MEMS: Micro Electro-Mechanical Systems for Wirelessly Monitoring the Health of Transportation Related Structures

Wireless MEMS miniaturization is about to overtake the discipline of field performance and structural health monitoring, and ITI's REG has the assets to continue to be a presence at the forefront of this new wave with limited personnel. ITI is among leaders in MEMS wireless application civil engineering. Past accomplishments include development of 1) a system for surveillance of vibratory phenomena with no minimal power drain (Lucid Dreaming), 2) system for monitoring crack extension, and 3) a system for monitoring long term crack extension. This year's work involves winding down and cessation of this work under this research focus. MEMS work is better continued with direct control and management by REG personnel. Track 3, commercialization of the crack extension would be of great benefit to all structural health monitoring endeavors, especially bridge inspection. It is important that Northwestern and ITI remain in the forefront of the use of wireless MEMS technology. Despite cessation of ACM related MEMS work it is hoped that the REG will continue to develop crack extension technology. These MEMS (Micro Electro-Mechanical Systems) devices are being developed for the defense and health care industries, and this development can be leveraged for structural health monitoring. Firms such as MicroStrain, Dust Inc., Crossbow, and Applied MEMS are selling devices that are approximately 1/10th size of currently available "small" digital instruments. There are plans and preliminary VLSI designs to reduce the size of these devices another two orders of magnitude in the near future. field testing of 1) a low sample rate, long-term (level 1) wireless ACM system, and 2) a multihoping low sample rate system with a battery life of over 6 months. In addition a zero powerconsumption dynamic motion trigger has been developed. This year's work involves development and field deployment of a system to measure the long term crack behavior of cracks in steel bridges. While focused on extension of cracks in steel bridges, the technology will can be employed across rock joints to monitor the long term effects of blasting vibration on rock mass stability during blasting. The system is currently undergoing field qualification testing at the Sycamore, IL test house. It is important that Northwestern and ITI remain in the forefront of the use of wireless MEMS technology, and this proposal is for the continuation of the modest investments to develop in-house expertise in this area. These devices present an opportunity to miniaturize instrumentation for measurement of strain, motion, and crack displacement, and a host of other measurement types. Their wireless nature grants them the potential to lower the cost of measuring relative motion and displacement of critical facilities and geologies, as well as propagation velocity, and provide an order of magnitude more points of measurement, etc. MEMS devices consume little power when acquiring single data point information atpredefined times, but require more power to sense continuously and to transmit large data sets. Communication is accomplished by transmitting only a short distance with a trail of devices that eventually leads to the central data collection unit that then "back casts" theinformation over cellular or hard lines of communication. These MEMS (Micro Electro-Mechanical Systems) devices are being developed for the defense and health care industries, and this development can be leveraged for structural health monitoring. Firms such as MicroStrain, Dust Inc., Crossbow, and Applied MEMS are selling devices that are approximately 1/10th size of currently available "small" digital instruments. There are plans and preliminary VLSI designs to reduce the size of these devices another two orders of magnitude in the near future.