AC Electroosmotic Generated In-Plane Microvortices for Stationary or Continuous Fluid Mixing

Huang, Shih-Hao; Wang, Shou-Kai; Khoo, Hwa Seng; Tseng, Fan‐Gang

doi:10.1109/sensor.2007.4300392

Cited by 13 publications

(16 citation statements)

References 10 publications

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“…Similar electro-osmotic microfluidic mixers have been studied by Sasaki et al [52] and Huang et al [53]. Sasaki et al [52] employed meandering electrodes to mix two microstreams and stress the importance of obtaining analytical results for the fluid flow in order to optimize the mixing performance, while Huang et al [53] generated in-plane microvortices to prove that up to 30-fold mixing enhancement can be achieved compared to mixing due to diffusion only. The spanwise spatial pattern displayed in Fig.…”

Section: Application To Flow Mixingmentioning

confidence: 98%

“…11(right) can be achieved by utilizing thin strips of different glass coatings and spatially modulated electric fields [18,20]. Typical frequencies of electro-osmosis actuators are of the order of 10 Hz [23,53] and the streamwise length of the microelectrode arrays, which define the forcing wavelength, can be in the range of 100-500 µm. The flow parameters therefore correspond to ratios ε = λ/R in the range of 0.1-1 and to U of order unity.…”

Section: Application To Flow Mixingmentioning

confidence: 99%

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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: 98%

Section: Application To Flow Mixingmentioning

confidence: 99%

Streamwise-travelling viscous waves in channel flows

Riccó

Hicks

2018

J Eng Math

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“…The ability to accelerate mass exchange among particles can potentially be used in mesoscopic materials mixing, as reported in previous works 45,46 . Figure S12 (Supplementary Information) shows the transformation process from individual nanoparticles (diameter = 300 nm) to a square lattice of particle clusters (δ ≈ 10 μm and P = 20 mW).…”

Section: Applications For Optofluidic Arrangement and Mixingmentioning

confidence: 85%

Hybrid optofluidics and three-dimensional manipulation based on hybrid photothermal waveguides

et al. 2018

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Despite enormous breakthroughs in lab-on-a-chip techniques, light-driven manipulation faces two long-standing challenges: the ability to achieve both multiform manipulation and tunable manipulation range and the means to avoid potential thermal damage to the targets. By harnessing the optical heating of hybrid photothermal waveguides (HPW), we develop a hybrid optofluidic technique involving buoyancy and thermocapillary convection to achieve fluid transport with controllable modes and tunable strength. Switching of the optofluidic mode from buoyancy to thermocapillary convection, namely, from vertical to horizontal vortices, is employed for three-dimensional manipulation. The strong confinement and torque in the vortices are capable of trapping and rotating/spinning particles at the vortex centers rather than the HPW. Buoyancy convection provides a trapping circle to achieve collective trapping and vertical rotation/spin, while thermocapillary convection offers a trapping lattice to achieve distributed trapping and horizontal rotation/spin. By integrating micro/nanoparticles with various properties and sizes, further investigations of the optofluidic arrangement, mixing, and synthesis will broaden the potential applications of the hybrid optofluidic technique in the fields of lab-on-a-chip, materials science, chemical synthesis and analysis, photonics, and nanoscience.

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“…Sasaki et al [45] demonstrated experimental evidence of enhanced mixing due to a meandering electrode pair on the bottom of the "Y" channel ( Figure 23), around which ac electroosmotic flow is created. More complex patterns of microelectrodes on the channel walls were also tried by Huang et al [46] for further enhancement of mixing ( Figure 24).…”

Section: Geometry Effectmentioning

confidence: 99%

A Review on Mixing in Microfluidics

2010

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Small-scale mixing is of uttermost importance in bio-and chemical analyses using micro TAS (total analysis systems) or lab-on-chips. Many microfluidic applications involve chemical reactions where, most often, the fluid diffusivity is very low so that without the help of chaotic advection the reaction time can be extremely long. In this article, we will review various kinds of mixers developed for use in microfluidic devices. Our review starts by defining the terminology necessary to understand the fundamental concept of mixing and by introducing quantities for evaluating the mixing performance, such as mixing index and residence time. In particular, we will review the concept of chaotic advection and the mathematical terms, Poincare section and Lyapunov exponent. Since these concepts are developed from nonlinear dynamical systems, they should play important roles in devising microfluidic devices with enhanced mixing performance. Following, we review the various designs of mixers that are employed in applications. We will classify the designs in terms of the driving forces, including mechanical, electrical and magnetic forces, used to control fluid flow upon mixing. The advantages and disadvantages of each design will also be addressed. Finally, we will briefly touch on the expected future development regarding mixer design and related issues for the further enhancement of mixing performance.

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AC Electroosmotic Generated In-Plane Microvortices for Stationary or Continuous Fluid Mixing

Cited by 13 publications

References 10 publications

Streamwise-travelling viscous waves in channel flows

Streamwise-travelling viscous waves in channel flows

Hybrid optofluidics and three-dimensional manipulation based on hybrid photothermal waveguides

A Review on Mixing in Microfluidics

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