Heteropolar ferroelectrets for ultrathin flexible keyboards and tactile sensors

Abstract

Ferroelectrets are flexible and conformable polymer transducer materials with a dominant longitudinal piezoelectric effect. They can be used in a wide range of transient pressure sensing applications. We present concepts for thin, flexible ferroelectret-keyboards (and advanced pressure sensors) based on ternary coded polarization patterns in a multilayer configuration. The decoration of a cellular polypropylene ferroelectret with a heteropolar polarization pattern of high resolution is a technical challenge. We discuss several concepts for achieving such polarization patterns and demonstrate a flexible 300 μm thin 3-layer keyboard where the combined signals of every single layer allow to encode and detect a total number of 26 keys.