Forum for Science, Industry and Business
Sponsored by:     Siemens  n-tv 
Search our Site:

Topic (optional):

 

Home Reports Physics and Astronomy Content

Simulations help explain fast water transport in nanotubes

next article
18.09.2008

By discovering the physical mechanism behind the rapid transport of water in carbon nanotubes, scientists at the University of Illinois have moved a step closer to ultra-efficient, next-generation nanofluidic devices for drug delivery, water purification and nano-manufacturing.

 

"Extraordinarily fast transport of water in carbon nanotubes has generally been attributed to the smoothness of the nanotube walls and their hydrophobic, or water-hating surfaces," said Narayana R. Aluru, a Willett Faculty Scholar and a professor of mechanical science and engineering at the U. of I.


"We can now show that the fast transport can be enhanced by orienting water molecules in a nanotube," Aluru said. "Orientation can give rise to a coupling between the water molecules' rotational and translational motions, resulting in a helical, screw-type motion through the nanotube," Aluru said.

Using molecular dynamics simulations, Aluru and graduate student Sony Joseph examined the physical mechanism behind orientation-driven rapid transport. For the simulations, the system consisted of water molecules in a 9.83 nanometer long nanotube, connected to a bath at each end. Nanotubes of two diameters (0.78 nanometers and 1.25 nanometers) were used. Aluru and Joseph reported their findings in the journal Physical Review Letters.

For very small nanotubes, water molecules fill the nanotube in single-file fashion, and orient in one direction as a result of confinement effects. This orientation produces water transport in one direction. However, the water molecules can flip their orientations collectively at intervals, reversing the flow and resulting in no net transport.

In bigger nanotubes, water molecules are not oriented in any particular direction, again resulting in no transport.

Water is a polar molecule consisting of two hydrogen atoms and one oxygen atom. Although its net charge is zero, the molecule has a positive side (hydrogen) and a negative side (oxygen). This polarity causes the molecule to orient in a particular direction when in the presence of an electric field.

Creating and maintaining that orientation, either by directly applying an electric field or by attaching chemical functional groups at the ends of the nanotubes, produces rapid transport, the researchers report.

"The molecular mechanism governing the relationship between orientation and flow had not been known," Aluru said. "The coupling occurs between the rotation of one molecule and the translation of its neighboring molecules. This coupling moves water through the nanotube in a helical, screw-like fashion."

In addition to explaining recent experimental results obtained by other groups, the researchers' findings also describe a physical mechanism that could be used to pump water through nanotube membranes in next-generation nanofluidic devices.

James E. Kloeppel | Source: EurekAlert!
Further information: www.illinois.edu

next article

More articles from Physics and Astronomy:

nachricht Better way to harness waste heat
20.11.2009 | Massachusetts Institute of Technology

nachricht NIST Demonstrates ‘Universal’ Programmable Quantum Processor
20.11.2009 | National Institute of Standards and Technology (NIST)

All articles from Physics and Astronomy >>>

B2B Search

Product / Service
Company / Organisation

Latest News

Scientists Unravel Evolution of Highly Toxic Box Jellyfish

20.11.2009 | Life Sciences

When good companies do bad things: Examining illegal corporate behavior

20.11.2009 | Business and Finance

UCR plant scientist's research spawns new discoveries showing how crops survive drought

20.11.2009 | Agricultural and Forestry Science

VideoLinks

Event News

Multidisciplinary meeting on Urological Cancers aims to benefit cancer patients

20.11.2009 | Event News

'Golden Age' for clinical psychology in Northern Ireland

20.11.2009 | Event News

New Perspectives in Marine Anti-Fouling Research

11.11.2009 | Event News