Hydrogel-based bimodal sensor array via modular assembly with decoupled strain–temperature sensing and high sensitivity

Bimodal flexible strain–temperature sensor arrays, capable of simultaneously detecting mechanical and thermal stimuli, show great potential in wearable electronics and human–machine interaction applications. However, existing hydrogel-based bimodal sensors commonly suffer from signal crosstalk, insufficient sensitivity, and poor structural reconfigurability. To address these challenges, this work proposes a modular “building-block” assembly strategy to construct a flexible multimodal hydrogel sensor array with effective strain–temperature signal decoupling and high sensitivity. The strain sensing units are composed of polyacrylamide/chitosan (PAM/CS) hydrogels, while the temperature sensing units are fabricated by sequentially coating chitosan (CS) and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) on polyacrylamide/sodium alginate (PAM/SA) hydrogels. Electrostatic interactions among CS, SA, and PEDOT:PSS ensure stable interfacial bonding, while Ca 2+ crosslinking enhances the rigidity of PAM/SA, inducing strain concentration in the PAM/CS region to achieve signal decoupling. The strain concentration effect significantly improves strain sensitivity with a gauge factor up to 8.82, and the constructed energy-filtering interface elevates the Seebeck coefficient to 128.59 μV/K, endowing the device with excellent temperature sensing performance (detection limits for strain and temperature difference are 0.1 % and 0.3 °C, respectively). Moreover, the hydrogel materials exhibit good cytocompatibility and hemocompatibility, further ensuring their safe integration into wearable systems. This sensor array is applicable in sign language recognition, intelligent password input, and other scenarios, demonstrating broad application prospects.