Research on a Humidity Sensor Based on Polymerizable Deep Eutectic System-Modified Filter Paper

In recent years, paper-based humidity sensors have emerged as a highly promising technology for humidity detection. In this work, a polymerizable deep eutectic solvent (PDES) was prepared via a one-step blending method, which was applied to modify filter paper. The modification process did not alter the overall structure of the paper cellulose but rather targeted only its internal cellulose channels, thereby minimizing any impact on the paper’s original moisture-independent properties. The filter paper functioned both as the substrate and the humidity-sensing material in the fabricated sensor. The finger-like electrodes were designed using AutoCAD 2018 software and then printed onto the modified paper using screen-printing technology to fabricate the humidity sensor. Different saturated salt solutions were used to simulate corresponding humidity environments and evaluate the humidity performance of sensors. Compared with that of the blank paper-based humidity sensor, the sensitivity of the sensor modified by the PDES was significantly greater, and the recovery time was greatly shorter. Specifically, the sensitivity increased from 1.34 to 10.36 at 54% RH and from 166.24 to 519.2 at 98% RH. Additionally, the sensor response time was reduced from 728 s to 137 s. PDES modification significantly improved the moisture-sensitive characteristics and detection performance of the sensor.