{"462531":{"#nid":"462531","#data":{"type":"news","title":"Ants: Both Solid-like and Liquid-like","body":[{"value":"\u003Cp\u003ECollections of ants have a remarkable ability to change shapes and tasks based on the demands of their environment. When floodwaters hit, they self-assemble and form rafts to stay alive. They can also use their bodies to build bridges and span gaps. What are the properties of these ant aggregations that allow for this wide range of abilities? New research from the Georgia Institute of Technology says it\u2019s because the insects are actually liquid-like and solid-like simultaneously. The study is currently published in Nature Materials.\u003C\/p\u003E\u003Cp\u003EThe Georgia Tech group probed the mechanical properties of fire ant aggregations by putting thousands of ants into a rheometer, a machine used to test the solid-like and liquid-like response of materials such as food, hand cream or melted plastic.\u003C\/p\u003E\u003Cp\u003EThe ants were sheared at constant speeds from about 0.0001 rpm up to about 100 rpm. The researchers found that the behavior of live ants was similar to that of dead ants: when the aggregation is forced to flow, live ants let go and play dead. In this case, the viscosity dramatically decreased as the speed increased.\u003C\/p\u003E\u003Cp\u003E\u201cIt\u2019s not unlike ketchup,\u201d said Alberto Fernandez-Nieves, an associate professor in the School of Physics. \u201cThe harder you squeeze, the easier it flows. But with ants, this happens much more dramatically than with ketchup.\u201d\u003C\/p\u003E\u003Cp\u003E\u201c\u003Ca href=\u0022https:\/\/www.youtube.com\/watch?v=B0QVXVgcdhs\u0022\u003EAnts seem to have an on\/off switch\u003C\/a\u003E in that they let go for sufficiently large applied forces,\u201d said David Hu, an associate professor in the George W. Woodruff School of Mechanical Engineering. \u201cDespite wanting to be together, they let go and behave like a fluid to prevent getting injured or killed.\u201d\u003C\/p\u003E\u003Cp\u003EThis same behavior \u003Ca href=\u0022https:\/\/youtu.be\/wMbbFCxrsno\u0022\u003Ecan be seen by dropping a penny\u003C\/a\u003E through an ant aggregation. Ants will flow around the coin as it sinks through the aggregation. This flow takes a relatively long time to happen. However, when the aggregation is poked quickly, it responds like a spring and returns to its original shape.\u003C\/p\u003E\u003Cp\u003E\u201cThis is the hallmark of viscoelastic behavior,\u201d said Fernandez-Nieves. \u201cThe ants exhibit a springy-response when probed at short times, but behave fluid-like at longer times.\u201d\u003C\/p\u003E\u003Cp\u003EThe group quantified this by looking at the ants\u2019 response to tiny wiggles of the rheometer. They found that the ants are equally liquid-like and solid-like. They did the same experiment with dead ants and saw that they are also solid-like. This showed that live ants are liquid-like and solid-like because of their activity.\u003C\/p\u003E\u003Cp\u003E\u201cRemarkably, the observed behavior is similar to what is seen in materials that are not alive, like polymer gels right at the point when they become a gel,\u201d said Fernandez-Nieves. \u201cThis is quite puzzling, and we are now performing many more experiments to try and understand where these similarities arise from and how much they can be pushed. Doing this will hopefully extend our current way of thinking about materials, that like the ants, are active and thus out-of-equilibrium. There is much more interesting work we plan on doing with ants.\u201d\u003C\/p\u003E\u003Cp\u003EHu has studied ant behavior for nearly 10 years. Fernandez-Nieves is a physicist who uses rheology to understand the mechanics of soft materials and unravel the microscopic origin of their overall properties and behaviors.\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022http:\/\/www.antphysics.gatech.edu\/\u0022\u003EMichael Tennenbaum\u003C\/a\u003E, a graduate research assistant who participated in the study, also compared the behavior of the ant aggregation to jello.\u003C\/p\u003E\u003Cp\u003E\u201cImagine if you wanted to make the most jello possible out of a packet of gelatin. It would be solid, but also very liquidy,\u201d he said. \u201cThat\u2019s because there would be just barely enough gelatin to make it solid-like but not enough to make it completely solid. The jello would be both solid-like and liquid-like.\u201d\u003C\/p\u003E\u003Cp\u003EHu has also used the liquid-like nature of the ants to study self-healing materials.\u003C\/p\u003E\u003Cp\u003E\u201cIf you cut a dinner roll with a knife, you\u2019re going to end up with two pieces of bread,\u201d said Hu. \u201cBut if you cut through a pile of ants, they\u2019ll simply let the knife go through, then reform on the other side. They\u2019re like liquid metal \u2013 just like that scene in the Terminator movie.\u201d\u003C\/p\u003E\u003Cp\u003EHu says it\u2019s this flexibility that allows ants to enjoy the best of both worlds. They\u2019re able to become solids to make things and liquids to avoid breaking into \u201csmithereens.\u201d\u003C\/p\u003E\u003Cp\u003EThe study, \u201c\u003Ca href=\u0022http:\/\/www.nature.com\/nmat\/journal\/vaop\/ncurrent\/full\/nmat4450.html\u0022\u003EMechanics of Ant Aggregations\u003C\/a\u003E,\u201d was published in Nature Materials on October 26, 2015.\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis research is supported by the U.S. Army Research Laboratory and the U.S. Army Research Office Mechanical Sciences Division, Complex Dynamics and Systems Program, under contract numbers W911NF-12-R-0011 and W911NF-14-1-0487.\u003C\/em\u003E \u003Cem\u003EAny conclusions expressed are those of the principal investigator and may not necessarily represent the official views of the funding organization. \u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003EADDITIONAL PHOTOS AND VIDEO ARE AVAILABLE HERE: \u003Ca href=\u0022https:\/\/www.dropbox.com\/sh\/hycnwywaxdeau60\/AAAHt79dAvREDICnt3nL4nlba?dl=0\u0022 title=\u0022https:\/\/www.dropbox.com\/sh\/hycnwywaxdeau60\/AAAHt79dAvREDICnt3nL4nlba?dl=0\u0022\u003Ehttps:\/\/www.dropbox.com\/sh\/hycnwywaxdeau60\/AAAHt79dAvREDICnt3nL4nlba?dl=0\u003C\/a\u003E\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":[{"value":"Ants act like ketchup when forces applied"}],"field_summary":[{"value":"\u003Cp\u003EThe researchers found that the behavior of live ants was similar to that of dead ants: when the aggregation is forced to flow, live ants let go and play dead. In this case, the viscosity dramatically decreased as the speed increased.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Study finds that ants are actually liquid-like and solid-like simultaneously"}],"uid":"27560","created_gmt":"2015-10-26 12:59:47","changed_gmt":"2016-10-08 03:19:51","author":"Jason Maderer","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2015-10-26T00:00:00-04:00","iso_date":"2015-10-26T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"462471":{"id":"462471","type":"image","title":"Ants in Rheometer","body":null,"created":"1449256373","gmt_created":"2015-12-04 19:12:53","changed":"1475895206","gmt_changed":"2016-10-08 02:53:26","alt":"Ants in Rheometer","file":{"fid":"203638","name":"rheometer.jpg","image_path":"\/sites\/default\/files\/images\/rheometer_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/rheometer_0.jpg","mime":"image\/jpeg","size":1244226,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/rheometer_0.jpg?itok=tklSKNCZ"}},"382241":{"id":"382241","type":"image","title":"David Hu","body":null,"created":"1449246231","gmt_created":"2015-12-04 16:23:51","changed":"1493396247","gmt_changed":"2017-04-28 16:17:27","alt":"Daivd Hu","file":{"fid":"75309","name":"hu.jpg","image_path":"\/sites\/default\/files\/images\/hu.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/hu.jpg","mime":"image\/jpeg","size":24895,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/hu.jpg?itok=JoMWZnaG"}},"462451":{"id":"462451","type":"image","title":"Alberto Fernandez-Nieves","body":null,"created":"1449256373","gmt_created":"2015-12-04 19:12:53","changed":"1475895206","gmt_changed":"2016-10-08 02:53:26","alt":"Alberto Fernandez-Nieves","file":{"fid":"203636","name":"alberto.jpg","image_path":"\/sites\/default\/files\/images\/alberto_1.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/alberto_1.jpg","mime":"image\/jpeg","size":408291,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/alberto_1.jpg?itok=28CR8AYG"}}},"media_ids":["462471","382241","462451"],"related_links":[{"url":"http:\/\/www.nature.com\/nmat\/journal\/vaop\/ncurrent\/full\/nmat4450.html","title":"Read the study"},{"url":"http:\/\/www.me.gatech.edu\/","title":"George W. Woodruff School of Mechanical Engineering"},{"url":"https:\/\/www.physics.gatech.edu\/","title":"School of Physics"},{"url":"http:\/\/www.antphysics.gatech.edu\/","title":"Ant Physics Website"}],"groups":[{"id":"1183","name":"Home"}],"categories":[{"id":"135","name":"Research"},{"id":"150","name":"Physics and Physical Sciences"}],"keywords":[{"id":"66681","name":"Alberto Fernandez-Nieves"},{"id":"20471","name":"Ants"},{"id":"297","name":"David Hu"}],"core_research_areas":[{"id":"39441","name":"Bioengineering and Bioscience"},{"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\u003EJason Maderer\u003Cbr \/\u003ENational Media Relations\u003Cbr \/\u003E404-660-2926\u003Cbr \/\u003E\u003Ca href=\u0022mailto:maderer@gatech.edu\u0022\u003Emaderer@gatech.edu\u003C\/a\u003E\u003C\/p\u003E","format":"limited_html"}],"email":["maderer@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}