Flexible strain sensor based on PU film with three-dimensional porous network

Flexible strain sensors are widely used in wearable applications such as human motion and health detection, but it is challenging to prepare sensors with excellent performance, such as a wide sensing range and high sensitivity with a simple process and low cost. By taking the advantages of the electrostatic spinning technique that can prepare micro-structured films with fibrous porous networks, and this paper investigated the effect of the distance between the electrostatic spinning needle and the collection drum on the mechanical properties of the PU films produced. Then, the most mechanically excellent three-dimensional porous PU fiber film was selected as the substrate, and Carbon Black (CB) particles were selected as the conductive filler to prepare the CB/PU/Ecoflex strain sensor (CPESS) with a three-dimensional porous fiber network structure by spraying CB on the PU fiber film for the sensitive layer and applying a layer of biocompatible Ecoflex on the surface as the encapsulation layer. Owing to the substrates of this three-dimensional network microstructure with excellent mechanical properties such as high Young's modulus and elongation at break, the CPESS has an excellent sensing performance, with a detection range of 200 %, a sensitivity of up to 1443.95, rapid dynamic response of 50 ms, a low detection limit of (0.3 % strain), favorable repeatability, and excellent dynamic response at a large-scale tensile strain of 150 % − 200 %. The CPESS can be used to detect human joint movements and fine motion changes, and it exhibits great potential for smart wearable applications.