Chapter Six
Flow Control in Biomedical Microdevices
using Thermally Responsive Fluids
Vahid Bazargan
and Boris Stoeber
Department of Mechanical Engineering, The University of British Columbia,
Vancouver, BC V6T 1Z4, Canada
Department of Electrical and Computer Engineering,
The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
Microfluidic lab-on-a-chip systems for biomedical applications require specialized
flow control devices. While several those for microfluidic devices have been devel-
oped to date, this text focuses on flow control concepts based on thermally responsive
polymer solutions. In particular, flow control concepts using the thermally triggered
reversible phase change of aqueous solutions of the polymer Pluronic will be dis-
cussed. The three example microflow control concepts presented in this text include
selective heating of small regions of microfluidic channels, which leads to localized
gel formation in these channels and reversible channel blockage. Furthermore, a
timed channel blockage due to viscous heating within the flow will be described.
Finally, a concept for cross-channel transport of Particles such as cells is presented
that relies on the continuous regeneration of a gel wall at the diffusive interface of
two co-streaming fluids in a microfluidic channel.
Transport of biological materials in microfluidic channels on-chip has gained
increasing popularity over the past decade. Many efforts aim at building
integrated microfluidic devices that combine several functions such as sample
preparation, separation and detection on a single chip, to form a so-called “lab-
on-a-chip”. Highly integrated lab-on-a-chip devices are also known as micro total
analysis systems (microTAS). These systems can manipulate sample volumes of
less than picoliters, reducing the amount of required sample and analyte that are of
ten difficult and expensive to acquire. By integrating conventional lab bench anal-
ysis methods on-chip, cost for laboratory equipment can be significantly reduced,
and automatic sample handling between the different lab processes requires less
Biomaterials for MEMS, Edited b y M. Chiao and J.-C. Chiao
Copyright © 2011 by Pan Stanford Publishing Pte. Ltd.
SO13997_text.indd 123SO13997_text.indd 123 26/01/2011 3:50 PM26/01/2011 3:50 PM

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