Biomaterials for MEMS

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

E-mail: [e-mail]

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.

6.1 INTRODUCTION

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.

www.panstanford.com

978-981-4241-46-5

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