Surface engineering of the PLA films for fabricating dexterous humidity sensors

This study presents the surface engineering of the thin films of a biodegradable polymer, poly lactic acid (PLA), for its application in moisture/humidity sensors. The PLA films were deposited on the comb-like pre-patterned indium tin oxide coated glass substrates. The surface morphology of the thin film was modified by using various etchants having different solubilities in PLA. The surface morphology of the thin films was studied by using atomic force microscope and surface profilometer. The modified surfaces feature of the PLA films made them attractive to use as humidity sensors. The humidity sensing characteristics of the surface modified films were investigated by measuring the resistance and capacitance over a wide range of relative humidity levels (20-90% RH). An increase in capacitance and a decrease in resistance was observed by raising the humidity level inside the testing chamber. The proposed PLA based humidity sensor showed small hysteresis, high sensitivity and fast response & recovery time.