 | Nguyen N.-T. Micromixers: fundamentals, design, and fabrication. - Norwich: William Andrew, 2008. - xiv, 311 p.: ill. - (Micro & nano technologies). - ISBN 978-0-8155-1543-2
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Series Editor's Preface ........................................ ix
Preface ........................................................ xi
Acknowledgments ................................................ xi
Symbols ...................................................... xiii
1. Introduction ................................................. 1
1.1. Micromixers and Mixing in Microscale ................... 1
1.2. Micromixers as Microreactors ............................ 4
1.3. Organization of the Book ................................ 6
References ................................................... 7
2. Fundamentals of Mass Transport in the Micro Scale ............ 9
2.1. Transport Phenomena ..................................... 9
2.1.1. Molecular Level .................................. 9
2.1.2. Continuum Level ................................. 13
2.2. Molecular Diffusion .................................... 21
2.2.1. Random Walk and Brownian Motion ................. 21
2.2.2. Stokes-Einstein Model of Diffusion .............. 23
2.2.3. Diffusion Coefficient ........................... 24
2.3. Taylor Dispersion ...................................... 28
2.3.1. Two-Dimensional Analysis ........................ 29
2.3.2. Three-Dimensional Analysis ...................... 35
2.4. Chaotic Advection ...................................... 37
2.4.1. Basic Terminologies ............................. 37
2.4.2. Examples of Chaotic Advection ................... 41
2.5. Viscoelastic Effects ................................... 54
2.6. Electrokinetic Effects ................................. 56
2.6.1. Electroosmosis .................................. 56
2.6.2. Electrophoresis ................................. 67
2.6.3. Dielectrophoresis ............................... 69
2.7. Magnetic and Electromagnetic Effects ................... 69
2.7.1. Magnetic Effects ................................ 69
2.8. Scaling Law and Fluid Flow in Micro Scale .............. 72
References .................................................. 75
3. Fabrication Technologies .................................... 79
3.1. Silicon-Based Microtechnologies ....................... 79
3.1.1. Basic Technologies .............................. 80
3.1.2. Single-Crystalline Silicon ...................... 84
3.1.3. Polysilicon ..................................... 95
3.1.4. Other Materials ................................. 97
3.2. Polymeric Microtechnologies ............................ 99
3.2.1. Thick-Film Polymeric Materials ................. 100
3.2.2. Polymeric Bulk Micromachining .................. 105
3.2.3. Polymeric Surface Micromachining ............... 117
3.3. Metallic Microtechnologies ............................ 121
3.3.1. Metals as Substrate Materials .................. 121
3.3.2. LIGA ........................................... 122
3.3.3. Micro Electro Discharge Machining .............. 122
3.3.4. Focused Ion Beam Micromachining ................ 123
3.3.5. Powder Blasting ................................ 123
3.3.6. Ultrasonic Micromachining ...................... 124
3.4. Packaging ............................................. 124
3.4.1. Anodic Bonding ................................. 124
3.4.2. Direct Bonding ................................. 125
3.4.3. Adhesive Bonding ............................... 126
3.4.4. Eutectic Bonding ............................... 127
3.5. Conclusions ........................................... 127
References ................................................. 127
4. Micromixers Based on Molecular Diffusion ................... 135
4.1. Parallel Lamination ................................... 135
4.1.1. Mixers Based on Pure Molecular Diffusion ....... 135
4.1.2. Mixers Based on Inertial and Viscoelastic
Instabilities .................................. 141
4.2. Sequential Lamination ................................. 144
4.3. Sequential Segmentation ............................... 146
4.4. Segmentation Based on Injection ....................... 147
4.5. Focusing of Mixing Streams ............................ 150
4.5.1. Streams with the Same Viscosity ................ 150
4.5.2. Streams with Different Viscosities ............. 153
4.5.3. Combination of Hydrodynamic Focusing and
Sequential Segmentation ........................ 155
References ................................................. 160
5. Micromixers Based on Chaotic Advection ..................... 163
5.1. Chaotic Advection at High Reynolds Numbers ............ 163
5.1.1. T-Mixer at High Reynolds Numbers ............... 163
5.1.2. Passive Mixers with Obstacles in the Mixing
Channel ........................................ 166
5.1.3. Dean Flow with Repeated Turns in Mixing
Channel ........................................ 168
5.2. Chaotic Advection at Intermediate Reynolds Numbers .... 170
5.2.1. Chaotic Advection with 90° Turns ............... 170
5.2.2. Chaotic Advection with Other Channel Designs ... 172
5.3. Chaotic Advection at Low Reynolds Numbers ............. 176
5.3.1. Chaotic Advection with Dean Vortices And
Complex 3-D Channels ........................... 176
5.3.2. Chaotic Advection with Flow-Guiding
Structures on Channel Walls .................... 180
5.4. Chaotic Advection in Multiphase Flow .................. 186
5.4.1. Multiphase Systems in Micro Scale .............. 186
5.4.2. Mixing in Microdroplets ........................ 198
References ................................................. 203
6. Active Micromixers ......................................... 207
6.1. Flow Instability in Microchannels ..................... 207
6.2. Pressure-Driven Disturbance ........................... 207
6.2.1. Actuation Concepts for Pressure Generation ..... 207
6.2.2. Hydrodynamic Instability ....................... 215
6.2.3. Pulsed Source-Sink Chaotic Advection ........... 217
6.2.4. Design Examples ................................ 221
6.3. Electrohydrodynamic Disturbance ....................... 227
6.4. Dielectrophoretic Disturbance ......................... 231
6.5. Electrokinetic Disturbance ............................ 233
6.5.1. Instability Caused by Conductivity Gradient .... 233
6.5.2. Instability Caused by Variation of Electric
Field .......................................... 237
6.5.3. Instability Caused by Variation of Zeta
Potentials ..................................... 238
6.5.4. Design Examples ................................ 240
6.6. Magnetohydrodynamic Disturbance ....................... 244
6.6.1. Straight Channel Configuration [43] ............ 244
6.6.2. Curved-Channel Configuration [44] .............. 246
6.6.3. Design Examples ................................ 250
6.7. Acoustic Disturbance .................................. 251
6.7.1. Vibration of a Rectangular Membrane [49] ....... 252
6.7.2. Vibration of a Circular Membrane [49] .......... 255
6.7.3. Design Examples ................................ 258
6.8. Thermal Disturbance ................................... 261
References ................................................. 262
7. Characterization Techniques ................................ 267
7.1.Imaging Techniques ..................................... 267
7.1.1. Two-Dimensional Optical Microscopy ............. 267
7.1.2. Two-Dimensional Fluorescence Microscopy ........ 271
7.1.3. Confocal Laser Scanning Microscopy ............. 273
7.1.4. Acquisition and Processing of Digital Images ... 275
7.2. Measurement Using Optical Microscopy .................. 280
7.2.1. Measurement of velocity field .................. 280
7.2.2. Measurement of Concentration Field ............. 283
7.3. Quantification Methods for Micromixers ................ 285
7.3.1. Direct Statistical Methods ..................... 285
7.3.2. Indirect Methods ............................... 288
References ................................................. 291
8. Application of Micromixers ................................. 293
8.1. Chemical Industry ..................................... 293
8.1.1. Micromixers as Microreactors ................... 293
8.1.2. Homogeneous Reactions .......................... 293
8.1.3. Heterogeneous Reactions ........................ 294
8.1.4. Enhancement of Chemical Selectivity ............ 295
8.2. Applications in Chemical and Biochemical Analysis ..... 296
8.2.1. Concentration Measurement ...................... 296
8.2.2. Improving Chemical and Biochemical Analysis .... 297
8.2.3. Purification and Pre-Concentration ............. 301
8.3. Outlook ............................................... 302
References ................................................. 304
Index ......................................................... 306
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