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Design and wafer-level replication of a freeform curvature for polymer-based electrostatic out-of-plane actuators

: Lange, Nicolas; Scheiding, Sebastian; Wippermann, Frank; Beckert, Erik; Eberhardt, Ramona; Tünnermann, Andreas


Journal of micro/nanolithography, MEMS and MOEMS 12 (2013), Nr.4, Art. 041205, 8 S.
ISSN: 1537-1646
ISSN: 1932-5150
ISSN: 1932-5134
Fraunhofer IOF ()
actuators; polymers; lithography; adaptive optics; micro-optics; micro-electromechanical systems

The purpose of this paper is the fabrication, replication, and wafer-level imprinting of a polynomial curvature to enable the realization of an electrostatic out-of-plane zipper actuator with considerably altered and enhanced voltage versus deflection behavior. This is achievable only by changing silicon as established main material to a UV-curable
polymer, while retaining the lithography-based fabrication technology. The basic concept of this actuator is explained, and with derived design rules, a finite element analysis is established to design an actuator with an integrated micro-mirror and 10- µ m deflection at 60-V driving voltage. The diamond turning of the master mold and the wafer-level fabrication process of the polynomial curvature are explained in detail and realized by unconventional wafer-level imprinting of a UV-curable, nonconducting polymer. The experimental results of the deflection measurements show a deflection of the intended 10 µ m at 200 V. This deviation in necessary driving voltage can be explained by fabrication-induced intrinsic stresses, which bend the actuator beams upward. This increases the gap between the electrodes, making it possible to achieve 26- µ m deflection at 300 V. This paper finalizes with an illustration about the now possible designs for polymer-based electrostatic zipper actuators.