Ultra-portable explosives sensor
Presently, there is a strong demand for rapid in-field methods for the detection of explosives compounds for purposes as the detection of roadside bombs, landmines and for airport security checks.
Conjugated polymers are a promising chemosensory material for explosives detection, as vapours from explosives such as TNT can strongly interact with films of the polymers and produce an easily detectable change in their optical properties. For example, exposure to explosive vapour can increase the non-radiative relaxation rate of the polymer, so by monitoring the lifetime, τ, of the polymer it is possible to detect the presence of explosive vapours.
Integrated CMOS-controlled micro-LEDs
In collaboration with the University of St. Andrews and University of Edinburgh, our group was involved in the development of a compact explosives detection system which integrated CMOS-controlled micro-LEDs, a film of conjugated polymer and an array of single-photon avalanche diodes (SPADs) .
In this system the CMOS-controlled micro-LEDs were used to generate nanosecond optical pulses to excite the conjugated polymer, and the SPAD array was used to monitor the lifetime of the polymer. A decrease in the lifetime of the polymer could in only a few seconds, allowing the presence of explosive vapours to be rapidly detected with a sensitivity of ~10 parts per billion (ppb). The conjugated polymer film can then be reset by a blast of nitrogen to remove the explosives vapour. The CMOS-controlled micro-LED and SPAD hardware is compact. The chemosensory polymer layer can be made very cheaply as it is made from plastic. This system offers a compact and cheap solution for explosives sensing.
This work was originally reported in the journal AIP Advances , but attracted much interest in the press and has been reported by outlets including BBC News and New Scientist magazine.
Listen to an audio interview on this work with Professor Ifor Samuel, of The University of St. Andrews.
 Y Wang et al. "Ultra-portable explosives sensor based on a CMOS fluorescence lifetime analysis micro-system", AIP Advances, 1, (3), p032115, (2011).