Fabrication of miniaturized CSRR-loaded HMSIW humidity sensors with high sensitivity and ultra-low humidity hysteresis

In this work, half-mode substrate integrated waveguide (HMSIW) resonators loaded with a complementary split ring resonator (CSRR) are designed and fabricated for humidity detection application. Introduction of the CSRR can significantly reduce the dimensions of the HMSIW devices in order to meet the demand for device miniaturization. Graphene oxide (GO) is used as the humidity sensing material and is deposited on the different regions of the surface of the CSRR. A series of experimental results indicate that high humidity sensitivity and ultra-low humidity hysteresis can be achieved when GO films are deposited on the central conducting patch of the CSRR. The sensor shows a high sensitivity of up to 772 kHz/%RH in the humidity range of 11.3% to 84.3% and 3.415 MHz/%RH in the high humidity range (> 84.3%RH), and an ultra-low humidity hysteresis (0.07%RH) in the range of 11.3% to 97.3%RH. This work provides a promising approach for the realization of miniaturized microwave humidity sensors with high sensitivity and ultra-low humidity hysteresis. (C) 2017 Elsevier B.V. All rights reserved.