Thermochromic optical/electrical hydrated ionogel with anti-freezing and self-healing ability for multimodal sensor

Abstract

Hydrogels featuring with high flexibility, comparable modulus to human skin, and biocompatibility, are deemed as an appropriate material for electronic-skins (e-skins). However, irreparable physical damage and poor environmental stability of the hydrogel-based sensor limit its practical applications in reality. Herein, we developed an ionohydrogel-based e-skin through in situ polymerizing thermoresponsive poly(oligo(ethylene glycol) methylacrylate) and acrylic acid in a hydrated ionic liquid (HIL) consisting of water and IL. Diversified hydrogen bonds among the polymer network, water and ILs enable the e-skin sensor with good self-healing ability. In addition, the inclusion of IL into the ionohydrogel greatly decreases the freezing point of water, imparting the e-skin sensor with excellent anti-freezing properties. More importantly, the temperature-induced switchable hydrophilia-hydrophobicity of polymer chain and the temperature-dependent destruction and reconstitution of the hydrogen bonds endow the ionohydrogel with switchable transparency, allowing intuitive visualization of ambient temperature. Attributing to the above merits, the ionohydrogel sensor could be used to monitor various human movements and visualize the change of temperature, showing promising applications in the multifunctional flexible sensor.