Optimization of biomimetic attachment system contacting with a rough surface

Several creatures including insects, spiders, and lizards have a unique ability to cling to ceilings and walls utilizing dry adhesion. Their fibrillar structure is the primary source of high adhesion. In the design of fibrillar structures, it is necessary to ensure that the fibrils are compliant enough to easily deform to mating surface's roughness profile, yet rigid enough not to collapse under their own weight. Fiber density is also important to improve the adhesion. In this study, the authors construct the adhesion design database for biomimetic attachment system. A simple idealized fibrillar structure consisting of a singie-level array of micro-/nanobeams is modeled. The fibers are assumed as oriented cylindrical cantilever beams with spherical tip. They consider three necessary conditions: buckling, fracture, and sticking of fiber structure, which constrain the allowed geometry. The adhesion analysis is performed for the attachment system in contact with rough surfaces with different sigma values for different main design variables-the fiber radius, the aspect ratio, and the material elastic modulus. For. a given applied load, roughness of contacting surface, and fiber material, the procedure to find optimal fiber radius and aspect ratio for the desired adhesion coefficient is developed. Two case studies are conducted to show the usefulness of this approach. These adhesion design databases are useful for understanding biological systems and for guiding of fabrication of the biomimetic attachment system. (c) 2007 American Vacuum Society.