inkjet printing of resistive-type humidity sensor for harsh environments
Committee for the Interdisciplinary Program in Materials Science and Engineering
Doctor of Philosophy
Materials Science and Engineering
Federici, John Francis
Sirkar, Kamalesh K.
Barat, Robert Benedict
Resistive - type
A flexible resistive-type humidity sensor for harsh environments is successfully designed and fabricated by an inkjet printing method using a Dimatix materials printer (DMP-2800 series from Fujifilm). Construction of the sensors is based on inkjet printed interdigitated silver electrodes on a polyimide flexible substrate along with an inkjet printable polyaniline (PANi) as humidity sensitive material. A copolymer of ethylene and vinyl alcohol (EVOH) is used as sensor protective coating. Double strand water- soluble PANi ink is synthesized by polymerization of aniline monomers with poly(4- styrenesulfonic acid) (PSSA) as a template.
Manufactured devices showed high sensitivity (/% @ 45%RH) to humidity with good linearity (R-squared correlation value of 0.99) and fast absorption and desorption responses over a broad range of humidity (/5-95%RH). The response time for the sensors without EVOH coating on top is around 5 and /5 seconds for absorption and desorption, respectively. The response time for the coated sensors is about 40 and //0 seconds for absorption and desorption, respectively. Sensors showed small hysteresis (about 3%) while a protective polymer coating provided a barrier to damage or false signals due to solvents and chemicals.
Fabricated sensors are characterized in order to investigate the structure and morphology of the thin films. UV-Visible spectroscopy is used to obtain information on PANi in solution form and to confirm that PANi in the form of emeraldine salt is obtained. FT-IR spectroscopy is used to verify the incorporation of the PSSA into PANi. SEM microscopy method is used to characterize the PANi-PSSA in powder form and the AFM method is used to show the morphology of the thin films.
njit-etd2012-054 (96 pages ~ 11,866 KB pdf)
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Created August 29, 2012