NERVE agents such as sarin and VX can kill quickly in low doses. Kim Jong Nam (pictured), half brother of Kim Jong Il, North Korea’s leader, was recently murdered by having VX smeared on his face at Kuala Lumpur airport. Though the use of nerve agents is supposed to be banned by treaty, governments and terrorists have deployed them, and may do so again in the future. At the moment, there is no simple way for soldiers in the field, or inspectors looking for manufacturing and storage sites, to detect nerve agents. The electrochemical sensors involved are bulky and awkward to use.

On civvy street, meanwhile, similar chemicals are employed as pesticides to ward off insects that might otherwise damage fruit and vegetable crops. If such crops are not thoroughly washed after picking, or have been overdosed in the first place, then they, too, may present a health hazard. Yet inspecting them to see if they are contaminated can also be a hassle.

It would be better all round if people had suitable detection technology available at their fingertips. And Joseph Wang of the University of California, San Diego, reports in ACS Sensors that he has a system that achieves this quite literally.

Sarin, VX and their kind are chemicals called organophosphorus compounds, which can be deactivated by an enzyme known as organophosphorus hydrolase. Existing nerve-agent detectors record changes induced by the presence of organophosphorus compounds in the electrical resistance of gels impregnated with this enzyme. Dr Wang’s trick is to miniaturise the process so that it fits on a glove.

To make their device, he and his colleagues print electrodes made of silver and silver chloride, and of carbon, onto the index fingers of rubber gloves. These electrodes run from the knuckle to the fingertip, where they almost, but not quite, meet. The zone of near-meeting is coated with a layer of gel containing organophosphorus hydrolase. The gel connects the ends of the electrodes together, completing the circuit. The knuckle-ends of the electrodes, meanwhile, are designed to meet a special ring, worn over the glove, that both supplies them with current and transmits information on the strength of that current to a nearby mobile phone—setting off an alarm if the current varies in a way that indicates the enzyme is reacting with a nerve agent.

To gather a residue sample from a surface, the glove’s thumb has a carbon disc printed onto it which the wearer rubs across a suspicious area. All he has to do then is press index finger and thumb together and, if the alarm goes off, he knows the surface in question is contaminated.

Tests with organophosphorus compounds smeared on glass, wood, stainless steel and plastic, and also four types of fruit and vegetable, suggest the idea works in principle. If it works in the field (and if suitable alternative enzymes can be found), it might be extended to the detection of other chemicals of interest, such as gunshot residues, drugs and explosives.