MAY 30, 2024 – Compact, throwable sensors allow the Joint Force to remotely identify chemical threats in the air.
Advancements in small, chip-based optical readout packages, coupled with low-power electronics and wireless communications modules, have led to developing a hands-free colorimetry-based chemical sensor that effectively acts as a self-reading M8 Chemical Detection Paper used to detect the presence of nerve and blister chemical agents as vapor-phase chemical threats.
Colorimetric chemical sensors are some of the simplest and lowest-cost sensors available to the Joint Force today, yet they are not fully utilized due to ambiguities in visually detecting a color change in the sensing element. Colorimetric papers work well for liquids; the challenge is getting them to work quickly for vapors. Coupling the colorimetric sensing element with an electronic readout creates a more reliable detection mechanism.
The Defense Threat Reduction Agency’s (DTRA) Chemical and Biological Technologies Department in its role as the Joint Science and Technology Office (JSTO) for Chemical and Biological Defense, an integral component of the Chemical and Biological Defense Program, invested with researchers at the Massachusetts Institute of Technology Lincoln Laboratory (MIT-LL) and the U.S. Army Combat Capabilities Development Command–Chemical Biological Center (DEVCOM CBC) to develop a self-contained, throwable, and reusable prototype called TOSSIT—the Tactical Optical Spherical Sensor for Interrogating Threats. TOSSIT can be used by the Joint Force as a remote point vapor sensor to provide early warning of a chemical threat.
To use the TOSSIT, warfighters simply power up the device and the sensor automatically connects to a handheld readout device (currently a smartphone application) using a secure wireless connection. The application lets the end user see the alarm state of the device at any time. In a typical site-assessment mission, the user rolls or tosses the device into a room, and TOSSIT quickly lets the user know if there were chemical threats present by giving out a warning. In addition to chemical threats, the developers have a function that alerts the user to the oxygen level of the enclosed space, as well as the presence of explosive fuel vapors that would make it unsafe to fire a weapon.
The TOSSIT sensor features a removable and disposable card containing an array of multiple colorimetric dyes, each specific to a different chemical threat or class of threats, and a camera readout to quantify the color change, with shielding from varying ambient lighting conditions. In practice, multiple dyes target the same threat to confirm detection and minimize the chance of false alarms. The dye indicators used to detect the threats come from a menu of traditional indicator dyes, custom-designed and synthesized dyes, and the Self-Indicating Colorimetric inorganic materials pioneered by researchers at DEVCOM CBC.
An onboard blower pulls ambient air into the system that moves toward a sampling chamber where it interacts with the colorimetric dyes. An internal imaging device observes the dye card illuminated by multiple white light or ultraviolet light emitting diodes acting as a camera flash. The onboard electronics determine the color of each spot in the dye array and compare it to a baseline value. Color changes outside a prescribed window for each dye trigger an alarm. Which dye displays a color change upon exposure to the ambient sample determines the identity of the chemical being detected.
Prior iterations of sensor and colorimetric indicators have been tested against toxic industrial chemical vapors in the lab and have undergone surety testing against select chemical agent threats. These data help researchers test the performance of the system as well as set realistic alarm levels to help minimize potential false alarms in the field.
The further development of low-size, -weight, -power, and -cost sensors that provide an early warning to chemical threats is an important mission area for DTRA JSTO to reduce the CB risks to the Joint Force in the field. Success in developing TOSSIT may open its use in other mission areas such as perimeter defense using the sensor in unobtrusive packaging as well as wide-area deployment by aerial assets.
POC: Tyler Miller, tyler.c.miller23.civ@mail.mil
Courtesy Story
Defense Threat Reduction Agency’s Chemical and Biological Technologies Department