Trace 2,4-dinitrotoluene detection using suspended membrane micro-hotplate based on heat absorption monitoring

Detection of trace explosive has become an outstanding research activity recently, and there is a demand for fast and reliable detection techniques. In this paper, the detection of trace 2,4-Dinitrotoluene (DNT) as a nitroaromatic explosive based on heat absorption monitoring (HAM) is introduced which employs heat absorption phenomenon during melting process of explosive particles. Thermodynamic analysis shows that the sensitivity of HAM sensor will be enhanced by increasing of heating efficiency; therefore, the sensor has been designed based on suspended-type membrane (STM) micro-hotplate with the small active area and narrow tethers to achieve high heating efficiency. The designed sensor is fabricated by a simple micro-fabrication process using bulk micromachining technology and the electrical and thermal characterization is performed. Experimental results demonstrate that the fabricated HAM sensor is capable of detecting DNT as little as 20 ppb within 72 ms by the applying power of 3.7 mW. Moreover, the fabricated sensor shows higher selectivity to DNT than other explosives when it is regulated to the melting point of DNT, and to detect DNT concentrations above 150ppb, run-to-run repeatability and device-to-device reproducibility are better than 4%-9%.