Humidity and temperature sensors on flexible transparency sheets

Abstract

Flexible humidity sensors are developed by coating copper films, thermally evaporated onto copier grade transparency sheets, with ZnFe 2O 4 nanoparticles dispersed in PMMA, and by applying carbon nanotubes electrodes on the top. Humidity sensing at constant temperature is demonstrated by the linear and reversible change of the device's capacitance in response to the RH changes, with average response and recovery times lower than 1 min. A simple local etching approach is used to pattern copper spiral heaters and resistances having calibrated temperature coefficient on the back and on the top of the substrate. The heaters and the calibrated resistances allow the temperature of the substrate to be set and measured, avoiding capacitance changes due to thermal drifts. © 2012 Springer Science+Business Media, LLC.