TWO clever pieces of science have opened the door to a faster and more reliable way for forensic experts to detect where explosives have been made and stored.
More than a decade ago researchers in the US developed the concept of using light-emitting plastics to detect explosives residue – a significant advance on the old world approach of droplets on test cards.
Now the University of Adelaide has gone a significant step further by adding special optical fibres into the mix.
"The resulting technology is accurate, easier to use and requires an analysis time of just a few minutes." Dr Georgios Tsiminis
Dr Tsiminis was joined for a year by Dr Fenghong Chu, an Assistant Professor at the Shanghai University of Electric Power in China.
"What I like about this technology is that it has a lot of complicated physics underlying it, but it is really a very simple concept," he said.
Part one of the concept is the plastic material, which can be applied in a thin layer to glass or other suitable materials. It emits red light when illuminated with a green laser, but the amount of light reduces if explosive residues are present.
This allows testing to be carried out on site, rather than having to return to the lab and wait for the results. You simply place a drop of liquid on the glass and apply the laser.
The drawback is that it can be difficult to control both the application and the collection of the light in an open environment, and the process is still a little cumbersome.
This is solved by the use of the optical fibres, which contain three tiny holes (thinner than a human hair) coated with the plastic material. Capillary action draws the liquid through the fibres, and you monitor the light at the other end.
There are two other advantages. You need significantly less liquid for testing (as little as a few billionths of a litre) and the test will tell you not just whether explosives residue is present, but how much (as little as 6.3 parts per million).
“That’s important because it lets you know whether you have levels above what could be just normal background contamination,” Dr Tsiminis says.
This technology only works with TNT-based explosives. However Dr Tsiminis’s broader research focuses on ways to use optical fibres to detect other explosive materials.
A scientific paper on the project is published in the current edition of Sensors and Actuators B: Chemical. Dr Tsiminis has also published a recent paper on his broader research.