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  1. Atomic force microscope
  2. Atomic nanoscope
  3. Atom probe
  4. Ballistic conduction
  5. Bingel reaction
  6. Biomimetic
  7. Bio-nano generator
  8. Bionanotechnology
  9. Break junction
  10. Brownian motor
  11. Bulk micromachining
  12. Cantilever
  13. Carbon nanotube
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  16. Chemical Compound Microarray
  17. Cluster
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  20. Computronium
  21. Coulomb blockade
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  23. Dielectrophoresis
  24. Dip Pen Nanolithography
  25. DNA machine
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  27. Electrochemical scanning tunneling microscope
  28. Electron beam lithography
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  30. Engines of Creation
  31. Exponential assembly
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  35. Fluorescence interference contrast microscopy
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  39. Grey goo
  40. Hacking Matter
  41. History of nanotechnology
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  45. Kelvin probe force microscope
  46. Lab-on-a-chip
  47. Langmuir-Blodgett film
  48. LifeChips
  49. List of nanoengineering topics
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  51. List of nanotechnology topics
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  55. Mechanochemistry
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  66. Molecular manufacturing
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  131. Richard Feynman
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  133. Scanning gate microscopy
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  135. Scanning probe microscopy
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  138. Self-assembled monolayer
  139. Self-assembly
  140. Self reconfigurable
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  142. Self-replication
  143. Smart dust
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  146. Spent nuclear fuel
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  148. Stone Wales defect
  149. Supramolecular assembly
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  152. Surface micromachining
  153. Surface plasmon resonance
  154. Synthetic molecular motors
  155. Synthetic setae
  156. Tapping AFM
  157. There's Plenty of Room at the Bottom
  158. Transfersome
  159. Utility fog


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From Wikipedia, the free encyclopedia


Dielectrophoresis (or DEP) is a phenomenon in which a force is exerted on a dielectric particle when it is subjected to a non-uniform electric field. This force does not require the particle to be charged. All particles exhibit dielectrophoretic activity in the presence of electric fields. However, the strength of the force depends strongly on the medium and particles' electrical properties, on the particles' shape and size, as well as on the frequency of the electric field. Consequently, fields of a particular frequency can manipulate particles with great selectivity. This has allowed, for example, the separation of cells or the orientation and manipulation of nanoparticles.

For a field-aligned prolate ellipsoid (a>b=c)of radius a and half-length b with dielectric constant εp in a medium with constant εm, the dielectrophoretic force is given by:

F_{dep} = \frac{\pi a^2 b}{3}\epsilon_m \textrm{Re}\left\{\frac{\epsilon^*_p - \epsilon^*_m}{\epsilon^*_m}\right\}\nabla \left|\vec{E}\right|^2

This is valid if the electric field does not change significantly over the particle length. The equation only takes into account the dipole formed and not higher order polarisation. Dielectrophoresis had been investigated a few decades ago (Pohl, 1978) but has recently been revived due to its potential in the manipulation of microparticles, nanoparticles and cells.

Pohl H.A.1 wrote in his book defining dielectrophoresis as the translational motion of neutral matter caused by polarization effects in a nonuniform electric field. The phenomenological bases are catalogued below:
1.The dielectrophoresis force can be seen only when particles are in the nonuniform electric fields.
2.Since the dielectrophoresis force does not depend on the polarity of the electric field, thus the phenomenon can be observed either with AC or DC excitation.
3.Particles are attracted to regions of stronger electric field when their permittivity exceeds that of the suspension medium.
4.When permittivity of medium is greater than that of particles, this results in motion of particles to lesser electric field.
5.DEP is most readily observed for particles with diameters ranging from approximately 1 to 1000 μm.

Phenomena associated with dielectrophoresis are electrorotation and traveling wave dielectrophoresis (TWDEP).

Dielectrophoresis coupled with Field-Flow Fractionation (DEP-FFF)
The utilization of the difference between dielectrophoretic forces exerted on different particles in nonuniform electric fields is now well known as DEP separation. The exploitation of DEP forces has been classified into two groups: namely DEP migration and DEP retention. DEP migration uses opposing polarities of DEP forces exerted on different particle types, so that one type is attracted toward high-field regions by positive dielectrophoresis while the other types are repelled by negative dielectrophoresis2. DEP retention uses competition between DEP and fluid-flow forces. Particles experiencing a weaker negative DEP forces are eluted by fluid flow, whereas particles experiencing strong positive DEP forces are trapped at electrode edges against the drag of the fluid flow3.
Field-Flow Fractionation, a family of chromatographic-like separation methods, is an elution technique capable of simultaneous separation and measurement, which was primarily introduced by Davis and Giddings4 and Giddings5. Thereafter, DEP forces were combined with field-flow-fractionation (FFF) for particle separation6,7,3. The idea of using DEP-FFF is summarized in the next paragraph.
Particles are injected into a carrier flow that passes through the separation chamber, with an external separating force (a DEP force) being applied perpendicular to the flow. By means of different factors, such as diffusion and steric, hydrodynamic, dielectric and other effects, or a combination thereof, particles (<1 μm in diameter) with different dielectric or diffusive properties attain different positions away from the chamber wall, which, in turn, exhibit different characteristic concentration profile. Particles that move further away from the wall reach higher positions in the parabolic velocity profile of the liquid flowing through the chamber and will be eluted from the chamber at a faster rate.


1. Pohl, H.A., 1978. Dielectrophoresis the behavior of neutral matter in nonuniform electric fields. Cambridge University Press. Cambridge.
2. Gascoyne, P.R.C., Y. Huang, R. Pethig, J. Vykoukal and F.F. Becker, 1992. “Dielectrophoretic separation of mammalian cells studied by computerized image analysis”. Meas. Sci.Technol. 3, 439-445.
3. Huang, Y., J. Yang, X.B. Wang, F.F. Becker and P.R.C. Gascoyne, 1999. “The removal of human breast cancer cells from hematopoietic CD34+ stem cells by dielectrophoretic field-flow-fractionation”. Journal of Hematotherapy & Stem Cell research. 8, 481-490.
4. Davis, J.M. and J.C. Giddings, 1986. “Feasibility study of dielectrical field-flow fractionation”. Sepa. Sci. and Tech. 21, 969-989.
5. Giddings, J.C., 1993. “Field-Flow Fractionation: Analysis of macromolecular, colloidal, and particulate materials”. Science. 260, 1456-1465.
6. Huang, Y., X.B. Wang, F.F. Becker and P.R.C. Gascoyne, 1997. “Introducing dielectrophoresis as a new force field for field-flow fractionation”. Biophys. J. 73, 1118-1129
7. Wang, X.B., J. Vykoukal, F.F. Becker and P.R.C. Gascoyne, 1998. “Separation of polystyrene microbeads using dielectrophoretic/gravitational field-flow-fractionation”. Biophysical Journal. 74, 2689-2701.




External links

  • The American Electrophoresis Society: Dielectrophoresis
  • Dielectrophoresis: a spherical shell model
  • On the Relationship of Dielectrophoresis and Electrowetting
  • Biological cell separation using dielectrophoresis in a microfluidic device
  • Sandia’s dielectrophoresis device may revolutionize sample preparation
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