1. 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

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

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

4. Suspension medium Membrane Cytoplasm  c,  c  d,  d  m,  m

5. Principles of experimentation with dielectrophoretic forces E

6. E

7. E

8. E

9. E F DEP

10. Principles of experimentation with dielectrophoretic forces E F DEP

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

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

13. 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

14. Principles of experimentation with dielectrophoretic forces 1kHz7kHz50kHz350kHz2MHz14MHz

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

16. Principles of experimentation with dielectrophoretic forces Electrode 1 Electrode 2 Gap

17. 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…)

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

19. Low-frequency is <40kHz Observation of parasitic flows

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

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

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

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

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

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

26. Presentation of the theory of EHD The electric force equation: Coulomb forcesDielectric forces  >> EHD

27. Presentation of the theory of EHD The electric force equation: Coulomb forcesDielectric forces  << Electro-thermal forces

28. Presentation of the theory of EHD Electrode Substrate Water ~nm

29. Presentation of the theory of EHD

31. Enhanced DEP trapping Fluid pumping Others…

32. Presentation of the theory of EHD Thank you for your attention

33. 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