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Microfluidic Devices for Control of Gaseous Environments
thesisposted on 01.02.2019 by Theodoros Christoforidis
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
Hydrogen sulfide (H2S) plays an important role as an intercellular and intracellular signaling molecule, yet its targets are not well understood. As a molecule it easily evaporates and it is hard to acquire stable concentration for in vitro studies, constituting a major problem for the field. Here we develop a microfluidic system that can provide consistent and controllable H2S levels in contrast to the current method of delivering large bolus doses to cells. Using that our devices enable to provide a stable concentration of H2S for up to 5 hours or, in addition, different H2S concentration profiles providing an easy means to control the H2S concentration. Our approach constitutes a unique method for H2S delivery for in vitro and ex vivo studies and is ideally suited to identify novel biological processes and cellular mechanisms regulated by H2S. Other applications of hydrogen sulfide gas in research are its in vivo administration to rodents for inhalation studies, and for the growth of nanostructures, such as MoS2 and WS2 as a precursor of sulfur. In order to implement research with hydrogen sulfide, tanks of different concentrations is needed. Storing and shipping hydrogen sulfide tanks can be dangerous as hydrogen sulfide is toxic at high concentrations. Here we show a microfluidic device that enables high volume hydrogen sulfide mixtures to be generated in situ without the need of premixed tanks. The device enables H2S mixtures of up to 60ppm to be generated at high flow rates in the range of 50-250 sccm. Finally, we show how vacuum pressure can be generated by just applying high gaseous pressure using a microfabricated converging diverging nozzle with two potential applications in pneumatic logic and bubble free filling of microfluidic devices.