AC Electrokinetics for Biosensors

Fluids Engineering ◽

10.1115/imece2004-62013 ◽

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.

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Manipulation of Clinical Materials Using AC Electrokinetics

ASME 2010 First Global Congress on NanoEngineering for Medicine and Biology ◽

10.1115/nemb2010-13367 ◽

2010 ◽

Author(s):

Mandy L. Y. Sin ◽

Pak Kin Wong

Keyword(s):

Experimental Data ◽

Sample Preparation ◽

Theoretical Prediction ◽

Fluid Motion ◽

Lab On A Chip ◽

Clinical Samples ◽

Electrochemical Reactions ◽

Ac Electrokinetics ◽

Wide Range ◽

Electrothermal Flow

AC electrokinetics is a promising approach for sample preparation and reaction enhancement in lab-on-a-chip devices. However, relative little has been done on the electrokinetic manipulation of physiological fluids and buffers with similar properties, such as conductivity. Herein, electrokinetic manipulation of fluids with a wide range of conductivities has been studied as a function of voltage and frequency. AC electrothermal flow is determined to dominate the fluid motion when the applied frequency of the AC potential is above 100 kHz. Interestingly, experimental data deviate from theoretical prediction for fluids with high conductivities (> 1 Sm−1). The deviation can be understood by voltage modulated electrochemical reactions and should be accounted for when manipulating clinical materials with high conductivities. The study will provide useful in sights in designing lab-on-a-chip devices for manipulating clinical samples in the future.

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

Materials ◽

10.1115/imece2003-42932 ◽

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.

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AC Electrokinetic Pumps for Micro/NanoFluidics

Microelectromechanical Systems ◽

10.1115/imece2004-61836 ◽

2004 ◽

Cited By ~ 1

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.

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

Materials: Processing, Characterization and Modeling of Novel Nano-Engineered and Surface Engineered Materials ◽

10.1115/imece2002-39617 ◽

2002 ◽

Cited By ~ 1

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.

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Editorial for the Special Issue on AC Electrokinetics in Microfluidic Devices

Micromachines ◽

10.3390/mi10050345 ◽

2019 ◽

Vol 10 (5) ◽

pp. 345

Author(s):

Antonio Ramos ◽

Pablo García-Sánchez

Keyword(s):

Electric Fields ◽

Microfluidic Devices ◽

Special Issue ◽

Small Particles ◽

Ac Electrokinetics ◽

Ac Electric Fields

The use of AC electric fields for manipulating and/or characterizing liquids and small particles in suspension is well-known [...]

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LBE for Generalized Hydrodynamics

10.1093/oso/9780199592357.003.0025 ◽

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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