Particle patterning using fluidics and electric fields

Electric-field manipulation of micro-particles in suspension can create patterns via a number of particle forces and fluid flows. These effects are assessed for their suitability for down-scaling to form nano-patterns such as may be incorporated into structured nano-composites. Consideration is given not only to the assembly of field-aligned chains or wires, but also to methods that can give cross-field assembly and even 2-D patterns or crystals. Dielectrophoresis is often the dominant driving force behind particle assembly, but other dipole-dipole interactions and also electrically-driven fluid flows are increasingly recognized as significant or dominant. Orientation of non-spherical particles in frequency-selectable directions is also possible. Estimates for the threshold field strengths required for using these effects to handle nano-particles are considered. Finally the use of media with modified permittivity to increase the field-induced forces or to optimize the selectivity of particle incorporation is discussed.