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Electrophoresis ; 31(22): 3634-41, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21077235


Here we present a scheme to separate particles according to their characteristic physical properties, including size, charge, polarizability, deformability, surface charge mobility, dielectric features, and local capacitance. Separation is accomplished using a microdevice based on direct current insulator gradient dielectrophoresis that can isolate and concentrate multiple analytes simultaneously at different positions. The device is dependent upon dielectrophoretic and electrokinetic forces incorporating a global longitudinal direct current field as well as using shaped insulating features within the channel to induce local gradients. This design allows for the production of strong local field gradients along a global field causing particles to enter, initially transported through the channel by electrophoresis and electroosmosis (electrokinetics), and to be isolated via repulsive dielectrophoretic forces that are proportional to an exponent of the field gradient. Sulfate-capped polystyrene nano and microparticles (20, 200 nm, and 1 µm) were used as probes to demonstrate the influence of channel geometry and applied longitudinal field on separation behavior. These results are consistent with models using similar channel geometry and indicate that specific particulate species can be isolated within a distinct portion of the device, whereas concentrating particles by factors from 10(3) to 10(6).

Eletroforese/instrumentação , Eletroforese/métodos , Técnicas Analíticas Microfluídicas/instrumentação , Técnicas Analíticas Microfluídicas/métodos , Modelos Químicos , Eletro-Osmose/instrumentação , Eletro-Osmose/métodos , Microesferas , Nanopartículas , Tamanho da Partícula , Poliestirenos/química , Propriedades de Superfície
Electrophoresis ; 30(9): 1441-8, 2009 May.
Artigo em Inglês | MEDLINE | ID: mdl-19425000


Insulator-based dielectrophoretic separation of small particles in a sawtooth channel is studied in the limit of dilute concentration. Pathlines for the movements of infinitesimal particles are constructed and the geometric changes of these pathlines are used to establish the criterion for blocking and trapping particles with different physical properties. The sharp corners of the sawtooth channel create much stronger dielectrophoretic force than channels with smooth corners for blocking particle movements. Particle blocking and trapping depend on particle properties and the geometry of the device. It is shown that once the channel geometric aspect ratios are specified, the blocking criterion depends on only a single dimensionless parameter C defined in terms of the particle mobility ratio (dielectrophoretic versus electrokinetic), the applied voltage and the spacing between the teeth. Selective blocking and trapping of particles can be realized by varying the geometry of the channel progressively. High-resolution separation can be achieved by tuning the differential in the parameter C to a desired level.

Fenômenos Químicos , Eletroforese/instrumentação , Modelos Teóricos , Campos Eletromagnéticos , Tamanho da Partícula