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Numerical modeling of dielectrophoresis
KTH, School of Engineering Sciences (SCI), Mechanics.
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

We investigate the dielectrophoretic separation of microparticles. Two different models are formulated in two characteristic time scales. The first model mainly accounts for the orientation behavior and rotational motion of non-spheric microparticles. The concept of effective charge is suggested to calculate the finite size non-spheric particles. It is combined with the fluid particle dynamics method to calculate hydrodynamic as well as dielectrophoretic forces and torques. The translational motion and the particle-particle interaction are calculated also, but they take much longer time to be observed due to the different time scales of the rotational and translational motions By viewing the particle as spheres, the second model focus on the translational motion of spheres. The hydrodynamic force between particles and particle-particle electrostatic interactions are also taken into account. We check the relative magnitude ratio between these forces in order to determine the importance of these forces. To predict and guide the design of experimental dielectrophoretic separation, two numerical applications are carried out. The first calculation suggests optimum patterns to improve the trapping efficiency of E.coli. cells by applying superimposed AC electric fields. The second calculation finds out the mobility and separation rate of particles which differs in size and electric properties by a multi-step trapping-releasing strategy.

Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , viii, 34 p.
Series
Trita-MEK, ISSN 0348-467X ; 2006:14
Keyword [en]
dielectrophoresis, orientation of rotation, fluid particle dynamics, microparticle, molecular dynamics, hydrodynamics, particle-particle interaction, superimposed, mobility
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-4014OAI: oai:DiVA.org:kth-4014DiVA: diva2:10394
Presentation
2006-06-06, Sal D3, KTH, Lindstedtsvägen 5, Stockholm, 13:00
Opponent
Supervisors
Note
QC 20101118Available from: 2006-06-01 Created: 2006-06-01 Last updated: 2010-11-18Bibliographically approved
List of papers
1. Simulation of dielectrophoresis of finite size particles
Open this publication in new window or tab >>Simulation of dielectrophoresis of finite size particles
(English)Article in journal (Refereed) Accepted
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-5868 (URN)
Note
QC 20101118Available from: 2006-06-01 Created: 2006-06-01 Last updated: 2010-11-18Bibliographically approved
2. Simulation of dielectrophoretic motion of microparticles using a molecular dynamics approach
Open this publication in new window or tab >>Simulation of dielectrophoretic motion of microparticles using a molecular dynamics approach
2006 (English)In: 4th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM2006, 2006, 1-10 p.Conference paper, Published paper (Refereed)
Abstract [en]

We model and simulate dielectrophoresis of microscale particles using the finite element method. A soft sphere system molecular dynamics model is presented, which solves a set of equations for the motion of every particle. The model couples most of the significant forces, i.e. the dielectrophoresis (DEP) forces, the particle-particle electrostatic forces, particle-particle interfacial repulsive forces, particle-wall repulsive forces and the hydrodynamic forces in Stokes flow. Since the system of equations is stiff, an implicit scheme is used. To obtain the particle trajectories, a constant time-step is applied. We present some numerical tests computing hydrodynamic force, electrostatic force and DEP force using our model, including simulated trapping of particles in a micro channel by dielectrophoresis. The results are in agreement with the theories and the experimental observations.

Keyword
Computer simulation; Electrostatics; Equations of motion; Finite element method; Mathematical models; Particles (particulate matter); Dielectrophoresis (DEP) forces; Electrostatic forces; Interfacial repulsive forces; Stokes flows
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-5518 (URN)000249885500001 ()2-s2.0-33847006942 (Scopus ID)978-0-7918-4760-2 (ISBN)
Conference
4th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM2006; Limerick; Ireland
Note

QC 20100820

Available from: 2006-03-22 Created: 2006-03-22 Last updated: 2014-11-18Bibliographically approved
3. Superpositioned dielectrophoresis for enhanced trapping efficiency
Open this publication in new window or tab >>Superpositioned dielectrophoresis for enhanced trapping efficiency
2005 (English)In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 26, no 22, 4252-4259 p.Article in journal (Refereed) Published
Abstract [en]

One of the major applications for dielectrophoresis is selective trapping and fractionation of particles. If the surrounding medium is of low conductivity, the trapping force is high, but if the conductivity increases, the attraction decreases and may even become negative. However, high-conductivity media are essential when working with biological material such as living cells. In this paper, some basic calculations have been performed, and a model has been developed which employs both positive and negative dielectrophoresis in a channel with interdigitated electrodes. The finite element method was utilized to predict the trajectories of Escherichia coli bacteria in the superpositioned electrical fields. It is shown that a drastic improvement of trapping efficiency can be obtained in this way, when a high conductivity medium is employed.

Keyword
alternating current electrokinetics; dielectrophoresis; Escherichia coli; field superposition; trajectory analysis
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-5516 (URN)10.1002/elps.200500068 (DOI)000233740900003 ()2-s2.0-28244475356 (Scopus ID)
Note
QC 20100820Available from: 2006-03-22 Created: 2006-03-22 Last updated: 2017-11-21Bibliographically approved
4. Multi-step dielectrophoresis for separation of particles
Open this publication in new window or tab >>Multi-step dielectrophoresis for separation of particles
2006 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1131, no 1-2, 261-266 p.Article in journal (Refereed) Published
Abstract [en]

A new concept for separation of particles based on repetitive dielectrophoretic trapping and release in a flow system is proposed. Calculations using the finite element method have been performed to envision the particle behavior and the separation effectiveness of the proposed method. As a model system, polystyrene beads in deionized water and a micro-flow channel with arrays of interdigited electrodes have been used. Results show that the resolution increases as a direct function of the number of trap-and-release steps, and that a difference in size will have a larger influence on the separation than a difference in other dielectrophoretic properties. About 200 trap-and-release steps would be required to separate particles with a size difference of 0.2%. The enhanced separation power of dielectrophoresis with multiple steps could be of great importance, not only for fractionation of particles with small differences in size, but also for measuring changes in surface conductivity, or for separations based on combinations of difference in size and dielectric properties.

Keyword
dielectrophoresis; dielectrophoretic mobility; resolution; selectivity; particle separation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-8578 (URN)10.1016/j.chroma.2006.07.022 (DOI)000241429000027 ()2-s2.0-33749267590 (Scopus ID)
Note
QC 20100820Available from: 2008-06-02 Created: 2008-06-02 Last updated: 2010-11-08Bibliographically approved

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