Linear humidity sensor fabrication using bi-layered active region of transition metal carbide and polymer thin films

A linear humidity sensor based on bi-layered sensing area using exfoliated chromium carbide (Cr-3 C-2) and polyacrylamide (PAM) thin films has been fabricated through all printed methods. Transition metal carbides have unique properties that can be applied in various gas sensing applications. In this work, different combinations of Cr-3 C-2 with two polymers have been used to fabricate high performance linear humidity sensors. Cr-3 C-2 was processed using wet grinding exfoliation to achieve flakes and small particles of the material. Based on the working principle and sensing results of the single layered sensors, a novel bi-layered structure was proposed and fabricated with stable linear response and good sensitivity. The sensors are capable of measuring percentage relative humidity accurately in range of 0% RH to 90% RH with an absolute change of 660 Omega/%,RH and fast response and recovery times of 1 s and 1.9 s respectively. The sensors can also work with simple frequency based read-out circuit with a highly linear and stable response. The fabricated sensors are cheap, easy to fabricate, and are ideal to be used in high end environmental and health monitoring applications. (C) 2017 Elsevier B.V. All rights reserved.