UBC Theses and Dissertations

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UBC Theses and Dissertations

Enhanced actuation and fabrication methods for integrated digital microfluidic systems Salem, Mohamed Yafia Okba


Introducing a practical digital microfluidic (DMF) platform has been always an important goal that can facilitate and broaden the use of DMF systems in various applications on a regular basis. In particular, a desired DMF platform may be the one which is fabricated easily and is also affordable, portable, battery powered, and user friendly. It should perform DMF operations reliably, accept mass-produced replaceable chips and can be readily integrated into a post processing station as well. Accordingly, the development of a practical DMF platform with these characteristics is the main target of this research. Specifically, the research has enhanced DMF systems through i) improved and novel actuation mechanisms, ii) cost-effective rapid prototyping techniques, and iii) full system integration. First, detailed experimental and numerical characterization of droplet morphology is performed to insinuate useful design and prototyping tips for enhanced DMF devices. Since droplet transport predominantly depends on the gap height, a major objective of the thesis is understanding the motion dynamics of a droplet at different gap heights. The characterization of the droplet behaviour in different regimes led to enhancing the actuation process in DMF systems. In addition, a variable gap size actuation (VGSA) mechanism is integrated into the DMF system to optimize DMF operations including droplet transport, splitting, dispensing and merging in real time. Consequently, the DMF operations can be performed reliably by adjusting the optimum operating conditions. Second, for rapid prototyping DMF chips, a new fabrication method is presented in which the electrodes are generated using screen printing. As a batch fabrication technique, the proposed screen printing approach is advantageous to the widely reported DMF electrode fabrication methods in terms of fabrication volume, time, and cost. In addition, a laser scribing technique is introduced as a low-cost, rapid and facile method for fabricating laser scribed graphene electrodes for DMF systems. Third, an ultraportable, low-cost, and modular DMF platform was successfully integrated with a smartphone that is used as a high-level controller. A colorimetric assay for pH value detection is introduced to demonstrate the performance of the device as a microscope and a post processing station.

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