Friday, July 18, 2014

SCIENCE SPECIAL..... Australian scientists have worked out how to control fluid at the nanoscale

Australian scientists have worked out how to control fluid at the nanoscale


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.

http://sciencealert.com.au/news/20140307-25814.html

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