Abstract
We present a comprehensive comparison of dielectrophoretic (DEP) crossover frequency of single particles determined by various experimental methods and theoretical models under the same conditions, and ensure that discrepancy due to uncertain or inconsistent material properties and electrode design can be minimized. Our experiment shows that sulfate- and carboxyl-functionalized particles have higher crossover frequencies than non-functionalized ones, which is attributed to the electric double layer (EDL). To better understand the formation of the EDL, we performed simulations to study the relationship between initial surface charge density, surface ion adsorption, effective surface conductance, and functional groups of both functionalized and nonfunctionalized particles in media with various conductivities. We also conducted detailed simulations to quantify how much error may be introduced if concurrent electrohydrodynamic forces, such as electrothermal and electro-osmotic forces, are not properly avoided during the crossover frequency measurement.
Highlights
Dielectrophoresis (DEP) is a phenomenon in which suspended dielectric particles are polarized and moved relative to the medium by a non-uniform alternating current (AC) or direct current (DC) electric field [1,2,3]
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We present a comprehensive study to elucidate the effect of concurrent electrohydrodynamic forces on the measurement of DEP crossover frequency using the recently developed experimental phase-shift method and numerical volumetric-integration model
Summary
Dielectrophoresis (DEP) is a phenomenon in which suspended dielectric particles are polarized and moved relative to the medium by a non-uniform alternating current (AC) or direct current (DC) electric field [1,2,3]. The magnitude and direction of the AC DEP force depend on the electric field gradient, the applied frequency, and the polarizability of the particle, which depends on the dielectric properties of the particle and the medium. The crossover frequency, at which the DEP force reverses its direction, is of particular importance since it is a key characteristic that enables particle/cell separations [20,21] and contains critical information on the mechanisms of the electric double layer (EDL) [22]. Experimental results reported by different groups using different methods still show a certain discrepancy, especially for larger particles and/or a more conductive medium [23,29,30]. One major challenge of csiogmnifpicaanrtindigscrdepiffanecryeins talesoxpobesreirmveednbteatwl emeneetxhpoerdimseanntadl retshueltos raentdictahel mtheoordyeblasseids othn at the results
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