{"238821":{"#nid":"238821","#data":{"type":"news","title":"Glass or Plastic? Container\u2019s Properties Affect the Viscosity of Nanoscale Water","body":[{"value":"\u003Cp\u003EWater pours into a cup at about the same rate regardless of whether the water bottle is made of glass or plastic.\u003C\/p\u003E\u003Cp\u003EBut at nanometer-size scales for water and potentially other fluids, whether the container is made of glass or plastic does make a significant difference. A new study shows that in nanoscopic channels, the effective viscosity of water in channels made of glass can be twice as high as water in plastic channels. Nanoscopic glass channels can make water flow more like ketchup than ordinary H\u003Csub\u003E2\u003C\/sub\u003EO.\u003C\/p\u003E\u003Cp\u003EThe effect of container properties on the fluids they hold offers yet another example of surprising phenomena at the nanoscale. And it also provides a new factor that the designers of tiny mechanical systems must take into account.\u003C\/p\u003E\u003Cp\u003E\u201cAt the nanoscale, viscosity is no longer constant, so these results help redefine our understanding of fluid flow at this scale,\u201d said \u003Ca href=\u0022https:\/\/www.physics.gatech.edu\/user\/elisa-riedo\u0022\u003EElisa Riedo\u003C\/a\u003E, an associate professor in the \u003Ca href=\u0022http:\/\/www.physics.gatech.edu\/\u0022\u003ESchool of Physics\u003C\/a\u003E at the Georgia Institute of Technology. \u201cAnyone performing an experiment, developing a technology or attempting to understand a biological process that involves water or another liquid at this size scale will now have to take the properties of surfaces into account.\u201d\u003C\/p\u003E\u003Cp\u003EThose effects could be important to designers of devices such as high resolution 3D printers that use nanoscale nozzles, nanofluidic systems and even certain biomedical devices.\u003C\/p\u003E\u003Cp\u003EConsidering that nano-confined water is ubiquitous in animal bodies, in rocks, and in nanotechnology, this new understanding could have a broad impact.\u003C\/p\u003E\u003Cp\u003EResearch into the properties of liquids confined by different materials was sponsored by the Department of Energy\u2019s Office of Basic Sciences and the National Science Foundation. The results were reported September 19 in the journal \u003Cem\u003ENature Communications\u003C\/em\u003E.\u003C\/p\u003E\u003Cp\u003EThe viscosity differences created by container materials are directly affected by the degree to which the materials are either hydrophilic \u2013 which means they attract water \u2013 or hydrophobic \u2013 which means they repel it. The researchers believe that in hydrophilic materials, the attraction for water \u2013 a property known as \u201cwettability\u201d \u2013 makes water molecules more difficult to move, contributing to an increase in the fluid\u2019s effective viscosity. On the other hand, water isn\u2019t as attracted to hydrophobic materials, making the molecules easier to move and producing lower viscosity.\u003C\/p\u003E\u003Cp\u003EIn research reported in the journal, this water behavior appeared only when water was confined to spaces of a few nanometers or less \u2013 the equivalent of just a few layers of water molecules.\u0026nbsp; The viscosity continued to increase as the surfaces were moved closer together.\u003C\/p\u003E\u003Cp\u003EThe research team studied water confined by five different surfaces: mica, graphene oxide, silicon, diamond-like carbon, and graphite. Mica, used in the drilling industry, was the most hydrophilic of the materials, while graphite was the most hydrophobic. \u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u201cWe saw a clear one-to-one relationship between the degree to which the confining material was hydrophilic and the viscosity that we measured,\u201d Riedo said.\u003C\/p\u003E\u003Cp\u003EExperimentally, the researchers began by preparing atomically-smooth surfaces of the materials, then placing highly-purified water onto them. Next, an AFM tip made of silicon was moved across the surfaces at varying heights until it made contact. The tip \u2013 about 40 nanometers in diameter \u2013 was then lifted up and the measurements continued.\u003C\/p\u003E\u003Cp\u003EAs the viscosity of the water increased, the force needed to move the AFM tip also increased, causing it to twist slightly on the cantilever beam used to raise and lower the tip. Changes in this torsion angle were measured by a laser bounced off the reflective cantilever, providing an indication of changes in the force exerted on the tip, the viscous resistance exerted \u2013 and therefore the water\u2019s effective viscosity.\u003C\/p\u003E\u003Cp\u003E\u201cWhen the AFM tip was about one nanometer away from the surface, we began to see an increase of the viscous force acting on the tip for the hydrophilic surfaces,\u201d Riedo said. \u201cWe had to use larger forces to move the tip at this point, and the closer we got to the surface, the more dramatic this became.\u201d\u003C\/p\u003E\u003Cp\u003EThose differences can be explained by understanding how water behaves differently on different surfaces.\u003C\/p\u003E\u003Cp\u003E\u201cAt the nanoscale, liquid-surface interaction forces become important, particularly when the liquid molecules are confined in tiny spaces,\u201d Riedo explained. \u201cWhen the surfaces are hydrophilic, the water sticks to the surface and does not want to move. On hydrophobic surfaces, the water is slipping on the surfaces. With this study, not only have we observed this nanoscale wetting-dependent viscosity, but we have also been able to explain quantitatively the origin of the observed changes and relate them to boundary slip. This new understanding was able to explain previous unclear results of energy dissipation during dynamic AFM studies in water.\u201d\u003C\/p\u003E\u003Cp\u003EWhile the researchers have so far only studied the effect of the material properties in water channels, Riedo expects to perform similar experiments on other fluids, including oils. Beyond simple fluids, she hopes to study complex fluids composed of nanoparticles in suspension to determine how the phenomenon changes with particle size and chemistry.\u003C\/p\u003E\u003Cp\u003E\u201cThere is no reason why this should not be true for other liquids, which means that this could redefine the way that fluid dynamics is understood at the nanoscale,\u201d she said. \u201cEvery technology and natural process that uses liquids confined at the nanoscale will be affected.\u201d\u003C\/p\u003E\u003Cp\u003EIn addition to Riedo, co-authors of the paper included Deborah Ortiz-Young, Hsiang-Chih Chiu and Suenne Kim, who were at Georgia Tech when the research was done, and Kislon Voitchovsky of the Ecole Polytechnique Federale de Lausanne in Switzerland.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECITATION\u003C\/strong\u003E: Deborah Ortiz-Young, Hsiang-Chih Chiu, Suenne Kim, Kislon Voitchovsky and Elisa Riedo, \u201cThe interplay between apparent viscosity and wettability in nanoconfined water,\u0022 (Nature Communications, 2013).\u0026nbsp;\u003Ca href=\u0022http:\/\/www.nature.com\/ncomms\/2013\/130919\/ncomms3482\/full\/ncomms3482.html\u0022\u003Ehttp:\/\/www.nature.com\/ncomms\/2013\/130919\/ncomms3482\/full\/ncomms3482.html\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis research was supported by the Office of Basic Energy Sciences of the U.S. Department of Energy (DOE) under grant DE-FG02-06ER46293 and by the National Science Foundation (NSF) under grants DMR-0120967, DMR-0706031 and CMMI-1100290. Any opinions or conclusions are those of the authors and do not necessarily reflect the official views of the DOE or NSF.\u003C\/em\u003E\u003Cbr \/\u003E\u003Cbr \/\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\u0026nbsp; 30332-0181 USA\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cbr \/\u003E\u003Cstrong\u003EMedia Relations Assistance\u003C\/strong\u003E: John Toon (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E)(404-894-6986) or Brett Israel (\u003Ca href=\u0022mailto:brett.israel@comm.gatech.edu\u0022\u003Ebrett.israel@comm.gatech.edu\u003C\/a\u003E)(404-385-1933)\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EWater pours into a cup at about the same rate regardless of whether the water bottle is made of glass or plastic. But at nanometer-size scales for water and potentially other fluids, whether the container is made of glass or plastic does make a significant difference.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"At the nanoscale, the properties of containers holding liquids can affect their viscosity."}],"uid":"27303","created_gmt":"2013-09-18 20:23:09","changed_gmt":"2016-10-08 03:14:56","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2013-09-19T00:00:00-04:00","iso_date":"2013-09-19T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"238791":{"id":"238791","type":"image","title":"Container-material1","body":null,"created":"1449243670","gmt_created":"2015-12-04 15:41:10","changed":"1475894914","gmt_changed":"2016-10-08 02:48:34","alt":"Container-material1","file":{"fid":"197736","name":"container-material2.jpg","image_path":"\/sites\/default\/files\/images\/container-material2_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/container-material2_0.jpg","mime":"image\/jpeg","size":899685,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/container-material2_0.jpg?itok=jHHjuIHl"}},"238801":{"id":"238801","type":"image","title":"Container-material2","body":null,"created":"1449243670","gmt_created":"2015-12-04 15:41:10","changed":"1475894914","gmt_changed":"2016-10-08 02:48:34","alt":"Container-material2","file":{"fid":"197737","name":"container-material3610.jpg","image_path":"\/sites\/default\/files\/images\/container-material3610_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/container-material3610_0.jpg","mime":"image\/jpeg","size":1356766,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/container-material3610_0.jpg?itok=-55JlA-2"}},"238811":{"id":"238811","type":"image","title":"Container-material-illustration","body":null,"created":"1449243670","gmt_created":"2015-12-04 15:41:10","changed":"1475894914","gmt_changed":"2016-10-08 02:48:34","alt":"Container-material-illustration","file":{"fid":"197738","name":"container-material-illustration.jpg","image_path":"\/sites\/default\/files\/images\/container-material-illustration_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/container-material-illustration_0.jpg","mime":"image\/jpeg","size":632853,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/container-material-illustration_0.jpg?itok=bNghWLnq"}}},"media_ids":["238791","238801","238811"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"141","name":"Chemistry and Chemical Engineering"},{"id":"149","name":"Nanotechnology and Nanoscience"},{"id":"150","name":"Physics and Physical Sciences"}],"keywords":[{"id":"13687","name":"Elisa Riedo"},{"id":"7425","name":"nanometer"},{"id":"431","name":"nanoscale"},{"id":"166937","name":"School of Physics"},{"id":"7424","name":"viscosity"},{"id":"5493","name":"wettability"}],"core_research_areas":[{"id":"39441","name":"Bioengineering and Bioscience"},{"id":"39451","name":"Electronics and Nanotechnology"},{"id":"39471","name":"Materials"}],"news_room_topics":[{"id":"71881","name":"Science and Technology"}],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EJohn Toon\u003C\/p\u003E\u003Cp\u003EResearch News\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E(404) 894-6986\u003C\/p\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}