Findings a step toward making new optical materials

Researchers at Purdue have developed a "self-assembling " technique to create a "nearly perfect two-dimensional colloidal crystal, " or a precisely ordered layer of particles, a critical step toward growing three-dimensional crystals... Click here for more information.

WEST LAFAYETTE, Ind. - Chemical engineers have developed a "self-assembling" method that could lead to an inexpensive way of making diamondlike crystals to improve optical communications and other technologies.

The method, developed at Purdue University, works by positioning tiny particles onto a silicon template containing precisely spaced holes that are about one-hundredth the width of a human hair. The template is immersed in water on top of which particles are floating, and the particles automatically fill in the holes as the template is lifted.

The researchers have used the technique to create a "nearly perfect two-dimensional colloidal crystal," or a precisely ordered layer of particles. This is a critical step toward growing three-dimensional crystals for use in optical technologies, said You-Yeon Won, an assistant professor of chemical engineering.

"Making the first layer is very difficult, so we have taken an important step in the right direction," Won said. "Creating three-dimensional structures poses a big challenge, but I think it's feasible."

Findings were detailed in a paper appearing online April 9 in the journal Soft Matter, published by the Royal Society of Chemistry in the United Kingdom. The paper was written by graduate student Jaehyun Hur and Won.

The single-layer structures might be used to form "micro lenses" to improve the performance of optical equipment, such as cameras and scientific instruments, and to control the color and other optical properties of materials for consumer products.

More importantly, the technique represents one of several possible approaches to create "omni-directional photonic band gap materials." Unlike conventional mirrored materials, which reflect light hitting the mirror at certain angles, the omni-directional materials would be "perfect mirrors," reflecting certain wavelengths of light coming from all directions.