Screen printing for producing ferroelectret systems with polymer-electret films and well-defined cavities
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We report a process for preparing polymer ferroelectrets by means of screen printing—a technology that is widely used for the two-dimensional patterning of printed layers. In order to produce polymer-film systems with cavities that are suitable for bipolar electric charging, a screen-printing paste is deposited through a screen with a pre-designed pattern onto the surface of a polymer electret film. Another such polymer film is placed on top of the printed pattern, and well-defined cavities are formed in-between. During heating and curing, the polymer films are tightly bonded to the patterned paste layer so that a stable three-layer system is obtained. In the present work, polycarbonate (PC) films have been employed as electret layers. Screen printing, curing and charging led to PC ferroelectret systems with a piezoelectric d 33 coefficient of about 28 pC/N that is stable up to 100 ∘C. Due to the rather soft patterned layer, d 33 strongly decreases already for static pressures of tens of kPa. The results demonstrate the suitability of screen printing for the preparation of ferroelectret systems.
KeywordsScreen Printing Polymer Foam Internal Charge Back Discharge Electret Property
The authors are indebted to the European Union for co-funding some of the essential equipment used in their work. R.G. wishes to thank the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and the Lady Davis Fellowship Trust (LDFT) for granting him visiting professorships at the Universidade de São Paulo (Brazil) and at the Hebrew University of Jerusalem (Israel), respectively.
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