Embedded multilayer strain architectures create self-sensing multifunctional titanium in additive manufacturing

Embedded multilayer strain architectures create self-sensing multifunctional titanium in additive manufacturing | 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 Embedded multilayer strain architectures create self-sensing multifunctional titanium in additive manufacturing Alisha Bhatt, Wenqing Chen, Zheng Wu, Prasenjit Kabi, Paul Brennan, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9237610/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Multifunctional structural metals capable of monitoring their internal mechanical state are increasingly important for aerospace, biomedical, and intelligent manufacturing applications, yet integrating thermally sensitive sensing architectures into high-temperature metal additive manufacturing remains challenging. Here we show that multilayer strain sensing architectures can be embedded directly within Ti-6Al-4V during laser powder bed fusion by combining high-resolution printing of polymer–metal gauges with powder mediated thermal protection. We evaluate four sensor architectures, including commercial foil gauges and directly printed gauges with different dielectric layers, and identify material stacks that survive embedding while retaining electrical functionality. The embedded sensors preserve strain sensing performance under mechanical loading, maintain structural integrity, and exhibit cytocompatibility. These results establish a route to multifunctional titanium with internal sensing capability and provide a materials integration framework for embedding functional devices within additively manufactured metals. Physical sciences/Materials science/Materials for devices/Sensors and biosensors Physical sciences/Nanoscience and technology/Nanoscale devices/Sensors Embedded strain sensors Titanium additive manufacturing Laser powder bed fusion Direct printing of functional inks Self-monitoring metal components Roll-to-roll deposition Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Introduction Metal components capable of internally monitoring strain are increasingly important for applications in aerospace structures 1 , biomedical implants 2 , 3 , and structural health monitoring systems 4 . Conventional monitoring approaches rely on external sensors, which provide limited spatial resolution and cannot capture stress distributions within the material 5 , 6 . Embedding sensors directly during metal additive manufacturing (AM) offers a pathway to measure strain internally and in real time, enabling predictive maintenance and integration with digital twin frameworks in critical engineering systems 7 , 8 . Titanium alloys such as Ti-6Al-4V are widely used in biomedical 9 and aerospace components 10 because of their high mechanical strength, corrosion resistance, and biocompatibility 11 . However, integrating sensors within these alloys remain challenging because of their high melting temperature 12 , low thermal conductivity, and the sensitivity of polymer dielectric materials 13 to localized laser heating during fabrication. Previous strategies for incorporating sensors in metallic structures include protective coating, cavity integration, or the use of prefabricated metallic sensing layers 14 , 15 . Although these approaches have shown promise, they often increase fabrication complexity, restrict design flexibility 16 ,1718 , and have primarily been demonstrated in alloys such as stainless steel 316L 19 , 20 or Inconel 718 21 . Commercial strain gauges typically consist of metallic foils mounted on polymer dielectric substrates, and their integration into titanium alloy components during laser powder bed fusion (LPBF) remains difficult 22 . The extreme thermal gradients and rapid heating cycles associated with LPBF can lead to polymer degradation, delamination, or loss of electrical functionality, limiting the reliability of embedded sensing systems 23 . Direct ink writing (DIW) provides a route to deposit functional materials with high spatial precision and flexible sensor geometries 24 . Tripropylene glycol diacrylate (TPGDA) was selected as the dielectric layer because it can form uniform thin films compatible with roll-to-roll deposition (R2R) 25 , provides sufficient thermal stability under controlled curing conditions, and promotes adhesion with metallic nanoparticle inks used for strain sensing 26 . Multilayer sensor architectures, where dielectric and conductive layers are independently optimized, can improve both resolution and durability under the thermal cycling conditions associated with LPBF processing 27 – 29 . The combination of DIW printing and TPGDA dielectric layers therefore enables fabrication of multilayer polymer–metal strain gauges compatible with metal additive manufacturing. Here we present a strategy for embedding multilayer strain-sensing architectures within Ti-6Al-4V components fabricated by LPBF. A powder-mediated shielding layer is used to mitigate thermal exposure during laser processing, while DIW enables direct deposition of polymer–metal sensing structures. The embedded sensors retain strain-sensing functionality under mechanical loading and exhibit cytocompatibility. These results establish a materials integration framework for embedding functional devices within additively manufactured metals, enabling the development of self-monitoring structural components for aerospace, biomedical, and intelligent manufacturing applications. 2. Results and Discussion 2.1. Surface Roughness and Wettability of Tripropylene Glycol Diacrylate (TPGDA) We selected TPGDA as a model dielectric to establish a transferable strategy for integrating printable polymer layers within metal substrates. TPGDA provides a processable thin film compatible with R2R deposition, enabling controlled investigation of surface modification and printing behavior relevant to a broader class of printable dielectrics. Importantly, the purpose of this study was to demonstrate a proof of concept for surface treatment and printing optimisation; therefore, the methodology and findings are expected to be transferable to other printable dielectric materials with a similar processing requirement. In this multilayer system, the dielectric surface governs both ink wettability and interfacial stability and is therefore critical for achieving high-resolution patterning and mechanical durability. The strain gauge compromises of a Ti-6Al-4V base layer, a TPGDA dielectric layer, and a sensing layer formed from commercial 50 wt. % silver nanoparticle dispersion in tripropylene glycol mono methyl ether (TPM) ink, hence the surface morphology of the dielectric is critical for both printability and durability. The TPGDA dielectric layer was deposited on Ti-6Al-4V using R2R vacuum web coating facility. Atomic force microscopy (AFM) imaging (Fig. 1 a) shows that TPGDA deposition preserves the underlying substrate roughness, but the as-deposited surface exhibits insufficient wettability for DIW 30 . Therefore, plasma and electron beam irradiation (EBI) treatments were applied to modify the TPGDA surface and improve its printability. Increasing the plasma current enhanced surface etching and produced pronounced peaks, whereas EBI generated a more symmetrical distribution of valleys and peaks, resulting in a smoother and more uniform surface morphology. Increasing the plasma current enhanced etching and produced peaks, whereas EBI generated a more symmetrical distribution of valleys and peaks, yielding a smoother and more uniform surface. Quantitative roughness parameters (Fig. 1 b) confirmed that both EBI and low current plasma yielded lower surface roughness ( \(\:{S}_{a}\) ) and root mean square ( \(\:RMS\) ) values in comparison to the higher plasma, suggesting their suitability for DIW . Spectroscopic analysis confirmed these observations. Fourier Transform Infrared spectroscopy (FTIR) spectra (Fig. 1 c) showed increase in the intensity of the ester carbonyl (C = O) stretching band at approximately 1730 cm⁻¹ with increasing plasma current, indicating enhanced surface polarity and wettability. This band is characteristic of the acrylate groups present in TPGDA and its polymerized network. The increase in C = O intensity is interpreted as evidence of increased surface oxidation/polar functionality following plasma treatment, which can enhance the surface polarity of the cured polymer coating and improve wettability for subsequently deposited layers, such as TPM silver nanoparticle ink. It should be noted that this interpretation relates to the surface properties of the cured polymer coating rather than the initial wetting of the monomer on the substrate prior to curing. In addition, the FTIR peak at approximately 810 cm⁻¹, corresponding to the out-of-plane bending of the acrylate C = C bond, is commonly used to assess the amount of residual unsaturation and therefore the degree of cure of the coating. A reduction in the intensity of this peak indicates a higher extent of polymerization. Similarly, EBI modified the surface chemistry of the TPGDA layer, increasing surface polarity and correlating with the observed reduction in infrared (IR) transmittance. Both plasma and EBI improved the surface energy and promoted ink adhesion. However, increasing plasma current also increased surface roughness, which can negatively affect high resolution printing. The practical consequence of these effects was captured by TPM silver nanoparticle ink contact angle measurements (Fig. 1 d). Low-current plasma produced moderate spreading and stable contact angles, while high current plasma and EBI induced extensive spreading and very low contact angles due to the combined effects of polarity and morphology. Excessive wettability, however, led to ink bleeding and compromised printing resolution (Supplementary Fig. 2). Overall, low current plasma treatment achieved the optimal balance of smooth morphology, sufficient polarity, and controlled wettability, enabling both reliable adhesion and high-resolution strain gauge patterning. These results establish that controlled tuning of dielectric surface chemistry and morphology is essential for integrating conductive features within multilayer architectures and provide a generalizable framework for printable polymer–metal interfaces in AM environments. 2.2. Thermal Constraints of the Dielectric Layer Define Curing Conditions for Nanoparticle Strain Gauges We establish the thermal constraints governing integration for the polymer dialectic and conductive ink within the LPBF environment (see Supplementary Fig. 3 for the methodology). Thermogravimetric analysis (TGA) revealed progressive weight loss beginning at ~ 220°C, indicative of polymer degradation (Fig. 2 a). Differential scanning calorimetry (DSC) analysis further identifies a glass transition at ~ 260°C, crystallisation at ~ 280°C, and complete melting at ~ 350°C (Fig. 2 b). Together these results define a narrow thermal processing window, in which exposure temperatures above ~ 200°C leads to irreversible damage and change in the polymer network. We then examine the curing behaviour of the TPM silver nanoparticle ink under these constraints, droplets were deposited onto plasma-treated TPGDA films and furnace-cured between 100–250°C (Fig. 2ci-ii). Resistance decreased linearly with curing time across all conditions, with faster reduction at higher temperatures due to enhanced conductivity (Fig. 2 d). However, temperatures ≥ 200°C, induce microstructural degradation characterised by pore formation within the conductive layer (Fig. 2 e). This behaviour is consistent with accelerated solvent evaporation and reduced mechanical robustness. The maximum thermal tolerance of the ink was ~ 250°C for 8500 s before degradation was evident. While elevated temperatures promote rapid conductivity development, they also approach degradation threshold of both the dielectric and conductive layers. We therefore identity curing at 150°C for 3800 s, which produced strain gauges with ~ 350 Ω resistance comparable to commercial devices 32 – 35 , while avoiding degradation of both the dielectric and the conductive layer. These results establish the additional requirements for a protective powder layer during laser scanning and a carefully controlled curing protocol to ensure device stability and performance. These results motivate the incorporation of a powder-mediated shielding strategy to mitigate transient thermal exposure, enabling retention of both dielectric integrity and conductive functionality during embedding. 2.3. High-Resolution Strain Gauge Embedding via Printing and Thermal Management Strategies Embedding high-resolution strain gauges into LPBF fabricated Ti-6Al-4V parts requires careful coordination of printing precision, thermal management, and material selection. The process begins with the micropipette nozzle, where tip geometry directly affects printing fidelity. Figure 3ai-iii shows the nozzle tip end pulled by the P-1000 micropipette puller (P-1000), demonstrating that the pull velocity influences the final tip size. Figure 3bi-iii shows the tip end where the heating temperature is indirectly defined as the ramp temperature which is not the real temperature. Using the P-1000 puller, we found that decreasing the ramp temperature and pull velocity produced smaller, more reproducible tips, whereas higher pull velocities increased the tip size due to extended neck reshaping (Fig. 3ci-ii). Tip size variation remained below 5% across all conditions, consistent with ref. 36 , ensuring both high spatial resolution (≤ 10 µm) and nozzle durability required for reliable conductive ink deposition. Nozzle tip breakage and bleeding were observed at low pull velocities (of 14). Based on these results, a ramp of 65 + and a pull velocity of 12 were selected to achieve durable, high-resolution nozzle (Supplementary Fig. 4). The printing process is followed by embedding under LPBF conditions, where thermal exposure can compromise strain gauge integrity. A 1 mm layer of Ti-6Al-4V powder was applied over the gauges to act as a thermal barrier. Simulations indicate that, although surface powder temperatures reach ~ 3347°C during laser scanning, the thermal effect near the embedded gauges is reduced to ~ 25°C, effectively mitigating thermal degradation (Fig. 3 d). Although the thermal simulation presented indicated that a thinner powder layer could reduce the peak temperature at the strain gauge, a 1 mm layer was selected to ensure a sufficient safety margin and account for any discrepancies in powder spreading and potential laser exposure. This protective layer also alleviates stress concentrations at the embedding site, helping preserve gauge structure and function. The thermal model represents transient heat conduction during the laser scanning process. A first order estimate of the thermal penetration depth is obtained using \(\:L\approx\:\:\sqrt{\alpha\:\tau\:}\) 37 , where \(\:\alpha\:\) is the thermal diffusivity of the powder and \(\:\tau\:\) is the laser interaction time. Using the process parameters ( \(\:v=\) 1.2 m/s, see supplementary methods), the estimated penetration depth is on the order of ~ 10 µm, which is significantly smaller than the 1 mm powder protective layer. This analytical estimate is consistent with the FEM results, which show minimal rise in temperature at the location of the sensor. The selected 1 mm powder layer will provide substantial additional safety margin to ensure sensor protection against any potential local thermal fluctuations during the laser scanning process. The interplay of nozzle precision and thermal protection was further tested across four strain gauge configurations: commercial foil with PI backing, DIW printed serpentine gauges with PI backing, glass fibre (GF) -reinforced phenolic backing, and the TPGDA backing (Fig. 3ei-ii). PI-backed gauges failed due to thermal deformation and adhesive degradation, whereas GF-reinforced phenolic and TPGDA-backed gauges survived, demonstrating that material selection shows post-embedding success. Although PI is known for its high thermal stability 38 , 39 compared to many other polymers 40 , failures in this case are likely to do with the LPBF processing conditions rather than the thermal limit of the material. The rapid heating and cooling cycles, steep thermal gradients and localised energy input during the process could result in interfacial stresses and degradation of the adhesive layer bonding the gauge to the substrate, which as a result leads to delamination. Measurements before and after embedding showed resistance decreases (Δ R = 134 Ω for phenolic, Δ R = 144 Ω for TPGDA), consistent with additional sintering of the silver nanoparticle ink induced by residual thermal exposure. These results confirm that, when printing resolution, thermal shielding, and backing material are carefully tuned, functional strain gauges can be reliably integrated into metal parts (Fig. 3 e). Together, these findings reveal a pathway from nozzle design to sensor survival: precise nozzle tips enable accurate deposition, the powder layer protects against LPBF thermal effects, and appropriate backing materials preserve electrical and structural integrity. This integrated approach provides a practical framework for embedding high-resolution, durable sensors in metal components fabricated via LPBF, highlighting the critical interactions between printing parameters, thermal management, and material choice. Collectively, this establishes a design framework for integrating functional sensing architectures within AM metals, linking processing parameters to device survival and performance. Although thinner powder layers may also reduce thermal exposure, a 1 mm layer was selected here to maximize process robustness and ensure reliable protection against local variations in powder packing and laser-induced heating. 2.4. Integrated Fabrication and Performance of Embedded Strain Gauges The embedded strain gauges demonstrated both cytocompatibility and functional integrity when integrated into LPBF-fabricated Ti-6Al-4V parts, highlighting their potential for biomedical and structural sensing applications. Four types of strain gauges DIW printed sensors with TPGDA, PI, and GF-reinforced phenolic backings, and commercial foil sensors were evaluated for biocompatibility by immersing them in PBS for three days and three weeks. Although the sensor was encapsulated within the Ti-6Al-4V structure, this assessment was performed to determine whether any leaching of components from the embedded multilayer sensor system (e.g., dielectric layers or conductive materials) could affect cell viability. High cell viability (80–90%) was observed across all sensors (Fig. 4 a), with predominantly elongated, healthy fibroblast cells confirmed by fluorescence imaging (Fig. 4 b, Supplementary Fig. 6). The Ti-6Al-4V base layer, dielectric layers (TPGDA, PI, GF-reinforced phenolic), and sensor layers (TPM silver nanoparticle ink or constantan alloy) collectively exhibited minimal cytotoxicity, consistent with prior reports 41 – 43 . These results indicate that the multilayer sensor constructs are potentially suitable for in vivo applications, though additional long-term biocompatibility studies would be required for clinical use. To assess functional performance, the same strain gauges were embedded in Ti-6Al-4V parts using a 1 mm powder protective layer during LPBF and compared to bare gauges on a substrate. Mechanical testing under three-point bending revealed that all sensors retained their strain-sensing capability (Fig. 4 c), with gauge factors (K) increasing slightly after embedding due to localized thermal-induced sintering of the TPM silver nanoparticle ink. This demonstrates that the LPBF process can embed DIW printed sensors while inducing partial curing, a slight densification of the conductive ink that improves electrical connectivity without complete degradation of the dielectric or backing layer (Fig. 4di-iv). This demonstrates that the LPBF process can both embed and partially cure DIW printed sensors without complete degradation. The GF-reinforced phenolic and TPGDA-backed sensors survived the embedding process, while PI-backed and commercial foil sensors were prone to thermal-induced performance variations. Some fluctuations in the stress-strain curves were observed for the surviving sensors, likely due to laser-induced thermal effects causing minor resistance changes and Wheatstone bridge imbalance (Fig. 4ei-iv). The overall stress-strain response was preserved, confirming the feasibility of embedding functional strain gauges using a powder shielding approach. These results establish a linked framework for integrating functional, biocompatible strain gauges into LPBF-fabricated metal parts. High cell viability demonstrates suitability for biomedical applications, while mechanical testing confirms that thermal protection via powder layers and appropriate backing materials preserves strain-sensing performance. Optimizing nozzle geometry, powder thickness, and backing material selection collectively ensures that embedded sensors maintain both biological safety and functional integrity, providing a robust strategy for next-generation smart implants and structural monitoring devices. Together these finding indicate that careful selection of powder thickness, backing material, and sensor design allows embedded sensors to maintain both functional integrity and cytocompatibility, providing a methodology for next generation smart implants and structural monitoring devices. More broadly, they establish design criteria linking backing material, thermal exposure, and interfacial stability, providing a framework for embedding multifunctional devices within structural metals for biomedical and sensing applications. These results support the cytocompatibility of the embedded sensor material system under the conditions tested, while further long-term biological evaluation will be required to assess suitability for clinical implantation. 3. Methodology Figure 5 shows a flow chart that summarizes the sensor embedding methodology. Figure 5 a shows four types of strain gauges that were embedded using LPBF, each consisting of a dielectric backing and a sensing layer: (1) a commercial foil gauge on a PI backing, (2) a DIW printed gauge with commercial PI, (3) a DIW printed gauge with GF-reinforced phenolic, and (4) a DIW printed gauge with a thin-film TPGDA dielectric deposited on a moving substrate in a R2R facility. The sensing layer for the DIW printed gauges was deposited using TPM silver nanoparticle ink. Full material specifications, particle sizes, and supplier details are provided in Supplementary. Commercial and DIW gauges with PI or GF-reinforced phenolic backings were bonded to Ti-6Al-4V substrates using adhesive. For TPGDA thin films, R2R deposition and roller compression were used to achieve adhesion. Deposition rates, curing conditions, and roller parameters are outlined in the Supplementary Methods and Supplementary Fig. 7. LPBF was used to embed the sensors within Ti-6Al-4V. Samples were printed under an argon atmosphere using an Aconity Lab system with optimised process parameters. A laser power of 190 W and scan speed of 1.2 m/s were maintained throughout the build. The full process map, hatching strategy, and powder specifications are provided in Supplementary Tables 6–8. Strain gauge designs were printed onto dielectric layers via DIW, using custom nozzles and a controlled translational stage. Sensors were cured by thermal sintering between 100–250°C. Details of nozzle manufacturing, scanning electron microscopy (SEM) imaging, printing speeds, and curing times are provided in Supplementary Table 5 and Supplementary Fig. 4. Surface and material characterisation was carried out by atomic force microscopy, FTIR, DSC, TGA, and contact angle measurements to assess dielectric properties and printability. Instrument models, acquisition parameters, calibration details, and supplementary figures (Supplementary Methods) provide full characterisation protocols. Two embedding strategies were used: (1) cold embedding with powder protection for PI- and phenolic-based sensors, and (2) a hybrid process combining R2R and DIW for TPGDA-based sensors. Schematics of both workflows are summarised by Fig. 5 b-e. Stepwise embedding protocols are provided in Supplementary Fig. 7 and Fig. 5 d. Thermal simulations were performed in Abaqus to analyse heat transfer through the 1 mm protective powder layer. Mesh details, Goldak’s model parameters 44 , and material constants are summarised in Supplementary Tables 6–8 and Supplementary Fig. 5. Mechanical performance was validated using three-point bending tests, while biocompatibility was assessed on human dermal fibroblasts (HDF) cell lines using LIVE/DEAD and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Complete assay protocols, incubation conditions, and statistical analyses are detailed in Supplementary Methods and Supplementary Fig. 6. Strain signals from embedded gauges were recorded using a Wheatstone bridge circuit connected to Arduino-based wireless data acquisition shown in Fig. 5 d. Circuit diagrams, component specifications, and software versions are shown in Supplementary Fig. 8. 4. Conclusions We have demonstrated a strategy for creating multifunctional titanium by embedding strain-sensing architectures directly within Ti-6Al-4V during laser powder bed fusion. By combining direct printing of multilayer polymer–metal gauges with a Ti-6Al-4V powder layer for thermal protection, we show that thermally sensitive sensing elements can survive incorporation into a high-temperature metal additive manufacturing process. Among the architecture evaluated, TPGDA- and GF phenolic-backed printed sensors retained electrical functionality and strain-sensing performance after embedding, whereas polyimide-based configurations were more susceptible to thermal and interfacial failure. Rather than presenting a single device optimization, this study establishes a materials integration framework linking dielectric surface properties, conductive ink curing behavior, backing-layer selection, and powder-mediated thermal shielding to the successful embedding of functional sensors in LPBF titanium. Although TPGDA and TPM silver nanoparticle ink were used here as model materials, the design principles identified namely control of dielectric surface chemistry and morphology, management of curing-temperature limits, and use of powder-mediated thermal shielding are expected to be transferable to other printable polymer–metal sensor systems. These results show that metal additive manufacturing can be extended beyond structural fabrication to produce titanium components with built-in sensing capability. More broadly, the work establishes a materials-integration framework in which interfacial design, curing conditions and powder-mediated thermal shielding are jointly used to incorporate functional devices into structural metals. This approach provides a foundation for self-monitoring metallic systems in aerospace, biomedical and intelligent manufacturing applications. 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A computationally efficient thermo-mechanical model for wire arc additive manufacturing. Addit. Manuf. 46 , (2021). Additional Declarations There is NO Competing Interest. Supplementary Files EmbeddedmultilayerstrainarchitecturescreateselfsensingmultifunctionaltitaniuminadditivemanufacturingNatureCommunicationMaterialsAlishaBhattSUPPLEMENTARY290326.docx Supplementary Material Graphicalabstract.docx Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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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-9237610","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":616516856,"identity":"25ae4ccf-c811-442e-ba50-478e89c5f97a","order_by":0,"name":"Alisha Bhatt","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAs0lEQVRIiWNgGAWjYDACCR4QacPAwE6SlgMJaQwMzCRqOUyCFv7ZvQc/f/xxXt6cmYH5xcc2Yiy5cy5Z4kDCbcOdzQxsljOJ0cJwI8cApIVxw2EGNmOeM0TokL+RY/zjQMI5e+K1GNzIMQPaciARqIX5MU8FEVoM75wxsziTlpy84TBjG+MMYrTI3e4xvlFhY2e74Xjz4Q8fDIjQggQY2yRI0wAEzB9I1jIKRsEoGAUjAgAAdDA5ExmsyswAAAAASUVORK5CYII=","orcid":"","institution":"Argonne National Laboratory","correspondingAuthor":true,"prefix":"","firstName":"Alisha","middleName":"","lastName":"Bhatt","suffix":""},{"id":616516857,"identity":"1b588783-42e5-4889-b642-ddc1dbd78562","order_by":1,"name":"Wenqing Chen","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Wenqing","middleName":"","lastName":"Chen","suffix":""},{"id":616516858,"identity":"9a33d7b1-b5bf-46fe-b199-328a74b86cb5","order_by":2,"name":"Zheng Wu","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Zheng","middleName":"","lastName":"Wu","suffix":""},{"id":616516859,"identity":"2861e382-73c4-4eed-bcb0-5e81823f1310","order_by":3,"name":"Prasenjit Kabi","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Prasenjit","middleName":"","lastName":"Kabi","suffix":""},{"id":616516860,"identity":"d6edfa79-4b7e-494b-8bd7-c0f40f0684d0","order_by":4,"name":"Paul Brennan","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Paul","middleName":"","lastName":"Brennan","suffix":""},{"id":616516861,"identity":"a2a3f411-22e8-4126-bb6a-5142e1337e32","order_by":5,"name":"Samy Hocine","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Samy","middleName":"","lastName":"Hocine","suffix":""},{"id":616516862,"identity":"53400d3c-d85d-4e8b-bc67-d398fb5821f0","order_by":6,"name":"Elena Ruckh","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Elena","middleName":"","lastName":"Ruckh","suffix":""},{"id":616516863,"identity":"edf40b61-5c3a-45f8-9edc-548437ed3abb","order_by":7,"name":"Hazel Assender","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Hazel","middleName":"","lastName":"Assender","suffix":""},{"id":616516864,"identity":"1f6dbd59-cdd3-4ed0-a28f-3df79215b2a2","order_by":8,"name":"Rob Snell","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Rob","middleName":"","lastName":"Snell","suffix":""},{"id":616516865,"identity":"fb136948-34a9-49e4-a97a-6bbad25f1846","order_by":9,"name":"Iain Todd","email":"","orcid":"https://orcid.org/0000-0003-0217-1658","institution":"University of Sheffield","correspondingAuthor":false,"prefix":"","firstName":"Iain","middleName":"","lastName":"Todd","suffix":""},{"id":616516866,"identity":"1d540210-54b4-4068-b576-5389eccab8ff","order_by":10,"name":"Peter Lee","email":"","orcid":"https://orcid.org/0000-0002-3898-8881","institution":"University College London","correspondingAuthor":false,"prefix":"","firstName":"Peter","middleName":"","lastName":"Lee","suffix":""},{"id":616516867,"identity":"6baafa76-7469-4fc8-aaa8-be1f6fe066ce","order_by":11,"name":"Manish Tiwari","email":"","orcid":"https://orcid.org/0000-0001-5143-6881","institution":"University College London","correspondingAuthor":false,"prefix":"","firstName":"Manish","middleName":"","lastName":"Tiwari","suffix":""}],"badges":[],"createdAt":"2026-03-26 19:35:57","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9237610/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9237610/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":106446166,"identity":"bfd89e06-3f39-429f-82e6-f1de79dd2f9e","added_by":"auto","created_at":"2026-04-08 15:34:30","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1073130,"visible":true,"origin":"","legend":"\u003cp\u003e\u0026nbsp;See image above for figure legend.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-9237610/v1/3a30f6aab865d8403a6df6ab.png"},{"id":106446167,"identity":"b99fd56f-6d92-41cf-8974-be7ae4866af0","added_by":"auto","created_at":"2026-04-08 15:34:30","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":274949,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Thermogravimetric analysis (TGA) profile and (b) differential scanning calorimetry (DSC) for tripropylene glycol diacrylate (TPGDA). (b)i Shows a subsection highlighter by (b), where the black box shows an endothermic dip and exothermic peak. (c)i-ii Schematic where a droplet of 50 wt. % dispersion in tripropylene glycol mono methyl ether (TPM) silver nanoparticle ink on Ti-6Al-4V coated tripropylene glycol d (TPGDA) treated with plasma coating at 1.35A was cured under four different temperatures (100, 150, 200 and 250°C ). (d) Scatter plot of the resistance against time for four different curing temperatures. (e) Optical images of the four different during times. All the scale bars are 600 µm.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-9237610/v1/f2cf84f6d79a625501e0b07b.png"},{"id":106446169,"identity":"8aa0f6e2-747c-4d35-8720-d0b4b9b3af7b","added_by":"auto","created_at":"2026-04-08 15:34:30","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":603376,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Optical imaging of the tip ends, showing the effect of the pulling velocity. Here the value stands for the scale unit of the puller it is related to the pulling velocity, but not the real value of pulling velocity, where (a)i 8 Ramp, (a)ii 12 and (a)iii 14. (b) Optical imaging of the tip ends, showing the effect of the Ramp. Here the value stands for the scale unit of the puller it is related to the heating temperature, but not the real value of temperature, where (b)i +10 Ramp, (b)ii +40 Ramp and (b)iii 70+ Ramp. (c)i-ii Plot showing velocity dependence of the tip ending tip size of glass capillary pulled by micropipette puller compared to ref.\u003csup\u003e36\u003c/sup\u003e. (d) Plot showing temperature dependence of the tip ending size of glass capillary pulled by micropipette puller compared to ref.\u003csup\u003e36\u003c/sup\u003e. (d) Schematic representation of the relative position of the X-ray beam shows the melt pool shape and heat affected zone for a protective layer of 1 mm (Supplementary Table 6,7 and 8 show the parameters used for the FEA simulation). Temperature in Celsius. (e) Optical images of four different sensors which includes commercial foil strain gauge with a polyamide film (PI) backing; direct ink write (DIW) printed strain gauge with 50 wt. % dispersion in tripropylene glycol monomethyl ether (TPM) silver nanoparticle ink with a PI backing; DIW printed strain gauge with 50 wt. % dispersion in TPM silver nanoparticle ink with glass fibre (GF) reinforced phenolic backing; and a Ti-6AI-4V base layer, tripropylene glycol diacrylate (TPGDA) backing and a sensor layer printed with 50 wt. % dispersion in TPM silver nanoparticle ink in respective order. (e) Is before embedding and (e)ii is after the embedding. Scale bars are 20 µm for (e)i and 0.25 mm for (e)ii. The resistance, R (\u003cimg width=\"9\" height=\"14\" src=\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAA0AAAAVCAMAAACqsJS4AAAAAXNSR0IArs4c6QAAAFdQTFRFAAAAAAAAAAA6AABmADpmADqQAGa2OgAAOmaQOma2OpDbZgAAZgA6ZjoAZrb/kDoAkNv/tmYAtmY6tpBmttv/tv//25A627aQ2////7Zm/9uQ//+2///bUbw+NwAAAAF0Uk5TAEDm2GYAAAAJcEhZcwAAFiUAABYlAUlSJPAAAAAZdEVYdFNvZnR3YXJlAE1pY3Jvc29mdCBPZmZpY2V/7TVxAAAAZUlEQVQoU62OyQ6AMAhEwa3uLS5V2/7/d1rAi1cjByYzmUcA+G3SahDbU+/FqdogmEYdlTvvwrEJpmfx6t5CtfDaT1bwOOgVErkUA8/Np5FTBiQCWFwcHSdHl51FzAQh4qy/fJkbU44EXEghs1AAAAAASUVORK5CYII=\"/\u003e) and power P (W) of the four strain gauges were recorded before embedding and after. \u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-9237610/v1/9ac6312758c80ee4d68cb044.png"},{"id":106724116,"identity":"280cda3a-73ad-4bbb-8e77-ec75240e5cc3","added_by":"auto","created_at":"2026-04-12 18:26:00","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":648733,"visible":true,"origin":"","legend":"\u003cp\u003eCytotoxicity test for four sensors (strain gauges). Sensor A which is a hybrid layer sensor with a Ti-6AI-4V base layer, tripropylene glycol diacrylate (TPGDA) dielectric layer and a sensor layer printed with 50 wt. % dispersion in tripropylene glycol monomethyl ether (TPM) silver nanoparticle ink. Sensor B is a polyamide film (PI) dielectric layer and a sensor layer printed with TMP silver nanoparticle ink. Sensor C is a glass fibre (GF) reinforced phenolic dielectric layer and a sensor layer printed with TMP silver nanoparticle ink. Sensor D is a commercial foil gauge sensor that has a PI backing. (a) (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) MTT assay showing cell viability of human dermal fibroblast (HDF) cell lines of the four strain gauges (sensor A, B, C and D) that were soaked in Phosphate buffered saline (PBS) for 3 and 21 days (including controls). (b) Fluorescence microscopy images of HDF cells were immersed with the four-strain gauge after 72 hours of incubation (see Supplementary Figure 6). All scale bars are 1050 µm. Validation of the sensor embedding process strain gauge sensor operation with comparison to bare strain gauges. (c) Mechanical testing set-up for monitoring of in situ strain gauges of the Ti-6AI-4V embedded parts. (d) Change of resistance divided by initial resistance against strain, where the gradient is the gauge factor (K). (d) stress-strain profile for the sensor comparing the bare strain gauges to the embedded strain gauges which include (e)i a commercial foil strain gauge with a polyamide film (PI) backing, (e)ii direct ink write (DIW) printed strain gauge with 50 wt. % dispersion in tripropylene glycol monomethyl ether (TPM) silver nanoparticle ink with a PI backing, (e)iii DIW printed strain gauge with 50 wt. % dispersion in TPM silver nanoparticle ink with glass fibre (GF) reinforced phenolic backing, and (e)iv a Ti-6AI-4V base layer, tripropylene glycol diacrylate (TPGDA) backing and a sensor layer printed with 50 wt. % dispersion in TPM silver nanoparticle ink.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-9237610/v1/bb42acc5831d8c21645c8cc9.png"},{"id":106724088,"identity":"6128a465-e4bc-4cdf-9b39-f3ef8b94c0b0","added_by":"auto","created_at":"2026-04-12 18:25:37","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":252158,"visible":true,"origin":"","legend":"\u003cp\u003e(a) A flow diagram describing the stages to achieve the sensor embedding process which includes (1) development of the four strain gauges that include a commercial foil gauge on a polyamide (PI) backing, a direct ink write (DIW) printed gauge with commercial PI, a DIW-printed gauge with glass fibre (GF) reinforced phenolic, and, a DIW-printed gauge with a thin-film tripropylene glycol diacrylate (TPGDA) dielectric deposited by roll-to-roll (R2R). (2) Strain gauges are characterised to analyse the wettability through contact angle measurements, Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). (3) Embedding stage where the four strain gauges were embedded in Ti-Al-4V component using laser powder bed fusion (LPBF). (4) The embedded and non-embedded strain gauges were evaluated to analyse the effect of embedding. (b) A schematic of the strain gauges embedded which consists of base layer, strain gauge which is deposited on the base layer and encapsulated in a cavity-like structure. (c) Once the gauges are embedded the embedded samples are tested using mechanical testing where continuous strain measurements are taken as shown by the schematic. (d) A schematic of the embedding process where powder is used as a protective layer to protect the sensor when the laser is scanning over the sensor to print the top wall. (e) A schematic summarising the three core components sensor embedding layers which includes the base layer which is made of Ti-6Al-4V, dielectric layer which is the barrier layer between the base layer and conductive layer and is composed of a polymer, and the sensing layer which is a conductive layer that is composed of a silver conductive nanoparticle ink.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-9237610/v1/88c1c44fb7a21defdb68c605.png"},{"id":106725935,"identity":"d33ab529-6184-41ee-91c7-3591a218577c","added_by":"auto","created_at":"2026-04-12 18:34:34","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3304426,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9237610/v1/a265e9ec-2204-41a7-9029-89352600b765.pdf"},{"id":106724057,"identity":"5394f922-3efa-4b94-8dcc-1181bf162f75","added_by":"auto","created_at":"2026-04-12 18:25:03","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":4266985,"visible":true,"origin":"","legend":"Supplementary Material","description":"","filename":"EmbeddedmultilayerstrainarchitecturescreateselfsensingmultifunctionaltitaniuminadditivemanufacturingNatureCommunicationMaterialsAlishaBhattSUPPLEMENTARY290326.docx","url":"https://assets-eu.researchsquare.com/files/rs-9237610/v1/85820815b7dc7caf07466cbf.docx"},{"id":106724104,"identity":"d77c7087-a299-4196-85d7-e6156b24fe29","added_by":"auto","created_at":"2026-04-12 18:25:53","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":506568,"visible":true,"origin":"","legend":"","description":"","filename":"Graphicalabstract.docx","url":"https://assets-eu.researchsquare.com/files/rs-9237610/v1/5183ddd48fc838aac2dcc8ec.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Embedded multilayer strain architectures create self-sensing multifunctional titanium in additive manufacturing","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eMetal components capable of internally monitoring strain are increasingly important for applications in aerospace structures\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, biomedical implants\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e, and structural health monitoring systems\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Conventional monitoring approaches rely on external sensors, which provide limited spatial resolution and cannot capture stress distributions within the material\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Embedding sensors directly during metal additive manufacturing (AM) offers a pathway to measure strain internally and in real time, enabling predictive maintenance and integration with digital twin frameworks in critical engineering systems\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. Titanium alloys such as Ti-6Al-4V are widely used in biomedical \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e and aerospace components \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e because of their high mechanical strength, corrosion resistance, and biocompatibility \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. However, integrating sensors within these alloys remain challenging because of their high melting temperature \u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e, low thermal conductivity, and the sensitivity of polymer dielectric materials \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e to localized laser heating during fabrication.\u003c/p\u003e \u003cp\u003ePrevious strategies for incorporating sensors in metallic structures include protective coating, cavity integration, or the use of prefabricated metallic sensing layers\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Although these approaches have shown promise, they often increase fabrication complexity, restrict design flexibility\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,1718\u003c/sup\u003e, and have primarily been demonstrated in alloys such as stainless steel 316L\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e or Inconel 718\u003csup\u003e21\u003c/sup\u003e. Commercial strain gauges typically consist of metallic foils mounted on polymer dielectric substrates, and their integration into titanium alloy components during laser powder bed fusion (LPBF) remains difficult\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. The extreme thermal gradients and rapid heating cycles associated with LPBF can lead to polymer degradation, delamination, or loss of electrical functionality, limiting the reliability of embedded sensing systems\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eDirect ink writing (DIW) provides a route to deposit functional materials with high spatial precision and flexible sensor geometries\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. Tripropylene glycol diacrylate (TPGDA) was selected as the dielectric layer because it can form uniform thin films compatible with roll-to-roll deposition (R2R)\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e, provides sufficient thermal stability under controlled curing conditions, and promotes adhesion with metallic nanoparticle inks used for strain sensing\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. Multilayer sensor architectures, where dielectric and conductive layers are independently optimized, can improve both resolution and durability under the thermal cycling conditions associated with LPBF processing\u003csup\u003e\u003cspan additionalcitationids=\"CR28\" citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. The combination of DIW printing and TPGDA dielectric layers therefore enables fabrication of multilayer polymer\u0026ndash;metal strain gauges compatible with metal additive manufacturing.\u003c/p\u003e \u003cp\u003eHere we present a strategy for embedding multilayer strain-sensing architectures within Ti-6Al-4V components fabricated by LPBF. A powder-mediated shielding layer is used to mitigate thermal exposure during laser processing, while DIW enables direct deposition of polymer\u0026ndash;metal sensing structures. The embedded sensors retain strain-sensing functionality under mechanical loading and exhibit cytocompatibility. These results establish a materials integration framework for embedding functional devices within additively manufactured metals, enabling the development of self-monitoring structural components for aerospace, biomedical, and intelligent manufacturing applications.\u003c/p\u003e"},{"header":"2. Results and Discussion","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Surface Roughness and Wettability of Tripropylene Glycol Diacrylate (TPGDA)\u003c/h2\u003e \u003cp\u003eWe selected TPGDA as a model dielectric to establish a transferable strategy for integrating printable polymer layers within metal substrates. TPGDA provides a processable thin film compatible with R2R deposition, enabling controlled investigation of surface modification and printing behavior relevant to a broader class of printable dielectrics. Importantly, the purpose of this study was to demonstrate a proof of concept for surface treatment and printing optimisation; therefore, the methodology and findings are expected to be transferable to other printable dielectric materials with a similar processing requirement. In this multilayer system, the dielectric surface governs both ink wettability and interfacial stability and is therefore critical for achieving high-resolution patterning and mechanical durability. The strain gauge compromises of a Ti-6Al-4V base layer, a TPGDA dielectric layer, and a sensing layer formed from commercial \u003cem\u003e50 wt. %\u003c/em\u003e silver nanoparticle dispersion in tripropylene glycol mono methyl ether (TPM) ink, hence the surface morphology of the dielectric is critical for both printability and durability. The TPGDA dielectric layer was deposited on Ti-6Al-4V using R2R vacuum web coating facility.\u003c/p\u003e \u003cp\u003eAtomic force microscopy (AFM) imaging (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea) shows that TPGDA deposition preserves the underlying substrate roughness, but the as-deposited surface exhibits insufficient wettability for DIW \u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. Therefore, plasma and electron beam irradiation (EBI) treatments were applied to modify the TPGDA surface and improve its printability. Increasing the plasma current enhanced surface etching and produced pronounced peaks, whereas EBI generated a more symmetrical distribution of valleys and peaks, resulting in a smoother and more uniform surface morphology. Increasing the plasma current enhanced etching and produced peaks, whereas EBI generated a more symmetrical distribution of valleys and peaks, yielding a smoother and more uniform surface. Quantitative roughness parameters (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb) confirmed that both EBI and low current plasma yielded lower surface roughness (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{S}_{a}\\)\u003c/span\u003e\u003c/span\u003e) and root mean square (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:RMS\\)\u003c/span\u003e\u003c/span\u003e) values in comparison to the higher plasma, suggesting their suitability for DIW .\u003c/p\u003e \u003cp\u003eSpectroscopic analysis confirmed these observations. Fourier Transform Infrared spectroscopy (FTIR) spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec) showed increase in the intensity of the ester carbonyl (C\u0026thinsp;=\u0026thinsp;O) stretching band at approximately 1730 cm⁻\u0026sup1; with increasing plasma current, indicating enhanced surface polarity and wettability. This band is characteristic of the acrylate groups present in TPGDA and its polymerized network. The increase in C\u0026thinsp;=\u0026thinsp;O intensity is interpreted as evidence of increased surface oxidation/polar functionality following plasma treatment, which can enhance the surface polarity of the cured polymer coating and improve wettability for subsequently deposited layers, such as TPM silver nanoparticle ink. It should be noted that this interpretation relates to the surface properties of the cured polymer coating rather than the initial wetting of the monomer on the substrate prior to curing. In addition, the FTIR peak at approximately 810 cm⁻\u0026sup1;, corresponding to the out-of-plane bending of the acrylate C\u0026thinsp;=\u0026thinsp;C bond, is commonly used to assess the amount of residual unsaturation and therefore the degree of cure of the coating. A reduction in the intensity of this peak indicates a higher extent of polymerization. Similarly, EBI modified the surface chemistry of the TPGDA layer, increasing surface polarity and correlating with the observed reduction in infrared (IR) transmittance. Both plasma and EBI improved the surface energy and promoted ink adhesion. However, increasing plasma current also increased surface roughness, which can negatively affect high resolution printing.\u003c/p\u003e \u003cp\u003eThe practical consequence of these effects was captured by TPM silver nanoparticle ink contact angle measurements (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). Low-current plasma produced moderate spreading and stable contact angles, while high current plasma and EBI induced extensive spreading and very low contact angles due to the combined effects of polarity and morphology. Excessive wettability, however, led to ink bleeding and compromised printing resolution (Supplementary Fig.\u0026nbsp;2). Overall, low current plasma treatment achieved the optimal balance of smooth morphology, sufficient polarity, and controlled wettability, enabling both reliable adhesion and high-resolution strain gauge patterning. These results establish that controlled tuning of dielectric surface chemistry and morphology is essential for integrating conductive features within multilayer architectures and provide a generalizable framework for printable polymer\u0026ndash;metal interfaces in AM environments.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Thermal Constraints of the Dielectric Layer Define Curing Conditions for Nanoparticle Strain Gauges\u003c/h2\u003e \u003cp\u003eWe establish the thermal constraints governing integration for the polymer dialectic and conductive ink within the LPBF environment (see Supplementary Fig.\u0026nbsp;3 for the methodology). Thermogravimetric analysis (TGA) revealed progressive weight loss beginning at ~\u0026thinsp;220\u0026deg;C, indicative of polymer degradation (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). Differential scanning calorimetry (DSC) analysis further identifies a glass transition at ~\u0026thinsp;260\u0026deg;C, crystallisation at ~\u0026thinsp;280\u0026deg;C, and complete melting at ~\u0026thinsp;350\u0026deg;C (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). Together these results define a narrow thermal processing window, in which exposure temperatures above ~\u0026thinsp;200\u0026deg;C leads to irreversible damage and change in the polymer network.\u003c/p\u003e \u003cp\u003eWe then examine the curing behaviour of the TPM silver nanoparticle ink under these constraints, droplets were deposited onto plasma-treated TPGDA films and furnace-cured between 100\u0026ndash;250\u0026deg;C (Fig.\u0026nbsp;2ci-ii). Resistance decreased linearly with curing time across all conditions, with faster reduction at higher temperatures due to enhanced conductivity (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed). However, temperatures\u0026thinsp;\u0026ge;\u0026thinsp;200\u0026deg;C, induce microstructural degradation characterised by pore formation within the conductive layer (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee). This behaviour is consistent with accelerated solvent evaporation and reduced mechanical robustness. The maximum thermal tolerance of the ink was ~\u0026thinsp;250\u0026deg;C for 8500 s before degradation was evident.\u003c/p\u003e \u003cp\u003eWhile elevated temperatures promote rapid conductivity development, they also approach degradation threshold of both the dielectric and conductive layers. We therefore identity curing at 150\u0026deg;C for 3800 s, which produced strain gauges with ~\u0026thinsp;350 Ω resistance comparable to commercial devices \u003csup\u003e\u003cspan additionalcitationids=\"CR33 CR34\" citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e, while avoiding degradation of both the dielectric and the conductive layer.\u003c/p\u003e \u003cp\u003eThese results establish the additional requirements for a protective powder layer during laser scanning and a carefully controlled curing protocol to ensure device stability and performance. These results motivate the incorporation of a powder-mediated shielding strategy to mitigate transient thermal exposure, enabling retention of both dielectric integrity and conductive functionality during embedding.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. High-Resolution Strain Gauge Embedding via Printing and Thermal Management Strategies\u003c/h2\u003e \u003cp\u003eEmbedding high-resolution strain gauges into LPBF fabricated Ti-6Al-4V parts requires careful coordination of printing precision, thermal management, and material selection. The process begins with the micropipette nozzle, where tip geometry directly affects printing fidelity. Figure\u0026nbsp;3ai-iii shows the nozzle tip end pulled by the P-1000 micropipette puller (P-1000), demonstrating that the pull velocity influences the final tip size. Figure\u0026nbsp;3bi-iii shows the tip end where the heating temperature is indirectly defined as the ramp temperature which is not the real temperature. Using the P-1000 puller, we found that decreasing the ramp temperature and pull velocity produced smaller, more reproducible tips, whereas higher pull velocities increased the tip size due to extended neck reshaping (Fig.\u0026nbsp;3ci-ii). Tip size variation remained below 5% across all conditions, consistent with ref.\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e, ensuring both high spatial resolution (\u0026le;\u0026thinsp;10 \u0026micro;m) and nozzle durability required for reliable conductive ink deposition. Nozzle tip breakage and bleeding were observed at low pull velocities (of 14). Based on these results, a ramp of 65\u0026thinsp;+\u0026thinsp;and a pull velocity of 12 were selected to achieve durable, high-resolution nozzle (Supplementary Fig.\u0026nbsp;4).\u003c/p\u003e \u003cp\u003eThe printing process is followed by embedding under LPBF conditions, where thermal exposure can compromise strain gauge integrity. A 1 mm layer of Ti-6Al-4V powder was applied over the gauges to act as a thermal barrier. Simulations indicate that, although surface powder temperatures reach\u0026thinsp;~\u0026thinsp;3347\u0026deg;C during laser scanning, the thermal effect near the embedded gauges is reduced to ~\u0026thinsp;25\u0026deg;C, effectively mitigating thermal degradation (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed). Although the thermal simulation presented indicated that a thinner powder layer could reduce the peak temperature at the strain gauge, a 1 mm layer was selected to ensure a sufficient safety margin and account for any discrepancies in powder spreading and potential laser exposure. This protective layer also alleviates stress concentrations at the embedding site, helping preserve gauge structure and function. The thermal model represents transient heat conduction during the laser scanning process. A first order estimate of the thermal penetration depth is obtained using \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:L\\approx\\:\\:\\sqrt{\\alpha\\:\\tau\\:}\\)\u003c/span\u003e\u003c/span\u003e \u003csup\u003e37\u003c/sup\u003e, where \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\alpha\\:\\)\u003c/span\u003e\u003c/span\u003e is the thermal diffusivity of the powder and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\tau\\:\\)\u003c/span\u003e\u003c/span\u003e is the laser interaction time. Using the process parameters (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:v=\\)\u003c/span\u003e\u003c/span\u003e 1.2 m/s, see supplementary methods), the estimated penetration depth is on the order of ~\u0026thinsp;10 \u0026micro;m, which is significantly smaller than the 1 mm powder protective layer. This analytical estimate is consistent with the FEM results, which show minimal rise in temperature at the location of the sensor. The selected 1 mm powder layer will provide substantial additional safety margin to ensure sensor protection against any potential local thermal fluctuations during the laser scanning process.\u003c/p\u003e \u003cp\u003eThe interplay of nozzle precision and thermal protection was further tested across four strain gauge configurations: commercial foil with PI backing, DIW printed serpentine gauges with PI backing, glass fibre (GF) -reinforced phenolic backing, and the TPGDA backing (Fig.\u0026nbsp;3ei-ii). PI-backed gauges failed due to thermal deformation and adhesive degradation, whereas GF-reinforced phenolic and TPGDA-backed gauges survived, demonstrating that material selection shows post-embedding success. Although PI is known for its high thermal stability \u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e,\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e compared to many other polymers \u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e, failures in this case are likely to do with the LPBF processing conditions rather than the thermal limit of the material. The rapid heating and cooling cycles, steep thermal gradients and localised energy input during the process could result in interfacial stresses and degradation of the adhesive layer bonding the gauge to the substrate, which as a result leads to delamination.\u003c/p\u003e \u003cp\u003eMeasurements before and after embedding showed resistance decreases (Δ\u003cem\u003eR\u003c/em\u003e\u0026thinsp;=\u0026thinsp;134 Ω for phenolic, Δ\u003cem\u003eR\u003c/em\u003e\u0026thinsp;=\u0026thinsp;144 Ω for TPGDA), consistent with additional sintering of the silver nanoparticle ink induced by residual thermal exposure. These results confirm that, when printing resolution, thermal shielding, and backing material are carefully tuned, functional strain gauges can be reliably integrated into metal parts (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee).\u003c/p\u003e \u003cp\u003eTogether, these findings reveal a pathway from nozzle design to sensor survival: precise nozzle tips enable accurate deposition, the powder layer protects against LPBF thermal effects, and appropriate backing materials preserve electrical and structural integrity. This integrated approach provides a practical framework for embedding high-resolution, durable sensors in metal components fabricated via LPBF, highlighting the critical interactions between printing parameters, thermal management, and material choice. Collectively, this establishes a design framework for integrating functional sensing architectures within AM metals, linking processing parameters to device survival and performance. Although thinner powder layers may also reduce thermal exposure, a 1 mm layer was selected here to maximize process robustness and ensure reliable protection against local variations in powder packing and laser-induced heating.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Integrated Fabrication and Performance of Embedded Strain Gauges\u003c/h2\u003e \u003cp\u003eThe embedded strain gauges demonstrated both cytocompatibility and functional integrity when integrated into LPBF-fabricated Ti-6Al-4V parts, highlighting their potential for biomedical and structural sensing applications. Four types of strain gauges DIW printed sensors with TPGDA, PI, and GF-reinforced phenolic backings, and commercial foil sensors were evaluated for biocompatibility by immersing them in PBS for three days and three weeks. Although the sensor was encapsulated within the Ti-6Al-4V structure, this assessment was performed to determine whether any leaching of components from the embedded multilayer sensor system (e.g., dielectric layers or conductive materials) could affect cell viability.\u003c/p\u003e \u003cp\u003eHigh cell viability (80\u0026ndash;90%) was observed across all sensors (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea), with predominantly elongated, healthy fibroblast cells confirmed by fluorescence imaging (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb, Supplementary Fig.\u0026nbsp;6). The Ti-6Al-4V base layer, dielectric layers (TPGDA, PI, GF-reinforced phenolic), and sensor layers (TPM silver nanoparticle ink or constantan alloy) collectively exhibited minimal cytotoxicity, consistent with prior reports \u003csup\u003e\u003cspan additionalcitationids=\"CR42\" citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. These results indicate that the multilayer sensor constructs are potentially suitable for in vivo applications, though additional long-term biocompatibility studies would be required for clinical use.\u003c/p\u003e \u003cp\u003eTo assess functional performance, the same strain gauges were embedded in Ti-6Al-4V parts using a 1 mm powder protective layer during LPBF and compared to bare gauges on a substrate. Mechanical testing under three-point bending revealed that all sensors retained their strain-sensing capability (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec), with gauge factors (K) increasing slightly after embedding due to localized thermal-induced sintering of the TPM silver nanoparticle ink. This demonstrates that the LPBF process can embed DIW printed sensors while inducing partial curing, a slight densification of the conductive ink that improves electrical connectivity without complete degradation of the dielectric or backing layer (Fig.\u0026nbsp;4di-iv). This demonstrates that the LPBF process can both embed and partially cure DIW printed sensors without complete degradation. The GF-reinforced phenolic and TPGDA-backed sensors survived the embedding process, while PI-backed and commercial foil sensors were prone to thermal-induced performance variations. Some fluctuations in the stress-strain curves were observed for the surviving sensors, likely due to laser-induced thermal effects causing minor resistance changes and Wheatstone bridge imbalance (Fig.\u0026nbsp;4ei-iv). The overall stress-strain response was preserved, confirming the feasibility of embedding functional strain gauges using a powder shielding approach.\u003c/p\u003e \u003cp\u003eThese results establish a linked framework for integrating functional, biocompatible strain gauges into LPBF-fabricated metal parts. High cell viability demonstrates suitability for biomedical applications, while mechanical testing confirms that thermal protection via powder layers and appropriate backing materials preserves strain-sensing performance. Optimizing nozzle geometry, powder thickness, and backing material selection collectively ensures that embedded sensors maintain both biological safety and functional integrity, providing a robust strategy for next-generation smart implants and structural monitoring devices. Together these finding indicate that careful selection of powder thickness, backing material, and sensor design allows embedded sensors to maintain both functional integrity and cytocompatibility, providing a methodology for next generation smart implants and structural monitoring devices. More broadly, they establish design criteria linking backing material, thermal exposure, and interfacial stability, providing a framework for embedding multifunctional devices within structural metals for biomedical and sensing applications. These results support the cytocompatibility of the embedded sensor material system under the conditions tested, while further long-term biological evaluation will be required to assess suitability for clinical implantation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3. Methodology","content":"\u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows a flow chart that summarizes the sensor embedding methodology. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea shows four types of strain gauges that were embedded using LPBF, each consisting of a dielectric backing and a sensing layer: (1) a commercial foil gauge on a PI backing, (2) a DIW printed gauge with commercial PI, (3) a DIW printed gauge with GF-reinforced phenolic, and (4) a DIW printed gauge with a thin-film TPGDA dielectric deposited on a moving substrate in a R2R facility. The sensing layer for the DIW printed gauges was deposited using TPM silver nanoparticle ink. Full material specifications, particle sizes, and supplier details are provided in Supplementary. Commercial and DIW gauges with PI or GF-reinforced phenolic backings were bonded to Ti-6Al-4V substrates using adhesive. For TPGDA thin films, R2R deposition and roller compression were used to achieve adhesion. Deposition rates, curing conditions, and roller parameters are outlined in the Supplementary Methods and Supplementary Fig.\u0026nbsp;7.\u003c/p\u003e \u003cp\u003eLPBF was used to embed the sensors within Ti-6Al-4V. Samples were printed under an argon atmosphere using an Aconity Lab system with optimised process parameters. A laser power of 190 W and scan speed of 1.2 m/s were maintained throughout the build. The full process map, hatching strategy, and powder specifications are provided in Supplementary Tables\u0026nbsp;6\u0026ndash;8.\u003c/p\u003e \u003cp\u003eStrain gauge designs were printed onto dielectric layers via DIW, using custom nozzles and a controlled translational stage. Sensors were cured by thermal sintering between 100\u0026ndash;250\u0026deg;C. Details of nozzle manufacturing, scanning electron microscopy (SEM) imaging, printing speeds, and curing times are provided in Supplementary Table\u0026nbsp;5 and Supplementary Fig.\u0026nbsp;4. Surface and material characterisation was carried out by atomic force microscopy, FTIR, DSC, TGA, and contact angle measurements to assess dielectric properties and printability. Instrument models, acquisition parameters, calibration details, and supplementary figures (Supplementary Methods) provide full characterisation protocols.\u003c/p\u003e \u003cp\u003eTwo embedding strategies were used: (1) cold embedding with powder protection for PI- and phenolic-based sensors, and (2) a hybrid process combining R2R and DIW for TPGDA-based sensors. Schematics of both workflows are summarised by Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb-e. Stepwise embedding protocols are provided in Supplementary Fig.\u0026nbsp;7 and Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed. Thermal simulations were performed in Abaqus to analyse heat transfer through the 1 mm protective powder layer. Mesh details, Goldak\u0026rsquo;s model parameters \u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e, and material constants are summarised in Supplementary Tables\u0026nbsp;6\u0026ndash;8 and Supplementary Fig.\u0026nbsp;5.\u003c/p\u003e \u003cp\u003eMechanical performance was validated using three-point bending tests, while biocompatibility was assessed on human dermal fibroblasts (HDF) cell lines using LIVE/DEAD and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Complete assay protocols, incubation conditions, and statistical analyses are detailed in Supplementary Methods and Supplementary Fig.\u0026nbsp;6. Strain signals from embedded gauges were recorded using a Wheatstone bridge circuit connected to Arduino-based wireless data acquisition shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed. Circuit diagrams, component specifications, and software versions are shown in Supplementary Fig.\u0026nbsp;8.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eWe have demonstrated a strategy for creating multifunctional titanium by embedding strain-sensing architectures directly within Ti-6Al-4V during laser powder bed fusion. By combining direct printing of multilayer polymer\u0026ndash;metal gauges with a Ti-6Al-4V powder layer for thermal protection, we show that thermally sensitive sensing elements can survive incorporation into a high-temperature metal additive manufacturing process. Among the architecture evaluated, TPGDA- and GF phenolic-backed printed sensors retained electrical functionality and strain-sensing performance after embedding, whereas polyimide-based configurations were more susceptible to thermal and interfacial failure. Rather than presenting a single device optimization, this study establishes a materials integration framework linking dielectric surface properties, conductive ink curing behavior, backing-layer selection, and powder-mediated thermal shielding to the successful embedding of functional sensors in LPBF titanium. Although TPGDA and TPM silver nanoparticle ink were used here as model materials, the design principles identified namely control of dielectric surface chemistry and morphology, management of curing-temperature limits, and use of powder-mediated thermal shielding are expected to be transferable to other printable polymer\u0026ndash;metal sensor systems.\u003c/p\u003e \u003cp\u003eThese results show that metal additive manufacturing can be extended beyond structural fabrication to produce titanium components with built-in sensing capability. More broadly, the work establishes a materials-integration framework in which interfacial design, curing conditions and powder-mediated thermal shielding are jointly used to incorporate functional devices into structural metals. This approach provides a foundation for self-monitoring metallic systems in aerospace, biomedical and intelligent manufacturing applications. Future work should focus on broadening the range of compatible dielectric and conductive materials, improving long-term reliability and cyclic stability, and extending the strategy to other sensing modalities and metal additive manufacturing platforms. These findings are relevant to application areas including aerospace structures, biomedical devices, and intelligent manufacturing, although further domain-specific validation will be required for end-use deployment.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eHegazy, M. A., Nada, N., Elhaes, H., Ibrahim, M. A. \u0026amp; Ezzat, H. A. 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Manuf.\u003c/em\u003e \u003cstrong\u003e46\u003c/strong\u003e, (2021).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"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":"Embedded strain sensors, Titanium additive manufacturing, Laser powder bed fusion, Direct printing of functional inks, Self-monitoring metal components, Roll-to-roll deposition","lastPublishedDoi":"10.21203/rs.3.rs-9237610/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9237610/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Multifunctional structural metals capable of monitoring their internal mechanical state are increasingly important for aerospace, biomedical, and intelligent manufacturing applications, yet integrating thermally sensitive sensing architectures into high-temperature metal additive manufacturing remains challenging. Here we show that multilayer strain sensing architectures can be embedded directly within Ti-6Al-4V during laser powder bed fusion by combining high-resolution printing of polymer\u0026ndash;metal gauges with powder mediated thermal protection. We evaluate four sensor architectures, including commercial foil gauges and directly printed gauges with different dielectric layers, and identify material stacks that survive embedding while retaining electrical functionality. The embedded sensors preserve strain sensing performance under mechanical loading, maintain structural integrity, and exhibit cytocompatibility. These results establish a route to multifunctional titanium with internal sensing capability and provide a materials integration framework for embedding functional devices within additively manufactured metals.","manuscriptTitle":"Embedded multilayer strain architectures create self-sensing multifunctional titanium in additive manufacturing","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-08 15:34:25","doi":"10.21203/rs.3.rs-9237610/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"communications-materials","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"commsmat","sideBox":"Learn more about [Communications Materials](https://www.nature.com/commsmat/)","snPcode":"","submissionUrl":"","title":"Communications Materials","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Communications Series","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"3d81c662-0afb-416a-b37b-e650edb1bbd6","owner":[],"postedDate":"April 8th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":65606728,"name":"Physical sciences/Materials science/Materials for devices/Sensors and biosensors"},{"id":65606729,"name":"Physical sciences/Nanoscience and technology/Nanoscale devices/Sensors"}],"tags":[],"updatedAt":"2026-04-29T09:00:26+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-08 15:34:25","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9237610","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9237610","identity":"rs-9237610","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}