Rational design of antifreeze and flexible chitosan-based hydrogels for integration device of supercapacitors electrodes and wearable strain sensors

Hydrogels with excellent flexibility are widely used in flexible sensors and supercapacitors, but their sensitivity and operating temperature range limit their application. In this study, chitosan (CS)/polyaniline (PANI) hydrogel with interpenetrating network structure is designed, in which phytic acid is used as crosslinking agent and antifreeze. The obtained CS/PANI hydrogel exhibits excellent mechanical properties, excellent sensing performance (Gauge Factor = 5.25), fast electrochemical response, high specific capacitance (383.7 F/g at 0.5 A/g) and good cycle stability, which may be due to the interpenetrating network structure formed between phytic acid cross-linked PANI and CS molecular chains. Due to these properties, CS/PANI hydrogels can be used as flexible sensors and supercapacitor electrodes materials. Because of the electrostatic interaction between the anionic and cationic groups in phytic acid, it also has certain frost resistance. The CS/PANI hydrogel can provide a high specific capacitance of 330 F/g at -40 degrees C. Compared with room temperature, the capacitance retention rate is as high as 87 %. It is believed that this CS/PANI hydrogel will be used as a new multifunctional material in many fields such as flexible electrodes, sensors and wearable devices in low temperature environments.