Non-vanishing ponderomotive AC electrophoretic effect for particle trapping...

We present here a study on overlooked aspects of alternating current (AC) electrokinetics—AC
electrophoretic (ACEP) phenomena. The dynamics of a particle with both polarizability and net
charges in a non-uniform AC electric trapping field is investigated. It is found that either
electrophoretic (EP) or dielectrophoretic (DEP) effects can dominate the trapping dynamics,
depending on experimental conditions. A dimensionless parameter gamma is developed to predict the
relative strength of EP and DEP effects in a quadrupole AC field. An ACEP trap is feasible for
charged particles in ‘salt-free’ or low salt concentration solutions. In contrast to DEP traps, an
ACEP trap favors the downscaling of the particle size.