title: Influence of packing density and surface roughness of vertically-aligned carbon nanotubes on adhesive properties of gecko-inspired mimetics.
abstract: We have systematically studied the macroscopic adhesive properties of vertically aligned nanotube arrays with various packing density and roughness. Using a tensile setup in shear and normal adhesion, we find that there exists a maximum packing density for nanotube arrays to have adhesive properties. Too highly packed tubes do not offer intertube space for tube bending and side-wall contact to surfaces, thus exhibiting no adhesive properties. Likewise, we also show that the surface roughness of the arrays strongly influences the adhesion properties and the reusability of the tubes. Increasing the surface roughness of the array strengthens the adhesion in the normal direction, but weakens it in the shear direction. Altogether, these results allow progress toward mimicking the gecko's vertical mobility.
authors.affiliation: Department of Engineering, University of Cambridge , Cambridge, CB2 1PZ, United Kingdom.
authors.forename: Bingan
authors.initials: B
authors.lastname: Chen
authors.forename: Guofang
authors.initials: G
authors.lastname: Zhong
authors.forename: Pola Goldberg
authors.initials: PG
authors.lastname: Oppenheimer
authors.forename: Can
authors.initials: C
authors.lastname: Zhang
authors.forename: Hans
authors.initials: H
authors.lastname: Tornatzky
authors.forename: Santiago
authors.initials: S
authors.lastname: Esconjauregui
authors.forename: Stephan
authors.initials: S
authors.lastname: Hofmann
authors.forename: John
authors.initials: J
authors.lastname: Robertson
mesh_terms: D000268:Adhesiveness; D000269:Adhesives / Q000737:chemistry*; D000818:Animals; D040761:Biomimetic Materials / Q000737:chemistry*; D032701:Biomimetics; D008116:Lizards; D037742:Nanotubes, Carbon / Q000737:chemistry*
chemical_list: D000269:Adhesives; D037742:Nanotubes, Carbon
keywords: area density; carbon nanotube forests; dry adhesive; normal adhesion; packing density; roughness; shear adhesion