Antifreeze Properties Research Articles

Wearable multifunctional organohydrogel-based electronic skin for sign language recognition under complex environments

Language barrier is the main cause of disagreement. Sign language, which is a common language in all the worldwide language families, is difficult to be entirely popularized due to the high cost of learning as well as the technical barrier in real-time translation. To solve these problems, here, we constructed a wearable organohydrogel-based electronic skin (e-skin) with fast self-healing, strong adhesion, extraordinary anti-freezing and moisturizing properties for sign language recognition under complex environments. The e-skin was obtained by using an acrylic network as the main body, aluminum (III) and bayberry tannin as the crosslinking agent, water/ethylene glycol as the solvent system, and a polyvinyl alcohol network to optimize the network performance. Using this e-skin, a smart glove was further built, which could carry out the large-scale data collection of common gestures and sign languages. With the help of the deep learning method, specific recognition and translation for various gestures and sign languages could be achieved. The accuracy was 93.5%, showing the ultra-high classification accuracy of a sign language interpreter. In short, by integrating multiple characteristics and combining deep learning technology with hydrogel materials, the e-skin achieved an important breakthrough in human-computer interaction and artificial intelligence, and provided a feasible strategy for solving the dilemma of mutual exclusion between flexible electronic devices and human bodies.

Designing Antifreezing Hydrogels with Enhanced Mechanical Properties Using a Simple Crosslinker

Antifreezing hydrogels are essential for materials design and practical applications, but their development and understanding have been challenging due to their high-water content. Current antifreezing hydrogels typically rely on organic solvents or the addition of antifreezing agents. In this study, we present a novel crosslinking strategy to fabricate antifreezing hydrogels without the need for additional antifreezing agents. We introduce a new crosslinker, PEGn-EGINA, which combines highly hydrophilic EGINA with polyethylene glycol (PEG) of varying molecular weights. Utilizing PEGn-EGINA as the crosslinker, we synthesize Agar/Polyacrylamide (Agar/PAAm) double-network hydrogels, alongside conventional MBAA-crosslinked hydrogels for comparison. The resulting PEGn-EGINA-crosslinked hydrogels exhibit inherent antifreezing properties and retain their mechanical integrity even at subzero temperatures for extended periods. Molecular dynamics (MD) simulations further reveal that the antifreezing behavior observed in the PEGn-EGINA-crosslinked hydrogels can be attributed to their highly hydrophilic and tightly crosslinked double-network structures. These structures enable strong bindings between water and the hydrogel network, thus effectively preventing the formation of ice crystals within the hydrogels. Notably, PEGn-EGINA-crosslinked hydrogels not only demonstrate superior mechanical performance compared to MBAA-crosslinked hydrogels, but also maintain their mechanical properties even in frozen conditions, making them suitable for a wide range of applications. This study presents a simple yet effective design concept for highlighting the role of novel crosslinker in enhancing antifreezing and mechanical properties, showcasing their potential for various applications that require both antifreezing capabilities and robust mechanical performance.

Cellulose eutecticgel electrolytes based on ethylene glycol/zinc chloride deep eutectic solvent for flexible solid-state capacitors

In the present work, we successfully prepared a conductive eutecticgel with good mechanical properties, adhesion properties and excellent antifreeze properties by mixing ethylene glycol (EG) as the hydrogen bonding donor and zinc chloride (ZnCl2) as the hydrogen bonding acceptor in different molar ratios to form an anhydrous deep eutectic solvent (DES). Water-soluble cellulose acetate (WSCA), monomer acrylamide (AM), initiator ammonium persulfate (APS) and cross-linking agent MBA (N, N′-methylene bis(acrylamide)) were added into the prepared DES to form a eutecticgel by a simple one-pot cooking strategy. The mechanical properties of the eutecticgel were strengthened by cross-linking of WSCA and PAM chains through hydrogen bonding, and the addition of the DES and ZnCl2 increased the freezing-resistant property of the eutecticgel. The stresses of DES-WSCA/PAM eutecticgel increased with the content of WSCA. The stress of DES-WSCA/PAM eutecticgel gradually becomes larger with the increase of WSCA content, and it can reach 184.07 kPa at 2 % WSCA content. In addition, the capacitor prepared by DES-WSCA/PAM eutecticgel shows excellent performance, with a voltage window of 2 V and a capacitance of 371.5 F/g, which can be operated stably for a long period, and the capacitance can still reach 145.4 F/g even under the condition of −40 °C. Moreover, DES-WSCA/PAM eutecticgel capacitor has a long service life, its capacitance retention rate and coulombic efficiency can reach more than 91 % and 95 %, respectively, after 10,000 times of charging and discharging tests. In summary, DES-WSCA/PAM eutecticgel electrolyte is an ideal material for capacitors, which opens up a new way of thinking for the development of multifunctional cellulose-based eutecticgels with low-temperature resistance, good mechanical properties, and non-irritating for wearable energy storage devices.

Multifunctional Organohydrogels for pH-Responsive Fluorescent and Electrostimulus Writing.

Hydrogels have attracted widespread attention in anticounterfeiting due to their unique physical/chemical properties and designability. However, hydrogels' poor mechanical properties and sluggish response to chemical stimuli pose challenges for their wide application. A fluorescent tough organohydrogel capable of freeform writing of information is reported in this work. By incorporation of the fluorescent monomer 7-methylacryloxy-4-methylcoumarin into the polyacrylamide network in a covalently cross-linked manner while intertwining with the carboxymethyl cellulose sodium network, a fluorescent tough organohydrogel with a dual-network structure is prepared. The organohydrogel shows acid-base-mediated adjustable fluorescence through the transformation of fluorescent monomers. Ion printing and electrical stimulation design achieved free information storage and encryption. In addition, the prepared organohydrogel has good antifreezing properties and can be encrypted and decrypted at subzero temperatures. The encrypted information in the organohydrogel can be read only after UV-light irradiation. These patterned fluorescent organohydrogels should find applications in protected message displays for improved information security.

Strong and Tough Antifreezing Hydrogel Sensor via the Synergy of Coordination and Hydrogen Bonds.

Hydrogel sensors are fascinating as flexible sensors and electronic skin due to their excellent biocompatibility and structure controllability. However, developing conductive hydrogels possessing both excellent mechanical and antifreezing properties for environmental-adaptive sensors remains a challenge. Herein, a strategy of combining betaine and metal ions to construct poly(acrylic acid) (PAA)-based high-conductive hydrogels has been reported. PAA-Al3+/betaine hydrogels with high toughness and antifreezing property were prepared by a one-step UV curing method. Their high toughness is attributed to the coordination of metal ions with the carboxylic groups in PAA, the interaction of betaine with PAA, and the formation of hydrogen bonds between them and water molecules. Moreover, the significant antifreezing property is due to the reduction of free water in the hydrogel. This, in turn, is attributed to the hydration of metal ions and the synergistic hydrogen bonding between betaine and water. The experiments demonstrate that the hydrogel has excellent mechanical property, high conductivity, superior transparency, antiswelling property, antipuncture as well as shape memory properties, and especially, low cytotoxicity. It can be used as a sensor for motion detection and information recognition. This work provides new insights into the application of flexible sensors and human-machine interfaces in multienvironmental conditions.

Cold storage alters the fat-trehalose trade-off, decreases the flight ability, and maintains the high survival rate and flight speed of Osmia excavata (Hymenoptera: Megachilidae).

Osmia solitary bees are important pollinators of various crops worldwide. Refrigeration has been widely used to synchronize the emergence time of Osmia species from cocoons with the blooming time of different crops, but the fitness of Osmia after refrigeration remains unknown. Here, the effects of long-term refrigeration at 0°C on the vitality, flight ability, and metabolism of Osmia excavata, which is known as the "king of pollination" in China, were studied. The survival rate (>90% before 120d), weight loss rate (<15% after 170d), and mean flight speed of O.excavata were not greatly affected after long-term refrigeration. The content of fats, which have antifreeze and energy storage properties, was not significantly altered in O.excavata before 130d of refrigeration, which might explain why the survival rates and flight speed of O.excavata remained high after long-term refrigeration. However, the flight duration and distance decreased significantly (P<0.05), and both were positively correlated with the reduced trehalose levels in O.excavata (r=[+0.69]-[+0.71]; P<0.05). Overall, these findings indicate that the pollination potential of O.excavata for various crops with different flowering periods is high after long-term refrigeration; however, long-term refrigeration may decrease pollination efficiency. Our findings highlight new research directions that could improve the ecological service function of refrigerated O.excavata.

Photocurable 3D printing high-strength gels for flexible wearable devices and surgical models

Hydrogels are considered to be ideal materials for the preparation of preoperative models and flexible wearable devices due to their softness and plasticity. However, there are still some problems in their application, such as how to achieve the construction of complex spatial structures through 3D printing and poor mechanical properties of the gel, especially poor tear resistance will greatly shorten the service life of hydrogels. In this study, with acrylamide (AM), stearyl methacrylate (SMA) and Multi-arm Crosslinking Agent (AGE-M) as the main raw materials, we provided a tear-resistance gel that can be photocurable for 3D printing. Through digital light processing (DLP)-based 3D printing, various gel-based preoperative models and devices with complex structures can be prepared. More importantly, the printed gel is endowed with excellent tear resistance by introducing the AGE-M as a nanoscale high-functionality crosslinker. In addition, the conductive substance sodium chloride is introduced to make the gel have a certain conductivity, and the organic solvent glycerol is introduced to replace part of the water to form a binary phase organic solvent, which endows the gel with excellent anti-drying and anti-freezing properties, to be suitable for more environments. Therefore, this work proposes a tear-resistance gel processed by DLP-based 3D printing technology, which can be used for the personalized manufacturing of organ models and flexible wearable devices, and is expected to be used in surgical training and artificial intelligence.

3D printable, stretchable, anti-freezing and rapid self-healing organogel-based sensors for human motion detection

Self-healing hydrogels have promising applications in sensors and wearable devices. However, self-healing hydrogels prepared with water as the dispersion medium inevitably freeze at sub-zero temperature, resulting in a loss of the self-healing and sensing ability. The black phosphorene / ethylene glycol / polyvinyl alcohol / sodium tetraborate / sodium alginate (BP/EG-SPB) organogels were prepared by 3D printing technology and solvent displacement method. The organogel exhibits high stretchability (1900 % strain), excellent self-healing property (25 s) and outstanding anti-freezing property (lower than −120 °C freezing point). Furthermore, the organogel can rapidly self-healed (150 s) at a low temperature (−80 °C) without any external stimulation. Additionally, this organogel-based flexible sensor possesses excellent sensitivity (gauge factor: 28.66 at 1900 % strain) and fast response capability, allowing for effective detection of human motion. This work provides a novel method for preparing multifunctional organogel-based sensors for use in harsh climates.

3D printable, anti-freezing, and rapid self-healing violet phosphorene incorporated hydrogel-based sensors for human motion detection

Conductive self-healing hydrogels, as an emerging flexible material, have been extensively studied in flexible sensors which have great application potential in the field of wearable electronic devices. However, hydrogels are prone to freezing at low temperatures, resulting in reduced or even lost flexibility, conductivity and self-healing properties. Besides, manufacturing method, processing time and cost of hydrogel-based sensors remain extremely challenging, hindering their application in complex and extreme environments. The hydrogel with excellent strain-sensing properties and outstanding anti-freezing properties was fabricated by 3D printing technology and solvent displacement method. The VP-SPB-EG hydrogel has excellent anti-freezing performance (−80 °C). In particular, this hydrogel exhibits excellent self-healing performance (120 s) at −80 °C. In addition, VP-SPB-EG hydrogel-based has high stretchability (1850 %) and sensitivity (GF: 27.82) can be used to detect strain changes caused by human joint movements. Therefore, this flexible hydrogel-based sensor has broad application prospects for wearable devices in extreme environments.

A full metal-free battery operating under cold condition enabled by an antisolvent

Metal-free batteries provide a more sustainable and environmental-friendly alternative to current popular batteries using nonrenewable metals. Alcohols as anti-solvents have been used in the electrolytes in Li-ion batteries (LIBs) and zinc-ion batteries (ZIBs), as they bring new properties with regards to the solvation sheath and water activity to the electrolytes. In this work, we explore the application of methanol (CH3OH) as an antisolvent in the electrolyte in a metal-free ammonium-ion battery (AIB) for operation at low temperature, with polyaniline (PANI) as anode and polypyrrole (PPy) as cathode. The addition of CH3OH alters the solvation sheath of the NH4+ and reduces the activity of H2O by forming hydrogen bonds in the solution, thereby decreasing the freezing point of the electrolyte. Through this strategy, a lower freezing point of the electrolyte is realized without using ultrahigh concentration of salts in aqueous solution. The resulted full metal-free battery using a 4 m ammonium acetate electrolyte is able to operate at -20°C, while long cycling at subzero temperatures has never been reported for ammonium-ion batteries before. Further, the CH3OH-H2O volume ratio can be optimized to 65-35, leading to an ammonium-ion battery that exhibits a capacity of 73.23, 48.32 and 32.88 mAh/g, as well as a capacity retention of 87.79%, 90.12% and 74.33% after 100 cycles at 0.1 A/g, at 25°C, 0°C and -20°C, respectively. In this work, an antisolvent is used in non-metal ammonium-ion batteries for the first time, engendering the battery anti-freezing properties. As such, this study opens the door to the realization of novel metal-free batteries with lower cost and better performance for applications in frigid environments.

Natural UCST hydrogel with long-term stability, recyclability, thermoplasticity, frost resistance and adhesive properties

Thermosensitive hydrogels have received great research interest, but the elaborate experimental design, inferior mechanical and anti-freeze properties have limited the practical application of thermosensitive hydrogels. For address these challenges, here, polyol (glycerol, xylitol, and sorbitol) and deionized water were selected as mixed solvents to fabricate multifunctional natural gelatin UCST hydrogels by simple physical blending. XRD and FT-IR indicate that the polyol assists the gelatin molecular chain to form short-range β-sheets without affecting the triple helix structure. The short-range β-sheets acts as the physical cross-linking point, which leads to a denser three-dimensional network of the hydrogel. The results indicate that the phase transition temperature and mechanical properties of UCST hydrogels can be modulated by simply changing the amount of polyol in the solvent mixture. In addition, the polyol forms extensive hydrogen bonds with water, which gives the hydrogel excellent freeze resistance, anti-drying and adhesive properties. In this paper, natural UCST gelatin hydrogels with long-term stability, recyclability, thermoplasticity, anti-freeze and adhesive properties were prepared by a simple scheme, and the facile process and cheap cost lays the foundation for the application of UCST hydrogels in drug delivery, skincare products and wearable devices.

3D Printable Organohydrogel with Long-Lasting Moisture and Extreme-Temperature Tolerance for Flexible Electronics.

Hydrogels with high electrical conductivity and mechanical stretchability are promising materials for flexible electronics. However, traditional hydrogels are applied in short-term usage at room temperature or low temperature due to their poor water-retention ability and freezing-tolerance property. Here, a dually cross-linked glycerol-organohydrogel (GL-organohydrogel) based on GL and acrylic acid was synthesized in a GL-water binary solvent. Fe3+ ions working as an electrolyte were added to improve the conductivity of the organohydrogel and form coordination interactions between Fe3+ ions and carboxyl groups of acrylic acid. The strong hydrogen bonding between GL and water molecules firmly lock water in the organohydrogel network, thereby endowing the GL-organohydrogel with the antifreezing property, long-term stability, and moisture lock-in capability. Our organohydrogel could endure extremely low temperature (-80 °C) over 30 days without freezing and retain its water content (almost 100% of its initial state) after being stored at room temperature (25 °C, 54% humidity) for 30 days. It also demonstrated desired stretchable properties, conductivity, three-dimensional (3D) printability, and self-healing ability. A wearable data glove was constructed by using the GL-organohydrogel and digital light processing technology. This work opens a new avenue for developing hydrogels with long-term stability, moisture lock-in capability, and extreme-temperature tolerance for stretchable electronics.

Highly Conductive, Anti-Freezing Hemicellulose-Based Hydrogels Prepared via Deep Eutectic Solvents and Their Applications.

Hydrogels containing renewable resources, such as hemicellulose, have received a lot of attention owing to their softness and electrical conductivity which could be applied in soft devices and wearable equipment. However, traditional hemicellulose-based hydrogels generally exhibit poor electrical conductivity and suffer from freezing at lower temperatures owing to the presence of a lot of water. In this study, we dissolved hemicellulose by employing deep eutectic solvents (DESs), which were prepared by mixing choline chloride and imidazole. In addition, hemicellulose-based DES hydrogels were fabricated via photo-initiated reactions of acrylamide and hemicellulose with N, N'-Methylenebisacrylamide as a crosslinking agent. The produced hydrogels demonstrated high electrical conductivity and anti-freezing properties. The conductivity of the hydrogels was 2.13 S/m at room temperature and 1.97 S/m at -29 °C. The hydrogel's freezing point was measured by differential scanning calorimetry (DSC) to be -47.78 °C. Furthermore, the hemicellulose-based DES hydrogels can function as a dependable and sensitive strain sensor for monitoring a variety of human activities.

Compressible, anti-freezing, and ionic conductive cellulose/polyacrylic acid composite hydrogel prepared via AlCl3/ZnCl2 aqueous system as solvent and catalyst

From the perspective of environmental sustainability, introducing cellulose into ionic conductive hydrogel is an inevitable trend for the development of flexible conductive materials. We report a double-network cellulose/polyacrylic acid (Cel/PAA) composite hydrogel based on the dissolving of cellulose by AlCl3/ZnCl2 aqueous system. The Cel/PAA composite hydrogel consists of rigid cellulose chains and flexible polyacrylic acid, which synergistically realize the improvement of the mechanical properties. The AlCl3/ZnCl2 aqueous system not only serves as the green solvent for cellulose, but also the Al3+ and Zn2+ metal ions can be served as a catalyst to activate the initiator for polymerization of acrylic acid. Compared with pure cellulose hydrogel, the compression strain of the Cel/PAA composite hydrogel was significantly improved to 80 %, and its conductivity increased by 28.1 %. In addition, its compression stress was enhanced over 2 times than pure PAA hydrogel. The Cel/PAA composite hydrogel exhibits excellent anti-freezing (−45 °C), weight retention (90 %), and conductivity (2.70 S/m) properties, still maintaining transparency and storage stability in the extreme environment. This work presents a facile strategy to develop an ionic conductive cellulose-based composite hydrogel with good conductivity and mechanical properties, which shows potential for the application fields of flexible sensors and 3D-printing functional materials.

Highly Stretchable, Transparent, and Adhesive Double-Network Hydrogel Dressings Tailored with Fish Gelatin and Glycyrrhizic Acid for Wound Healing.

It remains challenging to fabricate highly stretchable and adhesive hydrogel dressings for wound healing using simple, safe, and green methods. Herein, inspired by the main components of snail mucus, a fully physical double-network (DN) hydrogel dressing composed of fish gelatin (FGel) and glycyrrhizic acid (GL) was fabricated, in which FGel provided a protein scaffold to mimic snail mucus proteins, while GL mimicked the adhesion and bioactivity of snail mucus because of its abundant carboxyl and hydroxyl groups and intrinsic immunomodulatory activity. As expected, the obtained FGel/GL hydrogel dressings exhibited outstanding mechanical and adhesive performances (flexibility, stretchability, adhesive ability, and removability), high transparency, and good antifreezing properties. More importantly, they also possessed excellent biocompatibility, cell migration, and angiogenesis ability in vitro experiments. Finally, animal experiments in vivo indicated that the FGel/GL hydrogel dressings significantly promoted full-thickness wound healing, including promoting granulation tissue formation, collagen deposition, and skin angiogenesis and inhibiting the inflammatory response. All these findings indicated that the FGel/GL hydrogel dressings have great potential for applications in the clinical treatment of wound healing.

Hazardous Gases-Responsive Photonic Crystals Cryogenic Sensors Based on Antifreezing and Water Retention Hydrogels.

Nowadays, the sensing of hazardous gases is urgent for the consideration of public safety and human health, especially in extreme conditions of low temperatures. In this study, a photonic crystals (PhCs) sensor with water retention and antifreezing properties was developed and applied to visual hazardous gases sensing at low temperature, passively. The sensor was prepared by dip-coating with poly(methyl methacrylate) (PMMA) colloidal microspheres followed by embedding in k-carrageenan/polyacrylamide-ethylene glycol (k-CA/PAM-EG) hydrogel. The sensor responded to hazardous gases, including ammonia, toluene, xylene, acetone, methanol, ethanol, and 1-propanol, with a change in the reflection wavelength and visible structural color. At room temperature, the reflection wavelength of the sensor blue-shifted 49 nm in ammonia, and the structural color changed from red to yellow. For low temperatures, the sensor showed great water retention and antifreezing properties even at -57 °C due to the double network. The sensor still had a great response to hazardous gases after freezing at -20 °C for 12 h and testing at 0 °C, and the obtained results were similar to those at room temperature. Based on this excellent stability and visual sensing at low temperature, the sensor demonstrates the potential for detection of hazardous vapors in extreme environments.

Comparative genome analysis of the freshwater fungus Filosporella fistucella indicates potential for plant-litter degradation at cold temperatures.

Freshwater fungi play an important role in the decomposition of organic matter of leaf litter in rivers and streams. They also possess the necessary mechanisms to endure lower temperatures caused by habitat and weather variations. This includes the production of cold-active enzymes and antifreeze proteins. To better understand the physiological activities of freshwater fungi in their natural environment, different methods are being applied, and genome sequencing is one in the spotlight. In our study, we sequenced the first genome of the freshwater fungus Filosporella fistucella (45.7 Mb) and compared the genome with the evolutionary close-related species Tricladium varicosporioides (48.2 Mb). The genomes were annotated using the carbohydrate-active enzyme database where we then filtered for leaf-litter degradation-related enzymes (cellulase, hemicellulase, laccase, pectinase, cutinase, amylase, xylanase, and xyloglucanase). Those enzymes were analyzed for antifreeze properties using a machine-learning approach. We discovered that F. fistucella has more enzymes to participate in the breakdown of sugar, leaf, and wood than T. varicosporioides (855 and 719, respectively). Filosporella fistucella shows a larger set of enzymes capable of resisting cold temperatures than T. varicosporioides (75 and 66, respectively). Our findings indicate that in comparison with T. varicosporioides, F. fistucella has a greater capacity for aquatic growth, adaptability to freshwater environments, and resistance to low temperatures.

Enhancing Temperature Adaptability of Aqueous Zinc Batteries via Antifreezing Electrolyte and Site-Selective ZnSe-Ag Interface Layer Design.

Rechargeable aqueous zinc batteries (RAZBs) represent a sustainable, environmentally benign, cost-efficient energy storage solution for the scaled renewable power system. However, the cycling endurance and temperature adaptability of RAZBs are hindered by practical technological barriers such as the subzero freezing point of aqueous electrolyte, severe cation dissolution of the cathode, and dendrite growth on the Zn anode. Herein, we optimize the hybrid electrolyte formulation of 8 M ZnCl2 in the ethylene glycol-water mixed solvent to reconfigure the hydrogen bonding and [Zn(H2O)1.80(EG)0.23]2+ solvation sheath, which well balances the ionic conductivity and the antifreezing property until -125 °C. As monitored by operando X-ray diffraction, meanwhile, the structural dissolution of the V2O5 cathode upon the dynamic cycling and static idling storage at elevated temperature are effectively restrained. At the anode side, the thermally induced substitution between the Ag2Se overcoating and Zn foil in situ constructs the site-selective, mosaic interface layer, in which the solvophilic ZnSe facilitates the desolvation, while the Ag species provide zincophilic nucleation sites for high-throughput Zn deposition. The synergistic coupling of the antifreezing electrolyte and anode interfacial design enables the wide-temperature-range adaptability of the RAZB prototype (10 μm Zn foil and 1 mAh cm-2 V2O5 cathode), which balances the cycling endurance (92.5% capacity retention rate for 1000 cycles), 84.7% mitigation of the self-discharge rate at 55 °C, as well as the secured cyclability even at -40 °C.

Self-Healable, Adhesive, Anti-Drying, Freezing-Tolerant, and Transparent Conductive Organohydrogel as Flexible Strain Sensor, Triboelectric Nanogenerator, and Skin Barrier.

Conductive hydrogels have attracted tremendous interest in the construction of flexible strain sensors and triboelectric nanogenerators (TENGs) owing to their good stretchability and adjustable properties. Nevertheless, how to simultaneously achieve high transparency, self-healing, adhesion, antibacterial, anti-freezing, anti-drying, and biocompatibility properties through a simple method remains a challenge. Herein, a transparent, freezing-tolerant, and multifunctional organohydrogel (PAOAM-PDO) as electrode for strain sensors and TENGs was constructed through a free radical polymerization in the 1,3-propanediol (PDO)/water binary solvent system, in which oxide sodium alginate, aminated gelatin, acrylic acid, and AlCl3 were used as raw materials. The obtained PAOAM-PDO exhibited good transparency (>90%), self-healing, adhesiveness, antibacterial property, good conductivity (1.13 S/m), and long-term environmental stability. The introduction of PDO endowed PAOAM-PDO with freezing resistance with a low freezing point of -60 °C, and PAOAM-PDO could serve as a protective skin barrier to prevent frostbite at low temperature. PAOAM-PDO could be assembled as strain sensors to monitor heterogeneous human movements with high strain sensitivity (gauge factor of 7.05, strain = 233%). Meanwhile, PAOAM-PDO could be further fabricated as a TENG with a "sandwich" structure in single electrode mode. Moreover, the resulting TENG achieved electrical outputs with simple hand tapping and served as a self-powered device to light light-emitting diodes. This work displays a feasible strategy to build environment-tolerant and multifunctional organohydrogels, which possess potential applications in the wearable electronics and self-powered devices.

Designing ionophilic MXene-based organohydrogel electrolytes for high performance supercapacitor with wide-potential-window and anti-freezing properties

Supercapacitors based on organohydrogel electrolytes can function at subzero temperatures and demonstrate a large potential range. However, for the development of next-generation energy-storage technologies, improvements in the ionic conductivity, mechanical strength, and flexibility of organohydrogel electrolytes are required. We employed Ti3C2Tx, an ionophilic MXene, as a nanofiller in this study to improve the ionic conductivity of organohydrogel electrolytes. Strong affinity for Li+ ions and good dispersibility in water/glycerol were obtained by the hydroxyl group's abundance on the surface of the ionophilic MXene. Due to the enhanced Li-ion hopping through the plentiful hydroxyl groups, an antifreezing supercapacitor based on the MXene/poly(vinyl alcohol) organohydrogel electrolyte (MXPVA-OHE) displayed a gravimetric capacitance as high as 19.84 F g−1 at room temperature and 3.49 F g−1 at -20 °C. Due to their high ionic conductivity, wide potential window, and favorable post-freezing recyclability, MXPVA-OHE-based supercapacitors are thus excellent energy-storage devices.