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Polymer lasers developed for landmine detection

Research in the School on polymer lasers is being applied towards the creation of devices that may be used in humanitarian de-mining operations. This work has recently been featured in publications from the Royal Society of Chemistry.

Currently sniffer dogs, metal detectors, X-ray, and radar or THz imaging are widely used for detecting mines. Research in St Andrews has been looking at a laser-based alternative to a dog's nose to sniff very low concentrations of explosive vapours.

The new sensors work by a change in the way that some plastics emit light when exposed to the vapour. This sort of approach was first demonstrated by researchers at MIT, who showed that when certain polymer films were exposed to TNT or similar nitro-aromatic compounds some of these molecules went into the polymer and stopped the light emission. This happens due to the interaction between the explosive's molecules and the the polymer chains.

Our research team, consisting of Yue Wang, Graham Turnbull and Ifor Samuel, has developed miniature plastic lasers for detecting TNT-like molecules. By using laser emission from the polymer rather than fluorescence it is possible to increase the sensitivity and detection speed of the sensing process. Within the EPSRC-funded HYPIX project they are developing LED-pumped polymer lasers, which offer the potential for very compact sensors. In collaboration with Neil McKeown at the University of Cardiff, the team has also explored the use of microporous polymers to allow the explosive molecules to quickly penetrate through the light-emitting film to rapidly quench the laser emission.

The integrated semiconductor technologies developed in the HYPIX project (CMOS, nitride microLEDs and organic semiconductors) have also enabled a new approach to fluorescence sensing for explosives. A collaboration between HYPIX partners in St Andrews, Edinburgh and Strathclyde has demonstrated a laboratory prototype microsystem to detect changes in the lifetime of fluorescence from exposure to explosive vapours. After absorbing a very short pulse of LED light, the polymer film continues to fluoresce for a few nanoseconds. When exposed to the explosive vapours the lifetime of the fluorescence is reduced. The microsystem developed at Edinburgh is based on two CMOS computer chips, and can rapidly measure these changes in fluorescence lifetime. The application of the microsystem for explosives detection was recently reported in AIP Advances.

Currently all of the work in HYPIX is at the laboratory proof of principle stage. Aspects of the work are now being developed by the St Andrews team for applications in humanitarian demining, within a large European Project TIRAMISU (Toolbox Implementation for Removal of Anti-personnel Mines, Submunitions and UXO).

First posted BDS 15.5.12