Author ORCID Identifier
The phase angle between the imposed ac electric field and the oscillations in particle height is the key parameter governing the sign of interparticle force during two-dimensional directed assembly. The phase angle depends on a number of experimental parameters, including the frequency of the electric field and dispersing electrolytes. The origin of electrolyte dependence in this phase angle has been a mystery for a decade. Electrolyte dependence arises from polarization of the particle's diffuse layer, which affects the dynamic electrophoretic mobility of the particle. A full description of the magnitude and phase angle of the dynamic electrophoretic mobility was incorporated into a nonlinear integro-differential equation of motion for a 5.7 μm diameter particle suspended in 0.15 mM KOH, KCl, NaHCO3, NH4OH, and NaOH at frequencies between 5 and 1000 Hz. Integration of the equation revealed that the phase angles for a particle in KOH, NH4OH, and NaOH were smaller than the phase angles calculated for a particle in KCl and NaHCO3, which is consistent with previously published experiments. Although the phase angles for each electrolyte are spread over only ∼1°, the results cluster around 90°, which is the crucial boundary between particle aggregation (>90°) and separation (<90°). A family of curves of the oscillation in particle height collapsed to a master curve when the amplitude of motion was scaled with the product of the dynamic electrophoretic mobility and electric field strength. These results constitute the first a priori prediction of electrolyte-dependent motion of a particle near an electrode during ac polarization.
Physical Review E
Grant No. CBET 0730391; Achievement Rewards for College Scientists (ARCS) program; Bertucci graduate fellowship
National Science Foundation (NSF); PPG Foundation; The Carnegie Institute of Technology
©2013 American Physical Society
Wirth, Christopher L., "Electrolyte Dependence of Particle Motion Near an Electrode During Ac Polarization" (2013). Faculty Scholarship. 87.