A new study has found that “waviness” in forests of vertically-aligned carbon nanotubes dramatically reduces their stiffness, answering a long-standing question surrounding the tiny structures.  Instead of being a detriment, the waviness may make the nanotube arrays more compliant and therefore useful as thermal interface material for conducting heat away from future high-powered integrated circuits. (Left to right) Georgia Tech Ph.D. student Wei Chen, Professor Suresh Sitaraman and Ph.D. student Nick Ginga examine a carbon nanotube sample against a backdrop of scanning electron microscope images of carbon nanotubes. (Georgia Tech Photo: Rob Felt) Measurements of nanotube stiffness, which is influenced by a property known as modulus, had suggested that forests of vertically-aligned nanotubes should have a much higher stiffness than what scientists were actually measuring. The reduced effective modulus had been blamed on uneven growth density, and on buckling of the nanotubes under compression. However, based on experiments, scanning electron microscope (SEM) imaging and mathematical modeling, the new study found that kinked sections of nanotubes may be the primary mechanism reducing the modulus. “We believe that the mechanism making these nanotubes more compliant is a tiny kinkiness in their structure,” said Suresh Sitaraman, a professor in the Woodruff School of Mechanical Engineering at

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