Author: Robert A. Sayer

Publisher:

Published: 2006

Total Pages:

ISBN-13:

Abstract: Several creatures including insects, spiders, and lizards, have developed a unique clinging ability that utilizes dry adhesion. Geckos, in particular, have developed the most complex adhesive structures capable of smart adhesion--the ability to cling on different smooth and rough surfaces and detach at will. These animals make use of on the order of a million microscale hairs (setae) (about 14000/mm2) that branch off into hundreds of nanoscale spatulae. This hierarchical surface construction gives the gecko the adaptability to create a large real area of contact with surfaces. van der Waals forces are the primary mechanism utilized to adhere to surfaces and capillary forces are a secondary effect that can further increase adhesive force. Although a gecko is capable of producing on the order of 20 N of adhesive force, it retains the ability to remove its feet from an attachment surface at will. A man-made fibrillar structure capable of replicating gecko adhesion has the potential for use in dry, superadhesive tapes that would be of use in a wide range of applications. These adhesives could be created using micro/nanofabrication techniques or self-assembly. A fibrillar polyvinylsiloxane (PVS) sample consisting of an array pillars (about 230/mm2) approximately 50 um in diameter, 70 um in height and 60 um center-to-center was compared to an unstructured sample. Structured roughness was found to be more important than random roughness in adhesion. The added roughness of the structured sample increased the hydrophobicity of the surface.