title: Evidence for capillarity contributions to gecko adhesion from single spatula nanomechanical measurements.
abstract: The hairy attachment system on a gecko's toes, consisting of one billion spatulae in the case of Gekko gecko [Ruibal, R. & Ernst, V. (1965) J. Morphol. 117, 271-294], allows it to adhere to nearly all surface topographies. The mechanistic basis for gecko adhesion has been intensely investigated, but the lowest hierarchical level, that of the spatula, has become experimentally accessible only recently. This report details measurements of the adhesion force exerted by a single gecko spatula for various atmospheric conditions and surface chemistries. Through judicious choice and modification of substrates, the short- and long-range adhesive forces are separated. In contrast to previous work [Autumn, K., Sitti, M., Liang, Y. C. A., Peattie, A. M., Hansen, W. R., Sponberg, S., Kenny, T. W., Fearing, R., Israelachvili, J. N. & Full, R. J. (2002) Proc. Natl. Acad. Sci. USA 99, 12252-12256], our measurements clearly show that humidity contributes significantly to gecko adhesion on a nanoscopic level. These findings are crucial for the development of artificial biomimetic attachment systems.
authors.affiliation: Max Planck Institute for Metals Research, Heisenbergstrasse 3, D-70569 Stuttgart, Germany.
authors.forename: Gerrit
authors.initials: G
authors.lastname: Huber
authors.forename: Hubert
authors.initials: H
authors.lastname: Mantz
authors.forename: Ralph
authors.initials: R
authors.lastname: Spolenak
authors.forename: Klaus
authors.initials: K
authors.lastname: Mecke
authors.forename: Karin
authors.initials: K
authors.lastname: Jacobs
authors.forename: Stanislav N
authors.initials: SN
authors.lastname: Gorb
authors.forename: Eduard
authors.initials: E
authors.lastname: Arzt
mesh_terms: D000268:Adhesiveness; D000327:Adsorption; D000818:Animals; D002197:Capillary Action; D006813:Humidity; D008116:Lizards / Q000502:physiology*