Realization of Piezoresistive Behavior in P(VDF-TrFE) Thin Film via Carbon Black Modulation with Ultrahigh Gauge Factor

Abstract Despite significant progress in piezoelectric materials, the realization of a single material system capable of supporting both efficient energy harvesting and ultrasensitive piezoresistive pressure sensing remains a major challenge for wearable electronics. This study demonstrates the possibility of tuning the piezoelectric and piezoresistive behavior in ultrathin, unpoled poly(vinylidene fluoride–trifluoroethylene)/carbon black [P(VDF-TrFE)/CB] composite films, by varying the CB concentration within the polymer matrix. At 0.6 wt.% CB loading, the films exhibited enhanced piezoelectric energy harvesting performance, delivering an output voltage of 2.74 V pk−pk under a 6 N force at 1 Hz excitation, corresponding to a peak power density of 4.7 mW/cm 3 . Interestingly, increasing the CB content to 0.8 wt.% induced dominant piezoresistive behavior, with the films showing a remarkable 31% change in resistance under an applied force of 20 g (0.5 kPa). The device demonstrated an ultrahigh gauge factor of 1.5 × 10 6 and a sensitivity of 0.6 kPa −1 , highlighting its potential for low-pressure detection. This dual functionality highlights the ability to tune the electromechanical response of P(VDF-TrFE) simply by incorporating conductive nanofillers, thereby allowing both energy harvesting and high-performance pressure sensing in a single material platform. Moreover, this heterogeneous sensing platform provides a self-sustainable mechanism in which the harvested piezoelectric energy can also be utilized to support the piezoresistive sensing process, eliminating reliance on external power sources. These findings establish P(VDF-TrFE)/CB composites as a cost-effective and scalable pathway toward multifunctional, flexible, and durable materials for next-generation wearable sensing and energy harvesting applications.