Number of publications on DEP for the period 2000–2010. (The estimate for 2010 is based on the 110 papers published up to 1 May 2010.)
Classification of DEP publications since 1995, in terms of whether their content mainly addresses theory, technology (Tech), or applications (Appl), expressed as a percentage of the total number of papers published. The trend for 2010 suggests that the theory (5%) and technology (18%) have matured sufficiently for efforts to be directed mainly toward publication of applications (77%).
(a) The lines of electric potential associated with a dipole of moment . (b) The potential generated outside an uncharged dielectric sphere, polarized by an imposed field , is identical to that produced by an induced dipole moment . The resultant potential, when this dipole potential is superposed onto that of the original field , must satisfy standard electrostatic boundary conditions at the surface of the sphere.
Schematic representation of how a nucleated cell can progressively be simplified to a homogeneous sphere of effective permittivity , given by Eq. (15) , that mimics the dielectric properties of the nucleated cell. The first step in simplification shown here is to represent the endoplasmic reticulum as a topographical feature that increases the effective capacitance of the nuclear envelope. The penultimate step represents the cell as a smeared-out cytoplasm surrounded by a membrane of complex permittivities and , respectively.
Solid line: DEP response modeled for a viable cell normalized against the DEP response for a sphere composed of the same electrolyte as the cell cytoplasm. With increasing frequency the cell’s DEP behavior approaches that of the conducting sphere, making the transition from negative to positive DEP at the “cross-over” frequency . Dashed line: DEP response for a larger cell (radius ). The cross-over frequency is sensitive to cell size, but the cross-over at the higher frequency is not sensitive to cell size (with all other dielectric factors remaining constant).
DEP response modeled for a viable cell for two values of the conductivity of the suspending medium. The DEP cross-over frequency increases with increasing medium conductivity, but the high-frequency cross-over is not sensitive to the medium conductivity.
Examples of axial and nonaxial multipoles constructed from evenly spaced point charges (Ref. 9 , pp. 176–183). The axial quadrupole is constructed by adding a moment to an original negative moment , a distance from an initial negative moment located at the origin. The axial octupole is created by repeating this exercise with two quadrupoles.
A spherical particle trapped (left) by quadrupole polynomial electrodes (Ref. 41 ) and (right) in a 3Dl eight electrode field cage (Ref. 46 ). The field acting along the axis of symmetry in these two electrode assemblies is zero, and so no dipole moment can be induced in the particles. Higher-order moments are induced and account for the DEP forces.
(a) The interdigitated, castelled, electrode design for observing both positive and negative DEP collection of particles (Ref. 74 ). Particles collecting in the diamond-shaped areas on the electrodes are driven there by hydrodynamic fluid flow (Ref. 80 ). (b) Viable yeast cells collecting by positive DEP into pearl chains, and (stained) nonviable cells collecting by negative DEP into triangular aggregations levitated above the electrode plane (e.g., Ref. 49 and 50 ).
A traveling-wave DEP junction, fabricated by laser ablation, for the separation or bringing together of different particles types (Ref. 102 ).
(a) The DEP funnel electrode design for focusing and concentrating particles in a flowing aqueous suspension (based on Ref. 108 ). This design has been exploited in a particle sorting device described by Kralj et al. (Ref. 110 ) and an on-chip molecular library screening device (Ref. 202 ). (b) An electrodeless DEP particle trap formed by a dielectric constriction, etched into a quartz plate, for creating local and large field gradients for DEP (Ref. 122 ). This design has been used to concentrate and pattern DNA (Refs. 122 and 123 ) and to design assays based on DNA hybridization (Refs. 124 and 125 ).
Patent number, date of grant, inventors, and title of U.S. patents granted in the field of DEP for the period January 2005–May 2010.
DEP manipulation of nanoparticles.
DEP characterization and manipulation of biological particles.
Performance, in terms of maximum sample flow rate and particle sorting rate, for various DEP particle sorting devices reported in the literature. Magnetic activated cell sorting and FACS are included for comparison.
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