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Sub–100 nm Nanoparticle Upconcentration in Flow by Dielectrophoretic Forces
 
 
Article

Dielectrophoresis from the System’s Point of View: A Tale of Inhomogeneous Object Polarization, Mirror Charges, High Repelling and Snap-to-Surface Forces and Complex Trajectories Featuring Bifurcation Points and Watersheds

by 1,* and 2
1
Department of Biophysics, University of Rostock, Gertrudenstr. 11A, 18057 Rostock, Germany
2
Independent Researcher, HaPrachim 19, Ra’anana 4339963, Israel
*
Author to whom correspondence should be addressed.
Academic Editor: Rodrigo Martinez-Duarte
Micromachines 2022, 13(7), 1002; https://doi.org/10.3390/mi13071002
Received: 31 May 2022 / Revised: 21 June 2022 / Accepted: 24 June 2022 / Published: 26 June 2022
(This article belongs to the Special Issue Micromachines for Dielectrophoresis, Volume II)
Microscopic objects change the apparent permittivity and conductivity of aqueous systems and thus their overall polarizability. In inhomogeneous fields, dielectrophoresis (DEP) increases the overall polarizability of the system by moving more highly polarizable objects or media to locations with a higher field. The DEP force is usually calculated from the object’s point of view using the interaction of the object’s induced dipole or multipole moments with the inducing field. Recently, we were able to derive the DEP force from the work required to charge suspension volumes with a single object moving in an inhomogeneous field. The capacitance of the volumes was described using Maxwell–Wagner’s mixing equation. Here, we generalize this system’s-point-of-view approach describing the overall polarizability of the whole DEP system as a function of the position of the object with a numerical “conductance field”. As an example, we consider high- and low conductive 200 µm 2D spheres in a square 1 × 1 mm chamber with plain-versus-pointed electrode configuration. For given starting points, the trajectories of the sphere and the corresponding DEP forces were calculated from the conductance gradients. The model describes watersheds; saddle points; attractive and repulsive forces in front of the pointed electrode, increased by factors >600 compared to forces in the chamber volume where the classical dipole approach remains applicable; and DEP motions with and against the field gradient under “positive DEP” conditions. We believe that our approach can explain experimental findings such as the accumulation of viruses and proteins, where the dipole approach cannot account for sufficiently high holding forces to defeat Brownian motion. View Full-Text
Keywords: system’s perspective; MatLab® model; microfluidics; DEP trajectory; LMEP; protein dielectrophoresis; virus trapping; LOC; μTAS; force spectroscopy system’s perspective; MatLab® model; microfluidics; DEP trajectory; LMEP; protein dielectrophoresis; virus trapping; LOC; μTAS; force spectroscopy
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MDPI and ACS Style

Gimsa, J.; Radai, M.M. Dielectrophoresis from the System’s Point of View: A Tale of Inhomogeneous Object Polarization, Mirror Charges, High Repelling and Snap-to-Surface Forces and Complex Trajectories Featuring Bifurcation Points and Watersheds. Micromachines 2022, 13, 1002. https://doi.org/10.3390/mi13071002

AMA Style

Gimsa J, Radai MM. Dielectrophoresis from the System’s Point of View: A Tale of Inhomogeneous Object Polarization, Mirror Charges, High Repelling and Snap-to-Surface Forces and Complex Trajectories Featuring Bifurcation Points and Watersheds. Micromachines. 2022; 13(7):1002. https://doi.org/10.3390/mi13071002

Chicago/Turabian Style

Gimsa, Jan, and Michal M. Radai. 2022. "Dielectrophoresis from the System’s Point of View: A Tale of Inhomogeneous Object Polarization, Mirror Charges, High Repelling and Snap-to-Surface Forces and Complex Trajectories Featuring Bifurcation Points and Watersheds" Micromachines 13, no. 7: 1002. https://doi.org/10.3390/mi13071002

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