Droplet Deformation and Pumping in AC Electro-Osmotic Micropumps
Sprache des Titels:
MICRO AND NANO FLOWS 2009
This contribution deals with the pumping and deformation of oil in water droplets in alternatingcurrent electro-osmotic micropumps. These micropumps are used to transport lowly conductive fluids through micro channels by means of a harmonically driven electrode array on the channel bottom. The periodic formation of an electric double layer above the electrodes results in an electro-osmotic flow, which carries along adjacent fluid layers. In experiments we observed that droplets immersed in the carrier fluid are
transported by the channel flow and periodically deformed when passing the electrodes. Due to the different polarizability and conductivity of the droplet and the carrier fluid, dielectrophoretic forces act on the fluiddroplet interface. These forces that are described by the Maxwell stress tensor increase with the electric field
strength and attract the droplet towards the electrode. This contribution analyses the mechanisms of droplet
pumping and deformation numerically by means of solving for the electric and the flow field to the two phases in the channel and by evaluating the dielectrophoretic forces on the droplet. A conservative level-set method is used to track the droplet surface accurately.