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Advances in Optical Technologies
Volume 2017 (2017), Article ID 7610652, 5 pages
Research Article

Microfluidic Optical Shutter Flexibly - Actuated via Electrowetting-on-Dielectrics with <20 ms Response Time

Integrated Optoelectronics and Microoptics Research Group, Physics Department, University of Kaiserslautern, P.O. Box 3049, 67653 Kaiserslautern, Germany

Correspondence should be addressed to Henning Fouckhardt

Received 26 September 2017; Revised 29 November 2017; Accepted 6 December 2017; Published 31 December 2017

Academic Editor: Mikhail Noginov

Copyright © 2017 Henning Fouckhardt et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Tunable microoptics deals with devices of which the optical properties can be changed during operation without mechanically moving solid parts. Often a droplet is actuated instead, and thus tunable microoptics is closely related to microfluidics. One such device/module/cell type is an optical shutter, which is moved in or out of the path of the light. In our case the transmitting part comprises a moving transparent and electrically conductive water droplet, embedded in a nonconductive blackened oil, that is, an opaque emulsion with attenuation of 30 dB at 570 nm wavelength over the 250 μm long light path inside the fluid (15 dB averaged over the visible spectral range). The insertion loss of the cell is 1.5 dB in the “open shutter” state. The actuation is achieved via electrowetting-on-dielectrics (EWOD) with rectangular AC voltage pulses of  V peak-to-peak at 1 kHz. To flexibly allow for horizontal, vertical, and diagonal droplet movement in the upright x-y plane, the contact structures are prepared such that four possible stationary droplet positions exist. The cell is configured as two capacitors in series (along the axis), such that EWOD forces act symmetrically in the front and back of the 60 nl droplet with a response time of <20 ms.