Appliance Design - September 2007 - (Page 27) Going Gecko Mimicking the agile gecko’s uncanny ability to run up walls and across ceilings has long been a goal of materials scientists. Researchers at Rensselaer Polytechnic Institute, Troy, N.Y., and the University of Akron, Ohio, have taken one sticky step in the right direction, creating synthetic “gecko tape” with four times the sticking power of the real thing. In a paper published in the June 18–22 issue of the Proceedings of the National Academy of Sciences, the researchers described a process for making polymer surfaces covered with carbon nanotube hairs. The nanotubes imitate the thousands of microscopic hairs on a gecko’s footpad, which form weak bonds with whatever surface the creature touches, allowing it to unstick itself simply by shifting its foot. For the first time, the team has developed a prototype flexible patch that can stick and unstick repeatedly with properties better than the natural gecko foot. They fashioned their material into an adhesive tape that can be used on a wide variety of surfaces, including Teflon. Pulickel Ajayan, the Henry Burlage Professor of Materials Science and Engineering at Rensselaer, and Lijie Ci, a postdoctoral research associate in Ajayan’s lab, created the material in collaboration with Ali Dhinojwala, professor of polymer science at the University of Akron, and University of Akron graduate students Liehui Ge and Sunny Sethi. The researchers noted that others have tried to use carbon nanotube films and various fibrous structures as high-adhesive surfaces and to mimic gecko feet, but with limited success. They said that the patchy structures from micropatterned nanotubes are essential for the unique engineering feat to work, and that the nanotubes also need to be the right kind, with the right dimensions and compliance. The material could have a number of applications, including feet for wall-climbing robots; a dry, reversible adhesive in electronic devices; and outer space, where most adhesives don’t work because of the vacuum. The research was funded by the National Science Foundation. < Microfabricated aligned multiwalled carbon nanotube setae and spatulas. Image A is an optical picture of a gecko foot showing that the setae are arranged in many lobes along the foot. Image B is an SEM image of natural gecko setae terminating into thousands of smaller spatulas. The remaining are SEM images of the synthetic setae. Image C shows a side view of synthetic setae with width of 100 µm and Image D is a higher magnification of that. Images E through H show the synthetic setae at various widths: E is 50 µm; F is 100 µm; G is 250 µm; and H is 500 µm. Images courtesy of the University of Akron. For more Information Enter 116 www.applianceDESIGN.com AD09074Arc.indd 1 applianceDESIGN September 2007 27 8/13/07 11:23:51 AM http://www.arcom.com http://www.arcom.com http://www.appliancedesign.com
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