Trace Detection of Energetic Substances Using Silicon Dioxide Microbridge-Based Micro-Calorimetric Sensors

A microbridge based calorimetric sensor is developed for the detection of trace energetic substances by measuring their characteristic temperature change in thermal reactions. The micro-calorimeter is mainly a suspending microbridge made of silicon dioxide (SiO2) and integrated with heating and detecting resistors. It is fabricated based on silicon-on-insulator (SOI) wafers using a front-side releasing method, which is simple, efficient and high-yielding. The tiny microbridge is with an extremely low dimension and achieves low thermal capacity, allows small temperature changes induced by chemical reactions detectable. A limit of detection of sub-100 pg is demonstrated for trinitrotoluene (TNT) by measuring the endothermic and exothermic reactions when heating the preconcentrated TNT to the deflagrating temperature, indicating the ability of the sensors in energetic chemical detection.