Transport Of Passive And Active Scalars In Microfluidics: Device Design For Solute Delivery To Rat Hippocampal Neurons, Improved Analytical Expressions For Electrokinetic Transport In Porous And Charged Layers, And Electrokinetic Interrogation Of Perfluorinated Ionomeric (Nafion) Thin Films
First, we outline the design, modeling, and fabrication of a glass-polymer microdevice for the spatio-temporal delivery of neutral solutes to coherently grown rat hippocamapal neurons. In the design and modeling of this device, we incorporate biological constraints of the neurons and relate them to engineering parameters like solute delivery/clearing time and the fluid shear incumbent on the neurons. Next, we describe the effects of porous and charged interfaces on transport in microdevices. Porous and charged interfaces exhibit a fixed charge in a region of increased mechanical resistance. I will present approximate analytical relations to describe forces (gradients of pressure and electrical potential) and fluxes (mass and current) in a microfluidic device coated with porous and charged layers. These relations improve upon existing expressions in the literature. We demonstrate the efficacy of our results by comparison with numerical values. Finally, we execute streaming potential, conductivity, and other measurements on Nafion polymer films in a parallel-plate cell. I show that the charging of Nafion is relatively independent of pH, but that electrokinetic outputs are strongly dependent on the ionic strength of solution. These results are interpreted using our approximate analytical expressions predicting forces and fluxes.
microfluidics; electrokinetics; fluid mechanics
Abruna, Hector D; Koch, Donald L
Ph. D., Mechanical Engineering
Doctor of Philosophy
dissertation or thesis