Wearable Tactile Sensor Based on Hierarchically Structured PVDF-TrFE/ZnO Nanorods for Human Activity Monitoring

Flexible tactile sensors have become a focus of research owing to their potential in monitoring human physiology and motion signals. Nevertheless, it is still a challenge to simultaneously ensure high biocompatibility and precisely capture intricate and subtle physiological signals. Here, a flexible tactile sensor based on a sandwich structure was fabricated with Cu-coated polyimide (PI) membrane as a substrate and hierarchically structured PVDF-TrFE/ZnO nanorods as a piezoelectric nanocomposite membrane, which was prepared by spin-coating poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) onto vertically oriented ZnO nanorods (NRs) synthesized through a hydrothermal route. The surface morphology and crystallization of the pure PVDF-TrFE and nanocomposite membranes were investigated by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and x-ray diffraction (XRD). The results indicate a substantial increase in β-phase content from 87.50% in pure PVDF-TrFE to 95.06% in the nanocomposite membrane. The flexible tactile sensor incorporating the hierarchically structured PVDF-TrFE/ZnO NRs demonstrates a significantly superior piezoelectric response compared to the pure PVDF-TrFE membrane, with a sensitivity of 935 mV/N, which is approximately four times that of the pure PVDF-TrFE sensor. Additionally, the sensor shows a sensitive linear response within a force range below 4 N, and its output voltage remains stable even after 2000 compression cycles. Therefore, the sensor is capable of detecting various physiological signals, such as breathing, finger bending, and throat movements. These findings highlight its potential for use in wearable self-powered healthcare and physical activity monitoring systems.

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