Sticky nanotubes hold key to creating standards for nano-manufacturingApril 29th, 2008 - 3:53 pm ICT by admin
Washington, April 29 (ANI): A scientist of Indian origin and his team have precisely measured the forces required to peel tiny nanotubes off of other materials, opening up the possibility of creating standards for nano-manufacturing.
According to Arvind Raman, an associate professor of mechanical engineering at Purdue University, US, the so-called peel tests are used extensively in manufacturing.
Knowing how much force is needed to pull a material off of another material is essential for manufacturing, but no tests exist for nanoscale structures, he said.
Researchers are trying to learn about the physics behind the stiction, or how the tiny structures stick to other materials, to manufacture everything from nanoelectronics to composite materials, nanotweezers to medical devices using nanotubes, nanowires and biopolymers such as DNA and proteins, said Raman.
Flexible carbon nanotubes stick to surfaces differently than larger structures because of attractive forces between individual atoms called van der Waals forces.
The energy it takes to peel a nanotube from a surface was measured in nanonewtons, perhaps a billion times less energy than that required to lift a cup of coffee.
That peeling energy is proportional to the nanotubes interfacial energy, which is one measure of how sticky something is, said Mechanical engineering doctoral student Mark Strus.
The researchers worked together to fine tune the theoretical model, which describes the physics of why nanotubes peel off unevenly.
The nanotubes used in the research had a length of about 6 microns, or millionths of a meter, and were 40 nanometers wide, roughly 500 times thinner than a human hair.
The researchers used an atomic force microscope to measure the peeling forces. The nanotube was attached to the end of a diving-board shaped part of the microscope called a microcantilever.
As the nanotube was pulled away from a surface, the cantilever bent. This bending movement was tracked with a laser, revealing the forces required to peel the nanotube.
Nanotubes offer promise to produce a new class of composite materials that are stronger than conventional composites for use in aircraft and vehicles.
This is a big area of research primarily because the strength of nanotubes can be much greater than that of carbon nanofibers, said Raman.
The findings promise to help researchers understand how geckos are able to stick to surfaces, a trait that could translate into practical uses for industrial and military applications.
Nanotubes also have possible medical applications, such as creating more effective bone grafts and biomolecular templates to replace damaged tissues, which requires knowing precisely how the nanotubes adhere to cells.
Yet another potential application is a nanotweezer that might use two nanorods to manipulate components for tiny devices and machines. (ANI)
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