Vascular smooth muscle-inspired architecture enables soft yet tough self-healing materials for durable capacitive strain-sensor

Noncovalent Soft Composites with Superior Thermal Conductivity and Photothermal Efficiency for Advanced Thermal Management

Soft materials with elevated thermal conductivity are highly sought after for efficient, adaptable thermal management in contemporary electronics, yet their fabrication remains challenging. We describe a soft composite created by integrating tannic acid-mediated liquid metals and graphene nanosheets into a polyurethane matrix through a noncovalent assembly approach that involves multiple interfacial supramolecular interactions. This composite demonstrates remarkable toughness (90.39 MJ m-3) and stretchability (1050% strain) alongside superior through-plane thermal conductivity (18.69 W m-1 K-1) and in-plane thermal conductivity (8.05 W m-1 K-1). Additionally, the composite features excellent broadband light absorption (>85%) and a photothermal conversion efficiency of 84%, enabling heat generation. Our findings overcome the traditional trade-off between high thermal conductivity and mechanical compliance in a single material. We anticipate that our design strategy will pave the way for advanced thermal management materials that require functional integration.

Load-Bearing Organogels: Hierarchical Anisotropic Composite Structure for High Mechanical Toughness and Antifatigue-Fracture Capability under Extreme Conditions

Gels with excellent mechanical properties and antifatigue-fracture capability are attractive materials for load-bearing applications; however, at extreme temperatures, they still suffer from catastrophic failure caused by freezing- or dehydration-induced crack propagation. Here, we present a series of hierarchical anisotropic composite organogels that are strong yet tough and antifatigue-fracture over a wide temperature range (-30 to 60 °C) through the combination strategies of freezing-casting, annealing, and solvent exchange with polyols. Such a hybrid design endows the gels with anisotropic and hierarchical structures and excellent tolerance to extreme temperatures, thus guaranteeing efficient energy dissipation and crack propagation resistance under both ambient and harsh conditions. For instance, the organogel obtained via solvent exchange with glycerol exhibited high strength (22.6 MPa), toughness (198.0 MJ/m3), fatigue threshold (6.92 kJ/m2), and particularly, a superhigh fracture energy (665.7 kJ/m2), which is even higher than anhydrous elastomers, metals, and alloys. Importantly, these values were further boosted at extreme temperatures, such as fatigue thresholds of 8.01 and 9.77 kJ/m2 at -30 and 60 °C, respectively. This work offers an attractive strategy for fabricating gel materials that are reliable for load-bearing applications under extreme conditions.

Tough fiber-reinforced composite ionogels with crack resistance surpassing metals

Ion-conductive materials have received much attention because of their good mechanical and electrical properties. However, their practical applications are still hampered by limited toughness and crack resistance, stemming from the restricted size of energy dissipation zones, which impacts their reliability and durability. Herein, tough fiber-reinforced composite ionogels (FRCIs) with crack resistance are fabricated by incorporating high-performance fibers into elastic ionogels to efficiently dissipate energy. The FRCIs exhibit good tearing toughness, high strength, high elastic modulus, and low bending modulus. The toughness and crack resistance of the FRCI far exceed that of previously reported gel materials, even outperforming metals and alloys. Furthermore, the electrical resistance of FRCI shows high sensitivity to deformation. Moreover, it remains undamaged after undergoing 10,000 bending cycles when fixing the artificial bone, and possesses self-sensing impact resistance, demonstrating great potential in intelligent robots and smart protective equipment.

Liquid Metal-Promoted Supramolecular Interactions Enable Ultrafast Self-Healing Triboelectric Materials with High Performance at Room Temperature

Soft self-healing materials are excellent candidates for wearable devices to power sensors due to their excellent compliance, extensibility, and self-restorability. However, combining ultrafast and autonomous restorative properties with excellent mechanical capabilities for application in self-powered wearable device still poses challenges. Utilizing the high mobility and conductivity of liquid metal, this paper incorporates it into polydimethylsiloxane by a supramolecular interfacial assembly strategy to prepare a triboelectric material with ultrahigh stretchability (12000%) and remarkable self-healing (30 min at ∼25 °C). The dynamic bonds endow the material with excellent and universal self-healing ability under extreme environments (-20 °C, near infrared, and underwater), mechanical durability, and triboelectric properties (100 V and 0.81 W/m2). By integrating the material into wearable self-powered devices, real-time feedback on human joint movement is enabled. This work offers a valuable strategy to balance the trade-off between shape adaptation and self-healing, paving the way for enhanced applicability in sensing applications.

A Visible Light-Responsive, Fast Room-Temperature Self- Healing, Mechanically Robust, Antibacterial Waterborne Polyurethane Based on Triple Dynamic Bonds

Despite the recent rapid advancements in room-temperature self-healing waterborne polyurethanes, imparting fast self-healing ability while concurrently maintaining robust mechanical performance of waterborne polyurethanes remains a formidable challenge. Herein, we propose a molecular structure design strategy for developing visible light-responsive, room-temperature self-healing, and antibacterial waterborne polyurethane (DMZWPU) containing triple dynamic bonds of diselenide bonds, multiple hydrogen bonds, and Zn(II)-carboxylate coordination bonds. This innovative approach effectively balances the tensile stress, fracture toughness, and self-healing ability of the material. Thanks to the synergy of the three dynamic bonds, the resulting DMZWPU film demonstrates a tensile stress of 40.32 MPa and a fracture toughness of 119.29 MJ/m3, respectively. Furthermore, based on the dynamic characteristics of three dynamic bonds and the dual induction of trace ethanol and visible light, the damaged DMZWPU film can recover more than 85% of the tensile stress at room temperature within 2 h. These performances outperform those of most of the currently reported room-temperature self-healable polymers (healing efficiency >80%). Due to the combined action of selenium and zinc ions, the DWZWPU film exhibits excellent antibacterial properties (sterilization rate of 100% in 24 h). Finally, the DMZWPU emulsion is effectively applied for leather finishing processes, and the results show that the DMZWPU coating exhibits excellent folding resistance, wear resistance, and room-temperature self-healing function, as well as enhanced water resistance and dry friction resistance. In summary, this study provides a novel perspective for the development of waterborne polyurethane with high mechanical performances and rapid self-healable ability at room temperature.

Simultaneous Isotropic Omnidirectional Hypersensitive Strain Sensing and Deep Learning-Assisted Direction Recognition in a Biomimetic Stretchable Device

Omnidirectional strain sensing and direction recognition ability are features of the human tactile sense, essential to address the intricate and dynamic requirements of real-world applications. Most of the current strain sensors work by converting uniaxial strain into electrical signals, which restricts their use in environments with multiaxial strain. Here, the first device with simultaneous isotropic omnidirectional hypersensitive strain sensing and direction recognition (IOHSDR) capabilities is introduced. By mimicking the human fingers from three dimensions, the IOHSDR device realizes a novel heterogeneous substrate that incorporates the involute of a circle, resulting in isotropic behavior in the radial direction and anisotropic property in the involute direction for hypersensitive strain sensing. With the assistance of a deep learning-based model, the IOHSDR device accomplishes an impressive accuracy of 99.58% in recognizing 360° stretching directions. Additionally, it exhibits superior performance in the typical properties of stretchable strain sensors, with a gauge factor of 634.12, an ultralow detection limit of 0.01%, and outstanding durability exceeding 15 000 cycles. The demonstration of radial artery pulse and throat vibration applications highlights the IOHSDR's unique characteristics of isotropic omnidirectional sensing and precise direction detection unleashing new classes of wearable health monitoring devices.

Crack-Resistant and Self-Healable Passive Radiative Cooling Silicone Compounds

Crack damage and expansion are prevalent issues in outdoor materials, which absorb or transmit sunlight to damaged areas, substantially impairing the functionality of passive radiative cooling systems. Herein, a silicone/dielectric radiative cooling compound is introduced that is both self-healing and crack-resistant, developed through the synthesis of a dynamic and crack-resistant polymer/dielectric hydrogen bond network. This network incorporates boron nitride dielectrics, which serve as sunlight scatterers and hydrogen bond acceptors, with customized silicone polymer featuring high atmospheric window emissive chain segments and UV-vis-NIR transparent hydrogen bond moieties. When cracks form, the polymer's chain mobility allows the hydrogen bond moieties in boron nitride and silicone to re-associate, realizing self-healing of cracks from micrometers to millimeters wide and restoring cooling performance to ≈100%. The combination of rigid boron nitride and sacrificial hydrogen bonds in polymer also enhances the materials' fracture energy to 865%, effectively preventing further crack propagation under stress through autonomous crack blunting and deflection. These remarkable characteristics make this radiative cooling compound highly suited for increasingly complex, dynamic, and prolonged outdoor application environments.

Advances in Electrically Conductive Hydrogels: Performance and Applications

Electrically conductive hydrogels are highly hydrated 3D networks consisting of a hydrophilic polymer skeleton and electrically conductive materials. Conductive hydrogels have excellent mechanical and electrical properties and have further extensive application prospects in biomedical treatment and other fields. Whereas numerous electrically conductive hydrogels have been fabricated, a set of general principles, that can rationally guide the synthesis of conductive hydrogels using different substances and fabrication methods for various application scenarios, remain a central demand of electrically conductive hydrogels. This paper systematically summarizes the processing, performances, and applications of conductive hydrogels, and discusses the challenges and opportunities in this field. In view of the shortcomings of conductive hydrogels in high electrical conductivity, matchable mechanical properties, as well as integrated devices and machines, it is proposed to synergistically design and process conductive hydrogels with applications in complex surroundings. It is believed that this will present a fresh perspective for the research and development of conductive hydrogels, and further expand the application of conductive hydrogels.

Soft Materials and Devices Enabling Sensorimotor Functions in Soft Robots

Sensorimotor functions, the seamless integration of sensing, decision-making, and actuation, are fundamental for robots to interact with their environments. Inspired by biological systems, the incorporation of soft materials and devices into robotics holds significant promise for enhancing these functions. However, current robotics systems often lack the autonomy and intelligence observed in nature due to limited sensorimotor integration, particularly in flexible sensing and actuation. As the field progresses toward soft, flexible, and stretchable materials, developing such materials and devices becomes increasingly critical for advanced robotics. Despite rapid advancements individually in soft materials and flexible devices, their combined applications to enable sensorimotor capabilities in robots are emerging. This review addresses this emerging field by providing a comprehensive overview of soft materials and devices that enable sensorimotor functions in robots. We delve into the latest development in soft sensing technologies, actuation mechanism, structural designs, and fabrication techniques. Additionally, we explore strategies for sensorimotor control, the integration of artificial intelligence (AI), and practical application across various domains such as healthcare, augmented and virtual reality, and exploration. By drawing parallels with biological systems, this review aims to guide future research and development in soft robots, ultimately enhancing the autonomy and adaptability of robots in unstructured environments.

Liquid Metal Particles Decorated by Poly(imidazole-urea) as Versatile Adhesive and Recyclable Inks for Substrate-Irrelevant Direct Writing

Liquid metals (LMs) with fluidity and conductivity are widely applied in flexible electronics. However, the surface patterning of liquid metals (LMs) is restricted by the low adhesion effect on the substrates because of the intrinsic high surface tension. In this study, a versatile adhesive conductive poly(imidazole-urea)/eutectic Ga75.5In24.5 alloy (PIU/EGaIn) ink is proposed by wrapping the EGaIn particles with PIU through metal coordination to realize substrate-independent direct writing. The adhesion of PIU guarantees that the PIU/EGaIn ink can be written smoothly on different substrates, ranging from flexible to rigid and plane to camber. Complex patterns can also be stamped on the substrate by transfer printing. The maximum conductivity of the handwriting trace can reach as high as 1.3 × 106 S/m due to the highly efficient stability of EGaIn particles with a low content of residue PIU. The written circuit demonstrates high stability and maintains constant conductivity after 500 cycles of deformations (folding, bending, and stretching), thanks to the good adhesion effect of PIU with substrates. In addition, the resistance touch sensor was patterned to detect finger contact as a demonstration of potential application. The PIU/EGaIn ink waste can be recycled using an alkaline solution owing to the intrinsic degradability of PIU. This strategy offers a new choice for universal adhesive conductive ink that is suitable for environmentally friendly flexible electronics.

Advances in Soft Strain and Pressure Sensors

Soft strain and pressure sensors represent a breakthrough in material engineering and nanotechnology, providing accurate and reliable signal detection for applications in health monitoring, sports management, human-machine interface, or soft robotics, when compared to traditional rigid sensors. However, their performance is often compromised by environmental interference and off-axis mechanical deformations, which lead to nonspecific responses, as well as unstable and inaccurate measurements. These challenges can be effectively addressed by enhancing the sensors' specificity, making them responsive only to the desired stimulus while remaining insensitive to unwanted stimuli. This review systematically examines various materials and design strategies for developing strain and pressure sensors with high specificity for target physical signals, such as tactility, pressure distribution, body motions, or artery pulse. This review highlights approaches in materials engineering that impart special properties to the sensors to suppress interference from factors such as temperature, humidity, and liquid contact. Additionally, it details structural designs that improve sensor performance under different types of off-axis mechanical deformations. This review concludes by discussing the ongoing challenges and opportunities for inspiring the future development of highly specific electromechanical sensors.

Design and in-situ biomimetic fabrication of a high-density strain sensor array for parachute canopy fabric

In-situ monitoring of non-uniform strains in spacecraft parachute canopies is essential to ensure safe landings. Traditional wearable strain sensors struggle to meet high-resolution measurement requirements due to their low density. In-situ inkjet printing offers a promising solution for fabricating high-density strain sensor arrays directly on the fabric surface. However, capillary effects in the canopy fabric cause droplet leakage, hindering stable printing. To address this, we drew inspiration from nature, using modified silane to mimic the wax layer of coconut husk for modifying the canopy fabric, which enabled the in-situ fabrication of a strain sensor array via inkjet printing. This modification overcame capillary effects and balanced the fabric's wettability, essential for stable printing. Furthermore, a layered printing strategy was designed to increase sensor density to 4 units·cm-2, facilitating high-resolution measurement of non-uniform strains in the canopy. This study offers a feasible approach for developing sensors for large-scale parachute strain measurements.

Research Progress of Human Biomimetic Self-Healing Materials

Humans can heal themselves after injury, which inspires researchers to develop bionic self-healing materials. Such materials not only equipped with the self-repair capacities akin to those of the human body, but also emulate the mechanical properties of human organs, including the tensile resilience of muscles, the fatigue resistance of skin, and the elevated modulus typical of cartilage. Based on the design concept of imitating the structure of human organs, the bionic self-healing material perfectly solves the problem of poor mechanical properties of self-healing materials caused by weak bond energy and inter-chain flow. This review discusses various organ-inspired self-healing materials in detail, summarizes their synthetic principles and introduces their fascinating mechanical properties. Finally, the application prospects of bionic self-healing polymer materials, such as bio-strain sensors, self-healing anticorrosive coatings, biomedical detection, etc., are outlined. Considering the excellent comprehensive performance and multi-functions of human biomimetic self-healing polymers, more outstanding sustainable materials will be developed, accelerating research progress in self-healing materials and realizing environmentally friendly products in multiple fields.

Fracture-Resistant Stretchable Materials: An Overview from Methodology to Applications

Stretchable materials, such as gels and elastomers, are attractive materials in diverse applications. Their versatile fabrication platforms enable the creation of materials with various physiochemical properties and geometries. However, the mechanical performance of traditional stretchable materials is often hindered by the deficiencies in their energy dissipation system, leading to lower fracture resistance and impeding their broader range of applications. Therefore, the synthesis of fracture-resistant stretchable materials has attracted great interest. This review comprehensively summarizes key design considerations for constructing fracture-resistant stretchable materials, examines their synthesis strategies to achieve elevated fracture energy, and highlights recent advancements in their potential applications.

A Multifunctional Coating with Active Corrosion Protection Through a Synergistic pH- and Thermal-Responsive Mechanism

This article aims to develop CeO2 nanocontainer-constructed coating with a synergistic self-healing and protective nature through a simple mechanical blending technique to manage metal corrosion. The proposed coating exhibits excellent corrosion resistance, which is primarily attributed to the combination of thermal-driven healing and active corrosion inhibition. Paraffin wax and 2-polybenzothiazole-loaded CeO2 nanotubes (CeO2-MBT) are directly doped into epoxy coating to perform such a multifunctional role. CeO2 nanocontainers and encapsulated corrosion inhibitor MBT can be released by pH triggers to achieve instant corrosion inhibition upon the surface of metal substrate. In addition, any physical defects in the coating are responsively repaired by heating incorporated paraffin wax to regain structural integrity and consequent barrier function. Corrosion protection efficiency remains sufficient even after ten cycles of damage and healing. Such a multiple-functional coating strategy provides an alternative pathway toward efficient and sustainable performance to tackle corrosion-related challenges of metal components in both short-term and long-term services.

A Versatile Microporous Design toward Toughened yet Softened Self-Healing Materials

Realizing the full potential of self-healing materials in stretchable electronics necessitates not only low modulus to enable high adaptivity, but also high toughness to resist crack propagation. However, existing toughening strategies for soft self-healing materials have only modestly improves mechanical dissipation near the crack tip (ГD), and invariably compromise the material's inherent softness and autonomous healing capabilities. Here, a synthetic microporous architecture is demonstrated that unprecedently toughens and softens self-healing materials without impacting their intrinsic self-healing kinetics. This microporous structure spreads energy dissipation across the entire material through a bran-new dissipative mode of adaptable crack movement (ГA), which substantially increases the fracture toughness by 31.6 times, from 3.19 to 100.86 kJ m-2, and the fractocohesive length by 20.7 times, from 0.59 mm to 12.24 mm. This combination of unprecedented fracture toughness (100.86 kJ m-2) and centimeter-scale fractocohesive length (1.23 cm) surpasses all previous records for synthetic soft self-healing materials and even exceeds those of light alloys. Coupled with significantly enhanced softness (0.43 MPa) and nearly perfect autonomous self-healing efficiency (≈100%), this robust material is ideal for constructing durable kirigami electronics for wearable devices.

Fireproof Cavity Structure with Enhanced Impact Resistance and Thermal Insulation toward Safeguarding

Developing devices emphasizing safety protection is becoming increasingly important due to the widespread occurrence of impact damage and thermal hazards. Herein, the F-SSG/TPU-based circular cavity structure (FC) is developed through a convenient and efficient template method, which can effectively achieve anti-impact and thermal insulation for protection. The flame-retardant shear stiffening gel/thermoplastic urethane (F-SSG/TPU) is synthesized through the dynamic interaction between the SSG, TPU, and modified ammonium polyphosphate (APP@UiO-66-NH2) by thermo-solvent reactions. The developed FC can dissipate the impact force from 4.19 to 0.99 kN at 45 cm impacting heights, indicating good anti-impact performance. Moreover, the thermal insulation test demonstrates that the FC achieves a temperature drop of 76 °C at 160 °C attributed to the unique cavity structure design. Under the continuous shock of high-temperature flame, FC remains intact, and its performance is almost undamaged. These results elaborate that the designed FC can effectively resist various damage, such as high-temperature shock and collision. Then, a wearable wristband integrated with FC is developed which exhibits superior impact resistance and heat insulation properties compared with commercial wristbands. In short, this cavity structure based on high-performance F-SSG/TPU material shows promising potential applications in the protection field.

Organic-inorganic covalent-ionic network enabled all-in-one multifunctional coating for flexible displays

Touch displays are ubiquitous in modern technologies. However, current protective methods for emerging flexible displays against static, scratches, bending, and smudge rely on multilayer materials that impede progress towards flexible, lightweight, and multifunctional designs. Developing a single coating layer integrating all these functions remains challenging yet highly anticipated. Herein, we introduce an organic-inorganic covalent-ionic hybrid network that leverages the reorganizing interaction between siloxanes (i.e., trifluoropropyl-funtionalized polyhedral oligomeric silsesquioxane and cyclotrisiloxane) and fluoride ions. This nanoscale organic-inorganic covalent-ionic hybridized crosslinked network, combined with a low surface energy trifluoropropyl group, offers a monolithic layer coating with excellent optical, antistatic, anti-smudge properties, flexibility, scratch resistance, and recyclability. Compared with existing protective materials, this all-in-one coating demonstrates comprehensive multifunctionality and closed-loop recyclability, making it ideal for future flexible displays and contributing to ecological sustainability in consumer electronics.

Preparation of Self-healing Thermoplastic Polysiloxane-Polyurea/Polyether-Polyurea Elastomer Blends with a Co-continuous Microphase Structure and In-Depth Research on Their Synergistic Effects

Polymer blending has been an important method to create materials with specific properties that have synergistic effects. However, there are few reports on the mechanism of synergistic effects. It is well known that it is quite difficult to obtain ideal blends composed of nonpolar organosilicon polymers and polar polymers. In this paper, thermoplastic polyurea elastomer blends with a co-continuous microphase structure consisting of polysiloxane-polyurea (PDMS-PUA), polyether amine-polyurea (PEA-PUA), and compatibilizer PDMS-PUA-grafted PEA-PUA (PDMS-PUA-g-PEA-PUA) were prepared for the first time. For the first time, introduction of polysiloxane does not sacrifice mechanical properties of thermoplastic polyurea elastomers. For example, the tensile strength of the elastomer blend with 30 wt % PDMS-PUA content reached 25.7 MPa, which is higher than those of PEA-PUA and PDMS-PUA. The blends also show typical outstanding characters such as exceptional heat and water resistance. The mechanism of the synergistic effect on mechanical properties is revealed based on in-depth studies on mutual interphase interaction. In situ variable temperature infrared spectroscopic analysis (VTIR) shows that compatibilization facilitates the construction of a denser hydrogen bonding network at the blend interface, which is thought to play a key role in the co-continuous microphase structure. Microscopic morphological characterization shows that PDMS-PUA and PEA-PUA phases are deformed and oriented together during the stretching process, thus jointly resisting external forces. Moreover, the blends show an exceptional self-healing ability due to their strong and reversible hydrogen bonding network.

Mechanical Regulation of Polymer Gels

The mechanical properties of polymer gels devote to emerging devices and machines in fields such as biomedical engineering, flexible bioelectronics, biomimetic actuators, and energy harvesters. Coupling network architectures and interactions has been explored to regulate supportive mechanical characteristics of polymer gels; however, systematic reviews correlating mechanics to interaction forces at the molecular and structural levels remain absent in the field. This review highlights the molecular engineering and structural engineering of polymer gel mechanics and a comprehensive mechanistic understanding of mechanical regulation. Molecular engineering alters molecular architecture and manipulates functional groups/moieties at the molecular level, introducing various interactions and permanent or reversible dynamic bonds as the dissipative energy. Molecular engineering usually uses monomers, cross-linkers, chains, and other additives. Structural engineering utilizes casting methods, solvent phase regulation, mechanochemistry, macromolecule chemical reactions, and biomanufacturing technology to construct and tailor the topological network structures, or heterogeneous modulus compositions. We envision that the perfect combination of molecular and structural engineering may provide a fresh view to extend exciting new perspectives of this burgeoning field. This review also summarizes recent representative applications of polymer gels with excellent mechanical properties. Conclusions and perspectives are also provided from five aspects of concise summary, mechanical mechanism, biofabrication methods, upgraded applications, and synergistic methodology.

Strong and Healable Elastomers with Photothermal-Stimulus Dynamic Nanonetworks Enabled by Subnano Ultrafine MoO3-x Nanowires

One-dimensional nanomaterials have become one of the most available nanoreinforcing agents for developing next-generation high-performance functional self-healing composites owing to their unique structural characteristics and surface electron structure. However, nanoscale control, structural regulation, and crystal growth are still enormous challenges in the synthesis of specific one-dimensional nanomaterials. Here, oxygen-defective MoO3-x nanowires with abundant surface dynamic bonding were successfully synthesized as novel nanofillers and photothermal response agents combined with a polyurethane matrix to construct composite elastomers, thus achieving mechanically enhanced and self-healing properties. Benefiting from the surface plasmon resonance of the MoO3-x nanowires and interfacial multiple dynamic bonding interactions, the composite elastomers demonstrated strong mechanical performance (with a strength of 31.45 MPa and elongation of 1167.73%) and ultrafast photothermal toughness self-healing performance (20 s and an efficiency of 94.34%). The introduction of MoO3-x nanowires allows the construction of unique three-dimensional cross-linked nanonetworks that can move and regulate interfacial dynamic interactions under 808 nm infrared laser stimulation, resulting in controlled mechanical and healing performance. Therefore, such special elastomers with strong photothermal responses and mechanical properties are expected to be useful in next-generation biological antibacterial materials, wearable devices, and artificial muscles.

Liquid metal interface mechanochemistry disentangles energy density and biaxial stretchability tradeoff in composite capacitor film

Dielectric polymer composites for film capacitors have advanced significantly in recent decades, yet their practical implementation in industrial-scale, thin-film processing faces challenges, particularly due to limited biaxial stretchability. Here, we introduce a mechanochemical solution that applies liquid metal onto rigid dielectric fillers (e.g. boron nitride), dramatically transforming polymer-filler interface characteristics. This approach significantly reduces modulus mismatch and stress concentration at the interface region, enabling polypropylene composites to achieve biaxial stretching ratio up to 450 × 450%. Furthermore, liquid metal integration enhances boron nitride's dielectric polarization while maintaining inherent insulation, producing high-dielectric-constant, low-loss films. These films, only microns thick yet quasi square meters in area, achieve a 55% increase in energy density over commercial biaxially-oriented polypropylene (from 2.9 to 4.5 J cm-3 at 550 MV/m), keeping 90% discharge efficiency. Coupled with improved thermal conductivity, durability, and device capacitance, this distinctive interface engineering approach makes these composites promising for high-performance film capacitors.

Printed Self-Healing Stretchable Electronics for Bio-signal Monitoring and Intelligent Packaging

Integrating self-healing capabilities into printed stretchable electronic devices is important for improving performance and extending device life. However, achieving printed self-healing stretchable electronic devices with excellent device-level healing ability and stretchability while maintaining outstanding electrical performance remains challenging. Herein, a series of printed device-level self-healing stretchable electronic devices is achieved by depositing liquid metal/silver fractal dendrites/polystyrene-block-polyisoprene-block-polystyrene (LM/Ag FDs/SIS) conductive inks onto a self-healing thermoplastic polyurethane (TPU) film via screen printing method. Owing to the fluidic properties of the LM and the interfacial hydrogen bonding and disulfide bonds of TPU, the as-obtained stretchable electronic devices maintain good electronic properties under strain and exhibit device-level self-healing properties without external stimulation. Printed self-healing stretchable electrodes possess high electrical conductivity (1.6 × 105 S m-1), excellent electromechanical properties, and dynamic stability, with only a 2.5-fold increase in resistance at 200% strain, even after a complete cut and re-healing treatment. The printed self-healing capacitive stretchable strain sensor shows good linearity (R2 ≈0.9994) in a wide sensing range (0%-200%) and is successfully applied to bio-signal detection. Furthermore, the printed self-healing electronic smart label is designed and can be used for real-time environmental monitoring, which exhibits promising potential for practical application in food preservation packaging.

Synthesis of Photoresponsive Fast Self-healing Polyolefin Composites by Nickel-Catalyzed Copolymerization of Ethylene and Lignin Cluster Monomers

Polymers may suffer from sudden mechanical damages during long-term use under various harsh operating environments. Rapid and real-time self-healing will extend their service life, which is particularly attractive in the context of circular economy. In this work, a lignin cluster polymerization strategy (LCPS) was designed to prepare a series of lignin functionalized polyolefin composites with excellent mechanical properties through nickel catalyzed copolymerization of ethylene and lignin cluster monomers. These composites can achieve rapid self-healing within 30 seconds under a variety of extreme usage environments (underwater, seawater, extremely low temperatures as low as -60 °C, organic solvents, acid/alkali solvents, etc.), which is of great significance for real-time self-healing of sudden mechanical damage. More importantly, the dynamic cross-linking network within these composites enable great re-processability and amazing sealing performances.

What Exactly Can Bionic Strategies Achieve for Flexible Sensors?

Flexible sensors have attracted great attention in the field of wearable electronic devices due to their deformability, lightness, and versatility. However, property improvement remains a key challenge. Fortunately, natural organisms exhibit many unique response mechanisms to various stimuli, and the corresponding structures and compositions provide advanced design ideas for the development of flexible sensors. Therefore, this Review highlights recent advances in sensing performance and functional characteristics of flexible sensors from the perspective of bionics for the first time. First, the "twins" of bionics and flexible sensors are introduced. Second, the enhancements in electrical and mechanical performance through bionic strategies are summarized according to the prototypes of humans, plants, and animals. Third, the functional characteristics of bionic strategies for flexible sensors are discussed in detail, including self-healing, color-changing, tangential force, strain redistribution, and interfacial resistance. Finally, we summarize the challenges and development trends of bioinspired flexible sensors. This Review aims to deepen the understanding of bionic strategies and provide innovative ideas and references for the design and manufacture of next-generation flexible sensors.

Self-healing, antibiofouling and anticorrosion properties enabled by designing polymers with dynamic covalent bonds and responsive linkages

Coating metal structures with a protective material is a popular strategy to prevent their deterioration due to corrosion. However, maintaining the barrier properties of coatings after their mechanical damage is challenging. Herein, we prepared multifunctional coatings with self-healing ability to conserve their anticorrosion performance after damage. The coating was formed by blending synthesized redox-responsive copolymers with the ability to release a corrosion inhibitor upon the onset of corrosion with synthesized self-healing polyurethanes containing disulfide bonds. The corrosion rate of steel substrates coated with a blend is approximately 24 times lower than that of steel coated with only self-healing polyurethane. An exceptional healing efficiency, as high as 95%, is obtained after mechanical damage. The antibiofouling property against bacterial and microalgal attachments on coatings is facilitated by the repellent characteristic of fluorinated segments and the biocidal activity of the inhibitor moieties in the copolymer.

A Rational Design of Bio-Derived Disulfide CANs for Wearable Capacitive Pressure Sensor

Classic approaches to integrate flexible capacitive sensor performance are to on-demand microstructuring dielectric layers and to adjust dielectric material compositions via the introduction of insoluble carbon additives (to increase sensitivity) or dynamic interactions (to achieve self-healing). However, the sensor's enhanced performances often come with increased material complexity, discouraging its circular economy. Herein, a new intrinsic self-healable, closed-loop recyclable dielectric layer material, a fully nature-derived dynamic covalent poly(disulfide) decorated with rich H bonding and metal-catechol complexations is introduced. The polymer network possesses a mechanically ductile character with an Arrhenius-type temperature-dependent viscoelasticity. The assembled capacitive pressure sensor is able to achieve a sensitivity of up to 9.26 kPa-1, fast response/recovery time of 32/24 ms, and can deliver consistent signals of continuous consecutive cycles even after being self-healed or closed-loop recycled for real-time detection of human motions. This is expected to be of high interest for current capacitive sensing research to move toward a life-like, high performance, and circular economy direction.

Intelligent anti-impact elastomers by precisely tailoring the topology of modular polymer networks

High-performance elastomers are essential in daily life and various industrial sectors such as personal protection, soft electronics, and vibration control. Nevertheless, despite massive efforts, concurrently achieving ultrahigh flexibility and remarkable impact resistance continues to be elusive. Herein, we report an innovative modular construction strategy that employs a topology-tailoring polymer network consisting of stereoscopic (epoxy-oligosiloxane nanoclusters) and linear (amino-terminated polyurea) building blocks as independent modules to develop intelligent anti-impact elastomers via an epoxy-amine mechanism. By precisely tailoring the topology of building blocks, the elastomers demonstrate high flexibility and toughness, remarkable impact responsiveness and ultrahigh energy dissipation. Their anti-impact ability surpasses those of most common soft and rigid materials such as steel, plastic, rubber, foam, or even polyborosiloxane. Moreover, the elastomers are well-qualified for use in flexible display technologies, owing to their high transparency (>92% transmittance), exceptional fold-resistance (no creasing after 10 000 bends), and good thermal stability (no discoloration at 100 °C). Furthermore, the elastomers exhibit excellent versatility, enabling them to be combined with either soft or rigid materials to generate composites with ultrahigh puncture and ballistic resistance. This study offers a promising framework for the design and fabrication of intelligent anti-impact elastomers and provides valuable insights into the development of next-generation protective materials.

Ultra-Highly Stiff and Tough Shape Memory Polyurea with Unprecedented Energy Density by Precise Slight Cross-Linking

Shape memory polymers (SMPs) have attracted significant attention and hold vast potential for diverse applications. Nevertheless, conventional SMPs suffer from notable shortcomings in terms of mechanical properties, environmental stability, and energy density, significantly constraining their practical utility. Here, inspired by the structure of muscle fibers, an innovative approach that involves the precise incorporation of subtle, permanent cross-linking within a hierarchical hydrogen bonding supramolecular network is reported. This novel strategy has culminated in the development of covalent and supramolecular shape memory polyurea, which exhibits exceptional mechanical properties, including high stiffness (1347 MPa), strength (82.4 MPa), and toughness (312.7 MJ m-3), ensuring its suitability for a wide range of applications. Furthermore, it boasts remarkable recyclability and repairability, along with excellent resistance to moisture, heat, and solvents. Moreover, the polymer demonstrates outstanding shape memory effects characterized by a high energy density (24.5 MJ m-3), facilitated by the formation of strain-induced oriented nanostructures that can store substantial amounts of entropic energy. Simultaneously, it maintains a remarkable 96% shape fixity and 99% shape recovery. This delicate interplay of covalent and supramolecular bonds opens up a promising pathway to the creation of high-performance SMPs, expanding their applicability across various domains.

Review of Recent Progress on Silicone Rubber Composites for Multifunctional Sensor Systems

The latest progress (the year 2021-2024) on multifunctional sensors based on silicone rubber is reported. These multifunctional sensors are useful for real-time monitoring through relative resistance, relative current change, and relative capacitance types. The present review contains a brief overview and literature survey on the sensors and their multifunctionalities. This contains an introduction to the different functionalities of these sensors. Following the introduction, the survey on the types of filler or rubber and their fabrication are briefly described. The coming section deals with the fabrication methodology of these composites where the sensors are integrated. The special focus on mechanical and electro-mechanical properties is discussed. Electro-mechanical properties with a special focus on response time, linearity, and gauge factor are reported. The next section of this review reports the filler dispersion and its role in influencing the properties and applications of these sensors. Finally, various types of sensors are briefly reported. These sensors are useful for monitoring human body motions, breathing activity, environment or breathing humidity, organic gas sensing, and, finally, smart textiles. Ultimately, the study summarizes the key takeaway from this review article. These conclusions are focused on the merits and demerits of the sensors and are followed by their future prospects.

Regulation of Hard Segment Cluster Structures for High-performance Poly(urethane-urea) Elastomers

Elastomers are widely used in daily life; however, the preparation of degradable and recyclable elastomers with high strength, high toughness, and excellent crack resistance remains a challenging task. In this report, a polycaprolactone-based poly(urethane-urea) elastomer is presented with excellent mechanical properties by optimizing the arrangement of hard segment clusters. It is found that long alkyl chains of the chain extenders lead to small and evenly distributed hard segment clusters, which is beneficial for improving mechanical properties. Together with the multiple hydrogen bond structure and stress-induced crystallization, the obtained elastomer exhibits a high strength of 63.3 MPa, an excellent toughness of 431 MJ m-3 and an outstanding fracture energy of 489 kJ m-2, while maintaining good recyclability and degradability. It is believed that the obtained elastomer holds great promise in various application fields and it contributes to the development of a sustainable society.

Elastic and Self-Healing Copolymer Coatings with Antimicrobial Function

The revolutionary self-healing function for long-term and safe service processes has inspired researchers to implement them in various fields, including in the application of antimicrobial protective coatings. Despite the great advances that have been made in the field of fabricating self-healing and antimicrobial polymers, their poor transparency and the trade-off between the mechanical and self-healing properties limit the utility of the materials as transparent antimicrobial protective coatings for wearable optical and display devices. Considering the compatibility in the blending process, our group proposed a self-healing, self-cross-linkable poly{(n-butyl acrylate)-co-[N-(hydroxymethyl)acrylamide]} copolymer (AP)-based protective coating combined with two types of commercial cationic antimicrobial agents (i.e., dimethyl octadecyl (3-trimethoxysilylpropyl) ammonium chloride (DTSACL) and chlorhexidine gluconate (CHG)), leading to the fabrication of a multifunctional modified compound film of (AP/b%CHG)-grafted-a%DTSACL. The first highlight of this research is that the reactivity of the hydroxyl group in the N-(hydroxymethyl)acrylamide of the copolymer side chains under thermal conditions facilitates the "grafting to" process with the trimethoxysilane groups of DTSACL to form AP-grafted-DTSACL, yielding favorable thermal stability, improvement in hydrophobicity, and enhancement of mechanical strength. Second, we highlight that the addition of CHG can generate covalent and noncovalent interactions in a complex manner between the two biguanide groups of CHG with the AP and DTSACL via a thermal-triggered cross-linking reaction. The noncovalent interactions synergistically serve as diverse dynamic hydrogen bonds, leading to complete healing upon scratches and even showing over 80% self-healing efficiency on full-cut, while covalent bonding can effectively improve elasticity and mechanical strength. The soft nature of CHG also takes part in improving the self-healing of the copolymer. Moreover, it was discovered that the addition of CHG can enhance antimicrobial effectiveness, as demonstrated by the long-term superior antibacterial activity (100%) against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria and the antifouling function on a glass substrate and/or a silica wafer coated by the modified polymer.

3D Printing Self-Healing and Self-Adhesive Elastomers for Wearable Electronics in Amphibious Environments

To meet the demands of challenging usage scenarios, there is an increasing need for flexible electronic skins that can operate properly not only in terrestrial environments but also extend to complex aquatic conditions. In this study, we develop an elastomer by incorporating dynamic urea bonds and hydrogen bonds into the polydimethylsiloxane backbone, which exhibits excellent autonomous self-healing and reversible adhesive performance in both dry and wet environments. A multifunctional flexible sensor with excellent sensing stability, amphibious self-healing capacity, and amphibious self-adhesive performance is fabricated through solvent-free 3D printing. The sensor has a high sensing sensitivity (GF = 45.1) and a low strain response threshold (0.25%) and can be used to detect small human movements and physiological activities, such as muscle movement, joint movement, respiration, and heartbeat. The wireless wearable sensing system assembled by coupling this device with a bluetooth transmission system is suitable for monitoring strenuous human movement in amphibious environments, such as playing basketball, cycling, running (terrestrial environments), and swimming (aquatic environments). The design strategy provides insights into enhancing the self-healing and self-adhesive properties of soft materials and promises a prospective avenue for fabricating flexible electronic skin that can work properly in amphibious environments.

Recent progress in multifunctional, reconfigurable, integrated liquid metal-based stretchable sensors and standalone systems

Possessing a unique combination of properties that are traditionally contradictory in other natural or synthetical materials, Ga-based liquid metals (LMs) exhibit low mechanical stiffness and flowability like a liquid, with good electrical and thermal conductivity like metal, as well as good biocompatibility and room-temperature phase transformation. These remarkable properties have paved the way for the development of novel reconfigurable or stretchable electronics and devices. Despite these outstanding properties, the easy oxidation, high surface tension, and low rheological viscosity of LMs have presented formidable challenges in high-resolution patterning. To address this challenge, various surface modifications or additives have been employed to tailor the oxidation state, viscosity, and patterning capability of LMs. One effective approach for LM patterning is breaking down LMs into microparticles known as liquid metal particles (LMPs). This facilitates LM patterning using conventional techniques such as stencil, screening, or inkjet printing. Judiciously formulated photo-curable LMP inks or the introduction of an adhesive seed layer combined with a modified lift-off process further provide the micrometer-level LM patterns. Incorporating porous and adhesive substrates in LM-based electronics allows direct interfacing with the skin for robust and long-term monitoring of physiological signals. Combined with self-healing polymers in the form of substrates or composites, LM-based electronics can provide mechanical-robust devices to heal after damage for working in harsh environments. This review provides the latest advances in LM-based composites, fabrication methods, and their novel and unique applications in stretchable or reconfigurable sensors and resulting integrated systems. It is believed that the advancements in LM-based material preparation and high-resolution techniques have opened up opportunities for customized designs of LM-based stretchable sensors, as well as multifunctional, reconfigurable, highly integrated, and even standalone systems.

Photoluminescent Self-Healable Waterborne Polyurethane/Mo and S Codoped Graphitic Carbon Nitride Nanocomposite with Bioimaging and Encryption Capability

Creating polymers that combine various functions within a single system expands the potential applications of such polymeric materials. However, achieving polymer materials that possess simultaneously elevated strength, toughness, and self-healing capabilities, along with special properties, remains a significant challenge. The present study demonstrates the preparation of S and Mo codoped graphitic carbon nitride (g-C3N4) (Mo@S-CN) nanohybrid and the fabrication of self-healing waterborne polyurethane (SHWPU)/Mo@S-CN (SHWPU/NS) nanocomposites for advanced applications. Mo@S-CN is an intriguing combination of g-C3N4 nanosheets and molybdenum oxide (MoOx) nanorods, forming a complex lamellar structure. This unique arrangement significantly improves the inborn properties of SHWPU to an impressive degree, especially mechanical strength (28.37-34.11 MPa), fracture toughness (73.65-140.98 MJ m-2), and thermal stability (340.17-348.01 °C), and introduces fluorescence activity into the matrix. Interestingly, a representative SHWPU/NS0.5 film is so tough that a dumbbell of 15 kg, which is 53,003 times heavier than the weight of the film, can be successfully lifted without any significant crack. Remarkably, fluorescence activity is developed because of electronic excitations occurring within the repeating polymeric tris-triazine units of the Mo@S-CN nanohybrid. This fascinating feature was effectively harnessed by assessing the usability of aqueous dispersions of the Mo@S-CN nanohybrid and photoluminescent SHWPU/NS nanocomposites as sustainable stains for bioimaging of human dermal fibroblast cells and anticounterfeiting materials, respectively. The in vitro fluorescence tagging test showed blue emission from 365 nm excitation, green emission from 470 nm excitation, and red emission from 545 nm excitation. Most importantly, in vitro hemocompatibility assessment, in vitro cytocompatibility, cell proliferation assessment, and cellular morphology assessment supported the biocompatibility nature of the Mo@S-CN nanohybrid and SHWPU/NS nanocomposites. Thus, these materials can be used for advanced applications including bioimaging.

Computational design of ultra-robust strain sensors for soft robot perception and autonomy

Compliant strain sensors are crucial for soft robots' perception and autonomy. However, their deformable bodies and dynamic actuation pose challenges in predictive sensor manufacturing and long-term robustness. This necessitates accurate sensor modelling and well-controlled sensor structural changes under strain. Here, we present a computational sensor design featuring a programmed crack array within micro-crumples strategy. By controlling the user-defined structure, the sensing performance becomes highly tunable and can be accurately modelled by physical models. Moreover, they maintain robust responsiveness under various demanding conditions including noise interruptions (50% strain), intermittent cyclic loadings (100,000 cycles), and dynamic frequencies (0-23 Hz), satisfying soft robots of diverse scaling from macro to micro. Finally, machine intelligence is applied to a sensor-integrated origami robot, enabling robotic trajectory prediction (<4% error) and topographical altitude awareness (<10% error). This strategy holds promise for advancing soft robotic capabilities in exploration, rescue operations, and swarming behaviors in complex environments.

Self-healing and shape-memory polymers based on cellulose acetate matrix

The creation of self-healing polymers with superior strength and stretchability from biodegradable materials is attracting increasing attention. In this study, we synthesized new biomass-derived cellulose acetate (CA) derivatives by ring-opening graft polymerization of δ-valerolactone followed by the introduction of ureidopyrimidinone (Upy) groups in the polymer side chains. Due to the semicrystalline aliphatic characteristics of the side chain poly(δ-valerolactone) (PVL) and quadruple hydrogen bonds formed by the Upy groups, the stretchability of the resulting polymers was significantly enhanced. Moreover, the shape memory ability and self-healing property (58.3% of self-healing efficiency) were successfully imparted to the polymer. This study demonstrates the great significance of using biomass sources to create self-healing polymers.

Novel Radiochromic Elastomer Dosimeter Based on the Self-Sensitizing Effect of Disulfide Bonds

γ-Irradiation is a kind of high-energy ionizing ray, which has widespread applications in material, food, and medical industries as well as in the environment. Since this irradiation is invisible, quantitatively monitoring its exposure doses is crucial to irradiated targets. As a type of dosimeter, radiochromic dosimeters can detect γ-irradiation by color changing, and its strategy to realize the radiochromic behavior basically relies on active radicals from radiolysis of an external environmental medium. However, the primary problem of this external environment-mediated sensitization strategy is that it complicates the components of dosimeters. Herein, we present a novel type of self-sensitizing radiochromic poly(urethane-urea) elastomers (PUUEs), where disulfide bonds, serving as radiation-responsive and sensitizing units, are introduced. This is the first attempt to utilize radicals generated from radiolysis of weak bonds in a solid polymer matrix to sensitize color change of dye-doped radiochromic dosimeters. Moreover, it is intriguing that the simultaneously introduced aryl hydrazone bond endows dosimeters with excellent color retention and maintains the Δa* value of 72.9% even after 1 month on the basis of the as-irradiated specimen. Besides, the metathesis of disulfide bonds not only endows dosimeters with better self-healing capability, but also accelerates the postcuring behavior and hydrogen bond reconfiguration, resulting in improved mechanical performance.

Materials-Driven Soft Wearable Bioelectronics for Connected Healthcare

In the era of Internet-of-things, many things can stay connected; however, biological systems, including those necessary for human health, remain unable to stay connected to the global Internet due to the lack of soft conformal biosensors. The fundamental challenge lies in the fact that electronics and biology are distinct and incompatible, as they are based on different materials via different functioning principles. In particular, the human body is soft and curvilinear, yet electronics are typically rigid and planar. Recent advances in materials and materials design have generated tremendous opportunities to design soft wearable bioelectronics, which may bridge the gap, enabling the ultimate dream of connected healthcare for anyone, anytime, and anywhere. We begin with a review of the historical development of healthcare, indicating the significant trend of connected healthcare. This is followed by the focal point of discussion about new materials and materials design, particularly low-dimensional nanomaterials. We summarize material types and their attributes for designing soft bioelectronic sensors; we also cover their synthesis and fabrication methods, including top-down, bottom-up, and their combined approaches. Next, we discuss the wearable energy challenges and progress made to date. In addition to front-end wearable devices, we also describe back-end machine learning algorithms, artificial intelligence, telecommunication, and software. Afterward, we describe the integration of soft wearable bioelectronic systems which have been applied in various testbeds in real-world settings, including laboratories that are preclinical and clinical environments. Finally, we narrate the remaining challenges and opportunities in conjunction with our perspectives.

Tough soldering for stretchable electronics by small-molecule modulated interfacial assemblies

The rapid-developing soft robots and wearable devices require flexible conductive materials to maintain electric functions over a large range of deformations. Considerable efforts are made to develop stretchable conductive materials; little attention is paid to the frequent failures of integrated circuits caused by the interface mismatch of soft substrates and rigid silicon-based microelectronics. Here, we present a stretchable solder with good weldability that can strongly bond with electronic components, benefiting from the hierarchical assemblies of liquid metal particles, small-molecule modulators, and non-covalently crosslinked polymer matrix. Our self-solder shows high conductivity (>2×105  S  m-1), extreme stretchability (~1000%, and >600% with chip-integrated), and high toughness (~20 MJ m-3). Additionally, the dynamic interactions within our solder's surface and interior enable a range of unique features, including ease of integration, component substitution, and circuit recyclability. With all these features, we demonstrated an application as thermoforming technology for three-dimensional (3D) conformable electronics, showing potential in reducing the complexity of microchip interfacing, as well as scalable fabrication of chip-integrated stretchable circuits and 3D electronics.

Highly Stretchable Stress-Strain Sensor from Elastomer Nanocomposites with Movable Cross-links and Ketjenblack

Practical applications like very thin stress-strain sensors require high strength, stretchability, and conductivity, simultaneously. One of the approaches is improving the toughness of the stress-strain sensing materials. Polymeric materials with movable cross-links in which the polymer chain penetrates the cavity of cyclodextrin (CD) demonstrate enhanced strength and stretchability, simultaneously. We designed two approaches that utilize elastomer nanocomposites with movable cross-links and carbon filler (ketjenblack, KB). One approach is mixing SC (a single movable cross-network material), a linear polymer (poly(ethyl acrylate), PEA), and KB to obtain their composite. The electrical resistance increases proportionally with tensile strain, leading to the application of this composite as a stress-strain sensor. The responses of this material are stable for over 100 loading and unloading cycles. The other approach is a composite made with KB and a movable cross-network elastomer for knitting dissimilar polymers (KP), where movable cross-links connect the CD-modified polystyrene (PSCD) and PEA. The obtained composite acts as a highly sensitive stress-strain sensor that exhibits an exponential increase in resistance with increasing tensile strain due to the polymer dethreading from the CD rings. The designed preparations of highly repeatable or highly responsive stress-strain sensors with good mechanical properties can help broaden their application in electrical devices.

Self-healing polymers through hydrogen-bond cross-linking: synthesis and electronic applications

Recently, polymers capable of repeatedly self-healing physical damage and restoring mechanical properties have attracted extensive attention. Among the various supramolecular chemistry, hydrogen-bonding (H-bonding) featuring reversibility, directionality and high per-volume concentration has become one of the most attractive directions for the development of self-healing polymers (SHPs). Herein, we review the recent advances in the design of high-performance SHPs based on different H-bonding types, for example, H-bonding motifs and excessive H-bonding. In particular, the effects of the structural design of SHPs on their mechanical performance and healing efficiency are discussed in detail. Moreover, we also summarize how to employ H-bonding-based SHPs for the preparation of self-healable electronic devices, focusing on promising topics, including energy harvesting devices, energy storage devices, and flexible sensing devices. Finally, the current challenges and possible strategies for the development of H-bonding-based SHPs and their smart electronic applications are highlighted.

A strain-reinforcing elastomer adhesive with superior adhesive strength and toughness

Strong and ductile adhesives often undergo both interfacial and cohesive failure during the debonding process. Herein, we report a rare self-reinforcing polyurethane adhesive that shows the different phenomenon of only interfacial failure yet still exhibiting superior adhesive strength and toughness. It is synthesized by designing a hanging adhesive moiety, hierarchical H-bond moieties, and a crystallizable soft segment into one macromolecular polyurethane. The former hanging adhesive moiety allows the hot-melt adhesive to effectively associate with the target substrate, providing sufficient adhesion energy; the latter hierarchical H-bond moieties and a crystallizable soft segment cooperate to enable the adhesive to undergo large lap-shear deformations through sacrificing weak bonds and mechano-responsive strength through the fundamental mechanism of strain-induced crystallization. As a result, this polyurethane adhesive can keep itself intact during the debonding process while still withstanding a high lap-shear strength and dissipating tremendous stress energy. Its adhesive strength and work of debonding are as high as 11.37 MPa and 10.32 kN m-1, respectively, outperforming most reported tough adhesives. This self-reinforcing adhesive is regarded as a new member of the family of strong and ductile adhesives, which will provide innovative chemical and structural inspirations for future conveniently detachable yet high-performance adhesives.

Toward Highly Matching the Dura Mater: A Polyurethane Integrating Biocompatible, Leak-Proof, and Self-Healing Properties

The dura mater is the final barrier against cerebrospinal fluid leakage and plays a crucial role in protecting and supporting the brain and spinal cord. Head trauma, tumor resection and other traumas damage it, requiring artificial dura mater for repair.  However, surgical tears are often unavoidable. To address these issues, the ideal artificial dura mater should have biocompatibility, anti-leakage, and self-healing properties. Herein, this work has used biocompatible polycaprolactone diol as the soft segment and introduced dynamic disulfide bonds into the hard segment, achieving a multifunctional polyurethane (LSPU-2), which integrated the above mentioned properties required in surgery. In particular, LSPU-2 matches the mechanical properties of the dura mater and the biocompatibility tests with neuronal cells demonstrate extremely low cytotoxicity and do not cause any negative skin lesions. In addition, the anti-leakage properties of the LSPU-2 are confirmed by the water permeability tester and the 900 mm H2 O static pressure test with artificial cerebrospinal fluid. Due to the disulfide bond exchange and molecular chain mobility, LSPU-2 could be completely self-healed within 115 min at human body temperature. Thus, LSPU-2 comprises one of the most promising potential artificial dura materials, which is essential for the advancement of artificial dura mater and brain surgery.

High-Performance Branched Polymer Elastomer Based on a Topological Network Structure and Dynamic Bonding

High performance has always been the research focus of elastomers. However, there are inherent conflicts among properties of elastomers, such as strength and toughness, strength and damping performance, strength and self-healing ability, etc. Herein, first, we synthesized a unique structure of the dangling chain containing proton donors and receptors. Then, we design and fabricate a kind of high-performance elastomer with a gradient distribution of a dangling chain and a dynamic bond structure. The dangling chains of different lengths intertwine with each other and self-assemble to form a "dense accumulation" structure driven by hydrogen bonds, and the elastomer exhibits special micro/nano scale aggregated states and microphase separation. The "dense accumulation" structure plays a vital role in the increase of mechanical properties. Meanwhile, under the joint action of a dangling chain and a dynamic bond, the damping performance and self-healing performance of the elastomer are greatly enhanced. High strength (27.5 MPa), toughness (121.9 MJ·m-3), 94.8% healing efficiency and outstanding damping performance (tan δ ≥ 0.4, high damping temperature range up to 144 °C) are simultaneously achieved beyond the current state-of-the-art. This topoarchitected polymer with a gradient distribution of dangling chains successfully solves the defects of conventional branched polymers in deteriorating their mechanical properties. This material design provides a new strategy for the development of high-performance structural and functional integrated elastomers.

Spatiotemporally Responsive Hydrogel Dressing with Self-Adaptive Antibacterial Activity and Cell Compatibility for Wound Sealing and Healing

Adhesive hydrogels containing quaternary ammonium salt (QAS) moieties have shown attractive advantages in treatment for acute wounds, attributed to their high performances in wound sealing and sterilization. However, the introduction of QAS commonly leads to high cytotoxicity and adhesive deterioration. Herein, aimed to solve these two issues, a self-adaptive dressing with delicate spatiotemporal responsiveness is developed by employing cellulose sulfate (CS) as dynamic layers to coat QAS-based hydrogel. In detail, due to the acid environment of wound in the early stages of healing, the CS coating will quickly detach to expose the active QAS groups for maximum disinfectant efficacy; meanwhile, as the wound gradually heals and recovers to a neutral pH, the CS will remain stable to keep QAS screened, realizing a high cell growth-promoting activity for epithelium regeneration. Additionally, attributed to the synergy of temporary hydrophobicity by CS and slow water absorption kinetics of the hydrogel, the resultant dressing possesses outstanding wound sealing and hemostasis performance. At last, this work anticipates this approach to intelligent wound dressings based on dynamic and responsive intermolecular interaction can also be applied to a wide range of self-adaptive biomedical materials employing different chemistries for applications in medical therapy and health monitoring.

Construction of Wearable Touch Sensors by Mimicking the Properties of Materials and Structures in Nature

Wearable touch sensors, which can convert force or pressure signals into quantitative electronic signals, have emerged as essential smart sensing devices and play an important role in various cutting-edge fields, including wearable health monitoring, soft robots, electronic skin, artificial prosthetics, AR/VR, and the Internet of Things. Flexible touch sensors have made significant advancements, while the construction of novel touch sensors by mimicking the unique properties of biological materials and biogenetic structures always remains a hot research topic and significant technological pathway. This review provides a comprehensive summary of the research status of wearable touch sensors constructed by imitating the material and structural characteristics in nature and summarizes the scientific challenges and development tendencies of this aspect. First, the research status for constructing flexible touch sensors based on biomimetic materials is summarized, including hydrogel materials, self-healing materials, and other bio-inspired or biomimetic materials with extraordinary properties. Then, the design and fabrication of flexible touch sensors based on bionic structures for performance enhancement are fully discussed. These bionic structures include special structures in plants, special structures in insects/animals, and special structures in the human body. Moreover, a summary of the current issues and future prospects for developing wearable sensors based on bio-inspired materials and structures is discussed.

Intrinsic Self-Healing Chemistry for Next-Generation Flexible Energy Storage Devices

The booming wearable/portable electronic devices industry has stimulated the progress of supporting flexible energy storage devices. Excellent performance of flexible devices not only requires the component units of each device to maintain the original performance under external forces, but also demands the overall device to be flexible in response to external fields. However, flexible energy storage devices inevitably occur mechanical damages (extrusion, impact, vibration)/electrical damages (overcharge, over-discharge, external short circuit) during long-term complex deformation conditions, causing serious performance degradation and safety risks. Inspired by the healing phenomenon of nature, endowing energy storage devices with self-healing capability has become a promising strategy to effectively improve the durability and functionality of devices. Herein, this review systematically summarizes the latest progress in intrinsic self-healing chemistry for energy storage devices. Firstly, the main intrinsic self-healing mechanism is introduced. Then, the research situation of electrodes, electrolytes, artificial interface layers and integrated devices based on intrinsic self-healing and advanced characterization technology is reviewed. Finally, the current challenges and perspective are provided. We believe this critical review will contribute to the development of intrinsic self-healing chemistry in the flexible energy storage field.