Highly strain-sensitive and stretchable multilayer conductive composite based on aligned thermoplastic polyurethane fibrous mat for human motion monitoring

Conductive composite materials with single-component active fillers often possess high filler content, poor mechanical performance, and unimproved sensing behaviors. To overcome these challenges, a flexible strain sensor with a sandwich structure was achieved by coupling one-dimensional conductive filler carbon nanotubes (CNTs) with two-dimensional MXene nanosheets on an aligned thermoplastic polyurethane (TPU) electrospinning fibrous film with wave structure through vacuum suction filtration and encapsulation with Ecoflex. The synergy of MXene and CNTs can be employed to develop a good conductive path in the matrix, which can realize versatile sensing performances. Meanwhile, the MXene-CNTs/TPU/Ecoflex composites (MCTEC) when stretched in vertical fiber direction exhibit low hysteresis owing to the combination of the aligned TPU fiber network with wave structure and the low viscoelasticity of Ecoflex. The strain sensor based on MCTEC also possesses a low detection limit (0.1% strain), wide sensing range (0-251% strain), fast response time (50 ms), and fine sensing recoverability. Additionally, this strain sensor can monitor human limb movement and vocalization, which facilitates the development of strain sensors in the field of intelligent healthcare.