Bouncing liquid surface can make bubbles do a stop-start dance

Enlarge / Moving bubbles.

Sometimes life just isn't fair. If you play with fluids, you get to use cool camera systems, and every paper fluid researchers write comes with a fancy video of a fluid performing unnatural acts. Then, when you ask about applications, the researchers point to ink jet printers.

This should actually be taken as a warning. If you force a scientist to come up with an application, they will invent the ink jet printer as a form of long-lasting revenge. So, please, don't ask what bouncing superwalker bubbles might be useful for.

Bubble, bubble, toil and... inkjet?

Way back in the '70s, scientists discovered that if you take a droplet of oil and place it on the surface of an oil bath, it will bounce up and down as long as the surface of the bath is vibrating. About 10 years ago, scientists went a step further and showed that if you chose the vibrational frequency just right, then the droplet would move around the surface. Scientists referred to these perambulatory droplets as walkers-perhaps in a tribute to the fragility of walkers in Star Wars.

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