APS News

Nanotech Advances Include Data Storage and Sharper Metal Tips

New advances in nanotechnology keep pushing the smallest limits of what is possible, with this year’s March Meeting featuring over one hundred sessions exploring potential technology on the scale of the very tiny. Two physicists were among those asked to present their results in a press conference format as well.
Izhar Medalsy, of the Hebrew University in Jerusalem, described a novel method to store bits of data on a nanoscale. He combined a natural protein with clusters of silicon nanoparticles to create arrays of stored bits of information as close as 11 nanometers apart.

A slightly altered version of the aspen tree’s donut-shaped SP1 protein is an ideal scaffolding to suspend the information storing nanoparticles. Medalsy found that the ends of nucleotide strands in the protein could be manipulated to act as hooks for round silicon nanoparticles. These nano-sized semi-conducting spheres do stick out of the protein slightly, like a crystal ball over its wooden base. The individual silicon nanoparticles can then be infused with either a positive or negative electric charge to store individual bits of data. One added advantage of using such a system is that particles can exist in one of three states (positive, neutral and negative) rather than the standard binary that computer systems use today.

“The implementation of two and three states memory unit cells with a protein scaffold that can form large ordered and dense arrays suggests applications such as ultra dense and much more economic memory arrays,” Medalsy said.

Medalsy used a Langmuir Blodgett trough to arrange the proteins in a dense honeycomb film over a smooth gold surface. The proteins act as insulators between the conductive surface and the silicon particles. This allows the particles to retain their charge for several minutes under normal atmospheric pressure, and as long as a few hours in a vacuum.

With further development, Medalsy said that the surfaces could potentially be used to store large amounts of data more densely than today’s DVDs. Currently devices to efficiently record and later read information stored on such a dense scale do not yet exist.

A further application for Medalsy’s protein and nanoparticle combination would be to create nanoscale wires. Instead of compressing the proteins together horizontally to make a film, they could be stacked vertically so that conductive gold nanoparticles would contact each other and transfer charge along the wire. Thus far Medalsy has only been able to bring the stacked nanoparticles within 3.5 nanometers of each other, which is not close enough to transfer charge. He is continuing his research to bring the particles close enough together allow electricity to flow freely.

At the same press conference, Abha Misra of Caltech presented her new technique for manufacturing sharp metal tips for nanoprobes. Probes with carbon nanotube tips have in recent years emerged as an excellent method for technicians to manipulate nanosized objects. However up to now, when a metal coating is applied around the outside of the carbon nanotube, its tip is rounded off, limiting the probe’s effectiveness. Misra’s new technique allows iron to naturally form a tip sharp enough to work with atomic scale resolution.

“With these tips not only can we resolve problems related to the  ultra high resolution imaging of nanostructures but also … to observe magnetic behavior at atomic scale in spite of using a coated material tip.” Misra said.

She began by wrapping carbon nanotubes around a thin core of iron. Upon severing these nanowires using a high-energy electron beam, the surrounding carbon tubes retract back from the end. At the same time, the energized iron core flows forward, crystallizing into points sharper than otherwise possible by simply coating the nanotubes.

This process could also be used to weld two of these nanowires together. Misra demonstrated that the excess iron that flowed out from the carbon tubes could be melted by the same high-energy electron beam and rejoined. This process could lead to future nanotechnology repair techniques.

“These probes also provide means for coupling of nanoelectronic devices, by using them as a nanoscaled soldering iron,” Misra said, “This technique adds a new functionality in nano-electromechanical systems and offers new avenues for further investigations.”

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Editor: Alan Chodos