Hierarchical Micro-Fibrillar Adhesives For more information, see the General Gecko-hair fabrication page. Introduction: Gecko foot-hairs exhibit exceptional adhesion to smooth and rough surfaces. These hairs are complex multi-level branching structures with specialized tips. Here we mimic the hierarchical nature of the gecko's adhesive system using synthetic polymer fibers. Novel fabrication processes facilitate the creation of 2- and 3-level fiber structures with controlled geometry. The tips of each layer can also be created into a saucer-like flat mushroom shape for increased adhesion. The results of characterization of these hierarchical adhesives indicate that multi-level structuring acts to increase adhesion, particularly against surfaces with large amplitude roughness. The increased compliance of the hierarchical structures allows the fiber surfaces to tolerate larger surface asperities while maintaining strong contact. In addition to increased adhesive forces, the multi-level fibers exhibit significantly higher interface toughness than single level arrays, requiring much higher energy to separate them from a surface. Applications: Repeatable dry adhesives have many potential applications including: Advanced ultra-mobile robots. Diagnostic tool anchoring inside the body. Clothing closures to replace bulky and noisy Velcro. Ultra gripping gloves for sports applications. Videos: available online Papers: M. Murphy, S. Kim, and M. Sitti, "Enhanced Adhesion by Gecko Inspired Hierarchical Adhesives," Applied Materials and Interfaces (In Press), 2009. available online Members: Mike Murphy, Seok Kim, Metin Sitti General Gecko-hair fabrication page. List of biologically inspired adhesive publications

[Hierarchical fibers can conform to various surface roughnesses] [SEM image of 2 level microfibers] [Force-Distance plot comparing Unstructured, Single Level fibers and 2-level fibers]