{"73048":{"#nid":"73048","#data":{"type":"news","title":"Nanogenerator to Power Nanoscale Devices","body":[{"value":"\u003Cp\u003EResearchers have developed a new technique for powering nanometer-scale devices without the need for bulky energy sources such as batteries.  \n\u003C\/p\u003E\n\u003Cp\u003EBy converting mechanical energy from body movement, muscle stretching or water flow into electricity, these \u0027nanogenerators\u0027 could make possible a new class of self-powered implantable medical devices, sensors and portable electronics.\n\u003C\/p\u003E\n\u003Cp\u003EDescribed in the April 14th issue of the journal \u003Cem\u003EScience\u003C\/em\u003E, the nanogenerators produce current by bending and then releasing zinc oxide nanowires - which are both piezoelectric and semiconducting.  The research was sponsored by the National Science Foundation (NSF), the NASA Vehicle Systems Program and the Defense Advanced Research Projects Agency (DARPA).\n\u003C\/p\u003E\n\u003Cp\u003E\u0022There is a lot of mechanical energy available in our environment,\u0022 said Zhong Lin Wang, a Regents Professor in the School of Materials Science and Engineering at the Georgia Institute of Technology.  \u0022Our nanogenerators can convert this mechanical energy to electrical energy.  This could potentially open up a lot of possibilities for the future of nanotechnology.\u0022\n\u003C\/p\u003E\n\u003Cp\u003ENanotechnology researchers have proposed and developed a broad range of nanoscale devices, but their use has been limited by the sources of energy available to power them.  Conventional batteries make the nanoscale systems too large, and the toxic contents of batteries limit their use in the body.  Other potential power sources also suffer from significant drawbacks.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022We can build nanodevices that are very small, but if the complete integrated system must include a large power source, that defeats the purpose,\u0022 added Wang, who also holds affiliated faculty positions at Peking University and the National Center for Nanoscience and Technology of China.  \n\u003C\/p\u003E\n\u003Cp\u003EThe nanogenerators developed by Wang and graduate student Jinhui Song use the very small piezoelectric discharges created when zinc oxide nanowires are bent and then released.  By building interconnected arrays containing millions of such wires, Wang believes he can produce enough current to power nanoscale devices.\n\u003C\/p\u003E\n\u003Cp\u003ETo study the effect, the researchers grew arrays of zinc oxide nanowires, then used an atomic-force microscope tip to deflect individual wires.  As a wire was contacted and deflected by the tip, stretching on one side of the structure and compression on the other side created a charge separation - positive on the stretched side and negative on the compressed side - due to the piezoelectric effect.  \n\u003C\/p\u003E\n\u003Cp\u003EThe charges were preserved in the nanowire because a Schottky barrier was formed between the AFM tip and the nanowire.  The coupling between semiconducting and piezoelectric properties resulted in the charging and discharging process when the tip scanned across the nanowire, Wang explained.\n\u003C\/p\u003E\n\u003Cp\u003EWhen the tip lost contact with the wire, the strain was released - and the researchers measured an electrical current.  After the strain release, the nanowire vibrated through many cycles, but the electrical discharge was measured only at the instant when the strain was released.\n\u003C\/p\u003E\n\u003Cp\u003ETo rule out other potential sources of the current, the researchers conducted similar tests using structures that were not piezoelectric or semiconducting.  \u0022After a variety of tests, we are confident that what we are seeing is a piezoelectric-induced discharge process,\u0022 Wang said.\n\u003C\/p\u003E\n\u003Cp\u003EThe researchers grew the nanowire arrays using a standard vapor-liquid-solid process in a small tube furnace.  First, gold nanoparticles were deposited onto a sapphire substrate placed in one end of the furnace.  An argon carrier gas was then flowed into the furnace as zinc oxide powder was heated.  The nanowires grew beneath the gold nanoparticles, which serve as catalysts.\n\u003C\/p\u003E\n\u003Cp\u003EThe resulting arrays contained vertically-aligned nanowires that ranged from 200 to 500 nanometers in length and 20 to 40 nanometers in diameter.  The wires grew approximately 100 nanometers apart, as determined by the placement of the gold nanoparticles.  \n\u003C\/p\u003E\n\u003Cp\u003EA film of zinc oxide also grew between the wires on the substrate surface, creating an electrical connection between the wires.  To that conductive substrate, the researchers attached an electrode for measuring current flow.\n\u003C\/p\u003E\n\u003Cp\u003EThough attractive for use inside the body because zinc oxide is non-toxic, the nanogenerators could also be used wherever mechanical energy - hydraulic motion of seawater, wind or the motion of a foot inside a shoe - is available.  The nanowires can be grown not only on crystal substrates, but also on polymer-based films.  Use of flexible polymer substrates could one day allow portable devices to be powered by the movement of their users.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022You could envision having these nanogenerators in your shoes to produce electricity as you walk,\u0022 Wang said.  \u0022This could be beneficial to soldiers in the field, who now depend on batteries to power their electrical equipment.  As long as the soldiers were moving, they could generate electricity.\u0022\n\u003C\/p\u003E\n\u003Cp\u003ECurrent could also be produced by placing the nanowire arrays into fields of acoustic or ultrasonic energy.  Though they are ceramic materials, the nanowires can bend as much as 50 degrees without breaking.\n\u003C\/p\u003E\n\u003Cp\u003EThe next step in the research will be to maximize the power produced by an array of the new nanogenerators.  Wang estimates that they can convert as much as 30 percent of the input mechanical energy into electrical energy for a single cycle of vibration.  That could allow a nanowire array just 10 microns square to power a single nanoscale device - if all the power generated by the nanowire array can be successfully collected. \n\u003C\/p\u003E\n\u003Cp\u003E\u0022Our bodies are good at converting chemical energy from glucose into the mechanical energy of our muscles,\u0022 Wang noted.  \u0022These nanogenerators can take that mechanical energy and convert it to electrical energy for powering devices inside the body.  This could open up tremendous possibilities for self-powered implantable medical devices.\u0022\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\nGeorgia Institute of Technology\u003Cbr \/\u003E\n75 Fifth Street, N.W., Suite 100\u003Cbr \/\u003E\nAtlanta, Georgia 30308\u003C\/strong\u003E\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contacts\u003C\/strong\u003E: John Toon (404-894-6986); E-mail: (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E) or Jane Sanders (404-894-2214); E-mail: (\u003Ca href=\u0022mailto:jane.sanders@edi.gatech.edu\u0022\u003Ejane.sanders@edi.gatech.edu\u003C\/a\u003E).\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003ETechnical Contact\u003C\/strong\u003E: Zhong Lin Wang (404-894-8008); E-mail: (\u003Ca href=\u0022mailto:zhong.wang@mse.gatech.edu\u0022\u003Ezhong.wang@mse.gatech.edu\u003C\/a\u003E).\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\n\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":[{"value":"Researchers convert mechanical energy to electrical energy for self-powered nanometer scale devices"}],"field_summary":[{"value":"Researchers have developed a new technique for powering nanometer-scale devices without the need for bulky energy sources such as batteries.","format":"limited_html"}],"field_summary_sentence":[{"value":"Researchers develop generator for nanoscale devices"}],"uid":"27303","created_gmt":"2006-04-13 00:00:00","changed_gmt":"2016-10-08 03:03:34","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2006-04-13T00:00:00-04:00","iso_date":"2006-04-13T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"73049":{"id":"73049","type":"image","title":"Nanogenerator sample","body":null,"created":"1449177979","gmt_created":"2015-12-03 21:26:19","changed":"1475894671","gmt_changed":"2016-10-08 02:44:31"},"73050":{"id":"73050","type":"image","title":"Zhong Lin Wang in Laboratory","body":null,"created":"1449177979","gmt_created":"2015-12-03 21:26:19","changed":"1475894671","gmt_changed":"2016-10-08 02:44:31"},"73051":{"id":"73051","type":"image","title":"Nanowires, electric discharge","body":null,"created":"1449177979","gmt_created":"2015-12-03 21:26:19","changed":"1475894671","gmt_changed":"2016-10-08 02:44:31"}},"media_ids":["73049","73050","73051"],"related_links":[{"url":"http:\/\/www.mse.gatech.edu\/FacultyStaff\/MSE_Faculty_researchbios\/Wang\/wang.html","title":"Zhong Lin Wang"},{"url":"http:\/\/www.mse.gatech.edu\/","title":"Georgia Tech School of Materials Science and Engineering"},{"url":"http:\/\/www.nanoscience.gatech.edu\/zlwang\/","title":"Team Web site"}],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[],"keywords":[],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cstrong\u003EJohn Toon\u003C\/strong\u003E\u003Cbr \/\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\u003Ca href=\u0022http:\/\/www.gatech.edu\/contact\/index.html?id=jt7\u0022\u003EContact John Toon\u003C\/a\u003E\u003Cbr \/\u003E\u003Cstrong\u003E404-894-6986\u003C\/strong\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}