Australian scientists have worked out how to control
fluid at the nanoscale
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Computer modelling has revealed that a simple
technique that can pump fluid in tiny spaces, and could be used to desalinate
water and in lab-on-a-chip devices.
Computer modelling has revealed a simple
technique can pump fluid confined in tiny spaces, and could be used to
desalinate water and to improve lab-on-a-chip devices.
The simple method used a computer model to
predict where highly confined fluids will move, and then used this
information to work out how to "pump" the fluid without the need
for a mechanical pump or the use of electrodes.
Developed by a team led by Swinburne
University of Technology, this is the
first model that has successfully shown how these liquids move on such a tiny
scale.
“Conventional fluid dynamics modelling works
perfectly with things we can see such as the flow of air over an aircraft,” said
Swinburne University of Technology Professor Billy Todd, the study leader, in
a press release.
“But when devices get to nanometre size or 1
billionth of a metre – about one ten-thousandth the diameter of a human hair
– the fundamental assumptions of fluid mechanics break down. It is difficult
to force fluid to flow in confined dimensions that are just a few atoms
thick.”
The researchers used supercomputers to study
the interface between the solid surface and the fluid at nanometre
dimensions, and discovered that using a rotating microwave field they could
effectively pump the fluid.
“Several years ago, researchers in France and
Germany developed a theory that a rotating electric field could induce water
molecules to spin and that this spin motion could be converted into linear
streaming fluid motion,” Todd
explained.
“If the symmetry of the confining walls could
be broken such that one wall was hydrophilic and attracted water, while the
other was hydrophobic and repelled water, then mathematically it was
demonstrated that water could be made to flow in just one direction, namely
along the channel.”
Todd and the team developed this theory
further and performed the first molecular dynamics computer simulations to
demonstrate this effect.
They discovered that using a rotating
microwave field they could pump the water at the nanoscale, without
significantly heating the water.
So far however, this discovery hasn't been
verified in the lab. But if confirmed, it could have big implications for
lab-on-a-chip diagnostic devices and could also help to more efficiently
desalinate water.
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http://sciencealert.com.au/news/20140307-25814.html
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