Gecko Hair Manufacture Synthetic Gecko Hair Fabrication for Dry Adhesion Introduction: Nature can be an inspiration for innovations in science. One such inspiration is comes from the gecko lizard which can climb on walls and ceilings of almost any suface texture. Rather than using it's claws or sticky substances, the gecko is able to stick to smooth surfaces through dry adhesion which requires no energy to hold it to the surface and leaves no residue. The dry adhesion force comes from surface contact forces such as van der Waals forces which act between all materials in contact. The gecko's trick to sticking to surfaces lies in its feet, specifically the very fine hairs on its toes. There are billions of these tiny hairs which make contact with the surface and create a huge collective surface area of contact. The hairs have physical propeties which let them bend and conform to a wide variety of surface roughnesses, meaning that the gecko's secret lies in the structure of these hairs themselves. By studying this structure, we are able to mimic the biological structures with synthetic materials. The structure of the biological gecko hair is very complicated as well as very miniscule. Each hair is made from multiple sections, a micro-hair which is roughly 5 microns in diameter, and atop each of these micro-hairs sit tens to hundreds of nano-hairs which are 200 nanometers in diameter (1/250th of a human hair) in a tree-like branching structure. Goal: Develop techniques for producing synthetic gecko foot hairs with nano/micro hair heirarchy. Refine these techniques into processes which will alow for cost effective mass production. Utilize the gecko hair material to create advanced ultra-mobile robots. Approach: Our lab uses a multitude of techniques to produce the gecko hairs. The major areas of research are: Micro and Nano Molding MEMS Photolithography MEMS Deep Reactive Ion Etching By using our Force Characterization Systems we are able to get immediate feedback from our gecko hair samples, therefore we can rapidly evolve our designs to reach an optimal design. Benefits: The new synthetic adhesive will have countless uses from space exploration robots to surgical applications to post-it notes. This reusable, self-cleaning adhesive material can be thought of as a one sided velcro which can stick to almost everything. Videos: Video 1: 30um diameter polyurethane fibers attaching to a curved glass surface. Members: Mike Murphy, Seok Kim, Burak Aksak, Metin Sitti Papers: 2008 S. Kim, J.-H. Jang, M. Sitti, and E. Thomas, "Fabrication of gecko foot inspired elastomer nanofibers with spatulate tips," IEEE Nanotechnology, 2008, to appear. S. Kim and M. Sitti, "Fabrication and characterization of biologically inspired mushroom-shaped elastomer microfiber arrays," ASME IDETC Micro/Nano Systems, 2008, to appear. S. Kim and M. Sitti, "Fabrication and characterization of biologically Inspired microfiber arrays with spatulate tips," International Conference on Micromanufacturing, 2008, to appear. R. Long, C.-Y. Hui, S. Kim, and M. Sitti, "Modeling the Soft Backing Layer Thickness Effect on Adhesion of Elastic Microfiber Arrays," Journal of Applied Physics, 2008, in press. B. Aksak, M. Murphy, M. Sitti, "Gecko Inspired Micro-Fibrillar Adhesives for Wall Climbing Robots on Micro/Nanoscale Rough Surfaces," ICRA, Pasadena, CA, May 2008. [pdf] 2007 S. Kim, B. Aksak, M. Sitti, "Enhanced Friction of Elastomer Microfiber Adhesives with Spatulate Tips," Applied Physics Letters, 91, 2007. M. Murphy, B. Aksak, M. Sitti, "Adhesion and Anisotropic Friction Enhancements of Angled Heterogeneous Micro-Fiber Arrays with Spherical and Spatula Tips," Journal of Adhesion Science and Technology, 21, 1281-1296, 2007. S. Kim, M. Sitti, C. Hui, R. Long, and A. Jagota, Applied Physics Letters, 91, 161905 (2007) B. Aksak, M. Murphy, M. Sitti, "Adhesion of Biologically Inspired Vertical and Angled Polymer Microfiber Arrays", Langmuir, 0743-7463, 2007. available online. 2006 S. Kim and M. Sitti, ''Biologically Inspired Polymer Microfibers with Spatulate Tips as Repeatable Fibrillar Adhesives,'' Applied Physics Letters, vol. 89, no. 26, pp. 26911-13, 27 Dec. 2006. pdf G. Shah, M. Sitti, ''Modeling and Design of Biomimetic Adhesives Inspired by Gecko Foot-Hairs'' IEEE International Conference on Robotics and Biomimetics (ROBIO), Shenyang, China, Aug 2004. pdf C. Menon, M. Murphy, M. Sitti, ''Gecko Inspired Surface Climbing Robots'' IEEE International Conference on Robotics and Biomimetics (ROBIO), Shenyang, China, Aug 2004. pdf M. Sitti and R. S. Fearing, ''Synthetic Gecko Foot-Hair Micro/Nano-Structures as Dry Adhesives for Future Wall-Climbing Robots,'' IEEE Robotics and Automation Conference, pp. 1164-1170, Taiwan, September 2003. pdf M. Sitti and R. S. Fearing, ''Nanomolding based Fabrication of Synthetic Gecko Foot-Hair Micro/Nanostructures,'' IEEE Nanotechnology Conference, pp. 137-140, Washington, DC, USA, August 2002. pdf K. Autumn, M. Sitti, Y. A. Liang, A. Peattie, W. Hansen, S. Sponberg, T. Kenny, R. Fearing, J. Israelachvili & R. J. Full, ''Evidence for van der Waals attachment for geckos,'' PNAS, vol. 99, no. 19, pp. 12252-12256, 17 Sept. 2002. pdf List of biologically inspred adhesive publications

[Synthetic gecko foot hair heirarchy] [Close up view of nanohairs and their interaction with the surface] [Synthetic angled fibers with various tip geometry] [Fibers with spatulae] [Fibers with spatulae] [40um diameter polyurethane fibers (1 cm^2) holding 500 grams] [28um diameter polyurethane fibers stretching in contact]