C&EN: TODAY'S HEADLINES - Better Detector For Plastic Explosives

STU BORMAN

A sensitive and highly miniaturizable device has been developed for detecting plastic explosives like pentaerythritol tetranitrate (PETN) and hexahydro-1,3,5-triazine (RDX)—the type of explosives used in 2001 by shoe bomber Richard Reid and in 1988 on Pan Am flight 103.

Currently, large and expensive instruments like ion mobility spectrometers are used to detect plastic explosives in airports and other locations. Group leader Thomas G. Thundat and senior scientist Lal A. Pinnaduwage of Oak Ridge National Laboratory and the University of Tennessee and coworkers now demonstrate detection of plastic explosives in air with parts-per-trillion detection limits using a microelectromechanical system [Appl. Phys. Lett., 83, 1471 (2003)]. This sensitivity is “better than any other current technology,” Pinnaduwage says.

In the device, a triangular microcantilever (such as those shown in the photo) is coated on one side with gold and 4-mercaptobenzoic acid, which makes it capable of binding PETN and RDX selectively. When either of those substances binds, the microcantilever bends, and the deflection can be measured with a laser-photodiode system.

“It should be possible to make a handheld sensing device based on the optical detection of cantilever bending,” Pinnaduwage tells C&EN. “We are also working on a nonoptical detection technique that would be even easier to work with in the field.”