Preface xi
1 Introduction to Capillarity and Wetting Phenomena 1
1.1 Surface Tension and Surface Free Energy 2
1.2 Young¢"Laplace Equation: The Basic Law of Capillarity 7
1.3 Young¢"Dupr© Equation: The Basic Law of Wetting 13
1.4 Wetting in the Presence of Gravity 19
1.5 Variational Derivation of the Young¢"Laplace and the Young¢"Dupr© Equation 26
1.6 Wetting at the Nanoscale 29
1.7 Wetting of Heterogeneous Surfaces 35
2 Electrostatics 61
2.1 Fundamental Laws of Electrostatics 61
2.2 Materials in Electric Fields 66
2.3 Electrostatic Energy 76
2.4 Electrostatic Stresses and Forces 82
2.5 Two Generic Case Studies 87
3 Adsorption at Interfaces 95
3.1 Adsorption Equilibrium 96
3.2 Adsorption Kinetics 101
3.3 Surface-Active Solutes: From Surfactants to Polymers, Proteins, and Particles 105
4 From Electric Double Layer Theory to Lippmann's Electrocapillary Equation 113
4.1 Electrocapillarity: the Historic Origins 113
4.2 The Electric Double Layer at Solid¢"Electrolyte Interfaces 115
4.3 Shortcomings of Poisson¢"Boltzmann Theory and the Gouy¢"Chapman Model 124
4.4 Teflon¢"Water Interfaces: a Case Study 125
5 Principles of Modern Electrowetting 133
5.1 The Standard Model of Electrowetting (on Dielectric) 133
5.2 Interpretation of the Standard Model of EW 145
5.3 DC Versus AC Electrowetting 151
6 Elements of Fluid Dynamics 159
6.1 Navier¢"Stokes Equations 159
6.2 Lubrication Flows 170
6.3 Contact Line Dynamics 179
6.4 Surface Waves and Drop Oscillations 185
7 Electrowetting Materials and Fabrication 197
7.1 Practical Requirements 197
7.2 Electrowetting Deviation: Caused by Non-obvious Materials Behavior 198
7.3 Electrowetting Saturation 207
7.4 The Invariant Onset of Deviation or Saturation and Lack of a Universal Theory for This Invariance 208
7.5 Choosing Materials: Large Young's Angle and Low Wetting Hysteresis 210
7.6 Choosing Materials: the Electrowetting Dielectric (Capacitor) 215
7.7 Choosing Materials: Insulating and Conducting Fluids 221
7.8 Summary of General Best Practices 224
7.9 Mitigating Surface Fouling in Biological Applications 224
7.10 Additional Issues for Complex or Integrated Devices 226
8 Fundamentals of Applied Electrowetting 235
8.1 Introduction and Scope 235
8.2 Droplet Transport 235
8.3 Droplet Transport for Splitting, Dosing, Merging, and Mixing 240
8.4 Stationary Droplet Oscillation, Jumping, and Mixing 244
8.5 Gating, Valving, and Pumping 247
8.6 Generating Droplets and Channels 249
8.7 Shape Change in a Channel 251
8.8 Control of Meniscus Curvature 252
8.9 Control of Meniscus Surface Area/Coverage 253
8.10 Control of Film Breakup and Oil Entrapment 255
8.11 1D, 2D, and 3D Control of Rigid Objects 257
8.12 Reverse Electrowetting and Energy Harvesting 258
9 Related and Emerging Topics 265
9.1 Introduction and Scope 265
9.2 Dielectrophoresis and Dielectrowetting 265
9.3 Innovations in Liquid Metal Electrowetting and Electrocapillarity 269
9.4 Nonequilibrium Electrical Control Without Contact Angle Modulation 271
Appendix Historical Perspective of Modern Electrowetting: Individual Testimonials 277
Introduction and Scope 277
"CJ" Kim 277
Authors Note from Heikenfeld 278
Johan Feenstra 278
Tom Jones 279
Frieder Mugele 280
Richard Fair 281
Author's Note from Heikenfeld 282
Bruno Berge 282
Glen McHale 285
Stein Kuiper 286
Jason Heikenfeld 288
Kwan Hyung Kang: An Appreciation by T. B. Jones 289
Author's Note from Mugele 290
References 290
Index 293
