Temperature-sensitive and solvent-resistance hydrogel sensor for ambulatory signal acquisition in “moist/hot environment”

To realize continuously and stably work in a “moist/hot environment”, flexible electronics with excellent humid resistance, anti-swelling, and detection sensitivity are demanding. Herein, a solvent-resistant and temperature-ultrasensitive hydrogel sensor was prepared by combining MXene and quaternized chitosan (QCS) with the binary polymer chain. The strong electrostatic interaction between the QCS chain and the poly(acrylic acid) (PAA) network endows the hydrogel stability against solvent erosion, high temperature, and high humidity. The strong dynamic interaction between MXene and polymer matrix significantly improves the mechanical properties and sensing (strain and temperature) sensitivity of the hydrogel. The hydrogel strain sensor exhibits a high gauge factor (5.53), temperature/humidity tolerance (equilibrium swelling ratio of 2.5% at 80 °C), and excellent cycle stability, which could achieve a remote and accurate perception of complex human motion and environment fluctuation under aquatic conditions. Moreover, the hydrogel sensor exhibits impressive thermal response sensitivity (−3.183%/°C), ultra-short response time (< 2.53 s), and a low detection limit (< 0.5 °C) in a wide temperature range, which is applied as an indicator of the body surface and ambient temperature. In short, this study broadens the application scenarios of hydrogels in persistent extreme thermal and wet environments.