The Physics of Microdroplets

Preface xviii
Acknowledgements xxi
Introduction 1
1. Fundamentals of Capillarity 5
1.1 Abstract 5
1.2 Interfaces and Surface Tension 5
1.3 Laplace's Law and Applications 12
1.4 Measuring the Surface Tension of Liquids 49
1.5 Minimization of the Surface Energy 61
1.6 References 62
2. Minimal Energy and Stability Rubrics 67
2.1 Abstract 67
2.2 Spherical Shapes as Energy Minimizers 68
2.3 Symmetrization and the Rouloids 73
2.4 Increasing Pressure and Stability 77
2.5 The Double-Bubble Instability 81
2.6 Conclusion 84
2.7 References 84
3. Droplets: Shape, Surface and Volume 85
3.1 Abstract 85
3.2 The Shape of Micro-drops 86
3.3 Electric Bonds Number 87
3.4 Shape, Surface Area and Volume of Sessile Droplets 87
3.5 Conclusion 105
3.6 References 105
4. Sessile Droplets 107
4.1 Abstract 107
4.2 Droplet Self-motion Under the Effect of a Contrast orGradient of Wettability 107
4.3 Contact Angle Hysteresis 114
4.4 Pinning and Canthotaris 117
4.5 Sessile Droplet on a Non-ideally Planar Surface 124
4.6 Droplet on Textured or Patterned Substrates 125
4.7 References 142
5. Droplets Between Two Non-parallel Planes: from TaperedPlanes to Wedges 145
5.1 Abstract 145
5.2 Droplet Self-motion Between Two Non-parallel Planes 145
5.3 Droplet in a Corner 154
5.4 Conclusion 160
5.5 References 161
6. Microdrops in Microchannels and Microchambers 163
6.1 Abstract 163
6.2 Droplets in Micro-wells 163
6.3 Droplets in Microchannels 168
6.4 Conclusion 180
6.5 References 181
7. Capillary Effects: Capillary Rise, Capillary Pumping, andCapillary Valve 185
7.1 Abstract 185
7.2 Capillary Rise 185
7.3 Capillary Pumping 198
7.4 Capillary Valves 205
7.5 Conclusions 209
7.6 References 210
8. Open Microfluidics 213
8.1 Abstract 213
8.2 Droplet Pierced by a Wire 214
8.3 Liquid Spreading Between Solid Structures -Spontaneous Capillary Flow 218
8.4 Liquid Wetting Fibers 241
8.5 Conclusions 250
8.6 References 250
8.7 Appendix: Calculation of the Laplace Pressure for a Dropleton a Horizontal Cylindrical Wire 251
9. Droplets, particles and Interfaces 253
9.1 Abstract 253
9.2 Neumann's Construction for liquid Droplets 253
9.3 The Difference Between Liquid Droplets and Rigid Spheres atan Interface 254
9.4 Liquid Droplet Deposited at a Liquid Surface 256
9.5 Immiscible Droplets in Contact and Engulfment 261
9.6 Non-deformable (Rigid) Sphere at an Interface 265
9.7 Droplet Evaporation and Capillary Assembly 278
9.8 Conclusion 291
9.9 References 292
10. Digital Microfluidics 295
10.1 Introduction 295
10.2 Electrowetting and EWOD 295
10.3 Droplet Manipulation with EWOD 306
10.4 Examples of EWOD in Biotechnology - Cell Manipulation335
10.5 Examples of Electrowetting for Optics-Tunable Lenses andElectro fluidic Display 337
10.6 Conclusion 338
10.7 References 339
11. Capillary Self-assembly for 3D Microelectronics343
11.1 Abstract 343
11.2 Ideal Case: Total Pinning on the Chip and Pad Edges 344
11.3 Real Case: Spreading and Wetting 355
11.4 The Importance of Pinning and Confinement 358
11.5 Conclusion 359
11.6 Appendix A: Shift Energy and Restoring Force 360
11.7 Appendix B: Twist Energy and Restoring Torque 362
11.8 Appendix C: Lift Energy and Restoring Force 364
11.9 References 365
12. Epilogue 369
Index 369