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Proceedings Paper

Optical control of electro-osmotic flow
Author(s): Huba Kirei; Andras Der; Laszlo Oroszi; Karpat Ferencz; Vilmos Rakovics; Pal Ormos
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Paper Abstract

Electro-osmotic pumping is an efficient way to move fluids in microfluidic systems. It is driven by the interaction of the Debye layer formed in the vicinity of the charged channel wall with a tangential electric field. The key parameters that determine the flow properties are the zeta potential of the surface and the electric field that drives the flow. Consequently, the flow can be controlled by appropriately modifying these parameters. Controlling the charge on the channel wall makes it possible to modify fluid flow. Likewise, the electric field close to the surface can be modified by changing the conductivity of the surface. The surface charge of appropriate materials can be changed by light illumination: the application of this phenomenon offers the possibility to optically control flow parameters. We have tested this possibility with several light sensitive surfaces. In the class of materials that change their charge upon illumination TiO2, a well known photoactive material was investigated. Experiments were also performed with the protein bacteriorhodopsin, known to change its surface charge following the release of protons into the solvent upon illumination. CdS was tested as the photoconductive material to modify the electric field by light. Linear microfluidic channels were prepared by soft lithography: a PDMS mold was placed upon a planar glass surface so that a rectangular cross section channel was formed upon the glass. The photosensitive materials covered the bottom glass surface. The experiments show that the flow can be readily modulated by illumination. The results demonstrate that it is possible to dynamically control microfluidic flow, opening up the prospect to create optically controlled complex microfluidic networks.

Paper Details

Date Published: 27 August 2005
PDF: 8 pages
Proc. SPIE 5930, Optical Trapping and Optical Micromanipulation II, 59301I (27 August 2005); doi: 10.1117/12.616240
Show Author Affiliations
Huba Kirei, Institute of Biophysics (Hungary)
Andras Der, Institute of Biophysics (Hungary)
Laszlo Oroszi, Institute of Biophysics (Hungary)
Karpat Ferencz, Research Institute for Solid State Physics and Optics (Hungary)
Vilmos Rakovics, Research Institute for Technical Physics and Materials Science (Hungary)
Pal Ormos, Institute of Biophysics (Hungary)


Published in SPIE Proceedings Vol. 5930:
Optical Trapping and Optical Micromanipulation II
Kishan Dholakia; Gabriel C. Spalding, Editor(s)

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