A high-performance humidity sensor based on 3D porous SnO2-encapsulated MCM-48 for real-time breath monitoring and contactless gesture detection

Abstract

Ordered porous SnO₂/MCM-48 was used as a basis for developing a resistive-type humidity sensor fabricated by drop-casting on a Ag–Pd substrate and its use was demonstrated for real-time respiration monitoring and no-contact sensing for the first time. Using a hydrothermal method, a series of SnO₂/MCM-48 humidity sensors were prepared and comprehensively compared. The humidity sensor was tested in a variety of humidity levels from 11 to 98% RH for humidity detection, and various flexible humidity testing experiments were conducted and the results were recorded. The results showed a significant enhancement in the humidity-detecting capabilities of the sensor, which was ascribed to the combined outcomes of the use of SnO₂ and the material's structure characterized by the pores. The sensor demonstrated fast response and recovery times of 9 s and 12 s with high sensitivity and minimal hysteresis. Further, the stability over time of the SnO₂/MCM-48 sensor was confirmed, indicating its potential for commercial applications. The prepared sensor was used to test human breathing patterns under various tangible circumstances, and its successful performance demonstrated its potential for use in medical applications. In a broader context, the SnO₂/MCM-48-based humidity sensor proposed in this study can detect patterns in human health without physical contact and is very stable, easy to synthesize, and environment friendly.