Assessment of microcantilever sensors to detect pure explosive particles and explosive matter dissolved in soil

The insidious nature of land mines has stimulated significant research spanning over half a century, on techniques for mine detection, identification, and remediation. A miniature sensor was designed and fabricated using silicon surface micromachining techniques for explosive particle detection. The sensor is made of bimetallic cantilever beams made of polysilicon and gold. The cantilever deflects upon heating or cooling due to a large difference in linear coefficients of thermal expansion between polysilicon and gold. An optical laser beam deflection system was constructed to detect the deflections of the cantilever.; A number of finite element simulations have been performed to characterize the experimental results. The simulations were performed with various values of Young's modulus and Poisson's ratio, to model the experiments performed on the deflection of gold/polysilicon bimetallic cantilevers with increasing temperature. The simulations give a better fit to the experiments for the Young's modulus of gold as 78GPa and a Poisson's ratio as 0.35 as compared to 57GPa and 0.35. Experiments were also performed on the buckling of the cantilever and its evolution with heat. The results indicate that the extraction of Young's modulus is not affected by the initial residual stress.; The results of using the sensors to detect nanograms of pure explosive particles (TNT and DNT in particular), are presented. The explosive particles are detected based on their unique melting point and thermal kinetics. Results show that these sensors reproducibly detect nanograms of pure DNT. Experiments have also been performed to extract explosives from contaminated soil and further detection. However, the cantilever sensors do not seem very suitable for this method of detection.