Magnetic 'snakes' for storage devices?
According to a weekly digest from the American Physical Society (APS), physicists at Argonne National Laboratory (ANL) have found that under certain conditions, magnetic particles could form magnetic 'snakes' able to control fluids. According to the researchers, this 'magnetic self-assembly phenomena may be used to make the next generation of magnetic recording media or transparent conductors based on self-assembled conducting networks of magnetic micro-particles.' By digging further inside ANL labs, it seems apparent that storage devices based on these magnetic 'snakes' will not appear on the market before a long time.
You can see above one of these magnetic 'snakes' (Credit: ANL). This image has been extracted from a short movie (QuickTime format, 5 seconds, 2.77 MB). You really need to watch it...
And the image above shows a "self-assembled magnetic 'snake' and associated velocity patterns. The snakes are spontaneously created from short chains of magnetic micro-particles as a result of the competition between magnetic and hydrodynamic forces. (Credit: ANL). Here is a link to a larger version.
This research work has been achieved at ANL's Materials Science Division by Alexey Snezhko, Igor Aranson, Maxim Belkin and Materials Science Division Wai-Kwong Kwok.
An ANL news release, "Self-assembling 'magnetic ‘snakes' point to new electronic devices," provides additional details about these snakes. "The undulating, snake-like patterns are created when magnetic micro-particles floating on water are exposed to an alternating magnetic field. These magnetic "snakes'' are spontaneously created from short chains of magnetic micro-particles as a result of the competition between magnetic and hydrodynamic forces. Their internal structure and magnetic ordering can be effectively tailored by adjusting the external magnetic field."
Here is a quote from Snezhko about this project. "The self-assembled materials that automatically arrange themselves into useful patterns in a controlled electric and magnetic field environment have tremendous potential as components in micro- and nano-scale devices."
And what will be some possible applications for these 'snakes'? "The magnetic self-assembly phenomena may be used to make the next generation of magnetic recording media or transparent conductors based on self-assembled conducting networks of magnetic micro-particles. Magnetic snakes may also lead to new micro-fluidic devices for bioanalysis in which an alternating magnetic field can be used to assist transportation of micro-particles through micro-channels in biochips."
This research work has been accepted for publication by Physical Review Letters, one of the journals of the American Physical Society, but it is not yet available online. In the mean time, you might want to read "Dynamic Self-Assembly of Magnetic Microparticles: Surface Wave Assisted Magnetic Exchange," a previous research on the same subject done at ANL. "An ensemble of magnetic microparticles at the liquid/air interface displays novel snake-like self-assembled structures induced by an alternating magnetic field. These structures are directly related to surface waves in the liquid generated by the collective response of magnetic microparticles to the alternating magnetic field. The segments of the `"snake" exhibit long-range antiferromagnetic ordering mediated by the surface waves, while each segment is composed of ferromagnetically ordered chains of microparticles. The discovery of a remarkably rich dynamic assembly of magnetic field driven magnetic micro-particles suspended on a liquid/air interface represents a significant breakthrough in our understanding of the complex physics of self-assembly."
You'll find more details and pictures by reading this project's highlights (PDF format, 2 pages, 217 KB) and a poster (PDF format, 1 page, 324 KB).
Sources: American Physical Society news release, September 24, 2007; and various websites
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