Watch How Bubbles in Water Can Be a Powerful Cleaner

Cavitation, or the introduction of bubbles into a liquid, is a phenomenon used throughout the industrial and natural world. Shrimp use it to kill prey, doctors use it to break up kidney stones, and water treatment facilities can use it to purify water.

The details of how cavitation works are a little vague, but a research team led by Professor Sunghwan Jung at Virginia Tech is trying to figure it out.

To do so, the researchers create an underwater bubble next to a submerged glass bead. An electric spark is used to form the bubble and the effects are captured with a high-speed camera.

Part 1: Earlier Stage

In the first part of this video, you can see the spark create the bubble on the right side of the screen. The bubble quickly grows, pushing the glass bead away. The bubble expands to a maximal size and begins to collapse, sucking the glass bead towards it as it does. The bead continues to be sucked in even after the bubble has gone.

Part 2: Different Distances

The second part of the video shows how distance affects the bubble-bead interaction. The closer the bubble is to the bead, the faster the bead is sucked into the space left behind by the collapsed bubble.

Part 3: Different Voltages

Finally, the effect of bubble size is tested. By using a more powerful spark, the team is able to make bigger and bigger bubbles. The last part of the video shows that when they collapse, larger bubbles pull the glass bead towards them more quickly compared to smaller bubbles.

Videos like these have helped describe how collapsing cavitation bubbles physically interact with the particles surrounding them.

Jung believes that understanding how these bubbles disturb nearby objects can help create more effective cleansers. In the future, we may clean our produce with cavitation in order to better wash away harmful substances like salmonella and pesticides.