Can Send Secret Messages?

By combining cutting-edge chemistry with the ancient concept of signaling flares, researchers have made an information-dense fuse that transmits complicated messages as it burns.

The so-called “infofuse” is made from dots of lithium, rubidium and cesium laid on a line of fast-burning nitrocellulose. Different combinations of the metals produce different intensities and wavelengths of light, from visible to infrared. These characteristics can be precisely controlled, allowing the fuses to convey a form of chemical Morse code.

“If somebody is stranded in an unfriendly environment, they may need to communicate without attention-drawing electromagnetic frequencies,” said chemist David Walt of Tufts University. “The infofuses are designed to send signals that are visible in a region of the spectrum that human vision cannot detect, but can be picked up using detectors optimized for that part of the spectrum.”

Infrared-burning flares are the most obvious immediate possible application of the research, which was funded by the Defense Advanced Research Projects Agency and recently described in the Proceedings of the National Academy of Sciences. Other uses, however, will likely be found.

For an environmental biosensor, “the signal would change as a function of something that binds to the fuse itself. Imagine you’d like to know what the concentration of some air contaminant is. The fuse would go off and send a signal modulated by the concentration of the contaminant,” said Walt.

For now, a firecracker-scale infofuse can be detected at distances of up to one-third of a mile. But as researchers refine the technology, infofuses “could open up new opportunities in information technology,” wrote John Rogers, a University of Illinois at Urbana-Champaign material scientist, in a separate PNAS article.