Micropreconcentrator for Enhanced Trace Detection of Explosives and Chemical Agents

The design, fabrication, and testing of a sorbent-coated microfabricated preconcentrator device in complementary metal-oxide-semiconductor is presented. As a sorbent-coated device, the preconcentrator is used to collect, concentrate, and deliver analyte sampled from air for analysis with a detector. The preconcentrator in this paper is based on a perforated flowthrough microhotplate structure that is coated with a sorbent layer to maximize vapor trapping efficiency. The coating sorbs the analytes of interest during the collection phase at ambient temperatures. A thermal desorption cycle is then used to rapidly heat the preconcentrator to 180 degC in 40 ms to release a concentrated wave of analyte. A finite-volume method was used to simulate the temperature distribution on a microhotplate and to model the time to reach the steady-state temperature. The experimental electrical measurements of the device were found to be in good agreement with the predicted values obtained using the finite-volume method. The preconcentrator device was demonstrated by interfacing to the front end of a handheld chemical agent detector and a handheld trace explosives detector. The preliminary results showed signal enhancement for the detection of the nerve agent simulant dimethylmethylphosphonate and the explosive 2,4,6-trinitrotoluene