Transient Electrophoretic Motion of Cylindrical Particles in Capillaries

Abstract

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.

Transient simulations of the electrophoretic motion of a cylindrical particle through a 90° corner

“…The Dashed lines indicate h = 90°and -90°which is when a particle would be aligned with the vertical centerline cases with positive initial angles translate upwards in the Y* direction, while the negative initial angle cases translate downwards in the -Y* direction. This correlates to earlier work on translation in a straight channel in which the flow around an angled particle causes it to translate in the direction its leading edge is translating (Davison and Sharp 2007). This previous observation also explains the trajectory of the particles in the vertical section.…”

“…Similarly, the positive initial angle particles are oriented toward the + X* + Y* quadrant (after the corner), but at an angle closer to vertical so the motion in the + X* direction is not as pronounced. The trajectory plot also indicates that the particle moves slower as its angle is increased as a result of the increased drag from a larger area exposed to the flow (Davison and Sharp 2007). The angular motion of the particle is shown in Fig.…”

“…A cylindrical particle translating horizontally through a straight channel has been shown to move in an oscillatory manner in both vertical displacement and angle, with the nature of the motion dependent on the initial position and angle of the particle (Davison and Sharp 2007). Previous work with corners and junctions in microfluidic systems have largely focused on fluid-only systems (Slentz et al 2002;Zimmerman et al 2006).…”

dc electrokinetic transport of cylindrical cells in straight microchannels

“…As a result, a transient simulation accounting for the particle's translation and rotation is necessary to capture the essential physical process of the electrokinetic transport of cylindrical particles. Davison and Sharp 27,28 implemented a transient numerical model to predict the electrokinetic motion of a cylindrical particle through a tube and an L-shaped microchannel. 29 It was predicted that a cylindrical particle could experience an oscillatory motion in a straight channel 28 and an L-shaped channel could be used to control the orientation of cylindrical particles.…”

“…Davison and Sharp 27,28 implemented a transient numerical model to predict the electrokinetic motion of a cylindrical particle through a tube and an L-shaped microchannel. 29 It was predicted that a cylindrical particle could experience an oscillatory motion in a straight channel 28 and an L-shaped channel could be used to control the orientation of cylindrical particles. 29 However, the aforementioned numerical studies did not examine the dielectrophoretic ͑DEP͒ effect on the particle transport, and the numerical predictions have not been verified by experiments.…”