Facile Fabrication of Sodium Lignosulfonate Embedded Conductive Hydrogels toward Multifunctional Sensing and Supercapacitor Applications

Abstract The booming demand for high-performance wearable electronics has rendered multifunctional hydrogels highly promising candidates by virtue of their inherent high conductivity, excellent stretchability, and low cost. Herein, lignosulfonate sodium (LS) and ferric ions (Fe3+) undergo redox reactions to accelerate the ammonium persulfate (APS)-initiated copolymerization of acrylamide (AM) and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA), enabling rapid fabrication of LS/P(SBMA-co-AM) hydrogels. The optimized hydrogel (LS 10 wt %, SBMA 50 wt %, Fe3+ 0.32 wt % relative to AM) delivers a high ionic conductivity of 15.4 S/m, together with superior tensile performance: an elongation at break of 1160% and a tensile strength of 27.1 kPa. Moreover, the hydrogel maintains superior antifreezing properties, featuring an ultralow freezing point of −33.9 °C. When served as a strain sensor, it can realize real-time monitoring of human body movements with excellent cycling stability. For temperature sensing, the hydrogel possesses a high temperature coefficient of resistance across a broad temperature range and can accurately and stably detect human body temperature, demonstrating great suitability for wearable healthcare monitoring. Moreover, the assembled hydrogel-based supercapacitor delivers favorable electrochemical performance and can power LEDs even under subzero temperature conditions. Accordingly, the LS/P(SBMA-co-AM) hydrogel exhibits tremendous application potential for advanced flexible electronic devices.