Multifunctional hybrid hydrogel with transparency, conductivity, and self-adhesion for soft sensors using hemicellulose-decorated polypyrrole as a conductive matrix

Polymers with high conductivity and cross-linking ability are ideal materials for the preparation of conductive hydrogels for application in wearable electronic devices. However, the fabrication of conductive polymer-incorporated hydrogels with good synergistic properties remains a great challenge due to the hydrophobicity and opacity of conjugated π conductive polymers. In this study, a multifunctional hybrid hydrogel was prepared by incorporating hemicellulose-decorated polypyrrole (H/PPY), polyvinyl alcohol (PVA), and tannic acid (TA) into a polyacrylamide (PAM) network. The addition of excess ammonium persulfate (APS) in the process of gelation not only initiated the polymerization of PAM but also resulted in the change of the hydrogel from opaque to transparent by continuously breaking and reducing the size of the PPY particles. The hybrid hydrogel exhibited high transparency and conductivity, good adhesion ability and mechanical performance, and high resistance strain sensitivity and could accurately monitor the strain signals of the index finger and elbow flexion and pulse beat during rest and exercise, which has promising potential for use in wearable or implantable smart sensor devices, electronic skins, and artificial intelligence applications.