Nanotechnology, the science of the very small, touted as promising medical and manufacturing breakthroughs on a molecular level, just got an important tool that will help researchers make good on its hype.
A team of scientists at Brigham Young University publishes in the Feb. 3 issue of "Applied Physics Letters" that they have developed a method that has the potential to help scientists and industry better understand nanotech processes, which could ultimately lead to brighter computer monitors and cell phone screens, increasingly sensitive chemical sensors and more complex replicas of human tissue.
"Traditionally, we've taken large raw materials - a piece of aluminum, a hunk of plastic - and have combined them with other resources to create complex devices and products," said Robert C. Davis, a BYU professor of physics and lead researcher. "This technique gives scientists a better tool to build materials at the molecular level. It helps us figure out how chemical assembly works so we can one day imitate or replicate the process to build materials that are cleaner, lighter and stronger than we have now."
The process is roughly congruent with digging ditches under water and then draining the water from everything but the ditch. Dubbed "nano-chemomechanical patterning," the method uses the tip of an atomic force microscope that acts like a precise "shovel" to scribe patterns on the surface of silicon in the presence of liquid chemicals.
As the microscope cuts the silicon, it breaks strong chemical bonds, destabilizing the silicon so other chemicals will attach to it in a highly stable and reliable manner. The scribed patterns act as a template onto which multiple chemicals can be successively added to fashion complex structures, like rigorous plastics and living cells.
Brent A. Wacaser, a former BYU physics graduate student and first author on the paper, worked with Davis on the project.
"Knowing that others are interested in the work makes the effort we put into the project worth it," said Wacaser, who has since started a doctoral program in nanoscience at Lund University in Sweden. "Working on the project has taught me many skills that I use everyday in my continued research."
One of the technique's benefits is a significant decrease in the size of patterns that can be etched than was previously possible - lines now yield widths of 30 nanometers, roughly 10,000 times smaller than that of a human hair. Previous techniques yielded lines that were 1,000 times larger.
"In large-scale terms, that's roughly equivalent to going from the size of a football field to that of a football," said Davis. "The decrease in size will further helps scientists work at a 'nano' level, giving us even more insight into how chemical assembly works."
The method could be used to enable research that would improve the efficiency and lower the cost of solar cells by unlocking the mystery behind electrical processes involved in their production and facilitate the development of "gene chips," silicon wafers embedded with chemicals that could be used to test for diseases by adding human DNA and observing chemical reactions, said Davis.
Additionally, scientists can save time in the laboratory using the BYU technique - the molecules can be observed with the same atomic force microscope used to create the miniscule patterns. Switching to another machine to look at freshly minted patterns and chemical deposits used to be the norm.
In the past, such patterning also needed to be performed under the rigid and time-intense conditions of a high vacuum state to prevent rogue molecules from interfering with the process. The BYU technique can be performed under ambient conditions, which results in a large time savings to scientists who adopt the new method.
"Initial calculations also show that we should be able to improve the process to go even smaller than we are now," said Davis. "And that's exciting."
The study builds on the long-time work of BYU chemistry professor and co-author Matthew R. Linford. Joining Davis, Wacaser and Linford on the study are BYU physics graduate student Travis L. Niederhauser, physics undergraduate student Michael J. Maughan and Ian A. Mowat of Charles Evans and Associates of Sunnyvale, Calif., an independent analytical services organization.
