Journal
LANGMUIR
Volume 28, Issue 39, Pages 13861-13870Publisher
AMER CHEMICAL SOC
DOI: 10.1021/la302402v
Keywords
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Funding
- Regional Government Junta de Andalucia [P09-FQM-4584]
- Spanish Government Ministry MEC [FIS2011-25161]
- National Natural Science Foundation of China [51075087]
- State Key Lab of Fluid Power Transmission and Control, Zhe Jiang University [GZKF-201107]
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We present dielectrophoresis (DEP) and electrorotation (ROT) measurements of gold-coated polystyrene microspheres as a function of frequency and for several electrolyte conductivities. Particle rotation was counterfield with a maximum rotation rate observed at a single characteristic frequency. Negative DEP was observed for frequencies lower than this characteristic frequency and positive DEP for signal frequencies higher than this. These experimental observations are in agreement with predictions for the force and torque on the induced dipole of a perfectly polarizable metal sphere. We present a theoretical model for this case, and good agreement is found for both ROT and DEP measurements if we take into account the viscous friction for a spherical particle near a wall. From the characteristic frequency for rotation, we obtain the capacitance of the electrical double layer at the electrolyte particle interface. Remarkably, no effect of induced charge electroosmosis around the particles can be inferred from DEP measurements.
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