Fabrication and characterization of chemiresistive CuO sensors sensitized by Ca-doping for detection of sweat electrolyte concentration

Intense electrolyte loss as a result of excessive sweating can disrupt the electrolyte balance in the body and cause damage to many organs, as well as potentially fatal disturbances in even brain functions. There are commercial sensors developed to monitor users' physical activity, however, few of them can provide information on users' health status through sweat analysis. Herein we report a chemiresistive sensor to monitor the sweat electrolyte concentration level. Metal oxide semiconducting CuO films were deposited on Au electrodes as sensing layers. Ca2+ ions were doped into the CuO lattice as sensitizer. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and UV–Vis spectroscopy were used to characterize the films. Sensors produced with pure and Ca-doped CuO films were tested against different concentrations of artificial sweat. The sensors responded well to sweat electrolyte concentration with a linear detection range of 20–80 mM. Detection limits between 6.64 and 9.86 mM were estimated using standard deviation methods. Average sensor response times were found to be 12 s.