Achieving Reticulate Fibrous Ag NWs/ITO NPs/TPU Films for Sensing Human Physiological Activities with Low Detection Limit

In recent years, the optimization of flexible strain sensors has advanced from the design of single-type microstructures to hierarchical and multifunctional combinations of diverse microstructures. However, the one-step fabrication process of electrospinning limits the integration of fiber microstructures with other microstructures. Therefore, a reticulate thermoplastic polyurethane (TPU) fibrous film was prepared using a sieve as a collection template, featuring systematic regional variations in fiber morphology. These variations induce a synergistic effect, significantly enhancing both the sensing performance and mechanical properties. Silver nanowires (Ag NWs) and indium tin oxide nanoparticles (ITO NPs) were incorporated to form a conductive network. The inherent brittleness of conductive oxides boosts sensitivity, while the interaction between different-dimensional nanomaterials expands the sensing range. The sensor demonstrated exceptional sensitivity and linearity across a response range of 0.1–100% (gauge factor (GF) of 563.1, the strain of 50–100%), excellent durability even under rapid strain (over 1200 cycles at a strain rate of 144 mm/min), and rapid response/recovery times (188/232 ms). Furthermore, the microstructural synergy enabled the sensor to detect small strains with high sensitivity (GF up to 11.6 in 0.1–1% strain range), making it highly promising for human physiological activity monitoring.