Electromechanical Characterization and Experimental Sensor Modeling of Thermoformed FEP Piezoelectrets for Dynamic Force Environments

This study explores the design, fabrication, and electromechanical characterisation of thermoformed tubular Teflon piezoelectrets for force measurement applications. Piezoelectrets, a subclass of electrets, leverage engineered dipole configurations within charged internal cavities to exhibit piezoelectric properties. Using fluorinated ethylene propylene (FEP) films, tubular structures were fabricated through thermal lamination and subsequently polarised to form highly sensitive and flexible piezoelectrets. The electrical response was characterised by controlled impact tests, sinusoidal stationary force inputs using a shaker system and an instrumented insole to evaluate the piezoelectret in a real dinamic environment. The impact test revealed that the piezoelectret exhibits a rapid response time of 20 ms with a maximum voltage amplitude of ±3 V. The frequency-domain analysis identified primary and secondary band-pass ranges, with peak sensitivity observed at 400 Hz. The stationary test with a shaker showed a steady sensitivity of 53.87 mV/N for signals within the 200 Hz and 700 Hz bandwidth.