Poly (3, 4-Ethylenedioxythiophene) - Poly (4-Styrenesulfonate) for Humidity Sensing Using Ink-jet Printing Technique on Flexible Polyimide Substrate

A fully reversible and repeatable flexible capacitive humidity sensor is realized from design concept to reality via an ink-jet deposition system. The humidity sensor is ink-jet fabricated with aqueous Poly (3, 4-ethylenedioxythiophene) - poly (4-styrenesulfonate), PEDOT: PSS ink and Toluene suspended nano Ag particles of 5 nm sized solution. The humidity is monitored by changes in the sensor's effective inter-digitated electrodes capacitance. The humidity sensor exhibits sensitivity with resolution and accuracy of 0.0067 nF/ %RH and 1% RH, respectively, towards the relative environmental moisture concentrations of 32% RH to 100% RH. A fast absorption time of < 1 second and desorption time of approximately 3 second for the humidity sensor is observed. [PUBLICATION ABSTRACT]