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Electrets have a long history starting more 2600 years ago and a bright future in the areas of soft transducers, plastic electronics, radiation dosimeters, air filters, etc. From the beginning, the similarities, the differences, and the combinations of dielectric and magnetic materials, of positive and negative “electricities”, of internal hetero-charges and external homo-charges, etc. have been puzzling natural philosophers and scientists. At the same time, rather slow, but continuous progress in the understanding and the application of electrets has been made. Recently, the essential role of charges in the piezoelectricity of ferroelectric polymers and polymer ferroelectrets led not only to new electret-based materials and devices, but also to new approaches for understanding the diversity of electrets. Electrets are dielectric materials with quasi-permanent space charges and/or dipole polarization. They come as electro-electrets, space-charge electrets, ferro-/piezo-electrets, molecular-dipole electrets, piezo-/pyro-/ferroelectric crystals or ceramics, and piezo-/pyro-electric composites. Electrets are not always polymeric and soft and often not only electromechanically active (piezoelectric/electrostrictive), but can also be inorganic, hard, heterogeneous, ferroelectric, pyroelectric/electrocaloric, providing a quasi-permanent electric field, etc. A brief overview of the long history, of the various types of electrets and of intuitive ways to understand their relevant properties from their nano-, micro- or macro-level structures will lead to examples of new materials and systems with useful applications.
Prof. Reimund Gerhard (University of Potsdam/ Technical University of Berlin)
Prof. Dr.rer.nat.habil. Dr.-Ing. Reimund Gerhard, FAPS, FIEEE 2018–2019 President, Dielectrics and Electrical Insulation Society, IEEE, U.S.A. 2006–2012 Vice Dean (2006–2008) and Dean, Faculty of Science, University of Potsdam 2004–2012 Chairman, Joint Board, M.Sc. program in Polymer Science at Free University Berlin, Humboldt University Berlin, Technical University Berlin and University Potsdam since 1997 University Professor (C4) for Applied Condensed-Matter Physics, Institute of Physics and Astronomy, Faculty of Science, University of Potsdam 1994–1997 University Professor (C3) for Sensorics, University of Potsdam, Germany 1985–1994 Senior Scientist & Project Manager, Department of Signal Processing and Display Equipment, Heinrich-Hertz-Institut für Nachrichtentechnik Berlin Dec. 1984 Dr.-Ing., Communications Engineering, TH Darmstadt (summa cum laude) July 1978 Dipl.-Phys., Technische Hochschule Darmstadt, Germany 1971–1973 Flute studies at Musikhochschule Würzburg, 2nd Flutist in Army Division 12 Visiting appointments at Bell Laboratories, Murray Hill, NJ, USA (1981-1983), at ENS Cachan, France (1995/1996 and 2014/2015), at Universidade de São Paulo, São Carlos, SP, Brazil (1999, 2005/06, 2012/13, 2016/17), at ESPCI Paris, France (1999), at Hebrew University of Jerusalem (2013), at Xi'an Jiaotong University, China (since 2015), at Chongqing University, China (since 2017), at University of Connecticut, Storrs, CT, USA (2018), at Technical University of Berlin (since 2018). Technology Transfer Prize Brandenburg and Adalbert Seifriz Prize (both 2001), IEEE Life Fellow (since 1993/2017), APS Life Fellow (since 2012/2017), IEEE Whitehead Memorial Lecture (2014), EuroEAP Society Achievement Award (2016), IEEE Bernhard Gross Memorial Lecture (2017).