Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
New Concepts for Dielectrophoretic Separations and Dielectric Measurements of Bioparticles
KTH, School of Chemical Science and Engineering (CHE), Chemistry.
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis presents two new concepts for separation of micro particles using dielectrophoresis, demonstrated by calculated examples, as well as a new method for obtaining dielectric data on living cells. The thesis is based on four papers.

Paper I describes how the trapping efficiency of micro particles may be significantly increased when superpositioned electric fields are employed in a high conductivity medium. Avoiding low conductivity media is important when working with living cells. Calculations were performed to predict trajectories of Escherichia coli bacteria in the system with superpositioned electric fields, and a model was developed which employed two arrays of interdigitated electrodes in a micro channel.

Paper II proposes a new concept for separation of micro particles, based on repetitive dielectrophoretic trapping and release in a flow system. Calculations 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 dielectrophoretic properties. Polystyrene beads in deionized water were used as a model, and calculations were performed to predict the particle behavior and the separation efficiency. It should be possible to separate particles with a size difference of 0.2 % by performing 200 trap-and-release steps. The enhanced separation power of multi step dielectrophoresis could have significant applications, not only for fractionation of particles with small differences in size, but also for measuring changes in surface conductivity.

Paper III presents a new calculation method for predicting dielectrophoretic motion of micro particles. The method is based on a soft sphere method often used in molecular dynamics. Results from the calculations are in good agreement with theoretical predictions as well as initial experimental results, showing that the method provides good efficiency and accuracy.

Paper IV describes a new method for measurements of conductivity of living bacteria. To obtain reliable conductivity values, it is important to handle the cells as gently as possible during the measurement process. A standard conductivity meter was used in combination with cross-flow filtration. In this way, repeated centrifugation and resuspension is avoided which otherwise may cause damage to the bacteria. The conductivity of Bacillus subtilis was determined to be 7000 μS/cm by means of the cross-flow filtration method, and the values differ from earlier published values by almost an order of a magnitude.

In addition to the work presented in the papers, some experimental dielectrophoresis work in chip-based systems was performed. The behavior of Escherichia coli and polystyrene beads at different voltages and frequencies were studied. Separation of beads with different sizes was achieved on an array of interdigitated electrodes. Using electrodes with a pointed shape, alignment in different directions, pearl-chain formation, rotation, and other dielectrophoretic motion of E. coli were observed.

Place, publisher, year, edition, pages
Stockholm: Kemi , 2006. , 26 p.
National Category
Analytical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-3894ISBN: 91-7178-286-9 (print)OAI: oai:DiVA.org:kth-3894DiVA: diva2:9912
Presentation
2006-03-27, Sal K2, Teknikringen 28, Stokcholm, 10:15
Opponent
Supervisors
Note
QC 20101108Available from: 2006-03-22 Created: 2006-03-22 Last updated: 2010-11-08Bibliographically approved
List of papers
1. 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
2. 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
3. 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
4. Determination of conductivity of bacteria by using cross-flow filtration
Open this publication in new window or tab >>Determination of conductivity of bacteria by using cross-flow filtration
Show others...
2006 (English)In: Biotechnology letters, ISSN 0141-5492, E-ISSN 1573-6776, Vol. 28, no 8, 601-603 p.Article in journal (Refereed) Published
Abstract [en]

An important property of the bacterial surface is its conductivity. To obtain reliable conductivity values, it is essential to handle the cells as gently as possible during the measurement procedure. We have developed a method where a standard conductivity meter is used in combination with cross-flow filtration, thus avoiding repeated centrifugation and resuspension. With this method, the conductivity of Bacillus subtilis was determined to be 7000 mu S/cm, which is a deviation from previously published data by almost an order of a magnitude.

Keyword
Bacillus subtilis, conductivity, cross-flow filtration, isoconductance point
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:kth:diva-5519 (URN)10.1007/s10529-006-0021-8 (DOI)000236846800012 ()2-s2.0-33645876464 (Scopus ID)
Note
QC 20100908. Uppdaterad från In press till Published (20100908)Available from: 2006-03-22 Created: 2006-03-22 Last updated: 2017-11-21Bibliographically approved

Open Access in DiVA

fulltext(2033 kB)1817 downloads
File information
File name FULLTEXT01.pdfFile size 2033 kBChecksum MD5
4a07ea756d36633cf985655217fe71e8e993caf3394607218f4f824af0c3060597c4362d
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Aldaeus, Fredrik
By organisation
Chemistry
Analytical Chemistry

Search outside of DiVA

GoogleGoogle Scholar
Total: 1817 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 982 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf