A Highly Sensitive Flexible Humidity Sensor Based on Silk Fibroin Film and Trapezoidal Electrodes

The fabrication of high-performance flexible humidity sensors using biocompatible materials is crucial for expanding their application scope. Herein, a humidity sensor using silk fibroin (SF) as the sensing material is proposed and fabricated, accompanied with a systematical investigation of the effects of interdigital electrode geometry (the shape and spacing) and thickness of sensing layer on sensor performance. The prepared sensors were characterized by high sensitivity (3580%) at 95% relative humidity (RH), with a detection limit (LOD) of $1.34\times 10^{-{3}}$ %RH and a quantification limit (LOQ) of $4.48\times 10^{-{3}}$ %RH. It features a short response/recovery time of 37.81/1.15 s, excellent repeatability, outstanding flexibility, and minimal hysteresis (5.81%). The proposed flexible humidity sensors show pleasing applicability in many scenarios, amongst which there are three primary functions presented in this article, that is, the real-time respiratory status monitoring, skin perspiration moisture monitoring, and noncontact interactive switching. The experimental results reveal its broad application prospects in the areas of health monitoring and smart human–computer interactions. This work demonstrates a viable strategy for developing biocompatible humidity sensors with high performance and multifunctional applicability in next-generation wearable electronic devices.