Antifreezing, Ionically Conductive, Transparent, and Antidrying Carboxymethyl Chitosan Self-Healing Hydrogels as Multifunctional Sensors

Abstract

Through a simple strategy of immersion in a mixed solution of water/ethylene glycol (EG)/lithium chloride (LiCl), self-healing carboxymethyl chitosan (CA) hydrogels, that is, CA/N-vinylpyrrolidone-EG-Li+ hydrogels (CEH) with an ultra-low-temperature freezing resistance below −70 °C were fabricated. The introduction of electrolyte ions and small-molecule polyol also made these hydrogels highly conductive (0.8 S m–1) and imparted antidrying property to them, showing stable and reversible sensitivity to finger-wrist bending as well as 150 cycles of stretching. Such hydrogels also presented highly efficient self-healing ability, with a stress–strain healing efficiency of over 90%. Furthermore, the CEH-based sensors maintained a stable sensing performance over a wide range of temperatures below the freezing point (from −10 to −70 °C) and exhibited stable sensitivity to temperatures with fast response and no significant hysteresis. The present work is expected to provide a simple and sustainable route for the preparation of multifunctional antifreezing conductive hydrogels based on CA, leading to a wide range of potential applications in soft sensor devices.

High Mechanical Strength and Multifunctional Microphase‐Separated Supramolecular Hydrogels Fabricated by Liquid‐Crystalline Block Copolymer

“…The crystallization domain expanded with the increase of Azobenzene content, then the rigidity of P(AM-G)-b-PAzo hydrogels was enhanced, which strengthen the fracture strength and weaken the fracture elongation [47] (Figure 2f). P(AM-G)-b-PAzo 15 [8] hydrogel, [35] P-HP hydrogel, [48] PAM-CS-A hydrogel, [13] DFT hydrogel, [49] Tetra-PVA hydrogel, [50] 𝛽CD-VC hydrogel, [51] APVA/HTCC hydrogel, [52] CNH hydrogel [53] ).…”

“…d) Comparison chart by plotting the fatigue thresholds versus self-healing among tough hydrogels. (i.e., CS/CB[8] hydrogel,[35] P-HP hydrogel,[48] PAM-CS-A hydrogel,[13] DFT hydrogel,[49] Tetra-PVA hydrogel,[50] 𝛽CD-VC hydrogel,[51] APVA/HTCC hydrogel,[52] CNH hydrogel[53] ).…”

Self-healable and freeze-resistant polyelectrolyte based on an EG anchor chain and dual dynamic reversible interaction as highly sensitive ionic skin

“…[1][2][3][4][5][6][7] However, currently, wearable devices, such as smart watches, intelligent glasses, sports monitoring wristbands and bracelets, cannot tightly fit surfaces with different geometries or topologies, which is inconsistent with user-friendly design. [8][9][10] In this case, electronic and ionic skin can imitate natural skin sensing functions, converting diverse inputs such as strain, pressure, and temperature into electrical impulses, and they also conform closely to the human skin, making them a significant component in next-generation wearable electronics. 11 Generally, electronic skins are fabricated by dispersing conductive components such as carbon nanotubes, graphene, and metal nanowires in soft elastomeric matrices.…”

A highly stretchable and sensitive carboxymethyl chitosan-based hydrogel for flexible strain sensors

“…17 Unfortunately, most CMCS-based hydrogels have reported poor mechanical properties (B200 kPa) in recent years and cannot satisfy the requirements of long-term cyclic stretching. 18,19 In addition, CMSC-based hydrogels do not usually possess self-healing abilities due to the presence of irreversible covalent bonds. After numerous cycles of repeated stretching, the hydrogel deforms and has difficulty returning to its original shape.…”