All-soft physical and chemical microsystems based on liquid metal for wearable electronics applications

This paper introduces all-soft physical and chemical sensing systems for wearable electronics applications comprising soft microsensors and soft functional circuits using gallium-based liquid metal (eutectic gallium-indium alloy, EGaIn) and poly(dimethylsiloxane) (PDMS). An advanced EGaIn thin-line patterning technique enables size-scalable, high density, and residue-free liquid metal structures that form the base for the demonstrated physical microsystem for strain measurement and liquid-phase chemical sensing platform. The stretchable strain sensor consists of a soft Wheatstone bridge circuit, which exhibits a linear output voltage response for applied uniaxial strain up to 28%. The liquid-phase chemical sensor is comprised of a microfluidic capacitive sensor vertically integrated with a spiral inductor to form an LC resonance circuit. Its resonance frequency changes in response to the relative permittivity of the liquid solvent.