Fig. 1. Perforated e-skins with inorganic physical sensors.

(A) Design of auxetic dumbbell through-hole patterns for driving sweat-permeable channels and synergistic physical properties of e-skins. (B) Schematic illustration of perforated e-skins with (I) auxetic dumbbell through-hole patterns. As the hole interspacing is narrower than the average diameter of a sweat pore, the e-skin can form open channels on the pore. Four multiple sensors—(II) Pt resistance thermometer, (III) capacitive-type Au hydration sensor, and ZnO nano–thin-film–based (IV) strain and (V) UV sensor—are also perforated to suppress sweat trapping at the sensing regions. (C) Optical images of the perforated e-skins showing auxetic dumbbell through-hole patterns, Pt thermometer, Au hydration sensor, ZnO strain, and UV sensor. The images were obtained after lamination on the wrist, except for the leftmost image.