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www.surrey.ac.uk Manipulation of cells by dielectrophoresis – the effect of EHD By Lionel Broche With the help of Kai Hoettges Biomedical Engineering Group Supervisors: M.P.Hughes, S.Ogin, G.E.N.Kass

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Summary Principles of experimentation with dielectrophoretic forces Observations at low-frequency: the EHD effect Presentation of the theory of EHD

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Manipulation of cells by dielectrophoresis – the effect of EHD Principles of experimentation with dielectrophoretic forces

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Suspension medium Membrane Cytoplasm c, c d, d m, m

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Principles of experimentation with dielectrophoretic forces E

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E

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E

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E

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E F DEP

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Principles of experimentation with dielectrophoretic forces E F DEP

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Principles of experimentation with dielectrophoretic forces Suspension medium Membrane Cytoplasm c, c d, d m, m E F DEP

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Principles of experimentation with dielectrophoretic forces Suspension medium m, m E 2.r Q -Q

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Principles of experimentation with dielectrophoretic forces DEP theory for spherical particles: F DEP = 4 r 3. m 0. Re (K( DEP force Cell radius Dipole-related factor

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Principles of experimentation with dielectrophoretic forces 1kHz7kHz50kHz350kHz2MHz14MHz

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Principles of experimentation with dielectrophoretic forces The DEP spectrum: Frequency (Hz) F DEP

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Principles of experimentation with dielectrophoretic forces Electrode 1 Electrode 2 Gap

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Principles of experimentation with dielectrophoretic forces The experiments give a measure of the DEP force for different frequencies of the signal The result can be used in several ways (detection, measure…)

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Manipulation of cells by dielectrophoresis – the effect of EHD Observations at low-frequency: the EHD effect

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Low-frequency is <40kHz Observation of parasitic flows

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Observations at low- frequency: the EHD effect Electrode 1 Electrode 2 Gap

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Observations at low- frequency: the EHD effect Electrode 1 Electrode 2 Gap

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Observations at low- frequency: the EHD effect Electro-HydroDynamics: EHD Caused by the electronic double-layer

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Manipulation of cells by dielectrophoresis – the effect of EHD Presentation of the theory of EHD

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Navier-Stokes equation: Negligible since Re<<1 Pressure Visquous forces Electric forces Gravitation

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Presentation of the theory of EHD The electric force equation: Coulomb forcesDielectric forces

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Presentation of the theory of EHD The electric force equation: Coulomb forcesDielectric forces >> EHD

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Presentation of the theory of EHD The electric force equation: Coulomb forcesDielectric forces << Electro-thermal forces

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Presentation of the theory of EHD Electrode Substrate Water ~nm

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Presentation of the theory of EHD

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Enhanced DEP trapping Fluid pumping Others…

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Presentation of the theory of EHD Thank you for your attention

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References Castellanos, Ramos et al. (2003), “Electrohydrodynamics and dielectrophoresis in microsystems: Scaling laws”, Journal of Physics D: Applied Physics, 36(20): 2584 Hoettges, McDonnell et al. (2003), “Use of combined dielectrophoresis / electrohydrodynamics forces for biosensor enhancement”, Journal of Physics D: Applied Physics, 36(20): 101-104

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