London, June 19 : Princeton University engineers say that using lasers and plastic beads may help affordably create ultra-small features that are required for new generations of microchips.
The experts say that their new technique facilitates the creation of lines and dots that are 1,000 times narrower than a human hair, and believe that it may one day give rise to biological computers and micromachines with applications in medicine, optical communications, computing and sensor technologies.
Assistant Professor Craig Arnold and graduate student Euan McLeod say that their technique is similar to poising a magnifying lens over a scrap of paper, and angling the lens to focus sunlight and ignite the paper.
The researchers say that, in place of the lens, they use a microscopic plastic bead floating in water to focus light from a powerful laser, and burn designs onto a blank microchip.
They say that their approach involves an innovative way that ensures that the bead is always the same distance from the microchip, which allows them to draw on the surface with high levels of precision.
"One of the biggest challenges in probe-based nanopatterning is regulating the distance between your probe and the surface of the microchip. We used a special laser to trap the bead and keep it close to the surface without touching it," Nature magazine quoted Arnold as saying.
He said that the research team had, so far, used their new technique to "draw" features that were about 100 nanometers in size.
The researcher revealed that the key to their innovation was a highly focused laser that could exert a physical force on the bead, trapping it in the beam and pushing it down toward the surface.
The researcher added that the surface pushed back with a constant force, and the bead settled at a height that balances the opposing forces. The original laser would then be pulsed at the bead, which would focus the light to "zap" the surface directly below.
According to him, moving the bead along a computer-controlled trajectory, while repeating the laser pulse, might help create any desired pattern.
The research team believes that their technique will be particularly beneficial for drawing patterns on curved or irregular surfaces because the bead tracks the surface by moving up when there is a bump, and dropping when it moves over a dip.
Since the Princeton technique can be performed in a regular environment, it will be accessible for use with biological materials and other systems that require the presence of oxygen.
"The technique provides a very interesting new capability to expand laser-assisted nanofabrication without involving moving mechanical parts and related hardware complications. I do expect that this novel technique will advance nanopatterning since it offers an elegant and highly effective means for parallel, optically driven and controlled nanofabrication," said Costas Grigoropoulos, mechanical engineering professor at University of California-Berkeley.
Arnold and McLeod say that besides burning away part of a chip, their method also has the potential to deposit materials on surfaces, and thus may provide a new means of creating three-dimensional structures, such as miniscule guides that manipulate light and nanoscale electrical-mechanical devices.
Such devices may have many potential uses in ultra-small sensor systems and low-power computer processors, they add.
"In the future, we imagine the use of multiple beads of different shapes and sizes -- in essence a nanopatterning toolkit -- for researchers to pick and choose during the course of fabrication," said Arnold.
Reporting their work in the journal Nature Nanotechnology, the researchers have revealed that they are presently working to pattern a surface using an array of many beads moving in parallel, each trapped and controlled by a different laser beam.