Development of Functionalized Semipermeable Membranes for Microfluidic Separations

Gelwicks, Melissa J.
Microfluidic devices, which can affect a complex series of separations using small sample sizes, may fulfill a need for performing rapid, sensitive and efficient separations of biological samples for medical diagnostics. Silica gel is typically used for separations, but is not appropriate for very small-scale use; it tends to clog microscale channels, and silica membranes have been found to fail catastrophically after short experimental use. This project focused on the development of membranes that can be synthesized with varying permeabilities in order to perform size-based separations. Ultimately, the goal will be to include functional groups in the membranes with affinities for certain biological molecules. My work began with learning the techniques for fabricating microfluidic devices having channels of varying depths. Polymerization of acrylamide with amine-reactive monomers in situ in shallow regions of the devices was followed by reaction with functionalized amines, and then sodium silicate to produce hybrid membranes including organic molecules and silica. These hybrid membranes were tested for their abilities to trap small organic molecules while allowing the passage of low molecular weight buffer molecules by introducing buffered solutions of charged organic dyes that were then electrophoretically directed towards the membranes.
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