| In recent years, the use of improvised explosive devices (IED's) has been the preferred method for terrorist attacks because of their practical development from available resources. From the "Shoe Bomber" attack back in 2001, to the most recent attacks in Paris, IED's have been a vehicle for explosive delivery and of the utmost concern for organizations such as the Department of Homeland Security. Conventional methods for the detection of explosives have resorted to either canines, also known as "drug-sniffing" dogs, or the use of ion-mobility spectrometry. While such methods have proven some success in the field in the past, they are invasive, costly, or most importantly non-continuous. With this in mind, a continuous system for the detection of explosives at trace levels has been developed here at the University of Rhode Island. Recent improvements in the electronic trace detection system have included the use of pre-concentration in addition to the dynamic sensing mechanism. This allows for a controlled and highly concentrated burst of analyte to be delivered to the thermodynamic sensor. With the ultimate goal to fabricate a MEM's based device, a reduction in thermal mass without sacrificing signal response is imperative. To combat the reduction in thermal mass, metal oxide nanowires have been developed to create a library of catalysts that can be used to specifically target explosive molecules. Metal oxide nanowires increase viable sensor surface area by orders of magnitude, which is necessary for the transition to a MEMS based device. Not only has the surface area been increased, but the minimum detection limits for explosives such as 2, 6-DNT have been demonstrated to be improved down to the ppb and ppt levels. Finally, a portable testing setup has been developed which will allow for field-testing and generation of real-time results. By reducing the sensor footprint and reconfiguring the apparatus so that it fits into a carrying case, we will be able to test for explosives in a number of different environments. |
