This study aims to investigate the design, fabrication and characterisation of self-powered flexible pressure sensors based on zinc oxide (ZnO) nanorod arrays embedded in a poly(vinylidene fluoride) (PVDF) piezoelectric matrix, targeting continuous health monitoring and human–machine interface applications.
Vertically aligned ZnO nanorods were synthesised via low-temperature hydrothermal growth and embedded in an electrospun PVDF nanofibre matrix. Strain engineering was applied by controlling nanorod aspect ratio (diameter 80–250 nm; length 1.2–4.5 µm) and nanocomposite thickness (20–80 µm). Structural and electromechanical properties were characterised using X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and Fourier-transform infra-red spectroscopy. Output voltage, current density and sensitivity were measured under cyclic compressive loads from 0.1 to 500 kPa.
The optimised composite (aspect ratio 18:1, thickness 45 µm) delivered an open-circuit voltage of 32.4V, short-circuit current density of 8.7 µA cm² and peak power density of 28.6 µW cm² at 50 kPa. Sensitivity reached 6.23 mV kPa¹ below 10 kPa, with a linear range of 0.1–500 kPa, response time of 28 ms and 96.2% output retention over 50,000 cycles. Real-time wrist pulse, finger-bending and plantar pressure monitoring were demonstrated without external power.
The battery-free architecture and low-cost hydrothermal synthesis present a scalable pathway towards self-powered diagnostic wearables for clinical and consumer health monitoring.
A holistic strain-engineering strategy combining nanorod aspect ratio tuning and matrix porosity control simultaneously maximises piezoelectric output and mechanical compliance, exceeding the sensitivity and power density of previously reported single-filler piezoelectric wearable sensors.
