A significant driving force for the
fabrication of IoT-compatible smart health
gear integrated with multifunctional sensors is the growing trend
in fitness and the overall wellness of the human body. In this work,
we present an autonomous motion and activity-sensing device based
on the efficacious nucleation of the polar β-phase in an electroactive
polymer. Representatively, we investigate the nucleating effect of
TiO2 nanoparticles on weight-modulated PVDF-HFP films (PT-5,
PT-10, and PT-15) and subsequently prototype a sensing device with
the film that demonstrates superior β-phase nucleation. The
PT-10 film, with an optimal polar β-phase, shows the highest
remnant polarization (2Pr) and energy density of 0.36 μC/cm2 and 22.3 mJ/cm3, respectively, at 60 kV/cm. The
films mimic a high pass filter at frequencies above 10 KHz with very
low impedance and high ac conductivity values. The frequency-dependent
impedance studies reveal an effective interfacial polarization between
TiO2 nanoparticles and PVDF-HFP, explicitly observed in
the low-frequency region. Consequently, the sensor fabricated with
PT-10 as the sensing layer exhibits ultralow frequency detection (25
Hz) resulting from the blood flow muscle oxygenation. The device successfully
senses voluntary joint movements of the human body and actively tracks
a range of motions, from brisk walking to running. Additionally, through
repetitive human finger-tapping motion, the nanogenerator lights up
multiple light-emitting diodes in series and charges capacitors of
varying magnitudes under 50 s. The real-time human motion sensing
and movement tracking modalities of the sensor hold promise in the
arena of smart wearables, sports biomechanics, and contact-based medical
devices.