Evolutionary Reinforcement of Polymer Networks: A Stepwise-Enhanced Strategy for Ultrarobust Eutectogels

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.

Copper-Coordination Engineered Glassy Hydrogels Featuring Ultrastiffness and Structural Programmability

Glassy hydrogels, which maintain a distinctive glassy state at ambient temperature, are appealing for engineering applications. Nevertheless, the existing glassy hydrogels often suffer from inferior strength, inadequate stiffness, and environmental stability caused by weak physical cross-linking. Herein, we present an ultrastiff and ultrastrong glassy hydrogel by introducing robust coordination bonds into a network composed of polyacrylic acid (PAA) and polyvinyl alcohol (PVA), using a copper acetate-assisted strategy. The presence of acetate anions creates a relatively alkaline environment, which deprotonates the carboxyl groups of PAA. This deprotonation exposes carboxylate groups that readily coordinate with copper ions, establishing a densely cross-linked network in the glassy state. The resultant glassy hydrogel exhibits record-breaking Young's modulus (469.7 MPa), tensile strength (19.2 MPa), and exceptional environmental stability. Moreover, the reversible softening and vitrification induced by the breakage and reforming of coordination bonds endows glassy hydrogel with structural programmability, allowing for the construction of integrated auxetic hydrogel (IAH). The IAH demonstrates enhanced mechanical properties compared to the auxetic skeleton alone while maintaining a negative Poisson's ratio over a wide strain range of 0-29%. This study provides a promising engineering route for the development of advanced glassy hydrogels.

High Strength, Strain, and Resilience of Gold Nanoparticle Reinforced Eutectogels for Multifunctional Sensors

Eutectogels with inherent ionic conductivity, mechanical flexibility, environment resistance, and cost-effectiveness have garnered considerable attention for the development of wearable devices. However, existing eutectogels rarely achieve a balance between strength, strain, and resilience, which are critical indicators of reliability in flexible electronics. Herein, poly(sodium styrenesulfonate) (PSS)-modified gold nanoparticles (AuNPs) in eutectic solvents are synthesized, and PSS-AuNP reinforced polyacrylic acid/polyvinylpyrrolidone (SAu-PAA/PVP) eutectogel is successfully prepared. Through the coordination between AuNPs and the PAA/PVP polymer chains, the SAu-PAA/PVP eutectogel exhibits significantly enhanced tensile strain (946%), mechanical strength (3.50 MPa), and resilience (85.3%). The high-performance eutectogel was demonstrated as a flexible sensor sensitive to strain and temperature, and the AuNPs provided near-infrared sensing capabilities. Furthermore, SAu-PAA/PVP eutectogel inherits the benefits of ES, including anti-drying and anti-freezing properties (-77 °C). Moreover, the eutectogel is microstructured using a simple molding method, and the resulting hierarchical pyramid microstructured eutectogel functions as ionic dielectric layer in a pressure sensor. This sensor exhibits high sensitivity (37.11 kPa-1), low detection limit (1 Pa), a fast response rate (36/54 ms), and excellent reproducibility over 5000 cycles, making them reliable and durable for detecting small vibrations, with potential applications in precision machinery, aerospace, and buildings.

Puncture-resistant hydrogels with high mechanical performance achieved supersaturated salt

Sufficient mechanical performance is the basic requirement for load-bearing and damage-resistant materials. However, the simultaneous optimization of mechanical properties is usually difficult in a single hydrogel. Herein, a supersaturated salt was employed to enhance the mechanical performance and damage resistance of hydrogels. By immersing the pre-formed hydrogel based on hydrophobic associations into supersaturated Na2SO4 solution (3.3 M), high-density and strong hydrophobic associations were constructed simultaneously in the network due to the contraction of hydrophilic chains and improvement of hydrophobic associations. Compared to the pristine hydrogel, this salt-treated hydrogel was transparent and showed a simultaneous enhancement in stiffness (E of 253 ± 7 MPa), strength (σ of 12.65 ± 0.07 MPa), and toughness (Γ of 19.6 ± 3.2 MJ m-3). It also displayed remarkable puncture and tear resistance with a puncture force of 66 N, a puncture energy of 370 mJ, and a tearing energy of 34 kJ m-2. This work provides a simple method to simultaneously optimize the contradictory mechanical properties and puncture resistance in a single hydrogel.

Accelerated Hydrogel Strengthening: Synergy between Mechanical Training and Lignin Intake

The construction of high-strength hydrogels is essential for engineering applications but is often limited by poor durability under stress. Current post-treatment methods are inefficient and time consuming. Inspired by muscle building, we propose a green, efficient, and synergistic enhancement method. The dynamic stretching of the PVA hydrogel in LS solution promotes the formation of an ordered polymer network, while LS can fix the ordered structure. After 500 stretching cycles (approximately 16.7 min), the tensile strength, toughness, and Young's modulus increase by 76-fold, 117-fold, and 304-fold, respectively, outperforming single treatments such as soaking or training. Multitechnique analyses reveal that nanoscale crystalline domains and microscale-ordered polymers drive these macroscopic improvements. Notably, the LS solution can be substituted with other solvents to achieve similar effects, demonstrating excellent adaptability, scalability, and efficiency. This rapid and straightforward synergistic enhancement technology holds great promise for overcoming the challenges of constructing and applying high-strength hydrogels.

Ultrastrong eutectogels engineered via integrated mechanical training in molecular and structural engineering

Ultrastrong gels possess generally ultrahigh modulus and strength yet exhibit limited stretchability owing to hardening and embrittlement accompanied by reinforcement. This dilemma is overcome here by using hyperhysteresis-mediated mechanical training that hyperhysteresis allows structural retardation to prevent the structural recovery of network after training, resulting in simply single pre-stretching training. This training strategy introduces deep eutectic solvent into polyvinyl alcohol hydrogels to achieve hyperhysteresis via hydrogen bonding nanocrystals on molecular engineering, performs single pre-stretching training to produce hierarchical nanofibrils on structural engineering, and fabricates chemically cross-linked second network to enable stretchability. The resultant eutectogels display exceptional mechanical performances with enormous fracture strength (85.2 MPa), Young's modulus (98 MPa) and work of rupture (130.6 MJ m-3), which compare favorably to those of previous gels. The presented strategy is generalizable to other solvents and polymer for engineering ultrastrong organogels, and further inspires advanced fabrication technologies for force-induced self-reinforcement materials.

Fatigue-resistant and super-tough thermocells

Wearable thermocells offer a sustainable energy solution for wearable electronics but are hindered by poor fatigue resistance, low fracture energy, and thermal inefficiencies. In this study, we present a high-strength, fatigue-resistant thermocell with enhanced thermoelectric performance through solvent exchange-assisted annealing and chaotropic effect-enhanced thermoelectric properties. The mechanical strength and toughness are improved by forming macromolecular crystal domains and entangling polymer chains. Guanidine ions, with strong chaotropic properties, optimize the solvation layer of redox ion couple, boosting thermoelectric efficiency. Compared to existing anti-fatigue thermocells, the current design exhibits a 20-fold increase in mechanical toughness (368 kJ m-2) and a 3-fold increase in Seebeck coefficient (5.4 mV K-1). With an ultimate tensile strength of 12 MPa, a fatigue threshold of 4.1 kJ m-2, and a specific output power density of 714 μW m-2 K-2, this thermocell outperforms existing designs, enabling more reliable and efficient wearable electronics and stretchable devices.

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.

Ultra-Tough Dynamic Supramolecular Ion-Conducting Elastomer Induced Uniform Li+ Transport and Stabilizes Interphase Ensures Dendrite-Free Lithium Metal Anodes

Artificial polymer solid electrolyte interphases (SEIs) with microphase-separated structures provide promising solutions to the inhomogeneity and cracking issues of natural SEIs in lithium metal batteries (LMBs). However, achieving homogeneous ionic conductivity, excellent mechanical properties, and superior interfacial stability remains challenging due to interference from hard-phase domains in ion transport and solid-solid interface issues with lithium metal. Herein, we present a dynamic supramolecular ion-conducting poly (urethane-urea) interphase (DSIPI) that achieves these three properties through modulating the hard-phase domains and constructing a composite SEI in situ. The soft-phase polytetrahydrofuran backbone, featuring loose Li+-O coordinating interactions, ensures uniform Li+ transport. Concurrently, sextuple hydrogen bonds in the hard phase dissipate strain energy through sequential bond cleavage, thereby imparting exceptional mechanical properties. Moreover, enriched bis (trifluoromethanesulfonyl) imide anion (TFSI-) in DSIPI promotes the in situ formation of a stable polymer-inorganic composite SEI during cycling. Consequently, the DSIPI-protected lithium anode (DSIPI@Li) enables symmetric cells with exceptional cyclability exceeding 4,000 hours at an ultra-high current density of 20 mA cm-2, thereby demonstrating excellent cycling stability. Furthermore, DSIPI@Li facilitates stable operation of the pouch cells under the constraints of a high-loading LiNi0.8Co0.1Mn0.1O2 cathode and low negative/positive capacity (N/P) ratio. This work presents a powerful strategy for designing artificial SEIs and high-performance LMBs.

Coordinatively stiffen and toughen polymeric gels via the synergy of crystal-domain cross-linking and chelation cross-linking

Polymer gels have been widely used in flexible electronics, soft machines and impact protection materials. Conventional gels usually suffer from the inherent conflict between stiffness and toughness, severely hampering their applications. This work proposes a facile yet versatile strategy to break through this trade-off via the synergistic effect of crystal-domain cross-linking and chelation cross-linking, without the need for specific structure design or adding other reinforcements. Both effects are proven to boost the mechanical performance of the originally weak gel, and result in a stiff and tough conductive gel, achieving significant enhancements in elastic modulus and toughness by up to 366-, and 104-folds, respectively. The resultant gel achieves coordinatively enhanced stiffness (110.26 MPa) and toughness (219.93 MJ m-3), reconciling the challenging trade-off between them. In addition, the presented strategy is found generalizable to a variety of metal ions and polymers, offering a promising way to expand the applicability of gels.

Extreme Toughening of Conductive Hydrogels Through Synergistic Effects of Mineralization, Salting-Out, and Ion Coordination Induced by Multivalent Anions

Developing conductive hydrogels with both high strength and fracture toughness for diverse applications remains a significant challenge. In this work, an efficient toughening strategy is presented that exploits the multiple enhancement effects of anions through a synergistic combination of mineralization, salting-out, and ion coordination. The approach centers on a hydrogel system comprising two polymers and a cation that is highly responsive to anions. Specifically, polyvinyl alcohol (PVA) and chitosan quaternary ammonium (HACC) are used, as PVA benefits from salting-out effects and HACC undergoes ion coordination with multivalent anions. After just 1 h of immersion in an anionic solution, the hydrogel undergoes a dramatic improvement in mechanical properties, increasing by more than three orders of magnitude. The optimized hydrogel achieves high strength (26 MPa), a high Young's modulus (45 MPa), and remarkable fracture toughness (67.3 kJ m-2), representing enhancements of 860, 3200, and 1200 times, respectively, compared to its initial state. This breakthrough overcomes the typical trade-off between stiffness and toughness. Additionally, the ionic conductivity of the hydrogel enables reliable strain sensing and supports the development of durable supercapacitors. This work presents a simple and effective pathway for developing hydrogels with exceptional strength, toughness, and conductivity.

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.

Multi-Modal Sensing Ionogels with Tunable Mechanical Properties and Environmental Stability for Aquatic and Atmospheric Environments

Ionogels have garnered significant interest due to their great potential in flexible iontronic devices. However, their limited mechanical tunability and environmental intolerance have posed significant challenges for their integration into next-generation flexible electronics in different scenarios. Herein, the synergistic effect of cation-oxygen coordination interaction and hydrogen bonding is leveraged to construct a 3D supramolecular network, resulting in ionogels with tunable modulus, stretchability, and strength, achieving an unprecedented elongation at break of 10 800%. Moreover, the supramolecular network endows the ionogels with extremely high fracture energy, crack insensitivity, and high elasticity. Meanwhile, the high environmental stability and hydrophobic network of the ionogels further shield them from the unfavorable effects of temperature variations and water molecules, enabling them to operate within a broad temperature range and exhibit robust underwater adhesion. Then, the ionogel is assembled into a wearable sensor, demonstrating its great potential in flexible sensing (temperature, pressure, and strain) and underwater signal transmission. This work can inspire the applications of ionogels in multifunctional sensing and wearable fields.

Applications of Functional Polymeric Eutectogels

Over the past two decades, deep eutectic solvents (DESs) have captured significant attention as an emergent class of solvents that have unique properties and applications in differing fields of chemistry. One area where DES systems find utility is the design of polymeric gels, often referred to as "eutectogels," which can be prepared either using a DES to replace a traditional solvent, or where monomers form part of the DES themselves. Due to the extensive network of intramolecular interactions (e.g., hydrogen bonding) and ionic species that exist in DES systems, polymeric eutectogels often possess appealing material properties-high adhesive strength, tuneable viscosity, rapid polymerization kinetics, good conductivity, as well as high strength and flexibility. In addition, non-covalent crosslinking approaches are possible due to the inherent interactions that exist in these materials. This review considers several key applications of polymeric eutectogels, including organic electronics, wearable sensor technologies, 3D printing resins, adhesives, and a range of various biomedical applications. The design, synthesis, and properties of these eutectogels are discussed, in addition to the advantages of this synthetic approach in comparison to traditional gel design. Perspectives on the future directions of this field are also highlighted.

Regulating natural galactomannan into composite hydrogels for improved adhesion, anti-swelling capability and efficient dye pollution removal

Constructing bio-based composite hydrogel materials are receiving much interest, while regulating the interactions of the hydrogel components and integrating functions for multi-application meet various challenges. Herein, composite hydrogels were prepared by cross-linking of poly-acrylamide (PAM) and poly-N-[3-(Dimethylamino) propyl] acrylamide (PDMAPAA), assisted by natural galactomannan (GM) regulation. Even distribution and compatibility of GM in the three-dimensional materials were proved by a series of chemical and morphological characterizations, which favored the improvement of mechanical properties (~80 kPa) and flexibility. Besides, the hydrogels were well-connected with double networks of noncovalent intermolecular hydrogen bonding interactions and hydrophobic interactions, in addition to covalent-linked polymers. Due to great amount of inner hydrogen bond linkages, the hydrogels present satisfying anti-swelling capabilities (<15 %), exhibiting high potential for application in water treatment. Meanwhile, abundant surface functional groups provided possibilities to form interactive layer with the various substrates surface, exhibiting highly adhesive properties. Significant dyes adsorption capabilities were revealed on the hydrogels according to the electrostatic attraction with Congo red and hydrogen bond interactions with Brilliant green respectively. Thus, the proposed composite hydrogels integrated multi-functions due to the tuning the surface groups and cross-linking interactions, which provided deeper understanding on bio-based materials on fields of water treatment and environmental protection.

Supercooling-Driven Homogenization and Strengthening of Hydrogel Networks

By leveraging principles from metal grain refinement, we introduce a transformative technique for fabricating poly(vinyl alcohol) (PVA) hydrogels via supercooling-coupled wet annealing, significantly enhancing their mechanical robustness and isotropy while maintaining their exceptionally high water content. Our methodology involves the dissolving PVA in water at elevated temperatures, mirroring the homogeneity achieved with a molten metal, in order to ensure a uniform distribution of polymer chains. This uniformity facilitates a rapid cooling phase that generates ultrafine ice crystals, setting the stage for a crucial solvent exchange with ethylene glycol (EG). The EG-mediated supercooling technique ensures the polymer homogeneity and structure integrity and induces the PVA chains to aggregate and form high-density hydrogen bonds, leading to a uniformly distributed, interconnected PVA network with high crystallinity. The process is further strengthened by EG-enabled wet annealing, which promotes the formation of densely packed crystalline domains within the polymer network. This rigorous process yields PVA hydrogels with superior mechanical properties, including a tensile strength of 13.65 MPa and a fracture toughness of 35.39 MJ m-3, alongside remarkable water content nearing 80%. These advances not only surpass the capabilities of conventional hydrogels but also broaden their application potential, highlighting the innovative integration of supercooling principles in polymer science.

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.

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.

Sprayable oxidized polyvinyl alcohol with improved degradability and sufficient mechanical property for fruit preservation

Besides their limited preservation capacity and low biosafety, traditional fruit preservation procedures exacerbate "white pollution" because they utilize excessive plastic. Herein, an environmentally friendly one-pot method was developed to obtain degradable polyvinyl alcohol (PVA), where the hydroxyl radicals generated through the reaction between hydrogen peroxide (H2O2) and iron ions functioned to oxidize PVA. The oxidized PVA (OPVA-1.0) with abundant ketone groups, reduced crystallinity, and short molecular chains was completely degraded into H2O and CO2 after being buried in the soil for ∼60 days. An improvement in its degradation rate did not weaken the mechanical properties of OPVA-1.0 compared to other modified PVA films because the adverse effect of decreased crystallinity on its mechanical performance was offset by its ion coordination. Alternatively, the tensile strength or toughness of OPVA-1.0 was enhanced due to its internal multi-level interactions including molecular chain entanglement, hydrogen bonding, and metal coordination bonds. More interestingly, OPVA-1.0 was water-welded into various products in a recyclable way owing to its reversible physical bonds, where it was sprayed, dipped, or brushed conformally onto different perishable fruits to delay their ripening by 5-14 days. Based on the cellular biocompatibility and biosafety evaluations in mice, OPVA-1.0 obtained by the facile oxidation strategy was demonstrated to alleviate "white pollution" and delay the ripening of fruits effectively.

Nanolignin-Facilitated Robust Hydrogels

Recently, certain challenges and accompanying drawbacks have emerged in the preparation of high-strength and tough polymer hydrogels. Insights from wood science highlight the role of the intertwined molecular structure of lignin and crystalline cellulose in contributing to wood's strength. Herein, we immersed prestretched poly(vinyl alcohol) (PVA) polymer hydrogels into a solution of nanosized lignosulfonate sodium (LS), a water-soluble anionic polyelectrolyte, to creatively reconstruct this similar structure at the molecular scale in hydrogels. The nanosized LS effectively fixed and bundled the prestretched PVA polymers while inducing the formation of dense crystalline domains within the polymer matrix. Consequently, the interwoven structure of crystalline PVA and LS conferred good strength to the composite hydrogels, exhibiting a tensile strength of up to ∼23 MPa, a fracture strain of ∼350%, Young's modulus of ∼17 MPa, toughness of ∼47 MJ/m3, and fracture energy of ∼42 kJ/m2. This hydrogel far outperformed previous hydrogels composed directly of lignin and PVA (tensile strength <1.5 MPa). Additionally, the composite hydrogels demonstrated excellent antifreezing properties (<-80 °C). Notably, the LS-assisted reconstruction technology offers opportunities for the secondary fixation of PVA hydrogel shapes and high-strength welding of hydrogel components. This work introduces an approach for the high-value utilization of LS, a green byproduct of pulp production. LS's profound biomimetic strategy will be applied in multifunctional hydrogel fields.

Tough Supramolecular Hydrogels Crafted via Lignin-Induced Self-Assembly

Supramolecular hydrogels are typically assembled through weak non-covalent interactions, posing a significant challenge in achieving ultra strength. Developing a higher strength based on molecular/nanoscale engineering concepts is a potential improvement strategy. Herein, a super-tough supramolecular hydrogel is assembled by gradually diffusing lignosulfonate sodium (LS) into a polyvinyl alcohol (PVA) solution. Both simulations and analytical results indicate that the assembly and subsequent enhancement of the crosslinked network are primarily attributed to LS-induced formation and gradual densification of strong crystalline domains within the hydrogel. The optimized hydrogel exhibits impressive mechanical properties with tensile strength of ≈20 MPa, Young's modulus of ≈14 MPa, and toughness of ≈50 MJ m⁻3, making it the strongest lignin-PVA/polymer hydrogel known so far. Moreover, LS provides the supramolecular hydrogel with excellent low-temperature stability (<-60 °C), antibacterial, and UV-blocking capability (≈100%). Interestingly, the diffusion ability of LS is demonstrated for self-restructuring damaged supramolecular hydrogel, achieving 3D patterning on hydrogel surfaces, and enhancing the local strength of the freeze-thaw PVA hydrogel. The goal is to foster a versatile hydrogel platform by combining eco-friendly LS with biocompatible PVA, paving the way for innovation and interdisciplinarity in biomedicine, engineering materials, and forestry science.

A flexible, stretchable and wearable strain sensor based on physical eutectogels for deep learning-assisted motion identification

Physical eutectogels as a newly emerging type of conductive gel have gained extensive interest for the next generation multifunctional electronic devices. Nevertheless, some obstacles, including weak mechanical performance, low self-adhesive strength, lack of self-healing capacity, and low conductivity, hinder their practical use in wearable strain sensors. Herein, lignin as a green filler and a multifunctional hydrogen bond donor was directly dissolved in a deep eutectic solvent (DES) composed of acrylic acid (AA) and choline chloride, and lignin-reinforced physical eutectogels (DESL) were obtained by the polymerization of AA. Due to the unique features of lignin and DES, the prepared DESL eutectogels exhibit good transparency, UV shielding capacity, excellent mechanical performance, outstanding self-adhesiveness, superior self-healing properties, and high conductivity. Based on the aforementioned integrated functions, a wearable strain sensor displaying a wide working range (0-1500%), high sensitivity (GF = 18.15), rapid responsiveness, and excellent stability and durability (1000 cycles) and capable of detecting diverse human motions was fabricated. Additionally, by combining DESL sensors with a deep learning technique, a gesture recognition system with accuracy as high as 98.8% was achieved. Overall, this work provides an innovative idea for constructing multifunction-integrated physical eutectogels for application in wearable electronics.

Dynamically Cross-Linked Double-Network Hydrogels with Matched Mechanical Properties and Ideal Biocompatibility for Artificial Blood Vessels

Vessel transplantation is currently considered the "gold standard" treatment for cardiovascular disease. However, ideal artificial vascular grafts should possess good biocompatibility and mechanical strength that match those of native autologous vascular tissue to promote in vivo tissue regeneration. In this study, a series of dynamic cross-linking double-network hydrogels and the resultant hydrogel tubes were prepared. The hydrogels (named PCO), composed of rigid poly(vinyl alcohol) (PVA), flexible carboxymethyl chitosan (CMCS), and a cross-linker of aldehyde-based β-cyclodextrin (OCD), were formed in a double-network structure with multiple dynamical cross-linking including dynamic imine bonds, hydrogen bonds, and microcrystalline regions. The PCO hydrogels exhibited superior mechanical strength, good network stability, and fatigue resistance. Additionally, it demonstrated excellent cell and blood compatibility. The results showed that the introduction of CMCS/OCD led to a significant increase in the proliferation rate of endothelial cells seeded on the surface of the hydrogel. The hemolysis rate in the test was lower than 0.3%, and both protein adsorption and platelet adhesion were reduced, indicating an excellent anticoagulant function. The plasma recalcification time test results showed that endogenous coagulation was alleviated to some extent. When formed into blood vessels and incubated with blood, no thrombus formation was observed, and there was minimal red blood cell aggregation. Therefore, this novel hydrogel tube, with excellent mechanical properties, exhibits antiadhesive characteristics toward blood cells and proteins, as well as antithrombotic properties, making it hold tremendous potential for applications in the biomedical and engineering fields.

Interface-Compatible Gel-Polymer Electrolyte Enabled by NaF-Solubility-Regulation toward All-Climate Solid-State Sodium Batteries

Gel-polymer electrolyte (GPE) is a pragmatic choice for high-safety sodium batteries but still plagued by interfacial compatibility with both cathode and anode simultaneously. Here, salt-in-polymer fibers with NaF salt inlaid in polylactide (PLA) fiber network was fabricated via electrospinning and subsequent in situ forming gel-polymer electrolyte in liquid electrolytes. The obtained PLA-NaF GPE achieves a high ion conductivity (2.50×10-3 S cm-1) and large Na+ transference number (0.75) at ambient temperature. Notably, the dissolution of NaF salt occupies solvents leading to concentrated-electrolyte environment, which facilitates aggregates with increased anionic coordination (anion/Na+ >1). Aggregates with higher HOMO realize the preferential oxidation on the cathode so that inorganic-rich and stable CEI covers cathode' surface, preventing particles' breakage and showing good compatibility with different cathodes (Na3V2(PO4)3, Na2+2xFe2-x(SO4)3, Na0.72Ni0.32Mn0.68O2, NaTi2(PO4)3). While, passivated Na anode induced by the lower LUMO of aggregates, and the lower surface tension between Na anode and PLA-NaF GPE interface, leading to the dendrites-free Na anode. As a result, the assembled Na || Na3V2(PO4)3 cells display excellent electrochemical performance at all-climate conditions.

High Strength and Toughness Polymeric Triboelectric Materials Enabled by Dense Crystal-Domain Cross-Linking

Lightweight, easily processed, and durable polymeric materials play a crucial role in wearable sensor devices. However, achieving simultaneously high strength and toughness remains a challenge. This study addresses this by utilizing an ion-specific effect to control crystalline domains, enabling the fabrication of a polymeric triboelectric material with tunable mechanical properties. The dense crystal-domain cross-linking enhances energy dissipation, resulting in a material boasting both high tensile strength (58.0 MPa) and toughness (198.8 MJ m-3), alongside a remarkable 416.7% fracture elongation and 545.0 MPa modulus. Leveraging these properties, the material is successfully integrated into wearable self-powered devices, enabling real-time feedback on human joint movement. This work presents a valuable strategy for overcoming the strength-toughness trade-off in polymeric materials, paving the way for their enhanced applicability and broader use in diverse sensing applications.