Hollow NiCo-LDH polyhedrons for 1-second level humidity detection and respiratory monitoring†

Abstract

Humidity sensing, as a promising approach for detecting environmental humidity and respiration patterns, is garnering widespread attention. Here, we present a quartz crystal microbalance (QCM) humidity sensor modified with hollow NiCo-LDH polyhedrons for real-time monitoring of both environmental humidity and human respiration. The hollow NiCo-LDH polyhedrons possess a large surface area and loose stacking, which contribute to its excellent humidity sensing performance. In practical applications, our device demonstrates outstanding performance when the relative humidity (RH) ranges from 11% to 97%, exhibiting high sensitivity, rapid response and recovery time (all within 1 s), and high selectivity. Furthermore, the sensor is capable of effectively distinguishing different breathing patterns, such as normal breathing, breath after exercising, and holding the breath, as well as detecting humidity changes before and after drinking water. This demonstrates its potential application prospects in monitoring and analyzing human health conditions.