[ASC-media] More to droplets than meets the eye

Sarah Brooker sarah.brooker at gmail.com
Wed Aug 9 16:06:17 CEST 2006

Salads, shampoos and mining to benefit from theoretical research into

How much effort does it take to understand the behaviour of oil droplets? A
multi-disciplinary team of six researchers from the University of Melbourne
has spent the best part of two years, and used $300,000 of equipment to
crack the problem. 

They have developed a technique to measure the tiny forces between droplets
in liquids. The result could be the improvement of the design and production
of everyday products worth hundreds of millions of dollars.

For the first time, the researchers can measure the attraction between oil
droplets in water-and this has application for products ranging from milk
and ice-cream to shampoos, drugs, and even mineral processing.

All these instances involve emulsions, the dispersion of droplets of oil
through water.

"This was a truly multi-disciplinary effort," says team member Dr Raymond
Dagastine from the Particulate Fluids Processing Centre in the Department of
Chemical and Biomolecular Engineering. 

"We had chemists, chemical engineers and mathematicians all working together
because, not only did we have to figure out how to hold and push two tiny
droplets together, and how to measure their interaction, but we also needed
to interpret the information we collected."

An experimental tool known as an Atomic Force Microscope was used to drive
two oil droplets together in water very carefully at different speeds. The
researchers developed a theoretical analysis to describe the collisions. In
the end they were able to measure, understand and even predict how emulsion
droplets interact with each other.  

Emulsions are made of droplets of one liquid colliding with each other in
another liquid. Some droplets collide and bounce away, while others can
collide and stick together or coalesce. It may seem simple, but the physics
behind controlling whether the oil and water remain dispersed or how fast
they separate is a key variable in the purification steps in pharmaceutical
and minerals processing.

In addition, the separation that happens in salad dressing can be prevented
from happening in products such as shampoo, milk and even ice cream. "It all
could lead to improvements such as shampoos that clean better and mineral
processing equipment that is smaller and more efficient," Raymond says.

This work was recently published in Science the weekly journal of the
American Association for the Advancement of Science.

Raymond is one of sixteen Fresh Scientists participating in a media boot
camp at Melbourne Museum.

The best Fresh Scientist will win a study tour of the United Kingdom
courtesy of British Council Australia.

For more information or to interview: Raymond Dagastine on 0403 053 880

Media contacts: Sarah Brooker on 0413 332 489 and Niall Byrne on 0417 131
977 or niall at freshscience.org and visit www.freshscience.org

University of Melbourne Media Officer Rebecca Scott 0417 164 791  

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