A Multifunctional Flexible Sensor with a 3D TPU Fiber-Based Conductive Network via In Situ Reduction of an AgNP Layer

Good breathability and antibacterial properties are among the key prerequisites for applying flexible sensors to electronic skins or similar devices. As such, these features are hot topics for ongoing research. In this paper, a three-dimensional (3D) thermoplastic polyurethane (TPU) fiber network backbone was constructed by using the electrostatic spinning technique. Then, silver nanoparticles (AgNPs) were deposited on this backbone via an in situ reduction reaction with AgNO3 to form a 3D conductive network. From this reaction, a highly sensitive and flexible multifunctional sensor with excellent breathability and antibacterial properties was obtained. The sensor’s efficient 3D conductive network was shown to give the flexible sensor: fast response (21 ms) and recovery times (43 ms); high conductivity (4600 S/m); a high gauge factor (GF = 9.52 × 104); a low strain detection limit (0.05%); and a wide strain operating range (0.05–120%). A water vapor permeation test demonstrated that the synthesized sensor’s water vapor transmission rate (WVT) was 2209 g–2 day–1, which is approximately four times higher than that of human skin. Additionally, the in vitro antibacterial activity assay revealed that the diameter of the inhibition circle of both Escherichia coli and Staphylococcus aureus expanded to 4.17 and 5.67 cm, respectively, as a result of the antibacterial effect of the silver particles on the sensor’s surface.