Design, simulation and fabrication of electrowetting-based actuators for integrated digital microfluidics

Electrowetting-on-dielectric (EWOD) is a promising method for manipulating tiny amounts of liquids. However, the miniaturization and the monolithic integration become the great challenges to improve the EWOD applications in actual lab-on-a-chip systems. In this paper, we present an IC-compatible digital microfluidic actuator, which uses silicon as the substrate and the thermally grown SiO2 film on heavily phosphorus-doped poly-silicon microelectrodes as the high quality dielectric layer. The fundamental EWOD operations, such as the droplet transportation, division, creation, and mergence, are numerically analyzed by using the computational fluidic software, CFD-ACE+. The simulation results of transportation and division show that it is an antinomy to select the gap height between two plates for improving respective performances. A tradeoff value of the gap height of 133 mu m is ultimately used to implement the fundamental operations with one actuator. In experiments, all above operations are successfully achieved in air by applying 70 V voltages. Owing to the IC-compatible fabrication, the integration with peripheral circuits is technically feasible to achieve a miniaturized microfluidics.