{"206881":{"#nid":"206881","#data":{"type":"news","title":"Wireless \u0022Smart Skin\u0022 Sensors Could Provide Remote Monitoring of Infrastructure","body":[{"value":"\u003Cp\u003EMajor bridge failures in recent years have focused attention on the need to monitor America\u2019s highway bridges and other infrastructure. As thousands of bridges, parking garages and other structures age, improved methods for detecting deterioration could save lives and prevent economic disruption.\u003C\/p\u003E\u003Cp\u003EResearchers at the Georgia Institute of Technology are developing a novel technology that would facilitate close monitoring of structures for strain, stress and early formation of cracks. Their approach uses wireless sensors that are low cost, require no power, can be implemented on tough yet flexible polymer substrates, and can identify structural problems at a very early stage. The only electronic component in the sensor is an inexpensive radio-frequency identification (RFID) chip.\u003C\/p\u003E\u003Cp\u003EMoreover, these sensor designs can be inkjet-printed on various substrates, using methods that optimize them for operation at radio frequency. The result would be low-cost, weather-resistant devices that could be affixed by the thousands to various kinds of structures.\u003C\/p\u003E\u003Cp\u003E\u0022For many engineering structures, one of the most dangerous problems is the initiation of stress concentration and cracking, which is caused by overloading or inadequate design and can lead to collapse \u2013 as in the case of the I-35W bridge failure in Minneapolis in 2007,\u0022 said Yang Wang, an assistant professor in the Georgia Tech School of Civil and Environmental Engineering. \u0022Placing a \u0027smart skin\u0027 of sensors on structural members, especially on certain high-stress hot spots that have been pinpointed by structural analysis, could provide early notification of potential trouble.\u0022\u003C\/p\u003E\u003Cp\u003EWang is collaborating with a team that includes professor Manos M. Tentzeris of the School of Electrical and Computer Engineering, and Roberto Leon, a former Georgia Tech professor who recently moved to Virginia Tech. The work is supported by the Federal Highway Administration.\u003C\/p\u003E\u003Cp\u003EThis research was recently reported in \u003Cem\u003EIEEE Antennas and Wireless Propagation Letters\u003C\/em\u003E, Volume 11, 2012, and \u003Cem\u003EInternational Journal of Smart and Nano Materials\u003C\/em\u003E, Volume 2, 2011. Parts of this research were also presented at ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS) and several other conferences.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EAntennas as Sensors\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EThe Georgia Tech research team is focusing on wireless sensor designs that are passive, which means they need no power source. Instead, these devices respond to radio-frequency signals sent from a central reader or hub. One such reader can interrogate multiple sensors, querying them on their status at frequent intervals.\u003C\/p\u003E\u003Cp\u003EThe researchers\u0027 approach utilizes a small antenna mounted on a substrate and tuned to a specific radio frequency. This technique enables the antenna itself to function as a stress sensor.\u003C\/p\u003E\u003Cp\u003EAs long as the structural member to which the antenna\/sensor is affixed remains entirely stable, its frequency stays the same. But even a slight deformation in the structure also deforms the antenna and alters its frequency response. The reader can detect that change at once, initiating a warning months or years before an actual collapse.\u003C\/p\u003E\u003Cp\u003E\u0022A key benefit of this technology is that it\u0027s completely wireless,\u0022 Wang said. \u0022It doesn\u0027t require a battery, and you don\u0027t have to climb around on bridges running long connecting cables.\u0022\u003C\/p\u003E\u003Cp\u003EThe research team has developed a prototype strain\/crack sensor that has been successfully tested in the laboratory, Wang said. The simple device consists of a small piece of copper mounted on a polymer substrate, plus a 10-cent 1mm by 1mm RFID chip. The chip is used to distinguish each individual sensing unit from others. The simple sensor architecture allows it to be made at very low cost and to potentially be deployed in large quantities on any bridge.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EInkjet-Printed Circuits\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EMore sophisticated designs are in the works. Tentzeris\u0027 team is tackling an approach that produces strain sensors using different applications of inkjet printing technology.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EOne such design uses a silver-nanoparticle-based ink that is applied to a flexible or semi-flexible substrate, said Rushi Vyas, a Ph.D. student working with Tentzeris. The ink lays down a structure that can change properties in response to strain.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EA second approach involves the use of inkjet-printed carbon-nanotube-based structures, Vyas said. In this case, the nanotubes themselves produce an altered response when subjected to deformation.\u003C\/p\u003E\u003Cp\u003EIn laboratory testing, the team\u0027s prototype sensors have demonstrated high sensitivity in response to even slight changes in metal structures, Wang said. The sensors have been able to reliably detect a degree of deformation change as low as tens of microstrains (one microstrain equals 0.0001 percent, or 1 part per million), and they can continuously monitor stress accumulation until the metal develops a severe crack.\u003C\/p\u003E\u003Cp\u003EOne issue still being addressed is the capacity of the passive sensor to respond to a reader. A reader transmits a radio-frequency beam to a sensor, which utilizes that received energy to reflect a signal back to the reader.\u003C\/p\u003E\u003Cp\u003EBut this technique can be rather inefficient, Vyas said. A signal from a reader might travel 50 feet, yet the sensor\u0027s response might only travel back 10 feet. One issue is that readers are limited by FCC regulations, which govern how much power can be transmitted to the sensor.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EIncreasing the Power\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EWhat\u0027s needed are ways to supply a sensor with a power source that would increase the range of the response signal. Batteries are not preferred because they can be undependable and require periodic replacement.\u003C\/p\u003E\u003Cp\u003EOne candidate solution \u2013 in addition to solar-energy and vibration-energy harvesting \u2013 is scavenged energy, Tentzeris said. A Georgia Tech team that includes Tentzeris and Vyas is researching ways to gather power from ambient or electromagnetic energy in the air, such as television, radio, radar or other manmade signals found in Earth\u0027s lower atmosphere.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EScavenging experiments utilizing TV bands have already yielded power amounting to hundreds of microwatts. Multi-band systems are expected to generate one milliwatt or more \u2013 enough to operate some small electronic devices such as low-power wireless sensors.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003ETentzeris noted that smart-skin technology may soon help to enable a broad range of applications. These could include not only real-time stress monitoring in bridges, factories and buildings, but also new and extremely lightweight aircraft with self-sensing\/self-diagnostic capabilities, and battery-free methods for monitoring structures after major disasters such as earthquakes or hurricanes.\u003C\/p\u003E\u003Cp\u003E\u0022The wireless strain sensor could prove to be an effective, low-cost and easy-to-scale solution to a very important need,\u0022 Tentzeris said. \u0022A simple device \u2013 consisting of an antenna, an inexpensive RFID chip and some power-boosting technology \u2013 could quietly monitor at-risk structures for many years, and then send back a real-time warning if there\u0027s suddenly a problem.\u0022\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EResearch News\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EGeorgia Institute of Technology\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003E177 North Avenue\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EAtlanta, Georgia 30332-0181 USA\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cbr \/\u003E\u003Cstrong\u003EMedia Relations Contact\u003C\/strong\u003E: John Toon (404-894-6986)(\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E).\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: Rick Robinson\u003Cbr \/\u003E\u003Cbr \/\u003E\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EResearchers are developing a novel technology that would facilitate close monitoring of bridges, parking decks and other structures for early signs of strain, stress and formation of cracks. Their approach uses wireless sensors that are low cost, require no power, and can be implemented on tough yet flexible polymer substrates.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"A new technology would facilitate close monitoring of bridges and other structures for early signs of strain."}],"uid":"27303","created_gmt":"2013-04-16 09:33:31","changed_gmt":"2016-10-08 03:14:04","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2013-04-16T00:00:00-04:00","iso_date":"2013-04-16T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"206851":{"id":"206851","type":"image","title":"Strain sensing for infrastructure3","body":null,"created":"1449179988","gmt_created":"2015-12-03 21:59:48","changed":"1475894864","gmt_changed":"2016-10-08 02:47:44","alt":"Strain sensing for 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specimen","file":{"fid":"196758","name":"120515br238s.jpg","image_path":"\/sites\/default\/files\/images\/120515br238s_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/120515br238s_0.jpg","mime":"image\/jpeg","size":1143958,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/120515br238s_0.jpg?itok=zsCnU_bI"}}},"media_ids":["206851","206841","206821","206861","206871"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"145","name":"Engineering"}],"keywords":[{"id":"64101","name":"bridges"},{"id":"1897","name":"Civil Engineering"},{"id":"172","name":"infrastructure"},{"id":"167864","name":"School of Civil and Environmental Engineering"},{"id":"169489","name":"strain"},{"id":"171268","name":"strain sensor"},{"id":"64111","name":"Yang Wang"}],"core_research_areas":[{"id":"39451","name":"Electronics and Nanotechnology"},{"id":"39531","name":"Energy and Sustainable 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