UH professor finds new properties in plastics, nanotubes

Anyuan Cao lead author for article in Science magazine

The ubiquitous plastic foam has become an every day fact of life, performing a wide range of tasks in packaging, cushioning, support and construction. But suppose you had a material that could exhibit all the advantages of lightweight foam but also had tremendous strength and flexibility. Imagine the applications in construction, and electrical and mechanical engineering—not to mention the more mundane uses such as plastic utensils, rubber gloves, furniture, electronic games and even toys.

University of Hawaiʻi- Mānoa Professor Anyuan Cao of the Department of Mechanical Engineering and a team of researchers have discovered just such attributes in a commonly known micro-material called carbon nanotubes. Their findings have been published in the November 25th issue of Science magazine.

"Carbon nanotubes are cylindrical carbon molecules about 50,000 times thinner than the human hair, yet exhibit incredible tensile strength," explains Professor Cao, who is the lead author on the article. "Their strength comes from their bonding structure, which is similar to graphite."

"In our paper, we have shown for the first time that when you align a huge number of nanotubes and grow them like a forest, they create a highly resilient structure that can be compressed down to 15 percent of its original thickness and still spring back to its original shape once the pressure is removed. In other words, you can repeatedly bend and fold it and it will not collapse or lose any of its inherent strength.

Conventional foam either cannot be compressed heavily or they have very low structural strength. The structural strength of nanotube material is hundreds of times greater than existing synthetic foams such as those made of latex rubber or polyurethane."

Cao plans future research on tailoring the mechanical properties of nanotube foam-film. He suggests one possible way is to control the wavelength of how a nanotube buckles. With smaller buckling (wavelengths), a nanotube spring can be made stronger. He also plans to pursue applications of nanotube films as energy absorbing systems, actuators and electromechanical devices.

Cao joined the University of Hawaiʻi at Mānoa in July of 2005. Prior to that, he was a postdoctoral researcher at Resselaer Polytechnic Institute.