Science often tries to mimic what nature has already achieved, and nanotechnology is no exception – scientists have developed a method of dry printing nanotubes on to surfaces in a similar fashion to geckos ‘sticking’ to walls.
van der Waals attraction between the hairs on the gecko’s foot and the glass prevent the gecko from slipping. Credit: Bjørn Christian Tørrissen
The electrical attraction – the van der Waals force – between the millions of microscopic hairs on the gecko’s feet and the surface ensure the gecko ‘sticks’ to the wall. Using a similar principle, Rice graduate student Cary Pint is able to transfer forests of single-walled carbon nanotubes (SWNTs) from one surface with a reusable template.
“I realised early on it may be useful to transfer carbon nanotubes to other surfaces,” Pint said, “I started playing around with water vapour to clean up the amorphous carbons on the nanotubes. When I pulled out the sample, I noticed the nanotubes actually stuck to the tweezer.”
Pint etched the nanotubes with water, which weakens the chemical bonds between the tubes and the metal catalyst used to grow them. When placed on another surface, the nanotubes adhere to the surface via van der Waals leaving the catalyst in tact on the template.
Pint and other students at Rice are also investigating ways to take printed films of SWNTS and make them all- or semi-conducting. The techniques represent a move toward a near limitless number of practical applications in sensors, highly efficient solar panels and electronic components.
Dr Robert Hauge, a Rice distinguished faculty fellow in chemistry said: “A big frontier for the field of nanoscience is in finding ways to make what we can do on the nanoscale impact our everyday activities,” adding that being able to align carbon nanotubes in any pattern on any surface is a major advance.
Pint is able to deposit nanotubes on a range of surfaces in easily replicated patterns which could be scaled-up for industrial processes, particularly in nanotube circuitry into electronic devices.