Flexible fabric-integrated PAAm–LiCl hydrogel pressure sensor for wearable and soft robotics applications

Abstract

This work presents the successful development of a flexible, fabric-integrated pressure sensor based on a woven cotton substrate and a polyacrylamide–LiCl (PAAm–LiCl) plain ionic hydrogel, synthesized via free-radical polymerization. The composite sensor was fabricated by uniformly coating the hydrogel onto woven fabric electrodes, forming an ionic conductive network capable of capacitive pressure sensing. A comprehensive series of characterizations confirmed the performance of the sensor and material integrity. Scanning electron microscopy (SEM) revealed a densely microporous surface structure that promotes enhanced ion transport. Fourier transform infrared (FTIR) spectroscopy confirmed the presence of characteristic O–H, CO, and C–O functional groups, indicating hydrogen bonding, water retention, and the integration of polyacrylamide and cellulose components. Thermogravimetric analysis (TGA) demonstrated excellent thermal stability with major decomposition occurring at elevated temperatures, validating the robustness of the composite under thermal stress. Mechanical testing confirmed the strong self-adhesive properties of the material across diverse substrates, thereby improving its versatility for integration in practical applications. The pressure-sensing performance was validated through sensitivity analysis, dynamic and static gradient pressure response, frequency response under cyclic loading, and durability testing over 10 000 cycles. The sensor displayed rapid response and repeatability under varying pressure and frequency conditions, confirming its reliability and long-term functionality. These results collectively demonstrate the effective synthesis and integration of PAAm–LiCl hydrogel with woven fabric, leading to a stable, sensitive, and thermally durable pressure sensor. The developed system holds significant potential for use in wearable electronics, soft robotics, healthcare monitoring, and interactive human–machine interface technologies.