P 15610 DIGITAL MICROFLUIDICS CONTROL SYSTEM II Abstract

P 15610: DIGITAL MICROFLUIDICS CONTROL SYSTEM II Abstract Digital Microfluidics (DMF) is a novel platform that can manipulate pico to nano liter sized discrete droplets by applying voltages to electrodes in an array. This allows DMF devices to move, combine, and separate fluid without channels, pumps or valves. In the most common configuration, these devices consist of a lower substrate with a "checker board" array of electrodes and an upper substrate that consists of a large planar ground electrode. Team: (Left to Right) Zachary Heifferon, Zachary Santagata, Patrick Crilly, Kenneth Bean, Michael Dushkoff, Kevin Cho, Adam Wardas, Harold Paschal (Guide) Figure 1: Sketch of DMF device. Introduction Constraints 1. Control pico to nano liter sized discrete droplets on a previously manufactured Digital Microfluidic (DMF) device that is provided to the MSD team. 2. Use Electrowetting to manipulate fluid droplet. 3. Use DI water as the liquid to be transported. 4. Measuring the complex impedance of a droplet. 5. Independently control the high voltage signal applied to each electrode. 6. Increase modularity by offering the capability of stacking multiple output boards. 7. Encase the entire control system in a one-box solution. 8. Using the existing GUI to interface with the designed control system. In order to manipulate and sense droplets in digital microfluidic devices, the associated control system must include the following components: (i) a signal generator capable of generating an AC waveform in the k. Hz range, (ii) an amplifier capable of increasing the generated signal up to approximately 120 V (rms), (iii) a means to connect the actuation voltage to any addressable position on the device, and (iv) a method to sense both the resistance and capacitance at any addressable position on the device. A GUI on a PC will provide for interaction between users and the system. Control System Layout An Arduino Mega is controlled via GUI to direct the 40 pin high voltage output to a certain electrode on the DMF chip. The signal generator is programmed to output 0 -3 V to the amplifier for a gain of 9 V, then to a 14: 1 step up transformer to achieve 120 V. The whole system is powered by ± 15 V, ± 12 V, and +5 V. Figure 2: (a) Previous DMF Laboratory set up, utilizing a PXI controller to manipulate the high voltage signal. (b) Side-view of the DMF chip with a droplet to be analyzed inside. Impedance Measurements Figure 3: Shows a web diagram of what each subsystem will interact with. In order to accurately measure various properties of droplets within the control system, their complex impedance must be accurately determined; impedance is a measure of the parallel resistance and capacitance on a single node on the DMF device. This complex impedance can be determined by applying a sinusoidal voltage to the specific node to be measured and then measuring the resultant phase and magnitude after this sinusoid has passed through the impedance. The applied sinusoidal voltage has an amplitude A with frequency ω, and the Digital Microfluidics load of R and C in parallel is terminated by a resistive load z. This results in an output voltage magnitude Voutmagwith phase delay Vph. The relationship between these variables and R and C is shown in (1) and (2): Figure 4: Shows the fully constructed boards and the flow of controls within the system. Acknowlegements Dr. Michael Schertzer University of Toronto’s Wheeler Lab Harold Paschal (Guide) Figure 5: Shows the electrical schematic for the input board design. Copyright © 2015 Rochester Institute of Technology