Multiplexed Agent Detector with Cavity Ring-Down Spectroscopy (MADCaRS)

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Biotechnology OBJECTIVE: Develop an infrared cavity ring-down spectroscopy-based system possessing a large dynamic range for the rapid, sensitive, and selective identification of vapor phase and aerosol phase chemical warfare agents (CWA). DESCRIPTION: Vapor phase detection techniques of CWAs are often not specific or are restricted to very specific and/or narrow concentration ranges, causing frequent false positive and dynamic range issues. Additionally, current commercial technology that has greater specificity or a larger dynamic range are typically benchtop systems and not portable for the warfighter. Vapor and aerosol challenges are not static and can continuously evolve both in type of challenge and in concentration; therefore, there is a need for a robust system that can detect chemical warfare agents and other toxic industrial compounds (TICs) and can be carried by the warfighter. While some systems exist and claim to have a large dynamic range, the ability to detect a library of compounds, and are man-portable, no known man-portable systems exist that can provide rapid, sensitive, and selective chemical identification, even on unknown compounds outside of a pre-built library, over a large dynamic range. This infrared-based prototype will provide the warfighter with rapid feedback of any potential threats within the local vapor environment. The goal of this project is to develop an infrared cavity ring-down spectroscopy-based system with a large dynamic range from 100 ppb to 1000 ppm of all traditional agents (VX, GB, and HD), potential for non-traditional agents (NTAs), TICs such as phosgene, ammonia, or cyanide, as well as aerosolized liquid CWA. The lower end of the dynamic range will be of focus for the CWAs whereas the higher end of the dynamic range will be the focus for the TICs. The final prototype must not be limited to this set of challenges and must be able to update detection algorithms for new compounds. The final prototype must be less than 10 pounds, less than 16 L in volume, and continuously read in at least 60 second intervals with capability to modify interval length. The final prototype must be completely contained (i.e. not require outside gases, etc.) and can run on battery (warfighter portable), shore power (leave in place/perimeter applications), or through the means necessary for an unmanned system. The form factor must be amenable to deployment in adverse environments with temperature and humidity fluctuations from 0C to 45C and from 0% relative humidity (RH) to 90% (or non-saturating at respective temperature range). The system must be able to clear back to baseline signal within five minutes. Additionally, the prototype must use artificial intelligence/machine learning (AI/ML) for library building and/or spectral matching to enhance detection capabilities. PHASE I: Establish proof of concept by developing a bread-board device that clears down in the appropriate amount of time and can capture signal at or below 1 ppm of two CWA simulants at room temperature and approximately 50% RH. The signal capture must take no more than 60 seconds and provide a result. Identify optimized geometry for prototype and establish any logistic requirements for prototyping. PHASE II: Demonstrate system feasibility meeting outlined requirements including environmental requirements across at least two different temperatures and two different relative humidities which includes laboratory method validation and assessment of instrumentation. The prototype must meet the concentration requirements for at least two of the listed compounds (including one CWA) and must have detectability within the range for all compounds listed with the target range for the CWAs on the lower end of the dynamic range and the range for the TICs at the higher end of the dynamic range. CWA testing must be completed in an approved surety laboratory. The sensitivity for each listed compound will be established. A user assessment will be conducted to identify general improvements. PHASE III: Continued development and assessment at remaining temperatures and humidity levels and optimization of user interface. Finalize design/form factor for commercialization. Conduct final user assessment to incorporate modifications to design. PHASE III DUAL USE APPLICATIONS: This technology would be useful to civilian first responders, leave-in-place detectors at large social events, or in perimeter monitoring around various municipal facilities for vapor leakage. REFERENCES: 1. Zhang, Z.-T.; Cheng, C.-F.; Sun, Y.; Liu, A.-W.; Hu, S.-M., Cavity ring-down spectroscopy based on a comb-locked optical parametric oscillator source. Optics Express 2020, 28 (19), 27600-27607. 2. Dhall, S.; Mehta, B. R.; Tyagi, A. K.; Sood, K., A review on environmental gas sensors: Materials and technologies. Sensors International 2021, 2, 100116. 3. Maity, A.; Maithani, S.; Pradhan, M., Cavity Ring-Down Spectroscopy: Recent Technological Advancements, Techniques, and Applications. Analytical Chemistry 2021, 93 (1), 388-416. 4. Cotterell, M. I.; Knight, J. W.; Reid, J. P.; Orr-Ewing, A. J., Accurate Measurement of the Optical Properties of Single Aerosol Particles Using Cavity Ring-Down Spectroscopy. The Journal of Physical Chemistry A 2022, 126 (17), 2619-2631. KEYWORDS: CRDS, IR, vapor, agent, rapid, aerosol