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Nanobiotechnology, IEE Proceedings -

Issue 2 • Date 1 Nov. 2003

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Displaying Results 1 - 9 of 9
  • Aggregation profile characterisation in dielectrophoretic structures using bacteria and submicron latex particles

    Page(s): 70 - 74
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (335 KB)  

    A novel quantitative characterisation method for the measurement of anomalous low frequency aggregation processes on dielectrophoresis electrodes has been developed. Experimental evidence is provided for the relationship between the aggregation effect and AC electro-osmotical fluid motion theory. The aggregation profile dependence for E.coli bacteria, as a function of frequency and applied field, has been quantitatively examined. Additional experimental observations of the aggregation profiles of latex particles with dimensions of hundreds of nanometres, also confirm the relationship between this aggregation effect and the mentioned fluid motion theory. View full abstract»

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  • Dielectrophoresis of microbioparticles in water with planar and capillary quadrupole electrodes

    Page(s): 59 - 65
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (879 KB)  

    Dielectrophoresis of single microbioparticles was measured in a planar quadrupole microelectrode (50 μm or 65 μm in working area radius) with a microscope. Carbon and polystyrene microparticles, yeast cells and DNA molecules (about 40 kbp) were adopted as a sample. Their dielectrophoretic mobilities were analysed quantitatively with their intrinsic and surface conductivity, their permittivities and their sizes as well as the conductivity and permittivity of aqueous media. Using the dielectrophoretic mobilities obtained with the planar quadrupole microelectrode, some instances of the separation performance between the microparticles were demonstrated with a fabricated capillary quadrupole microelectrode (82.5 μm in bore radius) under the field flow fractionation regime. View full abstract»

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  • Influence of scale on electrostatic forces and torques in AC particulate electrokinetics

    Page(s): 39 - 46
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    Dielectrophoretic forces and torques move and manipulate biological cells, typically of the order of 10 μm (∼10-5 m) in diameter and ordinarily suspended in aqueous liquids, using electrodes with dimensions around 100 μm (∼10-4 m). The ability to exploit these same electromechanical effects for particles below 1 μm, that is, <10-6 m, creates opportunities for remote manipulation and handling of subcellular components, biological macromolecules, and DNA. In this paper, Trimmer's bracket notation (1989) is adapted for systematic examination of the scaling laws governing electrokinetic behaviour. The purpose is to shed light on how critical performance measures relevant to the laboratory on a chip are affected by reducing particle sizes and electrode dimensions into the nanometre range. The scaling methodology facilitates consideration of the effect of electrode structure and particle size reduction on voltage, electric field, heating, and response time. Particles with induced moments, dipolar and quadrupolar, as well as permanent dipoles are examined. Separate consideration is given to electrical torque and its application in electrorotation and particle alignment. An eventual goal of these scaling studies is to identify the lower limit on the size of particles that can be manipulated effectively using electrokinetic phenomena. View full abstract»

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  • Dielectrophoretic manipulation of surface-bound DNA

    Page(s): 54 - 58
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (351 KB)  

    Dielectrophoretic manipulation enables the positioning and orientation of DNA molecules for nanometer-scale applications. However, the dependence of the dielectrophoretic force and torque on the electric field magnitude and frequency has to be well characterised to realise fully the potential of this technique. DNA in solution is attracted to the strongest electric field gradient (i.e. the electrode edge) as a result of the dielectrophoretic force, while the dielectrophoretic torque aligns the DNA with its longest axis parallel to the electric field. In this work, the authors attached λ-DNA fragments (48 and 25 kilobases) to an array of gold microelectrodes via a terminal thiol bond and characterised the orientation and elongation as a function of electric field magnitude (0.1-0.8 MV/m) and frequency (0.08-1.1 MHz). Maximum elongation was observed between 200 and 500 kHz for the attached DNA. Dielectrophoresis is limited by thermal randomisation at electric fields below 0.1 MV/m and by electrothermal effects above 0.7 MV/m. The authors conclude that dielectrophoresis can be used to manipulate surface-immobilised DNA reproducibly. View full abstract»

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  • Microdevices for separation, accumulation, and analysis of biological micro- and nanoparticles

    Page(s): 82 - 89
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    Microfabrication and performance of a novel microsystem for separation, accumulation and analysis of biological micro- and nanoparticles is reported. Versatile chip functions based on dielectrophoresis and microfluidics were integrated to isolate particles from complex sample solutions such as serum. A bead-based assay for virus detection is proposed. Separation of micro- and sub-μm beads employing dielectrophoretic deflector and bandpass structures is demonstrated. Individual antibody coated beads with hepatitis A virus bound to their surface were trapped by negative dielectrophoresis in a field cage and analysed by fluorescence microscopy. View full abstract»

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  • Editorial

    Page(s): 37 - 38
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (186 KB)  

    First Page of the Article
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  • 3D focusing of nanoparticles in microfluidic channels

    Page(s): 76 - 81
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    Dynamic focusing of particles can be used to centre particles in a fluid stream, ensuring the passage of the particles through a specified detection volume. This paper describes a method for focusing nanoparticles using dielectrophoresis. The method differs from other focusing methods in that it manipulates the particles and not the fluid. Experimental focusing is demonstrated for a range of different particle types, and discussed in terms of the operational limits of the device. Dynamic numerical simulations of the particle motion in the device are presented and compared with the experimental results. The potential of the device for nanoparticle control and manipulation in microfluidic chips is discussed. View full abstract»

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  • Dielectrophoretic manipulation of DNA

    Page(s): 47 - 53
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (385 KB)  

    The characterisation and spatial manipulation of cells by AC electrokinetic methods such as dielectrophoresis and electrorotation is well established. However, applications to submicroscopical objects like viruses and molecules have been rare. Only recently has the number of such studies risen more quickly due to the availability of suitable electrodes and a growing need for single molecule techniques. Of special interest is the spatial control of single DNA molecules for genetic investigations as well as for the building of well defined structures with nanometre resolution. Here a review is given of dielectrophoretic studies dealing with single and double stranded DNA emphasising single molecule aspects. View full abstract»

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  • Separation of latex spheres using dielectrophoresis and fluid flow

    Page(s): 66 - 69
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (410 KB)  

    The authors present a method for separation of two latex spheres populations using dielectrophoresis (DEP) and the fluid drag force. Microelectrodes of a suitable layout are used to trap one population of spheres, while the other one is dragged away from the electrodes by the generated fluid flow. The finite difference method is implemented in C++ to calculate the potential distribution by solving Laplace's equation. From the potential distribution, the DEP force on particles is calculated. The drag force on particles due to the liquid motion is calculated from the observed fluid velocity. The experimental results are shown to be in good agreement with the numerical solution. View full abstract»

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