Development of a Bi-functional RH-Strain Flexible Sensor

Abstract

Bi-functional sensors capable of simultaneously detecting multiple physical stimuli are essential for next-generation wearable and intelligent sensing systems. However, most reported bi-functional sensors rely on the simple integration of independent sensing elements without intrinsic coupling. In this work, a bi-functional sensing device for simultaneous relative humidity (RH) and mechanical strain detection was developed and systematically investigated. The system integrated a silk fibroin (SF)-based RH sensor and a carbon nanotube (CNT)–PDMS-based strain sensor. The two sensing units were then electrically coupled using both parallel and series configurations. Their impedance responses were studied through MATLAB simulation and experimental measurements under controlled RH and strain conditions. The results proved that the sensor could simultaneously measure RH and strain, but the measurable range has limitations. This work provides insights into the design and optimization of multifunctional sensing systems with coupled electrical responses.