Design Of Electrowetting-on-dielectric Based Micro Droplets Driving Chip And Its Control System

With independent control of micro droplets to achieve samples’reaction, analysis and detection, digital microfluidics have become another potential direction after channel based microfluidic chip in the field of biochemical analysis. Among many technologies of trace amount fluid driving and controlling systems, electrowetting-on-dielectric (EWOD) technology occupies an important position for its flexible control method, simple structure and comprehensive droplets manipulation function.Based on EWOD effect, a kind of micro droplets driving chip and its control system were designed. First, the structural model of EWOD chip was built by ANSYS simulation software, the distribution of potential and electric field inside the dielectric layer and its effect to droplets were analyzed in AC and pulse voltage, respectively. As the result, the type of driving voltage was determined, it also provided a theoretical directive for the preparation of the dielectric layer and hydrophobic layer. On this basis, the selection and preparation process of the two layers were studied by MEMS technology. We chose PTFE as hydrophobic material, which formed a layer with uniform thickness and good hydrophobic property, on which the deionized water’s contact angle reached114.9°. The dielectric layer was prepared with organic polymer P(VDF-TrFE) and PI (polyimide), respectively. With the contrast of its EWOD effect, we select PI to deposit the dielectric layer, which showed a larger contact angle range and better breakdown characteristic. The design of FPGA-based control circuit implemented the output of square wave voltage signal with adjustable frequency and duty cycle, as well as timing switch of multi-channel driving electrode array.The result of micro droplets driving experiment demonstrates that stable droplets transport is achieved on the single-plate chip, the transport velocity varying with driving voltage is plotted; The parallel-plate chip successfully complies the generation, transport and merging of nanoscale deionized water droplets.