{"72234":{"#nid":"72234","#data":{"type":"news","title":"Nanogenerator Provides Continuous Electrical Power","body":[{"value":"\u003Cp\u003EResearchers have demonstrated a prototype nanometer-scale generator that produces continuous direct-current electricity by harvesting mechanical energy from such environmental sources as ultrasonic waves, mechanical vibration or blood flow.\u003C\/p\u003E\n\u003Cp\u003EBased on arrays of vertically-aligned zinc oxide nanowires that move inside a novel \u0027zig-zag\u0027 plate electrode, the nanogenerators could provide a new way to power nanoscale devices without batteries or other external power sources.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022This is a major step toward a portable, adaptable and cost-effective technology for powering nanoscale devices,\u0022 said Zhong Lin Wang, Regents\u0027 Professor in the School of Materials Science and Engineering at the Georgia Institute of Technology.  \u0022There has been a lot of interest in making nanodevices, but we have tended not to think about how to power them.  Our nanogenerator allows us to harvest or recycle energy from many sources to power these devices.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EDetails of the nanogenerator are reported in the April 6 issue of the journal \u003Cem\u003EScience\u003C\/em\u003E.  The research was sponsored by the Defense Advanced Research Projects Agency (DARPA), the National Science Foundation (NSF), and the Emory-Georgia Tech Center of Cancer Nanotechnology Excellence.\n\u003C\/p\u003E\n\u003Cp\u003EThe nanogenerators take advantage of the unique coupled piezoelectric and semiconducting properties of zinc oxide nanostructures, which produce small electrical charges when they are flexed.  \n\u003C\/p\u003E\n\u003Cp\u003EFabrication begins with growing an array of vertically-aligned nanowires approximately a half-micron apart on gallium arsenide, sapphire or a flexible polymer substrate.  A layer of zinc oxide is grown on top of substrate to collect the current.  The researchers also fabricate silicon \u0027zig-zag\u0027 electrodes, which contain thousands of nanometer-scale tips made conductive by a platinum coating.\n\u003C\/p\u003E\n\u003Cp\u003EThe electrode is then lowered on top of the nanowire array, leaving just enough space so that a significant number of the nanowires are free to flex within the gaps created by the tips. Moved by mechanical energy such as waves or vibration, the nanowires periodically contact the tips, transferring their electrical charges.  By capturing the tiny amounts of current produced by hundreds of nanowires kept in motion, the generators produce a direct current output in the nano-Ampere range.  \n\u003C\/p\u003E\n\u003Cp\u003EWang and his group members Xudong Wang, Jinhui Song and Jin Liu expect that with optimization, their nanogenerator could produce as much as 4 watts per cubic centimeter - based on a calculation for a single nanowire.  That would be enough to power a broad range of nanometer-scale defense, environmental and biomedical applications, including biosensors implanted in the body, environmental monitors - and even nanoscale robots.\n\u003C\/p\u003E\n\u003Cp\u003ENearly a year ago, in the April 14, 2006 issue of the journal \u003Cem\u003EScience\u003C\/em\u003E, Wang\u0027s research team announced the concept behind the nanogenerators.  At that time, the nanogenerator could harvest power from just one nanowire at a time by dragging the tip of an atomic force microscope (AFM) over it.  Made of platinum-coated silicon, the tip served as a Schottky barrier, helping accumulate and preserve the electrical charge as the nanowire flexed - and ensuring that the current flowed in one direction.\n\u003C\/p\u003E\n\u003Cp\u003EWith its multiple conducting tips similar to those of an AFM, the new zig-zag electrode serves as a Schottky barrier to hundreds or thousands of wires simultaneously, harvesting energy from the nanowire arrays.  \n\u003C\/p\u003E\n\u003Cp\u003E\u0022Producing the top electrode as a single assembly sets the stage for scaling up this technology,\u0022 Wang said.  \u0022We can now see the steps involved in moving forward to a device that can power real nanometer-scale applications.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EBefore that happens, additional development will be needed to optimize current production.  For instance, though nanowires in the arrays can be grown to approximately the same length - about one micron - there is some variation.  Wires that are too short cannot touch the electrode to produce current, while wires that are too long cannot flex to produce electrical charge.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022We need to be able to better control the growth, density and uniformity of the wires,\u0022 Wang said.  \u0022We believe we can make as many as millions or even billions of nanowires produce current simultaneously.  That will allow us to optimize operation of the nanogenerator.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EIn their lab, the researchers aimed an ultrasound source at their nanogenerator to measure current output over slightly more than an hour.  Though there is some fluctuation in output, the current flow was continuous as long as the ultrasonic generator was operating, Wang said.\n\u003C\/p\u003E\n\u003Cp\u003ETo rule out other sources of the current measured, the researchers substituted carbon nanotubes - which are not piezoelectric - for the zinc oxide nanowires, and used a top electrode that was flat.  In both cases, the resulting devices did not produce current.\n\u003C\/p\u003E\n\u003Cp\u003EProviding power for nanometer-scale devices has long been a challenge.  Batteries and other traditional sources are too large, and tend to negate the size advantages of nanodevices.  And since batteries contain toxic materials such as lithium and cadmium, they cannot be implanted into the body as part of biomedical applications.\n\u003C\/p\u003E\n\u003Cp\u003EBecause zinc oxide is non-toxic and compatible with the body, the new nanogenerators could be integrated into implantable biomedical devices to wirelessly measure blood flow and blood pressure within the body.  And they could also find more ordinary applications.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022If you had a device like this in your shoes when you walked, you would be able to generate your own small current to power small electronics,\u0022 Wang noted. \u0022Anything that makes the nanowires move within the generator can be used for generating power.  Very little force is required to move them.\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  USA\u003C\/strong\u003E\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contact\u003C\/strong\u003E: John Toon (404-894-6986); E-mail (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@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":"Device harvests energy from the environment to provide direct current"}],"field_summary":[{"value":"Researchers have demonstrated a prototype nanometer-scale generator that produces continuous direct-current electricity by harvesting mechanical energy from such environmental sources as ultrasonic waves, mechanical vibration or blood flow.","format":"limited_html"}],"field_summary_sentence":[{"value":"New device harvests energy for electric power"}],"uid":"27303","created_gmt":"2007-04-05 00:00:00","changed_gmt":"2016-10-08 03:03:29","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2007-04-05T00:00:00-04:00","iso_date":"2007-04-05T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"72235":{"id":"72235","type":"image","title":"Zhong Lin Wang","body":null,"created":"1449177446","gmt_created":"2015-12-03 21:17:26","changed":"1475894653","gmt_changed":"2016-10-08 02:44:13"},"72236":{"id":"72236","type":"image","title":"Close-up of nanogenerator","body":null,"created":"1449177446","gmt_created":"2015-12-03 21:17:26","changed":"1475894653","gmt_changed":"2016-10-08 02:44:13"},"72237":{"id":"72237","type":"image","title":"Schematic of nanogenerator","body":null,"created":"1449177446","gmt_created":"2015-12-03 21:17:26","changed":"1475894653","gmt_changed":"2016-10-08 02:44:13"}},"media_ids":["72235","72236","72237"],"related_links":[{"url":"http:\/\/www.mse.gatech.edu\/","title":"Georgia Tech School of Materials Science and Engineering"},{"url":"http:\/\/www.mse.gatech.edu\/FacultyStaff\/MSE_Faculty_researchbios\/Wang\/wang.html","title":"Zhong Lin Wang"}],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"145","name":"Engineering"},{"id":"149","name":"Nanotechnology and Nanoscience"},{"id":"135","name":"Research"}],"keywords":[{"id":"7567","name":"direct-current"},{"id":"436","name":"electricity"},{"id":"7568","name":"harvest"},{"id":"1334","name":"nanogenerator"}],"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":""}}}