Elisa Riedo is engaged in making the promises of nanotechnology come to life. By discovering the rules of nanoscience, Riedo is helping engineers who want to build technologies like faster computers, bullet-proof t-shirts and nanorobots get one step closer to their goal.
Recently, Riedo found that while nanotubes are extremely stiff when pulled from the ends, they give when poked in the middle. The larger the radius, the softer they become. Understanding the physical properties of nanotubes could lead to more efficient nanowires and nanoelectronics.
"We know from previous studies that nanotubes are very stiff in the axial direction (end to end) but very little is known about their radial elasticity, mainly because when you're working with tubes that small it's very difficult to poke them without pushing them beyond the point where they will be irremediably damaged," said Elisa Riedo, assistant professor of physics at Georgia Tech.
Using an atomic force microscope (AFM) and testing it with a tip of 35 nanometers in radius, Riedo lightly prodded the nanotubes to measure the elasticity.
By making a very small indentation in the tubes, she was able to measure the radial elasticity of a number of single and multiwalled carbon nanotubes of different radii. As she tested this technique with wider and wider nanotubes, the bigger tubes were more bendable than the smaller tubes.
"We started with single-walled nanotubes and then measured tubes with an increasing number of layers, keeping the external radius twice as large as internal radius," said Riedo. "Our experiments show that for nanotubes with small internal radii, increasing the radii makes them softer. This means that for these tubes, the radial rigidity is controlled by the magnitude of the internal radius, whereas the number of layers plays a minor role."
But, for the nanotubes with larger radii, the elasticity of the nanotubes is almost constant. This could mean that the softening that occurs as the internal radius of a nanotube is increased, is counterbalanced by the stiffening effect that occurs as the number of layers increases, up to the point at which the nanotube's properties reach those of graphite, she said.
Riedo received her doctorate in physics in 1999 at the University of Milan - European Synchrotron Radiation Facility Grenoble (France).