Table of Contents Preface List of Contributors xix Chapter 1. Microfluidics: Fundamentals and Engineering Concepts 1

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1 Table of Contents Preface List of Contributors v xix Chapter 1. Microfluidics: Fundamentals and Engineering Concepts 1 1. Introduction 1 2. Essentials of Fluidic Transport Phenomena at Small Scales Microflow Versus Macroflow 2.2. Nanoflow Scaling Analysis Scaling Analysis for Single-Phase Flow Flow Rate Heat Generation Heat Transfer Mass Transfer and Mixing Hydrodynamic Dispersion Scaling Analysis for Two-Phase Flow Capillary Filling Droplet Formation Blocking of Channels by Bubbles Particle Trapping by Dipole Forces Summary of Scaling Laws System/Engineering Concepts and Design Approaches for Microfluidics Engineering Concepts for Microfluidic Systems Mixing Separation Sensing and Detection Pumping Valving Manipulation of Bubbles and Slugs Integration and Materials Design Methods Reduced Order Models for Single-Phase Flow Multiphase and Particulate Flows Optimization and System Design 48 References 49

2 . x Table of Contents Chapter 2 Electrohydrodynamic and Magnetohydrodynamic Micropumps Introduction Basic Features of Conduction in Liquids Mechanical Aspects of Micropumps Electric Forces in the Bulk: Injection, Conduction, and Induction EHD Pumps Injection Pump Pump Principle Characteristics Conduction Pump Pump Principle Characteristics Induction Pump Pump Principle Characteristics Electric Forces in the Diffuse Layer: Electroosmotic and AC/IC Electroosmotic Pumps Electroosmotic Pump Pump Principle Characteristics AC/IC Electroosmotic Pump Pump Principle Characteristics Magnetic Forces: DC and AC MHD Pumps DC MHD Micropump Pumping Principle Characteristics AC MHD Micropump Pump Principle Characteristics Comparisons and Conclusions 107 References 111 Chapter 3. Mixing in Microscale Introduction Mass Transport in Microscale Transport Effects Diffusive Transport Advective Transport Taylor Aris Dispersion Chaotic Advection Dimensionless Numbers and Scaling Laws 121

3 Table of Contents xi 3. Micromixers Based on Molecular Diffusion Parallel Lamination Mixers Based on Pure Molecular Diffusion Mixers Based on Inertial Instabilities Sequential Lamination Sequential Segmentation Segmentation Based on Injection Focusing of Mixing Streams Micromixers Based on Chaotic Advection Chaotic Advection in a Continuous Flow Chaotic Advection at High Reynolds Numbers Chaotic Advection at Intermediate Reynolds Numbers Chaotic Advection at Low Reynolds Numbers Chaotic Advection in Multiphase Flow 5. Active Micromixers Pressure-Driven Disturbance Electrohydrodynamic Disturbance Dielectrophoretic Disturbance Electrokinetic Disturbance Magnetohydrodynamic Disturbance Acoustic Disturbance Thermal Disturbance 149 References 149 Chapter 4. Control of Liquids by Surface Energies Introduction Capillary Model Equilibrium Conditions Contact Line Pinning Computation of Droplet Shapes Plane Substrates with Wettability Patterns Experimental Circular Surface Domains Array of Hydrophilic Discs Array of Hydrophobic Discs Striped Surface Domains Perfectly Wettable Stripe Partially Wettable Stripe Hydrophilic Rings Liquid Wetting Several Stripes

4 xii Table of Contents 4. Wetting of Topographically Patterned Substrates Substrate Preparation Basic Topographies: Infinite Wedge and Step Infinite Wedge Tip Shape Topographic Step Triangular Grooves Rectangular Grooves Switching Equilibrium Morphologies Summary and Outlook 196 References 197 Chapter 5. Electrowetting: Thermodynamic Foundation and Application to Microdevices Introduction Theoretical Background Surface Tension Surface Thermodynamics General Concept of Work Surface Tension in Thermodynamic Consideration Liquid Liquid and Liquid Solid Interfaces: Young s Equation Pressure Difference at the Curvilinear Surface Example: Application of the Laplace-Young Equation Control of Surface Tension Example 1: Chemical Potential Surface Tension System Example 2: Temperature Surface Tension System Example 3: Electric Potential Surface Tension System Electrowetting and Its Recent Variations Electric Double Layer Electrocapillarity: Lippmann s Experiment Electrowetting: On Solid Electrode Electrowetting: On Dielectric Microfluidic Device Using Electrowetting Pumping by Electrowetting on Liquid Electrode: CEW Pumping by Electrowetting on Solid Electrode Pumping by Electrowetting on Dielectric-Coated Solid Electrode (EWOD) Reconfigurable Digital (or Droplet) Microfluidics 234

5 Table of Contents xiii 5. Summary 236 References 236 Chapter 6. Magnetic Beads in Microfluidic Systems Towards New Analytical Applications Introduction Types of Magnetic Beads Forces on Magnetic Beads Magnetic Bead Separation Magnetic Bead Transport Magnetic Beads as Labels for Detection Separation and Mixing Using Magnetic Supraparticle Structures Magnetic Beads as Substrates for Bio-assays Magnetic Beads in Droplets Conclusion 265 References 266 Chapter 7. Manipulation of Microobjects by Optical Tweezers Introduction Single-Particle Manipulation with a Focused Laser Beam Trapping of a Micro/nano Particle with a Focused Laser Beam Trapping of a Metallic Particle Rotation of a Birefringent Microparticle Manipulation of a Micromachined Object Multiparticle Manipulation Techniques Single Beam Based Manipulation Time-Divided Laser Scanning for the Manipulation of Multiple Microparticles Continuous Transportation of Multiple Particles Bessel Beam for the Manipulation of Multiple Particles Holographic Optical Tweezers Evanescent Waves for the Propulsion of Microparticles Optically Driven Microfluidic Components Particle Sorter Using an Optical Lattice Optically Driven Micropump and Microvalve with Colloidal Structures Optically Driven Micropump Produced by Two-Photon Microstereolithography Optically Controlled Micromanipulators Produced by Two-Photon Microstereolithography 303

6 xiv Table of Contents 5. Bio-manipulation Based on Optical Tweezers Cell Stretcher Using Optical Radiation Pressure Manipulation of Biomolecules with Optically Trapped Micro/nano Particles Optically Controlled Microtools for Biological Samples Conclusions and Outlook 309 References 309 Chapter 8. Dielectrophoretic Microfluidics Introduction Quantification of Dielectrophoretic Micro-Fluidics Electric Force Acting on an Individual Particle Field Driven Phase Transitions Electro-Hydrodynamic Models Single-Particle Model Model for Collective Phenomena Microfluidic Applications of Dielectrophoresis Primary Flows Non-uniform Electric Field Generators Modes of Operation Depletion and Enhancement Architectural Considerations Fouling Throughput Concentration Factor Heating Examples of Architectures Post-Based Devices Facet-Based Devices Corduroy Devices Conclusion References Chapter 9. Ultrasonic Particle Manipulation Introduction Theory Radiation Forces Radiation Forces on Small Compressible and Incompressible Spheres Some Practical Considerations Lateral Forces and Secondary Radiation Forces 363

7 Table of Contents xv 2.2. Acoustic Streaming Modelling of Standing Waves for Ultrasonic Force Fields Field Modelling Transduction Techniques Direct Excitation of Bulk Acoustic Waves Bulk PZT Thick-Film PZT Magnetostrictive Excitation Excitation via Leaky Surface Waves and Plate Waves Sol Gel Alternative Materials Applications of Ultrasonic Particle Manipulation Cell Viability Filtration and Concentration Enhanced Sedimentation Flow-Through Filtration Ultrasound Within a Porous Mesh Particle Trapping Trapping to Enhance Particle Particle Interaction Trapping to Enhance Particle Fluid Interaction Sensor Enhancement Particle Washing Exchange of Containing Medium Particle Fractionation The Future of Ultrasonic Particle Manipulation 383 References 383 Chapter 10. Electrophoresis in Microfluidic Systems Introduction Free Solution Electrophoresis Gel Electrophoresis Isoelectric Focusing (IEF) Micellar Electrokinetic Chromatography (MEKC) Electrophoresis in Microfabricated Systems Injection and Separation Sieving Gels Detection Device Construction Applications of Microchip Electrophoresis Advanced Electrophoresis Methods Integrated Systems Summary and Outlook 414 References 415

8 xvi Table of Contents Chapter 11. Chromatography in Microstructures Introduction Background Short Overview of Some Variants of Chromatography Gas Chromatography (GC) Pressure-Driven Liquid Chromatography (LC) Electrochromatography (EC) Miscellaneous Some Theoretical Considerations Examples of Chromatography on Microchips Gas Chromatography (GC) Pressure-Driven Liquid Chromatography (LC) Capillary Electrochromatography (CEC) Other Chromatographic Methods on Microchips Conclusions 465 References 466 Chapter 12. Microscale Field-Flow Fractionation: Theory and Practice Introduction Background and Theory FFF Operating Modes and SPLITT Fractionation FFF Retention Theory Plate Height Nonequilibrium Plate Height Instrumental Plate Height Resolution Miniaturization Effects in FFF Instrumental Plate Height Gradient-Based Systems Plate Height Scaling Resolution Scaling Nongradient-Based Systems Plate Height Scaling Microscale Electrical FFF Theory Fabrication and Packaging System Characteristics Retention Separations Effective Field Scaling Microscale Cyclical Electrical FFF Theory 495

9 Table of Contents xvii Effective Field Model Steric Effects in CyFFF Particle Diffusion Effects Experimental Results Comparison of Theory with Experimental Data Separations Effects of Carrier ph and Ionic Strength Microscale Dielectrophoretic FFF Theory Experimental Results Microscale Thermal FFF Miniaturized Flow FFF Microscale Acoustic FFF Other Microscale FFF Efforts Microscale Split-Flow Thin Fractionation Microscale Hydrodynamic Chromatography Nanoscale FFF Conclusion 515 References 516 Chapter 13. Nucleic Acid Amplification in Microsystems General Elements of Amplification Micro Macro Comparison Typical Length Scales Volumetric Effects Surface Effects Linear, Timescale and Other Effects Microfluidic Realization Methods Substrates Types of Setup Amplification in Wells Amplification by Continuous Flow-Through Devices Special Realization Methods Surface Treatments Detection of Amplified DNA Integrated Micro-PCR Systems Alternative Protocols to PCR Conclusion 554 References 555

10 xviii Table of Contents Chapter 14. Cytometry on Microfluidic Chips Introduction Design of Microfluidic Flow Cytometers Transport and Focusing of Cell Suspensions The Sorting Unit: Active Microfluidic Switches Integration of Several Functionalities on Microchips Detection Concepts for Ultrasensitive Cytometry Single Molecule Fluorescence Spectroscopy in Microfluidic Channels Determination of Flow Velocity by Fluorescence Correlation Spectroscopy (FCS) Integration of Optical Components into Microfluidic Chips Other Detection Techniques Perspectives for Biotechnology Sorting of Single Molecules Cell-Free Protein Expression in Microfluidic Chips Perspectives of Generating Membrane Vesicles in Microstructures Conclusion 598 References 598 Index 607

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