Fingerprints comprise secretions of amino acids, fatty acids and proteins, and are normally made visible in one of two ways. At a crime scene where the prints are fresh and still moist, they can be revealed with a dusting powder. But if prints are old and have largely dried out, they can be disclosed by "fuming" suspect artefacts in a sealed cabinet with a vapour of cyanoacrylate - better known as superglue. At a high enough concentration, the superglue vapour reacts with the organic fingerprint deposits to form a conspicuous white polymer that is easily photographed- even when the prints are faint.
However, getting a jerky remote-controlled robot arm to delicately dust a suspect package for prints could detonate the explosive if the bomb is fitted with a sensitive "trembler" switch. So engineers at the University of Calgary in Alberta, Canada, have worked out how to allow a robot to perform the cyanoacrylate fingerprinting technique without touching the package.
The major challenge facing Kristian Thomas and his colleagues was to get rid of the need for the fume-concentrating cabinet, since getting a robot to manoeuvre a package into a cabinet is too risky. Instead they designed a superglue gun that a robot can use to direct a concentrated jet of fumes at the package. That means the robot can be controlled from a safe distance of 100 metres or so.
The gun comprises two cylindrical vials stuffed with steel wool soaked in superglue, with each vial surrounded by an electric heating coil. The coils heat the cyanoacrylate to 65 ¢ªC to evaporate it, while a fan pushes the vapour out of a nozzle fixed to the robot's arm. The large surface area of the steel wool accelerates the evaporation and allows the gun to produce a dense cloud of glue.
After about 15 minutes of fumigation, the person controlling the robot uses its high-resolution camera to snap any fingerprints that show up. "It works fantastically. However, the prototype's durability has to be improved upon before it is ready for police use," says Dave Wood, a sergeant at the Calgary Police Service who commissioned the development of the device after a recent rash of mail bombs had to be destroyed without fingerprinting. He is now seeking further funding - perhaps from the FBI in the US - to improve the technique. The technology would be "one hell of an advantage", says Stephen Haylock of the fingerprint bureau at the City of London Police in the UK. "It would beat sifting through the wreckage and trying to find such evidence." If it is a success, anti-terrorist units are likely to want bomb disposal robots that can perform even more complex tasks. "If they can test it for fingerprints, why not swab it for DNA?" asks Ron Singer of the American Academy of Forensic Scientists in Colorado Springs.
Written by Celeste Biever
New Scientist issue: 1 May 2004
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