| Electrowetting-on-dielectric (EWOD) provides an efficient way to pump liquid droplets, because it does not require specific physical structures to be designed for each microfluidic function, i.e., mixing, cutting and pumping. Instead, these functions can be achieved on a general EWOD device by adjusting the program of electrical signals. Our goal is to fulfill a complete reconfigurable digital microfluidics platform having a large 2-D array of electrodes with the proper controls through hardware circuits and user interfaces.;Although cross-referencing EWOD devices provide a simple solution for large 2-D droplet operations, the driving efficiency is low and there are limitations to multi droplets operations. Direct-referencing EWOD devices on silicon or glass substrates are too expensive for disposable applications, which are most desirable for biomedical purposes. We have demonstrated 2-D direct-referencing EWOD devices based on the low cost multi-layer printed circuit board (PCB) technologies. Experiments on different types of PCB-EWOD devices with post-processing revealed surface flatness and smoothness were the main requirements for achieving reasonable driving voltages. The best PCB-EWOD devices with the CMP post-processing have comparable performances to devices made on silicon or glass substrates.;The direct-referencing devices allow the direct control of individual droplets, which permits feedback control of microfluidics operations. For digital microfluidics, the accurate droplet volume is important for analytical applications. We have developed real-time feedback control of the droplet volume during the all-electronic generation and cutting by fast capacitance measurement and high voltage modulation. Droplet volume precise within +/- 1% error and 5 time smaller standard deviations than open-loop control have been realized. Variable volumes of droplets can also be generated on the same electrodes by changing feedback control parameters. Droplet movement feedback control can also be realized in the same fashion.;LGA sockets and edge connector sockets, which greatly simplify packaging and assembly for high-density EWOD devices, are reported. We have developed a prototype of a portable EWOD system with the EWOD device, driving circuits, and a user interface which can be powered by 4 AA batteries for up to 40 hours. |
