FREE SURFACE MICROFLUIDICS BASED ON ELECTROWETTING

Multiple microfluidic devices such as Lab-on-a-Chip and microarrays are currently being used in various applications in biology and chemistry. Some of these devices use electrowetting as means of moving or mixing droplets to perform desired tasks. By applying electric potential to droplets, the wetting properties of the surface can be altered and thus allowing movement of the droplet. In this project, we intend to move and mix two droplets containing different chemicals using AC electrowetting. We use AC voltage to prevent electrolysis at small voltages. The chips are placed on a thermoelectric heater, to evaporate the solvent. The resistance of a resistive temperature detector is measured to control the temperature of the surface and this way control the evaporation rate of the droplet. Different voltages, frequencies, dielectrics and molarity of solutions are being experimented with to find a set up that requires less voltage to move the droplets. In addition, numerical simulations are being performed using COMSOL Multiphysics to find the electric field around the droplet due to the applied voltage to the electrodes. Initial results have shown that best electrowetting without electrolysis occurs with applied 4Vpp at a frequency of 300 Hz on a gold electrode. We expect to be able to determine the best set up that requires lower voltage for droplet movement and evaporation.