Gecko's Lessons Transfer Well
Watch a gecko walk up a wall. It defies gravity as it sticks to the surface no matter how smooth it appears to be.
What's happening isn't magic. The gecko stays put because of the electrical attraction - the van der Waals force - between millions of microscopic hairs on its feet and the surface.
The principle applies to new research at Rice University reported this week in the online version of the journal ACS Nano. But in this case, the hairs figuratively come off the gecko and plant themselves on the wall.
Rice graduate student Cary Pint has come up with a way to transfer forests of strongly aligned, single-walled carbon nanotubes (SWNTs) from one surface to another - any surface - in a matter of minutes. The template used to grow the nanotubes, with its catalyst particles still intact, can be used repeatedly to grow more nanotubes, almost like inking a rubber stamp.
Pint is primary author of the research paper, which also details a way to quickly and easily determine the range of diameters in a batch of nanotubes grown through chemical vapor deposition (CVD). Common spectroscopic techniques are poor at seeing tubes bigger than two nanometers in diameter - or most of the nanotubes in the CVD "supergrowth" process.
"This is important since all of the properties of the nanotubes - electrical, thermal and mechanical - change with diameter," he said. "The best thing is that nearly every university has an FTIR (Fourier transform infrared) spectrometer sitting around that can do these measurements, and that should make the process of synthesis and application development from carbon nanotubes much more precise."
Pint and other students and colleagues of Robert Hauge, a Rice distinguished faculty fellow in chemistry, are also investigating ways to take printed films of SWNTs and make them all-conducting or all-semiconducting - a process Hauge refers to as "Fermi-level engineering" for its ability to manipulate electron movement at the nanoscale.
Combined, the techniques represent a huge step toward a nearly limitless number of practical applications that include sensors, highly efficient solar panels and electronic components.
"This pattered array of nanotubes was stamped - by hand - by Rice graduate student Cary Pint. He grew millions of nanotubes in lines on an alumina template, transferred them to a window, grew another set on the same template and stamped them over the first to make the grid. (Credit: Image courtesy of Rice University)"
Source: Rice University
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