Salads, shampoos and mining to benefit from theoretical
research into droplets
8 August 2006
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. But 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 Dagastine is one of 16 Fresh
Scientists who are presenting their research to school students and the general
public for the first time thanks to Fresh Science, a national program hosted by
the Melbourne Museum and sponsored by the Federal and Victorian governments, New Scientist,
The Australian and Quantum Communications Victoria. One of the Fresh Scientists will win a trip
to the UK courtesy of the British Council to present his or her work to the
Royal Institution. | 
