Watch: Crystal Critters – salt structures that come to life!
1 September 2022
Last update: 31/01/23 12:12
When a drop of salty water is evaporated on a hydrophobic surface, “salt globes” that mirror the shape of the drop grow. Here, we present an unusual phenomenon in which salt globes grown from an evaporating drop on a heated superhydrophobic surface proceed to self-eject from that surface via growth of crystalline tubules. A large temperature gradient concentrates vaporization near the substrate, and escaping vapor at contact points between substrate and liquid leads to growth of crystalline tubules. These tubules grow into “legs,” causing the entire salt globe – and any remaining water – to lift off from the surface. We call the structures composed of salt globes balanced on tubule legs “crystal critters” due to their resemblance to biological forms. Following complete evaporation, the crystal critters have minimal contact with the substrate and can be easily removed; and could find application for anti-fouling surfaces for spray heat exchangers. Gallery of Fluid Motion entry: https://www.youtube.com/watch?v=VV5oc28QP7o
Samantha McBride (MIT) and Henri Girard (MIT) explain how they accidentally discovered a new fluid dynamics phenomena where the evaporation of salt water forms amazing creatures such as a ‘jellyfish’, ‘crab’, ‘elephant’ and ‘droid’. Research by Samantha McBride and Henri Girard at MIT. Interview with University of Oxford Mathematician Dr Tom Crawford.
This video is part of a collaboration with the Journal of Fluid Mechanics and the UK Fluids Network featuring a series of interviews with researchers from the APS DFD 2019 conference.
Produced by Tom Crawford an Early-Career Teaching and Outreach Fellow in Mathematics at St Edmund Hall. With thanks to Samantha McBride Henri Girard APS Physics Océane Baer InCamera
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