The Amazing World of Bubbles: Chris Brennen

This event was digitally recorded and is available for viewing on the Caltech Theater site. Many past Watson Lectures are available for viewing online on the Caltech Theater site, and are available for purchase: DVD Order Form (PDF)

We generally think of bubbles as benign and harmless, yet they can manifest the most remarkable range of physical effects. Some of those effects are the stuff of our everyday experience: the tinkling of a brook, or the sound of breaking waves at the beach. But even these mundane effects are examples of the ability of bubbles to gather, focus and radiate energy (acoustic energy in the above examples).

In other contexts that focusing of energy can lead to serious technological problems, such as when cavitation bubbles eat great holes through ships' propeller blades or cause a serious threat to the integrity of the spillways at the Hoover Dam. In liquid-propelled rocket engines bubbles pose a serious threat to the stability of the propulsion system and in artificial heart valves they can cause serious damage to the red blood cells. In perhaps the most extraordinary example of energy focusing, collapsing cavitation bubbles can emit not only sound but also light with black body radiation temperatures equal to that of the sun.

But, harnessed carefully, this ability to focus energy can also be put to constructive use. Cavitation bubbles are now used in a remarkable range of surgical procedures to emulsify tissue, most commonly in cataract surgery and in procedures for the reduction of kidney and gall stones. By creating cavitation bubbles non-invasively and thereby depositing energy non-intrusively, one can generate minute incisions or target cancer cells.

This lecture will begin by ranging over the past history of these phenomena (including Caltech s special role in their discovery) and will end with a vision of the new horizons for the remarkable bubble.

Chris Brennen is the Richard L. and Dorothy M. Hayman Professor of Mechanical Engineering at Caltech.

Chris Brennen

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