Recent Applications of AC Electrokinetics in Biomolecular Analysis on Microfluidic Devices

Sasaki, Naoki

doi:10.2116/analsci.28.3

Cited by 12 publications

(12 citation statements)

References 55 publications

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“…Since no dipole moment is required, fDEP does not require a nonuniform field to produce a net motion. We now demonstrate that the frequency and electricaldependent fDEP displacement at a single polarizable aqueous liquid interface is directly proportional to this polarization factor for all field frequencies observed in this work (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Unlike conventional dielectrophoresis where particle motion is driven by the interaction of the induced particle dipole moment with a nonuniform electric field, for an electrical interface the electric force and the observed liquid motion results from the electric field interacting with induced surface charge at a single liquid interface.…”

Section: Discussionmentioning

confidence: 58%

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Fluidic dielectrophoresis: The polarization and displacement of electrical liquid interfaces

2015

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Traditional particle-based dielectrophoresis has been exploited to manipulate bubbles, particles, biomolecules, and cells. In this work, we investigate analytically and experimentally how to utilize Maxwell-Wagner polarization to initiate fluidic dielectrophoresis (fDEP) at electrically polarizable aqueous liquid-liquid interfaces. In fDEP, an AC electric field is applied across a liquid electrical interface created between two coflowing fluid streams with different electrical properties. When potentials as low as 2 volts are applied, we observe a frequency-dependent interfacial displacement that is dependent on the relative differences in the electrical conductivity (Δσ) and dielectric constant (Δɛ) between the two liquids. At low frequency this deflection is independent of dielectric constant, while at high frequency it is independent of electrical conductivity. At intermediate frequencies, we observe an fDEP cross-over frequency that is independent of applied voltage, sensitive to both fluid electrical properties, and where no displacement is observed. An analytical fDEP polarization model is presented that accurately predicts the liquid interfacial cross-over frequency, the dependence of interfacial displacement on liquid electrical conductivity and dielectric constant, and accurately scales the measured fDEP displacement data. The results show that miscible aqueous liquid interfaces are capable of polarizing under AC electric fields, and being precisely deflected in a direction and magnitude that is dependent on the applied electric field frequency.

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Section: Discussionmentioning

confidence: 58%

“…(10), at the microscale the electrolyte can be regarded as quasi-electroneutral and the electric potential satisfies Laplace's equation, given by Eq. (11). In onedimension, neglecting variations in the potential over the channel height (y-direction), we have to solve d 2 ⌽ i dx 2 = 0 for each fluid stream.…”

Section: One Dimensional Modelmentioning

confidence: 99%

Fluidic dielectrophoresis: The polarization and displacement of electrical liquid interfaces

2015

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“…A number of micromixers have been reported to address such issues . Among these, electrokinetic micromixers have been widely studied . In general, electrokinetic phenomena involve the motion of liquids or particles under an AC or DC electric field.…”

Section: Introductionmentioning

confidence: 99%

Fluid mixing using AC electrothermal flow on meandering electrodes in a microchannel

Sasaki

Kitamori²,

Kim³

2012

Electrophoresis

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The mixing of fluids using AC electrothermal flow (AC-ETF) is presented. A pair of coplanar electrodes with a sinusoidal interelectrode gap was used to enhance the mixing in a microchannel. To demonstrate the performance of the mixer, conventional dilution experiments were conducted using Texas Red-labeled dextran. The dependence of mixing on the salt concentration (10(-3) ∼ 10(-1) mol dm(-3) ) of the solutions and frequency (100 kHz ∼ 5 MHz) of the applied voltage were investigated. AC-ETF was responsible for the mixing at salt concentrations >10(-2) mol dm(-3) , whereas the effect of AC-EOF was suggested to play a role at concentrations <10(-2) mol dm(-3) in the low-frequency region. The fluorogenic reaction of human serum albumin (HSA) with SYPRO Red in the mixer was also examined, and results showed that enrichment of fluorescence intensity and an almost uniform distribution of stained HSA were achieved. The present mixer can be employed as a powerful tool to facilitate efficient chemical and biomedical analysis on microfluidic devices.

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“…This two‐compartment model includes an additional differential equation to account for the time variation of the local analyte concentration due to molecules having to diffuse into the reaction zone as the local concentration decreases owing to binding. AC electrokinetic effects can be used to manipulate biomolecules or manipulate the fluid flow such that the local concentration is increased, overcoming the limitations due to mass transport or simply changing the binding equilibrium, resulting in a higher density of bound target molecules which in turn enhances the detection limit for a certain value of bulk analyte concentration. The two main strategies that are commonly used are dielectrophoretic (DEP) manipulation of biomolecules and AC electro‐osmotic flow (ACEOF) to drive the motion of molecules to the bioFET surface, overcoming the diffusion‐limited transport and increasing the local analyte concentration.…”

Section: Binding Kineticsmentioning

confidence: 99%

Performance limitations for nanowire/nanoribbon biosensors

Rajan

Duan

Reed

2013

WIREs Nanomed Nanobiotechnol

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Field-effect transistor-based biosensors (bioFETs) have shown great promise in the field of fast, ultra-sensitive, label-free detection of biomolecules. Reliability and accuracy, when trying to measure small concentrations, is of paramount importance for the translation of these research devices into the clinical setting. Our knowledge and experience with these sensors has reached a stage where we are able to identify three main aspects of bioFET sensing that currently limit their applications. By considering the intrinsic device noise as a limitation to the smallest measurable signal, we show how various parameters, processing steps and surface modifications, affect the limit of detection. We also introduce the signal-to-noise ratio of bioFETs as a universal performance metric, which allows us to gain better insight into the design of more sensitive devices. Another aspect that places a limit on the performance of bioFETs is screening by the electrolyte environment, which reduces the signal that could be potentially measured. Alternative functionalization and detection schemes that could enable the use of these charge-based sensors in physiological conditions are highlighted. Finally, the binding kinetics of the receptor-analyte system are considered, both in the context of extracting information about molecular interactions using the bioFET sensor platform and as a fundamental limitation to the number of molecules that bind to the sensor surface at steady-state conditions and to the signal that is generated. Some strategies to overcome these limitations are also proposed. Taken together, these performance-limiting issues, if solved, would bring bioFET sensors closer to clinical applications.

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Recent Applications of AC Electrokinetics in Biomolecular Analysis on Microfluidic Devices

Cited by 12 publications

References 55 publications

Fluidic dielectrophoresis: The polarization and displacement of electrical liquid interfaces

Fluidic dielectrophoresis: The polarization and displacement of electrical liquid interfaces

Fluid mixing using AC electrothermal flow on meandering electrodes in a microchannel

Performance limitations for nanowire/nanoribbon biosensors

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