Hydrophobic association and ionic coordination synergistically enhance a multifunctional hydrogel for high-performance wearable strain sensing

Flexible hydrogel-based strain sensors have attracted increasing attention for applications in wearable electronics and health monitoring due to their tissue-like mechanical properties and electrochemical responsiveness. However, most existing hydrogels suffer from mechanical brittleness, environmental instability, and humidity-sensitive conductivity, which limit their use in dynamic human motion detection. This study presents a high-performance flexible strain sensor based on PALCC hydrogel, which integrates hydrophobic association, ionic coordination, and deep eutectic solvent (DES) to enhance both mechanical and electrical properties. The hydrogel demonstrates exceptional mechanical strength (296.4 kPa), high elongation (434.6%), and stable electrical conductivity, making it ideal for wearable electronics and health monitoring applications. The synergistic interactions within the hydrogel network, including covalent bonding, ionic crosslinking, and hydrophobic associations, enable a two-stage linear strain response with outstanding durability (over 2000 cycles). Molecular dynamics simulations further elucidate the dynamic co-aggregation and strengthening mechanisms of the network. The sensor shows excellent dual-mode strain sensing under both tensile and compressive deformations, stable signal output for human motion and vocal vibration detection, and the capability to transmit information through Morse code via fingertip pressure. These results provide a promising solution for real-time health monitoring and wearable sensor applications, paving the way for future advancements in flexible strain-sensing technologies. Flexible hydrogel-based strain sensors have attracted increasing attention for applications in wearable electronics and health monitoring, but most existing hydrogels suffer from mechanical brittleness, environmental instability, and humidity-sensitive conductivity, which limit their use in dynamic human motion detection. Here, the authors present a flexible strain sensor based on a hydrogel that integrates hydrophobic association, ionic coordination, and deep eutectic solvents to achieve enhanced mechanical and electrical properties, demonstrating exceptional mechanical strength, high elongation, and stable electrical conductivity.