Design of a microfluidic disc

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Supervisor:
Dr. Sántha Hunor
Department of Electronics Technology

The aim of my thesis is to design and construct a centrifugal microfluidic disc and an appropriate actuating device. The microfluidic disc's intended use is to measure a blood chemistry parameter, based on photometric principles. The designed structure on the disc is able to perform the sample handling; it separates serum from whole blood by the means of centrifugation, and mixes the separated serum with the pre-filled reagent. Here a reaction occurs, which causes a change in the absorption spectrum of the solution. The change in the absorption at a given wavelength can be measured with a monochromatic light source and a phototransistor.

As the first step of my work I performed research on the properties and functions of the available centrifugal microfluidic devices. I investigated the role and parameters of the used structures (valves, channels). By analysing the available production technologies I selected the material for my own system.

I used CO2 laser fabricated PMMA sheets. Laser ablation was used as a subtractive manufacturing method. I deeply examined the machining properties of laser ablation, then selected a suitable surface treatment method to reduce the surface roughness on the disc. I performed measurements on the surface roughness before and after etching the disc.

By applying modifications to a CD-drive I created a device with controllable rotational frequency. This device is used to spin the disc based on a predefined RPM-protocol. The controller is realized on an Arduino Mega board.

I combined a nearly monochromatic LED and a phototransistor to create a photometric measurement unit. With a uniquely designed stroboscopic lighting I examined the fluid movements on the spinning disc.

Concluding my thesis I summarized the design and construction works performed, as well as recommendations for future development or modifications.

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