A potentially inexpensive miniature sensor able to detect tiny amounts of airborne plastic explosives in just seconds could make it possible to safeguard virtually all airports and key public facilities in the United States. The ORNL micromechanical system (MEMS) has several advantages over conventional plastic explosives sensors, which are bulky and expensive. In comparison, ORNL's sensor consists of a 180-by-25-micron piece of silicon attached to a microcantilever and could be produced for a few dollars. One side of the microcantilever, which is like a tiny diving board, is coated with gold. The gold side is then coated with an acid (4-mercaptobenzoic) sensitive to PETN (pentaerythritol tetranitrate) and RDX (hexahydro-1,3,5-triazine). If these plastic explosives are present, the microcantilever moves and that motion is instantly detected by a laser-microscope that is part of the system. Developer Thomas Thundat of the lab's Life Sciences Division says the device can detect explosives at a level of 14 parts per trillion after just 20 seconds of operation. The work is to be published in the Aug. 18 issue of Applied Physics Letters.
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