How to levitate a droplet on a liquid surface

Michela Geri - 2017-11-14

When a drop is released close to a bath of liquid (e.g. water or oil), our common sense tells us that the two should coalesce almost immediately. However when we pour drops of cold cream on our hot coffee or we observe raindrops over a puddle, we can often see the droplets floating on the surface for much longer than expected...so what happens? In this video we show that a temperature difference between a droplet and a bath can help levitate droplets without any direct contact!
For more details, see our paper @JFluidMech "Thermal delay of drop coalescence", by M. Geri, B. Keshavarz, G. McKinley and J. Bush.

Fluids in the video:
- cream on coffee
- silicone oils (1cSt...similar to water!)

SassePhoto - 2017-11-16

Absolutely wonderful! So beautifully filmed, very inspirational, thank you!

David Hasin - 2019-07-15

I have read your paper in JFM. Fascinating! I'm gonna try to reproduce the results in my lab:)

eunnieverse - 2017-12-19

Amazing!! So much hard work. Thanks for sharing.

Will Pack - 2017-11-17

Thanks for the video, but I wish it was more clear at the end. Seemed a bit blurry to me.

Splax - 2017-11-16

Came here from Vox. Cool stuff!

zoiuduu - 2017-11-20

can i have more fps next time please?

JAPANESUS - 2019-08-01

I was taking a shower last week and i watched what appeared to be a tiny droplet of water floating around for a few minutes.. I'm 99% positive it wasn't a soap bubble. It didn't move the same as a soap bubble, it didn't look like a soap bubble.. After watching it long enough i reached out my hand to see if it'd land on my hand and stay there, like i'd assume a soap bubble would but as soon at touched my hand, it vanished.. What did experience?? I was searching for an answer and found this video.

Nathan EverLast - 2020-03-20

https://youtu.be/Xs60XVXMUUo

Samy Kamkar - 2017-11-23

Cool video! The test at 2:00 doesn't seem to be the same as the others though, as it appears the tip of the dropper is still touching the water droplet, thus the water could be using Van der Waals forces to remain "stuck" to the tip, especially if there's more water up there. This may not technically be the case but it's difficult for viewers to tell when all the other droplets independently fell from gravity, and this one did not. Anyway, thanks for the video!