Monday, 25 February 2013

How do drops and bubbles stick to surfaces?

Understanding exactly how droplets and bubbles stick to surfaces is a “100-year-old problem”.  People love working with water.  It is cheap, bountiful and still a mystery.  

These guys at MIT used Scanning Electron Microscope and adapted a weaker vacuum that has the ability to change the surface angle and to push and pull droplets across the surface with a tiny wire.  Then they can investigate how these droplets of water stick to the surface at the droplets leading and trailing edges.  

As taken from rdmag:

“People have only been able to make sketches” of how droplet adhesion works, Paxson says. With the new high-resolution imagery, it is now clear that as a droplet peels away from a rough surface, the round droplet forms a series of tiny “necks” adhering to each of the high points on the surface; these necks (which the researchers call “capillary bridges”) then gradually stretch, thin and break. The more high spots on the surface, the more of these tiny necks form. “That’s where all the adhesion occurs,” Paxson says.
This research on surface tension and adhesion could have implications on cooling of power plants, ink & coating research, fabrics, packages and medical devices.  Maybe it might even make a better supersuit.  
It might also help in us to understand several biological process like the lotus effect.  

Read more here: