Deep Eutectic Solvents-based Ionogels with Ultrafast Gelation and High Adhesion in Harsh Environments

Hydrogel adhesives for tissue recovery

Hydrogel adhesives (HAs) are promising and rewarding tools for improving tissue therapy management. Such HAs had excellent properties and potential applications in biological tissues, such as suture replacement, long-term administration, and hemostatic sealing. In this review, the common designs and the latest progress of HAs based on various methodologies are systematically concluded. Thereafter, how to deal with interfacial water to form a robust wet adhesion and how to balance the adhesion and non-adhesion are underlined. This review also provides a brief description of gelation strategies and raw materials. Finally, the potentials of wound healing, hemostatic sealing, controlled drug delivery, and the current applications in dermal, dental, ocular, cardiac, stomach, and bone tissues are discussed. The comprehensive insight in this review will inspire more novel and practical HAs in the future.

Lignin-induced eutectogel electrolytes enabling wide-temperature tolerance and high energy density zinc-ion hybrid supercapacitors

Zinc-ion hybrid supercapacitors (ZHS) have demonstrated tremendous potential in the field of energy storage for wearable electronics, as they combine the higher energy density of zinc-ion batteries with the superior power density of supercapacitors. However, conventional solid electrolytes with low conductivity, extreme environments intolerance, safety risks, and a time- and energy-consuming preparation process, which hinders the applications of ZHS. Herein, a self-catalytic system (SLSFe3+) basing on sulfonated lignin (SLS) was used to rapidly (∼60 s) fabricate polyacrylamide-SLS hydrogels (PLH). Zinc perchlorate (Zn(ClO4)2) was used as hydrogen bond acceptor, ethylene glycol (EG) as hydrogen bond donor, and water as diluent to lower viscosity to create a metal salt-based ternary hydrated eutectic solvent (DES). PLH were immersed in the DES to obtain eutectogels. The prepared eutectogels displayed enhancing properties of mechanical strength (∼2160 % elongation), ionic conductivity (45.3 mS cm-1), antifreeze/non-drying and flame-retardant (a LOI value of 47.3). The ZHS assembled with the eutectogel electrolyte exhibited a high energy density of 216.94 Wh kg-1 at a high-power density of 712 W kg-1. Meanwhile, the ZHS had long cycle stability at -20 °C, with 70 % capacity retention after 10,000 long cycles. This study provides an effective strategy for the preparation of full-performance eutectogel electrolytes.

An Underwater Robust-Adhesion Triboelectric Ion-Gel Enabled by Amphiphilic Copolymer Encapsulation and Water-Induced Interfacial Rearrangement

Water drives the electronic device adhesion interface to debonding, leading to attenuation or distortion of signals and limiting the potential for underwater applications. Here, a hydrophobic ion-gel (HIG) modeled on barnacle gum was developed by encapsulating the ionic liquid [BMIm]Cl in a copolymer formed by free radical quenching of a lignin-carbohydrate complex (LCC) and polythioctic acid (PTA). Due to the dynamic bonding and hydrophobic action to promote the strong underwater adhesion, and a hydrophobic lining hydration structure that improves the underwater stability, the resulting HIG exhibits superextensibility (maximum 10,286%), stable underwater conductivity (180 mS m-1), strong underwater adhesion (maximum 15 N/cm2), and rapid underwater self-healing. It can be used as a single-electrode triboelectric sensor without the need for additional adhesives and encapsulation design and simply adheres to the glove, enabling durable sensing and communication under water. The proposed strategy offers a novel possibility for the material design of flexible and wearable underwater electronics.

Deep eutectic solvent-mediated extraction of lignin: A novel strategy for producing high-quality biopolymers in controlled-release mulching applications

Microplastic contamination of low-density polyethylene mulch and nutrient loss from fertilizers present significant challenges in the crop-growing. In this study, the focus was on creating a biodegradable film that combines the advantages of plastic film, thermal insulation and water retention, as well as the controlled release of fertilizer. A key innovation was the efficient introduction of low molecular weight and low dispersibility of poplar lignin into chitosan and polyvinyl alcohol matrices. The lignin was extracted using deep eutectic solvents of binary carboxylic acids (choline chloride and maleic acid). The refined lignin was used as a superhydrophobic additive to improve the mechanical properties, hydrophobicity, and controlled nutrient release properties of the films through cross-linking. The mulch attained a tensile strength of 37.6 MPa, an elongation of 644.1 %, and a precise release of 53.1 % urea over 30 d at the ideal lignin content ratio (10 %). Furthermore, the film proficiently regulated soil temperature and moisture content. Successful enhancement of cabbage growth was achieved by actual measurements. This discovery provides innovative ideas for the development of nutrient slow-release high-strength integrated agricultural mulching films to promote sustainable, high-quality green agriculture.

Ionogel Adhesives: From Structural Design to Emerging Applications

Adhesives are indispensable in both daily household applications and advanced industrial settings, where they must deliver exceptional bonding performance. Ionogel adhesives, which feature a supporting polymer network infused with ionic liquid (IL), have emerged as promising candidates due to their unique structural and functional properties. The presence of ionic species within ionogels promotes non-covalent interactions-such as ionic bonds, ion-dipole interactions, and hydrogen bonding-that enhance both cohesion within the material and adhesion to various substrates. These characteristics make ionogels ideal for applications that require robust adhesive performance, especially in demanding environments. Despite the growing interest in ionogel adhesives, a comprehensive review of the latest advancements in this area is lacking. This paper aims to fill this gap by categorizing ionogel adhesives based on their composition and discussing strategies to enhance their adhesive properties. Additionally, novel ionogel adhesives designed for specific applications are highlighted. Finally, the current state of research is summarized, and offers insights into the challenges and future opportunities for the development of ionogel adhesives.

Magnetic Ionogel and Its Applications

Magnetic ionogels, a category of hybrid materials consisting of magnetic nanoparticles and ionic liquids, have garnered significant interest owing to their remarkable attributes, including tunability, flexibility, and reactivity to external magnetic fields. These materials provide a distinctive amalgamation of the benefits of both magnetic nanoparticles and ionogels, resulting in improved efficacy across many applications. Magnetic ionogels may be readily controlled using magnetic fields, rendering them suitable for drug administration, biosensing, soft robotics, and actuators. The capacity to incorporate these materials into dynamic systems presents novel opportunities for the development of responsive, intelligent materials capable of real-time environmental adaptation. Nonetheless, despite the promising potential of magnetic ionogels, problems persist, including the optimization of the magnetic particle dispersion, the enhancement of the ionogel mechanical strength, and the improvement of the long-term stability. This review presents a comprehensive examination of the syntheses, characteristics, and uses of magnetic ionogels, emphasizing significant breakthroughs and persistent problems within the domain. We examine recent advancements and prospective research trajectories aimed at enhancing the design and efficacy of magnetic ionogels for practical applications across diverse fields, including biomedical uses, sensors, and next-generation actuators. This review seeks to elucidate the present status of magnetic ionogels and their prospective influence on materials science and engineering.

Deep eutectic solvent-based ionogel: Innovative potential as a promising chromatographic separation material

BACKGROUND

Ionogels, composed of cross-linked polymer networks with abundant anions and cations as dispersion media, have emerged as promising materials. The superior properties of ionogels suggest that they may offer valuable contributions to the development of novel chromatographic stationary phase. However, the potential application of ionogels as the charming materials in liquid chromatography has been limited, primarily due to the hydrophilic nature, leading to swelling and increased column pressure. To address this issue, a paradigm-shifting innovation was proposed by incorporating deep eutectic solvent (DES) to facilitate the formation of robust hydrogen bond networks, thereby reducing the swelling tendency of ionogel.

RESULTS

In this study, an environmentally friendly DES was selected as the optimal alternative to the traditional ionic liquid for the formation of a DES-based ionogel. By combining the ionogel with the silica gel matrix, a DES-Ionogel@SiO2 stationary phase was prepared. The whole synthesis process of DES-Ionogel@SiO2 was conducted in the green DES. The swelling tendency of ionogel as a functionalized chromatographic material was significantly reduced, thereby mitigating the risk of undue column pressure. This innovation results in a DES-based stationary phase with enhanced stability and durability in aqueous media, which is pivotal for maintaining the performance and longevity of chromatographic column. The DES-Ionogel@SiO2 stationary phase exhibits a distinctive mixed-mode retention mechanism, which is a highly desirable attribute in diverse chromatographic applications. This endows the developed chromatographic column with a broad applicability for the separation of complex samples, such as nucleosides, phenyl ketones, phthalates, alkylphenols, steroid hormones and position isomers.

SIGNIFICANCE

This work presents an innovative approach and green in-situ growth strategy for the development of a versatile ionogel stationary phase, and marks the first time that DES-based ionogel has been synthesized and used to modify silica gel as a promising chromatographic separation material, showcasing the revolutionary potential of DES-based ionogel in the field of liquid chromatography.

Choline-Based Deep Eutectic Solvents for Enzymatic Preparation of Epoxy Linseed Oil

Deep eutectic solvents (DESs) hold the potential to serve as a sustainable and environmentally friendly substitute for supercritical fluids, ionic liquids, and organic solvents. Moreover, DESs have been demonstrated to assist in stabilizing the structure of enzyme. The enzymatic synthesis of epoxy vegetable oil in a DES-system was developed in this study, and the influence of DESs viscosity on the epoxidation system was investigated for the first time. The results demonstrated that the epoxy value reached 8.97, and the double bond conversion rate was 82.48%. The viscosity of the reaction system decreased from 209.32 to 91.35 (mPa·s). The application of DES in epoxidation was confirmed through structural characterization, indicating that eutectic solvents could serve as substitutes for toxic and volatile organic solvents in synthesizing high-epoxide vegetable oils using an enzymatic method, thus facilitating the production of environmentally friendly plasticizers.

Tough and Stretchable Zwitterionic Eutectogels via Copolymerization-Induced Phase Separation in a Targeted Deep Eutectic Solvent

Deep eutectic solvent (DES)-based eutectogels show significant promise for flexible sensors due to their high ionic conductivity, non-volatility, biocompatibility, and cost-effectiveness. However, achieving tough and stretchable eutectogels is challenging, as the highly polar DES tends to screen noncovalent bonds, such as hydrogen and ionic bonds, between polymer chains, limiting their mechanical strength. In this work, this issue is addressed by leveraging the limited solubility of zwitterionic polymers in a specific DES to induce phase separation, promoting dipole-dipole interactions between polymer chains. These interactions improve energy dissipation under mechanical stress, allowing the creation of tough and stretchable P(MAA-co-VIPS)/TBAC-EG eutectogels through a copolymerization-induced phase separation approach. Methacrylic acid (MAA) and sulfobetaine vinylimidazole (VIPS) are copolymerized within a tetrabutylammonium chloride-ethylene glycol (TBAC-EG) DES, resulting in a bicontinuous network. The bicontinuous structure consists of a PVIPS-rich phase that enhances toughness via dipole-dipole interactions, and a PMAA solvent-rich phase that enables high stretchability. The resulting eutectogel demonstrates excellent mechanical properties, including a strength of 1.76 MPa, toughness of 16.61 MJ m⁻3, and remarkable stretchability of 1293%, along with self-recovery, self-healing, and shape-memory capabilities. The zwitterionic polymer-specific DES design opens up broad application potential for these eutectogels in diverse fields.

Soy Protein Adhesive Enhanced Through Supramolecular Interaction with Tannic Acid Modified Montmorillonite

The use of soybean meal (SM) as an alternative to petroleum-based resins in wood-based panels offers a solution to the problem of formaldehyde release. However, inherent drawbacks of soybean meal adhesives, such as poor toughness, low bond strength, and susceptibility to mold, have hindered their further development. In this study, a novel biomass adhesive, SM-MMT@TA, was developed based on supramolecular interactions between tannic acid (TA), montmorillonite (MMT), and soybean meal. Tannic acid was securely attached to the MMT surface through coordination bonds with Ca2+, Mg2+, and Al3+ ions, enhancing MMT's compatibility in the matrix via strong interfacial interactions. TA on the surface of MMT@TA effectively bonded with soy protein through strong hydrogen bonding, thereby increasing the crosslink density. As a result, the adhesive exhibited a wet shear strength of up to 1.75 MPa, which represents a 143.05 % increase compared to unmodified SM adhesive. Moreover, the moisture absorption rate of the adhesive was reduced to 26.79 %. Furthermore, abundant non-covalent interactions improved the adhesive's toughness, while natural polyphenols provided additional mold resistance. Overall, this study presents a new strategy for developing renewable, high-performance biomass-based adhesives.

Rigid-Flexible Coupled Dendritic Molecule Doping: General Approach to Activate Commercial Polymers into Harsh Condition-Tolerant Multi-Reusable Strong Supramolecular Adhesives

Developing functional adhesives combining strong adhesion, good recyclability and diverse harsh-condition adaptability is a grand challenge. Here, we introduce a general dendritic molecule doping strategy to activate commercial polymers into a new family of supramolecular adhesives integrating high adhesion strength, ultralow temperature, water resistant and multi-reusable properties. Our method involves rational design of a new rigid-flexible coupled dendritic molecule-M4C8OH as a versatile dopant, while simple M4C8OH doping into commercial polymers can modulate internal and external non-covalent interaction to enable H-bonding enhanced interchain cross-linking for tough cohesion along with enhanced interphase interaction. This endows 20 wt % M4C8OH-doped polycaprolactone (PCL) adhesives (PCL-M4C8OH) with improved adhesion strength on various substrates with the maximum increase up to 2.87 times that of PCL. In particular, the adhesion strengths of PCL-M4C8OH on polymethyl methacrylate at 25 °C and -196 °C reach 4.67 and 3.58 MPa-1.9 and 2.3 times those of PCL and superior to diverse commercial adhesives and most reported adhesives. PCL-M4C8OH also displays markedly-improved multi-usability and tolerance against ultralow temperature and diverse wet environments. Mechanism studies reveal the crucial role of M4C8OH molecular structures toward superior adhesion. Our method can be expanded to other polymer matrices, yielding diverse new supramolecular adhesives.

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.

Zwitterionic cellulose nanofibers-based hydrogels with high toughness, ionic conductivity, and healable capability in cryogenic environments

Extreme environmental conditions often lead to irreversible structural failure and functional degradation in hydrogels, limiting their service life and applicability. Achieving high toughness, self-healing, and ionic conductivity in cryogenic environments is vital to broaden their applications. Herein, we present a novel approach to simultaneously enhance the toughness, self-healing, and ionic conductivity of hydrogels, via inducing non-freezable water within the zwitterionic cellulose-based hydrogel skeleton. This approach enables resulting hydrogel to achieve an exceptional toughness of 10.8 MJ m-3, rapid self-healing capability (98.9 % in 30 min), and high ionic conductivity (2.9 S m-1), even when subjected to -40 °C, superior to the state-of-the-art hydrogels. Mechanism analyses reveal that a significant amount of non-freezable water with robust electrostatic interactions is formed within zwitterionic cellulose nanofibers-modified polyurethane molecular networks, imparting superior freezing tolerance and versatility to the hydrogel. Importantly, this strategy harnesses the non-freezable water molecular state of the zwitterionic cellulose nanofibers network, eliminating the need for additional antifreeze and organic solvents. Furthermore, the dynamic Zn coordination within these supramolecular molecule chains enhances interfacial interactions, thereby promoting rapid subzero self-healing and exceptional mechanical strength. Demonstrating its potential, this hydrogel can be used in smart laminated materials, such as aircraft windshields.

A self-bonding conductive electrode triggered by water-induced structure reconfiguration

This study presents a self-bonding conductive electrode triggered by water-induced structure reconfiguration. Water wetting causes the swelling and mobility of cotton-derived cellulose nanofibers in the conductive electrode, and the formation of hydrogen bonds, which enables the conductive electrode to heal damage, bond separated pieces, and directly bond on diverse substrates.

Conductive Hyaluronic Acid/Deep Eutectic Solvent Composite Hydrogel as a Wound Dressing for Promoting Skin Burn Healing Under Electrical Stimulation

Burns can cause severe damage to the skin due to bacterial infection and severe inflammation. Although conductive hydrogels as electroactive burn-wound dressings achieve remarkable effects on accelerating wound healing, issues such as imbalance between their high conductivity and mechanical properties, easy dehydration, and low transparency must be addressed. Herein, a double-network conductive eutectogel is fabricated by integrating polymerizable deep eutectic solvents (PDESs)including acrylamide/choline chloride/glycerol (acrylamide-polymerization crosslink) and thiolated hyaluronic acid (disulfide-bonding crosslink). The introduction of PDESs provides the eutectogel with a conductivity (up to 0.25 S·m-1) and mechanical strength (tensile strain of 59-77%) simulating those of natural human skin, as well as satisfactory tissue adhesiveness, self-healing ability, and antibacterial properties. When combined with exogenous electrical stimulation, the conductive eutectogel exhibits the ability to reduce inflammation, stimulate cell proliferation and migration, promote collagen deposition and angiogenesis, and facilitate skin tissue remodeling. This conductive eutectogel shows great potential as a dressing for healing major burn wounds.

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.

A thermally reversible injectable adhesive for intestinal tissue repair and anti-postoperative adhesion

Intestine damage is an acute abdominal disease that usually requires emergency sealing. However, traditional surgical suture not only causes secondary damage to the injured tissue, but also results in adhesion with other tissues in the abdominal cavity. To this end, a thermally reversible injectable gelatin-based hydrogel adhesive (GTPC) is constructed by introducing transglutaminase (TGase) and proanthocyanidins (PCs) into a gelatin system. By reducing the catalytic activity of TGase, the density of covalent and hydrogen bond crosslinking in the hydrogel can be regulated to tune the sol-gel transition temperature of gelatin-based hydrogels above the physiological temperature (42 °C) without introducing any synthetic small molecules. The GTPC hydrogel exhibits good tissue adhesion, antioxidant, and antibacterial properties, which can effectively seal damaged intestinal tissues and regulate the microenvironment of the damaged site, promoting tissue repair and regeneration. Intriguingly, temperature-induced hydrogen bond disruption and reformation confer the hydrogel with asymmetric adhesion properties, preventing tissue adhesion when applied in vivo. Animal experiment outcomes reveal that the GTPC hydrogel can seal the damaged intestinal tissue firmly, accelerate tissue healing, and efficiently prevent postoperative adhesion.

Exploring Mixed Ionic-Electronic-Conducting PVA/PEDOT:PSS Hydrogels as Channel Materials for Organic Electrochemical Transistors

Here, we report the preparation and evaluation of PVA/PEDOT:PSS-conducting hydrogels working as channel materials for OECT applications, focusing on the understanding of their charge transport and transfer properties. Our conducting hydrogels are based on crosslinked PVA with PEDOT:PSS interacting via hydrogen bonding and exhibit an excellent swelling ratio of ~180-200% w/w. Our electrochemical impedance studies indicate that the charge transport and transfer processes at the channel material based on conducting hydrogels are not trivial compared to conducting polymeric films. The most relevant feature is that the ionic transport through the swollen hydrogel is clearly different from the transport through the solution, and the charge transfer and diffusion processes govern the low-frequency regime. In addition, we have performed in operando Raman spectroscopy analyses in the OECT devices supported by first-principle computational simulations corroborating the doping/de-doping processes under different applied gate voltages. The maximum transconductance (gm~1.05 μS) and maximum volumetric capacitance (C*~2.3 F.cm-3) values indicate that these conducting hydrogels can be promising candidates as channel materials for OECT devices.

Multiple physical crosslinked highly adhesive and conductive hydrogels for human motion and electrophysiological signal monitoring

Hydrogel-based flexible electronic devices serve as a next-generation bridge for human-machine interaction and find extensive applications in clinical therapy, military equipment, and wearable devices. However, the mechanical mismatch between hydrogels and human tissues, coupled with the failure of conformal interfaces, hinders the transmission of information between living organisms and flexible devices, which resulted in the instability and low fidelity of signals, especially in the acquisition of electromyographic (EMG) and electrocardiographic (ECG) signals. In this study, we designed an ion-conductive hydrogel (ICHgel) utilizing multiple physical interactions, successfully applied for human motion monitoring and the collection of epidermal physiological signals. By incorporating fumed silica (F-SiO2) nanoparticles and calcium chloride into an interpenetrating network (IPN) composed of polyvinyl alcohol (PVA) and polyacrylamide (AAm)/acrylic acid (AA) chains, the ICHgel exhibited exceptional tunable stretchability (>1450% strain) and conductivity (10.58 ± 0.85 S m-1). Additionally, the outstanding adhesion of the ICHgel proved to be a critical factor for effective communication between epidermal tissues and flexible devices. Demonstrating its capability to acquire stable electromechanical signals, the ICHgel was attached to different parts of the human body. More importantly, as a flexible electrode, the ICHgel outperformed commercial Ag/AgCl electrodes in the collection of ECG and EMG signals. In summary, the synthesized ICHgel with its outstanding conformal interface capabilities and mechanical adaptability paves the way for enhanced human-machine interaction, fostering the development of flexible electronic devices.

Wetting-enhanced adhesion of photo-polymerized supramolecular adhesives for both smooth and rough surfaces

Efficient interactions between an adhesive and a substrate surface at the molecular level are the basis for the formation of robust adhesion, which substantially relies on interfacial wetting. However, strong adhesives usually improve cohesion but compromise interfacial properties. Herein, we have reported a kind of robust supramolecular adhesive based on the outstanding mobility and interfacial wettability of adhesive precursors. In situ fast photopolymerization endows supramolecular adhesives with more outstanding adhesion for both smooth and rough surfaces in air and underwater in contrast to their counterparts from thermal polymerization. In addition to their low viscosity and high monomer concentration, supramolecular adhesive precursors without any organic solvents possess well-defined hydrogen bonding interactions. These superior properties consistently contribute to the wetting of the substrate and the formation of adhesive polymers with high molecular weights. This work highlights that enhancing interfacial wetting between an adhesive and a substrate is a promising route to achieving robust adhesion.

Compliant Iontronic Triboelectric Gels with Phase-Locked Structure Enabled by Competitive Hydrogen Bonding

Rapid advancements in flexible electronics technology propel soft tactile sensing devices toward high-level biointegration, even attaining tactile perception capabilities surpassing human skin. However, the inherent mechanical mismatch resulting from deficient biomimetic mechanical properties of sensing materials poses a challenge to the application of wearable tactile sensing devices in human-machine interaction. Inspired by the innate biphasic structure of human subcutaneous tissue, this study discloses a skin-compliant wearable iontronic triboelectric gel via phase separation induced by competitive hydrogen bonding. Solvent-nonsolvent interactions are used to construct competitive hydrogen bonding systems to trigger phase separation, and the resulting soft-hard alternating phase-locked structure confers the iontronic triboelectric gel with Young's modulus (6.8-281.9 kPa) and high tensile properties (880%) compatible with human skin. The abundance of reactive hydroxyl groups gives the gel excellent tribopositive and self-adhesive properties (peel strength > 70 N m-1). The self-powered tactile sensing skin based on this gel maintains favorable interface and mechanical stability with the working object, which greatly ensures the high fidelity and reliability of soft tactile sensing signals. This strategy, enabling skin-compliant design and broad dynamic tunability of the mechanical properties of sensing materials, presents a universal platform for broad applications from soft robots to wearable electronics.

Quantification of alkalinity of deep eutectic solvents based on (H-) and NMR

Alkaline deep eutectic solvents (DESs) have been widely employed across diverse fields. A comprehensive understanding of the alkalinity data is imperative for the comprehension of their performance. However, the current range of techniques for quantifying alkalinity is constrained. In this investigation, we formulated a series of alkaline DESs and assessed their basicity properties through a comprehensive methodology of Hammett functions alongside 1H NMR analysis. A correlation was established between the composition, structure and alkalinity of solvents. Furthermore, a strong linear correlation was observed between the Hammett basicity (H-) of solvents and initial CO2 adsorption rate. Machine learning techniques were employed to predict the significant impact of alkaline functional components on alkalinity levels and CO2 capture capacity. This study offers valuable insights into the design, synthesis and structure-function relationship of alkaline DESs.

Solvent-Resistant Adhesive Gel with Thermal Post-Tunability

Adhesives have received extensive attention in flexible bioelectronics, wearable electronic medical devices, and biofuel cells. However, it is a challenge to achieve late regulation of performance once polymer-based gels are formed. Here, a double-network organogel composed of a hydrophilic and hydrophobic polymer network and a polyamide acid network was successfully prepared. In diverse liquid environments (including isopropyl alcohol, glycerol, epichlorohydrin, n-propanol, dichloromethane, triethanolamine, ethanol absolute, hydrogen peroxide, and ethyl acetate), the organogel adhesive demonstrated remarkable properties. It exhibits a strong tensile strength of 200 kPa, a high fracture strain reaching 560%, and an impressive adhesion strength of 38 kPa. In addition, the organogel demonstrates exceptional adhesive properties toward polytetrafluoroethylene, plastics, metals, rubber, and glass. Note that the organogel could also regulate adhesive and tough performance by thermally triggering a cyclization reaction even after the organogel has been formed. The strategy provides a new idea for designing soft materials with post-tunability.

Ultra-Tough and Highly Stretchable Dual-Crosslinked Eutectogel Based on Coordinated and Non-Coordinated Two Types Deep Eutectic Solvent Mixture

Eutectogels are gaining attention in flexible device applications for their superior ionic conductivity, stability, biocompatibility, and cost-effectiveness. However, most existing eutectogels suffer from low strength and toughness. Herein, ultra-tough and highly stretchable polyacrylamide (PAM) eutectogels featuring a dual-crosslinked network comprising chemical cross-linking and physical cross-linking facilitated by metal coordination bonds and hydrogen bonds are developed. This is achieved through a controlled strategy involving polymerization of acrylamide in a coordinated metal salt-type deep eutectic solvent (DES) combined with a non-coordinated choline chloride (ChCl)-type DES mixture. By varying the molar ratio of these two types of DES, exceptional and adjustable mechanical properties of the resulting eutectogel are achieved, including a high tensile strength ranging from 2.9 to 8.2 MPa and elongation at break ranging from 1725 to 747%, at a 70 wt% DES content. Furthermore, the reversible non-covalent crosslinking in these eutectogels enables self-recovery and self-healing capabilities of eutectogels. The prepared eutectogels also exhibit outstanding ionic conductivity (3.56 mS cm-1 ), making them well-suited for use as strain sensors in human motion detection. The toughening strategy is universally effective for creating tough eutectogels using coordinated metal salt-type DES with various metal ions, as well as a diverse range of coordinatable polymers.

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.

Topical drug delivery strategies for enhancing drug effectiveness by skin barriers, drug delivery systems and individualized dosing

Topical drug delivery is widely used in various diseases because of the advantages of not passing through the gastrointestinal tract, avoiding gastrointestinal irritation and hepatic first-pass effect, and reaching the lesion directly to reduce unnecessary adverse reactions. The skin helps the organism to defend itself against a huge majority of external aggressions and is one of the most important lines of defense of the body. However, the skin's strong barrier ability is also a huge obstacle to the effectiveness of topical medications. Allowing the bioactive, composition in a drug to pass through the stratum corneum barrier as needed to reach the target site is the most essential need for the bioactive, composition to exert its therapeutic effect. The state of the skin barrier, the choice of delivery system for the bioactive, composition, and individualized disease detection and dosing planning influence the effectiveness of topical medications. Nowadays, enhancing transdermal absorption of topically applied drugs is the hottest research area. However, enhancing transdermal absorption of drugs is not the first choice to improve the effectiveness of all drugs. Excessive transdermal absorption enhances topical drug accumulation at non-target sites and the occurrence of adverse reactions. This paper introduces topical drug delivery strategies to improve drug effectiveness from three perspectives: skin barrier, drug delivery system and individualized drug delivery, describes the current status and shortcomings of topical drug research, and provides new directions and ideas for topical drug research.

Photoswitchable and Reversible Fluorescent Eutectogels for Conformal Information Encryption

Smart fluorescent materials that can respond to environmental stimuli are of great importance in the fields of information encryption and anti-counterfeiting. However, traditional fluorescent materials usually face problems such as lack of tunable fluorescence and insufficient surface-adaptive adhesion, hindering their practical applications. Herein, inspired by the glowing sucker octopus, we present a novel strategy to fabricate a reversible fluorescent eutectogel with high transparency, adhesive and self-healing performance for conformal information encryption and anti-counterfeiting. Using anthracene as luminescent unit, the eutectogel exhibits photoswitchable fluorescence and can therefore be reversibly written/erased with patterns by non-contact stimulation. Additionally, different from mechanically irreversible adhesion via glue, the eutectogel can adhere to various irregular substrates over a wide temperature range (-20 to 65 °C) and conformally deform more than 1000 times without peeling off. Furthermore, by exploiting surface-adaptive adhesion, high transparency and good stretchability of the eutectogel, dual encryption can be achieved under UV and stretching conditions to further improve the security level. This study should provide a promising strategy for the future development of advanced intelligent anti-counterfeiting materials.

Super tough and high adhesive eutectic ionogels enabled by high-density hydrogen bond network

Ionogels have attracted tremendous interest for flexible electronics due to their excellent deformability, conductivity, and environmental stability. However, most ionogels suffer from low strength and poor toughness, which limit their practical applications. This article presents a strategy for fabricating ionogels with high toughness by constructing high-density hydrogen bonds within their microstructure. The ionogels exhibit a maximum fracture strength of 11.44 MPa, and can sustain a fracture strain of 506%. They also demonstrate a fracture energy of 27.29 MJ m-3 and offer a wide range of mechanical property adjustments (fracture stress from 0.3 to 11.44 MPa, fracture strain from 506% to 1050%). Strain sensors assembled with ionogels demonstrate exceptional sensing performance and enable motion detection of human joints. This study provides a new approach for achieving strong and tough ionogel design used for high-performance flexible electronic applications.

Effects of Short-Term Exposure of Chloramine-T Solution on the Characteristics of Light-Cured and Chemical-Cured Adhesives

This study evaluated the effect of a 0.5% chloramine T solution on a chemical-cured universal adhesive by comparing the light-cured, one-step, self-etch adhesive for the bonding performance, mechanical properties, and resin-dentin interfacial characteristics. Caries-free human molars were randomly assigned into eight groups based on the bonding systems employed (Bond Force II, BF and Bondmer Lightless, BL), the immersion solutions used before bonding (0.5% chloramine T solution and distilled water), and the immersion durations (5 and 60 min). Microtensile bond strength (μTBS), nanoleakage evaluation, and nanoindentation tests were performed, and the surface morphology of the resin-dentin interface was examined using a focus ion beam/scanning ion microscopy system. Immersion in chloramine-T for 5 min significantly decreased the μTBS of Bondmer Lightless (from 22.62 to 12.87 MPa) compared with that in distilled water. Moreover, there was also a decreasing trend after immersing in chloramine-T for 60 min (from 19.11 to 13.93 MPa). Chloramine T was found to have no effect on the hardness, elastic modulus, or morphological characteristics of the ion-beam milled resin-dentin interfacial surfaces in the tested adhesives, suggesting that chloramine T might reduce the bond strength by interfering with the interaction and the sealing between the adhesive resin and dentin in the chemical-cured universal adhesive, albeit without affecting the mechanical properties.

Recent Progress of the Vat Photopolymerization Technique in Tissue Engineering: A Brief Review of Mechanisms, Methods, Materials, and Applications

Vat photopolymerization (VP), including stereolithography (SLA), digital light processing (DLP), and volumetric printing, employs UV or visible light to solidify cell-laden photoactive bioresin contained within a vat in a point-by-point, layer-by-layer, or volumetric manner. VP-based bioprinting has garnered substantial attention in both academia and industry due to its unprecedented control over printing resolution and accuracy, as well as its rapid printing speed. It holds tremendous potential for the fabrication of tissue- and organ-like structures in the field of regenerative medicine. This review summarizes the recent progress of VP in the fields of tissue engineering and regenerative medicine. First, it introduces the mechanism of photopolymerization, followed by an explanation of the printing technique and commonly used biomaterials. Furthermore, the application of VP-based bioprinting in tissue engineering was discussed. Finally, the challenges facing VP-based bioprinting are discussed, and the future trends in VP-based bioprinting are projected.

Single-Line Multi-Channel Flexible Stress Sensor Arrays

Flexible stress sensor arrays, comprising multiple flexible stress sensor units, enable accurate quantification and analysis of spatial stress distribution. Nevertheless, the current implementation of flexible stress sensor arrays faces the challenge of excessive signal wires, resulting in reduced deformability, stability, reliability, and increased costs. The primary obstacle lies in the electric amplitude modulation nature of the sensor unit's signal (e.g., resistance and capacitance), allowing only one signal per wire. To overcome this challenge, the single-line multi-channel signal (SLMC) measurement has been developed, enabling simultaneous detection of multiple sensor signals through one or two signal wires, which effectively reduces the number of signal wires, thereby enhancing stability, deformability, and reliability. This review offers a general knowledge of SLMC measurement beginning with flexible stress sensors and their piezoresistive, capacitive, piezoelectric, and triboelectric sensing mechanisms. A further discussion is given on different arraying methods and their corresponding advantages and disadvantages. Finally, this review categorizes existing SLMC measurement methods into RLC series resonant sensing, transmission line sensing, ionic conductor sensing, triboelectric sensing, piezoresistive sensing, and distributed fiber optic sensing based on their mechanisms, describes the mechanisms and characteristics of each method and summarizes the research status of SLMC measurement.

Structural Engineering in Piezoresistive Micropressure Sensors: A Focused Review

The longstanding demands for micropressure detection in commercial and industrial applications have led to the rapid development of relevant sensors. As a type of long-term favored device based on microelectromechanical system technology, the piezoresistive micropressure sensor has become a powerful measuring platform owing to its simple operational principle, favorable sensitivity and accuracy, mature fabrication, and low cost. Structural engineering in the sensing diaphragm and piezoresistor serves as a core issue in the construction of the micropressure sensor and undertakes the task of promoting the overall performance for the device. This paper focuses on the representative structural engineering in the development of the piezoresistive micropressure sensor, largely concerning the trade-off between measurement sensitivity and nonlinearity. Functional elements on the top and bottom layers of the diaphragm are summarized, and the influences of the shapes and arrangements of the piezoresistors are also discussed. The addition of new materials endows the research with possible solutions for applications in harsh environments. A prediction for future tends is presented, including emerging advances in materials science and micromachining techniques that will help the sensor become a stronger participant for the upcoming sensor epoch.

Internet-of-Things-Based Multiple-Sensor Monitoring System for Soil Information Diagnosis Using a Smartphone

The rise of Internet of Things (IoT) technology has moved the digital world in a new direction and is considered the third wave of the information industry. To meet the current growing demand for food, the agricultural industry should adopt updated technologies and smart agriculture based on the IoT which will strongly enable farmers to reduce waste and increase productivity. This research presents a novel system for the application of IoT technology in agricultural soil measurements, which consists of multiple sensors (temperature and moisture), a micro-processor, a microcomputer, a cloud platform, and a mobile phone application. The wireless sensors can collect and transmit soil information in real time with a high speed, while the mobile phone app uses the cloud platform as a monitoring center. A low power consumption is specified in the hardware and software, and a modular power supply and time-saving algorithm are adopted to improve the energy effectiveness of the nodes. Meanwhile, a novel soil information prediction strategy was explored based on the deep Q network (DQN) reinforcement learning algorithm. Following the weighted combination of a bidirectional long short-term memory, online sequential extreme learning machine, and parallel extreme machine learning, the DQN Bi-OS-P prediction model was obtained. The proposed data acquisition system achieved a long-term stable and reliable collection of time-series soil data with equal intervals and provided an accurate dataset for the precise diagnosis of soil information. The RMSE, MAE, and MAPE of the DQN Bi-OS-P were all reduced, and the R2 was improved by 0.1% when compared to other methods. This research successfully implemented the smart soil system and experimentally showed that the time error between the value displayed on the mobile phone app and its exact acquisition moment was no more than 3 s, proving that mobile applications can be effectively used for the real-time monitoring of soil quality and conditions in wireless multi-sensing based on the Internet of Things.

Liquid Metal Flexible EMG Gel Electrodes for Gesture Recognition

Gesture recognition has been playing an increasingly important role in the field of intelligent control and human-computer interaction. Gesture recognition technology based on electromyography (EMG) with high accuracy has been widely applied. However, conventional rigid EMG electrodes do not fit the mechanical properties of human skin. Therefore, rigid EMG electrodes are easily influenced by body movements, and uncomfortable to wear and use for a long time. To solve these problems, a stretchable EMG electrode based on liquid metal nanoparticles was developed in this research. It is conformal with human skin because of its similar mechanical properties to skin. Liquid metal nanoparticles mixed in polymer can be connected to each other to form conductive circuits when pressed by mechanical force. Therefore, this preparation method of liquid metal flexible gel electrodes is low-cost and can be fabricated largely. Moreover, the liquid metal flexible gel electrodes have great stretch ability. Their resistance increases slightly at maximum strain state. Based on these advantages, the flexible gel electrodes are applied to arm to collect EMG signals generated by human hand movements. In addition, the signals are analyzed by artificial intelligence algorithm to realize accurate gesture recognition.

Preparation of Nanocomposites for Antibacterial Orthodontic Invisible Appliance Based on Piezoelectric Catalysis

Compared to fixed orthodontic appliances with brackets, thermoplastic invisible orthodontic aligners offer several advantages, such as high aesthetic performance, good comfort, and convenient oral health maintenance, and are widely used in orthodontic fields. However, prolonged use of thermoplastic invisible aligners may lead to demineralization and even caries in most patients' teeth, as they enclose the tooth surface for an extended period. To address this issue, we have created PETG composites that contain piezoelectric barium titanate nanoparticles (BaTiO₃NPs) to obtain antibacterial properties. First, we prepared piezoelectric composites by incorporating varying amounts of BaTiO₃NPs into PETG matrix material. The composites were then characterized using techniques such as SEM, XRD, and Raman spectroscopy, which confirmed the successful synthesis of the composites. We cultivated biofilms of Streptococcus mutans (S. mutans) on the surface of the nanocomposites under both polarized and unpolarized conditions. We then activated piezoelectric charges by subjecting the nanocomposites to 10 Hz cyclic mechanical vibration. The interactions between the biofilms and materials were evaluated by measuring the biofilm biomass. The addition of piezoelectric nanoparticles had a noticeable antibacterial effect on both the unpolarized and polarized conditions. Under polarized conditions, nanocomposites demonstrated a greater antibacterial effect than under unpolarized conditions. Additionally, as the concentration of BaTiO₃NPs increased, the antibacterial rate also increased, with the surface antibacterial rate reaching 67.39% (30 wt% BaTiO₃NPs). These findings have the potential for application in wearable, invisible appliances to improve clinical services and reduce the need for cleaning methods.

Multiple Responsive Hydrogel Films Based on Dynamic Phenylboronate Bond Linkages with Simple but Practical Linear Response Mode and Excellent Glucose/Fructose Response Speed

Multiple responsive hydrogels are usually constructed by the addition of many different functional groups. Generally, these groups have different responsive behaviors which lead to interleaved and complex modes of the multi-response system. It is difficult to get a practical application. In this study, we show that multi-response hydrogels can also be constructed using dynamic bonds as crosslinks. The multiple responsive hydrogel films with thicknesses on the sub-micrometer or micrometer scale can be fabricated from P(DMAA-3-AAPBA), a copolymer of N,N-dimethylacrylamide, 3-(acrylamido)phenylboronic acid, and poly(vinylalcohol) (PVA) though a simple layer-by-layer (LbL) technique. The driving force for the film build up is the in situ-formed phenylboronate ester bonds between the two polymers. The films exhibit Fabry-Perot fringes on their reflection spectra which can be used to calculate the equilibrium swelling degree (SD_e) of the film so as to characterize its responsive behaviors. The results show that the films are responsive to temperature, glucose, and fructose with simple and practical linear response modes. More importantly, the speed of which the films respond to glucose or fructose is quite fast, with characteristic response times of 45 s and 7 s, respectively. These quick response films may have potential for real-time, continuous glucose or fructose monitoring. With the ability to bind with these biologically important molecules, one can expect that hydrogels may find more applications in biomedical areas in the future.

Reinforcement of Nanocomposite Hydrogel with Dialdehyde Cellulose Nanofibrils via Physical and Double Network Crosslinking Synergies

Preparation of tough and high-strength hydrogels for water plugging in oil fields with an easy-scalable method is still considered to be a challenge. In this study, dialdehyde cellulose nanofibril (DA-CNF) prepared by sodium periodate oxidation, polyamine, 2-acrylamido-2-methylpropane sulfonic acid (AMPS) with sulfonate groups and Acrylamide (AM) as raw materials, CNF reinforced nanocomposite hydrogels were prepared in one step by in-situ polymerization. The tensile strength, and texture stability of the obtained nanocomposite hydrogel were determined. The results showed that the tensile strength and toughness of the obtained nanocomposite hydrogel increased four times compared with control sample due to physical and chemical double crosslinking synergies. Moreover, the texture intensity of DA-CNFs reinforced hydrogel still maintains high stability and strength performance under high salinity conditions. Therefore, DA-CNF reinforced hydrogel has potential application value in both normal and high-salinity environments in oil recovery.

Heterogeneous Multi-Material Flexible Piezoresistive Sensor with High Sensitivity and Wide Measurement Range

Flexible piezoresistive sensors (FPSs) have the advantages of compact structure, convenient signal acquisition and fast dynamic response; they are widely used in motion detection, wearable electronic devices and electronic skins. FPSs accomplish the measurement of stresses through piezoresistive material (PM). However, FPSs based on a single PM cannot achieve high sensitivity and wide measurement range simultaneously. To solve this problem, a heterogeneous multi-material flexible piezoresistive sensor (HMFPS) with high sensitivity and a wide measurement range is proposed. The HMFPS consists of a graphene foam (GF), a PDMS layer and an interdigital electrode. Among them, the GF serves as a sensing layer, providing high sensitivity, and the PDMS serves as a supporting layer, providing a large measurement range. The influence and principle of the heterogeneous multi-material (HM) on the piezoresistivity were investigated by comparing the three HMFPS with different sizes. The HM proved to be an effective way to produce flexible sensors with high sensitivity and a wide measurement range. The HMFPS-10 has a sensitivity of 0.695 kPa^-1, a measurement range of 0-14,122 kPa, fast response/recovery (83 ms and 166 ms) and excellent stability (2000 cycles). In addition, the potential application of the HMFPS-10 in human motion monitoring was demonstrated.

Multifunctional Nanoplatform Based on Sunitinib for Synergistic Phototherapy and Molecular Targeted Therapy of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a tumor that poses a serious threat to human health, with an extremely low five-year survival rate due to its difficulty in early diagnosis and insensitivity to radiotherapy and chemotherapy. To improve the therapeutic efficiency of HCC, we developed a novel multifunctional nanoplatform (SCF NPs) with an amphiphilic polymer (Ce6-PEG2000-FA) and a multitarget tyrosine kinase inhibitor sunitinib. SCF NPs showed superior therapeutical efficiency for HCC due to the synergetic effect of molecular targeted therapy and phototherapy. The Ce6-PEG2000-FA not only serves as a nanocarrier with excellent biocompatibility but also can act as a therapeutic reagent for photothermal therapy (PTT) and photodynamic therapy (PDT). Furthermore, the folic acid group of Ce6-PEG2000-FA enhanced the active targeting performance of SCF NPs. As a multitargeted tyrosine kinase inhibitor, sunitinib in SCF NPs can play a role in molecular targeted therapies, including tumor growth inhibition and anti-angiogenesis. In vivo experiments, SCF NPs showed multimode imaging capabilities, which can be used for tumorous diagnosis and intraoperative navigation. Meanwhile, SCF NPs showed outstanding synergetic tumor inhibition ability. Tumors of SCF NPs group with laser radiation were eradicated without any recrudescence after 14 days of treatment. Such theranostic nanoparticles offer a novel therapeutic tactic for HCC.