Biocompatible liquid metal coated stretchable electrospinning film for strain sensors monitoring system

Liquid metals (LMs) are potential inorganic materials which could be applied in flexible and deformable electronics owing to their fluidity, low viscosity, high metallic conductivity, and low toxicity. However, recently reported sensing devices based on LMs required complex processes with high cost. Herein, a flexible three-dimensional (3D) conductive network was prepared by coating LM droplets onto an electrospun thermoplastic polyurethane (TPU) fiber film. The LM is suspended between the TPU fibers and self-coalesces into a vertically buckled and laterally mesh-like structure, which provides good biocompatibility, conductivity, and stretchability simultaneously. The LM-TPU composite-film-based flexible device demonstrates a multitude of desired features, such as a widely workable stretching range (0%–200%), sufficient sensitivity under stretching strain (gauge factor (GF) of 0.2 at 200% strain), and outstanding stability and durability (9000 cycles). In vitro biocompatibility experiments show that the LM-TPU composite film directly attached to the skin has excellent biocompatibility. Such strain sensor-based integrated monitoring systems could monitor human body motions in real time, such as muscle movement and joint motion, revealing application prospects in healthcare and human-machine interfacing.