29. Polymer Electrets and Ferroelectrets as EAPs: How to Start Experimenting with Them

Ferroelectrets are used in capacitive piezoelectric sensors. When a force is applied to such a sensor, an electrical signal is generated. We first describe the equivalent circuit representation of a ferroelectret sensor element and proceed with the coupling of the sensor element to a measurement device. Based on the governing equations for the measurement signal following a given time-dependent force, we show that the sensors measure either force or force rate. We illustrate the use of ferroelectrets by proposing a reaction game using ferroelectret sensor elements. Several sensor elements are coupled to a measurement instrument, such as an oscilloscope, while forces are applied by the gamers as fast as possible with their hands. The sensor element is easily prepared by students within a few minutes, immediately enabling playing with the elements, followed by a fundamental understanding of ferroelectret force sensing.