Rosenblatt's team adapted traditional NSOM technology by using polarized light, immersing the fiber into the fluid, and collecting images at a series of heights above the substrate. The result is polarized optical nanotomograpy (ONT), a system for 3D mapping of anisotropic fluid on top of a substrate.
The team chose a nematic liquid crystal, whose molecular orientation is controlled by a nanoscopic pattern scribed into the underlying polymer-coated substrate. This material was chosen because its structure can be readily calculated, giving the team an idea of what they should expect to see through the ONT imaging process.
In their ONT experiment the team immersed an optical fiber with a diameter of 60 nanometers (approximately one-tenth the diameter of the wavelength of light) into the liquid crystal to a position just above the substrate. There the fiber was scanned two-dimensionally over the surface and an image was obtained. They then retracted the fiber by approximately 25 nm and obtained a second image. In principle data from the first image could be subtracted from the second, providing information about the molecular orientation profile at 25 nm above the surface. This process was repeated out to a distance of 500 nm above the substrate. Rosenblatt's team demonstrated that the images at each height were completely consistent with the theoretical predictions, and they were able to make the first visualization and direct measurement of the 200 nanometer length over which the molecular orientation homogenizes.
The research was funded by the U.S. Department of Energy's Basic Energy Science program and the Petroleum Research Fund of the American Chemical Society.
Over the summer Rosenblatt received a three year grant from the National Science Foundation (NSF)
|Contact: Susan Griffith|
Case Western Reserve University