Low Power Sensors for Trace Detection of Threats in the Vapor Phase
There is an ever-growing need for a gas sensor that can detect explosives and toxic vapors at the part per billion (ppb) level or better. Triacetone triperoxide (TATP), for example, is a common explosive used by terrorists as the initiator or the energetic material itself in improvised explosive devices (IED’s), that still goes largely undetected in many densely populated venues. Currently, no detection system exists that is capable of continuously monitoring TATP as well as nitrogen-based explosives. We demonstrated a thermodynamic sensor platform employing thin-film micro heaters and metal oxide catalysts that can detect TATP and 2,4-DNT at the ppb level, as well as toxic gases. Researchers at URI have demonstrated the ability to detect a variety of explosives at trace levels by reducing the thermal mass of the sensing platform (substrate). Thin-film microheaters were patterned onto ultrathin YSZ ceramic substrates 40 um thick to achieve extraordinary sensitivity levels. By reducing the thermal mass of the sensing platform even further (from 40 um down to 8 um), unprecedented sensitivity and selectivity were realized. These substrates exhibited highly localized heating and heat transfer characteristics that were anisotropic in nature. Thus, the heat remained concentrated in the area of catalyst with little dissipation into the surrounding area of the ceramic substrate. This eliminated temperature gradients and greatly improved resolution of the measurement. Even though the YSZ substrates have isotropic thermal conductivity, the ultrathin-film YSZ substrates possess a very unique ultralow thermal mass in the z-direction. The future vision for this project is the combination of many sensors into an array, integrated on one substrate, with supporting electronics. Using sensor arrays, “signatures” for explosives and toxic gases of interest can be immediately identified in field locations with reduced false positives and negatives, which is the holy-grail for first responders and security personnel.