Liquid Friction, Wettability and Surfaces Slippery to Liquids

Water is all around us. On a wet day we need coats to keep us dry, windscreen wipers to see and reservoirs to collect water to drink. There are few things more essential for life. However, when objects become small, the force of gravity gives way to the force of surface tension. In this world, Nature really does know how to manipulate water. Insects walk on water. Diving beetles breathe without the need for gills. Desert beetles drink from fog. Lotus leaves stay dry and stay clean. Galling aphids roll away their sticky liquid waste. And the Nepenthes Pitcher Plant eats ants for breakfast, lunch and dinner. In all these cases, the key is the natural adaptation of surfaces to control how they interact with water. In this talk, I will give an overview of how Nature inspires diverse strategies to manipulate droplets and liquids to engineer super-water repellent, superslippery, low friction and drag reducing surfaces. I will show how this allows solid-liquid interfacial interactions to be understood, the wetting of surfaces to be manipulated and the liquid-on-solid friction to be reduced.

Acknowledgements: Many collaborators contributed to this work, which was part-funded by the UK Engineering and Physical Sciences Research Council (EPSRC).