maintaining the same other components for comparative analysis of ion-dipole interactions. The color scale represented the intensity ratio of cations ([BMIM] + ) to polyurethane, with deeper red indicating higher cation concentration. In fluorine-free PU-iongel, the flux of cations towards the right was clearly observable at all positions under tensile stress (Fig. 3 a). At Position-1#, cations repelled by the anode moved further away; at Position-2#, the ion flux towards the cathode was more pronounced; at Position-3#, cations accumulated near the cathode. This flux behavior is typical of fluidic ions driven by the electric field direction towards the cathode and the piezoionic effect 36 – 38 , which is caused by tensile stress-induced compression perpendicular to the direction of stretch. For ShPiP containing fluorine in the hard segments, only minimal flux of cations was observed at all positions after stretching (Fig. 3 b). Specifically, at Position-1#, cations repelled from the left anode were biased towards the right with a distribution that remained nearly unchanged post-stretching. At Position-2#, cations were uniformly distributed across the region due to equal distance from both electrodes, with slight aggregation on the upper side possibly due to longitudinal compression of the polymer chains, while maintaining a uniform lateral distribution. At Position-3#, cations attracted to the right cathode were biased towards the right with a distribution that remained nearly unchanged post-stretching. Regarding the anions ([TFSI] - ) in both ShPiP and PU-iongel, freed from polymer chain constraints (Supplementary Fig. 17,18 and Supplementary Note 4), they migrated leftwards under longitudinal compression and electric field drive. A comparison of the overlapped areas of anion movement before and after stretching revealed only slightly less ion flux in ShPiP than in PU-iongel (Supplementary Fig. 19). This indicates that the negatively charged fluorine groups in SFPU strongly bound [BMIM] + through ion-dipole interactions but form relatively weak ion-dipole bonds with [TFSI] - . In the ion flux process, the hard domains containing fluorine groups functioned like a closed cage (Fig. 3 c). Acoustic pressure-induced stretching could form interstitial passages in these domains, creating ion-accessible pathways similar to an open cage. In the PU-iongel (Fig. 3 d top), cations were captured but could escape after multiple interactions due to weaker ion-dipole interactions. This resulted in only slight reductions in cation mobility. In contrast, in ShPiP (Fig. 3 d bottom), stronger ion-dipole interactions between the fluorine groups and [BMIM] + restricted cation mobility more effectively, leading to greater impedance changes and enhanced sensitivity. A comparison of strain-impedance curves (Supplementary Fig. 20a) indicated that the ion hitching-in cage effect in ShPiP resulted in higher stretch sensitivity than in PU-iongel. In the PU-NH-iongel variant with fewer hard domains, based on SPU-NH (Supplementary Fig. 20b–c and Supplementary Note 4), the ion hitching-in cage effect was minimal, resulting in reduced sensitivity. The ion hitching-in cage effect in ShPiP was also found to be reversible; IR spectroscopy and fatigue resistance tests confirmed that the hard domains opened with strain but returned to their original state upon release, maintaining stable impedance changes even after repeated stretching (Supplementary Fig. 21, 22). Self-healing mechanism, demonstration and performance of the PiMAS To address the limitations of non-regenerative hair cells and issues associated with SNHL, we recognized the need for acoustic sensors with self-healing capabilities in conventional environments, underwater, and even in lymphatic fluid. We achieved these objectives through the molecular design of ShPiP. Specifically, polybutadiene was selected as the soft segment to enhance the overall hydrophobicity of the polyurethane, followed by the introduction of fluorine groups into the hard segments to further increase hydrophobicity. Additionally, disulfide bonds were incorporated into the hard segments to impart self-healing capability to the resulting polyurethanes. Due to the dipole-dipole interactions of the fluorine, the disulfide bonds within the hard segments were brought closer together, facilitating bond exchange and enhancing self-healing efficiency (Supplementary Fig. 23 and Supplementary Note 5). Ab initio molecular dynamics (AIMD) simulations (Fig. 4 a) revealed that SFPU molecular chains tightly cluster together, distinctly separating from water molecule aggregates. The distance between the two aggregates was greater than 3 Å, indicating the tight binding of SFPU molecular chains and their excellent hydrophobicity. In addition, the radial distribution curves obtained from AIMD and Density Functional Theory (DFT) calculations (Fig. 4 b) showed that the hydrogen bonds (O-H) among water molecules were the most abundant, with no hydrogen bonds forming between SFPU and water molecules. And the average length of hydrogen bonds between carbonyl groups in the hard segments (− N−H∙∙∙O = C−) was 3 Å (2.7–3.3 Å), which was the distance between the hard segments. The distance was less than that between SFPU molecular chains and water molecules, indicating that the disulfide bond exchange reactions occurring between hard segments were almost undisturbed by water molecules. Then, we tested their water contact angles, which reached up to 112°. Even after soaking in water for five days, the water contact angle changed very little, performing much better than commercial polyurethanes lacking hydrophobic structures (Supplementary Fig. 24). As shown in Supplementary Fig. 25 and Movie 1, two severed SFPU films were drawn together on the water's surface through dipole-dipole interactions between fluorine groups. Once close enough, disulfide bond exchange began, ultimately achieving underwater self-healing through the combined effects of fluorine group interactions and disulfide bond exchange. Further studies on ShPiP's self-healing abilities in water and artificial lymph fluid revealed a self-healing speed comparable to that in conventional environments, with the process and performance remaining almost unaffected by water molecules (Supplementary Fig. 26–29 and Supplementary Note 5). However, the sensing channel of PiMAS included both ShPiP and AgNW, so we conducted self-healing tests on the complete sensing channel. We placed channel-1 in artificial lymph fluid, cut and rejoined it (Fig. 4 c), and observed that it fully self-healed within 24 hours (Supplementary Movie 2). Figure 4 d (top row) shows the self-healing process of the channel as observed under a microscope in cross-section. After the channel was severed, ShPiP began the self-healing process first, followed by reconnection of the AgNW layer on its surface, resulting in a "passive" self-healing effect 5 , 39 . As shown in Supplementary Movie 3, completely cutting the ShPiP coated with the AgNW layer instantly extinguished the LEDs connected on either side of the layer; however, the "passive" self-healing subsequently relit the LEDs. Figure 4 d (bottom row) displays repeated response curves of the channel to a 100 Hz audio frequency throughout the self-healing process, showing a gradual recovery from complete loss of sensing performance. This finding highlights the crucial role of ShPiP in the self-healing function of the entire channel. Furthermore, Fig. 4 e and f show that after self-healing, the channel’s ability to discriminate sound frequency and loudness was only minimally reduced. In summary, PiMAS not only demonstrated excellent pressure and stretch sensitivity but also outstanding multi-scenario self-healing capabilities. Compared to other iontronic and non-iontronic sensors with similar functions (Fig. 4 g, Supplementary Table 3), PiMAS performed significantly better. This advancement indicates that our sensor not only provides precise feedback but also significantly enhances sustainability and reliability in complex environments. Application of the PiMAS in recognizing real-world sounds Finally, we applied PiMAS to the recognition of real-world sounds. Male vocal cords are typically longer and thicker, with larger throat spaces, which produce lower-frequency sounds (Fig. 5 a). In contrast, female vocal cords are generally shorter and thinner, with smaller throat spaces, resulting in higher-frequency sounds. To test this, three males and three females each said “hello, sensor,” and our sensor accurately and sensitively detected each utterance (Fig. 5 b, left). Fourier transformation of the time-domain graphs into frequency-domain graphs revealed that the detected frequencies for male voices were lower than those for female voices, demonstrating the excellent frequency discrimination capability of PiMAS (Fig. 5 b, right). We further tested PiMAS’s response to six piano keys, each with a distinct characteristic frequency (4# – 76#: 32.70 Hz – 2093.02 Hz), as shown in Fig. 5 c. Since each piano key contains additional harmonic frequencies, this experiment tested the frequency resolution of the sensor (Fig. 5 d). In the frequency-impedance spectra (Fig. 5 d, 1st and 3rd rows), all frequencies within each piano key were sensitively detected, with the characteristic frequency showing the highest impedance response. The time-frequency-impedance mapping (Fig. 5 d, 2nd and 4th rows) demonstrated that all frequencies from each key press were detected continuously until the sound ceased, with the characteristic frequency having the largest and longest-lasting impedance response. We also used ShPiP to analyze three songs: a bass singing “Doubt” (82–392 Hz), a baritone singing “Marechiare” (123–493 Hz), and a tenor singing “Nessun dorma” (164–698 Hz), and compared PiMAS’s performance to that of commercial acoustic sensors. Actual test images and response impedance spectra are shown in Fig. 5 e, f, with video documentation in Supplementary Movie 4. The results showed that PiMAS provided significantly clearer signal feedback at the same sound pressure level compared to commercial sound sensor arrays, with sensitivities 3.5 times (bass), 3.4 times (baritone), and 3.2 times (tenor) higher (Supplementary Fig. 30). In conclusion, we developed PiMAS, inspired by the physiological characteristics of the human basilar membrane, which exhibits high sensitivity to various sound pressures and frequencies while addressing the non-regenerative limitation of basilar membrane hair cells. Composed of ShPiP and AgNW interdigitated electrodes, PiMAS efficiently converts sound stimuli into mechanical vibrations, detecting frequencies across a range of 20–3300 Hz and sound pressures above 65 dB with high sensitivity to sound pressure (530 kPa⁻¹) and stretch (53.6), surpassing most ionic sensors. This sensitivity is primarily due to the ion hitching-in cage effect, driven by ion-dipole interactions between SFPU and [BMIM]⁺[TFSI]⁻ within ShPiP, which restricts cation flux, resulting in more pronounced impedance changes. Moreover, ShPiP’s self-healing capability in conventional environments, underwater, and even in lymphatic fluid is attributed to a combination of dynamic disulfide bond exchange, fluorine-group dipole-dipole interactions, and increased chain mobility due to the ionic liquid’s plasticizing effect. PiMAS effectively differentiates between male and female voice frequencies and accurately detects characteristic frequencies of various piano keys, demonstrating superior responsiveness to singing voices compared to commercial acoustic sensors. The structural design and material functionality presented in this work provide valuable insights for developing future sustainable iontronic devices and acoustic sensors. Moving forward, we aim to further optimize PiMAS's structure and performance and explore its application in a wider range of settings. Methods Materials. Hydroxyl-terminated polybutadiene (HTPB, Mn = 2700–3300 g/mol) was acquired from Energy Chemical, and its OH index was quantitatively assayed via titration prior to utilization. Isophorone diisocyanate (IPDI, 99%), dibutyltin dilaurate (DBTDL, 95%), anhydrous tetrahydrofuran (THF, 99.5%), anhydrous N,N-Dimethylformamide (DMF, 99.8%), 4-aminophenyl disulfide (98%), 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol (> 98%), and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM] + [TFSI] − , 98%) were procured from Aladdin (China) and were used as received without any further purification process. Silver nanowire suspensions (AgNW, diameter: 32 ± 5 nm, length: 25 ± 5 µm), obtained from Nanopyxis Corp., were diluted 4-fold before electrode spray-coating applications. The recipe of artificial inner ear lymphatic fluid: H 2 O 1L, NaCl 130–140mmol/L, KCl 4.5mmol, CaCl 2 2 mmol, MgCl 2 1 mmol, NaHCO 3 11.5 mmol, NaH 2 PO 4 1 mmol, glucose 67.5 mg/dL. Polyurethane Synthesis 1) Self-healable fluorinated polyurethane (SFPU) HTPB (10 g), THF (50 g) and IPDI (calculated quantity) were sequentially added to a custom-designed three-necked reactor, and the outlets were sealed using a Teflon stirring rod and rubber stoppers. The reactor was subsequently transferred to a 60 ℃ oil bath, and the Teflon stirring rod was connected to a mechanical stirrer. Stirring was initiated and continued until all reactants were dissolved in THF. The catalyst of DBTDL (0.5 wt% of the total reactants), chain extenders of 4-aminophenyl disulfide and 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol were sequentially added in the reactor. The molar ratio of NCO groups in IPDI to the total hydroxyl (OH) groups in HTPB, 4-aminophenyl disulfide and 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol was maintained at 1:1. The weight ratios of HTPB, 4-aminophenyl disulfide and 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol were set at 20/1/1, 20/1.5/1.5, 20/2/2 and 20/2.5/2.5, corresponding to the sample names SFPU-1 through SFPU-4, respectively. After reacting for 4 hours, 10 ml of methanol was injected into the reactor, and stirring was continued for an additional 10 minutes to terminate the polymerization. Finally, the reaction mixture was poured into methanol to precipitate the polyurethane, which was washed three times with methanol. The polymer was then dried in a vacuum oven at 80°C for 12 hours. 2) Fluorine-free polyurethane (SPU) The synthesis method follows that of SFPU. The difference lies in the removal of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol. The composition consists of HTPB, 4-aminophenyl disulfide and IPDI in a ratio of 20/2/2. 3) Polyurethane with little hard domains (SPU-NH) The synthesis method was based on our previous research and shares the same composition as SPU 40 . HTPB (10 g) and 4-aminophenyl disulfide (1 g) were sequentially added to a custom-designed three-necked reactor. DBTDL (0.5 wt% of the total reactants) and THF was then added to the reactor, and the outlets were sealed using a Teflon stirring rod and rubber stoppers. The reactor was subsequently transferred to an oil bath, and the Teflon stirring rod was connected to a mechanical stirrer. Stirring was initiated and continued until all reactants were dissolved in THF. The temperature of the oil bath was raised to 60 ℃, and IPDI was injected into the reactor using a syringe. The molar ratio of NCO groups in IPDI to the total hydroxyl (OH) groups in HTPB and 4-aminophenyl disulfide was maintained at 1:1. After reacting for 4 hours, 10 ml of methanol was injected into the reactor, and stirring was continued for an additional 10 minutes to terminate the polymerization. Finally, the reaction mixture was poured into methanol to precipitate the polymer, which was washed three times with methanol. The polymer was then dried in a vacuum oven at 80 ℃ for 12 hours. Sensing Materials Preparation 1) Self-healing piezo-ionotropic polymer (ShPiP) SFPUs were dissolved in DMF, followed by the addition of [BMIM][TFSI]. The mixture was stirred until a clear and homogeneous solution was obtained. The SFPUs and [BMIM][TFSI] were blended in mass ratios ranging from 90/10 to 10/90. The solution was then poured into a Teflon mold and allowed to dry at room temperature in a fume hood. Subsequently, the mold was placed on a heating plate at 80 ℃ and dried for 24 hours. 2) Pristine PU-based iongel (PU-iongel) The synthesis method follows that of ShPiP. The difference is that SFPU is replaced with SPU, and the mass ratio of SPU to [BMIM][TFSI] is 40/60. 3) PU-based iongel with little hard domains(PU-NH-iongel) The synthesis method follows that of ShPiP. The difference is that SFPU is replaced with SPU-NH, and the mass ratio of SPU-NH to [BMIM][TFSI] is 40/60. Preparation of piezo-ionotropic multi-resonance acoustic sensor (PiMAS) A mask with a specific interdigitated electrode pattern was placed in a Teflon mold, followed by spraying a silver nanowire solution using a spray coater (SRC-200 VT, E-FLEX Korea, nozzle: 0.05 mm, pressure: 200 mbar). After removing the mask, a specific SFPU/[BMIM][TFSI] solution was poured into the same Teflon mold and dried using the same method as for the ShPiP preparation. The thickness of the channels was controlled by the weight of SFPU/[BMIM][TFSI] solution poured into the mold. Channels measuring 100 µm to 800 µm were cut into sizes of 1 cm × 4 cm, arranged in order from thinnest to thickest, attached to a hollow rectangular support frame and wired accordingly. Characterization The chemical compositions of all chemicals and polyurethanes were verified using 1 H NMR spectroscopy conducted at 25°C on a Bruker AVIII400 NMR spectrometer, with tetramethylsilane (TMS) serving as an internal standard. The weight-average molecular weights (Mw) and molecular weight dispersity (MWD) were determined via gel permeation chromatography (GPC, Waters-2690) employing tetrahydrofuran (THF) as the mobile phase at 40℃. The mechanical properties of the polyurethanes were assessed at room temperature using a universal testing machine (UTM, Instron 5567) with dumbbell-shaped specimens, in accordance with ASTM D638–5 standards. This equipment was also utilized to mechanically stimulate sensors during gauge factor testing. Water contact angle (WCA) measurements were performed using a contact angle goniometer (OCA25, DataPhysics, Germany). X-ray diffraction (XRD) analyses were conducted using a Bruker D8 Advance diffractometer with Cu-Kα radiation (wavelength = 1.54060 Å). Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) absorption spectra were recorded on an iD5 ZnSe ATR instrument (Cary660, Agilent). Dynamic mechanical thermal analysis (DMTA) was executed using a DMA Q800 system from TA Instruments (USA), with measurements conducted at a heating and cooling rate of 3°C/min from − 120 to 100 ℃ in a liquid N 2 atmosphere, at a frequency of 1 Hz. Scratch recovery tests for self-healing experiments were carried out under an optical microscope (Olympus/BX 51TF Instec H601, Japan) in various time periods, under both ambient (20–40% relative humidity) and submerged conditions (DI water). Electrochemical impedance spectroscopy (EIS) was performed at room temperature using an electrochemical analyzer PGSTAT302N (Metrohm Autolab) within a frequency range of 0.1 Hz to 1 MHz, applying a 10 mV AC signal. For Raman intensity mapping, a Renishaw inVia Reflex confocal micro-Raman spectrometer was used to analyze the samples. Each sample was mounted on a custom-built stretching fixture to enable precise control during measurements. Raman scans were performed at predefined locations, covering an area of 50 µm × 50 µm, with a DC voltage of 1V applied throughout. Initial measurements were taken on unstretched samples, followed by scans after stretching the samples to a predetermined length. The confocal setup of the spectrometer allowed for high spatial resolution, enabling detailed mapping of Raman-active regions and revealing the molecular composition and structural characteristics of the samples under both conditions. The impedance spectra were analyzed using equivalent circuit models in NOVA software to evaluate the bulk resistance (R b ) of the devices, from which the ionic conductivity was calculated as σ = (l/R b × A), where σ is the ionic conductivity, l is the film thickness, and A is the electrode area. The morphology of AgNW was examined using a scanning electron microscope (SEM, Verios G4 UC, Thermo Scientific), which was also equipped with energy dispersive spectroscopy (EDS) to analyze element mass percentages. A precision LCR meter (Agilent Keysight Technologies, E4980A) was employed to measure the dielectric constant, capacitance, and impedance data of the sensing materials and sensors. The amplitude of individual channels in the sensors was measured using a laser vibrometer (HEPU, GC03-30A). Simulation and Calculation 1) Hydrophobicity simulation and calculation To study the hydrophobicity or hydrophilicity of the synthesized polyurethanes, we performed density-functional theory (DFT) calculations to compute water adsorption energy, and Ab-Initio Molecular Dynamics (AIMD) calculations to simulate the process of water adsorption for polyurethanes. DFT and AIMD calculations were carried out by using Vasp packages. All the systems were initially relaxed by density-functional theory with GGA-PBE. In the AIMD simulations, the systems in the presence of water molecular were equilibrated under the canonical ensemble (NVT) for 100 ps with 0.5 fs as time steps) at room temperature conditions (300 K). Average properties were then evaluated from the last simulation iteration. To obtain better statistics properties and structural properties, for each system two independent runs were simulated, with setting the molecular straight or zigzag. we added 80 water molecular [240 (160 H and 80 O) atoms totally] surrounding target molecular. The averaged initial distance between the target molecular was around 3 Å, this distance between these H 2 O and the target molecular were then fully relaxed in the process of DFT structural relaxations and AIMD simulations. 2) Binding energy simulation and calculation The theoretical calculations were performed via the Gaussian 16 suite of programs. The structures of the studied molecules (denoted by A, B2, and C) and the complexes of A-B2 and A-B2-C were fully optimized at the B3LYP-D3BJ/6–31 + G(d,p) level of theory. The vibrational frequencies of the optimized structures were carried out at the same level. The structures were characterized as a local energy minimum on the potential energy surface by verifying that all the vibrational frequencies were real. To avoid basis set superposition error (BSSE), counterpoise correction was applied to obtain the complexation energies between A and B in the A-B and A-B-C complexes at the B3LYP-D3BJ/6-311 + G(d,p) level of theory. Independent gradient model (IGM) analysis was derived by using the Multiwfn software. The Visual Molecular Dynamics (VMD) program was used to plot the color-filled isosurfaces graphs of IGM analytical results. The IGM method can visualize weak-interaction areas and their characteristics. Consequently, the initial binding energy of A and B 2 is -87.60 kcal/mol, which decreases to -81.04 kcal/mol upon the addition of C, indicating the presence of weak interactions between B2 and C in the complexes A-B2-C. Within this system, A corresponds to [TFSI], B2 to [BMIM], and C to a fluorine-containing chain extender. Declarations Data availability All data are included in this article and its Supplementary Information file. All data are available from the corresponding authors upon reasonable request. Acknowledg e ments This work was supported by the Brain Pool program, National R&D Program and Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (RS-2024-00405818, 2022M3H4A1A02076825, 2022M3C1A3081211, 2021M3H4A1A03049075, 2020R1A2C3014237). Author contributions J.Z. and D.H.K. supervised the project. D.H.K., J.Z., W.B.Y. and J.S.K. developed the theoretical concepts and designed the experiments. W.B.Y., J.S.K. and Z.K. carried out all the experiments, while W.B.Y., J.S.K., Z.K. and Z.Y. conducted the material characterization studies. E.K.B., F.L., C.C. and Y.T. provided assistance with experimental procedures. D.H.K., J.Z. and J.Y.L. reviewed and provided feedback on the manuscript. W.B.Y., J.S.K., and D.H.K. wrote the manuscript, with D.H.K. responsible for revisions. All authors discussed the results and contributed to the final manuscript. Competing interests The authors declare that they have no competing interests. Additional information Supplementary Information is available for this paper at www.nature.com/reprints. Correspondence and requests for materials should be addressed to Jin Zhu or Do Hwan Kim. References Bermingham-McDonogh O, Reh TA (2011) Regulated Reprogramming in the Regeneration of Sensory Receptor Cells. Neuron 71:389–405 Zhao C, Park J, Root SE, Bao Z (2024) Skin-inspired soft bioelectronic materials, devices and systems. Nat Rev Bioeng 2:671–690 Luo Y et al (2023) Technology Roadmap for Flexible Sensors. ACS Nano 17:5211–5295 Marshall KL et al (2016) Touch Receptors Undergo Rapid Remodeling in Healthy Skin. 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Nat Commun 13:7699 Sillero E et al (2009) Static and dynamic determination of the mechanical properties of nanocrystalline diamond micromachined structures. J Micromech Microeng 19:115016 Miles RN (2024) Physical Approach to Engineering Acoustics 53–82. Springer International Publishing, Cham Kojio K, Nozaki S, Takahara A, Yamasaki S (2020) Influence of chemical structure of hard segments on physical properties of polyurethane elastomers: a review. J Polym Res 27:1–13 Sakurai S et al (2009) Ultra small-angle X-ray scattering studies on structural changes in micrometers upon uniaxial stretching of segmented polyurethaneureas. Polymer 50:1566–1576 Dobashi Y et al (2022) Piezoionic mechanoreceptors: Force-induced current generation in hydrogels. Science 376:502–507 Lee JI et al (2021) Visco-Poroelastic Electrochemiluminescence Skin with Piezo-Ionic Effect. Adv Mater 33:2100321 Jin ML et al (2017) An Ultrasensitive, Visco-Poroelastic Artificial Mechanotransducer Skin Inspired by Piezo2 Protein in Mammalian Merkel Cells. Adv Mater 29:1605973 Son D et al (2018) An integrated self-healable electronic skin system fabricated via dynamic reconstruction of a nanostructured conducting network. Nat Nanotechnol 13:1057–1065 Ying WB et al (2020) Waterproof, Highly Tough, and Fast Self-Healing Polyurethane for Durable Electronic Skin. ACS Appl Mater Interfaces 12:11072–11083 Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryInformationDoHwanKim.docx Supplementary Information MovieS1SFPUselfhealing.mp4 Supplementary Movie 1 MovieS2ShPiPSelfhealing.mp4 Supplementary Movie 2 MovieS3AgNWpassiveselfhealing.mp4 Supplementary Movie 3 MovieS4Songsensing.mp4 Supplementary Movie 4 Cite Share Download PDF Status: Published Journal Publication published 02 Sep, 2025 Read the published version in Nature Communications → 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. 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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-5810151","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":405328394,"identity":"77408628-8204-4251-92b7-5131a0564451","order_by":0,"name":"Do Hwan Kim","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8klEQVRIie3RsWrDMBCA4Qsq7uIkq0So8woyBi/Nw1iLvMiZO7TBEFCW5F28td2UCJzFJatKMndKoNCpQ0s1ZpKdrRD943EfHByAz/cfMwGo3u8komcz1E4g4MllBCDYsKozGewl25hQ5c+3bzX+fnmC4UKh5MFByKFWWuBD8bqccrJqtoCbDLHGQajJSy3oR1EpkeK+rO2pgNZlK8l0TnfHlPxYMm4n3B6mdEaNSEd9+WgngJiLEMMzXZQ8rswxub+TKowbNo9dZGB48lWUkzHdifj9JGdRtNWauMh5NxhAhwC9rsB+8BNg1nnb5/P5rqc/rFdYBGH4VDoAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0003-3003-8125","institution":"Hanyang University","correspondingAuthor":true,"prefix":"","firstName":"Do","middleName":"Hwan","lastName":"Kim","suffix":""},{"id":405328395,"identity":"d74aa6b8-3201-4304-9b9b-478bf955fa7e","order_by":1,"name":"Wu Bin Ying","email":"","orcid":"https://orcid.org/0000-0002-8768-7428","institution":"KAIST","correspondingAuthor":false,"prefix":"","firstName":"Wu","middleName":"Bin","lastName":"Ying","suffix":""},{"id":405328396,"identity":"7d40bc63-5bc5-443d-9007-bd1e8d1bd203","order_by":2,"name":"Joo Sung Kim","email":"","orcid":"","institution":"Hanyang University","correspondingAuthor":false,"prefix":"","firstName":"Joo","middleName":"Sung","lastName":"Kim","suffix":""},{"id":405328397,"identity":"924c720c-5185-4136-923e-f0f1497a89e9","order_by":3,"name":"zhe YU","email":"","orcid":"https://orcid.org/0009-0002-8628-7243","institution":"East China Normal University","correspondingAuthor":false,"prefix":"","firstName":"zhe","middleName":"","lastName":"YU","suffix":""},{"id":405328398,"identity":"164ea71b-2007-42ec-8bb7-936d65d5ffc4","order_by":4,"name":"Zhengyang Kong","email":"","orcid":"","institution":"Hanyang University","correspondingAuthor":false,"prefix":"","firstName":"Zhengyang","middleName":"","lastName":"Kong","suffix":""},{"id":405328399,"identity":"a3b10924-8317-4cb9-ae89-42488dfdcf5d","order_by":5,"name":"Elvis K. Boahen","email":"","orcid":"https://orcid.org/0009-0002-8784-243X","institution":"Hanyang University","correspondingAuthor":false,"prefix":"","firstName":"Elvis","middleName":"K.","lastName":"Boahen","suffix":""},{"id":405328400,"identity":"4a3a5518-64bd-41d6-85a1-edc544f3b120","order_by":6,"name":"Fenglong Li","email":"","orcid":"","institution":"Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Fenglong","middleName":"","lastName":"Li","suffix":""},{"id":405328401,"identity":"1c4fa0b1-b4be-427e-89fe-b09af77b8b07","order_by":7,"name":"Chao Chen","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Chao","middleName":"","lastName":"Chen","suffix":""},{"id":405328402,"identity":"f4c9416d-608d-4c70-83e3-1aca5e8e5318","order_by":8,"name":"Ying Tian","email":"","orcid":"","institution":"Sungkyunkwan University","correspondingAuthor":false,"prefix":"","firstName":"Ying","middleName":"","lastName":"Tian","suffix":""},{"id":405328403,"identity":"1b95aa49-fa7f-44b8-9c11-df908c5f1f7e","order_by":9,"name":"Hanbin Choi","email":"","orcid":"","institution":"Hanyang University","correspondingAuthor":false,"prefix":"","firstName":"Hanbin","middleName":"","lastName":"Choi","suffix":""},{"id":405328404,"identity":"8a23c28d-5d51-44c8-a8f7-0da302a41102","order_by":10,"name":"Jung-Yong Lee","email":"","orcid":"https://orcid.org/0000-0002-5347-8230","institution":"Korea Advanced Institute of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Jung-Yong","middleName":"","lastName":"Lee","suffix":""},{"id":405328405,"identity":"a174aa2f-1d28-44e1-9a2a-5a92680652b3","order_by":11,"name":"Jin Zhu","email":"","orcid":"","institution":"Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Jin","middleName":"","lastName":"Zhu","suffix":""}],"badges":[],"createdAt":"2025-01-11 15:20:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5810151/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5810151/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41467-025-63643-4","type":"published","date":"2025-09-02T04:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":75445233,"identity":"43fe2c62-a4d3-43a8-b799-21ac1302dc1e","added_by":"auto","created_at":"2025-02-04 16:26:25","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1567465,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eConceptual design of the PiMAS inspired by the basilar membrane in the biological auditory system.\u003c/strong\u003e \u003cstrong\u003ea,\u003c/strong\u003e Schematic representation of a biological basilar membrane in both coiled and uncoiled states. \u003cstrong\u003eb,\u003c/strong\u003e Response mechanism of the basilar membrane to sound and characterization of its non-regenerative properties. \u003cstrong\u003ec,\u003c/strong\u003e Schematic illustration of PiMAS, mimicking the topology and sensing capabilities of the basilar membrane. \u003cstrong\u003ed,\u003c/strong\u003e Schematic of the ShPiP components: SFPU and [BMIM]⁺[TFSI]⁻, along with the Independent Gradient Model (IGM) analysis between them. \u003cstrong\u003ee, \u003c/strong\u003eSensing mechanism of the PiMAS and its self-healing capability, aimed at preventing sensorineural hearing loss (SNHL).\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5810151/v1/9f8a696e844d12a5765fd17e.jpg"},{"id":75445238,"identity":"c8d09518-4c3e-4e61-a002-be356907a7bf","added_by":"auto","created_at":"2025-02-04 16:26:25","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":2330294,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDiscrimination ability of the PiMAS for sound frequency and sound pressure.\u003c/strong\u003e \u003cstrong\u003ea,\u003c/strong\u003e Response of the PiMAS to sound stimuli, demonstrating vibration characteristics based on different channel thicknesses, which lead to varying resonance frequencies and amplitudes. \u003cstrong\u003eb,\u003c/strong\u003e SEM images of AgNW on the channel, showing their distribution across the channel's surface.\u003cbr\u003e\n \u003cstrong\u003ec,\u003c/strong\u003e Variations in impedance and amplitude for channel 1 in response to frequency changes, both exhibiting similar trends. \u003cstrong\u003ed,\u003c/strong\u003e Impedance response curve of channel 1 to sound pressure, indicating a positive correlation. The inset illustrates the relationship between impedance change and sound pressure sensitivity. \u003cstrong\u003ee,\u003c/strong\u003e Impedance and amplitude responses of channels 1-8 to sound stimuli, with the upper figure correlating frequency changes to impedance and the lower figure correlating frequency changes to amplitude. \u003cstrong\u003ef,\u003c/strong\u003e Impedance curves of channels 1-8 as they change with increasing sound pressure. \u003cstrong\u003eg,\u003c/strong\u003e Impedance curves of channels 1-8 as they vary with strain induced by sound pressure, along with their sensitivity to strain. The inset explains how strain induced by sound pressure is calculated.\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5810151/v1/60a2ca25b53547b617ecb0b0.jpg"},{"id":75445664,"identity":"e12229e5-e9af-478d-8c49-2204e6c9f3bf","added_by":"auto","created_at":"2025-02-04 16:34:25","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1810947,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eInvestigation of ion flux pathways inside the PiMAS.\u003c/strong\u003e \u003cstrong\u003ea and b, \u003c/strong\u003eMicro-Raman spectroscopy maps showing the cation intensity distribution in PU-iongel and ShPiP in both original and stretched states (with regions labeled as 1#-anode, 2#-intermediate, and 3#-cathode). \u003cstrong\u003ec,\u003c/strong\u003e Illustration of the ion hitching-in cage effect in the hard domains before and after stretching, depicting its role in capturing cations. \u003cstrong\u003ed,\u003c/strong\u003eComparison of cation escape probability in PU-iongel and ShPiP, highlighting the enhanced capture due to the ion hitching-in cage effect.\u003c/p\u003e","description":"","filename":"Figure3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5810151/v1/2bd39bdc3e61e9ccd65bb209.jpg"},{"id":75445239,"identity":"d85b3b49-c419-46f8-aa46-c848f7f4935a","added_by":"auto","created_at":"2025-02-04 16:26:25","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2260893,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSelf-healing mechanism, demonstration and performance of the PiMAS.\u003c/strong\u003e \u003cstrong\u003ea,\u003c/strong\u003eDensity Functional Theory (DFT) and Ab Initio Molecular Dynamics (AIMD) calculations reveal that the separation distance between SFPU and water molecules exceeds 3 Å. \u003cstrong\u003eb,\u003c/strong\u003e Radial distribution curve reveals that internal hydrogen bonds within SFPU average approximately 3 Å in length, with minimal hydrogen bonding between SFPU and water molecules. \u003cstrong\u003ec,\u003c/strong\u003e Demonstration of self-healing in an artificial lymph fluid environment for a sensing channel. \u003cstrong\u003ed,\u003c/strong\u003eObservation of the self-healing process in a channel under an optical microscope: (Top) The AgNWs functioning as electrodes undergo \"passive\" self-healing in tandem with ShPiP, eventually restoring electrical connectivity. (Bottom) As the channel completes the repair process, its sensitivity to sound progressively returns to baseline levels. \u003cstrong\u003ee and f, \u003c/strong\u003eResponse curves of channel-1 to various sound frequencies and sound pressure levels before and after self-healing, showing nearly identical performance and stable sensitivity. \u003cstrong\u003eg,\u003c/strong\u003eComparison of PiMAS with other iontronic and non-iontronic sensors in terms of pressure sensitivity, stretch sensitivity (gauge factor), and self-healing capability, underscoring its superior performance across these metrics.\u003c/p\u003e","description":"","filename":"Figure4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5810151/v1/d73c595248bf4f25d98b40b5.jpg"},{"id":75445669,"identity":"fd27f0dd-2007-44a1-b87e-0cdbf4ab1f71","added_by":"auto","created_at":"2025-02-04 16:34:25","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":2342695,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eApplication of the PiMAS in recognizing real-world sounds.\u003c/strong\u003e \u003cstrong\u003ea, \u003c/strong\u003eVariations in vocal cord length and thickness result in differing frequencies between male and female voices. \u003cstrong\u003eb,\u003c/strong\u003e Impedance response of PiMAS to three males and three females saying \"Hello, sensor,\" with frequency analysis via Fourier transformation. The ordinate represents the value of ∆Z/Z₀. \u003cstrong\u003ec,\u003c/strong\u003e Characteristic frequencies of six piano keys, covering the entire detectable frequency range of the sensor. \u003cstrong\u003ed,\u003c/strong\u003e Frequency response of PiMAS to six piano keys, with frequency-impedance spectra (1st and 3rd rows) and time-frequency-impedance mapping (2nd and 4th rows), showing sensitive and continuous detection of all frequencies for each piano key. Both the ordinate and intensity of the mapping represent the value of ∆Z/Z₀. \u003cstrong\u003ee,\u003c/strong\u003e Photographic documentation of PiMAS in practical sound detection tests. \u003cstrong\u003ef,\u003c/strong\u003e Comparison of PiMAS response curves to those of a commercial sound sensor for vocal performances by a Bass (\"Doubt\"), Baritone (\"Marechiare\"), and Tenor (\"Nessun dorma\").\u003c/p\u003e","description":"","filename":"Figure5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5810151/v1/c0c4eaed80a766232195398e.jpg"},{"id":90476108,"identity":"839bb847-a193-4746-bc6f-6460b6eefb4e","added_by":"auto","created_at":"2025-09-03 07:07:17","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":11396136,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5810151/v1/827c7e6a-7e5c-43b8-92fa-fa92c256cf56.pdf"},{"id":75445244,"identity":"aab1a324-06c8-4803-8ffb-1ee7fec09b2f","added_by":"auto","created_at":"2025-02-04 16:26:25","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":6323452,"visible":true,"origin":"","legend":"Supplementary Information","description":"","filename":"SupplementaryInformationDoHwanKim.docx","url":"https://assets-eu.researchsquare.com/files/rs-5810151/v1/dcd9b6ee54a1e7ca5d3e55b1.docx"},{"id":75445236,"identity":"a5c71c20-0566-46a5-9fee-4c94cbfddecb","added_by":"auto","created_at":"2025-02-04 16:26:25","extension":"mp4","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":7496102,"visible":true,"origin":"","legend":"\u003cp\u003eSupplementary Movie 1\u003c/p\u003e","description":"","filename":"MovieS1SFPUselfhealing.mp4","url":"https://assets-eu.researchsquare.com/files/rs-5810151/v1/00f3c3ee797bfbaac14a66f8.mp4"},{"id":75445251,"identity":"caaaa824-21b0-415a-bedb-eaa78ce6edca","added_by":"auto","created_at":"2025-02-04 16:26:25","extension":"mp4","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":12346606,"visible":true,"origin":"","legend":"\u003cp\u003eSupplementary Movie 2\u003c/p\u003e","description":"","filename":"MovieS2ShPiPSelfhealing.mp4","url":"https://assets-eu.researchsquare.com/files/rs-5810151/v1/7b688ed0086025292c78f84c.mp4"},{"id":75445229,"identity":"33ecd94a-b516-4a36-b94a-0aeac49391b0","added_by":"auto","created_at":"2025-02-04 16:26:24","extension":"mp4","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":2598968,"visible":true,"origin":"","legend":"\u003cp\u003eSupplementary Movie 3\u003c/p\u003e","description":"","filename":"MovieS3AgNWpassiveselfhealing.mp4","url":"https://assets-eu.researchsquare.com/files/rs-5810151/v1/de133a714a5ec845ac635df8.mp4"},{"id":75445267,"identity":"03d07f9a-8dab-4a61-be98-039f471030f9","added_by":"auto","created_at":"2025-02-04 16:26:26","extension":"mp4","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":47983306,"visible":true,"origin":"","legend":"Supplementary Movie 4","description":"","filename":"MovieS4Songsensing.mp4","url":"https://assets-eu.researchsquare.com/files/rs-5810151/v1/70776904c7e9db532e4cdc69.mp4"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"\u003cp\u003eA Reconfigurable Piezo-Ionotropic Polymer Membrane for Sustainable Multi-Resonance Acoustic Sensing\u003c/p\u003e","fulltext":[{"header":"Main","content":"\u003cp\u003eHuman sensory tissues are constantly exposed to the external environment that facilitates the effective capture of necessary physical inputs (e.g., touch, sound, heat, light, and chemicals) for sensory function\u003csup\u003e\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. However, prolonged overstimulation and exposure to physical hazards can lead to damage to sensory receptors. To protect the uniform distribution and function of these receptors from damage, sensory tissues directly exposed to the environment, including the epidermis, olfactory epithelium and gustatory cells, undergo continuous regeneration after injury\u003csup\u003e\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. In contrast, hair cells and the basilar membranes in the auditory system exhibit an extremely limited regenerative capacity in mammals\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. Moreover, the intricate structure of hair cells makes them particularly susceptible to damage from aging or disease, leading to irreversible sensorineural hearing loss (SNHL), the most prevalent form of sensory impairment in humans\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eCurrently, cochlear implants are the primary therapeutic option for SNHL. However, these devices require invasive surgical procedures that substitute the natural auditory system, posing significant risks, including tissue necrosis, facial paralysis and meningitis, as well as significant financial burdens for patients\u003csup\u003e\u003cspan additionalcitationids=\"CR12\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. Addressing the underlying cause of SNHL could revolutionize treatment strategies. Since SNHL primarily results from damage to hair cells on the basilar membrane while other auditory tissues remain intact, the development of an artificial basilar membrane could substantially reduce the scope and complexity of necessary surgical interventions.\u003c/p\u003e \u003cp\u003eTo meet the requirements for constructing an artificial basilar membrane, multi-resonant acoustic sensors have been developed by mimicking the biological auditory system based on piezoelectric\u003csup\u003e\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e, triboelectric\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e,\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e, capacitive\u003csup\u003e\u003cspan additionalcitationids=\"CR20\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e and resistive materials\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e, achieving the required sensitivity. Despite these advances, a significant challenge remains due to the use of rigid materials in these sensors, which are prone to cracking under prolonged acoustic vibrations and could potentially cause SNHL anew. Additionally, the mechanical mismatch between the rigid electronic components and the soft biological tissues frequently leads to tissue damage\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e,\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. More importantly, conventional electronic conduction-driven sensors, unlike the ionic conduction in biological systems, can induce redox reactions that result in corrosion and gas evolution when exposed to wet environments (e.g., biofluid) during operation\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. To address these mechanical and electrochemical mismatches, an ideal design for an artificial basilar membrane would use entirely soft materials that mimic the ionotropic mechanotransduction mechanisms observed in biological sensory systems. Furthermore, considering the non-regenerative properties of hair cells and the high water content (98\u0026ndash;99%) of the lymph fluid in the inner ear\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e, it is crucial that the artificial basilar membrane possesses self-healing capability in humid environments, ensuring its durability and functionality for in vivo implantability.\u003c/p\u003e \u003cp\u003eHere, inspired by the ionotropic mechanotransduction mechanism and structural features of the basilar membrane in the human auditory system, we report a reconfigurable piezo-ionotropic polymer membrane engineered for biomimetic, sustainable, multi-resonance acoustic sensing, offering exceptional sensitivity and frequency discrimination while being immune to \u0026ldquo;dying.\u0026rdquo; To achieve this, hydrophobic fluorine groups were initially incorporated into the polyurethane molecular chain along with units of high electronegativity and dynamic covalent bonds in the hard segments, resulting in underwater self-healing properties. Subsequently, ionic liquid ([BMIM]\u003csup\u003e+\u003c/sup\u003e[TFSI]\u003csup\u003e-\u003c/sup\u003e) was employed as an ion donor and combined with self-healable fluorinated polyurethane (SFPU) to develop the self-healing piezo-ionotropic polymer (ShPiP), the key sensing material in the piezo-ionotropic multi-resonance acoustic sensor (PiMAS). PiMAS demonstrates significant advancements in both sensitivity and frequency discrimination. The ion hitching-in cage effect, enabled by the dynamic reconfiguration of polymer networks, efficiently regulates ion flux under acoustic pressure, thereby enhancing PiMAS\u0026rsquo;s acoustic sensitivity. Acoustic pressure causes the polymer chains in ShPiP to stretch, creating interstitial passages between hard segments-akin to unlocking a sealed cage. This ion hitching-in cage mechanism, combined with reversible ion-dipole interactions from the highly electronegative fluorine groups within the hard segments, enables cations to access the unlocked cage structure, effectively hitching ions and increasing impedance. As a result, PiMAS can accurately identify sound frequencies from 20 to 3200 Hz, particularly within the human speech frequency range (men: 64\u0026ndash;523 Hz; women: 160\u0026ndash;1200 Hz), demonstrating high sensitivity to both sound pressure and strain. Furthermore, the dynamic and reconfigurable properties of ShPiP enable PiMAS to maintain its waterproof and self-healing capabilities across diverse environments, including air, water, and even lymphatic fluids, offering substantial potential for preventing sensorineural hearing loss (SNHL).\u003c/p\u003e\n\u003ch3\u003eDesign of piezo-ionotropic multi-resonance acoustic sensor\u003c/h3\u003e\n\u003cp\u003eSound transmission in the human auditory system involves several stages: vibration of the tympanic membrane, conduction through the ossicles, and generation of pressure waves within the cochlea, which displace the basilar membrane (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea)\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. The basilar membrane plays a critical role in auditory perception, varying in width and stiffness along its length to decompose complex acoustic signals into their constituent frequencies. This frequency decomposition is essential for the next stage of auditory perception, where ionotropic mechanotransduction occurs in hair cells located on the basilar membrane. Vibrations of the basilar membrane cause the bending of cilia on these hair cells, which stretches the tip links and activates ion channels (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). This sequence allows cations to enter the hair cells, generating the receptor potential necessary for sound detection. Despite the efficiency of this mechanism, hair cells are extremely delicate, and because they cannot regenerate, any damage leads to irreversible sensorineural hearing loss (SNHL) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb, rightmost).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eInspired by this human ionotropic mechanotransduction mechanism and the structural features of basilar membranes, we have developed a sustainable PiMAS, comprising eight channels, each formed by ShPiP and AgNWs interdigitated electrodes. These channels, with thicknesses ranging from 100 to 700 \u0026micro;m, effectively detect sounds in the 20\u0026ndash;3300 Hz range, covering almost the entire conventional sound frequency range of 20\u0026ndash;4000 Hz (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). ShPiP, the key material for sensing functionality, consists of SFPU and ionic liquid ([BMIM]\u003csup\u003e+\u003c/sup\u003e[TFSI]\u003csup\u003e-\u003c/sup\u003e). The structure of SFPUs features hard segments introduced by dynamic disulfide bonds and fluorine groups, with varying soft/hard segment ratios (Z\u0026thinsp;=\u0026thinsp;0.6\u0026ndash;0.78) and similar molecular weights (6.9\u0026ndash;7.1 \u0026times; 10\u003csup\u003e4\u003c/sup\u003e g/mol) as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed. Their synthesis steps, structural characterization and analysis of mechanical properties were detailed in the Supporting Information (Supplementary Figs.\u0026nbsp;1\u0026ndash;4, Supplementary Note 1, and Supplementary Tables\u0026nbsp;1, 2). A series of ShPiPs were prepared by blending a certain proportion of [BMIM]\u003csup\u003e+\u003c/sup\u003e[TFSI]\u003csup\u003e-\u003c/sup\u003e with SFPUs (Supplementary Figs.\u0026nbsp;5\u0026ndash;9 and Supplementary Note 2). Independent gradient model (IGM) analysis revealed that the initial binding energy between [BMIM]\u003csup\u003e+\u003c/sup\u003e and [TFSI]\u003csup\u003e-\u003c/sup\u003e was \u0026minus;\u0026thinsp;87.60 kcal/mol (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed, right). Attraction between the fluorine group and [BMIM]\u003csup\u003e+\u003c/sup\u003e reduced the binding energy between [BMIM]\u003csup\u003e+\u003c/sup\u003e and [TFSI]\u003csup\u003e-\u003c/sup\u003e to -81.04 kcal/mol, indicating that the fluorine group in SFPU acts as an ion-hitching site, capable of forming ion-dipole interactions with [BMIM]\u003csup\u003e+ 29,30\u003c/sup\u003e. Subsequently, we validated the aforementioned calculations by characterizing the asymmetric stretching bands of S\u0026thinsp;=\u0026thinsp;O and N-S of [TFSI]\u003csup\u003e-\u003c/sup\u003e in ShPiP, as well as the associated and free carbonyl groups, using infrared spectroscopy (detailed description in Supplementary Fig.\u0026nbsp;10a, b and Supplementary Note 2). X-ray diffraction (XRD) spectra result further supported these analyses (detailed description in Supplementary Fig.\u0026nbsp;10c, d)\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eUnder the influence of ion-dipole interactions, PiMAS will possess a perceptual mechanism and high sensitivity akin to that of the basilar membrane (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee). In its quiescent state, the hard segments of the SFPU are associated through dipole-dipole interactions among fluorine groups and hydrogen-bonding, forming a closed hard domain where ions maintain a dynamic equilibrium both inside and outside. When sound vibrations bend PiMAS channels, the resulting stretch causes the associated hard segments of the ShPiP to separate, creating interstitial passages within the hard domains where ions are captured under the effect of ion-dipole interactions. This process further restricts the ions and accentuates the impedance increase induced by stretching, thereby enhancing sensitivity. In addition, to overcome the limitations of non-regenerative hair cells and SNHL, the acoustic sensor is designed to possess self-healing capabilities in conventional environments, water and lymphatic fluid. This self-healing capability is driven by the synergistic effects of dynamic disulfide bond exchange, dipole-dipole interactions among fluorine groups and the enhanced chain mobility due to the plasticizing effect of the ionic liquid (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee rightmost). Additionally, the strong hydrophobic properties conferred by the polybutadiene structure and fluorine groups within the ShPiP, coupled with the weak miscibility of [BMIM]\u003csup\u003e+\u003c/sup\u003e[TFSI]\u003csup\u003e-\u003c/sup\u003e with water, ensure that these driving forces remain unaffected by water molecules, facilitating underwater self-healing capabilities.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eDiscrimination ability of the PiMAS for sound frequency and sound pressure\u003c/h2\u003e \u003cp\u003eWe first assessed the resolution of the PiMAS with respect to sound pressure and frequency. The PiMAS was positioned between a speaker and a laser vibrometer and concurrently connected to an LCR meter for synchronous monitoring of impedance and amplitude changes (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). The distribution of ShPiP and AgNW interdigitated electrodes within each channel of the PiMAS is depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb, with the fabrication method detailed in Supplementary Fig.\u0026nbsp;11. When sound vibrations induce deformation in the channel, the impedance changed because of variations in ion flux within the ShPiP. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec, Channel 1 exhibited its maximum response impedance at 110 Hz and its maximum sound response limit at 805 Hz; similarly, it demonstrated its maximum amplitude at 106 Hz, the peak resonant frequency. Beyond 803 Hz, the amplitude of Channel 1 remained unchanged. A comparison of the impedance and amplitude profiles revealed a close correspondence in their characteristic response frequencies to acoustic stimuli. This indicated that the impedance signals originated from the channel vibrations and that PiMAS successfully converted mechanical sound stimuli into electrical signals, mimicking the function of the human basilar membrane.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSubsequently, to verify whether these electrical signal changes originated from impedance alterations in the AgNW electrodes during vibration, a dedicated sound frequency scan ranging from 20 Hz to 4000 Hz was performed on the AgNW electrodes alone (Supplementary Fig.\u0026nbsp;12 and Supplementary Note 3). The AgNW electrodes demonstrated remarkably stable impedance throughout the test due to their inherent stretchability, confirming that the conversion of mechanical sound stimuli into electrical signals was primarily facilitated by the ShPiP. Furthermore, we tested the sensitivity of Channel 1 at its maximum resonant frequency by varying the sound pressure (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed). As the sound pressure gradually increased from 65 dB to 91 dB, the response impedance also increased correspondingly, yielding a sensitivity of 530 kPa\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e (inset in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed).\u003c/p\u003e \u003cp\u003eThe responses of channels 1\u0026ndash;8 in PiMAS to acoustic sources in terms of impedance signals and amplitude have been aggregated in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee and Supplementary Fig.\u0026nbsp;13. The trends in impedance and amplitude responses were consistent across all channels. Moreover, as the thickness of the channels increased, their maximum response frequencies shifted from approximately 110 Hz to 680 Hz, and the upper limits of their response frequencies extended from around 800 Hz to 3300 Hz (Supplementary Fig.\u0026nbsp;14). This indicates a gradual shift in their response frequencies from the low to high frequency regions, consistent with the response characteristics of the basilar membrane to sound and conforming to the resonant frequency formula defined in Eq.\u0026nbsp;1\u003csup\u003e32\u003c/sup\u003e:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:{f}_{R}\\:\\propto\\:\\:t/{l}^{2}\\bullet\\:\\sqrt{E/\\rho\\:}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e, where \u003cem\u003ef\u003c/em\u003e\u003csub\u003e\u003cem\u003eR\u003c/em\u003e\u003c/sub\u003e represented the resonant frequency, \u003cem\u003et\u003c/em\u003e and \u003cem\u003el\u003c/em\u003e denoted the thickness and length of the ShPiP, \u003cem\u003eE\u003c/em\u003e and \u003cem\u003eρ\u003c/em\u003e signified the elastic modulus and density, respectively. The sound pressure sensitivity of channels 1\u0026ndash;8 at their maximum resonant frequencies was summarized in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef. An increase in thickness resulted in a slight decrease in sensitivity, as the channel thickness influenced its deformation magnitude under same sound pressure according to Newton\u0026rsquo;s second law\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. Nevertheless, all channels exhibited sufficiently high-pressure sensitivity (350\u0026ndash;530 kPa\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e). As sound vibration induced elongation in the channels, we also calculated the gauge factor (GF) for these channels, summarized in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eg and Supplementary Fig.\u0026nbsp;15. Similar to sound pressure sensitivity, the tensile sensitivity decreased slightly with increasing channel thickness, yet all channels demonstrated sufficiently high tensile sensitivity (49.2\u0026ndash;53.6).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSensing mechanism of PiMAS under acoustically induced vibration\u003c/h3\u003e\n\u003cp\u003eThe exceptional sensitivity of the PiMAS is attributed to the inherent ionotropic mechanotransduction mechanism, termed the ion hitching-in cage effect. The driving force for ion flux stemmed from the stretching induced by acoustic pressure. Such tensile stress separates the hard domains of the SFPU and increases their d-spacing\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e,\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e, enabling ion-dipole interactions between [BMIM]\u003csup\u003e+\u003c/sup\u003e[TFSI]\u003csup\u003e-\u003c/sup\u003e and fluorine groups of hard segments. Simultaneously, an external electric field prompts the migration of ions towards the electrodes. Consequently, the total ion flux driven by tensile stress is governed by the competitive relationship between the strength of ion-dipole interactions and electric field-induced ion migration. To explore this complex ion flux pathway, we utilized in-situ Raman spectroscopy for ionic intensity mapping at three distinct locations in the ShPiP samples: adjacent to the anode (Position-1#), intermediate (Position-2#), and adjacent to the cathode (Position-3#). The testing and data analysis methods are shown in Supplementary Fig.\u0026nbsp;16 and described in Supplementary Note 4. Additionally, we prepared a variant of pristine PU-based iongel (PU-iongel) without fluorine in the hard segments of self-healing polyurethane (SPU), while maintaining the same other components for comparative analysis of ion-dipole interactions. The color scale represented the intensity ratio of cations ([BMIM]\u003csup\u003e+\u003c/sup\u003e) to polyurethane, with deeper red indicating higher cation concentration. In fluorine-free PU-iongel, the flux of cations towards the right was clearly observable at all positions under tensile stress (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). At Position-1#, cations repelled by the anode moved further away; at Position-2#, the ion flux towards the cathode was more pronounced; at Position-3#, cations accumulated near the cathode. This flux behavior is typical of fluidic ions driven by the electric field direction towards the cathode and the piezoionic effect\u003csup\u003e\u003cspan additionalcitationids=\"CR37\" citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e, which is caused by tensile stress-induced compression perpendicular to the direction of stretch. For ShPiP containing fluorine in the hard segments, only minimal flux of cations was observed at all positions after stretching (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb). Specifically, at Position-1#, cations repelled from the left anode were biased towards the right with a distribution that remained nearly unchanged post-stretching. At Position-2#, cations were uniformly distributed across the region due to equal distance from both electrodes, with slight aggregation on the upper side possibly due to longitudinal compression of the polymer chains, while maintaining a uniform lateral distribution. At Position-3#, cations attracted to the right cathode were biased towards the right with a distribution that remained nearly unchanged post-stretching. Regarding the anions ([TFSI]\u003csup\u003e-\u003c/sup\u003e) in both ShPiP and PU-iongel, freed from polymer chain constraints (Supplementary Fig.\u0026nbsp;17,18 and Supplementary Note 4), they migrated leftwards under longitudinal compression and electric field drive. A comparison of the overlapped areas of anion movement before and after stretching revealed only slightly less ion flux in ShPiP than in PU-iongel (Supplementary Fig.\u0026nbsp;19). This indicates that the negatively charged fluorine groups in SFPU strongly bound [BMIM]\u003csup\u003e+\u003c/sup\u003e through ion-dipole interactions but form relatively weak ion-dipole bonds with [TFSI]\u003csup\u003e-\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn the ion flux process, the hard domains containing fluorine groups functioned like a closed cage (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec). Acoustic pressure-induced stretching could form interstitial passages in these domains, creating ion-accessible pathways similar to an open cage. In the PU-iongel (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed top), cations were captured but could escape after multiple interactions due to weaker ion-dipole interactions. This resulted in only slight reductions in cation mobility. In contrast, in ShPiP (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed bottom), stronger ion-dipole interactions between the fluorine groups and [BMIM]\u003csup\u003e+\u003c/sup\u003e restricted cation mobility more effectively, leading to greater impedance changes and enhanced sensitivity. A comparison of strain-impedance curves (Supplementary Fig.\u0026nbsp;20a) indicated that the ion hitching-in cage effect in ShPiP resulted in higher stretch sensitivity than in PU-iongel. In the PU-NH-iongel variant with fewer hard domains, based on SPU-NH (Supplementary Fig.\u0026nbsp;20b\u0026ndash;c and Supplementary Note 4), the ion hitching-in cage effect was minimal, resulting in reduced sensitivity. The ion hitching-in cage effect in ShPiP was also found to be reversible; IR spectroscopy and fatigue resistance tests confirmed that the hard domains opened with strain but returned to their original state upon release, maintaining stable impedance changes even after repeated stretching (Supplementary Fig.\u0026nbsp;21, 22).\u003c/p\u003e\n\u003ch3\u003eSelf-healing mechanism, demonstration and performance of the PiMAS\u003c/h3\u003e\n\u003cp\u003eTo address the limitations of non-regenerative hair cells and issues associated with SNHL, we recognized the need for acoustic sensors with self-healing capabilities in conventional environments, underwater, and even in lymphatic fluid. We achieved these objectives through the molecular design of ShPiP. Specifically, polybutadiene was selected as the soft segment to enhance the overall hydrophobicity of the polyurethane, followed by the introduction of fluorine groups into the hard segments to further increase hydrophobicity. Additionally, disulfide bonds were incorporated into the hard segments to impart self-healing capability to the resulting polyurethanes. Due to the dipole-dipole interactions of the fluorine, the disulfide bonds within the hard segments were brought closer together, facilitating bond exchange and enhancing self-healing efficiency (Supplementary Fig.\u0026nbsp;23 and Supplementary Note 5). Ab initio molecular dynamics (AIMD) simulations (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea) revealed that SFPU molecular chains tightly cluster together, distinctly separating from water molecule aggregates. The distance between the two aggregates was greater than 3 \u0026Aring;, indicating the tight binding of SFPU molecular chains and their excellent hydrophobicity. In addition, the radial distribution curves obtained from AIMD and Density Functional Theory (DFT) calculations (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb) showed that the hydrogen bonds (O-H) among water molecules were the most abundant, with no hydrogen bonds forming between SFPU and water molecules. And the average length of hydrogen bonds between carbonyl groups in the hard segments (\u0026minus;\u0026thinsp;N\u0026minus;H∙∙∙O\u0026thinsp;=\u0026thinsp;C\u0026minus;) was 3 \u0026Aring; (2.7\u0026ndash;3.3 \u0026Aring;), which was the distance between the hard segments. The distance was less than that between SFPU molecular chains and water molecules, indicating that the disulfide bond exchange reactions occurring between hard segments were almost undisturbed by water molecules. Then, we tested their water contact angles, which reached up to 112\u0026deg;. Even after soaking in water for five days, the water contact angle changed very little, performing much better than commercial polyurethanes lacking hydrophobic structures (Supplementary Fig.\u0026nbsp;24). As shown in Supplementary Fig.\u0026nbsp;25 and Movie 1, two severed SFPU films were drawn together on the water's surface through dipole-dipole interactions between fluorine groups. Once close enough, disulfide bond exchange began, ultimately achieving underwater self-healing through the combined effects of fluorine group interactions and disulfide bond exchange. Further studies on ShPiP's self-healing abilities in water and artificial lymph fluid revealed a self-healing speed comparable to that in conventional environments, with the process and performance remaining almost unaffected by water molecules (Supplementary Fig.\u0026nbsp;26\u0026ndash;29 and Supplementary Note 5).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eHowever, the sensing channel of PiMAS included both ShPiP and AgNW, so we conducted self-healing tests on the complete sensing channel. We placed channel-1 in artificial lymph fluid, cut and rejoined it (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec), and observed that it fully self-healed within 24 hours (Supplementary Movie 2). Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed (top row) shows the self-healing process of the channel as observed under a microscope in cross-section. After the channel was severed, ShPiP began the self-healing process first, followed by reconnection of the AgNW layer on its surface, resulting in a \"passive\" self-healing effect\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e. As shown in Supplementary Movie 3, completely cutting the ShPiP coated with the AgNW layer instantly extinguished the LEDs connected on either side of the layer; however, the \"passive\" self-healing subsequently relit the LEDs. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed (bottom row) displays repeated response curves of the channel to a 100 Hz audio frequency throughout the self-healing process, showing a gradual recovery from complete loss of sensing performance. This finding highlights the crucial role of ShPiP in the self-healing function of the entire channel. Furthermore, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee and f show that after self-healing, the channel\u0026rsquo;s ability to discriminate sound frequency and loudness was only minimally reduced. In summary, PiMAS not only demonstrated excellent pressure and stretch sensitivity but also outstanding multi-scenario self-healing capabilities. Compared to other iontronic and non-iontronic sensors with similar functions (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eg, Supplementary Table\u0026nbsp;3), PiMAS performed significantly better. This advancement indicates that our sensor not only provides precise feedback but also significantly enhances sustainability and reliability in complex environments.\u003c/p\u003e\n\u003ch3\u003eApplication of the PiMAS in recognizing real-world sounds\u003c/h3\u003e\n\u003cp\u003eFinally, we applied PiMAS to the recognition of real-world sounds. Male vocal cords are typically longer and thicker, with larger throat spaces, which produce lower-frequency sounds (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). In contrast, female vocal cords are generally shorter and thinner, with smaller throat spaces, resulting in higher-frequency sounds. To test this, three males and three females each said \u0026ldquo;hello, sensor,\u0026rdquo; and our sensor accurately and sensitively detected each utterance (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb, left). Fourier transformation of the time-domain graphs into frequency-domain graphs revealed that the detected frequencies for male voices were lower than those for female voices, demonstrating the excellent frequency discrimination capability of PiMAS (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb, right).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWe further tested PiMAS\u0026rsquo;s response to six piano keys, each with a distinct characteristic frequency (4# \u0026ndash; 76#: 32.70 Hz \u0026ndash; 2093.02 Hz), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec. Since each piano key contains additional harmonic frequencies, this experiment tested the frequency resolution of the sensor (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed). In the frequency-impedance spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed, 1st and 3rd rows), all frequencies within each piano key were sensitively detected, with the characteristic frequency showing the highest impedance response. The time-frequency-impedance mapping (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed, 2nd and 4th rows) demonstrated that all frequencies from each key press were detected continuously until the sound ceased, with the characteristic frequency having the largest and longest-lasting impedance response. We also used ShPiP to analyze three songs: a bass singing \u0026ldquo;Doubt\u0026rdquo; (82\u0026ndash;392 Hz), a baritone singing \u0026ldquo;Marechiare\u0026rdquo; (123\u0026ndash;493 Hz), and a tenor singing \u0026ldquo;Nessun dorma\u0026rdquo; (164\u0026ndash;698 Hz), and compared PiMAS\u0026rsquo;s performance to that of commercial acoustic sensors. Actual test images and response impedance spectra are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee, f, with video documentation in Supplementary Movie 4. The results showed that PiMAS provided significantly clearer signal feedback at the same sound pressure level compared to commercial sound sensor arrays, with sensitivities 3.5 times (bass), 3.4 times (baritone), and 3.2 times (tenor) higher (Supplementary Fig.\u0026nbsp;30).\u003c/p\u003e \u003cp\u003eIn conclusion, we developed PiMAS, inspired by the physiological characteristics of the human basilar membrane, which exhibits high sensitivity to various sound pressures and frequencies while addressing the non-regenerative limitation of basilar membrane hair cells. Composed of ShPiP and AgNW interdigitated electrodes, PiMAS efficiently converts sound stimuli into mechanical vibrations, detecting frequencies across a range of 20\u0026ndash;3300 Hz and sound pressures above 65 dB with high sensitivity to sound pressure (530 kPa⁻\u0026sup1;) and stretch (53.6), surpassing most ionic sensors. This sensitivity is primarily due to the ion hitching-in cage effect, driven by ion-dipole interactions between SFPU and [BMIM]⁺[TFSI]⁻ within ShPiP, which restricts cation flux, resulting in more pronounced impedance changes.\u003c/p\u003e \u003cp\u003eMoreover, ShPiP\u0026rsquo;s self-healing capability in conventional environments, underwater, and even in lymphatic fluid is attributed to a combination of dynamic disulfide bond exchange, fluorine-group dipole-dipole interactions, and increased chain mobility due to the ionic liquid\u0026rsquo;s plasticizing effect. PiMAS effectively differentiates between male and female voice frequencies and accurately detects characteristic frequencies of various piano keys, demonstrating superior responsiveness to singing voices compared to commercial acoustic sensors. The structural design and material functionality presented in this work provide valuable insights for developing future sustainable iontronic devices and acoustic sensors. Moving forward, we aim to further optimize PiMAS's structure and performance and explore its application in a wider range of settings.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e \u003cspan type=\"BoldUnderline\" class=\"BoldUnderline\" name=\"Emphasis\"\u003eMaterials.\u003c/span\u003e \u003c/p\u003e \u003cp\u003eHydroxyl-terminated polybutadiene (HTPB, Mn\u0026thinsp;=\u0026thinsp;2700\u0026ndash;3300 g/mol) was acquired from Energy Chemical, and its OH index was quantitatively assayed via titration prior to utilization. Isophorone diisocyanate (IPDI, 99%), dibutyltin dilaurate (DBTDL, 95%), anhydrous tetrahydrofuran (THF, 99.5%), anhydrous N,N-Dimethylformamide (DMF, 99.8%), 4-aminophenyl disulfide (98%), 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol (\u0026gt;\u0026thinsp;98%), and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM]\u003csup\u003e+\u003c/sup\u003e[TFSI]\u003csup\u003e\u0026minus;\u003c/sup\u003e, 98%) were procured from Aladdin (China) and were used as received without any further purification process. Silver nanowire suspensions (AgNW, diameter: 32\u0026thinsp;\u0026plusmn;\u0026thinsp;5 nm, length: 25\u0026thinsp;\u0026plusmn;\u0026thinsp;5 \u0026micro;m), obtained from Nanopyxis Corp., were diluted 4-fold before electrode spray-coating applications. The recipe of artificial inner ear lymphatic fluid: H\u003csub\u003e2\u003c/sub\u003eO 1L, NaCl 130\u0026ndash;140mmol/L, KCl 4.5mmol, CaCl\u003csub\u003e2\u003c/sub\u003e 2 mmol, MgCl\u003csub\u003e2\u003c/sub\u003e 1 mmol, NaHCO\u003csub\u003e3\u003c/sub\u003e 11.5 mmol, NaH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e 1 mmol, glucose 67.5 mg/dL.\u003c/p\u003e \u003cp\u003e \u003cb\u003ePolyurethane Synthesis\u003c/b\u003e \u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e1) Self-healable fluorinated polyurethane (SFPU)\u003c/h2\u003e \u003cp\u003eHTPB (10 g), THF (50 g) and IPDI (calculated quantity) were sequentially added to a custom-designed three-necked reactor, and the outlets were sealed using a Teflon stirring rod and rubber stoppers. The reactor was subsequently transferred to a 60 ℃ oil bath, and the Teflon stirring rod was connected to a mechanical stirrer. Stirring was initiated and continued until all reactants were dissolved in THF. The catalyst of DBTDL (0.5 wt% of the total reactants), chain extenders of 4-aminophenyl disulfide and 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol were sequentially added in the reactor. The molar ratio of NCO groups in IPDI to the total hydroxyl (OH) groups in HTPB, 4-aminophenyl disulfide and 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol was maintained at 1:1. The weight ratios of HTPB, 4-aminophenyl disulfide and 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol were set at 20/1/1, 20/1.5/1.5, 20/2/2 and 20/2.5/2.5, corresponding to the sample names SFPU-1 through SFPU-4, respectively. After reacting for 4 hours, 10 ml of methanol was injected into the reactor, and stirring was continued for an additional 10 minutes to terminate the polymerization. Finally, the reaction mixture was poured into methanol to precipitate the polyurethane, which was washed three times with methanol. The polymer was then dried in a vacuum oven at 80\u0026deg;C for 12 hours.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003e2) Fluorine-free polyurethane (SPU)\u003c/h3\u003e\n\u003cp\u003eThe synthesis method follows that of SFPU. The difference lies in the removal of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol. The composition consists of HTPB, 4-aminophenyl disulfide and IPDI in a ratio of 20/2/2.\u003c/p\u003e\n\u003ch3\u003e3) Polyurethane with little hard domains (SPU-NH)\u003c/h3\u003e\n\u003cp\u003eThe synthesis method was based on our previous research and shares the same composition as SPU\u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e. HTPB (10 g) and 4-aminophenyl disulfide (1 g) were sequentially added to a custom-designed three-necked reactor. DBTDL (0.5 wt% of the total reactants) and THF was then added to the reactor, and the outlets were sealed using a Teflon stirring rod and rubber stoppers. The reactor was subsequently transferred to an oil bath, and the Teflon stirring rod was connected to a mechanical stirrer. Stirring was initiated and continued until all reactants were dissolved in THF. The temperature of the oil bath was raised to 60 ℃, and IPDI was injected into the reactor using a syringe. The molar ratio of NCO groups in IPDI to the total hydroxyl (OH) groups in HTPB and 4-aminophenyl disulfide was maintained at 1:1. After reacting for 4 hours, 10 ml of methanol was injected into the reactor, and stirring was continued for an additional 10 minutes to terminate the polymerization. Finally, the reaction mixture was poured into methanol to precipitate the polymer, which was washed three times with methanol. The polymer was then dried in a vacuum oven at 80 ℃ for 12 hours.\u003c/p\u003e \u003cp\u003e \u003cb\u003eSensing Materials Preparation\u003c/b\u003e \u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e1) Self-healing piezo-ionotropic polymer (ShPiP)\u003c/h2\u003e \u003cp\u003eSFPUs were dissolved in DMF, followed by the addition of [BMIM][TFSI]. The mixture was stirred until a clear and homogeneous solution was obtained. The SFPUs and [BMIM][TFSI] were blended in mass ratios ranging from 90/10 to 10/90. The solution was then poured into a Teflon mold and allowed to dry at room temperature in a fume hood. Subsequently, the mold was placed on a heating plate at 80 ℃ and dried for 24 hours.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e2) Pristine PU-based iongel (PU-iongel)\u003c/h2\u003e \u003cp\u003eThe synthesis method follows that of ShPiP. The difference is that SFPU is replaced with SPU, and the mass ratio of SPU to [BMIM][TFSI] is 40/60.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3) PU-based iongel with little hard domains(PU-NH-iongel)\u003c/h2\u003e \u003cp\u003eThe synthesis method follows that of ShPiP. The difference is that SFPU is replaced with SPU-NH, and the mass ratio of SPU-NH to [BMIM][TFSI] is 40/60.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003ePreparation of piezo-ionotropic multi-resonance acoustic sensor (PiMAS)\u003c/h2\u003e \u003cp\u003eA mask with a specific interdigitated electrode pattern was placed in a Teflon mold, followed by spraying a silver nanowire solution using a spray coater (SRC-200 VT, E-FLEX Korea, nozzle: 0.05 mm, pressure: 200 mbar). After removing the mask, a specific SFPU/[BMIM][TFSI] solution was poured into the same Teflon mold and dried using the same method as for the ShPiP preparation. The thickness of the channels was controlled by the weight of SFPU/[BMIM][TFSI] solution poured into the mold. Channels measuring 100 \u0026micro;m to 800 \u0026micro;m were cut into sizes of 1 cm \u0026times; 4 cm, arranged in order from thinnest to thickest, attached to a hollow rectangular support frame and wired accordingly.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eCharacterization\u003c/h2\u003e \u003cp\u003eThe chemical compositions of all chemicals and polyurethanes were verified using \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003eH NMR spectroscopy conducted at 25\u0026deg;C on a Bruker AVIII400 NMR spectrometer, with tetramethylsilane (TMS) serving as an internal standard. The weight-average molecular weights (Mw) and molecular weight dispersity (MWD) were determined via gel permeation chromatography (GPC, Waters-2690) employing tetrahydrofuran (THF) as the mobile phase at 40℃. The mechanical properties of the polyurethanes were assessed at room temperature using a universal testing machine (UTM, Instron 5567) with dumbbell-shaped specimens, in accordance with ASTM D638\u0026ndash;5 standards. This equipment was also utilized to mechanically stimulate sensors during gauge factor testing. Water contact angle (WCA) measurements were performed using a contact angle goniometer (OCA25, DataPhysics, Germany). X-ray diffraction (XRD) analyses were conducted using a Bruker D8 Advance diffractometer with Cu-Kα radiation (wavelength\u0026thinsp;=\u0026thinsp;1.54060 \u0026Aring;). Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) absorption spectra were recorded on an iD5 ZnSe ATR instrument (Cary660, Agilent). Dynamic mechanical thermal analysis (DMTA) was executed using a DMA Q800 system from TA Instruments (USA), with measurements conducted at a heating and cooling rate of 3\u0026deg;C/min from \u0026minus;\u0026thinsp;120 to 100 ℃ in a liquid N\u003csub\u003e2\u003c/sub\u003e atmosphere, at a frequency of 1 Hz. Scratch recovery tests for self-healing experiments were carried out under an optical microscope (Olympus/BX 51TF Instec H601, Japan) in various time periods, under both ambient (20\u0026ndash;40% relative humidity) and submerged conditions (DI water). Electrochemical impedance spectroscopy (EIS) was performed at room temperature using an electrochemical analyzer PGSTAT302N (Metrohm Autolab) within a frequency range of 0.1 Hz to 1 MHz, applying a 10 mV AC signal. For Raman intensity mapping, a Renishaw inVia Reflex confocal micro-Raman spectrometer was used to analyze the samples. Each sample was mounted on a custom-built stretching fixture to enable precise control during measurements. Raman scans were performed at predefined locations, covering an area of 50 \u0026micro;m \u0026times; 50 \u0026micro;m, with a DC voltage of 1V applied throughout. Initial measurements were taken on unstretched samples, followed by scans after stretching the samples to a predetermined length. The confocal setup of the spectrometer allowed for high spatial resolution, enabling detailed mapping of Raman-active regions and revealing the molecular composition and structural characteristics of the samples under both conditions. The impedance spectra were analyzed using equivalent circuit models in NOVA software to evaluate the bulk resistance (R\u003csub\u003eb\u003c/sub\u003e) of the devices, from which the ionic conductivity was calculated as σ = (l/R\u003csub\u003eb\u003c/sub\u003e \u0026times; A), where σ is the ionic conductivity, l is the film thickness, and A is the electrode area. The morphology of AgNW was examined using a scanning electron microscope (SEM, Verios G4 UC, Thermo Scientific), which was also equipped with energy dispersive spectroscopy (EDS) to analyze element mass percentages. A precision LCR meter (Agilent Keysight Technologies, E4980A) was employed to measure the dielectric constant, capacitance, and impedance data of the sensing materials and sensors. The amplitude of individual channels in the sensors was measured using a laser vibrometer (HEPU, GC03-30A).\u003c/p\u003e \u003cp\u003e \u003cb\u003eSimulation and Calculation\u003c/b\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e1) Hydrophobicity simulation and calculation\u003c/h2\u003e \u003cp\u003eTo study the hydrophobicity or hydrophilicity of the synthesized polyurethanes, we performed density-functional theory (DFT) calculations to compute water adsorption energy, and Ab-Initio Molecular Dynamics (AIMD) calculations to simulate the process of water adsorption for polyurethanes. DFT and AIMD calculations were carried out by using Vasp packages. All the systems were initially relaxed by density-functional theory with GGA-PBE. In the AIMD simulations, the systems in the presence of water molecular were equilibrated under the canonical ensemble (NVT) for 100 ps with 0.5 fs as time steps) at room temperature conditions (300 K). Average properties were then evaluated from the last simulation iteration. To obtain better statistics properties and structural properties, for each system two independent runs were simulated, with setting the molecular straight or zigzag. we added 80 water molecular [240 (160 H and 80 O) atoms totally] surrounding target molecular. The averaged initial distance between the target molecular was around 3 \u0026Aring;, this distance between these H\u003csub\u003e2\u003c/sub\u003eO and the target molecular were then fully relaxed in the process of DFT structural relaxations and AIMD simulations.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e2) Binding energy simulation and calculation\u003c/h2\u003e \u003cp\u003eThe theoretical calculations were performed via the Gaussian 16 suite of programs. The structures of the studied molecules (denoted by A, B2, and C) and the complexes of A-B2 and A-B2-C were fully optimized at the B3LYP-D3BJ/6\u0026ndash;31\u0026thinsp;+\u0026thinsp;G(d,p) level of theory. The vibrational frequencies of the optimized structures were carried out at the same level. The structures were characterized as a local energy minimum on the potential energy surface by verifying that all the vibrational frequencies were real. To avoid basis set superposition error (BSSE), counterpoise correction was applied to obtain the complexation energies between A and B in the A-B and A-B-C complexes at the B3LYP-D3BJ/6-311\u0026thinsp;+\u0026thinsp;G(d,p) level of theory. Independent gradient model (IGM) analysis was derived by using the Multiwfn software. The Visual Molecular Dynamics (VMD) program was used to plot the color-filled isosurfaces graphs of IGM analytical results. The IGM method can visualize weak-interaction areas and their characteristics. Consequently, the initial binding energy of A and B\u003csub\u003e2\u003c/sub\u003e is -87.60 kcal/mol, which decreases to -81.04 kcal/mol upon the addition of C, indicating the presence of weak interactions between B2 and C in the complexes A-B2-C. Within this system, A corresponds to [TFSI], B2 to [BMIM], and C to a fluorine-containing chain extender.\u003c/p\u003e \u003c/div\u003e "},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data are included in this article and its Supplementary Information file. All data are available from the corresponding authors upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledg\u003c/strong\u003e\u003cstrong\u003ee\u003c/strong\u003e\u003cstrong\u003ements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Brain Pool program, National R\u0026amp;D Program and Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (RS-2024-00405818, 2022M3H4A1A02076825, 2022M3C1A3081211, 2021M3H4A1A03049075, 2020R1A2C3014237).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJ.Z. and D.H.K. supervised the project. D.H.K., J.Z., W.B.Y. and J.S.K. developed the theoretical concepts and designed the experiments. W.B.Y., J.S.K. and Z.K. carried out all the experiments, while W.B.Y., J.S.K., Z.K. and Z.Y. conducted the material characterization studies. E.K.B., F.L., C.C. and Y.T. provided assistance with experimental procedures. D.H.K., J.Z. and J.Y.L. reviewed and provided feedback on the manuscript. W.B.Y., J.S.K., and D.H.K. wrote the manuscript, with D.H.K. responsible for revisions. All authors discussed the results and contributed to the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdditional information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSupplementary Information\u003c/strong\u003e is available for this paper at www.nature.com/reprints.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrespondence and requests for materials\u003c/strong\u003e should be addressed to Jin Zhu or Do Hwan Kim.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBermingham-McDonogh O, Reh TA (2011) Regulated Reprogramming in the Regeneration of Sensory Receptor Cells. 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ACS Appl Mater Interfaces 12:11072\u0026ndash;11083\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-5810151/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5810151/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSensorineural hearing loss is the most common form of deafness, typically resulting from the loss of sensory cells on the basilar membrane, which cannot regenerate and thus lose sensitivity to sound vibrations. Here, we report a reconfigurable piezo-ionotropic polymer membrane engineered for biomimetic sustainable multi-resonance acoustic sensing, offering exceptional sensitivity (530 kPa⁻\u0026sup1;) and broadband frequency discrimination (20 to 3300 Hz) while remaining resistant to \"dying.\" The acoustic sensing capability is driven by an ion hitching-in cage effect intrinsic to the ion gel combined with fluorinated polyurethane. In this platform, the engineered ionotropic polymer stretches under acoustic vibrations, allowing cations to penetrate the widened hard segments and engage in strong ion-dipole interactions (cation\u0026middot;\u0026middot;\u0026middot;F), thereby restricting ion flux and amplifying impedance changes. Additionally, the sensor\u0026rsquo;s sustainability is ensured through its self-healing properties and hydrophobic components, which enable effective self-repair in both conventional and aqueous environments without ion leakage, achieving a room-temperature healing speed of 0.3\u0026ndash;0.4 \u0026micro;m/min. Leveraging this newly developed sustainable acoustic sensing technology, our devices demonstrate high proficiency in identifying specific sounds in everyday environments (e.g., human voices, piano notes), underscoring their potential as artificial basilar membranes.\u003c/p\u003e","manuscriptTitle":"A Reconfigurable Piezo-Ionotropic Polymer Membrane for Sustainable Multi-Resonance Acoustic Sensing","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-02-04 16:26:19","doi":"10.21203/rs.3.rs-5810151/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":"87127b9d-68ae-4991-aaf0-b3410d20251f","owner":[],"postedDate":"February 4th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":43838586,"name":"Physical sciences/Materials science/Soft materials/Gels and hydrogels"},{"id":43838587,"name":"Physical sciences/Materials science/Materials for devices/Sensors and biosensors"}],"tags":[],"updatedAt":"2025-09-03T07:07:08+00:00","versionOfRecord":{"articleIdentity":"rs-5810151","link":"https://doi.org/10.1038/s41467-025-63643-4","journal":{"identity":"nature-communications","isVorOnly":false,"title":"Nature Communications"},"publishedOn":"2025-09-02 04:00:00","publishedOnDateReadable":"September 2nd, 2025"},"versionCreatedAt":"2025-02-04 16:26:19","video":"","vorDoi":"10.1038/s41467-025-63643-4","vorDoiUrl":"https://doi.org/10.1038/s41467-025-63643-4","workflowStages":[]},"version":"v1","identity":"rs-5810151","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5810151","identity":"rs-5810151","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}