Fast microfluidic mixers based on acoustically drivem microbubbles

Open Access
Author:
Ahmed, Daniel
Graduate Program:
Engineering Science
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 27, 2009
Committee Members:
  • Dr Tony Huang, Thesis Advisor
Keywords:
  • microfluidics
  • acoustic-bubbles
  • micromixers
Abstract:
Due to the low Reynolds number associated with microscale fluid flow, it is difficult to rapidly and homogenously mix two fluids. The thesis discusses fast and homogenized mixing devices through the use of a bubble-based microfluidic structure. We have designed two micromixers prototypes. (1) This micromixing device worked by trapping air bubbles within the pre-designed grooves on the sidewalls of the channel. When acoustically driven, the membranes (liquid/air interfaces) of these trapped bubbles started to oscillate. The bubbles’ oscillation resulted in a microstreaming phenomenonstrong pressure and velocity fluctuations in the bulk liquid, thus giving rise to fast and homogenized mixing of two side-by-side flowing fluids. The performance of the mixer was characterized by mixing deionized water and ink at different flow rates. The mixing time was measured to be as small as 120 ms. (2) The device operates by trapping a single bubble within a “horse-shoe” structure located between two laminar flows inside a microchannel. Acoustic waves then excite the trapped air bubble at its resonance frequency, resulting in acoustic streaming which disrupts the laminar flows and triggers the two fluids to mix. Due to this technique’s simple design, excellent mixing performance, and fast mixing speed (a few milliseconds), our single-bubble-based acoustic micromixer will be useful in many biochemical studies and applications. Mixing performance, and fast mixing speed (7 milliseconds), our single-bubble-based acoustic micromixer will be useful in many biochemical studies and applications.