Optical control of electroosmosis
Principal Investigator: Pál Ormos
This project is part of the EU-FP6 cooperation ATOM-3D
Electroosmosis can be effectively used to manipulate fluid in microfluidic systems. The flow can
be controlled by the geometry of the system, the zeta-potential of the channel walls, and the
structure of the electric field itself which drives electroosmosis. In our concept we use light to
dynamically modify the spatial structure of the electric field to control the flow. The conductivity
of a photoconductor film parallel to a microfluidic channel is changed dynamically by appropriate
illumination. A local increase in the conductivity upon excitation results in the reduction of the
electric field in the corresponding microchannel region, and thus the local electroosmotic driving
force. This way it is possible to realize a range of functions needed for the manipulation of fluids like
switching of flow, (re)directing flow and mixing. The concept is demonstrated experimentally, modeled and interpreted.
Below you can see the microfluidic sample used in the experiments. As the photoactive layer
we used CdS (cadmium-sulfidem, chemically deposited onto the glass surface). The sample was created by the soft lithography method.
At the two ends of the microchannel there are two reservoirs open to the outside containing the electrodes.
L. Oroszi, A. Dér, H. Kirei, V. Rakovics, and P. Ormos,
Control of electroosmostic flow by light, Appl. Phys. Lett. 89 263508 (2006)