Frequency dependence and frequency control of microbubble streaming flows

Cheng Wang, Bhargav Rallabandi, Sascha Hilgenfeldt

Research output: Contribution to journalArticle

Abstract

Steady streaming from oscillating microbubbles is a powerful actuating mechanism in microfluidics, enjoying increased use due to its simplicity of manufacture, ease of integration, low heat generation, and unprecedented control over the flow field and particle transport. As the streaming flow patterns are caused by oscillations of microbubbles in contact with walls of the set-up, an understanding of the bubble dynamics is crucial. Here we experimentally characterize the oscillation modes and the frequency response spectrum of such cylindrical bubbles, driven by a pressure variation resulting from ultrasound in the range of 1 kHz 100 kHz. We find that (i) the appearance of 2D streaming flow patterns is governed by the relative amplitudes of bubble azimuthal surface modes (normalized by the volume response), (ii) distinct, robust resonance patterns occur independent of details of the set-up, and (iii) the position and width of the resonance peaks can be understood using an asymptotic theory approach. This theory describes, for the first time, the shape oscillations of a pinned cylindrical bubble at a wall and gives insight into necessary mode couplings that shape the response spectrum. Having thus correlated relative mode strengths and observed flow patterns, we demonstrate that the performance of a bubble micromixer can be optimized by making use of such flow variations when modulating the driving frequency.

Original languageEnglish (US)
Article number022002
JournalPhysics of Fluids
Volume25
Issue number2
DOIs
StatePublished - Feb 1 2013

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frequency control
Flow patterns
bubbles
flow distribution
oscillations
Heat generation
Microfluidics
Frequency response
Flow fields
Ultrasonics
heat generation
frequency response
coupled modes

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Frequency dependence and frequency control of microbubble streaming flows. / Wang, Cheng; Rallabandi, Bhargav; Hilgenfeldt, Sascha.

In: Physics of Fluids, Vol. 25, No. 2, 022002, 01.02.2013.

Research output: Contribution to journalArticle

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