Fig. 1

Schematic illustrations and images of a differential hydration sensor platform with epidermal construction. a Optical micrograph showing the electrode layout for a representative device on a silicon wafer just before transfer to a thin, silicone substrate. b Optical micrograph of a pair of reference (left) and measuring (right) electrodes, with concentric designs, corresponding to channels 4 and 5 in a. Images of a device during c uniaxial stretching and d twisting. e Schematic illustration and equivalent circuit model (red) of a reference (left) and measuring (right) electrode