Manipulation of Bio-Particles in Microelectrode Structures by Means of Non-Uniform AC Electric Fields

2002 ◽  
Author(s):  
Antonio Castellanos ◽  
Antonio Ramos ◽  
Antonio Gonza´lez ◽  
Hywel Morgan ◽  
Nicolas Green
Keyword(s):  
Electric Fields ◽  
Mass Density ◽  
Fluid Motion ◽  
Electrode System ◽  
Viscous Drag ◽  
Diffuse Double Layer ◽  
Ac Electroosmosis ◽  
Ac Electric Fields ◽  
High Electric Fields ◽  
And Diffusion

Non-uniform ac electric fields induce movement of polarizable particles. This phenomenon, known as dielectrophoresis, is useful to manipulate bioparticles. High electric fields when used in bio-separation systems give rise to fluid motion, which in turn results in a viscous drag on the particle. These fields generate heat, leading to volume forces in the liquid. Gradients in conductivity and permittivity rise to electrothermal forces; gradients in mass density to buoyancy. Also non-uniform ac electric fields produce forces on the induced charges in the diffuse double layer on the electrodes, and the resulting steady fluid motion has been termed ac electroosmosis. The effects of Brownian motion and diffusion are also discussed in this context. The orders of magnitude of the various forces experienced by a submicrometre particle in a model electrode system are calculated. The results are compared with experiments and the relative influence of each type of force is described.

AC Electrokinetics for Biosensors

2004 ◽  
Author(s):  
M. Sigurdson ◽  
C. Meinhart ◽  
D. Wang
Keyword(s):  
Electric Fields ◽  
Dna Hybridization ◽  
Fluid Motion ◽  
Diffusive Transport ◽  
Analyte Concentration ◽  
Ac Electrokinetics ◽  
Ac Electric Fields ◽  
Binding Rate ◽  
Electrothermal Flow ◽  
Biosensor Device

We develop here tools for speeding up binding in a biosensor device through augmenting diffusive transport, applicable to immunoassays as well as DNA hybridization, and to a variety of formats, from microfluidic to microarray. AC electric fields generate the fluid motion through the well documented but unexploited phenomenon, Electrothermal Flow, where the circulating flow redirects or stirs the fluid, providing more binding opportunities between suspended and wall-immobilized molecules. Numerical simulations predict a factor of up to 8 increase in binding rate for an immunoassay under reasonable conditions. Preliminary experiments show qualitatively higher binding after 15 minutes. In certain applications, dielectrophoretic capture of passing molecules, when combined with electrothermal flow, can increase local analyte concentration and further enhance binding.

Two-Color Micro PIV Measurements of Particle and Fluid Motion in AC Electrokinetics

Materials ◽  
2003 ◽  
Author(s):  
Dazhi Wang ◽  
Carl Meinhart ◽  
Marin Sigurdson
Keyword(s):  
Electric Fields ◽  
Fluorescent Dyes ◽  
Fluid Velocity ◽  
A Priori ◽  
Fluid Motion ◽  
Ac Electroosmosis ◽  
Ac Electrokinetics ◽  
Piv Measurements ◽  
Drag Forces ◽  
Micro Piv

Two-Color μ-PIV is developed and used to uniquely determine the fluid velocity based on the micron-resolution Particle Image Velocimetry (μ-PIV) technique [1–3]. The fluid velocity field was obtained by measuring the motion of two different sizes particles, 0.7 and 1.0 μm. The different sizes of particles contain different fluorescent dyes, allowing them to be distinguished using fluorescent filter cubes. By comparing the velocity fields from the two different size particles, the underlying fluid motion can be uniquely determined, without a priori knowledge of the electrical properties of the particles, or the electrical field. The test section is formed by two wedge-shaped electrodes sandwiched between two glass wafers. In the presence of nonuniform ac electric fields, the particles experience dielectrophoretic (DEP) forces due to polarization and drag forces due to viscous interaction with the suspending medium, and the fluid motion is induced by the electrothermal effect and/or ac electroosmosis. The micro-PIV measurements are used to determine quantitatively the physical characteristics of the AC electrokinetic effects.

scholarly journals Anomalous Anisotropic Diffusion of Electron Swarms in AC Electric Fields

1995 ◽  
Vol 48 (6) ◽  
pp. 925 ◽  
Author(s):  
RD White ◽  
RE Robson ◽  
KF Ness
Keyword(s):  
Electric Fields ◽  
Diffusion Coefficients ◽  
Anisotropic Diffusion ◽  
Time Varying ◽  
Longitudinal Diffusion ◽  
Temporal Behaviour ◽  
Ac Electric Fields ◽  
Wide Range ◽  
First Time ◽  
And Diffusion

A time-dependent multi-term solution of the Boltzmann equation is used to calculate the drift and diffusion coefficients of electron swarms in gases under the influence of a time varying electric field. Two model gases are considered and for a.c. electric fields results are presented for a wide range of applied frequencies. Of particular interest is the anomalous temporal behaviour of the longitudinal diffusion coefficient, which is discussed here for the first time.

AC Electrokinetic Pumps for Micro/NanoFluidics

2004 ◽  
Author(s):  
Junqing Wu ◽  
Gaurav Soni ◽  
Dazhi Wang ◽  
Carl D. Meinhart
Keyword(s):  
Electric Fields ◽  
Fluid Motion ◽  
Lab On A Chip ◽  
Dna Amplification ◽  
Aqueous Fluid ◽  
Working Fluid ◽  
High Frequencies ◽  
Electrode Surfaces ◽  
Ac Electric Fields ◽  
Micro Channels

We have developed micropumps for microfluidics that use AC electric fields to drive aqueous fluid motion through micro channels. These pumps operate at relatively low voltages (~5–10Vrms), and high frequencies (~100kHz). They have several distinct advantages over the DC electrokinetic pumps. The low voltages make the pumps well suited for a wide variety of biosensor and “Lab-on-a-Chip” applications (e.g. PCR chip for DNA amplification). The high frequencies minimize electrolysis, so that bubbles do not form on the electrode surfaces, and do not contaminate the working fluid. The pumps can also be used as active valves or precision micro-dispensers.

scholarly journals Transport Analysis of RF Drift-velocity Filter Employing Crossed DC and AC Electric Fields for Ion Swarm Experiments

1995 ◽  
Vol 48 (3) ◽  
pp. 491 ◽  
Author(s):  
K Iinuma ◽  
M Takebe
Keyword(s):  
Electric Fields ◽  
Drift Velocity ◽  
Analytical Formula ◽  
Transmission Efficiency ◽  
Ion Separation ◽  
Velocity Filter ◽  
Ac Electric Fields ◽  
Operational Characteristics ◽  
Cs Ions ◽  
And Diffusion

The operational characteristics of the RF drift-velocity filter developed recently by us to separate a mixture of gaseous ions are examined theoretically. The solutions of the appropriate transport equations provide an analytical formula for the transmission efficiency of the filter in terms of the mobility and diffusion coefficient of the ions, the electric field strength, the RF frequency and the filter dimension. Using the experimental transport data for Li+ /Xe and Cs+ /Xe, the formula was tested and we find that it adequately accounts for the degree of ion separation achieved by the filter at high gas pressures. The variation of the profiles of the arrival time spectra for Li+, Na+ and Cs+ ions in C02, obtained by our drift-tube experiments, also supports this analysis.

Electric Trapping and Lysing of Cells in a Microchannel Constriction

2009 ◽  
Author(s):  
Christopher Church ◽  
Junjie Zhu ◽  
Guohui George Huang ◽  
Gaoyan Wang ◽  
Tzuen-Rong Jeremy Tzeng ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Cell Concentration ◽  
Ac Electric Fields ◽  
Ac Electric Field ◽  
Electrical Lysis ◽  
Smooth Switching ◽  
Dc Component ◽  
High Electric Fields ◽  
Pressure Driven Flow

Cell lysis is a necessary step in the analysis of intracellular contents. It has been recently demonstrated in microfluidic devices using four methods: chemical lysis, mechanical lysis, thermal lysis, and electrical lysis [1]. The locally high electric fields needed for electrical lysis have been achieved using micro-electrodes and micro-constrictions for pulsed and continuous DC electric fields, respectively. However, since the two determining factors of electrical lysis are field strength and exposure time, opposing pressure-driven flow must often be used in pure DC lysis to reduce the velocity of the cells and to ensure the cells spend sufficient time in the high electric field region [1,2]. Using DC-biased AC fields can easily fulfill these requirements as only the DC component contributes to cell electrokinetic transport. Prior to lysis, cell concentration can be increased by trapping using dielectrophoresis (DEP), which may occur with either DC or DC-biased AC electric fields [3,4]. This operation is useful in cases where the cell supply is limited or when the cell concentration is too low in general. In this work, red blood cells are used to demonstrate the smooth switching between electrical lysing and trapping in a microchannel constriction. The transition between lysis and trapping is realized by tuning the DC component in a DC-biased AC electric field.

Atomic Spectroscopy in the FIM

1986 ◽  
Vol 44 ◽  
pp. 758-761
Author(s):  
J. J. Hren ◽  
S. D. Walck
Keyword(s):  
Electron Microscope ◽  
Electric Fields ◽  
Atom Probe ◽  
Atomic Spectroscopy ◽  
Single Atom ◽  
Statistical Sampling ◽  
Commercial Instrument ◽  
Available Technology ◽  
High Electric Fields ◽  
Field Ion Microscope

The field ion microscope (FIM) has had the ability to routinely image the surface atoms of metals since Mueller perfected it in 1956. Since 1967, the TOF Atom Probe has had single atom sensitivity in conjunction with the FIM. “Why then hasn't the FIM enjoyed the success of the electron microscope?” The answer is closely related to the evolution of FIM/Atom Probe techniques and the available technology. This paper will review this evolution from Mueller's early discoveries, to the development of a viable commercial instrument. It will touch upon some important contributions of individuals and groups, but will not attempt to be all inclusive. Variations in instrumentation that define the class of problems for which the FIM/AP is uniquely suited and those for which it is not will be described. The influence of high electric fields inherent to the technique on the specimens studied will also be discussed. The specimen geometry as it relates to preparation, statistical sampling and compatibility with the TEM will be examined.

LBE for Generalized Hydrodynamics

2018 ◽  
Author(s):  
Sauro Succi
Keyword(s):  
Potential Energy ◽  
Electric Fields ◽  
Chemical Reactions ◽  
Soft Matter ◽  
Fluid Motion ◽  
Life Sciences ◽  
Scientific Discipline ◽  
The Past ◽  
Generalized Hydrodynamics ◽  
Internal Forces

This chapter presents the main techniques to incorporate the effects of external and/or internal forces within the LB formalism. This is a very important task, for it permits us to access a wide body of generalized hydrodynamic applications whereby fluid motion couples to a variety of additional physical aspects, such as gravitational and electric fields, potential energy interactions, chemical reactions and many others. It should be emphasized that while hosting a broader and richer phenomenology than “plain” hydrodynamics, generalized hydrodynamics still fits the hydrodynamic picture of weak departure from suitably generalized local equilibria. This class is all but an academic curiosity; for instance, it is central to the fast-growing science of Soft Matter, a scientific discipline which has received an impressive boost in the past decades, under the drive of micro- and nanotechnological developments and major strides in biology and life sciences at large.

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