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Proceedings Paper

Vibration effect on cross-flow and co-flow focusing mechanism for droplet generation
Author(s): Alinaghi Salari; Colin Dalton
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Paper Abstract

Microbubbles are widely used in many industries such as water treatment, drug coating, and ultrasonic contrast agents. Cross-flow focusing and co-flow focusing are considered basic mechanisms used for microbubble generation. Typically, to achieve micron-sized droplets requires structure dimensions in the same order of magnitude of the desired droplet sizes. In this paper we report a method of applying an external vibration to a cross-flow and co-flow focusing structure, which allows for smaller droplets to be generated. The junction dimension was 700×400 μm, and the channel width was 800 μm. The two assumed fluids are selected in a way that the Capillary number is high (Ca>10) to make use of necking effect occurred in the downstream. Linear vibration was exerted on the microchannel structure in the direction of central flow. A 2D structure was simulated using finite element software, and the numerical approach was then verified by comparing the experimental data of a typical cross-flow focusing structure taken from our previous study with the corresponding simulation assuming the same parameters. The results show that although the droplet generation regime depends on flow ratio (Qa/Qw) and vibration parameter (ampl×freq), Capillary number also has a significant effect on the regime. Briefly, applying a low-cost linear vibration to the conventional flow focusing structures can be used as an accurate controlling technique for increasing the chance of droplet generation. In fact, vibration motion can change the flow regime and breakup mechanism. It can also change the breakup point at which the droplets are formed.

Paper Details

Date Published: 5 March 2015
PDF: 6 pages
Proc. SPIE 9320, Microfluidics, BioMEMS, and Medical Microsystems XIII, 93201B (5 March 2015); doi: 10.1117/12.2081537
Show Author Affiliations
Alinaghi Salari, Univ. of Calgary (Canada)
Colin Dalton, Univ. of Calgary (Canada)

Published in SPIE Proceedings Vol. 9320:
Microfluidics, BioMEMS, and Medical Microsystems XIII
Bonnie L. Gray; Holger Becker, Editor(s)

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