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Binary solvent-based fabrication permits the conductive organohydrogel to function well at low-temperature environments. However, the deep cryogenic and high temperatures are still threatening the performance of conductive organohydrogels in the application of stretchable electronics, biosensors, and intelligent coatings. Here, a radically new method is developed to introduce propylene and carbonate cellulose nanofibrils into freeze tolerance polymer matrix, and fabricate an antifreezing/antiheating organohydrogel integrated a high mechanical strength (1.6 MPa) and high level of ionic conductivity (4.2 S cm -1 ) over a wide temperature range (-40 to 100 °C). In this designed system, the propylene carbonate with low freezing point and high boiling point was shown to enhance antifreezing (-40 °C) and antiheating (100 °C) performance of organohydrogel. Furthermore, negative charge-rich cellulose nanofibrils (CNFs) were served as an ion transport channel and nanoreinforcements to boost the conductive and mechanical properties of the organohydrogel. In particular, Molecular Dynamics (MD) simulations reveal that propylene carbonate with high dielectric constant is capable of generating ion migration-facilitated effects, enabling the high ionic conductivity of organohydrogel. Tapping into these attributes, potential applications in mechanoresponsive smart coating have been demonstrated utilizing the appealing organohydrogel as a paint, rendering unprecedented protection and monitoring performance., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Graphene aerogel (GA), with low density, high conductivity, and good mechanical properties, has important application potentials in the field of flexible electronics. Here, a balanced approach was developed in this work: Graphene oxide (GO) nanosheets were induced to assemble into a homogeneous porous hydrogel under alkali induction, and then, the oxygen-containing functional groups of GO were removed by reductant of formamidine sulfonic acid (FAS). Besides, the hydrogel of GA precursor can be quickly dried at a high temperature (150 °C) within 30 min to obtain pure GA of FGA. After further calcination, the obtained aerogel of AFGA with ordered structure has ultralow density (3.88 mg/cm3), high conductivity (7.4 S/m), supercompression recovery performance (99%), high sensitivity (S = 0.83 kPa−1), large reversible compression cycle performance (200 cycles under 90% strain), and high fatigue resistance (10,000 cycles under 70% strain), which presents excellent piezoresistive properties and can find wide applications in piezoresistive sensors as the high-performance sensing material. [ABSTRACT FROM AUTHOR]

Conductive hydrogels with high flexibility, superior formability, good mechanical elasticity, and excellent biocompatibility have emerged as promising materials for broad applications in flexible/wearable electronic devices. In this work, a conductive dual‐network PVA/SA/MXene hydrogel (PSM‐h) composed of polyvinyl alcohol, sodium alginate, and MXene (Ti3C2Tx) is constructed by a green method without using chemical crosslinking agents. The resultant hydrogel with dual‐network feature shows excellent cytocompatibility (no toxicity for human umbilical cord mesenchymal stem cells), high stretchability (up to 263%), and superior anti‐fatigue ability (stretched up to 1000 cycles). More importantly, PSM‐h based strain sensor presents good sensing sensitivity with a fast response time (62.5 ms) and a low detection limit even under a very slight strain of 0.2%. In terms of the practical application, the PSM‐h based strain sensor can be applied to detect and distinguish various human motions. [ABSTRACT FROM AUTHOR]

With the popularization of intelligent terminals and the improvement of medical level, the development of flexible wearable electronic devices (FWEDs) with high sensitivity and excellent mechanical properties plays a vital role in human motion and health monitoring. But most of FWEDs still stuck in a difficult choice of mechanical, functional, and sensory properties. In this work, it is found a strategy for extricating such plight. Using zwitterionic and quaternary ammonium salt, a novel polycationic hydrogel [P(ImSL‐AmC)] with excellent performance is synthesized by copolymerization under photoinitiation. After optimizing conditions of synthesis, its structure and properties are characterized. It is found that the electrostatic interaction enhances the mechanical applicability of P(ImSL‐AmC), which combines high stretchability (≈500% strain) with perfect strength (≈900 kPa) successfully. It is exciting that P(ImSL‐AmC) not only exhibits excellent antibacterial activities against both E. coli and S. aureus, but also maintains transparency and flexibility at −10 °C. This polycationic hydrogel also has superior conductivity as a stretchable pressure‐strain sensor, which can accurately monitor human motion. In summary, the obtained polycationic hydrogel possesses excellent combination functions, including intelligent conductivity, mechanical adaptability, antibacterial, frost resistance, and transparency. Furthermore, the practical strategy can be applied in preparation of intelligent wearable devices and human–computer interaction. [ABSTRACT FROM AUTHOR]

Wearable flexible sensors face many harsh environments in practical applications. However, developing corrosion-resistant conductive hydrogel-based flexible sensing materials for applications under harsh conditions remains a formidable challenge because significant damages are caused by the inevitable solvent corrosion on the polymer network structure. Here, a novel conductive hydrogel with superior chemical stability and stretchability was intelligently designed and successfully fabricated by introducing a small amount of N,N′-methylenebis(acrylamide) (BIS) and graphene oxide (GO) as chemical and physical crosslinking agents into the polymer interpenetrating network formed by poly(N-isopropylacrylamide) (PNIPAM) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Benefiting from the introduction of strong chemical bonds and GO nanosheets, the synthesized conductive hydrogel exhibited swelling resistance to strong alkali/polar solvents and surprising chemical structure stability to all solvents. Interestingly, the hydrogel-based sensor could even achieve an accurate and a stable mechanical sensing of tensile strain in a variety of solvents. Furthermore, the hydrogel sensor is featured by strong adhesion, high reliability, and wide sensing ranges for detecting and distinguishing various human motions. Therefore, such design strategy greatly extends the application range of conductive hydrogels in flexible electronic devices and shows great potential in the applications of electronic skins and soft robots in harsh environments (especially in various solvents). [ABSTRACT FROM AUTHOR]

Avoiding wound infection and retaining an appropriate level of moisture around woundz are major challenges in wound care management. Therefore, designing hydrogels with desired antibacterial performance and good water-maintaining ability is of particular significance to promote the development of wound dressing. Thus a series of hydrogels are prepared by crosslinking of Ag/graphene composites with acrylic acid and N, N′-methylene bisacrylamide at different mass ratios. The antibacterial performance and accelerated wound-healing ability of hydrogel are systematically evaluated with the aim of attaining a novel and effective wound dressing. The as-prepared hydrogel with the optimal Ag to graphene mass ratio of 5:1 (Ag5G1) exhibits stronger antibacterial abilities than other hydrogels. Meanwhile, Ag5G1 hydrogel exhibits excellent biocompatibility, high swelling ratio, and good extensibility. More importantly, in vivo experiments indicate that Ag5G1 hydrogel can significantly accelerate the healing rate of artificial wounds in rats, and histological examination reveals that it helps to successfully reconstruct intact and thickened epidermis during 15 day of healing of impaired wounds. In one word, the present approach can shed new light on designing of antibacterial material like Ag/graphene composite hydrogel with promising applications in wound dressing. [ABSTRACT FROM AUTHOR]

In this study, a polydopamine (PDA)-modified MXene-PNIPAM (pMP) hydrogel is prepared using a soap-free emulsion polymerization method, which shows enhanced anti-oxidative, photo-thermal, and tribological properties. The introduction of PDA not only inhibits the oxidation of MXene but also enhances the photo-thermal conversion efficiency of the hydrogel. Even after 50 days, it can still maintain good photo-thermal conversion performance. Moreover, compared with PNIPAM hydrogel, the friction coefficient (COF) and wear volume of pMP hydrogel as lubricant were reduced by 33% and 85%, respectively. Interestingly, the control of COF with excellent reversibility and durability is achieved using pMP hydrogel modulated by near-infrared light. The pMP composite hydrogel exhibits promising prospects in the fields of intelligent robots and biomedical devices. [Display omitted] • pMP hydrogel with excellent photothermal conversion performance was designed and prepared. • Polydopamine can significantly enhance the oxidation resistance of pMP hydrogel. • pMP exhibits reversible NIR light active modulation capabilities for friction control. • The method and materials developed in this work have broad application prospects in smart materials and intelligent devices. [ABSTRACT FROM AUTHOR]

Inspired by the phenomenon of cell dehydration in electrolyte solutions, a simple salting out method was performed to fabricate controllable water releasing hydrogels, achieving solid–liquid composite lubrication within a single material. [Display omitted] • MXene/PVA hydrogel with controllable water release was prepared by salting out. • The salt out effect induced densification of the hydrogel structure and water release. • The structure and properties of MXene/PVA hydrogel were significantly strengthened. • The hydrogel achieved solid–liquid composite lubrication within a single material. Due to the unique synergistic lubrication mechanisms, solid–liquid composite lubrication has received widespread attention in tribology. However, the cumbersome preparation process and solid–liquid separated service conditions limit its practical application. Inspired by the phenomenon of cell dehydration in electrolyte solutions, a simple salting out method is employed to develop multi-crosslinked and salted out MXene/polyvinyl alcohol (PVA) (MS-MP) hydrogels that can release water controllably for achieving solid–liquid composite lubrication in a single material. In this work, zinc ions (Zn2+) with both multi-crosslinking effect and salting out effect are incorporated into MXene/PVA hydrogels. These effects not only induce the formation of crystalline domains and the strengthening of network structure of hydrogels, but also release the water in hydrogels to realize the solid–liquid composite lubrication. Furthermore, the structure and tribological properties of MS-MP hydrogels can be regulated by adjusting the salting out degree, resulting in the acquisition of a structurally stable hydrogel with exceptional load-bearing capacity and superior lubrication performance. In brief, this work provides a novel and simple strategy for the fabrication of solid–liquid composite lubricating hydrogels, which shows great potential in fabricating liquid-containing lubrication materials. [ABSTRACT FROM AUTHOR]