electrodes allow the handling of small bioparticles. The most used electrode geometries are isometric, polynomial, interdigitated, and crossbar. Isometric geometry is effective for particle manipulation with DEP but repelled particles do not collect in well defined areas and so separation into two homogeneous groups is difficult. Polynomial is a new geometry producing well defined differences in regions of high and low forces and so particles could be collected by positive and negative DEP. This electrode geometry showed that the electrical field was highest at the middle of the inter-electrode gaps. Interdigitated geometry comprises alternating electrode fingers of opposing polarities and is mainly used for dielectrophoretic trapping and analysis. Crossbar geometry is potentially useful for networks of interconnects. DEP-well electrodes These electrodes were developed to offer a high-throughput yet low-cost alternative to conventional electrode structures for DEP. Rather than use photolithographic methods or other microengineering approaches, DEP-well electrodes are constructed from stacking successive conductive and insulating layers in a laminate, after which multiple "wells" are drilled through the structure. If one examines the walls of these wells, the layers appear as interdigitated electrodes running continuously around the walls of the tube. When alternating conducting layers are connected to the two phases of an AC signal, a field gradient formed along the walls moves cells by DEP. DEP-wells can be used in two modes; for analysis or separation. In the first, the dielectrophoretic properties of cells can be monitored by light absorption measurements: positive DEP attracts the cells to the wall of the well, thus when probed with a light beam the well the light intensity increases through the well. The opposite is true for negative DEP, in which the light beam becomes obscured by the cells. Alternatively, the approach can be used to build a separator, where mixtures of cells are forced through large numbers (>100) of wells in parallel; those experiencing positive DEP are trapped in the device whilst the rest are flushed. Switching off the field allows release of the trapped cells into a separate container. The highly parallel nature of the approach means that the chip can sort cells at much higher speeds, comparable to those used by MACS and FACS. This approach offers many advantages over conventional, photolithography-based devices but reducing cost, increasing the amount of sample which can be analysed simultaneously, and the simplicity of cell motion reduced to one dimension (where cells can only move