Silicone Ionic Liquid-Based Hydrogel for Flexible Strain Sensors with Intrinsically Antifreezing Property

Abstract

Conductive hydrogels are garnering increased attention for their application in flexible strain sensors due to their distinctive inherent excellent properties. However, the high water content leads to inadequate antifreezing capability, severely restricting their application in cold environments. Here, an interpenetrating dual-network hydrogel with intrinsic antifreezing property was prepared by introducing silicone-containing imidazolium ionic liquid [SiM]Cl into an acrylic acid gel system. The introduction of silicone composition increases the fracture strength of the hydrogel by 157% to 0.62 MPa. Notably, the existence of ionic liquid [SiM]Cl greatly enhances the hydrogel’s low-temperature resistance, offering it a freezing point as low as −42.9 °C and a breaking elongation of 650% even at −20 °C. The hydrogel has a conductivity of 2.46 mS/cm and shows excellent linear strain-sensing behavior. Flexible sensors fabricated using this hydrogel demonstrate sensitive and responsive performance to human movements, and the array sensors produced through three-dimensional printing technology can accurately reflect the distribution of force and deformation. Furthermore, the hydrogel exhibits favorable pH sensitivity and inhibits the growth of Escherichia coli and Staphylococcus aureus in more than 99%. The silicone ionic liquid-based multifunctional hydrogel in this work provides a noteworthy strategy for designing low-temperature-resistant flexible strain sensors.