Dual-function ionic flexible sensors with linear humidity and strain perception based on grid weave structure

Multifunctional flexible sensors capable of detecting strain and humidity are crucial for the accurate, stable, and safe information between individuals and objects in complex environments. However, achieving dual-function ionic flexible sensors (IFS) with linear humidity and strain perception remains an enormous challenge. This paper introduces a multifunctional wearable sensor based on ionic liquids (ILs) capable of simultaneously detecting humidity and strain. The sensor utilizes a grid-structured thermoplastic polyurethane (TPU) fiber via near-field electrospinning (NFS) technology, and encapsulates it with IL-bonded waterborne polyurethane (WPU) to achieve linear sensing of both humidity and strain. Owing to the grid structure design, the sensor exhibits high linearity in the detection of both humidity and strain. Moreover, the sensor exhibits excellent stability and mechanical flexibility, and a quick response to humidity changes, a short recovery time. Consequently, the sensor can successfully monitor human respiration with strain interference. Additionally, the mechanism of the grid-structured effect on sensing signals linearity is revealed. This research paves the way for dual-function flexible sensors and their applications in human movement, respiration monitoring, and human-machine interaction.