TPU/Polypyrrole Composite Nanofibrous Membrane-Based Triboelectric Nanogenerators for Wearable Gait Monitoring and Healthcare Applications

In this study, electrospinning was employed to fabricate composite nanofibrous membranes comprising conductive polypyrrole nanoparticles (PPy NPs) embedded within a thermoplastic polyurethane (TPU) matrix as the positive triboelectric layer, while poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibrous membranes were utilized as the negative triboelectric layer to construct a triboelectric nanogenerator (TENG). Among the fabricated devices, the TPU/PPy-7.0 TENG exhibited the highest triboelectric output performance. Under an operating frequency of 5 Hz and an applied contact force of 60 N, the device delivered a maximum open-circuit voltage of 360 V and a short-circuit current of 62.8 μA, representing increases of approximately 105.9% and 29.9%, respectively, compared with those of the pristine TPU-based TENG. The enhanced electrical performance can be attributed to the excellent electrical conductivity and strong polarization capability of PPy, which increase the effective dielectric constant of the TPU matrix and facilitate charge transfer during the triboelectrification process. Furthermore, interfacial polarization induced at the TPU/PPy interfaces promotes charge accumulation and increases the surface charge density, thereby contributing to the improved triboelectric output. The TPU/PPy-7.0 TENG also demonstrated excellent operational durability, maintaining a stable output voltage of approximately 360 V after 20,000 contact−separation cycles. To demonstrate its practical applicability, the TENG device was integrated into an insole for footstep sensing and activity monitoring. The developed self-powered sensing system enables continuous monitoring of walking activity, demonstrating strong potential for wearable gait monitoring and healthcare applications.