Scanning Dielectrophoresis for the Directed-Assembly and Non-Contact Manipulation of Colloidal Particles

The scanning dielectrophoresis system consists of a pair of microneedles connected to a waveform generator of arbitrary ac electric fields. Consequently, our scanning method is able to place and move the strong electric field spot between the electrode tips anywhere, just as optical tweezers have done the focus of light beam. In this paper, we demonstrate non-contact manipulations unique to our scanning method. We also propose that the use of the frequency modulated electric field provides a novel way for one-step assay of crossover frequency in dielectrophoresis of a single colloid, which has been validated by the scanning method. Furthermore, the dielectrophoretic assembly forms a micron-film with stripe pattern of single-walled carbon nanotube bundles surrounded by polymer beads, similarly to depletion induced clusters in binary colloids.