Numerical Investigation of DC Dielectrophoretic Particle Transport

In this paper, we investigate the mechanism of two dimensional DC dielectrophoresis (DEP) using a hybrid immersed interface-immersed boundary method where both electric and hydrodynamic forces are obtained with interface-resolved approach instead of point-particle method. Immersed interface method is employed to predict DC electric field in a fluid media with suspended particles while immersed boundary method is used to study particle transport in a fluid media. The Maxwell stress tensor approach is adopted to obtain dielectrophoretic force. This hybrid numerical scheme demonstrates the underlying physics of positive and negative dielectrophoresis, and explains their contribution in particle assembly with consideration of size, initial configurations and electrical properties of particles as well as fluid media. The results show that the positive DEP provides accelerating motion while negative DEP provides decelerating motion depending on the electrode configurations and initial particle positions. The results also show that the local nonuniformity in electric field induced by the suspended particles guides the particles to form stable chain. Both positive and negative DEP can contribute in the process of particle assembly formation based on the properties of particles and fluid media. This hybrid immersed interface-immersed boundary scheme could be an efficient numerical tool for understanding fundamental mechanism of dielectrophoresis as well as designing and optimization of DEP based microfluidic devices.

Download Full-text

Modeling and Simulation of Dielectrophoretic Particle Assembly

Volume 7: Fluids and Heat Transfer, Parts A, B, C, and D ◽

10.1115/imece2012-85768 ◽

2012 ◽

Author(s):

Mohammad Robiul Hossan ◽

Prashanta Dutta

Keyword(s):

Electric Field ◽

Stress Tensor ◽

Immersed Boundary Method ◽

Applied Electric Field ◽

Immersed Boundary ◽

Particle Assembly ◽

Immersed Interface ◽

Boundary Method ◽

Fluid Media ◽

A Chain

In this paper, we present a comprehensive study of dielectrophoretic particle assembly using hybrid immersed interface-immersed boundary method where both dielectrophoretic and hydrodynamic forces are evaluated with interface resolved approach instead of point-particle method. Immersed interface method is employed to capture physics of electrostatics in a fluid media with embedded particles, while immersed boundary method is used to study hydrodynamics with rigid and/or flexible immersed boundaries. Unlike existing studies, dielectrophoretic force is obtained using Maxwell’s stress tensor; a comparative study between Maxwell stress tensor and effective dipole moment methods are presented. This hybrid method is employed to demonstrate the dielectrophoretic particle assembly for both similar and dissimilar particles. In a fluid media, the similar particles form a chain parallel to the applied electric field, while the dissimilar particles form a chain perpendicular to the applied electric field. These results are consistent with the recent experimental observations.

Download Full-text

Parametric Study of Dielectrophoretic Interactive Motion of Particles

ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2015-48343 ◽

2015 ◽

Author(s):

Mohammad Robiul Hossan ◽

Matthew J. Benton ◽

Prashanta Dutta ◽

Robert Dillon

Keyword(s):

Electrical Conductivity ◽

Electrical Properties ◽

Electric Field ◽

Free Particle ◽

Immersed Boundary ◽

Label Free ◽

Navier Stokes Equation ◽

Immersed Interface Method ◽

Immersed Interface ◽

Fluid Medium

Dielectrophoresis (DEP) has become one of the most popular mechanisms for label free particle manipulations and transport in microfluidics. The efficacy of this mechanism is greatly dependent on the understanding and control of DEP interactive motion among particles. In this study, we performed a systematic investigation to understand the effect of particles size and electrical properties on DC DEP interactions among particles using in-house hybrid immersed boundary – immersed interface numerical method. Immersed boundary method is employed to predict flow field and immersed interface method is used to simulate electric field. The numerical model utilizes Maxwell’s stress tensor to obtain DEP forces, while solving transient Navier-Stokes equation it determines the hydrodynamic interaction between each of the particles and the fluid containing them. By varying the number of particles as well as the particles’ size, electrical properties and initial orientations, a number of possibilities were considered. Results indicate that the particles with similar electrical conductivities attract each other and tend to align themselves parallel to the external electric field regardless of sizes. If electrical conductivity of particles is lower than that of the fluid medium then the particle-particle interactions is caused by the negative DEP. If electrical conductivity of particles is higher than that of the fluid medium then the interactive motions of particle is attributed to the positive DEP. On the other hand, electrically dissimilar particles still attract each other but tend to align perpendicular to the electric field. Both negative and positive DEP contributes in interactions between electrically dissimilar particles. Numerical simulation also shows that the identical sized particles move at the same speed during interaction. In contrast, smaller particles moves faster than the larger particle during the interactions. This study explains the effect of size and electrical properties on DEP interactive motions of particles and can be utilized to design microfluidic devices for DEP particle manipulations.

Download Full-text

Dielectrophoretic Interactions and Chaining of Ellipsoidal Particles in a Microchannel

Volume 7: Fluids Engineering ◽

10.1115/imece2016-67247 ◽

2016 ◽

Author(s):

Mohammad Robiul Hossan ◽

Partha P. Gopmandal ◽

Prashanta Dutta ◽

Robert Dillon

Keyword(s):

Electric Field ◽

Stress Tensor ◽

Applied Electric Field ◽

Immersed Boundary ◽

Immersed Interface Method ◽

Immersed Interface ◽

Ellipsoidal Particles ◽

Clockwise Direction ◽

A Chain ◽

Final Orientation

Recent experimental studies report that the understanding of dielectrophoretic (DEP) interactions and chaining of irregularly shaped particles, particularly ellipsoidal shaped particle, are critical for development of smart materials, engineered biological cellular structure and tissue formation. This paper presents a comprehensive numerical investigation of direct current (DC) dielectrophoretic (DEP) chaining and interactions of ellipsoidal particles in a microchannel. A hybrid immersed boundary-immersed interface method is employed to explain the fundamental mechanism of DEP interactions and chaining of ellipsoidal particles. Electric field equations are solved by the immersed interface method while the immersed boundary method is employed to solve fluid equations. The DEP force was estimated by using Maxwell’s stress tensor (MST) and the Cauchy stress tensor (CST) was employed to evaluate hydrodynamic force. The results show that the electrical properties of fluid and particles are the main deciding factor on the final orientation of ellipsoidal particles. However the size, shapes and initial positions and orientations have significant impact on interaction time spans. Results also show that if the interacting particles are electrically similar i.e. having same electrical conductivity then they always form a chain parallel to the applied electric field, otherwise they form a chain which is orthogonal to the applied electric field. In parallel chaining, particles rotate in a clockwise direction, while in orthogonal (to the applied electric field) chaining, particles rotate in counter-clockwise direction to reach to the final orientation. Results also indicate that the ellipsoidal particles go through an electro-orientation process if initially the major axis of the ellipsoidal particles is not in perfect alignment with the applied electric field. The electro-orientation and DEP interaction take place simultaneously to reach to final stable orientation. This study provides critical insight on the mechanism of DEP interactions and chaining of ellipsoidal shaped particles.

Download Full-text

Simulation of Fluid-Structure and Fluid-Mediated Structure-Structure Interactions in Stokes Regime Using Immersed Boundary Method

The Scientific World JOURNAL ◽

10.1155/2014/782534 ◽

2014 ◽

Vol 2014 ◽

pp. 1-13

Author(s):

Masoud Baghalnezhad ◽

Abdolrahman Dadvand ◽

Iraj Mirzaee

Keyword(s):

Equilibrium State ◽

Stokes Flow ◽

Immersed Boundary Method ◽

Deformable Body ◽

Fluid Motion ◽

Immersed Boundary ◽

Immersed Interface Method ◽

Computational Point ◽

Fluid Structure ◽

Boundary Method

The Stokes flow induced by the motion of an elastic massless filament immersed in a two-dimensional fluid is studied. Initially, the filament is deviated from its equilibrium state and the fluid is at rest. The filament will induce fluid motion while returning to its equilibrium state. Two different test cases are examined. In both cases, the motion of a fixed-end massless filament induces the fluid motion inside a square domain. However, in the second test case, a deformable circular string is placed in the square domain and its interaction with the Stokes flow induced by the filament motion is studied. The interaction between the fluid and deformable body/bodies can become very complicated from the computational point of view. An immersed boundary method is used in the present study. In order to substantiate the accuracy of the numerical method employed, the simulated results associated with the Stokes flow induced by the motion of an extending star string are compared well with those obtained by the immersed interface method. The results show the ability and accuracy of the IBM method in solving the complicated fluid-structure and fluid-mediated structure-structure interaction problems happening in a wide variety of engineering and biological systems.

Download Full-text

An AC Dielectrophoretic Trap for Cellular Assembly

Volume 7B: Fluids Engineering Systems and Technologies ◽

10.1115/imece2013-64819 ◽

2013 ◽

Author(s):

Mohammad Robiul Hossan ◽

Robert Dillon ◽

Prashanta Dutta

Keyword(s):

Mathematical Model ◽

Electric Field ◽

Immersed Boundary ◽

Computational Domain ◽

Point Dipole ◽

Dielectrophoretic Force ◽

Immersed Interface Method ◽

Immersed Interface ◽

Maxwell Stress Tensor ◽

Ac Electric Field

A mathematical model and numerical techniques are proposed to study AC electric field induced cellular assembly in a microfluidic device. In the mathematical model, the Maxwell stress tensor is used to calculate the dielectrophoretic force acting on particles by considering the physical effect of particles in the computational domain. Thus, the proposed model eliminates the approximations used in point dipole methods for calculating dielectrophoretic force. The numerical method is based on hybrid immersed boundary-immersed interface methods. An immersed boundary method is used for the fluid equations and particle transport, while an immersed interface method is employed to obtain the AC electric field in a fluid media with suspended particles. For the immersed interface method, an iterative algorithm is developed to solve the complex Poisson equation using a real variable formulation. The decoupled algorithm for solving complex differential equations converges rapidly. The hybrid method is used to investigate the physics of AC dielectrophoresis in a cross-channel junction. The numerical results show that with proper design and appropriate selection of applied potential and frequency, global electric field minima can be obtained to facilitate multiple particle trapping by exploiting the mechanism of negative dielectrophoresis.

Download Full-text