Development and optimization of microfabrication processes for capillary driven microfluidic valves

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Microfluidic capillary systems automate, miniaturize and expedite the laboratory procedures without any needfor active mechanical elements such as external pumps or valves. The technology has enabled Sensoreal, thesupporting company, to develop self-contained, and self-powered microfluidic cartridges that perform rapidblood tests to measure multiple protein biomarkers using a few drops of blood. Currently, due to the laminarflow behaviour of the capillary microfluidic systems, the rehydrated reagents do not uniformly spread acrossthe reservoirs of interest and as a result there is over 80% waste of the volume of the sample and the reagentused to perform the assay. Also the current issue makes the footprint of the microchips bulky (5 cm x 10 cm).The proposed research project plans to enhance the performance of the microfluidic capillary systems byintroducing a capillary valve for the slow release of the dry reagents (SRDR). The valving system could then beintegrated to the Sensoreal's capillary circuits for making cartridges consuming much less sample and reagentsvolume and could further miniaturize the footprint of the cartridges made.In this context, our ultimate goal is to develop and optimize microfabrication processes including plasmasynthesis, etching and functionalization processes to fabricate SRDR valves made in silicon. A particularattention will be paid to the optimization of the plasma etching processes (gaz ratio, temperature) to minimizethe formation of any hydrophobic passivation layer on the surface of the Si channels, while keeping themicrofluidic sidewall profiles as vertical as possible (anisotropic etching). Different techniques will be used tofurther oxidize the surface of the microchannel to enhance their hydrophilicity as required for the operation ofthe SRDR. These techniques will include plasma-based functionalization and/or plasma-based thin filmdeposition. If successful, the solution will give Sensoreal more opportunities to increase their technologyportfolio and have future market share especially in price sensitive countries.