Science features engineers' creation

During this process, molecules organize themselves into larger, three-dimensional objects. What's more, they glow, or fluoresce, and they are among the most well-defined, discrete structures scientists have ever created through self-assembly.

The colorful hollow spheres and cylinders, solid rings, and flat disks are 1,000 times bigger than the previous largest synthetic self-assembled structures, say Professor Samson Jenekhe and graduate student X. Linda Chen. Each object is made up of millions of molecules that organized themselves together.

"In the world of self-assembly, these structures are giant," Chen said.

In the growing field of self-assembly, scientists design molecules that can assemble themselves into much larger, functioning objects. They draw inspiration from nature, where proteins and cells are genetically encoded to grow and precisely arrange themselves into functioning entities.

"A human being is the ultimate in self-assembly: An egg and sperm join, and the embryo grows and develops into a human being," said Jenekhe, Chen's adviser and a professor of chemical engineering, chemistry, and materials science. "Through our research not only do we take advantage of some of the self-assembly techniques nature uses, but we hope to shed light on the biological process as well."

The largest of the team's structures are 50 micrometers long, bigger than the largest bacteria known and most human cells, but smaller than the width of a human hair. Just a few years ago, chemists believed the self-assembly of such large objects would remain elusive until early in the 21st century.

Jenekhe, whose work is supported by the National Science Foundation and the Office of Naval Research, predicts that the new self-assembly technique may be useful in a wide range of fields, including drug delivery, cosmetics, adhesives, pesticides, biomaterials, sensors, pollution control, composites, coatings and paints, and photographic and imaging media.