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

Yu Zhao,Jozef Brcka,Jacques Faguet,Guigen Zhang

doi:10.3390/mi9060279

Abstract

Particle-particle interaction plays a crucial role in determining the movement and alignment of particles under dielectrophoresis (DEP). Previous research efforts focus on studying the mechanism governing the alignment of spherical particles with similar sizes in a static condition. Different approaches have been developed to simulate the alignment process of a given number of particles from several up to thousands depending on the applicability of the approaches. However, restricted by the simplification of electric field distribution and use of identical spherical particles, not much new understanding has been gained apart from the most common phenomenon of pearl chain formation. To enhance the understanding of particle-particle interaction, the movement of pearl chains under DEP in a flow condition was studied and a new type of tumbling motion with unknown mechanism was observed. For interactions among non-spherical particles, some preceding works have been done to simulate the alignment of ellipsoidal particles. Yet the modeling results do not match experimental observations. In this paper, the authors applied the newly developed volumetric polarization and integration (VPI) method to elucidate the underlying mechanism for the newly observed movement of pearl chains under DEP in a flow condition and explain the alignment patterns of ellipsoidal particles. The modeling results show satisfactory agreement with experimental observations, which proves the strength of the VPI method in explaining complicated DEP phenomena.

Highlights

As one of the most studied electro-kinetic phenomena, dielectrophoresis (DEP) has been recognized as having promising potential in manipulating small particles because it can be utilized to move either charged or non-charged particles
Using the free-body diagram shown in Figure 3a where Fx1, Fz1, Fx2 and Fz2 are the x and z components of the DEP force for particles 1 and 2, respectively, N is the normal contact force, and F0 is the sum of other forces for each particle, we can express the stable contact conditions as (1) Fx1 – N × cos θ = Fx2 + N × cos θ, (2) Fz1 + N × sin θ = F0 and Fz2 – N × sin θ = F0
Computational models based on the volumetric polarization and integration (VPI) method have been developed to elucidate the underlying mechanism for such movement using a static-force analysis approach and dynamic Arbitrary Lagrangian-Eulerian (ALE) approach

Summary

Introduction

As one of the most studied electro-kinetic phenomena, dielectrophoresis (DEP) has been recognized as having promising potential in manipulating small particles because it can be utilized to move either charged or non-charged particles. The applications of DEP mainly focused on separating different types of particles. Based on the difference in physical or dielectric property, particles are either guided into separate trajectories or pushed into different regions [1,2,3,4,5]. Due to significant progress made in the field of bio-manufacturing, researchers are paying more attention toward applying the DEP technique to pattern cells based on the induced interactions among cells. Cells of different types have been patterned into a liver-like tissue structure with designed electrodes [6,7]. Cell fusion has been successfully achieved based on the close attachment of cells in gap regions between parallel electrodes [8,9]

Methods

Results

Conclusion