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Skin Attached Traumatic Brain Injury Sensing System


OBJECTIVE: Proposals are sought to develop a flexible, conformal, skin-attach electronic platform for wearable sensors, with the goal of attaching sensors anywhere on the body to monitor the environment and/or physiological parameters of the wearer. The platform should include microprocessor with simple data analysis algorithms, data storage, power supply, and wireless Radio Frequency communication, along with a method for incorporating digital sensors both mechanically and electronically into the system. DESCRIPTION: Over the past 5 years the Army and the Department of Defense have been developing sensor systems for detection of impact and blast events with potential for causing traumatic brain injury (TBI). Most of these systems are helmet-mounted, whereas the small adhesive patch targeted here would allow attachment to the skin, which is more closely coupled to the environment that the skull and brain experience, while also helping to minimize head-supported mass. Wearable sensors, especially skin-attached sensors with the flexible/conformal requirements therein, are still in their infancy [1], with most still larger than 100 square millimeters [2]. This research topic entails the design of the electronics necessary for monitoring an array of arbitrary digital sensors; incorporating these electronics into a flexible, stretchable, conformal substrate (references [3] and [4] are provided by way of example only and are not intended to limit the materials or methods used); and development of a method for transferring or assembling microelectromechanical systems (MEMS) sensors to the flexible substrate that is amenable to volume manufacturing. Methods for attachment or transfer of the MEMS sensors to the substrate must retain the inherent substrate flexibility. The resulting system should be completely self-contained, including power supply, some basic data processing/analysis, real-time clock, data storage for at least 100 time-stamped magnitude/duration events, and radio-frequency (RF) communications for programming and data retrieval. Battery and individual electronic components (microprocessor/radio/memory) may be COTS, but size and mass are at a premium to promote maximum flexibility and minimum footprint. The substrate should be both flexible and stretchable to allow for attachment on various three-dimensional body parts. The overall system size should be no larger than a standard band-aid (approximately 1.9 x 5.75 cm), no thicker than 4mm at the widest point, weigh less than 3 grams, and should be attachable via standard medical adhesives. Desired minimum radius of curvature is 0.6 cm to accommodate wrapping sensors around thinner body parts such as the nose or fingers. The system should last at least one month while continuously monitoring on a single battery charge, with at least 5 data collection/transmission events covering a minimum of 50 meters. Expected maximum current draw is for the wireless data transmission, approximately 20mA. Sensor power draw is expected to be less than 100uA during an event. Data sampling during an event should be at least 20 kilohertz or equivalent, triggered by an interrupt from the sensor. The system should be awake and recording data in less than 20 microseconds. The sensors (to be chosen by ARL) will be provided in standard surface-mountable leadless chip form factor. Provisions for at least 15 digital outputs from the sensor should be provided for flexibility in accomodating arrays of sensors in a single package. PHASE I: During phase I the performer will design the electronic data collection, storage, and transmission system and select components, and demonstrate feasibility of proposed method for assembling sensors onto flexible substrates. A full analysis of power consumption and anticipated battery life is expected during this phase. Phase I deliverable shall be a final report to include details of the system-level design and architecture, demonstration of the assembly of the sensor and other components onto the flexible substrate, and calculated/anticipated mechanical (radius of curvature limits for attachment, strain sensitivity, etc.) and electrical (data sampling rates, transmission distance, battery lifetime, etc) performance. PHASE II: During phase II, the implementation of the design from Phase I will be conducted. The electronics will be prototyped in the final flexible and conformal form factor to correctly interface with the digital MEMS sensors selected by ARL to interpret, store and transmit the data to a nearby laptop or handheld device. The system should be evaluated for mechanical (radius of curvature limits for attachment point, strain sensitivity, etc.) and electrical (data sampling rates, transmission distance, etc) performance. The sensors will be transferred/assembled onto the flexible substrates by the performer. Finally the performer will evaluate system performance and survivability with impact tests on a dummy headform. The phase II deliverables shall include a final report detailing the overall system design and performance. In addition, the contractor shall deliver twelve (12) prototype flexible, conformal assemblies with all of the electronics and sensors integrated thereon. PHASE III: In phase III, follow-on activities are expected to be aggressively pursued by the offeror, namely in seeking opportunities to commercialize the skin-attach sensing system developed during phases I and II. Potential military applications include impact/blast personal monitoring systems for Traumatic Brain Injury early warning. Commercial applications of the conformal wireless sensor assembly include TBI sensing for sports such as football, hockey, soccer, rugby, and others all the way from junior leagues to professional levels. There is considerable interest throughout the athletic community in better tools to immediately determine severity of a hit or fall and the need for medical attention. It is also expected that the TBI sensor will not be the only application of the underlying technology for instance, band-aid form factor heart rate or perspiration sensors would also have wide application in athletics. The electronics would ideally be developed in a sensor-agnostic way so that other sensors can be easily integrated into the system with no hardware changes and minimal software changes. REFERENCES: [1] E. McAdams, A. Krupaviciute, C. Gehin, E. Grenier, B. Massot, A. Dittmar, P. Rubel, J. Fayn,"Wearable Sensor Systems: The Challenges,"IEEE EMBS, Boston, MA, Aug. 30-Sept. 3, 2011, pp. 3648-3651. [2] J. Yoo, L. Yan, S. Lee, Y. Kim, and H.-J. Yoo,"A 5.2mW Self-Configured Wearable Body Sensor Network Controller and a 12uW Wirelessly Powered Sensor for a Continuous Health Monitoring System,"IEEE Journal of Solid-State Circuits 45, pp. 178-188. [3] J. A. Rogers, T. Someya, and Y. Huang,"Materials and Mechanics for Stretchable Electronics,"Science 327 pp. 1603-1607 (2010). [4] K. J. Lee et al,"Large-Area, Selective Transfer of Microstructured Silicon: A Printing- Based Approach to High-Performance Thin-Film Transistors Supported on Flexible Substrates,"Advanced Materials 17, pp. 2332-2336 (2005).
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