Analytical Chemistry, 2007: Continuous-Flow Particle Separation by 3D Insulative Dielectrophoresis Using Coherently Shaped, DC-Biased, AC Electric Fields
Citation: Hawkins BG, Smith AE, Syed YA, Kirby BJ. Continuous-flow particle separation by 3D insulative dielectrophoresis using coherently shaped, DC-biased, AC electric fields, Analytical Chemistry, 79(19): pages 7291-7300. doi pdf
Abstract: We present the development of a continuous-flow, “dielectrophoretic spectrometer” based on insulative DEP techniques and three-dimensional geometric design. Hotembossed thermoplastic devices allow for high-throughput analysis and geometric control of electric fields via ridged microstructures patterned in a high width-to-depth aspect ratio (250:1) channel. We manipulate particles with dc-biased, ac electric fields and generate continuous output streams of particles with a transverse outlet position specified by linear and nonlinear particle mobilities. We show, with simulation and experiment, that characteristic shape factors can be defined that capture the effects of constrictions in channel depth and that modulating the angle of these constrictions changes the resulting local DEP force. Microdevices are fabricated with an insulative constriction in channel depth, whose angle of incidence with the direction of flow varies continuously across the channel width. The resulting electric field gradients enable demonstration of a dielectrophoretic spectrometer that separates particles and controls their transverse channel position.
Figures:
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- Figure 1. (a) 3D schematic of channel geometry. In (b), we define relevant geometric factors based on cross sections of the constriction region along the x-y and x-z planes.
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- Figure 2. Simulated particle streamlines (red line) for high and low ac to dc ratios. Background color table corresponds to electric field magnitude. Simulation parameters: phi-inlet ) 50 V, constriction ratio 10:1, particle radius 1 um.
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- Figure 3. Simulated and experimental values of Rd(Edc1/2) show good fit quality and expected dependence on r and γ. Multiplication of Rd by Edc1/2 emphasizes the dependence of Rd on factors determined by channel geometry (γ and r) and eliminates the dependence of Rd on Edc. Scatter in simulated data points is attributable to minor effects of constriction width. Applied (dc) electric fields are either 25 or 50 V/cm in simulation and experiment, electric field frequency is 1 kHz, and particle size is 2 um.
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- Figure 4. Varying the ac to dc ratio, R, increases transverse (y-axis) deflection. Simulated particle pathlines in (a) show no net particle deflection at a low ac to dc ratio. (b) shows particle deflection tangent to a curved constriction in channel depth, transverse to the direction of flow for a high ac to dc ratio. Simulated particle radius of 1 um. Electric field frequency is 1 kHz.
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- Figure 5. The 2-um particles passing the ridge with no net y-axis deflection. The 3-um particles show significant net y-axis motion as expected due to higher DEP mobility. Background color table in (a) and (b) represents Edc. Simulation parameters: phi-inlet ) 50 V, constriction ratio r ) 10:1, and R ) 15. Experimental parameters: phi-inlet ) 50 V, R ) 5. Electric field frequency is 1 kHz.