They found a reliable way to create antibubbles

[This is a transcript with links to references.]

You’ve all heard of bubbles, but have you heard of anti-bubbles? Me neither, but it’s a thing, as I just learned from this recent paper.

Bubbles are thin, closed membranes of liquid surrounded by gas both inside and out. An anti-bubble is just the opposite, a thin, closed layer of gas with liquid inside and out. They’re known to sometimes exist in liquids, but they usually last just a few milliseconds, so unless you have very sharp eyes, you’ve probably never seen one.

But researchers from the Université de Liège in Belgium have now found a way to reliably create those bubbles and to study them. They did it in a very clever way, by dropping liquid ether into hot oil. The hot liquid makes the drops evaporate on their surface, which creates a layer of vapor. So there’s the antibubble!

They took videos of the antibubbles at very high frame rates and found a few interesting things. First, they had to let the drops fall down from some height because otherwise they’d just sit on the oil surface and evaporate. Then they observed how the antibubbles plunged into the oil and came back up. They found that the bubbles were more stable if the oil was hotter, because the heat caused an extra expansion that helped the bubble maintain its structure. They also found that pre-warming the droplets to room temperature prior to dropping them into the oil increased their lifetime, because otherwise they expanded too quickly.

Their creation of antibubbles is based on a version of the Leidenfrost effect, which you can see if you drop water onto a hot pan. The droplets then seem to slide around in the pan almost without friction. This is because the heat from the pan vaporizes the liquid water, essentially allowing it to levitate above the surface. The antibubbles come about similarly, just inside of oil rather than on a surface.

Now I really want an antibubble canon.