Liquid Marbles
![Liquid marble](https://naturesraincoats.com/wp/wp-content/uploads/2019/03/Liquid-Marble-ID2.jpg)
‘Hydrophobic’ is usually taken to mean ‘water-fearing’, but hydrophobic grains stick to the surface of water. If the grains forming a hydrophobic surface are loose, rather than fixed, a droplet of water rolling across the surface will become encapsulated by the grains. This is known as a liquid marble can be formed in which a ‘ball’ of water is encased in a granular coating. A droplet of water rolling across the surface becomes encapsulated by the grains., as illustrated schematically in the image below.
![](https://naturesraincoats.com/wp/wp-content/uploads/2019/03/Marble-Schematic.jpg)
Liquid marbles are completely mobile and rolls freely on solid (and water) surfaces, as seen below.
![A liquid marble rolling across a surface](https://naturesraincoats.com/wp/wp-content/uploads/2019/05/img8.jpg)
![slowly-rolling liquid marble](https://naturesraincoats.com/wp/wp-content/uploads/2019/06/Slow-Marble-480ul-36-deg.2019-06-19-14_26_11.gif)
![Fast-rolling liquid marble](https://naturesraincoats.com/wp/wp-content/uploads/2019/06/Fast-Marble-210ul-34-deg.2019-06-19-14_21_59.gif)
Professor Quéré and co-workers have shown that small liquid marbles roll down hill faster than larger ones, as shown below. This is the opposite of what would be expected for solid marbles.
![A race between liquid marbles](https://naturesraincoats.com/wp/wp-content/uploads/2019/06/Marble-Race-4062.2019-06-19-14_25_12.gif)
Liquid marbles occur naturally and are used by galling aphids as a waste disposal system for the honeydew they secrete – read more about gall aphids here.
Publications
- Liquid Marbles P. Aussillous and D. Quéré, Nature 411 (2001), 924-927
- Electrowetting of non-wetting liquids and liquid marbles G. McHale, D.L. Herbertson, S.J. Elliot, N.J. Shirtcliffe and M.I. Newton, Langmuir 23 (2007) 918-924
- Liquid Marbles: Principles and applications G. McHale and M.I. Newton, Soft Matter 7 (2011) 5473-5481
- Liquid marbles: topical context within soft matter and recent progress G. McHale and M.I. Newton, Soft Matter 11 (2015) 2530–2546