All-organic flexible ferroelectret nanogenerator for wearable electronics

Abstract

Piezoelectric nanogenerators used for energy harvesting in wearable electronics require flexibility, durability, and skin compatibility. Previous work has identified expanded polytetrafluoroethylene (ePTFE) as a potential candidate. A ferroelectret film was prepared by laminating ePTFE membranes and two fluorinated ethylene propylene (FEP) films using hot pressing, and injecting charges through corona discharge process. Using conductive fabric containing poly(3,4- ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as electrodes, an all-organic nanogenerator was obtained. The open- circuit voltage and short-circuit current were measured to characterize the piezoelectric response. The short-circuit current was found to be approximately 50 nA for one layer of ePTFE membrane (15 × 15 mm2) under light pressure from one finger, and no increase in current and voltage was found from additional ePTFE layers. The polarizability and charges stability of the FEP/ePTFE/FEP film were also evaluated. The flexible ferroelectret nanogenerator can be embedded into clothes or insole and is expected to power continuously future wearable electronics system.