Physically crosslinked polyvinyl alcohol/chitosan-phytic acid hydrogels for wearable sensors with highly conductive, recyclable and antibacterial properties

Conductive hydrogels as wearable sensors meet the basic requirements of mechanical flexibility and intelligent sensing. However, they are often hampered by problems such as the incompatibility between favorable mechanical properties and high conductivity, inferior antimicrobial ability and difficulty in recycling. Herein, highly conductive and physically cross-linked polyvinyl alcohol/chitosan-phytic acid (PVA/CS-PA) hydrogels were developed by a facile freeze-thaw method. The hydrogen bonding and electrostatic interaction between PA and matrix of CS and PVA endow hydrogels with not only moderate mechanical properties and high degree of ductility, but also meaningfully recyclable characteristics. In addition, the hydrogel exhibits superior conductivity (~0.125 S cm−1) and antimicrobial activity, benefiting from the ionic conductivity and antibacterial capacity of PA molecules. These exceptional properties enable the hydrogel-based wearable sensors to exhibit strain-sensitive properties (a gauge factor of 7.21 under strains of 200%–420%), which could monitor various activities of human body. More interestingly, the PVA/CS-PA sol ink could be transformed into a gel state in an ice bath, which would meet the need of flexible circuit and make wearable sensors more portable.