May 12, 2010 One of the biggest obstacles in microscopy and in micro-fabrication is the so-called diffraction limit. This basic law says that the resolution (or sharpness) of an image cannot be better than approximately half the wavelength of the light waves being used to make it. Similarly, when light is used to inscribe patterns on microchips -- a standard process known as lithography -- these features can't get much more narrow than about a quarter the wavelength of the light.
Now scientists at the University of Maryland have pushed this limit, achieving pattern features with a size as small as one-twentieth of the wavelength.
They do this by a clever use of two laser beams racing through a polymer solution. One beam triggers polymerization (long molecules start to link up into even longer molecules) while the other beam turns the process off. Polymerization of very narrow pillars -- much narrower than the wavelength of the light -- occurs in a tiny overlap region between the beams.
The leader of this effort, John Fourkas, says that the size of the tiny polymer structures probably represents the smallest fraction of the incoming radiation wavelength ever realized in the laboratory.
One of the structures made in the Maryland lab is a sphere-like post only 40 nanometers tall (about a million times shorter than the length of a 12-point hyphen "-"). If the polymer structures could be made conducting, then they could possibly be used in making microchips. More likely, Fourkas says, are applications in the area of biochemistry. Since the polymer structures are much smaller than typical cells, they might be used to study cell function. For example, cells could be made to "walk over" the structures, which could be used to trigger a chemical or biological response from the cell.
Additionally, the tiny polymer structures might be useful in adhesives or as channels on microfluidic chips -- little platforms on which chemical reactions can be carried out with nano-liter batches of fluids.
The work is being reported at the 2010 Conference on Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference (CLEO/QELS) May 16-21 at the San Jose McEnery Convention Center in San Jose, Calif., where researchers from around the world are presenting the latest breakthroughs in electro-optics, innovative developments in laser science, and commercial applications in photonics.
Presentation: "High Resolution 3-D Laser Direct-Write Patterning" by John T. Fourkas et al. is at 8 a.m. Tuesday, May 18.
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