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UBC Theses and Dissertations

Rapid prototyping of a programmable controller for digital microfluidic systems Murran, Miguel Angel


Digital microfluidic (DMF) devices can be used to perform complete chemical or biochemical analysis on miniscule droplets; thus they have the potential to replace large and expensive laboratory facilities. Droplets are manipulated on a DMF device by the application of electrical signals to an array of electrodes. Several droplet operations including transport, mixing, and splitting can be performed by the sequential timing of these electrical signals. However, the reliability and successful operation of a DMF device largely depend on improving its controller hardware and fabrication quality. A closed-loop controller uses feedback information to compensate for modeling and run-time uncertainties; thus the controller can improve the accuracy and robustness of droplet operations on a DMF device. In this thesis, a low cost and fully-customizable closed-loop controller is prototyped for DMF devices. This controller incorporates a calibration-free droplet position sensing technique capable of estimating the position of any type of droplet anywhere on a DMF device. The controller was simulated to evaluate its feasibility of improving the control of a droplet prior to prototyping. Simulation results demonstrate that unprecedented control over droplet position, velocity, and acceleration can be achieved with the proposed controller. In addition, these simulation observations revealed that pulse train actuation was feasible for controlling the incremental position, velocity, and acceleration of a droplet in a DMF device. Finally, a portable, low-cost closed-loop control system was built using off-the-shelf components. The proposed controller was integrated with a DMF device to experimentally demonstrate its potential of enhancing the control of droplet transport operations by sub-electrode droplet positioning. The prototyped controller can monitor and control the position of a droplet in real-time with an unparalleled degree of accuracy and repeatability. A final contribution was to optimize the fabrication process for a defect-free DMF device using basic microfabrication. The outcome of this research will allow for complete control over the droplet transport operation. This controller can also be used for more complex droplet operations including mixing and splitting droplets in DMF devices. In addition, the proposed closed-loop controller hardware can serve as a prototype development environment for promoting the commercialization of DMF technology.

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Attribution-NonCommercial-NoDerivatives 4.0 International