Long-Term Durable and Ultrasensitive Multiple-Crosslinked Ionic Hydrogel Sensors with Multi-Functions for Wearable Electronics

Hydrogels are considered promising for wearable devices because they are soft, flexible, stretchable, and biocompatible. However, existing hydrogels suffer from poor strength, weak and one-time adhesion, non-self-recovery, water evaporation, ice crystallization, and low sensitivity, and these problems have been only partly solved previously. We propose the one-pot synthesis of a multiple-crosslinked poly(2-(methacryloyloxy)ethyl)dimethyl-(3-sulfopropyl)ammonium hydroxide-co-acrylamide (P(SBMA-co-AAm) multifunctional hydrogel to overcome these limitations. The synthetic route provided elasticity, self-healing, and transparency, and the incorporation of glycerol and NaCl ions provided moisture stability (e.g., water retention) and antifreeze properties. Zwitterionic SBMA contributed to the increased gauge factor, resulting in high sensitivity and an ability to detect human movements at a strain of 800%–1600%, making the hydrogel sensor practical. The sensor retained its properties after even 300 cycles, indicating its durability and reliability for long-term applications.