Piezo-, pyro- and ferroelectrets: soft transducer materials for electromechanical energy conversion

Cellular space charge polymer electrets significantly enlarge the basis of pyro- and piezoelectric as well as ferroic materials. Since the first review of the field has been published in this journal (R. Gerhard-Multhaupt, Less can be more: Holes in polymers lead to a new paradigm of piezoelectric materials for electret transducers, IEEE Trans. Dielectr. Electr. Insul. Vol.9, pp.850-859, 2002), progress has been achieved in the understanding, preparation and characterization of cellular space charge electrets. Advanced applications arise in stacked microphones, artificial sonar systems, and in the combination of piezo- and ferroelectrets with flexible electronics. In the present survey an update of the developments since 2002 is provided