Orthogonal Sensors for the Trace Detection of Explosives

There is a growing need for an electronic trace detection system that can continuously monitor explosives at trace levels in the vapor phase. Triacetone triperoxide (TATP) is a common explosive used by terrorists as the initiator or the energetic material in improvised explosive devices. TATP still goes largely undetected in many densely populated public venues. Currently, no detection system exists that is capable of continuously monitoring TATP, as well as nitrogen-based explosives such as 2,4-dinitrotoluene. We have demonstrated a thermodynamic sensor platform employing thin film microheaters and metal oxide catalysts that can detect TATP and 2,4-DNT at the parts per billion (ppb) level. The microheaters and catalysts were deposited onto ultrathin alumina ceramic substrates, which are responsible for extraordinary sensitivity. Recently, we have added a conductometric sensor platform to this thermodynamic platform to form an orthogonal sensor capable of interrogating the same catalyst using two different modalities. The orthogonal sensor probes the same catalyst using a thermodynamic protocol, as well as a conductometric protocol where electrical resistivity changes in the catalyst are measured as a function of analyte exposure. The advantages of this added orthogonality in terms of mitigating false-positives and negatives are described within.