|Acquisition Program: ||JPEO Chemical and Biological Defense|| Objective: ||Develop a sensing element that exhibits an electronic signal upon detection of a chemical or biological stimulus for incorporation into a textile-based conductive core fiber worn on the uniform in a patch-type application.
|| Description: ||The modern Warfighter lacks the ability to sense the existence of threats beyond the traditional sights and smells on the battlefield without the help of additional bulky equipment. The proposed research will provide the Warfighter with electrochemical signals from a chemical/biological sensing patch on the Warfighter’s uniform to greatly improve the Warfighter response time, survivability and lethality. Conventional high-sensitivity sensors are often too heavy and too expensive to be carried by all dismounted Warfighters. Incorporation of sensitive, low-power sensor elements into a fiber/textile material uniform patch capable of transmitting electronic signals through to a conductive core/channel to a lightweight readout device would allow each dismounted Warfighter the ability to identify and avoid potential battlefield threats.
Recent research has focused upon chemresistors and chemFETs as sensors for various chemical threats with varying degrees of success. Inorganic semiconductors, flexible and light conductive polymers, and specially treated carbon nanotubes are examples of designs that will be considered in the proposed research. It is envisioned that a single chemical chemresistor sensing element would be placed into a suitable high-throughput polymeric fiber spinning process to create a strand of one-time use indicator fiber. Additionally developed single chemical chemresistor sensing element fibers could then be bundled into a wearable patch to provide multi-chemical threat detection/specificity and result in substantial reductions in both cost and weight. To produce a sensor system, the sensing elements must be developed that can rapidly change their electronic properties upon exposure to a battlefield threat such as a toxic industrial chemical at sensitivity levels below the exposure threshold to the Warfighter, and transmit a signal to a conductive core fiber to provide an alert to the Warfighter.
The conductive core fiber research will attempt to maximize the available surface area for the chemresistor sensor while keeping the overall fiber diameter to a maximum of 100 microns. Appropriate fiber and chemresistor combinations will also be evaluated to ensure that signal conductivity in conditions are capable of spanning temperature ranges of –60 degrees F to +160 degrees F and humidity ranges of 0% to 100% Relative Humidity in order to simulate operating conditions encountered by the Warfighter. Additionally, the sensing molecule will be designed to exhibit sufficient mechanical robustness when incorporated into the conductive fiber of a uniform patch to survive the demands of textile operations and abrasion resistance. Specifically, as a uniform patch application, the conductive core fiber and chemresistor combination would not be required to pass laundering tests, but should be able to operate in situations such as rainstorms and other climatological battlefield conditions.
The fiber plus sensor element will be designed to detect Army relevant threat(s) and elicit a response to a challenge chemical in a reasonable timeframe to warn the Warfighter of the impending threat. The chemresistor design should also be capable of good selectivity to avoid triggering false positives. The chemresistor will respond to threats in the vapor phase (i.e. gas/vapor in the surrounding air). Limits of detectability are expected to vary with different chemical species; however, the chemresistor must elicit a positive response to a challenge at limits below levels considered a threat to the Warfighter.
|| ||PHASE I: Identify candidate chemresistor(s) or similar type sensor for detecting a CB relevant threat. Demonstrate incorporation of sensing element to a conductive fiber platform and electronic connection to fiber conduction method and show sensitivity to a laboratory threat environment. Mitigate risk by identifying and addressing the most challenging technical barriers in order to establish viability of the technology or process.
|| ||PHASE II: Refine the chemresistor sensor to reduce possibilities of false positives and fabricate advanced prototypes that meet the stated requirements. Reduce size/power requirements for sensor output detection and address manufacturability issues related to full-scale production. Provide prototype system for government testing and initial Warfighter acceptance testing. The prototype fiber and sensor combination should show a good robustness to mechanical stress and abrasion resistance.
|| ||PHASE III: Further research and development during Phase III efforts will be directed towards refining a final deployable design, incorporating design modifications based on results from tests conducted during Phase II, and improving engineering/form-factors and manufacturability designs to meet U.S. Army CONOPS and end-user requirements. The initial military application for this technology will be a sensing fiber incorporated into the Warfighter uniform, either as an integral part of the textile or as a patch. The transition from research to operational capability will most likely result from a partnership or licensing agreement with a manufacturer of textile fibers and subsequent incorporation of the sensing fiber into a fabric. The ability to sense dangerous threats to the human body would not only benefit the Warfighter, but also have a significant relevance to first-responder type civilians (police, firefighter, and EMS). Potential for use in civilian markets would depend upon the specific chemical/biological threats the sensor is sensitive to, although it can be envisioned that enclosed-space workers such as underground mining, plant operators and others would likely find use for more portable hazardous gas (hydrogen sulfide, methane, carbon monoxide) sensors.
|| References: ||
1. The Present State of Amperometric Nanowire Sensors for Chemical and Biological Detection, ARL-TR-3962 Oct. 2006
2. Covington, J.A.; Gardner, J.W.; Bartlett, P.N.; Toh, C-S. Conductive polymer gate FET devices for vapour sensing. IEE Proceeding-Circuits Devices and Systems, 151 (4), 326-334, 2004
3. Crone, B.; Dodabalapur, A.; Gelperin, A.; Torsie, L.; Katz, H.E.; Lovinger, A.J.; Bao, Z. Electronic sensing of vapors with organic transistors. Applied Physics Letters, 78 (15), 2229-2231, 2001|
|Keywords: ||textile, chemresistor, chemFET, conductive polymer, sensing fiber, conductive fiber|