Ultrathin, all-organic, fabric-based ferroelectret loudspeaker for wearable electronics.

All-organic, flexible, and body-compatible loudspeakers have become increasingly attractive for wearable electronics. Due to their remarkable piezoelectric response, ferroelectrets are suitable for loudspeakers. Two distinct kinds of ultrathin ferroelectrets, including cellular polypropylene films and expanded polytetrafluoroethylene (ePTFE) films, were combined with three different types of electrodes ((Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS))-coated fabrics, PEDOT:PSS direct coating, and sputter-coated Au/Pd) for study regarding their frequency-dependent sound intensity and radiation directivity. Among the loudspeakers investigated, the all-fabric loudspeakers with ePTFE ferroelectret and PEDOT:PSS-coated spandex electrodes have a higher frequency dependency. Loudspeakers equipped with PEDOT:PSS-coated spandex electrodes are less angle dependent compared to other loudspeakers evaluated. Moreover, the soft loudspeaker constituted of an all-organic FEP(fluorinated-ethylene-propylene)-ePTFE-based ferroelectret and PEDOT:PSS-coated fabrics presented in this paper is easy to integrate with clothes and has a higher thermal stability. It is naturally compatible with the human body and a competitive candidate for future developments of all-organic loudspeakers for wearable electronic systems.