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Liquid Crystal-based Sensors for Detection of Airborne Toxic Chemicals for Integration with Unmanned Robotic Systems

Description:

OBJECTIVE: Development of rugged light-weight liquid crystal-based chemical sensors for integration with unmanned vehicles. DESCRIPTION: Unmanned vehicles (UMVs) that allow assessment of threat before entering an unknown environment are becoming an integral part of critical missions to ensure personal safety. These remotely controlled robotic devices are typically equipped with multiple infrared cameras and microphones to provide a real-time audio-visual signal from an otherwise unknown environment. Recent advances in new materials, efficient device design, and improved data transfer and processing capabilities have led to the development of small lightweight throwable robots that can be deployed remotely inside a building to provide situational awareness. Besides audio-visual capabilities, the need for onboard sensors to detect presence of potentially lethal or other important chemical agents has long been recognized. Large UMVs can carry large instruments capable of collecting air samples and performing in-situ spectral analysis, but small, recently developed throwable robots do not have integrated chemical sensors primarily due to the absence of a sensing technology that can provide small, lightweight, low-power sensors that can withstand the mechanical impacts during deployment. Chemical sensors based on existing technologies are either too bulky, require high power to operate or they cannot withstand the mechanical shock during deployment. There exists, therefore, an unmet need for small, low-cost rugged sensor technologies that can be integrated into throwable robots to empower them with the third sense (i.e. smell). A sensor that can be integrated with these UMVs will save lives during critical missions by providing real-time information to the operator about the life-threatening chemical environments before entering. These sensors for toxic chemicals should be lightweight and should allow seamless interfacing with the existing wireless data communication system in UMVs. Development of these new sensor technologies requires the design of advanced materials systems that exhibit large changes in physical properties in response to relevant concentrations of targeted toxic chemicals so as to avoid the need for bulky and complex instruments and minimize device power consumption. Liquid crystal (LC)-based materials systems have potential to address this unmet need by enabling development of a robust, light-weight, sensitive, low power sensor platform. This innovative technology relies on the use of liquid crystalline materials, supported on chemically functionalized surfaces, that undergoes an ordering transition upon exposure to targeted analytes. Together, the use of LC materials and competitive interactions at the molecular scale form the basis of a sensing technology that provides simplicity and selectivity not offered by existing sensing technologies. The sensors can be interrogated optically (by using polarized light) or electronically (by measuring change in capacitance) to yield an unambiguous and quantifiable dose dependent response. By tailoring the physicochemical properties of the chemically functionalized surfaces, a technology can be developed to distinguish classes of chemical agents (e.g. blister vs. nerve agents) and also compounds within a given class (e.g. GB vs. VX nerve agents). The LC-based sensing technology is capable of detection of various gases of relevance to defense and security (nerve agents) and occupational hygiene (toxic chemicals) applications. Optimization of the physicochemical properties of the surfaces will allow detection in the ppb levels in seconds. The technology is based on materials and processes currently employed in well-established LC display technology and therefore it is amenable to high-throughput manufacturing. The technology can be realized in a variety of formats and packaging for surveillance and monitoring of the chemical environment that will allow easy integration with UMVs such as throwable robots. PHASE I: In Phase I, the LC-based technology should demonstrate detection of at least 4 different chemicals of different classes within seconds and at 100 ppb limits of detection or less. Possible targets include but are not limited to toxic industrial chemicals, chemical agent simulants, and pesticides. PHASE II: Phase II should continue sensor chemistry development and optimization, and demonstrate detection of at least 7 different chemicals from different classes within seconds and at less than 100 ppb limits of detection. The sensor technology should be able to distinguish classes of chemical agents as well as compounds within the same class. In addition to a sensitive detection surface with rapid response time and non-responsiveness to common interferents, a sensor for integration with the UMVs must be sufficiently rugged to withstand fluctuations in the environmental conditions including temperature and relative humidity variations. Once the optimal chemistry and LC materials are identified, an electrical detection method should be developed. To demonstrate integration with throwable robots, a prototype sensor sub-system should be designed, fabricated, tested, and demonstrated in a realistic environment mimicking operational conditions. PHASE III DUAL USE APPLICATIONS: This technology has a broad range of potential civilian and military applications. The sensor platform developed for detection of chemical warfare agents and toxic industrial chemicals for military applications can readily be adapted for detection of a range of toxic chemicals for first responders. REFERENCES 1. http://www.reconrobotics.com/products/ 2. http://www.qinetiq-na.com/products/unmanned-systems/talon/ 3. Shah, R.R. and N.L. Abbott, Principles for measurement of chemical exposure based on recognition-driven anchoring transitions in liquid crystals. Science 293(5533): 1296-1299 (2001). 4. Cadwell KD et al., Detection of organophosphorous nerve agents using liquid crystals supported on chemically functionalized surfaces. Sensors and Actuators B 128 9198 (2007).
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