High-Precision Stretchable Ionic Temperature Sensor Passivated with a Liquid Metal/Block Copolymer Multilayer Film

Moisture barriers are essential for ionic sensors because moisture has a direct impact on the stability and reliability of electrochemical properties. So far, stretchable moisture barriers that can maximize the advantage of using deformable ion gel as the active material have been rarely investigated and remain as a technological challenge. This study proposes a four-layer (4L) stretchable moisture barrier alternatively composed of a poly(styrene-isobutylene-styrene) copolymer (SiBS) film (2 μm in thickness) and a eutectic gallium-indium liquid metal (LM) film (1 μm in thickness). This multilayer barrier has a low water permeability of 9.09 × 10^-20 m²/Pa s at 50% uniaxial strain (ε) and retains the barrier properties at repeated stretchable cycles at ε = 50%. This study demonstrates a skin-attached precise ion gel-based temperature sensor that is independent of moisture change (even dipping in water) and body motions.