Microfabricated vapor preconcentrator for portable ion mobility spectroscopy

This paper reports on the design, simulation, fabrication and performance of 6.65 mm × 6.65 mm micromachined vapor preconcentrator devices. The devices are composed of sorbent-coated dual serpentine platinum heaters supported by a 6 μm thick layer of polyimide suspended over a silicon frame. The preconcentrators are designed to allow analyte flow normal to the surface through a 10 × 23 array of 375 μm × 125 μm perforations in the polyimide heater support. This facilitates relatively large airflow through the device while providing intimate contact with the sorbent layer with low pressure drop. In preliminary experiments, the device is demonstrated by interfacing to the front end of a commercial ion mobility spectrometer for trace explosives detection. Samples of 2,4,6-trinitrotoluene from a NESTT (non-hazardous explosives for security training and testing) source were collected on the preconcentrator for 15 min at a concentration adjusted to be just above the detectorʹs noise floor. The results show at least an order of magnitude signal enhancement.