Multi-substrate passive colorimetric sensors for detecting toxic industrial chemicals and chemical warfare agents
Inventors
Beshay, Manal • Jensen, Janet L. • Cress, James M.
Assignees
Intelligent Optical Systems Inc • United States Department of the Army
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Publication Number
US-11255794-B1
Publication Date
2022-02-22
Expiration Date
2039-02-22
Abstract
Disclosed are systems and methods for the robust passive detection of airborne toxins using a colorimetric sensor coating onto a optically transparent substrate. In certain embodiments, the substrate is affixed to an adhesive material (tape). In certain embodiments, the sensor and substrate are transparent. In various embodiments, multiple sensors are coated onto selected substrate for the simultaneous detection of multiple toxins. In various embodiments, the sensed or detected toxins include a number of chemical warfare agents and toxic industrial chemicals. In various implementations, the tape is affixed to a remote surface, which may be visually monitored by a camera directly by focusing the camera on the tape or may be affixed to a camera lens by an adhesive backing, such that colorimetric sensor changes may be observed through the lens itself. Sensor claddings consist of optical grade polymers immobilized with colorimetric and/or fluorescent indicators that undergo optical changes upon exposure to their target analyte. Typical substrate cross-linked polymers are urethane acrylate polymer based, co-polymerized with silicone backbone such as dimethyl siloxane, which in general is chemically inert, yet leaves the polymer with the large free-volume necessary for rapid target diffusion. The polymer is cured after immobilization with target indicator mixture, and simultaneously cross-linked by UV light or heat.
Core Innovation
Disclosed are systems and methods for the robust passive detection of airborne toxins using a colorimetric sensor coating onto an optically transparent substrate. In certain embodiments, the substrate is affixed to adhesive material such as tape, and both the sensor and substrate may be transparent. Multiple sensors can be coated onto a selected substrate for simultaneous detection of multiple toxins including chemical warfare agents (CWAs) and toxic industrial chemicals (TICs). The tape can be affixed to remote surfaces and visually monitored by cameras, for example by placing the tape on a camera lens so that colorimetric changes are observed through the lens.
The sensor claddings consist of optical grade polymers immobilized with colorimetric and/or fluorescent indicators that undergo optical changes upon exposure to their target analyte. Cross-linked polymers are typically urethane acrylate polymer based and co-polymerized with a chemically inert silicone backbone such as dimethyl siloxane, which provides large free volume necessary for rapid diffusion of target toxins. The polymers are cured after immobilization with target indicator mixtures via UV light or heat to achieve stable, durable sensor coatings.
The problem being addressed arises from the need for advanced detection techniques for chemical and biological threats to military personnel and civilians, especially owing to dispersed chemical weapons stockpiles, terrorist threats, and limitations of existing detection technologies. Available colorimetric detection papers like M8 and M9 have poor stability and specificity and are generally used directly by personnel. Electronic noses, while sophisticated, require power and complex components unsuitable for passive integration into unmanned autonomous systems (UAS). There is a critical need to provide multifunctional, interoperable, near-real-time or real-time remote detection solutions that are stable and adaptable under various environmental conditions.
Claims Coverage
The patent contains two independent claims: one for a system for passive detection of airborne toxins using colorimetric indicators on a polymer substrate, and one for a method for passive detection using similarly constructed sensors. The main inventive features encompass the colorimetric indicator integration with a transparent polymer substrate affixed to a transparent window or lens, enabling passive detection of chemical warfare agents or toxic industrial chemicals.
Colorimetric indicator on transparent polymer substrate for toxin detection
A system comprising at least one colorimetric indicator which changes color upon exposure to airborne toxins, clad and immobilized on an optical grade transparent polymer substrate that includes a cross-linked urethane acrylate primary polymer combined with a chemically inert silicon-based co-polymer.
Affixing sensor substrate to transparent window or lens for optical detection
The transparent polymer substrate is affixed to an environment-facing surface of a transparent window or lens and positioned between the optical detector and environment to allow a line of sight through the polymer substrate such that color changes are observable by the optical detector indicating the presence of target airborne toxins.
Use of hydrolyzing agent and metal salt complexed indicator dye
The colorimetric indicator comprises an indicator dye complexed with a metal salt and optionally mixed with a hydrolyzing agent to improve detection, especially for chemical warfare agents like sarin and soman.
Application of free volume enhancer additives to polymer substrate
The polymer substrate may be treated with a free volume enhancer additive, specifically poly-styrene-sulfonate derivatives such as poly-styrene-sulfonate-trisilanol-isooctyl substituted, to increase porosity and enhance gas diffusion and sensor response speed.
Method for passive detection using cross-linked transparent polymer substrate and optical monitoring
A method involving exposing a colorimetric indicator immobilized in a UV and heat cured transparent polymer substrate to an environment, affixing the substrate to an environment-facing transparent window or lens, and discerning color changes through the transparent substrate by an optical detector indicative of airborne chemical warfare agents or toxic industrial chemicals.
The claims cover systems and methods for passive detection of airborne toxins using colorimetric indicators immobilized on specifically cross-linked transparent polymer substrates affixed to transparent windows or lenses for optical detection, including enhancements with hydrolyzing agents and free volume enhancers to improve sensitivity and response.
Stated Advantages
Provides a robust, passive chemical detection system suitable for integration with unmanned autonomous systems (UAS) without requiring power, complex hardware, or software interfaces.
Improves stability and specificity over existing detection papers like M8 and M9 through polymer claddings and tailored indicator chemistries.
Enables near real-time monitoring under a wide range of environmental conditions, including low humidity, temperature, and airborne contaminants.
Supports multiplexed sensing of multiple chemical warfare agents and toxic industrial chemicals simultaneously with high selectivity and low cross-reactivity.
Allows passive visual or optoelectronic monitoring via sensors affixed to camera lenses or windows facilitating remote or automated detection.
Documented Applications
Affixing sensor tapes with colorimetric indicators onto camera lenses of unmanned aerial systems (UAS) or unmanned ground systems (UGS) for remote sensing of chemical warfare agents and toxic industrial chemicals.
Use as a portable field detection kit for military personnel including individual test strips that can be visually inspected or inserted into opto-electronic readers for verification.
Integration with unmanned autonomous systems for chemical reconnaissance, intelligence, surveillance, and reconnaissance missions.
Coating various substrate materials such as glass, quartz, wood, metal, paper, and Styrofoam for stable chemical detection on different surfaces.
Implementation as armband chemical warfare agent colorimetric sensors for first responders and environmental monitoring applications.
Multiplexed sensor arrays for detecting multiple toxic industrial chemicals and chemical warfare agents in vapor or aerosol form with optical readout.
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