Multifunctional hydrogel with outstanding conductivity and mechanical flexibility has received enormous attention as wearable electronic devices. However, fabricating transparent, ultrastretchable, and biocompatible hydrogel with lowtemperature stability still remains a tremendous challenge. In this study, an ultrastretchable, highly transparent, and antifreezing zwitterionic-based electronic sensor is developed by introducing zwitterionic proline (ZP) into gellan gum/polyacrylamide (GG/ PAAm) double network (DN) hydrogel. The existence of ZP endows the hydrogel with remarkable frost resistance. The toughness and transparency of zwitterionic Ca-GG/PAAm-ZP DN hydrogel can be maintained down to −40 °C. Also, the zwitterionic hydrogel shows good biocompatibility and protein adsorption resistance. The zwitterionic Ca-GG/PAAm-ZP DN hydrogel-based strain sensor can accurately monitor human motions (such as speaking and various joint bendings) under a broad temperature range from −40 to 25 °C. The zwitterionic Ca-GG/PAAm-ZP DN hydrogel-based strain sensor will be of immense value in the field of wearable electronic devices, especially for extreme environment applications.

Strong mechanical performance, appropriate adhesion capacity, and excellent biocompatibility of conductive hydrogel-based sensors are of great significance for their application. However, conventional conductive hydrogels usually exhibit insufficient mechanical strength and adhesion. In addition, they will lose flexibility and conductivity under subzero temperature and a dry environment owing to inevitable freezing and evaporation of water. In this study, a tough, flexible, self-adhesive, long-term moisturizing, and antifreezing organohydrogel was prepared, which was composed of gelatin, zwitterionic poly [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) (PSBMA), MXene nanosheets, and glycerol. Natural gelatin was incorporated to enhance mechanical performance via the entanglement of a physical cross-linked network and a PSBMA network, which was also used as a stabilizer to disperse MXene into the organohydrogel. Zwitterionic PSBMA endowed the organohydrogel with good adhesion and self-healing properties. Long-term moisturizing properties and antifreeze tolerance could be achieved owing to the synergistic water retention capacity of PSBMA and glycerol. The resulting PSBMA–gelatin–MXene–glycerol (PGMG) organohydrogel exhibited high mechanical fracture strength (0.65 MPa) and stretchability (over 1000%), excellent toughness (3.87 MJ/m3), strong and repeated adhesion to diverse substrates (e.g., paper, glass, silicon rubber, iron, and pig skin), good fatigue resistance (under the cyclic stretching–releasing process), and rapid recovery capacity. Moreover, the PGMG organohydrogel showed good stability under −40 °C. The sensor based on PGMG organohydrogel could tightly attach to the human skin and real-time-monitor the motions of joints (e.g., bending of the finger, wrist, elbow, and knee) and the change in mood such as smiling and frowning. Therefore, PGMG organohydrogels have a huge potential for wearable sensors under room temperature or extreme environments.

Hydrogels as wound dressings have received great attention in recent years. It is highly important yet challenging to develop hydrogel dressings that are biocompatible and that can promote wound healing by lowering the risk of inflammatory responses. In this work, we designed and prepared zwitterionic dextran-based hydrogels using carboxybetaine dextran (CB-Dex) and sulfobetaine dextran (SB-Dex) as raw materials, respectively. The efficacy of CB-Dex and SB-Dex hydrogels in promoting wound recovery was evaluated using a mouse skin wound model. Results suggested that the zwitterionic dextran wound dressings showed a faster healing rate than natural dextran hydrogel and a commercial wound dressing (Duoderm film) due to their excellent protein resistance and capacity to scavenge free hydroxyl radicals. In addition, both CB-Dex and SB-Dex hydrogel wound dressings showed excellent cytocompatibility with NIH3T3 and L929 cells, as well as antibacterial adhesion against Staphylococcus aureus and Escherichia coli. Furthermore, both zwitterionic hydrogels demonstrated self-healing properties and can be stretched to adapt to irregular full-thickness wound beds. More importantly, they can be removed from the wound site painlessly by washing with normal saline. Overall, this work provided a new pathway to fabricate multifunctional polysaccharide hydrogels for wound treatment and pain relief when changing wound dressings.

Forming natural polymers‐based hydrogels with enhanced mechanical strength, outstanding antifreezing property and superior conductivity is still a challenge. Here, gelatin/oxidized dextran hydrogel is fabricated and it shows enhanced mechanical performance, antifreeze tolerance, and conductivity due to the synergistic interaction of ammonium sulfate and betaine. The resulting gelatin/oxidized dextran/(NH4)2SO4/betaine hydrogel exhibits high stretchability (570%), tough tensile (2.49 MPa) and compressive (46.41 MPa) fracture strength, favorable tensile (6.05 MJ m−3) and compressive (3.08 MJ m−3) toughness, antifreezing property (−30 °C) and high conductivity (2.86 S m−1). Based on the above characteristics, the hydrogel is applied for strain sensor to monitor the joints motion of human body such as finger, wrist, elbow, knee, neck, and throat. The hydrogel can maintain good mechanical performance and stable sensing signal from 25 to −30 °C. Therefore, the designed hydrogel based on natural polymers shows a huge potential for tissue engineering and biosensing under the mild or extreme environment.

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