Researchers at MIT have found what they are calling a novel method for etching extremely narrow lines on a microchip using a material that can be switched from transparent to opaque, and vice versa by exposing it to certain light wavelengths. Not a new approach, however the researchers employ a unique way of harnessing the property to create a mask with exceptionally fine lines of transparency. This mask can then be used to create a correspondingly fine line on the semiconductor material. The researchers exposed a photochromic material, one that changes color and therefore its transparency, to a pair of simultaneous light patterns, each of a different wavelength. When the bright lines at one wavelength coincide with the dark lines at the other wavelength, extremely narrow lines of clear material are formed interspersed with the opaque material. The banded layer then serves as a mask through which the first wavelength illuminates a layer of material underneath. Using this method, the team produced lines 36-nm wide and claim they can place many such lines spaced a similar distance apart. For more details, contact Elizabeth A. Thomson at the MIT news office via e-mail at thomson@mit.edu or telephone at (617) 258-5402.