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The Experiment by wanghonghx

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									Manipulation of Nanoparticles
     and Nanotubes by
      Dieletrophoresis

                ME 395
            March 16, 2004
     Ned Cameron, Christine Darve,
     Christina Freyman, and Li Sun
                  Outline
•   Techniques for Separation
•   Electrodes
•   Stern Layer
•   Applications of DEP
•   Activities
•   Results
        Separation Techniques
• Electrophoresis - migration of charged molecules
  in an electrical field
• Electroosmosis - the movement of liquid through a
  bed of particles by applying an electric field
• Dielectrophoresis (DEP) - the manipulation of
  polarizable particles by non-uniform AC fields.
  Non-invasive, non-destructive, alternating pulses,
  at controllable frequency
       Dielectrophoretic Force


• DEP Force on the particle
  – r = radius of particle
  – εm= permittivity of medium
  – Re[K(ω)]-real part of the Clausius-Mossotti
    factor
  – E - gradient of electric field
            Clausius-Mossotti Factor


        ε*m= complex permittivities of the medium
        ε*p = complex permittivities of the particle




        σ the conductivity; ε the permittivity; ω the angular frequency of the applied
        electric field; j=-1, psurface conductance of particle/radius of particle
If K(ω) > 0 , then particles move to regions of highest field strength -
                             positive DEP
If K(ω) < 0 , then particles move to regions of lowest field strength -
                             negative DEP
       Activity 1 - Plotting Re[K(ω)] vs
         ω for 500 and 200 nm beads

                                                                     A plot of the Clausius-
                                                                     Mossotti factor versus
                                                                     frequency for 216-nm-
                                                                     (dashed) and 557-nm-
                                                                     diameter (solid) latex
                                                                     particles with a particle
                                                                     permittivity p = 2.55 and a
                                                                     medium conductivity m = 1
                                                                     mSm-1. The surface
                                                                     conductance was set at 2.32
                                                                     nS for both sizes of particles.
Morgan, Hywel et al. “Separation of Submicron Bioparticles by
Dielectrophoresis.” Biophys J, July 1999, p. 516-525, Vol. 77, No.
1
      Electrode Arrays
 and Electric Field Analysis
The Scaling Law




V ~ the applied voltage and
Le ~the characteristic length of the electrodes
Electrode Fabrication & Electrode Configuration


 Deposit gold electrodes


     Si Substrate
Parallel / Tip-to-tip electrode array




N G Green and H Morgan, Dielectrophoretic investigations of sub-micrometre latex spheres,
J. Phys. D: Appl. Phys. 30 (1997) 2626–2633.
   Castellated electrode array




N G Green and H Morgan, Dielectrophoretic separation of nano-particles,
J. Phys. D: Appl. Phys. 30 (1997)
    Polynomial electrode array (1)




N G Green and H Morgan, Dielectrophoretic investigations of sub-micrometre latex spheres,
J. Phys. D: Appl. Phys. 30 (1997) 2626–2633.
    Polynomial electrode array (2)




Michael Pycraft Hughes, AC Electrokinetics: Applications for Nanotechnology
http://www.foresight.org/Conferences/MNT7/Papers/Hughes/
Stern Model & Interfacial Effects on Electrode
Double   layer or Stern layer   Electro-osmosis




  surface charges

  bound   ions (Stern layer)
  diffuse double   layer
Combination of DEP and EHD forces
Applications of DEP
                 Positive and negative DEP
                                                        100 kHz, positive DEP
    • Digitized images of 282 nm
      latex spheres in a fluorescence
      microscopes
    • Suspending buffer: 10 mM
      potassium phosphate,
                                   Chains of beads at
      conductivity =0.17 S/m
                                      the electrodes


                          Electric field map
                                                        1 MHz, negative DEP




                                 Beads trapped at the
                                              center
Electrode array for DEP
                Complications of negative DEP
          • High frequency (MHz) needed to achieve negative DEP
          • Particles are trapped in the electric cage
          • Brownian motion



                            E2 map


                                                         Dielectric potential
                                                         well where particles
                                                         are trapped in negative
                                                         DEP
      Potential barrier
   preventing particles
from entering the well                                electrode
Example of electrode
configurations for
electric cages.
                       DEP applications - 1
 •   Separation of metallic and semi-conducting nano-tubes (for nano-scale electronics
     research and applications)
       – Suspension of Carbon nano-tubes subjected to a inhomogeneous AC field
       – Metallic nanotubes (and bundles containing at least one metallic nano-tube
          dominating the dielectric properties) are attracted at the electrodes
       – The nano-tubes remaining in the suspension are semi conducting



            Suspension drop                            electrodes




                           SWNT experimental set-up

R. Krupke, F. Hennrich, H. Lohneysen, M. Kappes, Universitat Karlsruhe, D, Science, 301, pp 344 -347
(2003).
                      DEP applications - 2
   •   Trapping of human viruses (detection, research of viral properties)

         – 250 nm diameter enveloped human virus and viral capsid of Herpes simplex
           (HSV-1)
         – Gold electrodes on glass slides, 1 Hz to 20 MHz AC excitation
         – Stable levitation of a single viral capsid in the potential well


                                                             electrodes




                             virus
                             envelope
 Herpes Simplex Virion (HSV-1), virus and
 its envelope



M. Hughes and H. Morgan, University of Glasgow, UK, J. of D: appl. Phys. , 31, pp 2205-2210 (1998).
                                DEP applications - 3
•    Concentration of colloids from solution            •    Example of manipulation of nano-particles:

       – Useful, e.g., to collect single parts                 – 14 nm diameter fluorescently labeled
         for nano-machines on the                                latex spheres precipitated from an
         “assembly site” using negative                          aqueous solution (=2.5 mSm-1) by
         DEP. Examples:                                          positive (a) and negative (b) DEP.
           • two or more interlocking                          – micro spheres and colloidal gold particles
              molecules, normally in a
                                                                 fictionalized using antibodies, used to
              highly dilute solution,
              concentrated by DEP into a                         construct microscopic biosensors(1)
              confined space where they                 8 Vpp, 2 MHz                           10 Vpp, 10 MHz
              assemble;
           • collecting "fuel" for a nano-
              machine from solution. Self-
              assembly reaction takes place
              at the collection point;
           • bringing together "stacking"
              particles of different types,
              which bind on contact
           • etc.



    (1)Velev   OD, Kaler EW, In situ assembly of colloidal particles into miniaturized biosensors
                      DEP applications - 4
•    Dielectrophoretic separation and transportation of cells on micro fabricated chips

      – microchip with a suitable array of electrodes produces controlled transport and
        switching electric fields
      – The electric field pattern is switched so that human blood cells are transported from
        the top of the chip to the left side (see next slide)




                                                                      Fluid chamber comprising
                                                                      a DEP chip


    Particle switch with 4-        Transportation chip
    phase signals applied to       (bottom) and guide chip
    the electrodes                 (top) separated by 80 mm

    J. Xu, L. Wu, M. Huang, W. Yang, J. Cheng, X-B Wang, AVIVA Bioscences Corp, CA & Dept. of
    Biological Sciences and Biotechnolog, Tsinghua University, Beijing, China
                                  -4
                 DEP applicationsTransport
                                                               electrode




Application of AC voltages      White blood cells
                                                       Three-
caused carbon beads to be       retained by sinusoidal
collected along electrode edges electrodes human blood way
and polystyrene beads to be                            switch
levitated.
                              Blood cell


1                                 2                                   3



Transport along top channel        Three-way switching to             Transport along left channel
                                   left channel

J. Xu, L. Wu, M. Huang, W. Yang, J. Cheng, X-B Wang, AVIVA Bioscences Corp, CA & Dept. of
Biological Sciences and Biotechnolog, Tsinghua University, Beijing, China
                         DEP applications - 5
•    Dielectrophoretic size-sensitive particle
     filter for micro-fluidics applications

       – The dielectrophoretic force, and the
         cross-over frequency from positive
         to negative DEP, depends on the
         particle radius
       – At given frequency, particles with
         smaller radius tend to experience
         positive DEP, particle with larger
         radius experience negative DEP
       – By proper geometry arrangement of
         electrodes and operating frequency
         selection it is possible to trap                              free
         particles selectively based on their
         size




    J. Auerswald, H.F. Knapp, Micro Center Central Switzerland
                                                                 trapped
                       DEP applications - 6




     DEP of 557 nm diameter latex spheres
     (a) Negative DEP with polynomial electrode array. (b) Negative DEP
     with castellated electrode array. (c) Positive DEP with polynomial
     electrode array. (d) Positive DEP with castellated electrode array.



N.G. Green, A. Ramos, H. Morgan, J. Phys. D: Appl. Phys., 33, pp 632-641 (2000)
                       DEP applications - 6




        (a) Schematic of fluid flow observed in polynomial arrays at high
        frequencies. (b) Schematic of fluid flow observed at low frequencies
        and low potentials. (c) Experimental image (12 Volts peak -to-peak, 6
        MHz). (d) Experimental image (5 Volts peak-to-peak, 3 MHz).


N.G. Green, A. Ramos, H. Morgan, J. Phys. D: Appl. Phys., 33, pp 632-641 (2000)
                       DEP applications - 6




       Diagrams and experimental images of AC electro-osmosis for two
       designs of electrodes. (a) Schematic diagrams for polynomial
       electrode arrays. (b) Schematic diagrams for castellated electrode
       arrays. (c) Experimental image for polynomial electrode arrays. (d)
       Experimental image for castellated electrode arrays.

N.G. Green, A. Ramos, H. Morgan, J. Phys. D: Appl. Phys., 33, pp 632-641 (2000)
                       DEP applications - 6




       Experimental images of 557 nm diameter latex spheres over three
       decades of frequency on castellated electrode arrays at an applied
       potential of 8 Volts peak-to-peak and a solution conductivity of 2 mSm-1.




N.G. Green, A. Ramos, H. Morgan, J. Phys. D: Appl. Phys., 33, pp 632-641 (2000)
The Experiment
  The Equipment:
Activity 2: Positive DEP
    • Movies
      – posfork.avi
      – posstick.avi
      – possquare.avi
Activity 3: Negative DEP
    • Movie
      – negstick.avi
Activity 4: Carbon Nanotube
        Manipulation
      • Positive
         – cntpos.avi
      • Negative
         – negcnt.avi
            Future Activity: Four Electrode
                    Manipulation
   • Buffer – 10 mM potassium
   phosphate
   • Conductivity 0.17 Sm-1
   • Latex sphere diameter: 557 nm
   • 1 Hz to 20 MHz AC                                        Side view of traveling wave device
   • Negative DEP: 5 V p-p @ 5 MHz
   • Positive DEP: 5 V p-p @ 500 kHz


                                   Y1 = A · sin(wt)
                                   Y2 = A · sin(wt +p /2)
                                   Y3 = A · sin(wt + p)
                                   Y4 = A · sin(wt +3 p /2)
Inspired from John Zelena (Mechanical Engineering) – Wilkes
University, NSF Summer Undergraduate Fellowship in Sensor
Technologies, technical report (2004).
                                                                               Top view of device design
         Acknowledgements
• Thanks to:
  – Dr. Moldova
  – Prof. Espinosa
  – Dr. Espinosa’s graduate students that had to
    keep logging us back on to the server when we
    would crash the computer

								
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