Explosive vapor detection using microcantilevers

In-situ detection of explosives is of major importance in several applications: finding hidden explosives in airport luggage and in mail, screening of personnel for concealed explosives, environmental monitoring of explosives-contaminated sites, and detection of buried landmines. Two main types of detectors are being used for explosive detection: bulk detection systems and vapor detectors. However, they both have their disadvantages: high false alarm rates, low efficiency, or too costly.; An experimental technique based on measurement of either a resonant frequency or bending of a microcantilever has been explored in this work. Five different experiments including either optical or electrical detection of signal from a microcantilever were conducted. A traditional approach of measuring a change in resonant frequency of a microcantilever via optical detection was initially pursued to optimize the associated parameters, such as Trinitrotoluene (TNT) pulsewidth, tip flow rate, humidity, etc. Four new techniques were experimented with, and compared for a fast, sensitive, portable, and relatively inexpensive detection of an important explosive such as TNT.; One of the four new techniques was based upon measurement of change in resonant frequency by an electrical method. This technique was found to have a very low detection limit for TNT (∼20 pg); however, it is incapable of confirming an explosive. The other three new techniques were based upon either measurement of change in resonant frequency or upon bending of a microcantilever caused by 'deflagration' of an explosive. Therefore, all three techniques are capable of confirming an explosive. Detection limits in these techniques were found to range from 600 pg to 3000 pg.; In general, newly developed electrical diagnostic based techniques were found to be superior to optical diagnostic based techniques in terms of detection limits, and analysis time. Elimination of bulky components in optical systems means reduction in cost and weight of an explosive detection system. Therefore, it is recommended to pursue further research on electrical diagnostic based explosive detection systems experimented in this research.