High-Sensitive Microwave Humidity Sensor based on PAN and MXene

Currently, most humidity sensors have low sensitivity to detect low relative humidity. Therefore, it is necessary to optimize microwave sensor devices and moisture sensitive materials in concert to achieve high sensitivity for low relative humidity detection. In this paper, we propose a miniaturized, high-sensitivity microwave humidity sensor for humidity detection. A complementary split ring resonator (CSRR) is used as the detection electrode. Its high-field region is located in a large copper layer, providing an excellent receiving plane for electrostatic rotation. Therefore, we prepared a moisture-sensitive film of polyacrylonitrile (PAN) with good mechanical stability and water insolubility directly on its surface, compounded both materials by drop coating with an ethanol suspension of MXene, and then characterized relative humidity using the S - parameter. Experimental results indicate a sensitivity of 0.055 dB/% RH in low humidity environments, characterized by an amplitude shift from 10% RH to 70% RH for relative humidity. The sensor achieves high sensitivity in low humidity environments, with its resonant frequency moving less at different humidity levels, and a sensitivity of 0.065 dB/% RH at 2.865 GHz. The sensor is thus potentially useful for future implementations of low-cost microwave humidity sensors in conjunction with fixed-frequency detection circuits.