Self-powered health monitoring with ultrafast response and recovery enabled by nanostructured silicon moisture-electric generator

Abstract

Humidity sensors have been widely applied in health management, including respiration monitoring and non-contact sensing for human–machine interaction. Nevertheless, most existing monitoring systems hinging on moisture-sensitive materials require an additional external power source. In addition, the inferior sensitivity and long response/recovery time of the sensors still hinder their desirable healthcare applications. Here, we developed a self-powered humidity sensor built on the moisture-directly triggered electricity generation (MEG) effect, where silicon nanowire arrays (SiNWs) function as the sensing element, exhibiting an ultrafast response to humidity changes with high-level sensitivity. Humidity gradients induce charge directional transport in SiNWs nanochannels, directly actuating electricity signals generation without any additional power units for sensing. The enlarged surface area, oriented nanochannel structure, and superior electrical conductivity of SiNWs facilitate a robust dependence of the output voltage on humidity, enabling the sensor with quick response/recovery (∼0.10 s/∼0.17 s), ultra-high sensitivity, and broad detection range (3.94 mV/1% for 50–95% RH/1.13 mV/1% for 0–50% RH). Furthermore, we designed a smart respiratory monitoring system that can extract various respiration patterns and distinguish different language commands. We also constructed a non-contact human–machine interface leveraging the SiNWs sensor that can effectively disrupt virus propagation and bacterial infection. The elaborate self-powered humidity sensor proposed in our work could as well potentially be exploited for establishing wearable and integrated health monitoring platforms in the future.