Fundamentals and Applications of Microfluidics Second Edition Nam-Trung Nguyen Steven T. Wereley ARTECH HOUSE BOSTON LONDON artechhouse.com
Contents Preface Acknowledgments xi xiii Chapter 1 Introduction 1 1.1 What Is Microfluidics? 1 1.1.1 Relationships Among MEMS, Nanotechnology, and Microfluidics 1 1.1.2 Commercial Aspects 4 1.1.3 Scientific Aspects 5 1.2 Milestones of Microfluidics 6 1.2.1 Device Development 6 1.2.2 Technology Development. 8 1.3 Organization of the Book - 8 9 Chapter 2 Fluid Mechanics Theory 11 2.1 Introduction 11 2.1.1 Intermolecular Forces 12 2.1.2 The Three States of Matter 14 2.1.3 Continuum Assumption 15 2.2 Continuum Fluid Mechanics at Small Scales 18 2.2.1 Gas Flows 19 2.2.2 Liquid Flows 23 2.2.3 Boundary Conditions 25 2.2.4 Parallel Flows 30 2.2.5 Low Reynolds Number Flows 33 2.2.6 Entrance Effects, 36 2.2.7 Surface Tension ' 37 2.3 Molecular Approaches 39 2.3.1 MD 40 2.3.2 DSMC Technique 42 2.4 Electrokinetics 44 2.4.1 Electro-osmosis 44 2.4.2 Electrophoresis 47 2.4.3 Dielectrophoresis 49 2.5 Conclusion 51
VI Fundamentals and Applications of Microfluidics 52 53 Chapter 3 Fabrication Techniques for Microfluidics 55 3.1 Basic Microtechniques 55 3.1.1 Photolithography 55 3.1.2 Additive Techniques 57 3.1.3 Subtractive Techniques 59 3.1.4 Pattern Transfer Techniques 61 3.2 Functional Materials 62 3.2.1 Materials Related to Silicon Technology 62 3.2.2 Polymers 67 3.3 Silicon-Based Micromachining Techniques 69 3.3.1 Silicon Bulk Micromachining 69 3.3.2 Silicon Surface Micromachining 76 3.4 Polymer-Based Micromachining Techniques 81 3.4.1 Thick Resist Lithography 82 3.4.2 Polymeric Bulk Micromachining 86 3.4.3 Polymeric Surface Micromachining 87 3.4.4 Microstereo Lithography 91 3.4.5 Micromolding 95 3.5 Other Micromachining Techniques 100 3.5.1 Subtractive Techniques 101 3.5.2 Additive Techniques 103 3.6 Assembly and Packaging of Microfluidic Devices 104 3.6.1 Wafer Level Assembly and Packaging 104 3.6.2 Device Level Packaging 106 3.7 Biocompatibility. 108 3.7.1 Material Response 108 3.7.2 Tissue and Cellular Response 109 3.7.3 Biocompatibility Tests 109 109 110 Chapter 4 Experimental Flow Characterization 117 4.1 Introduction 117 4.1.1 Pointwise Methods 117 4.1.2 Full-Field Methods 118 4.2 Overview of upiv 122 4.2.1 Fundamental Physics Considerations of upiv 122 4.2.2 Special Processing Methods for upiv Recordings; 138 4.2.3 Advanced Processing Methods Suitable for Both Micro/Macro-PIV Recordings 141 4.3 upiv Examples 144 4.3.1 Flow in a MicroChannel 144 4.3.2 Flow in a Micronozzle 146 4.3.3 Flow Around a Blood Cell 149 4.3.4 Flow in Microfluidic Biochip 151 4.3.5 Conclusions 153 4.4 Extensions of the upiv Technique 153
Contents vu 4.4.1 4.4.2 4.4.3 4.4.4 Microfluidic Nanoscope Microparticle Image Thermometry Infrared upiv Particle Tracking Velocimetry 153 158 167 169 172 172 Chapter 5 Chapter 6 Chapter 7 Microfluidics for External Flow Control 5.1 Velocity and Turbulence Measurement 5.1.1 Velocity Sensors 5.1.2 Shear Stress Sensors 5.2 Turbulence Control 5.2.1 Microflaps 5.2.2 Microballoon 5.2.3 Microsynthetic Jet 5.3 Microair Vehicles 5.3.1 Fixed- Wing MAV 5.3.2 Flapping-Wing MAV 5.3.3 Microrotorcraft 5.3.4 Microrockets Microfluidics for Internal Flow Control: Microvalves 6.1 Design Considerations 6.1.1 Actuators 6.1.2 Valve Spring 6.1.3 Valve Seat 6.1.4 Pressure Compensation Design 6.2 Design Examples 6.2.1 Pneumatic Valves ^ 6.2.2 6.2.3 6.2.4 6.2.5 6.2.6 6.2.7 6.2.8 6.3 Summary Thermopneumatic Valves Thermomechanical Valves Piezoelectric Valves Electrostatic Valves Electromagnetic Valves Electrochemical and Chemical Valves Capillary-Force Valves Microfluidics for Internal Flow Control: Micropumps 7.1 Design Considerations 7.1.1 Mechanical Pumps 7.1.2 Nonmechanical Pumps 7.2 Design Examples 7.2.1 Mechanical Pumps 7.2.2 Nonmechanical Pumps 7.3 Summary 177 177 177 181 189 190 191 192 193 194 195 197 198 207 208 211 213 213 234 237 238 239 239 240 242 244 245 247 248 250 250 251 251 255 256 256 269 288 288 298 303
viii Fundamentals and Applications of Microfluidics Chapter 8 Chapter 9 Microfluidics for Internal Flow Control: Microflow Sensors 8.1 Design Considerations 8.1.1 Design Parameters 8.1.2 Nonthermal Flow Sensors 8.1.3 Thermal Flow Sensors 8.2 Design Examples 8.2.1 Nonthermal Flow Sensors 8.2.2 Thermal Flow Sensors 8.3 Summary Microfluidics for Life Sciences and Chemistry: Microneedles 9.1 Design Considerations 9.1.1 Mechanical Design 9.1.2 Delivery Modes 9.2 Design Examples 9.2.1 Solid Microneedles 9.2.2 Hollow Microneedles 9.3 Summary 303 304 311 311 311 312 317 324 324 327 335 336 336 339 341 341 346 348 348 349 352 353 353 Chapter 10 Microfluidics for Life Sciences and Chemistry: Micromixers 10.1 Design Considerations 10.1.1 Parallel Lamination 10.1.2 Sequential Lamination 10.1.3 Sequential Segmentation 10.1.4 Segmentation Based on Injection 10.1.5 Focusing of Mixing Streams 10.1.6 Formation of Droplets and Chaotic Advection 10.2 Design Examples 10.2.1 Passive Micromixers 10.2.2 Active Micromixers 10.3 Summary Chapter 11 Microfluidics for Life Sciences and Chemistry: Microdispensers 11.1 Design Considerations 11.1.1 Droplet Dispensers 11.1.2 In-Channel Dispensers 11.2 Design Examples 11.2.1 Droplet Dispensers 11.2.2 In-Channel Dispensers 11.3 Summary 357 359 360 363 364 366 369 372 374 374 383 386 388 389 395 395 395 404 408 408 412 414 415
Contents 416 Chapter 12 Microfluidics for Life Sciences and Chemistry: Microfilters and Microseparators 419 12.1 Microfilters, 419 12.1.1 Design Considerations 421 12.1.2 Design Examples 423 12.2 Microseparator 425 12.2.1 Cell and Particle Sorter 426 12.2.2 Chromatography 431 12.3 Summary 438 439 439 Chapter 13 Microfluidics for Life Sciences and Chemistry: Microreactors 443 13.1 Design Considerations 444 13.1.1 Specification Bases for Microreactors 444 13.1.2 Miniaturization of Chemical Processes 445 13.1.3 Functional Elements of a Microreactor 446 13.2 Design Examples 449 13.2.1 Gas-Phase Reactors 449 13.2.2 Liquid-Phase Reactors 457 13.2.3 Multiphase Reactors 464 13.2.4 Microreactors for Cell Treatment 468 13.2.5 Hybridization Arrays 470 13.3 Summary 472 472 473 Appendix A List of Symbols 479 Appendix B Resources for Microfluidics Research 483 Appendix C Abbreviations of Different Plastics 485 Appendix D Linear Elastic Deflection Models 487 About the Authors 489 Index 491