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June 06, 2006

Growing nanotubes on AFM tip will speed research and development of nanotubes

Refining this technique so that nanotubes can be grown and weighed at the same time, then the process can be scaled up to many (thousands/millions) of parallel analysis. Like computational chemistry or gene chip arrays it will accelerate the rate of progress in the mastery of nanotubes. Plus it shows that if other nanoscale structures can be grown and measured on AFM tips that it would be a pathway to accelerating trial and error learning of chemical vapor deposition, self-assembly and other currently poorly understood processes, which require fine tuning of optimal conditions.

Instead of a large furnace that is normally used to grow nanotubes as part of the chemical vapor deposition process, the Georgia Institute of Technology researchers grew bundles of nanotubes on a micro-heater built into an atomic force microscope (AFM) tip. The tiny device provided highly-localized heating for only the locations where researchers wanted to grow the nanostructures.

Using arrays of cantilevers operating at different temperatures would allow researchers to accelerate the process for mapping the kinetics of nanostructure growth. Because the cantilevers can be heated and cooled more rapidly than a traditional furnace, batches of nanostructures can be produced in just 10 minutes – compared to two hours or more for traditional processing.

By demonstrating that carbon nanotubes can be growth on an AFM cantilever, the technique also provides a new way to integrate nanometer-scale structures with microdevices.

From the change in the resonance frequency, the researchers were able to calculate the mass of the carbon nanotubes they had grown as approximately four picograms (4 x 10-14) kg.

"We are working on integrating the growing and weighing of the nanotubes so we can do both of them at the same time," said King. "That would allow us to monitor the materials growth as it happens."

Once the two processes are integrated, the researchers expect to increase the number of cantilevers operating simultaneously. Cantilever arrays could allow many different growth temperatures and conditions to be measured in parallel, accelerating the task of charting the growth kinetics to determine the optimal settings.

"This is a platform for materials discovery, so we could test tens or even thousands of different chemistry or growth conditions in a very short period of time," King said. "With a thousand cantilevers, we could do in a single day experiments that would take years using conventional growth techniques. Once the right conditions were found, the production process could be scaled up."

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