Friend or foe?

 作者:薛两     |      日期:2019-03-08 05:11:03
By Duncan Graham-Rowe HOW do you get a sample of an unidentified and potentially deadly substance from a sealed container without being exposed to it? An ingenious drill bit could be the solution, say researchers at the Los Alamos National Laboratory in New Mexico. LANL’s sampling bit can extract a specimen of a liquid, gas or powder and seal the container safely in seconds, promising a low-risk, cheap and portable technique for inspecting suspect biological and chemical weapons, or unlabelled old drums from heavy industry. Presently, the only safe way to verify the contents of a sealed container is to scan it with a portable isotopic neutron spectroscope or PINS system (This Week, 31 October, p 16). But these cost $120 000 apiece. Roger Johnston, one of the developers, says the new $400 device fits into the chuck of a standard electric drill. The bit is completely contained within the tool and has a silicone cap that temporarily seals the drilled area as the operator applies pressure during drilling. Once the hollow drill bit has penetrated the container wall, it retracts within its housing (see Diagram) and pierces a “vacutainer”—a vacuum-filled device normally used for taking blood samples. With the vacutainer’s seal temporarily broken, the vacuum sucks a measured sample of the unknown contents through a hole in the side of the bit. As soon as this is full, the contaminated bit is fully retracted and the continued rotation of the drill forces a piston forward, releasing an inert flowing sealant called siloxane that plugs the hole. Because the tip of the retracted drill bit will be contaminated, the device still presents a tiny risk of exposure for technicians taking the sample, so LANL has developed a variant that can be left sticking out of the container. This also has the benefit of allowing further samples to be taken. Margaret Tout of Britain’s chemical and biological weapons research unit at Porton Down, Hampshire, says a device that extracts a sample has advantages over remote-sensing. “It’s definite confirmation because you can do a chemical analysis on the sample,