Self-Adhesive, Antifreezing, and Antidrying Conductive Glycerin/Polyacrylamide/Chitosan Quaternary Ammonium Salt Composite Hydrogel as a Flexible Strain Sensor

Abstract

Conductive hydrogels, a type of intrinsically flexible and conductive materials, are frequently employed in soft electronics. However, because water-based hydrogels can easily freeze and dry, their long-term stability is considerably limited. Herein, a glycerol (Gly)–water binary antifreezing and antidrying hydrogel was prepared by using glycine with water as a solvent, followed by the introduction of cationic polysaccharide chitosan quaternary ammonium salts into the covalently cross-linked polyacrylamide network and addition of NaCl ions to adjust the ionic conductivity of the hydrogel. In a broad temperature range, the produced hydrogel was used for tensile and sensitive strain sensing. Because strong hydrogen bonds between Gly and water molecules are easily established, the resultant organohydrogels have good freezing and drying endurance, retaining long-term deformation even at negative temperatures. Moreover, the hydrogel exhibits good adhesion and tensile properties because of the addition of chitosan quaternary ammonium salts. At the same time, strain sensors fabricated using the hydrogel exhibit a wide operating strain range (≈1000%) and good sensitivity, stability, and repeatability, making them promising candidates for building gel-based strain sensor platforms.