A compact model for electroosmotic flows in microfluidic devices

Qiao, Rui; Aluru, N. R.

doi:10.1088/0960-1317/12/5/318

Cited by 53 publications

(40 citation statements)

References 9 publications

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“…5. As also discussed by Qiao and Aluru [50], this hypothesis is amply verified as * d is very small, i.e. of the order of 100 nm [47,51], therefore about three orders of magnitude smaller than the channel height and two orders smaller than the viscous layers generated by the travelling waves.…”

Section: Application To Flow Mixingmentioning

confidence: 58%

Streamwise-travelling viscous waves in channel flows

Riccó

Hicks

2018

J Eng Math

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The unsteady viscous flow induced by streamwise-travelling waves of spanwise wall velocity in an incompressible laminar channel flow is investigated. Wall waves belonging to this category have found important practical applications, such as microfluidic flow manipulation via electro-osmosis and surface acoustic forcing and reduction of wall friction in turbulent wall-bounded flows. An analytical solution composed of the classical streamwise Poiseuille flow and a spanwise velocity profile described by the parabolic cylinder function is found. The solution depends on the bulk Reynolds number R, the scaled streamwise wavelength λ, and the scaled wave phase speed U . Numerical solutions are discussed for various combinations of these parameters. The flow is studied by the boundary-layer theory, thereby revealing the dominant physical balances and quantifying the thickness of the near-wall spanwise flow. The Wentzel-Kramers-Brillouin-Jeffreys (WKBJ) theory is also employed to obtain an analytical solution, which is valid across the whole channel. For positive wave speeds which are smaller than or equal to the maximum streamwise velocity, a turning-point behaviour emerges through the WKBJ analysis. Between the wall and the turning point, the wall-normal viscous effects are balanced solely by the convection driven by the wall forcing, while between the turning point and the centreline, the Poiseuille convection balances the wall-normal diffusion. At the turning point, the Poiseuille convection and the convection from the wall forcing cancel each other out, which leads to a constant viscous stress and to the break down of the WKBJ solution. This flow regime is analysed through a WKBJ composite expansion and the Langer method. The Langer solution is simpler and more accurate than the WKBJ composite solution, while the latter quantifies the thickness of the turning-point region. We also discuss how these waves can be generated via surface acoustic forcing and electro-osmosis and propose their use as microfluidic flow mixing devices. For the electro-osmosis case, the Helmholtz-Smoluchowski velocity at the edge of the Debye-Hückel layer, which drives the bulk electrically neutral flow, is obtained by matched asymptotic expansion.

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Section: Application To Flow Mixingmentioning

confidence: 58%

Streamwise-travelling viscous waves in channel flows

Riccó

Hicks

2018

J Eng Math

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“…Traditional (continuous-flow) microfluidic technologies are based on the continuous flow of liquid through micro-fabricated channels [8], [10]- [16]. Continuous-flow systems are inherently difficult to integrate because the parameters that govern flow field (e.g.…”

Section: A Continuous-flow Microfluidicsmentioning

confidence: 99%

Design Automation and Test Solutions for Digital Microfluidic Biochips

Chakrabarty

2010

IEEE Trans. Circuits Syst. I

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Abstract-Microfluidics-based biochips are revolutionizing high-throughput sequencing, parallel immunoassays, blood chemistry for clinical diagnostics, and drug discovery. These devices enable the precise control of nanoliter volumes of biochemical samples and reagents. They combine electronics with biology, and they integrate various bioassay operations, such as sample preparation, analysis, separation, and detection. Compared to conventional laboratory procedures, which are cumbersome and expensive, miniaturized biochips offer the advantages of higher sensitivity, lower cost due to smaller sample and reagent volumes, system integration, and less likelihood of human error. This tutorial paper provides an overview of droplet-based "digital" microfluidic biochips. It describes emerging computer-aided design (CAD) tools for the automated synthesis and optimization of biochips from bioassay protocols. Recent advances in fluidic-operation scheduling, module placement, droplet routing, pin-constrained chip design, and testing are presented. These CAD techniques allow biochip users to concentrate on the development of nanoscale bioassays, leaving chip optimization and implementation details to design-automation tools.

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“…This model is based on earlier presented results (Qiao and Aluru 2002;Ajdari 2003;Besselink et al 2004;Kohlheyer et al 2005). Therefore, it is described only briefly.…”

Section: Analytical Modelmentioning

confidence: 99%

A microfluidic device for array patterning by perpendicular electrokinetic focusing

Kohlheyer

Unnikrishnan

Besselink

et al. 2007

Microfluid Nanofluid

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This paper describes a microfluidic chip in which two perpendicular laminar-flow streams can be operated to sequentially address the surface of a flowchamber with semi-parallel sample streams. The sample streams can be controlled in position and width by the method of electrokinetic focusing. For this purpose, each of the two streams is sandwiched by two parallel sheath flow streams containing just a buffer solution. The streams are being electroosmotically pumped, allowing a simple chip design and a setup with no moving parts. Positioning of the streams was adjusted in real-time by controlling the applied voltages according to an analytical model. The perpendicular focusing gives rise to overlapping regions, which, by combinatorial (bio) chemistry, might be used for fabrication of spot arrays of immobilized proteins and other biomolecules. Since the patterning procedure is done in a closed, liquid filled flow-structure, array spots will never be exposed to air and are prevented from drying. With this device configuration, it was possible to visualize an array of 49 spots on a surface area of 1 mm 2 . This article describes the principle, fabrication, experimental results, analytical modeling and numerical simulations of the microfluidic chip.

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A compact model for electroosmotic flows in microfluidic devices

Cited by 53 publications

References 9 publications

Streamwise-travelling viscous waves in channel flows

Streamwise-travelling viscous waves in channel flows

Design Automation and Test Solutions for Digital Microfluidic Biochips

A microfluidic device for array patterning by perpendicular electrokinetic focusing

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