Skin-like mechanoresponsive self-healing ionic elastomer from supramolecular zwitterionic network

Solvent Polarity-Induced Ultrahigh Strength Supramolecular Polyzwitterionic Organogels with Impact-Stiffening, Damping, and Anti-Freezing Properties

Widely used polyzwitterionic hydrogels usually suffer from significant mechanical loss, owing to the strong hydration of the zwitterionic groups. Herein, a novel solvent polarity-induced strategy is introduced for developing pure supramolecular polyzwitterionic organogels with ultrahigh strength by using a facile one-pot synthesis process. The mechanical properties of these polyzwitterionic organogels can be well-tuned by adjusting the polarity of dihydric alcohol solvents to regulate hydrogen bonding and dipole-dipole interactions between polymer chains in the organogel network. The polyzwitterionic organogels exhibit superior mechanical properties, including a tensile strength of 1.5 MPa, elongation at break of 669%, toughness of 3.2 MJ m- 3, and adhesive strength of 506 kPa. Additionally, the polyzwitterionic organogels display outstanding impact response performance (maximum strain-stiffening ratio of 140 times, and maximum impact-stiffening ratio of 450 times) and energy dissipation properties (energy dissipation ratio of above 60%, and maximum loss factor of 2.0 at 1 Hz), resulting from the presence of inter-molecular internal friction. Notably, the synergistic interactions between zwitterionic groups on polymer side chains and the organic solvents impart these organogels with mechanical flexibility and vibration absorption capabilities even in low-temperature environments. Furthermore, the polyzwitterionic organogels demonstrate flaw-insensitivity, self-healing ability, and water processability, broadening their applicability to more complex conditions.

Antifreezing hydrogels: from mechanisms and strategies to applications

Antifreezing hydrogels have emerged as an innovative solution for maintaining functional performance and mechanical integrity in subzero environments, offering a robust alternative to traditional water-free antifreezing materials that often fail under wet and cold conditions. These water-rich hydrogels leverage their porous, crosslinked, polymeric networks, which serve as the structural basis for implementing two parallel strategies: the incorporation of antifreezing additives (peptides/proteins, salts, ionic liquids, and organics) and the meticulous engineering of polymer systems and network structures for manipulating the water-ice phase equilibrium to significantly enhance antifreezing properties. This review synthesizes recent findings to provide a fundamental overview of the important advancements in antifreezing hydrogels, focusing on their designs, mechanisms, performances, and functional applications. Various types of antifreezing hydrogels have been developed, utilizing strategies like the incorporation of antifreeze agents, use of strongly water-bound polymers, and design of highly crosslinked networks to illustrate different antifreezing mechanisms: freezing point depression, ice recrystallization inhibition, and network freezing inhibition. This review also explores the diverse functions of antifreezing hydrogels in biomedical devices, soft robotics, flexible electronics, food industry, and environmental engineering. Finally, this review concludes with future directions, emphasizing the potential of integrating machine learning and advanced molecular simulations into materials design. This strategic vision is aimed at promoting continuous innovation and progress in the rapidly evolving field of antifreezing hydrogels.

Thermo-responsive and phase-separated hydrogels for cardiac arrhythmia diagnosis with deep learning algorithms

Adhesive epidermal hydrogel electrodes are essential for achieving robust signal transduction and cardiac arrhythmia diagnosis, but detachment of conventional adhesive dressings easily causes secondary damage to delicate wound tissues due to lack of programmable capability of changed adhesion. Herein, we developed hydrogel-based skin-interfacing electrodes capable of on-demand programmable adhesion and detachment to capture electrocardiogram signals for diagnosing cardiac arrhythmia. This was achieved by integrating dynamic multiscale contact and coordinated regulation through temperature-mediated switchable hydrogen bond interactions in phase-separated smart hydrogels. Through micro-scale regulation of adhesive molecules and meso-scale modulation of the modulus, the hydrogel electrodes can be rapidly transited between a slippery state (adhesion ∼1.3 N/m) and a sticky one (adhesion ∼110 N/m) during its peeling from skin. This achieves an 84.5-fold increase of on/off adhesive energy (or reducing the adhesion at the skin interface by 98%) at low temperatures compared to normal skin temperature. A real-time cloud platform was developed by integrating hydrogel electrodes, enabling remote electrocardiogram (ECG) monitoring. For clinical applications, such developed skin sensing platform effectively captured cardiac activities in patients with eight common arrhythmias, achieving by the recorded high-fidelity and analyzable electrical signals. With the assistance of deep learning algorithms, we demonstrated a wearable cardiac arrhythmia intelligent diagnosis system which enables real-time conversion of the collected ECG data into diagnostic evaluations with a recognition accuracy of 98.5%.

Kinetic Insight into the Formation of Physically Robust Molecular Network in Cellulose Hydrogels

Sol-gel method unlocks the enormous potential of utilizing abundant and renewable cellulose resources. However, the molecular-level structural evolution during the cellulose gelation process is less well understood, bringing challenges for achieving high performance of cellulose hydrogels by regulating their molecular network. Herein, a fascinating journey is unveiled through time-resolved in situ techniques for the evolution of the hierarchical structure of cellulose from micro to molecular scale during the gelation process. The two-regime gelation mechanism of cellulose is proposed. Unexpectedly, it is discovered that the polarity of anti-solvents could effectively control the gelation kinetics and manipulate the molecular network of cellulose hydrogels. As a result, the performance of cellulose hydrogels can be purposefully customized, which are either robust and elastic, or tough and high-damping. Understanding the gelation mechanism of cellulose and its structural evolution kinetics unlocks the pathways to exceptional performance and multifunctionality, which will foster potential advances in sustainable cellulose-based hydrogels.

Bio-Based Thermoplastic Room Temperature Phosphorescent Materials with Closed-Loop Recyclability

Producing thermoplastic room temperature phosphorescent (RTP) materials with closed-loop recyclability from natural sources is an attractive approach but hard to achieve. Here, the study develops such RTP materials, Poly(TA)/Cell, by thermally polymerizing thioctic acid in the presence of cellulose. Specifically, polymerized thioctic acid poly(TA) forms strong hydrogen bonding interactions with CNF, promoting formation of molecular clusters between the oxygen-containing units. The as-formed clusters generate humidity- and excitation-sensitive green RTP emission. Red afterglow emission is also obtained by integrating Poly(TA)/Cell together with Rhodamine B (RhB) via an energy transfer process. Attributed to the thermoplastic properties, the as-obtained Poly(TA)/Cell can be thermally molded into flexible shapes with uncompromised RTP performance. Moreover, owing to the alkali-cleavable properties of the disulfide bond in Poly(TA)/Cell, thioctic acid and cellulose can be successfully recycled from Poly(TA)/Cell with a yield of 92.3% and 81.5%, respectively. As a demonstrator for potential utility, Poly(TA)/Cell is used to fabricate materials for information encryption.

Jellyfish-Inspired Ultrastretchable, Adhesive, Self-Healing, and Photoswitchable Fluorescent Ionic Skin Enabled by a Supramolecular Zwitterionic Network

Ionic hydrogels suit ionic skins, but advanced hydrogels are challenging. Inspired by jellyfish, we developed an ionic hydrogel with ultrastretchability, conductivity, adhesion, self-healing, and photoswitchable fluorescence via a supramolecular zwitterionic network. This hydrogel consists of silk fibroin, zwitterionic betaine analogue, biomineral calcium salts, and spiropyran in a dynamically cross-linked macromolecular network. Calcium ions facilitate electrical signal transmission and ionic interactions, while spiropyran enables photoswitchable color and fluorescence. Density functional theory and Fourier transform infrared analysis reveal abundant hydrogen bonding, ionic associations, and van der Waals forces, contributing to stretchability, adhesion, and self-healing, making them ideal for epidermal electrodes. The hydrogel also shows potential in optical printing and anti-counterfeiting applications due to spiropyran's reversible photochromic and photoluminescent behaviors. Moreover, a jellyfish-like robot capable of electric-driven movement is created by using these features. This study enhances understanding of dynamic noncovalent interactions in zwitterionic networks, enriching hydrogel design principles and advancing intelligent ionic skins.

Design of Hydrogel Electrolytes Using Strong Bacterial Cellulose with Weak Ionic Interactions

Hydrogel electrolytes with both high ionic conductivity and sufficient mechanical strength are in great demand but remain a long-standing challenge. Here, we report a simple method to fabricate highly conductive and strong hydrogels (IBVA) by leveraging a layered cellulose network with weak ionic interactions. Specifically, bacterial cellulose (BC) membranes with high crystallinity and mechanical strength are employed as the strong skeletons of the hydrogel matrix. Simultaneously, formate anions with a salting-in effect are introduced to tune the aggregation states of polymer chains, endowing the hydrogel with weak hydrogen bonding, and finally forming a "hard-soft-hard" interlocking hierarchical structure. This strategy enables the hydrogel to achieve an ultrahigh ionic conductivity of 105 ± 5 mS cm-1, alongside satisfying mechanical strength (0.78 MPa), outperforming most reported hydrogel electrolytes. Furthermore, the IBVA hydrogel was successfully demonstrated as an electrolyte for supercapacitors, exhibiting the favorable flexibility, broad temperature adaptability, interfacial stability, and stable electrochemical performance. Our proposed method establishes a framework for engineering high-performance hydrogel electrolytes tailored for flexible electronics.

Self-Maintainable Electronic Materials with Skin-Like Characteristics Enabled by Graphene-PEDOT:PSS Fillers

Conventional devices lack the adaptability and responsiveness inherent in the design of nature. Therefore, they cannot autonomously maintain themselves in natural environments. This limitation is primarily because of using rigid and fragile material components for their construction, which hinders their ability to adapt and evolve in changing environments. Moreover, they often cannot self-repair after injuries or significant damage. Even devices with self-healing, soft, and responsive properties often fail to seamlessly integrate all these attributes into a single, scalable, and cohesive platform. In this study, a significant breakthrough is introduced by utilizing graphene-poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (graphene-PEDOT:PSS) fillers to transform a typically weak, insulating, and jelly-like material into a soft electronic material with properties akin to those of living organisms, such as skin tissue. The developed electronic materials exhibit a range of other capabilities attributed to the hierarchical organization originating from filler enhancement, which includes methods such as heat regulation, 3D printability, and multiplex sensing. The introduction of this new class of materials can facilitate the self-maintenance of life-like soft robots and bioelectronics that can be seamlessly integrated within dynamic environments, such as the human body, while demonstrating the ability to sense, respond, and adapt to challenging environments.

Scalable Preparation of Polyzwitterionic Hydrogels Based on Hydration Shielding-Accelerated Redox Self-Catalytic Polymerization (HS-A-RP)

Traditional synthesis methods for polyzwitterionic hydrogels involve harsh conditions, such as thermal or UV irradiation, prolonged durations, and high monomer concentrations. Herein, we address these challenges at the meantime by proposing a novel chemical method, called hydration-shielding accelerated self-catalytic polymerization (HS-A-RP), facilitating the preparation of polyzwitterionic hydrogels. The discovery is that polyvinyl alcohol (PVA) chains can generate hydration shielding around hydrated zwitterionic monomers, promoting their effective aggregation and rapid crosslinking polymerization under the assistance of silver ions (Ag+)-potassium persulfate (S2O8 2-) redox catalyst. The HS-A-RP method performs under mild condition (-5 °C to 37 °C) without extra energy, overcomes the critical monomer polymerization concentration limitation (wt%: 0.3%), and completes within an ultrashort polymerization time (<60 s). The prepared polyzwitterionic hydrogels possesses a denser network and superior mechanical properties compared to those prepared by traditional thermal/UV methods, exhibiting good antiswelling behavior, excellent lubrication performance, and significant antibacterial and anti-fouling properties. These significant advances endow HS-A-RP with attractive application potentials in manufacturing functional hydrogel coatings for biomedical device, in situ encapsulation of thermally sensitive materials, and excellent sand fixation abilities. Moreover, HS-A-RP method is suitable for scalable manufacture and decorative coating of polyzwitterionic hydrogels on diverse substrates in extreme environmental conditions.

High-voltage water-scarce hydrogel electrolytes enable mechanically safe stretchable Li-ion batteries

Soft Li-ion batteries, based on conventional organic electrolytes, face performance degradation challenges due to moisture penetration and safety concerns due to possible leakage of toxic fluorine compounds and flammable solvents under mechanical damage. We design a water-scarce hydrogel electrolyte with fluorine-free lithium salt to achieve wide electrochemical stability window (up to 3.11 volts) in ambient air without hermetic packaging while balancing high stretchability (1348%), ion conductivity (41 millisiemens per centimeter), and self-healing capabilities for mechanically and chemically safe stretchable Li-ion batteries. Molecular synergy between hydrophilicity and lithiophilicity of zwitterionic polymer backbone is revealed by molecular dynamics simulations. The battery exhibits capacity retention under harsh mechanical stresses-enduring stretching, twisting, folding, and multiple through-punctures by a needle-while self-healing from repeated through cuts by a razor blade. Stable ambient operation for 1 month over 500 charge-discharge cycles (average coulomb efficiency, 95%) is achieved. A prototype self-healing electronic system with embedded soft batteries demonstrates practical application as a durable embodied energy source.

High-Conductivity, Self-Healing, and Adhesive Ionic Hydrogels for Health Monitoring and Human-Machine Interactions Under Extreme Cold Conditions

Ionic conductive hydrogels (ICHs) are emerging as key materials for advanced human-machine interactions and health monitoring systems due to their unique combination of flexibility, biocompatibility, and electrical conductivity. However, a major challenge remains in developing ICHs that simultaneously exhibit high ionic conductivity, self-healing, and strong adhesion, particularly under extreme low-temperature conditions. In this study, a novel ICH composed of sulfobetaine methacrylate, methacrylic acid, TEMPO-oxidized cellulose nanofibers, sodium alginate, and lithium chloride is presented. The hydrogel is designed with a hydrogen-bonded and chemically crosslinked network, achieving excellent conductivity (0.49 ± 0.05 S m-1), adhesion (36.73 ± 2.28 kPa), and self-healing capacity even at -80 °C. Furthermore, the ICHs maintain functionality for over 45 days, showcasing outstanding anti-freezing properties. This material demonstrates significant potential for non-invasive, continuous health monitoring, adhering conformally to the skin without signal crosstalk, and enabling real-time, high-fidelity signal transmission in human-machine interactions under cryogenic conditions. These ICHs offer transformative potential for the next generation of multimodal sensors, broadening application possibilities in harsh environments, including extreme weather and outer space.

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.

Enhanced Carbon Nanotube Ionogels for High-Performance Wireless Strain Sensing

Ionogels, as emerging stretchable conductor materials, have garnered significant attention for their potential applications in flexible electronics, particularly in wearable strain sensors. However, a persistent challenge in optimizing ionogels lies in achieving a balance between enhanced mechanical properties and electrical conductivity. In this study, we successfully addressed this challenge by incorporating carbon nanotubes (CNTs) into ionogels, achieving a simultaneous improvement in the electrical conductivity (2.67 mS/cm) and mechanical properties (400.83 kPa). The CNTs served dual purposes, acting as a continuous conductive pathway to facilitate electrical signal transmission and as reinforcing nanotubes to bolster the mechanical robustness of the ionogels. Additionally, the polymer network, composed of acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA), established a purely physical cross-linking network characterized by dense hydrogen bonding, which ensured sufficient toughness within the ionogels. Notably, the assembled ionogels, when utilized as wireless strain sensors, demonstrated exceptional sensitivity in detecting subtle finger movements, with the CNTs significantly amplifying the electrical response. This work provides new insights into the integration of carbon nanotubes in ionogels, expanding their applications and pioneering a fresh approach to functionalized ionogel design.

Mechanics-Photophysics Correlation in Tough, Stretchable and Long-Lived Room Temperature Phosphorescence Ionogels Deciphered by Dynamic Mechanical Analysis

The development of tough, stretchable and long-lived room temperature phosphorescence (RTP) materials holds great significance for manufacturing and processing photoluminescent materials, but limited techniques are available to profile their mechanics-photophysics correlation. Here we report glassy ionogels, and their mechanical properties and photophysical properties are fused by dynamic mechanical analysis (DMA), functioning like a human brain that perceives a material instantaneously by linking sensory perception and cognition. Depending on two special temperatures presented in DMA curves, Tloss (the peak of loss modulus (E")) and Tg (glass transition temperature), the ionogels can vary from being either tough with persistent phosphorescence, extensible with effective phosphorescence or resilience with inefficient phosphorescence. Leveraging this method, we achieve stretchable and long-lived RTP ionogels with tensile yield strength of 53 MPa, tensile strain of 497 %, Young's modulus of 782 MPa, toughness of 111.2 MJ/m3, and lifetime of 113.05 ms. Our work provides a simple yet powerful method to reveal the mechanics-photophysics correlation of RTP ionogels, to predict their performance without laborious synthesis and characterization, opening new avenues for applications of RTP materials, including applications in harsh conditions (257 K or 347 K), shape memory and shape reconstruction.

Observation of topological hydrogen-bonding domains in physical hydrogel for excellent self-healing and elasticity

Physical hydrogels, three-dimensional polymer networks with reversible cross-linking, have been widely used in many developments throughout the history of mankind. However, physical hydrogels face significant challenges in applications due to wound rupture and low elasticity. Some self-heal wounds with strong ionic bond throughout the network but struggle to immediately recover during cyclic operation. In light of this, a strategy that achieves both self-healing and elasticity has been developed through the construction of topological hydrogen-bonding domains. These domains are formed by entangled button-knot nanoscale colloids of polyacrylic-acid (PAA) with an ultra-high molecular weight up to 240,000, further guiding the polymerization of polyacrylamide to reinforce the hydrogel network. The key for such colloids is the self-assembly of PAA fibers, approximately 4 nm in diameter, and the interconnecting PAA colloids possess high strength, simultaneously acting as elastic scaffold and reversibly cross-linking near wounds. The hydrogel completely recovers mechanical properties within 5 h at room temperature and consistently maintains >85% toughness in cyclic loading. After swelling, the hydrogel has 96.1 wt% of water content and zero residual strain during cycling. Such physical hydrogel not only provides a model system for the microstructural engineering of hydrogels but also broadens the scope of potential applications.

Hybrid Zwitterionic Hydrogels with Encoded Differential Swelling and Programmed Deformation for Small-Scale Robotics

Stimuli-responsive shape-morphing hydrogels with self-healing and tunable physiochemical properties are excellent candidates for functional building blocks of untethered small-scale soft robots. With mechanical properties similar to soft organs and tissues, such robots enable minimally invasive medical procedures, such as cargo/cell transportation. In this work, responsive hydrogels based on zwitterionic/acrylate chemistry with self-healing and stimuli-responsiveness are synthesized. Such hydrogels are then judiciously cut and pasted to form hybrid constructs with predetermined swelling and elastic anisotropy. This method is used to program hydrogel constructs with predetermined 2D-to-3D deformation upon exposure to different environmental ionic strengths. Untethered soft robotic functionalities are demonstrated, such as actuation, magnetic locomotion, and targeted transport of soft and light cargo in flooded media. The proposed hydrogel expands the repertoire of functional materials for fabricating small-scale soft robots.

Network design for soft materials: addressing elasticity and fracture resistance challenges

Soft materials, such as elastomers and gels, feature crosslinked polymer chains that provide stretchable and elastic mechanical properties. These properties are derived from entropic elasticity, which limits energy dissipation and makes the material susceptible to fracture. To address this issue, network designs that dissipate energy through the plastic zone have been introduced to enhance toughness; however, this approach compromises elasticity, preventing the material from fully recovering its original shape after deformation. In this review, we describe the trade-off between fracture resistance and elasticity, exploring network designs that overcome this limitation to achieve both high toughness and low hysteresis. The development of soft materials that are both elastic and fracture-resistant holds significant promise for applications in stretchable electronics, soft robotics, and biomedical devices. By analyzing successful network designs, we identify strategies to further improve these materials and discuss potential enhancements based on existing limitations.

Biointerface engineering of flexible and wearable electronics

Biointerface sensing is a cutting-edge interdisciplinary field that merges conceptual and practical aspects. Wearable bioelectronics enable efficient interaction and close contact with biological components such as tissues and organs, paving the way for a wide range of medical applications, including personal health monitoring and medical intervention. To be applicable in real-world settings, the patches must be stable and adhere to the skin without causing discomfort or allergies in both wet and dry conditions, as well as other desirable features such as being ultra-soft, thin, flexible, and stretchable. Biosensors have emerged as promising tools primarily used to directly detect biological and electrophysiological signals, enhancing the efficacy of personalized medical treatments and enabling accurate tracking of human well-being. This review highlights the engineering of skin-tissue surfaces/interfaces and their interactions with wearable patches, aiming for both a broad and in-depth understanding of the mechanical and physicochemical properties required for the advancement of flexible and wearable skin patches. Specifically, the advantages of flexible bioelectronics and sensors with optimized surface geometry for long-term diagnosis are discussed. This insight aims to guide the future development of functional materials that can interact with human tissue in a controlled manner. Finally, we provide perspectives on the challenges and potential applications of biointerface engineering in wearable devices.

A Wet-Adhesion and Swelling-Resistant Hydrogel for Fast Hemostasis, Accelerated Tissue Injury Healing and Bioelectronics

Hydrogel bioadhesives with adequate wet adhesion and swelling resistance are urgently needed in clinic. However, the presence of blood or body fluid usually weakens the interfacial bonding strength, and even leads to adhesion failure. Herein, profiting from the unique coupling structure of carboxylic and phenyl groups in one component (N-acryloyl phenylalanine) for interfacial drainage and matrix toughening as well as various electrostatic interactions mediated by zwitterions, a novel hydrogel adhesive (PAAS) is developed with superior tissue adhesion properties and matrix swelling resistance in challenging wet conditions (adhesion strength of 85 kPa, interfacial toughness of 450 J m-2, burst pressure of 514 mmHg, and swelling ratio of <4%). The PAAS hydrogel can not only realize fast hemostasis of liver, heart, artery rupture, and sealing of pulmonary air-leakage but also accelerate the recovery of stomach and liver defects in rat, rabbit, and pig models. Moreover, PAAS hydrogel can precisely and durably monitor various physiological activities (pulse, electrocardiogram, and electromyogram) even under humid environments (immersion in water for 3 days), and can be employed for the evaluation of in vivo sealing efficiency for artery rupture. The work provides a promising hydrogel adhesive for clinical hemostasis, tissue injury repair, and bioelectronics.

Adaptive Phase-Locked E-Skin for Sports Physiology and Medicine

The pursuit of creating materials that replicate the flexibility, stability, and advanced perceptual capabilities of human skin, attributes honed through natural evolution, represents a long-term objective in pioneering fields such as electronic skin (e-skin) research. However, conventional e-skin often struggles with stability and functionality in harsh sports environments, resulting in the degradation of the intimate interface over time. Inspired by the innate biphasic structure of human subcutaneous tissue, an adaptive phase-locked e-skin (APLE) is presented, designed to seamlessly conform to dynamic sports environments, offering robust applications in sports physiology and medical contexts without malfunctioning. The APLE allows one to laminate onto the skin with consistent homeostasis, providing a foundation for advancing data-driven sports physiology and creating personalized sports plans. Additionally, APLE offers immediate on-site medical treatment for common sports injuries, including hemostasis and sutureless wound closure. Ultimately, the reported multifunctional e-skin can provide significant value in managing sport-related burdens through digital and people-centered physiology monitoring, along with real-time sport healthcare.

Layered Double Hydroxide Nanosheets Incorporated Hierarchical Hydrogen Bonding Polymer Networks for Transparent and Fire-Proof Ceramizable Coatings

In recent decades, annual urban fire incidents, including those involving ancient wooden buildings burned, transportation, and solar panels, have increased, leading to significant loss of human life and property. Addressing this issue without altering the surface morphology or interfering with optical behavior of flammable materials poses a substantial challenge. Herein, we present a transparent, low thickness, ceramifiable nanosystem coating composed of a highly adhesive base (poly(SSS1-co-HEMA1)), nanoscale layered double hydroxide sheets as ceramic precursors, and supramolecular melamine di-borate as an accelerator. We demonstrate that this hybrid coating can transform into a porous, fire-resistant protective layer with a highly thermostable vitreous phase upon exposure to flame/heat source. A nanosystem coating of just ~ 100 μm thickness can significantly increase the limiting oxygen index of wood (Pine) to 37.3%, dramatically reduce total heat release by 78.6%, and maintain low smoke toxicity (CITG = 0.016). Detailed molecular force analysis, combined with a comprehensive examination of the underlying flame-retardant mechanisms, underscores the effectiveness of this coating. This work offers a strategy for creating efficient, environmentally friendly coatings with fire safety applications across various industries.

In Situ Anchoring Functional Molecules to Polymer Chains Through Supramolecular Interactions for a Robust and Self-Healing Multifunctional Waterborne Polyurethane

Nowadays, much attention is paid to the development of high-performance and multifunctional materials, but it is still a great challenge to obtain polymer materials with high mechanical properties, high self-healing properties, and multifunctionality in one. Herein, an innovative strategy is proposed to obtain a satisfactory waterborne polyurethane (PMWPU-Bx) by in situ anchoring 3-aminophenylboronic acid (3-APBA) in a pyrene-capped waterborne polyurethane (PMWPU) via supramolecular interactions. The multiple functional sites inherent in 3-APBA can produce supramolecular interactions with groups on PMWPU, promoting the aggregation of hard domains in the polymer network, which confers the PMWPU-Bx strength (7.9 MPa) and high modulus (243.2 MPa). Meanwhile, the dynamic natures of boronic ester bonds formed by the condensation of 3-APBA endow PMWPU-Bx with a high self-healing efficiency. Additionally, PMWPU-Bx exhibits fluorescence tunability due to the controlled π-π stacking. In this research, the strategy of anchoring functional molecules onto polymers through supramolecular interactions synchronously achieves the high performance and the multi-functionality of waterborne polyurethanes, but also broadens their potential applications in the fields of optical anticounterfeiting and encrypted information transmission.

Construction of gradient ionogels by self-floatable hyperbranched organosilicon crosslinkers for multi-sensing and wirelessly monitoring physiological signals

Monitoring complex human movements requires the simultaneous detection of strain and pressure, which poses a challenge due to the difficulty in integrating high stretchability and compressive ability into a single material. Herein, a series of hyperbranched polysiloxane crosslinkers (HPSis) with self-floating abilities are designed and synthesized. Taking advantage of the self-floating capabilities of HPSis, ionogels with gradient composition distribution and conductivities are constructed by in situ one-step photopolymerization, and possess satisfactory stretchability, high compressibility and excellent resilience. The gradient-ionogel-based strain sensor exhibits extraordinary pressure sensitivity (19.33 kPa-1), high strain sensitivity (GF reaches 2.5) and temperature sensing ability, enabling the monitoring of the angles and direction of joint movements, transmitting Morse code and wirelessly detecting bioelectrical signals. This study may inspire the design of development of multi-function flexible electronics.

Mechanically Resilient, Self-Healing, and Environmentally Adaptable Eutectogel-Based Triboelectric Nanogenerators for All-Weather Energy Harvesting and Human-Machine Interaction

Triboelectric nanogenerators (TENGs) have garnered significant attention for mechanical energy harvesting, self-powered sensing, and human-machine interaction. However, their performance is often constrained by materials that lack sufficient mechanical robustness, self-healing capability, and adaptability to environmental extremes. Eutectogels, with their inherent ionic conductivity, thermal stability, and sustainability, offer an appealing alternative as flexible TENG electrodes, yet they typically suffer from weak damage endurance and insufficient self-healing capability. To overcome these challenges, here, we introduce an internal-external dual reinforcement strategy (IEDRS) that enhances internal bonding dynamics within the eutectogel matrix, composed of glycidyl methacrylate and deep eutectic solvent, and integrates plant-derived lignin as an external reinforcer. Notably, the resultant eutectogel, named GLCL, exhibits appealing collection merits including superior mechanical robustness (1.53 MPa tensile stress and 1.85 MJ/m3 toughness), ultrastrong adhesion (4.76 MPa), high self-healing efficiency (84.7%), and significant environmental adaptability (-40 to 100 °C). These improvements ensure that the assembled triboelectric nanogenerator (GLCL-TENG) produces stable and robust electrical outputs, maintained even under dynamic and postdamage conditions. Additionally, the GLCL-TENG exhibits significant extreme environmental tolerance and durability, maintaining high and consistent electrical outputs over a wide temperature range (-40 to 100 °C) and throughout 10,000 cycles of repeated contact-separation. Leveraging these robust performances, the GLCL-TENG excels in all-weather biomechanical energy harvesting and accurate individual motion detection and functions as a self-powered interface for wireless vehicular control. This work presents a viable material design strategy for developing tough and self-healing eutectogel electrodes, emphasizing the potential application of TENGs in all-weather smart vehicles.

Self-healing and hyperelastic magneto-iono-elastomers through molecular confinement of magnetic anions

Magneto-responsiveness in living organisms, exemplified by migratory birds navigating vast distances, offers inspiration for soft robots and human-computer interfaces. However, achieving both high magneto-responsiveness and resilient mechanical properties in synthetic materials has been challenging. Here, we develop magneto-iono-elastomers (MINEs), combining exceptional magnetization [2.6 emu (electromagnetic units)/g] with hyperelasticity and self-healability. Such a MINE consists of a magnetic ionic liquid (MIL; [Emim][FeCl4]) and a urethane group-based polymer that can distinctively confine magnetic anions through strong intermolecular interactions, including potential hydrogen bonds and metal-coordination bonds. This confinement enables high MIL loading (80 wt %) while maintaining structure integrity, resulting in a high ionic conductivity exceeding 10-3 S/cm. Furthermore, the synergistic interplay of these reversible bonds in MINEs contributes to an outstanding elastic recovery that surpasses 99%, alongside good self-healing capabilities. The unique combination of these attributes positions MINE as a promising candidate for diverse magnetoelectronic applications, encompassing wearable strain sensors, contactless magneto-responsive electronics, see-through touch panels, and soft magnetic carriers.

A supramolecular hydrogel leveraging hierarchical multi-strength hydrogen-bonds hinged strategy achieving a striking adhesive-mechanical balance

To obtain high-performance tissue-adhesive hydrogel embodying excellent mechanical integrity, a supramolecular hydrogel patch is fabricated through in situ copolymerization of a liquid-liquid phase separation precursor composed of self-complementary 2-2-ureido-4-pyrimidone-based monomer and acrylic acid coupled with subsequent corporation of bioactive epigallocatechin gallate. Remarkably, the prepared supramolecular hydrogel leverages hierarchical multi-strength hydrogen-bonds hinged strategy assisted by alkyl-based hydrophobic pockets, broadening the distribution of binding strength of physical junctions, striking a canonical balance between superb mechanical performance and robust adhesive capacity. Ultimately, the fabricated supramolecular hydrogel patch stands out as a high stretchability (1500 %), an excellent tensile strength (2.6 MPa), a superhigh toughness (12.6 MJ m-3), an instant and robust tissue adhesion strength (263.2 kPa for porcine skin), the considerable endurance under cyclic loading and reversible adhesion, a superior burst pressure tolerance (108 kPa) to those of commercially-available tissue sealants, and outstanding anti-swelling behavior. The resultant supramolecular hydrogel patch demonstrates the rapid hemorrhage control within 60 s in liver injury and efficient wound closure and healing effects with alleviated inflammation and reduced scarring in full-thickness skin incision, confirming its medical translation as a promising self-rescue tissue-adhesive patch for hemorrhage prevention and sutureless wound closure.

Lignin-reinforced eutectogel with environmentally stability for high-performance human multi-functional sensor

Intrinsic environmental instability of hydrogels has limited their practical applications as durable flexible sensors in human life. In this study, a bio-based eutectogel (BEG) with environmental tolerance was designed via deep eutectic solvent (DES), thioctic acid (TA) and lignin. Benefit from self-ring-opening polymerization of TA monomer in the ethanol and the lignin acting as free radicals, the BEG was fabricated through efficient cast-drying method. The dynamic interaction formation between DES and TA polymer network was revealed by using in-situ infrared spectroscopy during the ethanol evaporation process. The introduction of lignin not only improve the mechanical properties of the eutectogels, but also endow the BEG with moisture tolerance by activating self-aggregated dense hydrophobic layer on the surface while in high humidity environment. This bio-based eutectogels with non-volatility, board range operating temperature and proper self-adhesion could serve as long-term stable temperature-strain dual sensor with high sensitivity (GF = 1.17, TCR = 4.26 %/K) and rapid response behavior (373 ms). Furthermore, the biocompatible BEG was validated for recording human physiological signals over extended period with performance comparable to commercial hydrogel electrodes. This strategy could broaden the range of making durable stretchable eutectogels in human healthcare monitoring.

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.

A robust bio-based polyurethane employed as surgical suture with help to promote skin wound healing

Designing bio-based polyurethane materials with excellent mechanical, biocompatibility, and self-healing properties simultaneously is currently a significant challenge due to the increasing demands for high-performance materials. In this study, we propose an asymmetric backbone strategy utilizing bio-based polycarbonate as the soft segment, equimolar ratios of lysine diisocyanate and isophorone diisocyanate as asymmetric hard segments, and isophorone diamine as the chain extender. The resulting polyurethane elastomers exhibit excellent mechanical properties, including high tensile stress (46.1 MPa), toughness (213.9 MJ/m3), and fracture energy (98.47 kJ/m3). The polyurethane elastomers demonstrate good self-healing and recyclable properties under simple heat treatment. Furthermore, biological experiments confirm the degradability and bio-safety of the bio-based polyurethane elastomers, which have shown potential in accelerating wound healing in mice when used as surgical sutures. These findings highlight the promising prospects of the obtained polyurethane elastomers in various applications, including biomedicine, flexible sensing, and electronic components.

Biogel Library-Accelerated Discovery of All-Natural Bioelectronics

Biogels prepared from natural biopolymers are ideal candidates for constructing bioelectronics from the perspective of commercialization and environmental sustainability. However, discovering all-natural biogels that meet specific properties, such as mechanical properties, optical transparency, and stability, remains challenging. Here, our study introduces a revolutionary biogel library, a novel resource that significantly accelerates the discovery and application of suitable all-natural biogel materials for bioelectronics. Utilizing a high-throughput screening system designed with a frontend/backend development strategy, this biogel library facilitates the swift screening and customization of biogels, tailored to meet specific performance criteria. Along with demonstrating applications in soft bioelectronics and printed bioelectronics, this research also thoroughly investigates the recyclability and environmental impacts of biogels, setting a foundation for their use in sustainable, closed-loop ecological systems. This pioneering approach serves not only to foster the departure from petrochemical-derived polymers but also to bolster the advancement of environmentally responsible bioelectronics.

Synthesis of Novel Zwitterionic Surfactants: Achieving Enhanced Water Resistance and Adhesion in Emulsion Polymer Adhesives

Recent advancements in polymer materials have enabled the synthesis of bio-based monomers from renewable resources, promoting sustainable alternatives to fossil-based materials. This study presents a novel zwitterionic surfactant, SF, derived from 10-undecenoic acid obtained from castor oil through a four-step reaction, achieving a yield of 78%. SF has a critical micelle concentration (CMC) of 1235 mg/L, slightly higher than the commercial anionic surfactant Rhodacal DS-4 (sodium dodecyl benzene sulfonate), and effectively stabilizes monomer droplets, leading to excellent conversion and stable latex formation. The zwitterionic groups in SF enhance adhesion to hydrophilic substrates (glass, stainless steel, and skin). Films produced with SF exhibit outstanding water resistance, with only 18.48% water uptake after 1800 min, compared to 81% for the control using Rhodacal DS-4. Notably, SF maintains low water uptake across various concentrations, minimizing water penetration. Thus, the synthesized SF demonstrates improved adhesive properties and excellent water resistance in emulsion polymerization applications, highlighting its potential as a sustainable, high-performance alternative to petrochemical surfactants.

Anti-polyelectrolyte effect of zwitterions containing (meth)acrylic waterborne polymer chains as tool for colloidal stabilization and polymer reinforcement

The anti-polyelectrolyte effect, a characteristic unique to polymer chains containing zwitterions, was investigated for its impact on colloidal stabilization during emulsion polymerization and on the resulting polymer characteristics. The zwitterionic monomer (ZM) 3-[(3-Acrylamidopropyl)dimethylammonio]propane-1-sulfonate (A3361) was selected for the synthesis of 30 wt% emulsifier-free methyl methacrylate/n-butyl acrylate (MMA/n-BA) polymer latex. Three pH conditions were examined: neutral, where the zwitterionic chains are in a collapsed state, and acidic and basic, where these chains adopt an extended conformation, leading to the anti-polyelectrolyte effect. The study of the anti-polyelectrolyte phenomenon on colloidal stability was challenging due to the increased ionic strength in the dispersions. Nevertheless, films cast from the acidic latex demonstrated enhanced mechanical properties, water resistance, and humidity barrier compared to films produced at neutral pH. This improvement is attributed to the anti-polyelectrolyte phenomenon, where the extended polymer chains rich in zwitterions offer enhanced ionic complexation, resulting in a denser and thicker ionic complexed network within the MMA/n-BA matrix. Under basic pH conditions, these improvements were modest, indicating that the anti-polyelectrolyte mechanism is influenced by pH. Furthermore, the high incorporation of A3361 facilitated, for the first time, the synthesis of 50% solids content emulsifier-free latexes, highlighting practical importance of this technology.

Highly Conducting and Ultra-Stretchable Wearable Ionic Liquid-Free Transducer for Wireless Monitoring of Physical Motions

Wearable strain transducers are poised to transform the field of healthcare owing to the promise of personalized devices capable of real-time collection of human physiological health indicators. For instance, monitoring patients' progress following injury and/or surgery during physiotherapy is crucial but rarely performed outside clinics. Herein, multifunctional liquid-free ionic elastomers are designed through the volume effect and the formation of dynamic hydrogen bond networks between polyvinyl alcohol (PVA) and weak acids (phosphoric acid, phytic acid, formic acid, citric acid). An ultra-stretchable (4600% strain), highly conducting (10 mS cm-1), self-repairable (77% of initial strain), and adhesive ionic elastomer is obtained at high loadings of phytic acid (4:1 weight to PVA). Moreover, the elastomer displayed durable performances, with intact mechanical properties after a year of storage. The elastomer is used as a transducer to monitor human motions in a device comprising an ESP32-based development board. The device detected walking and/or running biomechanics and communicated motion-sensing data (i.e., amplitude, frequency) wirelessly. The reported technology can also be applied to other body parts to monitor recovery after injury and/or surgery and inform practitioners of motion biomechanics remotely and in real time to increase convalescence effectiveness, reduce clinic appointments, and prevent injuries.

Unclonable Encryption-Verification Strategy Based on Bilayer Shape Memory Photonic Crystals

The ability to reversibly exhibit structural color patterns has positioned photonic crystals (PCs) at the forefront of anti-counterfeiting. However, the security offered by the mere reversible display is susceptible to illicit alteration and disclosure. Herein, inspired by the electronic message captcha, bilayer photonic crystal (BPC) systems with integrated decryption and verification modules, are realized by combining inverse opal (IO) and double inverse opal (DIO) with polyacrylate polymers. When the informationized BPC is immersed in ethanol or water, the DIO layer displayed encrypted information due to the solvent-induced ordered rearrangement of polystyrene (PS) microspheres. The verification step is established based on the different structural colors of the IO layer pattern, which result from the deformation or recovery of the macroporous skeleton induced by solvent evaporation. Moreover, through the evaporation-induced random self-assembly of PS@SiO2 and SiO2 microspheres, unclonable structurally colored identifying codes are created in the IO layer, ensuring the uniqueness upon the verification. The decrypted code in the DIO layer is valid only when the IO layer displays the pattern with the predetermined structural color; otherwise, it is a pseudo-code. This structural color-based "decryption-verification" approach offers innovative anti-counterfeiting applications in nanophotonics.

Synergistic Dual-Cross-Linking Gelation: Exploring the Impact of Metal-Ligand Complexation on Ionogel Performance

Owing to the growing interest in wearable ionotronics, the demand for ionogels with outstanding mechanical and electrochemical characteristics has increased dramatically. Nevertheless, it remains challenging to simultaneously enhance the mechanical robustness and conductivity of ionogels because of their trade-off relationship. In this work, we propose physically/chemically dual-cross-linked ionogels designed to improve the mechanical strength without reducing ionic conductivity by introducing metal-ligand complexation only within the physically cross-linked domains. In particular, the impact of metal-ligand complexation, a crucial parameter in this strategy, on ionogel performance is systematically examined using various metal ions. The mechanical resilience and thermal stability of ionogels are effectively enhanced with Co3+ having the highest coordination number, which can be explained by the highest metal-ligand complexation (i.e., chemical cross-linking) density. Additionally, there is no degradation in ionic conductivity when compared to the pristine ionogel because these complexations occur within physically cross-linking domains that are irrelevant to the ion conductive channels. The dual-cross-linked ionogels are successfully applied to alternating-current electroluminescent displays (ACEDs). Moreover, a versatile mixed-emitter strategy is suggested to improve practicality, enabling the realization of frequency-controlled multicolor ACEDs.

From materials to structures: a holistic examination of achieving linearity in flexible pressure sensors

As a pivotal category in the realm of electronics skins, flexible pressure sensors have become a focal point due to their diverse applications such as robotics, aerospace industries, and wearable devices. With the growing demands for measurement accuracy, data reliability, and electrical system compatibility, enhancing sensor's linearity has become increasingly critical. Analysis shows that the nonlinearity of flexible sensors primarily originates from mechanical nonlinearity due to the nolinear deformation of polymers and electrical nonlinearity caused by changes in parameters such as resistance. These nonlinearities can be mitigated through geometric design, material design or combination of both. This work reviews linear design strategies for sensors from the perspectives of structure and materials, covering the following main points: (a) an overview of the fundamental working mechanisms for various sensors; (b) a comprehensive explanation of different linear design strategies and the underlying reasons; (c) a detailed review of existing work employing these strategies and the achieved effects. Additionally, this work delves into diverse applications of linear flexible pressure sensors, spanning robotics, safety, electronic skin, and health monitoring. Finally, existing constraints and future research prospects are outlined to pave the way for the further development of high-performance flexible pressure sensors.

DNA-Intercalating Supramolecular Hydrogels for Tunable Thermal and Viscoelastic Properties

Polymeric supramolecular hydrogels (PSHs) leverage the thermodynamic and kinetic properties of non-covalent interactions between polymer chains to govern their structural characteristics. As these materials are formed via endothermic or exothermic equilibria, their thermal response is challenging to control without drastically changing the nature of the chemistry used to join them. In this study, we introduce a novel class of PSHs utilizing the intercalation of double-stranded DNA (dsDNA) as the primary dynamic non-covalent interaction. The resulting dsDNA intercalating supramolecular hydrogels (DISHs) can be tuned to exhibit both endothermically or exothermically driven binding through strategic selection of intercalators. Bifunctional polyethylene glycol (MW~2000 Da) capped with intercalators of varying hydrophobicity, charge, and size (acridine, psoralen, thiazole orange, and phenanthridine) produced DISHs with comparable moduli (500-1000 Pa), but unique thermal viscoelastic responses. Notably, acridine-based cross-linkers displayed invariant and even increasing relaxation times with temperature, suggesting an endothermic binding mechanism. This methodology expands the set of structure-properties available to biomass-derived DNA biomaterials and promises a new material system where a broad set of thermal and viscoelastic responses can be obtained due to the sheer number and variety of intercalating molecules.

Polyfunctional and Multisensory Bio-Ionoelastomers Enabled by Covalent Adaptive Networks With Hierarchically Dynamic Bonding

Developing versatile ionoelastomers, the alternatives to hydrogels and ionogels, will boost the advancement of high-performance ionotronic devices. However, meeting the requirements of bio-derivation, high toughness, high stretchability, autonomous self-healing ability, high ionic conductivity, reprocessing, and favorable recyclability in a single ionoelastomer remains a challenging endeavor. Herein, a dynamic covalent and supramolecular design, lipoic acid (LA)-based dynamic covalent ionoelastomer (DCIE), is proposed via melt building covalent adaptive networks with hierarchically dynamic bonding (CAN-HDB), wherein lithium bonds aid in the dissociation of ions and the integration of dynamic disulfide metathesis, lithium bonds, and binary hydrogen bonds enhances the mechanical performances, self-healing capability, reprocessing, and recyclability. Therefore, the trade-off among mechanical versatility, ionic conductivity, self-healing capability, reprocessing, and recyclability is successfully handled. The obtained DCIE demonstrates remarkable stretchability (1011.7%), high toughness (3877 kJ m-3), high ionic conductivity (3.94 × 10-4 S m-1), outstanding self-healing capability, reprocessing for 3D printing, and desirable recyclability. Significantly, the selective ion transport endows the DCIE with multisensory feature capable of generating continuous electrical signals for high-quality sensations towards temperature, humidity, and strain. Coupled with the straightforward methodology, abundant availability of LA and HPC, as well as multifunction, the DCIEs present new concept of advanced ionic conductors for developing soft ionotronics.

Making Sticky-Slippery Switchable Fluorogels Through Self-Adaptive Bicontinuous Phase Separation

Developing gel materials with tunable frictional properties is crucial for applications in soft robotics, anti-fouling, and joint protection. However, achieving reversible switching between extreme sticky and slippery states remains a formidable challenge due to the opposing requirements for energy dissipation on gel surfaces. Herein, a self-adaptive bicontinuous fluorogel is introduced that decouples lubrication and adhesion at varying temperatures. The phase-separated fluorogel comprises a soft fluorinated lubricating phase and a stiff yet thermal-responsive load-bearing phase. At ambient temperature, the fluorogel exhibits a highly slippery surface owing to a low-energy-dissipating lubricating layer, demonstrating an ultralow friction coefficient of 0.004. Upon heating, the fluorogel transitions into a highly dissipating state via hydrogen bond dissociation, concurrently releasing adhesive dangling chains to make the surface highly sticky with an adhesion strength of ≈362 kPa. This approach provides a promising foundation for creating advanced adaptive materials with on-demand self-adhesive and self-lubricating capabilities.

A Biodegradable, Stretchable, Healable, and Self-Powered Optoelectronic Synapse Based on Ionic Gelatins for Neuromorphic Vision System

Optoelectronic synapses have gained increasing attentions as a fundamental building block in the development of neuromorphic visual systems. However, it remains a challenge to integrate multiple functions into a single optoelectronic synapse that can be widely applied in wearable artificial intelligence and implantable neuromorphic vision systems. In this study, a stretchable optoelectronic synapse based on biodegradable ionic gelatin heterojunction is successfully developed. This device exhibits self-powered synaptic plasticity behavior with broad spectral response and excellent elastic properties, yet it degrades rapidly upon disposal. After complete cleavage, the device can be fully repaired within 1 min, which is mainly attributed to the non-covalent interactions between different molecular chains. Moreover, the recovery and reprocessing of the ionic gelatins result in optoelectronic properties that are virtually indistinguishable from their original state, showcasing the resilience and durability of ionic gelatins. The combination of biodegradability, stretchability, self-healing, zero-power consumption, ease of large-scale preparation, and low cost makes the work a major step forward in the development of biodegradable and stretchable optoelectronic synapses.

Squid-Inspired Anti-Salt Skin-Like Elastomers With Superhigh Damage Resistance for Aquatic Soft Robots

Cephalopod skins evolve multiple functions in response to environmental adaptation, encompassing nonlinear mechanoreponse, damage tolerance property, and resistance to seawater. Despite tremendous progress in skin-mimicking materials, the integration of these desirable properties into a single material system remains an ongoing challenge. Here, drawing inspiration from the structure of reflectin proteins in cephalopod skins, a long-term anti-salt elastomer with skin-like nonlinear mechanical properties and extraordinary damage resistance properties is presented. Cation-π interaction is incorporated to induce the geometrically confined nanophases of hydrogen bond domains, resulting in elastomers with exceptional true tensile strength (456.5 ± 68.9 MPa) and unprecedently high fracture energy (103.7 ± 45.7 kJ m-2). Furthermore, the cation-π interaction effectively protects the hydrogen bond domains from corrosion by high-concentration saline solution. The utilization of the resultant skin-like elastomer has been demonstrated by aquatic soft robotics capable of grasping sharp objects. The combined advantages render the present elastomer highly promising for salt enviroment applications, particularly in addressing the challenges posed by sweat, in vivo, and harsh oceanic environments.

Low-Hysteresis and Tough Ionogels via Low-Energy-Dissipating Cross-Linking

Low-hysteresis merits can help polymeric gel materials survive from consecutive loading cycles and promote life span in many burgeoning areas. However, it is a big challenge to design low-hysteresis and tough polymeric gel materials, especially for ionogels. This can be attributed to the fact that higher viscosities of ionic liquids (ILs) would increase chain friction of polymeric gels and eventually dissipate large amounts of energy under deformation. Herein, a chemical design of ionogels is proposed to achieve low-hysteresis characteristics in both mechanical and electric aspects via hierarchical aggregates formed by supramolecular self-assembly of quadruple H-bonds in a soft IL-rich polymeric matrix. These self-assembled nanoaggregates not only can greatly reinforce the polymeric matrix and enhance resilience, but also exhibit low-energy-dissipating features under stress conditions, simultaneously benefiting for low-hysteresis properties. These aggregates can also promote toughness and subsequent anti-fatigue properties in response to external cyclic mechanical stimuli. More importantly, these ionogels are presented as a model system to elucidate the underlying mechanism of the low hysteresis and fatigue resistance. Based on these findings, it is further demonstrated that the supramolecular low-hysteresis strategy is universal.

Biomass and Transparent Supramolecular Elastomers for Green Electronics Enabled by the Controlled Growth and Self-Assembly of Dynamic Polymer Networks

Determining the optimal method for preparing supramolecular materials remains a profound challenge. This process requires a combination of renewable raw materials to create supramolecular materials with multiple functions and properties, including simple fabrication, sustainability, a dynamic nature, good toughness, and transparency. In this work, a strategy is presented for toughening supramolecular networks based on solid-phase chain extension. This toughening strategy is simple and environmentally friendly. In addition, a series of biobased elastomers are designed and prepared with adjustable performance characteristics. This strategy can significantly improve the transparency, tensile strength, and toughness of the synthesized elastomer. The synthesized biobased elastomers have great ductility, repairability, and recyclability, and they show good adhesion and dielectric properties. A biobased ionic skin is assembled from these biobased elastomers. Assembled ionic skin can sensitively detect external stimuli (such as stretching, bending, compression, or temperature changes) and monitor human movement. The conductive and dielectric layers of the biobased ionic skin are both obtained from renewable raw materials. This research provides novel molecular design approaches and material selection methods for promoting the development of green electronic devices and biobased elastomers.

Tough and stretchable ionic polyurethane foam for use in wearable devices

Developing tough and conductive materials is crucial for the fields of wearable devices. However, soft materials like polyurethane (PU) are usually non-conductive, whereas conductive materials like carbon nanotubes (CNTs) are usually brittle. Besides, their composites usually face poor interfacial interactions, leading to a decline in performance in practical use. Here, we develop a stretchable PU/CNTs composite foam for use as a strain sensor. A cationic chain extender is incorporated to afford PU cationic groups and to regulate its mechanical properties, whose tensile strength is up to 12.30 MPa and breaking strain exceeds 1000%, and which shows considerable adhesion capability. Furthermore, porous PU foam is prepared via a salt-templating method and carboxylic CNTs with negative groups are loaded to afford the foam conductivity. The obtained foam shows high sensitivity to small strain (GF = 5.2) and exhibits outstanding long-term cycling performance, which is then used for diverse motion detection. The strategy illustrated here should provide new insights into the design of highly efficient PU-based sensors.

Regulating Anode-Electrolyte Interphasial Reactions by Zwitterionic Binder Chemistry in Lithium-Ion Batteries with High-Nickel Layered Oxide Cathodes and Silicon-Graphite Anodes

The practical application of silicon (Si)-based anodes faces challenges due to severe structural and interphasial degradations. These challenges are exacerbated in lithium-ion batteries (LIBs) employing Si-based anodes with high-nickel layered oxide cathodes, as significant transition-metal crossover catalyzes serious parasitic side reactions, leading to faster cell failure. While enhancing the mechanical properties of polymer binders has been acknowledged as an effective means of improving solid-electrolyte interphase (SEI) stability on Si-based anodes, an in-depth understanding of how the binder chemistry influences the SEI is lacking. Herein, a zwitterionic binder with an ability to manipulate the chemical composition and spatial distribution of the SEI layer is designed for Si-based anodes. It is evidenced that the electrically charged microenvironment created by the zwitterionic species alters the solvation environment on the Si-based anode, featuring rich anions and weakened Li+-solvent interactions. Such a binder-regulated solvation environment induces a thin, uniform, robust SEI on Si-based anodes, which is found to be the key to withstanding transition-metal deposition and minimizing their detrimental impact on catalyzing electrolyte decomposition and devitalizing bulk Si. As a result, albeit possessing comparable mechanical properties to those of commercial binders, the zwitterionic binder enables superior cycling performances in high-energy-density LIBs under demanding operating conditions.

Polyelectrolyte-Mediated Modulation of Spatial Internal Stresses of Hydrogels for Complex 3D Actuators

Hydrogel actuators with complex 3D initial shapes show numerous important applications, but it remains challenging to fabricate such actuators. This article describes a polyelectrolyte-based strategy for modulating small-scale internal stresses within hydrogels to construct complex actuators with tailored 3D initial shapes. Introducing polyelectrolytes into precursor solutions significantly enhances the volume shrinkage of hydrogel networks during polymerization, allowing us to modulate internal stresses. Photopolymerization of these polyelectrolyte-containing solutions through a mask produces mechanically strong hydrogel sheets with large patterned internal stresses. Consequently, these hydrogel sheets attain complex 3D initial shapes at equilibrium, in contrast to the planar initial configuration of 2D actuators. We demonstrate that these 3D actuators can reversibly transform into other 3D shapes (i.e., 3D-to-3D shape transformations) in response to external stimuli. Additionally, we develop a predictive model based on the Flory-Rehner theory to analyze the polyelectrolyte-mediated shrinking behaviors of hydrogel networks during polymerization, allowing precise modulation of shrinkage and internal stress. This polyelectrolyte-boosted shrinking mechanism paves a route to the fabrication of high-performance 3D hydrogel actuators.

Highly Transparent, Mechanically Robust, and Conductive Eutectogel Based on Oligoethylene Glycol and Deep Eutectic Solvent for Reliable Human Motions Sensing

Recently, eutectogels have emerged as ideal candidates for flexible wearable strain sensors. However, the development of eutectogels with robust mechanical strength, high stretchability, excellent transparency, and desirable conductivity remains a challenge. Herein, a covalently cross-linked eutectogel was prepared by exploiting the high solubility of oligoethylene glycol in a polymerizable deep eutectic solvent (DES) form of acrylic acid (AA) and choline chloride (ChCl). The resulting eutectogel exhibited high transparency (90%), robust mechanical strength (up to 1.5 MPa), high stretchability (up to 962%), and desirable ionic conductivity (up to 1.22 mS cm-1). The resistive strain sensor fabricated from the eutectogel exhibits desirable linear sensitivity (GF: 1.66), wide response range (1-200%), and reliable stability (over 1000 cycles), enabling accurate monitoring of human motions (fingers, wrists, and footsteps). We believe that our DES-based eutectogel has great potential for applications in wearable strain sensors with high sensitivity and reliability.

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.

Hydrogen Bonding Competition Mediated Phase Separation with Abnormal Moisture-Induced Stiffness Boosting

Moisture usually deteriorates polymers' mechanical performance owing to its plasticizing effect, causing side effects in their practical load-bearing applications. Herein, a simple binary ionogel consisting of an amphiphilic polymer network and a hydrophobic ionic liquid (IL) is developed with remarkable stiffening effect after moisture absorption, demonstrating a complete contrast to water-induced softening effect of most polymer materials. Such a moisture-induced stiffening behavior is induced by phase separation after hydration of this binary ionogel. Specifically, it is revealed that hydrogen (H)-bonding structures play a dominant role in the humidity-responsive behavior of the ionogel, where water will preferentially interact with polymer chains through H-bonding and break the polymer-IL H-bonds, thus leading to phase separation structures with modulus boosting. This work may provide a facile and effective molecular engineering route to construct mechanically adaptive polymers with water-induced dramatic stiffening for diverse applications.

Transforming Commercial Polymers into Tough yet Switchable Adhesives by Trident Photoswitch Molecule Doping: Break Adhesion-Switchability Paradox

Here, a trident molecule doping strategy is introduced to overcome both cohesion-adhesion trade-off and adhesion-switchability conflict, transforming commercial polymers into tough yet photo-switchable adhesives. The strategy involves initial rational design of new trident photoswitch molecules namely TAzo-3 featuring azobenzene and hydroxy-terminated alkyl chains involved rigid-soft tri-branch structure, and subsequent doping into commercial polycaprolactone (PCL) via simple blending. Unique design enables TAzo-3 as a versatile dopant, not only regulating the internal and external supramolecular interaction to balance cohesion and interface adhesion for tough bonding, but also affording marked photothermal effect to facilitate rapid adhesive melting for great photo-switchability. Thus, the optimal TAzo-3-doped PCL (TAzo-3@P) displays markedly-improved bonding performance on diverse substrates compared to linear azobenzene-doped PCL and pure PCL. Impressively, TAzo-3@P on polymethyl methacrylate (PMMA) attains large room-temperature adhesion strength of 6.7 MPa - surpassing most reported adhesives and many commercial adhesives on PMMA, along with easy photo-induced detachment with remarkable switch ratio of 2.09 × 105. Besides, TAzo-3@P can also act as "permanent" adhesives for only adhesion, demonstrating excellent multi-reusability, anti-freezing and waterproof ability. Mechanism studies unveil that the switchable adhesion is closely linked with the dopant molecule structure while rigid-soft coupled trident structures and hydroxy-terminated alkyl chains are key factors.