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The Amazing Bubble

The Amazing Bubble

By Franz Grieser

Bubbles may seem fleeting and fragile but scientists are getting closer to finding the right conditions to turn them into tiny fusion reactors and to recreate the genesis of life itself.

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The ephemeral nature of bubbles is perhaps the reason they catch our eye, be they simple and often beautifully iridescent soap bubbles or streams of bubbles rising rapidly in a glass of carbonated drink.

One remarkable feature of bubbles has captured the attention of physicists and chemists for some time. Under the right conditions they can be converted into transient spherical “mini-pistons: that, when they collapse, produce localised hot spots with core temperatures in excess of 5000°C and pressures of several hundred atmospheres. In the specific case of bubbles in water, the hot spots produced are above water’s super-critical point – where liquid and vapour are indistinguishable and the fluid is more akin to an oil rather than being water-like.

To turn a bubble into one of these thermal reactors requires the interaction of ultrsound with a micrometre-sized bubble in a liquid. Sound is basically a periodic undulation of high and low pressure, and can make a bubble oscillate, expand rapidly and then implode in a fraction of a microsecond. Because the implosion is so rapid, the gases and the vapour of the liquid are trapped inside the bubble, and the mechanical energy of the collapsing bubble goes into heating the bubble’s contents (Fig. 1).

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The full text of this article can be purchased from Informit.