A Stable Piezoelectric Pressure-Sensing Device Based on Riboflavin-Poly(vinylidene fluoride) Composite Nanofibers for Potential Applications in Athlete Training

Piezoelectric pressure sensors are being extensively explored for their applications in wearable electronics. However, the long-term stability of the piezoelectric output voltage along with high sensing properties are still challenges for piezoelectric pressure sensors. To overcome this challenge, riboflavin nanorods were used as a filler in different concentrations for electrospinning of poly(vinylidene fluoride) (PVDF)-Vb composite nanowebs (Vb x PVDF 100-x ) and investigated for their morphology, structural, dielectric, mechanical, and piezoelectric pressure-sensing performance. Riboflavin nanorods incorporated into PVDF for the fabrication of piezoelectric pressure sensors helps to stabilize dipoles due to dipole–dipole interaction, hydrogen bonding, and van der Waals forces between the various functional groups of riboflavin and PVDF. Analysis via FTIR and dielectric characterization confirm that 2 wt % Vb NRs in PVDF nanofibers exhibit the highest β phase (67%) and dielectric constant (7.90 at 1 kHz) among all the samples. This sample exhibited high pressure sensitivities of 4.16 ± 0.184 and 1.23 ± 0.009 V/kPa in the pressure ranges of 2.5–10 and 10–20 kPa, respectively. Peak power generation through the piezoelectric device was 163 μW/g on continuous application of cyclic pressure. The piezoelectric voltage of the device was found to be stable for over 15 months, which is the highest duration of stability reported in the literature, to the best of our knowledge. Furthermore, the pressure sensor was integrated into the insole of a shoe and evaluated for its application in monitoring the physical activities of an athlete.