An interface that can be used to detect explosives has been developed by Swedish scientists.

Thomas Frisk and his colleagues at the Royal Institute of Technology, Stockholm, also used their microfluidic interface to detect nanogram quantities of cocaine and heroin.

Frisk said there was a need for fast, portable and sensitive machines to be designed that could be used by customs officers to detect narcotics and explosives.

His sensor collects airborne materials by absorbing them into a phosphate buffer solution. This solution constantly flows across a silicon surface, patterned with a micrometre sized matrix of columns - like water flowing between the bristles of a toothbrush.

The controlled flow rate, surface tension and capillary forces prevent the buffer solution from overflowing the tops of the columns, allowing the interface to be used in any orientation. The buffer solution flowing out of the interface is then analysed for absorbed materials using the most appropriate detection method.

By maximising the adsorption properties of the interface, the device size and weight could be reduced and detection times halved compared to previous detection systems, said Frisk.

Douglas Weibel, assistant professor of biochemistry at the University of Wisconsin-Madison, believes Frisk's work is 'particularly timely given the global interest in developing rapid, sensitive and portable methods for detecting explosives and toxins in air'

'The recent increase in security levels in public places and in airports is an excellent motivation for [the development of] this technology,' Weibel said.

David Parker