Dielectrophoretic microfluidics

Dielectrophoresis (DEP), the term coined by Pohl [1, 2], is the motion of an object under forces resulting from electric field gradients. The applications of DEP are based on differentiation of dielectric and conducting properties of objects to allow their separation and identification. DEP has been demonstrated to be useful for separating polydisperse particle suspensions into homogeneous subpopulations, manipulating and concentrating bio logically relevant molecules, distinguishing dead and living cells or ill and healthy cells, assembling carbon nanotubes, etc. Numerous books and reviews address the fundamentals and various applications of DEP: Pohl [2], Pethig [3], Mizuno and Washizu [4], Jones [5], Fuhr et al. [6], Pethig [7], Pethig and Markx [8], Koch et al. [9], Gascoyne and Vykoukal [10], Hughes [11, 12], Morgan and Green [13], Burke [14], and Gonzalez and Remcho [15]. Early experiments on DEP were conducted on simple electrode configurations, typically pin-plate, pin-pin, and wire-wire. Microfabrication technologies borrowed from the semiconductor industry facilitate the fabrication of novel and more capable dielectrophoretic microfluidic systems. For example, micro-and nanoscaled electrodes can produce high fields of up to several kV mm^-1 from the application of only a few volts. Precisely contoured arrays of thousands or millions of field-shaping structures can be patterned and replicated economically. Moreover, undesired effects like electro-convection and Joule heating can be suppressed in tiny microfluidic devices.