High Performance Humidity Fluctuation Sensor for Wearable Devices via a Bioinspired Atomic-Precise Tunable Graphene-Polymer Heterogeneous Sensing Junction

Measurements of an individual's water metabolism dynamical information can provide us rich biological information in a noninvasive way. This concept is hindered by the trade-off between the sensitivity and responsive velocity of traditional moisture sensors. Herein, inspired by the molecular detecting system based on weak bond interactions in natural organisms, we designed a new concept of a tunable graphene-polymer heterogeneous nanosensing junction by confining a reasonable thickness sensing material into graphene nanochannels. The fundamentally new sensing mechanism based on dynamical hydrogen bonds endows the sensor with over 4 orders of magnitude sensitivity toward a wide range of relative humidity (RH) (from 0% to 97%) with unprecedented fast response (20 ms) and recovery times (17 ms) with little humidity hysteresis. The promising advantages of the sensor allow us to record humidity fluctuation information in real time during a user's speech and breath, which can both reveal the speech feature and monitor the respiration rate accurately. Importantly, this advanced sensor provides a new opportunity for accurate and reliable physiological and psychological monitoring by detecting the subtlest RH fluctuations on human skin in a noncontact way.