Bofors Schnauzer-a biosensor for detection of explosives

Bofors made an initiative to take a leading position by introducing the Bofors Concept of Demining. The Bofors Concept of Demining comprises concepts for a total system incorporating different technologies that will be the tools for: search and detection of minefields; detection, location and identification of individual mines; destruction of mines; and verification of the work carried out. The crucial item on this agenda is detection, location and identification of individual mines. The overall plan is to build a multisensor system which will be based on in combination: biosensor detectors; ground penetrating radar; and metal detectors. This paper discusses the biosensor which combines microelectronics and micromechanics together with the latest in biotechnology. It works by detecting TNT vapour given off by a mine which is then concentrated into a solvent. A quartz crystal oscillates at a frequency of approximately 8 to 9 MHz. Such a system is very sensitive to changes in the mass of the resonator. Antibodies which are sensitive to TNT are attached on the surface of the oscillator. If the small volume of solvent contains TNT, some of the antibodies will release from the surface of the oscillator. The frequency of the oscillator will then change due to the change in mass. The change in frequency is then detected, and the change of frequency will be in the range of 5 to 25 Hz. If the frequency has changed, the operator will be warned immediately. The system has a sensitivity of less than 10 picogram.