Deep Eutectic Solvent-Induced Microphase Separation and Entanglement of PVA Chains for Tough and Reprocessable Eutectogels for Sensors

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.

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.

Multifunctional hydrogel based on polyvinyl alcohol/chitosan/metal polyphenols for facilitating acute and infected wound healing

Bacterial-infected wounds could cause delayed wound healing due to increased inflammation, especially wounds infected by drug-resistant bacteria remain a major clinical problem. However, traditional treatment strategies were gradually losing efficacy, such as the abuse of antibiotics leading to enhanced bacterial resistance. Therefore, there was an urgent need to develop an antibiotic-free multifunctional dressing for bacterially infected wound healing. This study demonstrated the preparation of a multifunctional injectable hydrogel and evaluated its efficacy in treating acute and infected wounds. The hydrogel was prepared by a one-step mixing method, and cross-linked by natural deep eutectic solvent (DES), polyvinyl alcohol (PVA), chitosan (CS), tannic acid (TA), and Cu2+ through non-covalent interactions (hydrogen bonds and metal coordination bonds). PVA/CS/DES/CuTA500 hydrogel has multiple functional properties, including injectability, tissue adhesion, biocompatibility, hemostasis, broad-spectrum antibacterial, anti-inflammatory, and angiogenesis. Most importantly, in the MRSA-infected skin wound model, PVA/CS/DES/CuTA500 hydrogel could ultimately accelerate infected wound healing by killing bacteria, activating M2 polarization, inhibiting inflammation, and promoting angiogenesis. In summary, the PVA/CS/DES/CuTA500 hydrogel showed great potential as a wound dressing for bacterial infected wounds treatment in the clinic.

Formation of Self-Healing Granular Eutectogels through Jammed Carbopol Microgels in Supercooled Deep Eutectic Solvent

Typically, gel-like materials consist of a polymer network structure in a solvent. In this work, a gel-like material is developed in a deep eutectic solvent (DES) without the presence of a polymer network, achieved simply by adding microgels. The DES is composed of choline chloride and citric acid and remains stably in a supercooled state at room temperature, exhibiting Newtonian fluid behavior with high viscosity. When the microgel (Carbopol) concentration exceeds 2 wt %, the DES undergoes a transition from a liquid to a soft gel state, characterized as a granular eutectogel. The soft gel characteristics of eutectogels exhibit a yield stress, and their storage moduli exceed the loss moduli. The yield stress and storage moduli are observed to increase with increasing microgel concentration. In contrast, the ion conductivity decreases with increasing microgel concentration but eventually levels off. Because the eutectogel can dissolve completely in excess water, it is a physical gel-like material, attributed to the densely packed structure of microgels in the supercooled DES. Due to the absence of networks, the granular eutectogel has the capability to self-heal simply by being pushed together after being cut into two pieces.

Zwitterionic Eutectogels with High Ionic Conductivity for Environmentally Tolerant and Self-Healing Triboelectric Nanogenerators

Eutectogels have garnered considerable attention for the development of wearable devices, owing to their inherent mechanical elasticity, ionic conductivity, affordability, and environmental compatibility. However, the low conductivity of existing eutectogels has impeded their progression in electronic applications. Here, we report a zwitterionic eutectogel with an impressive ionic conductivity of up to 15.7 mS cm-1. The incorporation of zwitterionic groups into the eutectogel creates ample mobile charges by dissociating the cation and anion of solvents, thereby yielding exceptional ionic conductivity. Moreover, the abundant electrostatic and hydrogen bonding interactions within the eutectogel endow it with prominent self-healing and adhesive properties. By integrating the eutectogel with a roughly patterned polydimethylsiloxane film, we have successfully constructed a triboelectric nanogenerator (TENG) with a maximum output power density of 112 mW m-2. This TENG is capable of generating stable electrical signals even in extreme temperature conditions ranging from -80 to 100 °C and effectively powering electronic devices. Furthermore, the assembled TENG displays high sensitivity as a self-powered sensor, enabling real-time and precise monitoring of signals derived from human motions. This study establishes a promising approach for the development of sustainable and multifunctional flexible electronics that are resilient in extreme environments.

A Strong and Highly Transparent Ionogel Electrolyte Enabled by In Situ Polymerization-Induced Microphase Separation for High-Performance Electrochromic Devices

Electrochromic devices built with ionogel electrolytes are seen as a pivotal step toward the future of quasi-solid electrochromic devices, due to their striking properties like exceptional safety and high ionic conductivity. Yet, the poor mechanical strength of electrolyte of these devices remains a constraint that hampers their advancement. As a resolution, this research explores the use of a robust, transparent ionogel electrolyte, which is designed using an in situ microphase separation strategy. The ionogels are highly transparent and robust and exhibit excellent physicochemical stability, including a wide electrochemical window and high temperature tolerance. Benefitting from these properties, a high-performance electrochromic device is fabricated through in situ polymerization with the ionogels, PPRODOT as the electrochromic layer, and PEDOT: PSS as the ion storage layer, achieving high transmittance contrast (43.1%), fast response (1/1.7 s), high coloring efficiency (1296.4 cm2 C-1), and excellent cycling endurance (>99.9% retention after 2000 cycles). In addition, using ITO-poly(ethylene terephthalate) as flexible substrates, a deformable electrochromic device displaying high stability is realized, highlighting the potential use in functional wearables.

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

Gel materials are appealing due to their diverse applications in biomedicine, soft electronics, sensors, and actuators. Nevertheless, the existing synthetic gels are often plagued by feeble network structures and inherent defects associated with solvents, which compromise their mechanical load-bearing capacity and cast persistent doubts about their reliability. Herein, combined with attractive deep eutectic solvent (DES), a stepwise-enhanced strategy is presented to fabricate ultrarobust eutectogels. It focuses on the continuous modulation and optimization of polymer networks through complementary annealing and solvent exchange processes, which drives a progressive increase in both quantity and mass of the interconnected polymer chains at microscopic scale, hence contributing to the evolutionary enhancement of network structure. The resultant eutectogel exhibits superb mechanical properties, including record-breaking strength (31.8 MPa), toughness (76.0 MJ m-3 ), and Young's modulus (25.6 MPa), together with exceptional resistance ability to tear and crack propagation. Moreover, this eutectogel is able to be further programmed through photolithography to in situ create patterned eutectogel for imparting specific functionalities. Enhanced by its broad applicability to various DES combinations, this stepwise-enhanced strategy is poised to serve as a crucial template and methodology for the future development of robust gels.

Hydrophobic deep eutectic solvent-based eutectogels for underwater sensing

Eutectogels derived from deep eutectic solvents (DESs) exhibit great potential for the fabrication of flexible sensors. However, the hygroscopicity of eutectogels hinders their applications in underwater sensing. In this work, a hydrophobic eutectogel with exceptional long-term underwater stability is produced through one-step polymerization of lauryl methacrylate and glycidyl methacrylate in a hydrophobic DES. The hydrophobic gel network and hydrophobic DES fulfill the eutectogel with outstanding water resistance (water contact angle > 110°) and excellent mechanical properties in an aqueous environment, thus leading to extraordinary durability (over 1000 testing cycles). Additionally, based on this eutectogel, underwater strain and pressure sensors with high sensitivity, rapid responsiveness, and superior durability were fabricated for accurate real-time monitoring of human activity. Furthermore, it has been demonstrated that the eutectogel sensor can transmit information through Morse code, performing as a wearable underwater communicator. This research provides an exemplary way for a demonstration method of hydrophobic eutectogel for durable underwater applications.

Facile Solvent Regulation for Highly Strong and Tough Physical Eutectogels with Remarkable Strain Sensitivity

Physical eutectogels have great potential for applications in many fields due to their electrical conductivity, broad temperature stability, and biocompatibility. However, the preparation of high-performance physical eutectogels in a simple, efficient, and cost-effective way remains a challenge. In this study, a facile but efficient solvent regulation strategy was proposed to construct a highly robust poly(vinyl alcohol) (PVA) physical eutectogel. Hydrogen bonds within the polymer-containing deep eutectic solvent system were dynamically regulated by the introduction-removal of water to induce the formation of a uniform and dense polymer cross-linked network, which imparted excellent mechanical properties to the resulting eutectogel. For the eutectogel with 15 wt % PVA, the tensile strength and toughness were 1.67 MPa and 6.81 MJ m-3, respectively, which were at a high level among existing physical eutectogels. This high-performance eutectogel was available as a strain sensor and exhibited high sensitivity. In addition, this eutectogel can be endowed with a directional muscle-like stretching performance through convenient mechanical training. The easy scalability and low cost made our method an effective strategy for developing high-performance physical eutectogels, which would further promote the application of such materials in areas such as wearable electronics and soft robotics.

In Situ Formation of Conductive Epidermal Electrodes Using a Fully Integrated Flexible System and Injectable Photocurable Ink

In situ fabrication of wearable devices through coating approaches is a promising solution for the fast deployment of wearable devices and more adaptable devices for different sensing demands. However, heat, solvent, and mechanical sensitivity of biological tissues, along with personal compliance, pose strict requirements for coating materials and methods. To address this, a biocompatible and biodegradable light-curable conductive ink and an all-in-one flexible system that conducts in situ injection and photonic curing of the ink as well as monitoring of biophysiological information have been developed. The ink can be solidified through spontaneous phase changes and photonic cured to achieve a high mechanical strength of 7.48 MPa and an excellent electrical conductivity of 3.57 × 10⁵ S/m. The flexible system contains elastic injection chambers embedded with specially designed optical waveguides to uniformly dissipate visible LED light throughout the chambers and rapidly cure the ink in 5 min. The resulting conductive electrodes offer intimate skin contact even with the existence of hair and work stably even under an acceleration of 8 g, leading to a robust wearable system capable of working under intense motion, heavy sweating, and varied surface morphology. Similar concepts may lead to various rapidly deployable wearable systems that offer excellent adaptability to different monitoring demands for the health tracking of large populations.