(6c) Probing the Basset Force Acting On a Particle Undergoing AC Electrophoresis
AIChE Annual Meeting
2011
2011 Annual Meeting
2011 Annual Meeting of the American Electrophoresis Society (AES)
Advances In Electrokinetics and Electrophoresis - Fundamentals
Monday, October 17, 2011 - 9:06am to 9:24am
The electrophoretic motion and related assembly of colloidal particles near an electrode is important to a variety of applications including the preparation of colloidal crystals,1 the separation of colloids,2,3 and the high throughput evaluation of electrocatalysts4,5. With the aid of Total Internal Reflection Microscopy (TIRM), we studied high frequency (1 kHz - 100 kHz) AC electrophoresis of a single particle normal to an electrode. Surprisingly, the particle adopted a position either closer to- or farther from the nearby wall even when the driving force was oscillatory. The position dependence in the hydrodynamic mobility of the particle suffices to explain apparent repulsion from the electrode, but attraction toward the electrode had remained a mystery for a number of years.6 Recently, these experiments and new modeling suggested that the Basset force plays a role in this unexpected behavior. The Basset (or “history”) force, results from the transient development of the particle’s momentum boundary layer during unsteady particle motion. TIRM’s capability of probing weak, ~kT scale interaction energies is ideal for investigation of this hydrodynamic effect. The evidence showing the significance of including the Basset force is the subject of this presentation.
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