A\nMultifunctional, Self-Healing, Self-Adhesive, and\nConductive Sodium Alginate/Poly(vinyl alcohol) Composite Hydrogel\nas a Flexible Strain Sensor

Abstract

Hydrogel-based\nwearable devices have attracted tremendous interest\ndue to their potential applications in electronic skins, soft robotics,\nand sensors. However, it is still a challenge for hydrogel-based wearable\ndevices to be integrated with high conductivity, a self-healing ability,\nremoldability, self-adhesiveness, good mechanical strength and high\nstretchability, good biocompatibility, and stimulus-responsiveness.\nHerein, multifunctional conductive composite hydrogels were fabricated\nby a simple one-pot method based on poly­(vinyl alcohol) (PVA), sodium\nalginate (SA), and tannic acid (TA) using borax as a cross-linker.\nThe composite hydrogel network was built by borate ester bonds and\nhydrogen bonds. The obtained hydrogel exhibited pH- and sugar-responsiveness,\nhigh stretchability (780% strain), and fast self-healing performance\nwith healing efficiency (HE) as high as 93.56% without any external\nstimulus. Additionally, the hydrogel displayed considerable conductive\nbehavior and stable changes of resistance with high sensitivity (gauge\nfactor (GF) = 15.98 at a strain of 780%). The hydrogel was further\napplied as a strain sensor for monitoring large and tiny human motions\nwith durable stability. Significantly, the healed hydrogel also showed\ngood sensing behavior. This work broadens the avenue for the design\nand preparation of biocompatible polymer-based hydrogels to promote\nthe application of hydrogel sensors with comfortable wearing feel\nand high sensitivity.