Microfluidics E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 643

Veröffentlichungsjahr: 2013

Beschreibung

The recent development of microscale technologies makes it possible to design complex microsystems devoted to transport, dosing, mixing, analysis or even synthesis of fluids. Applications are numerous and exist in almost every industrial field, from biotechnology and healthcare to aeronautics and advanced materials manufacturing. Microfluidics is a relatively new research area, usually comprising work with microsystems and involving internal fluid flows with characteristic dimensions of the order of one micrometer (1 x 10 ¯-6 m). This book provides engineers and researchers with a range of tools for modeling, experimenting on, and simulating these microflows, as a preliminary step in designing and optimizing fluidic microsystems. The various consequences of miniaturization on the hydrodynamics of gas, liquid or two-phase flows, as well as on associated heat transfer phenonema, are analyzed. The book is illustrated with examples that demonstrate the wide diversity of applications, and the breadth of novel uses of these fluidic microsystems.

Leseprobe

Table of Contents

Preface

Chapter 1: Introduction to Microflows

1.1. Fluid mechanics, fluidics and microfluidics

1.2. Scaling effects and microeffects

1.3. Original pumping techniques

1.4. Microfabrication and flows

1.5. Microfluidic applications

1.6. Bibliography

Chapter 2: Gaseous Microflows

2.1. Continuum model and molecular model

2.2. Molecular description of a flow

2.3 Continuum description of a flow

2.4. Physical modeling

2.5. Examples of microflows

2.6. Bibliography

Chapter 3: Liquid Microflows: Particularities and Modeling

3.1. Introduction

3.2. Background, liquid microflow physics

3.3. Numerical simulation of microflows

3.4. Non-mechanical active control of microflows

3.5. Conclusions

3.6. Bibliography

Chapter 4: Physiological Microflows

4.1. Description of the microvascular network

4.2. Blood flow: an unusual means of transportation

4.3. Instrumentation

4.4. Description of flows and microcirculatory networks

4.5. The microcirculatory system: an optimized transport network?

4.6. Conclusion

4.7. Bibliography

Chapter 5: Single-phase Heat Transfer

5.1. Introduction

5.2. Heat transfer in channels of conventional sizes

5.3. “Macroeffects” in microchannels: single-phase liquid flows

5.4. Gas microflows: rarefaction and compressibility

5.5. Molecular effects of liquid flows in microchannels

5.6. Electrostatic effects: interfacial electrostatic double layer

5.7. Conclusion

5.8. Acknowledgment

5.9. Bibliography

Chapter 6: Two-Phase Microflows

6.1. Introduction

6.2. Digital versus continuous two-phase microflows

6.3. Basic phenomena

6.4. Some peculiarities of two-phase flows in microchannels

6.5. Bibliography

Chapter 7: Experimental Methods

7.1. Introduction

7.2. Measurements at the microscale: general overview

7.3. Pressure measurements

7.4. Flow rate measurements

7.5. Temperature measurements

7.6. Velocity measurements

7.7. Conclusion

7.8. Acknowledgments

7.9. Bibliography

Chapter 8: Fluidic Microsystems

8.1. Introduction

8.2. Basic modules

8.3. Examples of developments around microsystems

8.4. Conclusion

8.5. Bibliography

Chapter 9: Microsystems in Macroflows Active Control

9.1. Introduction

9.2. Notions of active control

9.3. Microsensors

9.4. Microprobes in the flow

9.5. Actuators

9.6. Conclusion

9.7. Bibliography

List of Authors

Index

First published 2010 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc. Adapted and updated from Microfluidique published 2004 in France by Hermes Science/Lavoisier © LAVOISIER 2004

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:

ISTE LtdJohn Wiley & Sons, Inc.27-37 St George’s Road111 River StreetLondon SW19 4EUHoboken, NJ 07030UKUSAwww.iste.co.ukwww.wiley.com

© ISTE Ltd 2010

The rights of Stéphane Colin to be identified as the author of this work have been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.

Library of Congress Cataloging-in-Publication Data

Microfluidics / edited by Stéphane Colin.

p. cm.

Includes bibliographical references and index.

ISBN 978-1-84821-097-4

1. Microfluidics. I. Colin, Stéphane.

TJ853.4.M53M543 2010

629.8'042--dc22

2010009529

British Library Cataloguing-in-Publication Data

A CIP record for this book is available from the British Library

ISBN 978-1-84821-097-4

Preface

Microfluidics is a recent research area; it has only recently reached a phase of maturity and today it is an extremely active scientific field. It relates to everything that concerns flows in structures or systems involving characteristic dimensions in the order of 1 µm. Until 1990, literature in this domain was still confidential, but in 2010, researchers have access to a very important database, including books presenting the main research results and applications in microfluidics. This book gives more emphasis to the peculiarities of microflows than the applications themselves, which are nevertheless widely cited. The idea is to provide the researcher or engineer with tools for the modeling of microflows, as a preliminary stage for the design of fluidic microsystems.

From a scale analysis, Chapter 1 presents the main consequences of miniaturization on flows in a synthetic manner. Simple scaling effects, which give more weight to quantities often neglected in equations relative to macroscopic flows, are distinguished from real microeffects that require us to take new terms into account and involve original properties, linked for example to rarefaction, electrokinetic or micropolar properties of the flow. It is pointed out that scientific issues are very different for liquid and gas microflows.

Gas microflows are discussed in Chapter 2. This chapter details the modeling of various flow regimes encountered that require a continuum or a molecular approach. Analytical as well as numerical tools are presented. Original pumping techniques, the principles of which are based on thermal properties of rarefied gases, are also explained.

Chapter 3 covers the analysis of the behavior of liquid microflows forms. The role of intermolecular forces is highlighted and electrokinetic phenomena are more specifically detailed: the importance of electric double layers at the wall is shown. The main numerical tools are also presented. Several techniques for the non-mechanical control of liquid microflows, in microchannels or as microdroplets, illustrate the variety of possibilities in the field of liquid microfluidics. Microflows of physiological fluids, including blood, are analyzed in detail in Chapter 4. These particular microflows are characterized by non-Newtonian behavior and by transport in microchannel networks with soft walls.

Miniaturization gives a predominant role to surface effects, to the detriment of volume effects. This dramatically enhances heat transfer efficiency. It allows us, for example, to evacuate high heat fluxes in order to cool high-power electronic components. These aspects are detailed in Chapter 5 for gases as well as liquids.

Chapter 6 deals with two-phase microflows, emphasizing the role of basic phenomena (surface tension, contact angles, etc.). Two-phase flow configurations in microchannels are analyzed and the main applications of two-phase microfluidics conclude this chapter.

Every model should be supported by careful experimental analysis. Unfortunately the very small sizes of microsystems pose experimental problems. Chapter 7 reviews global and local measurement techniques (flowrate, pressure, temperature, velocity) as well as visualization techniques.

Chapters 8 and 9 give a more precise idea of what current fluidic microsystems look like: micropumps, microvalves, micromixers and more complex microsystems are shown. Chapter 9 focuses on microsensors and microactuators that are used for the active control of aerodynamic flows. These microsystems have local multiple and coordinated actions and are able to modify the boundary layer of the flow around the wings of an airplane to reduce drag or increase lift.

Stéphane COLIN

March 2010