Ultrafast self-healing zwitterionic hydrogels reinforced by carboxymethyl chitosan-oxidized hyaluronic acid and graphene oxide toward high-performance strain sensors.

Inspired by the inherent recuperative ability of organisms in nature, researchers have dedicated significant efforts towards developing self-healing hydrogel sensors. Although the works on self-healing hydrogels have made great progress, achieving hydrogel sensors combining with rapid and efficient healing capability, excellent mechanical properties and high sensing sensitivity remains a challenging task. In this study, we proposed a novel approach for fabricating a self-healing conductive zwitterionic hydrogel sensor by adding carboxymethyl chitosan (CMCs) and oxidized hyaluronic acid (OHA) to induce dynamic Schiff base reaction, and graphene oxide (GO) nanosheets as physical crosslinker. This zwitterionic hydrogel exhibited a high tensile strength of 133 kPa and elongation at break of 878 %. By leveraging various dynamic interactions within the system, the hydrogel exhibited ultra-fast and efficient healing property, achieving a self-healing efficiency of 98.9 % within just 15 min. The hydrogel demonstrated exceptional adhesion to diverse substrates especially to glass with a maximum adhesion strength reaching up to 53.7 kPa. The hydrogel exhibited a high gauge factor (GF) value of 23.2, which showed clear and stable monitoring and sensing capabilities across various human movements ranging from swallowing to bending knees. Notably, the hydrogel could also be employed as a Morse code transmitter and flexible tablet. The zwitterionic hydrogel demonstrates its great potential applications in the field of high-performance flexible sensors as well as human-computer interaction.