Quantifying particle sorting in microbubble streaming flows

Thameem, Raqeeb Muddassir

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https://hdl.handle.net/2142/89089 Copy

Description

Title

Quantifying particle sorting in microbubble streaming flows

Author(s)

Thameem, Raqeeb Muddassir

Issue Date

2015-12-11

Director of Research (if dissertation) or Advisor (if thesis)

Hilgenfeldt, Sascha

Department of Study

Mechanical Science & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Microfluidics
• Acoustics
• Streaming
• Hydrodynamics
• Experimental fluid mechanics
• Microbubbles
• Sorting
• Oscillatory flow

Abstract

This work seeks to characterize and model the size-dependent behaviour of microparticles in a bubble streaming flow. We show that in microchannels, the steady streaming flow generated by an ultrasonically driven semicylindrical microbubble can be combined with a Poiseuille flow to achieve tunable, high throughput, size-sensitive sorting and trapping of particles much smaller than the bubble itself. We propose a simple geometric mechanism, based on flow speeds and channel geometry, that reliably predicts the sorting behaviour seen in experiment. It is also shown that an asymptotic theory that incorporates the device geometry and superimposed channel flow accurately models key flow features such as peak speeds and particle trajectories. Finally, the forces acting on particles on oscillatory time scales are determined experimentally using a novel method in which the trajectories of small and large particles are compared. These forces are found to scale quadratically with both oscillatory flow speed and particle size. Simulations of particle trajectories are used to show that Saffman lift is not primarily responsible for these forces. Instead, a lubrication theory is proposed that is able to predict both the magnitude and dependence of forces on particles.

Graduation Semester

2015-12

Type of Resource

text

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http://hdl.handle.net/2142/89089

Copyright and License Information

Copyright 2015 Raqeeb Muddassir Thameem

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