Carbon nanotubes - tiny, hollow structures made of a material related to graphite in pencils - are so small that they may filter out impurities from water flowing through them. The scientific community initially expected that their narrow diameters would slow the water's flow. Surprisingly, early experiments hinted that water is not impeded in the expected way as it passes through nanotubes.
To understand why, a distinguished team of international researchers led by scientists at Tsinghua University undertook an unprecedented, massive computational simulation study powered by IBM's World Community Grid to find out what was behind this surprise. Prior simulations performed by the scientific community were unable to study the process at realistic water flow rates because that would have required considerably more costly computing power than typically available.
The new simulations were conducted using the massive computing power of IBM's crowdsourced World Community Grid, which revealed that under certain conditions, the natural, random thermal vibrations of atoms in nanotubes could have a significant effect on water moving through them. The researchers discovered that these vibrations, called phonons, can actually enhance the rate of water diffusion - a kind of flow - by more than 300%, as a result of reduced friction.
Researchers led by the Center for Nano and Micro Mechanics at Tsinghua University in Beijing performed vast simulations using the donated, surplus processing power of IBM's World Community Grid, which harnesses three million linked computers from more than 700,000 "citizen-scientist" volunteers worldwide. The nearly 100 million calculations performed by IBM's virtual, crowdsourced supercomputer for the Computing For Clean Water project would have cost USD $15 million had they been performed commercially, and would have taken more than 37,000 years had they been performed on a single-processor PC. Instead, the work was completed at no cost to scientists and in a fraction of the time.
With this newfound understanding of the phenomenon, researchers now hope to optimize the nanotubes and apply them to improve water filtration and seawater desalination. As freshwater reserves dwindle worldwide, an improved and less costly purification process could help quench thirst and grow crops. Nearly one billion people around the world currently lack access to safe drinking water.
The new understanding of this phenomenon may also lead to a better understanding of how chemicals and drugs pass through tiny channels in human cell walls, potentially leading to improvements in medicines. With further research, it might also be possible to apply these findings to improve a process that creates energy when freshwater and saltwater are mixed, a process known as osmotic power.
International collaborators who contributed to this important discovery include researchers from Tsinghua University, University College London, Tel Aviv University, University of Geneva, University of Sydney, Monash University, and Xi'an Jiaotong University.
"Prior to our project, simulations of water flow in carbon nanotubes could only be carried out under unrealistically high flow-rate conditions", stated Quanshui Zheng, Director of Tsinghua University's Center for Nano and Micro Mechanics. "Thanks to IBM's crowdsourced World Community Grid, the Computing for Clean Water project could extend such simulations to probe flow rates of just a few centimeters per second, characteristic of the working conditions of real nanotube-based filters."
World Community Grid was conceived and is managed by IBM. Hosted on IBM's SoftLayer Cloud technology, World Community Grid provides massive, free computing power to scientists by harnessing the unused, surplus cycle time of a number of volunteers' computers and mobile devices from all over the globe. World Community Grid software receives, completes, and returns small computational assignments to scientists. The combined power available on World Community Grid has created one of the most powerful and fastest virtual supercomputers on the planet, advancing scientific work by hundreds of years.
More than three million computers and mobile devices used by approximately 700,000 people globally and 460 institutions from 80 countries have contributed virtual supercomputing power for vitally important projects on World Community Grid over the last 10 years. Since the programme's inception, World Community Grid has powered nearly two-dozen important research projects, donating more than one million years of computing time worth $400 million to scientific research, and enabled important scientific advances in areas as diverse as cancer research, AIDS treatments, genetic mapping, solar energy and ecosystem preservation. More than 2.4 billion research tasks have been completed to date; more than 1.5 million new tasks are processed every day.
IBM invites researchers to submit research project proposals to receive this free resource, and encourages members of the public to donate their unused computing power to these efforts at worldcommunitygrid.org .
World Community Grid is enabled by Berkeley Open Infrastructure for Network Computing (BOINC), an open source platform developed at the University of California, Berkeley and with support from the National Science Foundation. The BOINC project choreographs the technical aspects of volunteer computing.