Stimuli-free Zn/soda-lime glass/CuO-based MIS device for sensing human skin moisture

Abstract

Proximity sensors are important devices for measuring the proximity/closeness of an object. Furthermore, being selective in sensing the proximity and simultaneously differentiating humans from that of a non-living object/machine is crucial. Herein, we designed a simple and cost-effective stimuli-free Zn/soda-lime glass/CuO-based MIS device that can detect ambient moisture and moisture emanating from human skin. Neither any external bias nor any stimulus is required for the operation. Basically, the device operates at room temperature and induces current and voltage owing to exposure to moisture. Molecular insights for mechanistic understandings are evaluated using in situ Raman spectroscopy, and it is ascertained that ion transport between the Zn and CuO electrodes with soda-lime glass as a medium induces a voltage and current depending on the quantity of the moisture. Further, the investigation suggests that the device can be used as a proximity sensor to distinguish humans and robots.