Wearable Safeguarding Leather Composite with Excellent Sensing, Thermal Management, and Electromagnetic Interference Shielding

Strong and Anti-Impact Multi-Functional Elastomer via Hierarchical Hydrogen Bonding Design

Despite extensive research on enhancing the strength, toughness, or impact resistance of elastomers, materials that simultaneously integrate these properties remain elusive. In this work, a multifunctional elastomer is developed with high strength, superior toughness, and excellent impact resistance by designing multiscale structures. The synergistic coupling of strong and weak hydrogen bonds, rigid ring-flexible chain coordination, and precise control of hard/soft block ratio enabled the development of an optimized multiscale architecture tailored for superior performance, achieving a tensile strength of 84 MPa and a toughness of 450 MJ m⁻3, while maintaining excellent impact resistance across varying strain rates. Additionally, the incorporation of hindered urea dynamic covalent bonds and hydrogen bond-induced localized conjugation effect impart thermal adhesion and fluorescence capabilities, broadening the material's functional application scenarios. This multiscale molecular design strategy not only facilitates the tailoring of high-performance materials but also provides new insights into the structure-property relationships in elastomers.

Hollow-structured elastic aerogel fibers enabling simultaneous EMI shielding, infrared stealth, and thermal management

Electromagnetic interference (EMI) shielding materials that also possess thermal management capabilities are crucial for safeguarding sensitive information against interception or disruption in electronic countermeasure applications. Furthermore, these materials are adept at maintaining a stable internal temperature within their structural framework, even under the most severe cold conditions. In this work, we fabricated elastic hollow porous polyurethane (HPU) fibers incorporating silver-coated copper nanosheets (Cu@Ag NS) as fillers, which exhibit low mid-infrared emissivity and exceptional electrical conductivity. These fibers were subsequently woven into HPU textile using a shuttle weaving technique, resulting in the textile with superior EMI shielding and excellent thermal management properties. The results indicate that the HPU textile can attain an adjustable EMI shielding effectiveness (SE) ranging from 21.11 to 57.53 dB, depending on the angle between HPU textile and the electric field of the incident electromagnetic wave. The HPU textile exhibits a thermal conductivity of 0.06 Wm-1K-1, offering excellent thermal insulation. Moreover, it demonstrates an elongation of 490 %, underscoring its exceptional flexibility. These outstanding EMI shielding capabilities, combined with its adaptable thermal response and superior thermal management properties, make the HPU textile highly appropriate for use in wearable devices and architectural applications.

Interface Engineering Assisted 3D Printing of Silicone Composites with Synergistically Optimized Impact Resistance and Electromagnetic Interference Shielding Effectiveness

Silicone composites have been universally employed in smart devices, flexible electronics, and mechanical metamaterials. However, it remained challenging to develop 3D printable silicone composites with desirable mechanical and electrical properties. Here, an interface engineering strategy is reported, developing heterointerfacial silver-coated hollow glass microspheres (SHGMs), which are integrated with polydimethylsiloxane (PDMS) for 3D printing of impact-resistant, highly conductive, and mechanically robust SHGMs-PDMS (SHP) composites. SHP simultaneously achieves high compression modulus (12.65 MPa), substantial energy dissipation density (1.58 × 106 N m-2 at 50% strain), excellent conductivity (2.55 × 103 S m-1), and long-period robustness. SHP presents extraordinary impact resistance under dynamic impacts, reaching a considerable energy dissipation of 1.91 kJ m-1 at an incident velocity of 192.3 m s-1. More importantly, SHP with 2 mm in thickness achieves an ultraefficient electromagnetic interference (EMI) effectiveness of 92.5 dB, which is among that of state-of-the-art silicone and its derivatives, and can maintain favorable shielding efficiency (>70 dB) after undergoing mechanical excitations. Moreover, the formability enables it to fabricate delicate structures with a negative Poisson's ratio, ensuring adaptive fit and thus providing complete protection for individuals. This work paves an effective way to rapidly manufacture silicone composites with expected functions for new-generation protective devices.

A Universal Toughening and Energy-Dissipating Strategy for Impact-Resistant 3D-Printed Composites

3D-printed polymer-based composites are promising for various engineering applications due to high strength-to-weight ratios and design flexibility. However, conventional matrix materials, such as polylactic acid and epoxy resin, often exhibit brittleness and limited impact resistance (< 10 kJ m- 2). Herein, a universal strategy is reported for enhancing the ductility and impact energy absorption of 3D-printed composites by leveraging the dynamic crosslinking of B─O dative bonds. To validate its effectiveness, a smart composite (PLA/SSG) comprising shear-stiffening gel fillers embedded in a polylactic acid matrix is designed and its rate-dependent mechanical adjustability along with 3D printability is evaluated. The resulting composite shows significant improvements in impact resistance, ductility, and strength-ductility balance. Specifically, the multiple crack and localized plastic yielding of polylactic acid matrix induced by shear-stiffening gel fillers enables PLA/SSG with a 40-times increase in ductility; the "soft-hard" phase transition of shear-stiffening gel induced by B─O bonds endows PLA/SSG with a 330% improvement in impact energy absorption. This B─O bonds-inspired strategy provides a universal approach for printing smart impact-resistant composites and structures.

Conductive Textile Embedded with Bioinspired Wettability for Prolonged and Energy Efficient Thermal Management

The design of electrically conductive textiles appears to be a promising approach to combat the existing challenge of deaths caused by severe cold climates around the globe. However, reports on the scalable fabrication of tolerant conductive textiles maintaining a low electrical resistance with an ability for unperturbed and prolonged performance are scarce. Here, a breathable and wrappable water-repellent conductive textile (water-repellent CT) with electrothermal and photothermal conversion abilities at low external voltage and in weak solar light is introduced, respectively. In the current approach, less carbon-containing silver nanowires (AgNWs) are selected to spray deposit on a commercially available woven textile to attend a uniform and highly conductive network over a large dimension. The subsequent spray deposition of a reaction mixture of selected small molecules prevents aerial oxidation of deposited AgNWs even at elevated temperatures and provides bioinspired extreme water-repellence. Thus, it maintains an unperturbed performance even when exposed to different aqueous environment. Using the scalability of current approach and durability of prepared water-repellent CT, relevant wearable devices are derived to demonstrate personal heat management ability with rechargeable and portable battery for prolonged duration in severely cold conditions. Thus, the prepared water-repellent CT enabled an energy-efficient and "wrappable" heating, providing a basis for various potential applications.

Full-fiber triboelectric nanogenerators with knitted origami structures for high impact resistance intelligent protection fabric

Next-generation fabrics with excellent protection and intelligent sensing abilities will be beneficial to protect the elderly from accidents, as the ageing population will be a global challenge in the next decade. However, for widely used techniques such as fabric coating and multi-layer compositing, maintaining a balance between comfortability, stable anti-impact protection, and multi-function such as intelligent monitoring remains elusive. Herein, a full-fiber composite yarn with triboelectric ability was developed, which was then woven into an origami-structured knitted fabric (OSKF). Due to the coaxial torsional structure, the composite yarn exhibited outstanding fracture strength (219.18 MPa). The full-fiber multi-scale structure design endowed the OSKF with significantly improved energy absorption capacity (absorbing > 85% of the applied force) and the desired self-powered sensing performance without affecting the comfortability. The OSKF also had a unique ability to respond to various hazardous situations, such as external mechanical force stimuli, cutting by a sharp object, and accidental falls. This work sheds light on a new path toward the design of next-generation smart protection wearables based on knitted fabric structure design-based full-fiber materials.

Multi-performance sodium alginate-based composite films for sensing and electromagnetic shielding

As science and technology progress swiftly, the demand for high-performance composite films designed to shield against electromagnetic interference (EMI) and for strain sensing applications has significantly increased, making these films essential components for the future generation of smart wearable electronics. However, designing and developing multifunctional flexible composite films remains a considerable challenge. This study employed vacuum-assisted filtration techniques combined with calcium ion cross-linking to create multifunctional MXene/sodium alginate/liquid metal (MSL) composite films exhibiting exceptional EMI shielding and strain sensing capabilities. The mechanical strength of the MSL composite films was optimized by implementing continuous hydrogen bonding and ionic interactions among MXene, sodium alginate, liquid metal (LM), and calcium ions, resulting in a tensile strength of 71.71 MPa. The composite film exhibits excellent electromagnetic absorption properties, resulting in an exceptional EMI shielding efficacy of 50.61 dB and a specific shielding effectiveness value of 7563 dB·cm2·g-1. This is due to the heterogeneous interface between MXene and LM nanoparticles. Furthermore, the composite film exhibits favorable electrothermal and photothermal conversion capabilities. The film can be a flexible sensor to detect human motion, contingent on the conductive network between MXene and LM. This research illustrates the potential of multifunctional MSL composite films for EMI shielding and human motion monitoring, offering a promising pathway for creating adaptable wearable electronics in challenging electromagnetic conditions.

New Carbon Materials for Multifunctional Soft Electronics

Soft electronics are garnering significant attention due to their wide-ranging applications in artificial skin, health monitoring, human-machine interaction, artificial intelligence, and the Internet of Things. Various soft physical sensors such as mechanical sensors, temperature sensors, and humidity sensors are the fundamental building blocks for soft electronics. While the fast growth and widespread utilization of electronic devices have elevated life quality, the consequential electromagnetic interference (EMI) and radiation pose potential threats to device precision and human health. Another substantial concern pertains to overheating issues that occur during prolonged operation. Therefore, the design of multifunctional soft electronics exhibiting excellent capabilities in sensing, EMI shielding, and thermal management is of paramount importance. Because of the prominent advantages in chemical stability, electrical and thermal conductivity, and easy functionalization, new carbon materials including carbon nanotubes, graphene and its derivatives, graphdiyne, and sustainable natural-biomass-derived carbon are particularly promising candidates for multifunctional soft electronics. This review summarizes the latest advancements in multifunctional soft electronics based on new carbon materials across a range of performance aspects, mainly focusing on the structure or composite design, and fabrication method on the physical signals monitoring, EMI shielding, and thermal management. Furthermore, the device integration strategies and corresponding intriguing applications are highlighted. Finally, this review presents prospects aimed at overcoming current barriers and advancing the development of state-of-the-art multifunctional soft electronics.

High-Precision Printing Sandwich Flexible Transparent Silver Mesh for Tunable Electromagnetic Interference Shielding Visualization Windows

Flexible transparent conductive films (FTCFs) with electromagnetic interference (EMI) shielding performance are increasingly crucial as visualization windows in optoelectronic devices due to their capabilities to block electromagnetic radiation (EMR) generated during operation. Metal mesh-based FTCFs have emerged as a promising representative in which EMI shielding effectiveness (SE) can be enhanced by increasing the line width, reducing the line spacing, or increasing mesh thickness. However, these conventional approaches decrease optical transmittance or increase material consumption, thus compromising the optical performance and economic viability. Hence, a significant challenge still remains in the realm of metal mesh-based FTCFs to enhance EMI SE while maintaining their original optical transmittance and equivalent material usage. Herein, we propose an innovative symmetric structural optimization strategy to create silver mesh-based sandwich-FTCFs with arbitrary customized sizes through high-precision extrusion printing technology for tunable EMI shielding performance. The meticulous adjustment of xy-axis offsets and printing starting point ensures perfect alignment of the silver mesh on both sides of the transparent substrate. This approach yields sandwich-FTCFs with optical transmittance equivalent to single-layer-FTCFs under identical parameters while simultaneously achieving up to 40% enhanced EMI SE. This improvement stems from the synergistic effect of multiple internal reflections and wave interference between the symmetric silver meshes. The excellent shielding performance of sandwich-FTCFs is evidenced through effectively blocking electromagnetic waves from common devices such as mobile phones, Bluetooth earphones, and smartwatches. Our work represents a significant advancement in balancing optical transmittance, EMI SE, and material efficiency in high-performance and cost-effective FTCFs.

Robust Treble-Weaving Wearable Textiles for Pressure and Temperature Monitoring in Harsh Environments

Wearable sensing textiles with continuous temperature monitoring, tactile feedback, and motion perception are highly desirable for personal safeguarding in extreme environments, such as fire scenes and extreme sports. However, it remains challenging for current wearable sensors to maintain reliable performance and provide point-of-care monitoring in harsh environments, such as high- and low-temperature or high-humidity conditions. Herein, a robust temperature and pressure sensing textile (TPST) with a hierarchical triple-weaving structure is developed using industrial weaving technology. The well-engineered interlacing configuration of the polyimide binding yarns in the triple-weaving structure tightly solidifies the carbon-based sensing yarns between two weaving layers, forming an integrated textile sensing array. The TPST not only exhibits excellent sensing sensitivity, reliability, and rapid response to pressure and temperature stimuli but also shows robust mechanical properties, flame resistance, and wearing comfort. Moreover, we demonstrate the application of the TPST for continuous temperature monitoring, human motion mapping, and vital sign monitoring. This technology offers significant potential for enhancing autonomous rescue operations and defense wearables.

Hybridizing Shear-Stiffening Gel and Chemically-Strengthened Ultrathin Glass Sheets for Flexible Impact-Resistant Armor

Traditional anti-impact armors and shields are normally made of stiff and hard materials and therefore deficient in flexibility. This greatly limits their applications in protecting objects with complex geometries or significant deformability. Flexible armors can be developed with the application of hard platelets and soft materials, but the lower rigidity of the flexible armors renders them incapable of providing sufficient resistance against impact attacks. To address the inherent conflict between flexibility and impact resistance in traditional armors, here, a composite is developed by hybridizing a shear-stiffening gel as the matrix and chemically-strengthened ultrathin glass sheets (CSGS) as the reinforcement. The resulting laminate, termed PCCL, exhibits both high flexibility and high impact resistance. Specifically, at low strain rates, the high ductility of the gel combined with the high flexural strength of the CSGS enables the PCCL to undergo considerable deformation; at high strain rates, on the other hand, the shear stiffening behavior of the gel matrix endows the PCCL with excellent impact resistance manifested by its high performance in energy absorption and high rigidity. With the combination of high flexibility and high impact resistance, the PCCL is demonstrated to be an ideal armor for protecting curved vulnerable objects from impact attacks.

Bioinspired Flexible Kevlar/Hydrogel Composites with Antipuncture and Strain-Sensing Properties for Personal Protective Equipment

Currently, multifunction has become an essential direction of personal protective equipment (PPE), but achieving the protective effect, flexibility, physiological comfort, and intelligent application of PPE simultaneously is still a challenge. Herein, inspired by the meso-structure of rhinoceros skin, a novel strategy is proposed by compounding an ammonium sulfate ((NH4)2SO4) solution soaked gelatin hydrogel with the high weight fraction and vertically interwoven Kevlar fibers to manufacture a flexible and wearable composite with enhanced puncture resistance and strain-sensing properties. After (NH4)2SO4 solution immersion, the hydrogel's tensile strength, toughness, and fracture strain were up to 3.77 MPa, 4.26 MJ/m3, and 305.19%, respectively, indicating superior mechanical properties. The Kevlar/hydrogel composites revealed excellent puncture resistance (quasi-static of 132.06 N and dynamic of 295.05 N), flexibility (138.13 mN/cm), and air and moisture permeability (17.83 mm/s and 2092.73 g m-2 day-1), demonstrating a favorable balance between the protective effect and wearing comfort even after 7 days of environmental exposure. Meanwhile, salt solution immersion endowed the composite with excellent strain-sensing properties at various bending angles (30-90°) and frequencies (0.25-1 Hz) and allowed it to monitor different human motions directly in real-time. The rhinoceros-skin-inspired Kevlar/hydrogel composites provide a simple and economical solution for antipuncture materials that combine high protective effects, a comfortable wearing experience, and good strain-sensing properties, promising multifunctional PPE in the future.

Biocompatible and Biodegradable 3D Graphene/Collagen Fiber Hybrids for High-Performance Conductive Networks and Sensors

Polymer-based flexible conductive materials are crucial for wearable electronics, electronic skin, and other smart materials. However, their development and commercial applications have been hampered by the lack of strain tolerance in the conductive network, poor bonding with polymers, discomfort during wear, and a lack of biocompatibility. This study utilized oil-tanned leather with a natural network structure, high toughness, and high tensile deformation recovery as a structural template. A graphene (Gr) conductive network was then constructed on the collagen network of the leather, with coordination cross-linking between Gr and collagen fibers through aluminum ions (Al3+). A new flexible conductive material (Al-GL) was then constructed. Molecular dynamics simulations and experimental validation revealed the existence of physical adsorption, hydrogen bonding adsorption, and ligand bonding between Al3+, Gr, and collagen fibers. Although we established that the binding sites between Al3+ and collagen fibers were primarily on carboxyl groups (-COOH), the mechanism of chemical bonding between Gr and collagen fibers remains unclear. The Al-GL composite exhibited a high shrinkage temperature (67.4 °C) and low electrical resistance (16.1 kΩ·sq-1), as well as good softness (9.33 mN), biocompatibility, biodegradability (<60 h), and air and moisture permeability. Furthermore, the incorporation of Al3+ resulted in a heightened Gr binding strength on Al-GL, and the resistance remained comparable following 1 h of water washing. The Al-GL sensor prepared by WPU encapsulation not only demonstrated highly sensitive responses to diverse motion signals of the human body but also retained a certain degree of response to external mechanical effects underwater. Additionally, the Al-GL-based triboelectric nanogenerator (Al-GL TENG) exhibited distinct response signals to different materials. The Al-GL prepared by the one-pot method proposed in this study offers a novel approach to combining functional nanofillers and substrate materials, providing a theoretical foundation for collagen fiber-based flexible conductive materials.

Wearable EMI Shielding Composite Films with Integrated Optimization of Electrical Safety, Biosafety and Thermal Safety

Biomaterial-based flexible electromagnetic interference (EMI) shielding composite films are desirable in many applications of wearable electronic devices. However, much research focuses on improving the EMI shielding performance of materials, while optimizing the comprehensive safety of wearable EMI shielding materials has been neglected. Herein, wearable cellulose nanofiber@boron nitride nanosheet/silver nanowire/bacterial cellulose (CNF@BNNS/AgNW/BC) EMI shielding composite films with sandwich structure are fabricated via a simple sequential vacuum filtration method. For the first time, the electrical safety, biosafety, and thermal safety of EMI shielding materials are optimized integratedly. Since both sides of the sandwich structure contain CNF and BC electrical insulation layers, the CNF@BNNS/AgNW/BC composite films exhibit excellent electrical safety. Furthermore, benefiting from the AgNW conductive networks in the middle layer, the CNF@BNNS/AgNW/BC exhibit excellent EMI shielding effectiveness of 49.95 dB and ultra-fast response Joule heating performance. More importantly, the antibacterial property of AgNW ensures the biosafety of the composite films. Meanwhile, the AgNW and the CNF@BNNS layers synergistically enhance the thermal conductivity of the CNF@BNNS/AgNW/BC composite film, reaching a high value of 8.85 W m‒1 K‒1, which significantly enhances its thermal safety when used in miniaturized electronic device. This work offers new ideas for fabricating biomaterial-based EMI shielding composite films with high comprehensive safety.

Ultralight Flexible Collagen Fiber Based Aerogels Derived from Leather Solid Waste for High Electromagnetic Interference Shielding

Designing and developing high-performance shielding materials against electromagnetic interference is of utmost importance due to the rapid advancement of wireless telecommunication technologies. Such materials hold both fundamental and technological significance. A three-stage process is presented for creating ultralight, flexible aerogels from biomass to shield against electromagnetic interference. Collagen fibers sourced from leather solid waste are used for: (i) freeze-drying preparation of collagen fibers/poly(vinyl alcohol) (PVA) aerogels, (ii) adsorption of silver nanowires (AgNWs) onto collagen fiber/PVA aerogels, and (iii) Hydrophobic modification of collagen fiber/PVA/AgNWs aerogels with 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (POTS). Scanning electron microscopy studies reveal that an interweaving of AgNWs and collagen fiber/PVA porous network has formed a conductive network, exhibiting an electrical conductivity of 103 S·m-1. The electromagnetic interference shielding effectiveness reached more than 62 dB, while the density was merely 5.8 mg/cm3. The collagen fiber/PVA/AgNWs/POTS aerogel displayed an even better electromagnetic shielding efficiency of 73 dB and water contact angle of 147°. The study results emphasize the distinctive capacity of leather solid waste to generate cost-effective, ecofriendly, and highly efficient electromagnetic interference shielding materials.

Lightweight and Strong Cellulosic Triboelectric Materials Enabled by Cell Wall Nanoengineering

As intelligent technology surges forward, wearable electronics have emerged as versatile tools for monitoring health and sensing our surroundings. Among these advancements, porous triboelectric materials have garnered significant attention for their lightness. However, these materials face the challenge of improving structural stability to further enhance the sensing accuracy of triboelectric sensors. In this study, a lightweight and strong porous cellulosic triboelectric material is designed by cell wall nanoengineering. By tailoring of the cell wall structure, the material shows a high mechanical strength of 51.8 MPa. The self-powered sensor constructed by this material has a high sensitivity of 33.61 kPa-1, a fast response time of 36 ms, and excellent pressure detection durability. Notably, the sensor still enables a high sensing performance after the porous cellulosic triboelectric material exposure to 200 °C and achieves real-time feedback of human motion, thereby demonstrating great potential in the field of wearable electronic devices.