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The best-known materials with a piezoelectric effect are ceramic or crystalline materials enabling the design of a wide variety of sensor and harvesting concepts. Due to their high young's modulus, their brittle material behavior and their high specific density, these materials are only suitable to a very limited extent for technical applications in which solutions are sought for integration into flexible systems such as textiles. Alternatives are offered by polymeric materials of which PVDF (polyvinylidene fluoride) has already been considered in several papers. However, these materials are disadvantageous in terms of transducer coefficients. More advantageous are piezoelectric electrets (also called piezoelectrets or ferroelectrets) due to their high piezoelectric coefficients and low mass density. They allow the realization of lightweight transducers with high output power. In this paper, the results from recently completed research projects are presented and possible applications for ferroelectrets to implement sensors and energy harvesters, especially for smart wearables, are outlined. |
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