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Research Papers

A Study on Micromixing Utilizing Marangoni Effect Induced on Gas–Liquid Free Interfaces

[+] Author and Article Information
Takashi Yamada

Department of Engineering Science and Mechanics,
Shibaura Institute of Technology,
3-7-5 Toyosu, Ko-to ku,
Tokyo 135-8548, Japan
e-mail: na12104@shibaura-it.ac.jp

Naoki Ono

Department of Engineering Science and Mechanics,
Shibaura Institute of Technology,
3-7-5 Toyosu, Ko-to ku,
Tokyo 135-8548, Japan
e-mail: naokiono@shibaura-it.ac.jp

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MICRO- AND NANO-MANUFACTURING. Manuscript received April 4, 2014; final manuscript received January 20, 2015; published online February 23, 2015. Assoc. Editor: John P. Coulter.

J. Micro Nano-Manuf 3(2), 021003 (Jun 01, 2015) (11 pages) Paper No: JMNM-14-1022; doi: 10.1115/1.4029684 History: Received April 04, 2014; Revised January 20, 2015; Online February 23, 2015

Traditionally, micromixing has been thought to be governed by molecular diffusion. However, the authors consider that advection is important in the mixing enhancement and applicable to micromixing devices in many industrial fields. Here, the Marangoni convection, a type of shear flow induced at gas–liquid free interfaces, is introduced as an additional source for micromixing. To evaluate the proposal, two liquids with different surface tensions values were mixed in a capillary channel fabricated by the photolithography technique. The utility of Marangoni convection was confirmed in rapid mixing by the flow experiments.

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References

Figures

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Fig. 1

Notation describing a stationary spherical bubble fixed in a flowing fluid

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Fig. 2

Stream lines near a spherical bubble of radius 0.0002 mm in a three-dimensional spherical coordinate system. The bubble is intercepted by steady flow with velocity 0.002 m/s in the x direction (Fig. 1) with surface tension distribution dS/dx at the x (horizontal) direction: (a) dS/dx = 1.00, (b) dS/dx = 0.20, (c) dS/dx = 0.00, (d) dS/dx = −0.04, (e) dS/dx = −0.07, and (f) dS/dx = −0.20.

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Fig. 8

A series of photographs at the bending point in type-A channel during the flow experiment using the two test fluids having different surface tension values at 0.1 s intervals from (a) to (j). Volume flow rate: 0.8 μl/min in each inlet.

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Fig. 9

A series of photographs at the bending point in type-B channel during the flow experiment using the two test fluids having different surface tension values at 0.1 s intervals from (a) to (j). Volume flow rate: 0.8 μl/min in each inlet.

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Fig. 10

A series of photographs at the bending point in type-C channel during the flow experiment using the two test fluids having different surface tension values at 0.1 s intervals from (a) to (j). Volume flow rate: 0.8 μl/min in each inlet.

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Fig. 11

A series of photographs at each point of the outlet channel, 0.0 mm–3.0 mm from the bending point during flow experiments using two test fluids with different surface tensions in each channel: (above) type-A, (middle) type-B, and (below) type-C channel. Volume flow rate: 0.8 μl/min at each inlet.

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Fig. 12

Maximum concentration difference of blue dye at several distances along the outlet channel (from the bending point) during mixing experiments in type-A, -B, and -C channels

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Fig. 7

Schematic of the experimental apparatus

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Fig. 6

Image of PDMS cast installed with the type-A channel (magnified 10 × under a laser microscope (Olympus LEXT 4000); three-dimensional views of the crossing point of each channel, where the mixing device is installed: (a) general view, (b) and (c) side views, and (d) measurements of the test channel in the cross-sectional direction of the air chamber

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Fig. 5

Fabrication of test channels by the photolithography method: (a) and (b) mold of the structure retaining the shape of the type-A channel, (c) casting part composed of polydimethylsiloxane (PDMS) rubber, and (d) completed test channel

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Fig. 4

Design of the type-A channel: (a) general view and (b) details of the bending point of region in the type-B channel, including the bubble holding section as air chamber and air channel (containing the bubble). Vertical cross-sectional views of the flection flexion area in the L-shaped region of the three test channels with the dimensions in details, (c) type-A channel, (d) type-B channel, and (e) type-C channel.

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Fig. 3

Construct of the new mixing device: (a) basic design at the elbow point of the new test channel (three-dimensional view) and (b) the expected mechanism of the new mixing device

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Fig. 13

(a) Definition of cross section A–B in the outlet channel, 0.5 mm from the bending point in the type-B channel and (b) distribution of the blue dye concentrations at several points along the cross section A–B during the mixing experiments

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Fig. 14

Assuming mechanism of causing a specific flow pattern at upper region of the flexion in the flow experiment using type-A channel

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