Physics of Wetting

Motivated by a plethora of phenomena from nature, this textbook introduces into the physics of wetting of surfaces. After a brief discussion of the foundations of surface tension, its implementation for floating objects, capillary waves, bouncing droplets, walking of water striders, etc. is discussed. Furthermore, Marangoni flows, surface tension inspired instabilities, condensation and evaporation of droplets, liquid marbles, superhydrophobicity and superoleophobicity (lotus effect) are introduced. All relevant concepts are illustrated by the numerous qualitative and quantitative exercises.

Contents

What is surface tension?

Wetting of surfaces: the contact angle

Surface tension-assisted floating of heavy and light objects and walking of water striders

Capillary interactions between particles. Particles placed on liquid surfaces. Elasticity of liquid surfaces, covered by colloidal particles

Capillary waves

Oscillation of droplets

Marangoni flow and surface instabilities

Evaporation of droplets. The Kelvin and the coffee-stain effects

Condensation, growth and coalescence of droplets and the breath-figure self-assembly

Dynamics of wetting: bouncing, spreading and rolling of droplets (water hammer effect - water entry and drag-out problems)Superhydrophobicity and superoleophobicity: the Wenzel and Cassie wetting regimes

The Leidenfrost effect. Liquid marbles: self-propulsion

Physics, geometry, life and death of soap films and bubbles