One of the biggest barriers to advances in nanotechnology has manipulating objects at such a small scale. Scientists can make balls, rods and tubes that are only billionths of a meter in size—and have developed techniques to get them to self assemble in different patterns—but tweaking the structure of individual nano-scale particles without breaking them down has proved problematic.

A technique for creating more flexible nanotubules that pulsate in response to temperature changes could help make these materials easier to work with and reveal new uses for them, according to a team of scientists from Korea's Seoul National University, Japan's Nagoya University and China's Harbin Institute of Technology. The researchers report in Science this week that they were able to use ring-shaped molecules to construct mini cylinders containing spherical carbon "buckyball" fullerenes. When exposed to rising temperatures, the cylinders constricted to about half their diameter, expelling the buckyballs in the process without fully collapsing. Drop the temperature a bit and the procedure could be reversed, expanding and pulling nanoparticles back into the nanotubule.

Although far from having immediate pragmatic applications, the researchers essentially created the components of a nano-scale circulatory system. Or, to use another analogy, the process could create "thermo-responsive 'pulsating nanotubes,' just like cylinders in engines" that may be able to convert thermal energy into multi-directional motion, write Wei Zhang, a postdoctoral materials researcher at Japan's Riken Advanced Science Institute, and Takuzo Aida, a University of Tokyo professor of chemistry and biotechnology, in a Science Perspectives article analyzing the research.

Image courtesy of Zhegang Huang, Seoul National University