Elucidating the DEP phenomena using a volumetric polarization approach with consideration of the electric double layer

Abstract

Dielectrophoretic (DEP) phenomena have been explored to great success for various applications like particle sorting and separation. To elucidate the underlying mechanism and quantify the DEP force experienced by particles, the point-dipole and Maxwell Stress Tensor (MST) methods are commonly used. However, both methods exhibit their own limitations. For example, the point-dipole method is unable to fully capture the essence of particle-particle interactions and the MST method is not suitable for particles of non-homogeneous property. Moreover, both methods fare poorly when it comes to explaining DEP phenomena such as the dependence of crossover frequency on medium conductivity. To address these limitations, the authors have developed a new method, termed volumetric-integration method, with the aid of computational implementation, to reexamine the DEP phenomena, elucidate the governing mechanism, and quantify the DEP force. The effect of an electric double layer (EDL) on particles' crossover behavior is dealt with through consideration of the EDL structure along with surface ionic/molecular adsorption, unlike in other methods, where the EDL is accounted for through simply assigning a surface conductance value to the particles. For validation, by comparing with literature experimental data, the authors show that the new method can quantify the DEP force on not only homogeneous particles but also non-homogeneous ones, and predict particle-particle interactions fairly accurately. Moreover, the authors also show that the predicted dependence of crossover frequency on medium conductivity and particle size agrees very well with experimental measurements.

Optoelectrokinetics-based microfluidic platform for bioapplications: A review of recent advances

“…Recently, a model for the self-rotation of cells in a DEP field was reported and experimentally validated. [122][123][124] Nevertheless, it did not reveal the correlation between the intrinsic properties of cells and nonuniform and nonrotational fields. Also, although both a DEP and an ODEP field rely on a nonuniform electric field, an ODEP field generally relies on a much more nonuniform electric field than a DEP field, which can be seen from our previous simulation results.…”

Elucidating the Mechanisms of Two Unique Phenomena Governed by Particle-Particle Interaction under DEP: Tumbling Motion of Pearl Chains and Alignment of Ellipsoidal Particles

“…In our previous paper, we have developed a new method based on volumetric polarization to quantify the DEP force exerted on particles [ 13 ]. In this paper, we expand this VPI method to quantify the electrostatic potential energy and torque of particles.…”

“…Aside from the forces considered above, the particle is also subject to DEP force [ 13 ], gravitational force, and buoyancy force. These forces are outlined in the equations below.…”

“…To explain reasons that cause this unique phenomenon, we adopted two types of modeling approaches called the static force analysis based on volumetric polarization and integration (VPI) method and the coupled ALE-VPI method. The VPI method is our newly developed method which intends to overcome the limitations of both the point-dipole method and the MST method [ 13 ]. The point-dipole method neglects the distortion effect of volumetric polarization of particles, which makes it less accurate when the electric field is highly non-uniform.…”

Dielectrophoretic Crossover Frequency of Single Particles: Quantifying the Effect of Surface Functional Groups and Electrohydrodynamic Flow Drag Force

“…On the theoretical side, the prevailing dipole model treats particles as point dipoles and does not consider the volume effect nor the distortion of the electric field caused by the particles [ 3 ]. The more comprehensive Maxwell stress tensor (MST) considers the effects mentioned above, but cannot predict the surface ion adsorption and the forming of an electric double layer (EDL), although an effective surface conductance can be assigned to account for the EDL effect [ 30 , 31 ]. More recently, Zhao et al propose a new volumetric-integration (VI) method, which addresses those limitations and applies to particles of various sizes and shapes [ 31 , 32 ].…”