A double-dynamic-bond crosslinked multifunctional conductive hydrogel with self-adhesive, remoldability, and rapid self-healing properties for wearable sensing

In recent years, conductive hydrogels have been designed as flexible sensors with broad application prospects in the field of smart wearable devices. However, the coordination of the mechanical properties, self-healing capability, and conductivity of hydrogels has always been a challenge. In this work, a multifunctional conductive hydrogel with self-adhesive, re-shapeable, and rapid self-healing abilities (PB-PACS-PM3 (self-healing efficiency) = 98.8% in 15 s) was prepared by incorporating protocatechualdehyde modified carboxymethyl chitosan (PA@o-CMCS) and PDA-modified MXene (PDA@MXene) into the interchain of polyvinyl alcohol through dynamic borate ester crosslinking. The dynamic Schiff base reaction not only effectively introduced o-CMCS as a mechanical enhancer but also improved the viscoelasticity and self-healing capability of the hydrogel through the dual dynamic bond crosslinking structure. The PDA@MXene nanosheets are uniformly distributed in the hydrogel, providing the composite system with excellent conductivity (the conductivity of PB-PACS-PM3 hydrogel is 1.5 S/m) and strain sensitivity (the response time and recovery time of the hydrogel sensor are 230 and 260 ms, respectively), while the tensile strength of the hydrogel is improved to 0.035 MPa. Due to all these advantages, this conductive hydrogel can be assembled into flexible wearable sensors for rapid and accurate monitoring of various physiological activities of the human body, such as finger, wrist, elbow, and knee bending vibrations, among others.