The trajectory of a cylindrical particle driven by electrophoresis was transiently simulated as the particle moves through a 90°corner. A variety of system parameters were tested to determine their impact on the particle motion. The zeta potential, channel width, and particle aspect ratio were shown to have a minimal effect on the particle motion. Conversely, the initial vertical position of the particle and initial angle with respect to the horizontal had a significant impact on the particle motion. The presence of the 90°corner acts to reduce the initial distribution of angles to the vertical of 90°to less than 30°, demonstrating the possibility of using a corner as a passive control element as part of a larger microfluidic system. However, the reduction in angle is limited to the area near the corner posing a limitation on this means of control.

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In this paper, we investigate the use of inducedcharge electroosmosis (ICEO) as a means of providing localized flow control near conductive obstacles within bulk pressure-driven flow. In an experimental device, this ICEO flow was induced by an on/off switchable AC field applied across a section containing gold post(s). A simple numerical model, adapted from Levitan et al. (Colloids Surf A 267:122-132, 2005), was implemented and used to provide guidance for the design of the experimental devices. The induced flow was combined with an applied bulk pressure-driven flow to modify flow patterns. We have specifically observed single and multiple stream patterns downstream of the posts in the experimental devices, suggesting the presence of ICEO flow in the experimental system. The custom devices were obtained using a fabrication process that relies on relatively standard steps in the MEMS community, however, unlike other fabrication processes, it has been shown to create fully conductive posts with vertical sidewalls. Utilizing various combinations of number(s) of post(s), geometry and position, useful flow patterns can be created.

Expanding interest in enhanced subsurface natural resource recovery and carbon sequestration motivates study of reacting flows in porous media. In this work, we examine the case of reaction products that increase or decrease the viscosity of the fluid. Parallel reactant streams flow through porous media and react transversely along the centerline. We utilize a pore scale, finite element numerical method that couples the reaction with fluid flow through two arrangements of porous media at three Damkohler (Da) numbers and two viscosity conditions. When the product increases the fluid viscosity, the flow velocity is reduced and higher amounts of product are formed due to increased diffusion time. Conversely, reduced fluid viscosity leads to greater fluid velocity and lower amount of product formation. An exception is the viscous thinning case of high Peclet (Pe) number and high Da where an instability develops (in low Reynolds (Re) number flow) that enhances mixing between the reactants, resulting in increasing product formation.

The transient electrophoretic motion of a cylindrical particle through a relatively narrow channel is numerically simulated. The particle is initially located on the channel centerline and the initial angle of the particle to the channel centerline is varied with the objective of determining the effect on the particle trajectory. It is observed that the particles that begin aligned with or perpendicular to the channel centerline translate at a constant rate without rotation. The particles that begin at an intermediate angle (22.5 , 45 , and 67.5 ) translate along the channel while also translating perpendicular to the channel centerline and rotating in an oscillatory manner.