Direct Current Dielectrophoresis

House DL, Luo H (2011) Effect of direct current dielectrophoresis on the trajectory of a non-conducting colloidal sphere in a bent pore. Electrophoresis 32 3277-3285... 

Direct current dielectrophoresis (DC-DEP) Electrodeless dielectrophoresis Insulating post dielectrophoresis Insulator-based dielectrophoresis (iDEP) Streaming dielectrophoresis Trapping dielectrophoresis... 

A number of creative ways have been developed to create nonuniformities in an electric field using insulators. Initial efforts simply used prefabricated posts embedded in the channels [6] or rectangular [8], triangular [3], oil menisci [9], and other protrusions into the channels. The most common insulator materials are polymers utilized for photolithography or hot press microfahrication including polydimethylsiloxane PDMS and polymethyl methacrylate PMMA, or glass or silicone, which can be chemically etched or ablated [2]. A key attribute of direct current dielectrophoresis is that the electrodes supplying the electric field can be located more remotely on the lab-on-a-chip device. Electrodes can be immersed in fluid in chambers at either end of the test channel to avoid detrimental electrolysis reaction products [31]. Please see Pig. 1. 

Thwar PK, Linderman JJ, Bums MA (2007) Electrodeless direct current dielectrophoresis reconfigurable field-shaping oil barriers using. Electrophoresis 28 4572 581... 

Li M, Li SB. Li WH, Wen WJ. Alici G (2013) Continuous manipulation and separation of particles using combined obstacle- and curvature-induced direct current dielectrophoresis. ElectrophOTesis 34 952—960... 

Lynntech, Inc. s (Lynntech s), electrokinetic remediation of contaminated soil technology is an in situ soil decontamination method that uses an electric current to transport soil contaminants. According to Lynntech, this technology uses both direct current (DC) and alternating current (AC) electrokinetic techniques (dielectrophoresis) to decontaminate soil containing heavy metals and organic contaminants. A non homogeneous electric field is applied between electrodes positioned in the soil. The field induces electrokinetic processes that cause the controlled, horizontal, and/or vertical removal of contaminants from soils of variable hydraulic permeabilities and moisture contents. 

A phenomenon called dielectrophoresis has been used to pattern a variety of cell types on 2D substratesand more recently in 3D culture constructs. Unlike electrophoresis where charged species move in an applied electric field due to Coulombic forces (F = qE), dielectrophoresis capitalizes on the ability of a cell to become polarized when placed in an electric field. Dielectrophoresis is most often used in conjunction with dtemating current (AC) electric fields since AC fields eliminate electrophoretic movement, and have less physiological impact on cells than direct current (DC) fields. When a cell is placed in an AC field, the magnitude and polarity of the induced dipole depend on the frequency of the applied field and the conductivities of the cell and the surrounding medium, described by the equation... 

An alternative method is electrokinetic focusing, which uses a direct current electric field (at high voltages of 1 kV) to focus particles and Uquids into a narrow stream. Typically, the sample fluid stream is driven along the central channel of a cross-shaped channel. As the sample enters the intersection, three fluid streams meet and the sample stream is focused into narrow stream. Dielectrophoresis (DEP) can also be used for sample focusing. DEP is the movement of polarized particles in a nonuniform electric field. This phenomenon is explained further in the next section. The main advantage of this... 

Direct current (DC) dielectrophoresis (DEP) is an efficient means to move and thus separate particles or cells with the force of a stationary electric field. This is accomplished with a spatially nonuniform electric field shaped around insulative objects as obstacles in the path of the DC field. DC-DEP is then the induced motion of polarizable, dielectric objects of micron and smaller size, in a DC electric field that is modified by lab-on-a-chip geometry (or other means) to be spatially nonuniform. 

It is important to note the differences between electrophoresis and dielectrophoresis. Both technologies manipulate particles with their interaction to an applied electric field. In electrophoresis, a force is created on a charged particle by its attraction to a potential with the opposite polarity. The speed at which a particle moves through a stagnant fluid under apphed electrophoresis forces is proportional to its size and electrical charge. The applied electric field for electrophoresis is typically a direct-current (DC) signal. Dielectrophoresis utilizes a nonuniform electric field to induce a dipole or higher moments in a neutral particle. 

The magnitude and orientation of the induced dipole is a function of the dielectric properties of the particle and the surrounding medium. These induced moments in a nonuniform electric field can create a translational and/or rotational force on a particle. The applied electric field for dielectrophoresis can be either direct current or alternating current (AC), but it is typically the latter of the two. 

These effects are classified as either electrophoresis (EP) or dielectrophoresis (DEP). Whereas EP arises from the interaction of a fixed charge and an electric field, DEP results from the interaction of an induced charge and the spatial or temporal gradient of the electric field. In EP, direct current (DC) or low-frequency fields, usually homogeneous, are applied. On the other hand, in DEP, alternating current (AC) fields over a wide range of frequencies are used. 

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