Wireless Strain Sensors Based on Sustainable Poly(lipoic acid) Zwitterionic Conductive Biogels with Self-Healing, High Stretchability, and Biodegradability

Abstract

Recently, sustainable poly(lipoic acid) (poly(LA))-based biogels have attracted increasing interest and have been used in wearable sensing fields. However, the low stretchability and adhesion, poor self-healing, and wire transmission remain the major issues that limit the applications of poly(LA)-based gel sensors. It is urgent to develop multifunctional biogels with excellent comprehensive performance. In this work, multifunctional conductive poly(LA)-based zwitterionic biogels (denoted as PLLS gels) were fabricated by introducing hydrophilic sulfobetaine methacrylate (SBMA) through nucleophilic addition reactions with poly(LA). The addition of SBMA endowed the gels with conductivity due to the abundant anionic and cationic groups of the zwitterionic structure. The excellent biocompatibility of poly(LA) and SBMA provided the gels nontoxicity and harmlessness. As expected, the PLLS gels possessed high stretchability, adhesion, and self-healing due to the multiple dynamic bonds, including hydrogen bonds and electrostatic interactions. Besides, the gels exhibited excellent biodegradability, antioxidant, and antibacterial activities. The PLLS gels had found application as a wireless wearable sensor, which could monitor various human activities involving temperature changes, human joint movements, and voice recognition. This work not only provides a valuable strategy for constructing the sustainable gel sensors but also expands the applications of biogels to portable mobile monitoring of wireless wearable devices.