- Superhydrophobicity: when droplets slide -

Superhydrophobic surfaces repel water and promote drop sliding – key to understanding the Leidenfrost effect. To see in this video from the "Dynamics of fluid interfaces" MOOC by ESPCI Paris - PSL.

🎥 https://www.youtube.com/watch?v=T8AFO2iXsmE&list=PLcbz7zf4dTyk9BqlBPLpgI48i9TiorpEi&index=10

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#Superhydrophobic #SurfaceTension #FluidPhysics #HydrohphobicTextures #LeidenfrostEffect

Ice Discs Surf on Herringbones

Inspired by the roaming rocks of Death Valley, researchers went looking for ways to make ice discs self-propel. Leidenfrost droplets can self-propel on herringbone-etched surfaces, so the team used them here, as well. On hydrophilic herringbones, they found that meltwater from the ice disc would fill the channels and drag the ice along with it.

But on hydrophobic herringbone surfaces, the ice disc instead attached to the crest of the ridges and stayed in place–until enough of the ice melted. Then the disc would detach and slingshot (as shown above) along the herringbones. This self-propulsion, they discovered, came from the asymmetry of the meltwater; because different parts of the puddle had different curvature, it changed the amount of force surface tension exerted on the ice. Thus, when freed, the ice disc tried to re-center itself on the puddle.

The team is especially interested in how effects like this could make ice remove itself from a surface. After all, it requires much less energy to partially melt some ice than it does to completely melt it. (Image and research credit: J. Tapochik et al.; via Ars Technica)

#fluidDynamics #ice #melting #physics #science #selfPropulsion #superhydrophobic

How Insects Fly in the Rain

Getting caught in the rain is annoying for us but has the potential to be deadly for smaller creatures like insects. So how do they survive a deluge? First, they don’t resist a raindrop, and second, they have the kinds of surfaces water likes to roll or bounce off. The key to this second ability is micro- and nanoscale roughness. Surfaces like butterfly wings, water strider feet, and leaf surfaces contain lots of tiny gaps where air gets caught. Water’s cohesion — its attraction to itself — is large enough that water drops won’t squeeze into these tiny spaces. Instead, like the ball it resembles, a water drop slides or bounces away. (Video and image credit: Be Smart)

#biology #butterfly #cohesion #droplets #fluidDynamics #hydrophobic #insects #physics #science #superhydrophobic #surfaceRoughness #surfaceTension

💇 Fabrication of Superhydrophobic Ultra-Fine Brass Wire by Laser Processing

… this sort of thing can cut out PFAS!

https://www.mdpi.com/1996-1944/18/7/1420

#manufacturing #materials #lasers #pfas #technology #superhydrophobic

Even freshwater contains trace salts and minerals that cause scaly buildups as they evaporate. Getting rid of the scale usually requires toxic chemicals and/or lots of scrubbing, neither of which are desirable at the industrial level. At the same time, we’re extremely limited in the amount of freshwater that we have available; only about 1% of Earth’s water is liquid and fresh. If we could use salt water in more industrial processes, that would preserve freshwater for drinking and agriculture. But how do we tackle the scaly buildup?

Enter “salt critters.” Researchers found that when salt water evaporated from microtextured surfaces designed to shed water, salt would eventually build up in the gaps, breaking the hydrophobic effect and allowing scale to build up. In contrast, a nanotextured surface left nowhere for the salt to adhere. On these surfaces, evaporating salt water built jellyfish-like salt critters that rose from the surface and, eventually, broke off and rolled away, leaving the surface pristine. (Image credit: S. McBride; research credit: S. McBride et al.; via Physics Today)

https://fyfluiddynamics.com/2024/10/self-cleaning-with-salt-critters/

#droplets #evaporation #fluidDynamics #physics #science #selfCleaning #superhydrophobic

Artist Lily Clark loves to work in water. One of her recent sculptures, “Dew Point,” uses superhydrophobic ceramic to grow and manipulate water droplets over and over and over. Droplets coalesce in four corners until they grow large enough for gravity to pull them into a circular depression. Given their limited contact with the ceramic, the falling water droplets zip and slide on their way to a return slit in the center of the piece. You can see more of the action in the video below. Personally, I’m reminded of coins falling into a collection box! (Video credit: L. Turczan; artwork by: L. Clark; via Colossal)

https://fyfluiddynamics.com/2024/05/dew-point-deposits-droplets/

#fluidDynamics #fluidsAsArt #physics #science #superhydrophobic

#DYK #superhydrophobic surfaces have the potential to keep things dry, clean & bacteria-free?
🆕 research @aaltouniversity aims to harness this potential for aerospace, defence, automotive, biomedical & textile sectors.
Read more:
👉 https://bit.ly/3kcHo2L
@CORDIS_EU @robin_ras

🐦🔗: https://n.respublicae.eu/ERC_Research/status/1614170481548222464