Polymeric humidity sensor based on laser carbonized polyimide substrate

Abstract

This research demonstrated some of the capabilities of a laser carbonized polyimide substrate functioning in an all-polymer humidity sensor. Most polymeric chemical sensors are based on alumina or silica substrates with gold or silver deposited wiring. These sensor substrates are relatively expensive and complicated to manufacture. A Kapton-based all-polymer substrate is a possible alternative for use in future chemical and biological sensing applications. The substrate was carbonized to form electrically conducting filaments using a focused cw argon ion laser beam operating at 364 and 514 nm. The substrate was coated with a hygrosensitive polymer and tested varying humidity, test frequency, test voltage, and temperature. Two separate hygrosensitive polymer coatings were tested: 2-hydroxy-3-methacryloxypropyltrimethylammonium chloride (HMPTAC) and polyethylene oxide doped with lithium perchlorate (PEO-LiClO 4). Humidity detection was used as a proof of concept for future research into chemical and biological agent detection. Results demonstrate the Kapton-based sensor performed as well as an alumina gold substrate and indicate the all-polymer substrate is a viable sensor substrate for future use in chemical detection systems.