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  • 1.
    Aldaeus, Fredrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Lin, Yuan
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Roeraade, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Multi-step dielectrophoresis for separation of particles2006In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1131, no 1-2, p. 261-266Article in journal (Refereed)
    Abstract [en]

    A new concept for separation of particles based on repetitive dielectrophoretic trapping and release in a flow system is proposed. Calculations using the finite element method have been performed to envision the particle behavior and the separation effectiveness of the proposed method. As a model system, polystyrene beads in deionized water and a micro-flow channel with arrays of interdigited electrodes have been used. Results show that the resolution increases as a direct function of the number of trap-and-release steps, and that a difference in size will have a larger influence on the separation than a difference in other dielectrophoretic properties. About 200 trap-and-release steps would be required to separate particles with a size difference of 0.2%. The enhanced separation power of dielectrophoresis with multiple steps could be of great importance, not only for fractionation of particles with small differences in size, but also for measuring changes in surface conductivity, or for separations based on combinations of difference in size and dielectric properties.

  • 2.
    Aldaeus, Fredrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Lin, Yuan
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Roeraade, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Superpositioned dielectrophoresis for enhanced trapping efficiency2005In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 26, no 22, p. 4252-4259Article in journal (Refereed)
    Abstract [en]

    One of the major applications for dielectrophoresis is selective trapping and fractionation of particles. If the surrounding medium is of low conductivity, the trapping force is high, but if the conductivity increases, the attraction decreases and may even become negative. However, high-conductivity media are essential when working with biological material such as living cells. In this paper, some basic calculations have been performed, and a model has been developed which employs both positive and negative dielectrophoresis in a channel with interdigitated electrodes. The finite element method was utilized to predict the trajectories of Escherichia coli bacteria in the superpositioned electrical fields. It is shown that a drastic improvement of trapping efficiency can be obtained in this way, when a high conductivity medium is employed.

  • 3.
    Lin, Yuan
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Modeling of dielectrophoresis in micro and nano systems2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis presents models and simulations of dielectrophoretic separation of micro and nano particles. The fluid dynamics involved and the dielectric properties of water inside single-walled carbon nanotube are studied as well.

    Based on the effective dipole moment method, the particle dynamic model focuses on the translational motions of micro particles. The hydrodynamic force between the particles and the particle-particle electrostatic interactions are considered as well. By comparing the dimensionless parameters, the dominating force can be determined. Based on a simplified version of the particle dynamic model, two numerical simulations are carried out to predict the efficiency of dielectrophoretic separation of micro size particles. The first calculation suggests a strategy to improve the trapping efficiency of E.coli bacteria by applying superimposed AC electric fields. The second calculation discusses the concept of mobility and improves the separation rate of particles by a multi-step trapping-releasing dielectrophoresis strategy.

    The model is extended down scale to calculate the separation of metallic and semiconducting single-walled carbon nanotubes by the modified effective dipole moment method for prolate ellipsoids. The steeply changed gradient of electric field results in the local joule heating therefore creates gradient of dielectric properties in the solution. As a result, certain pattern of fluid flow with a considerable strength is created and affects the motion of carbon nanotubes especially close to the electrode gap, which indicates that the so-called electrothermal flow should be considered in designing the experiment to separate single-walled carbon canotubes.

    When the length scale of particles is comparable to that of the electrodes, the calculation of dielectrophoretic force by the effective dipole moment is considered not to be accurate since only the electric field in the center point is taken into account. Hence in the thesis a new method based on distributed induced charge is suggested. By approximating a straight slender body as a prolate ellipsoid, the electric field of multiple points along the centerline are all considered in the calculation and the interaction between particles could be concurrently taken care. This method is expected to be an improved method to calculate the dielectrophoretic force of rod-like virus, DNA, nanowires and carbon nanotubes.

    The dielectric property of water confined in carbon nanotubes is expected to be dramatically different from that of bulk water. The thesis also contains a molecular dynamics study to reveal the difference also a dependence on the diameter of carbon nanotubes. The results show that along the axial direction, both the static permittivity and the relaxation time are larger than the isotropic bulk water, and in the cross-section plane it is opposite. When the radius of the carbon nanotubes increases, the properties of water inside become closer to the bulk water.

  • 4.
    Lin, Yuan
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Numerical modeling of dielectrophoresis2006Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    We investigate the dielectrophoretic separation of microparticles. Two different models are formulated in two characteristic time scales. The first model mainly accounts for the orientation behavior and rotational motion of non-spheric microparticles. The concept of effective charge is suggested to calculate the finite size non-spheric particles. It is combined with the fluid particle dynamics method to calculate hydrodynamic as well as dielectrophoretic forces and torques. The translational motion and the particle-particle interaction are calculated also, but they take much longer time to be observed due to the different time scales of the rotational and translational motions By viewing the particle as spheres, the second model focus on the translational motion of spheres. The hydrodynamic force between particles and particle-particle electrostatic interactions are also taken into account. We check the relative magnitude ratio between these forces in order to determine the importance of these forces. To predict and guide the design of experimental dielectrophoretic separation, two numerical applications are carried out. The first calculation suggests optimum patterns to improve the trapping efficiency of E.coli. cells by applying superimposed AC electric fields. The second calculation finds out the mobility and separation rate of particles which differs in size and electric properties by a multi-step trapping-releasing strategy.

  • 5.
    Lin, Yuan
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Simulation of dielectrophoresis of finite size particlesArticle in journal (Refereed)
  • 6.
    Lin, Yuan
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Aldaeus, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry (closed 20110630).
    Roeraade, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry (closed 20110630).
    Simulation of dielectrophoretic motion of microparticles using a molecular dynamics approach2006In: 4th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM2006, 2006, p. 1-10Conference paper (Refereed)
    Abstract [en]

    We model and simulate dielectrophoresis of microscale particles using the finite element method. A soft sphere system molecular dynamics model is presented, which solves a set of equations for the motion of every particle. The model couples most of the significant forces, i.e. the dielectrophoresis (DEP) forces, the particle-particle electrostatic forces, particle-particle interfacial repulsive forces, particle-wall repulsive forces and the hydrodynamic forces in Stokes flow. Since the system of equations is stiff, an implicit scheme is used. To obtain the particle trajectories, a constant time-step is applied. We present some numerical tests computing hydrodynamic force, electrostatic force and DEP force using our model, including simulated trapping of particles in a micro channel by dielectrophoresis. The results are in agreement with the theories and the experimental observations.

  • 7.
    Lin, Yuan
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Shiomi, Junichiro
    Department of Mechanical Engineering, The University of Tokyo.
    Maruyama, Shigeo
    Department of Mechanical Engineering, The University of Tokyo.
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Dielectric properties of water inside single-walled carbon nanotubesArticle in journal (Other academic)
  • 8.
    Lin, Yuan
    et al.
    Department of Process Technology, SINTEF Materials and Chemistry.
    Shiomi, Junichiro
    Department of Mechanical Engineering, University of Tokyo.
    Maruyama, Shigeo
    Department of Mechanical Engineering, University of Tokyo.
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Dielectric relaxation of water inside a single-walled carbon nanotube2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, no 4Article in journal (Refereed)
    Abstract [en]

    We report a molecular dynamics study of anisotropic dynamics and dielectric properties of water confined inside a single-walled carbon nanotube (SWNT) at room temperature. The model includes dynamics of an SWNT described by a realistic potential function. A comparison with simulations assuming a rigid nanotube demonstrates that the popular assumption severely overestimates the dielectric constant for small diameter SWNTs. Simulations of water inside flexible SWNTs with various diameters reveal strong directional dependence of the dynamic and dielectric properties due to the confinement effect. The obtained dielectric permittivity spectra (DPS) identify two different dipolar relaxation frequencies corresponding to the axial and the cross-sectional directions, which are significantly smaller and larger than the single relaxation frequency of bulk water, respectively. The frequency variation increases as the SWNT diameter decreases. The results suggest that DPS can be used as a fingerprint of water inside SWNTs to monitor the water intrusion into SWNTs.

  • 9.
    Lin, Yuan
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics.
    Shiomi, Junichiro
    Department of Mechanical Engineering, University of Tokyo.
    Maruyama, Shigeo
    Department of Mechanical Engineering, University of Tokyo.
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics.
    Electrothermal flow in dielectrophoresis of single-walled carbon nanotubes2007In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 76, no 4, p. 045419-1-045419-5Article in journal (Refereed)
    Abstract [en]

    We theoretically investigate the impact of the electrothermal flow on the dielectrophoretic separation of single-walled carbon nanotubes (SWNTs). The electrothermal flow is observed to control the motions of semiconducting SWNTs in a sizable domain near the electrodes under typical experimental conditions, therefore helping the dielectrophoretic force to attract semiconducting SWNTs in a broader range. Moreover, with the increase of the surfactant concentration, the electrothermal flow effect is enhanced, and with the change of frequency, the pattern of the electrothermal flow changes. It is shown that under some typical experimental conditions of dielectrophoretic separation of SWNTs, the electrothermal flow is a dominating factor in determining the motion of SWNTs.

  • 10.
    Lin, Yuan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Shiomi, Junichiro
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Maruyama, Shigeo
    Department of Mechanical Engineering, The University of Tokyo.
    Amberg, Gustav
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Brandner, Birgit D.
    YKI, Ytkemiska Institute AB/Institute for Surface Chemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Dielectric properties of water inside single-walled carbon nanotubesIn: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838Article in journal (Other academic)
  • 11. Shiomi, Junichiro
    et al.
    Lin, Yuan
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Carlborg, Carl Fredrik
    KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Maruyama, Shigeo
    Low dimensional heat and mass transport in carbon nanotubes2010In: Proceedings of the ASME Micro/Nanoscale Heat and Mass Transfer International Conference 2009, MNHMT2009, 2010, p. 337-346Conference paper (Refereed)
    Abstract [en]

    This report covers various issues related to heat and mass transport in carbon nanotubes. Heat and mass transport under quasi-one-dimensional confinement has been investigated using molecular dynamics simulations. It is shown that the quasi-ballistic heat conduction manifests in the length and diameter dependences of carbon nanotube thermal conductance. Such quasi-ballistic nature of carbon nanotube heat conduction also influences the thermal boundary conductance between carbon nanotubes and the surrounding materials. The quasi-one-dimensional structure also influences the mass transport of water through carbon nanotubes. The confinement gives rise to strongly directional dynamic properties of water. Here, it is demonstrated that the confined water can be efficiently transported by using the temperature gradient. Furthermore, the simulations reveal the diameter-dependent anisotropic dielectric properties, which could be used to identify intrusion of water into carbon nanotubes.

1 - 11 of 11
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