title: Harnessing tunable scanning probe techniques to measure shear enhanced adhesion of gecko-inspired fibrillar arrays.
abstract: The hierarchical arrays of mesoscale to nanoscale fibrillar structures on a gecko's foot enable the animal to climb surfaces of varying roughness. Adhesion force between the fibrillar structures and various surfaces is maximized after the gecko drags its foot in one direction, which has also been demonstrated to improve the adhesion forces of artificial fibrillar arrays. Essential conditions that influence the magnitude of these interactions include the lateral distance traveled and velocity between the contacting surfaces, as well as the velocity at which the two surfaces are subsequently separated. These parameters have, however, not been systematically investigated to assess the adhesion properties of artificial adhesives. We introduce a systematic study that investigates these conditions using a scanning probe microscope to measure the adhesion forces of artificial adhesives through a process that mimics the mechanism by which a gecko climbs. The measured adhesion response was different for arrays of shorter and longer fibrils. These results from 9000 independent measurements also provide further insight into the dynamics of the interactions between fibrillar arrays and contacting surfaces. These studies establish scanning probe microscopy techniques as a versatile approach for measuring a variety of adhesion properties of artificial fibrillar adhesives.
authors.affiliation: Menrva Lab, School of Engineering Science, ‡School of Engineering Science, and §Department of Chemistry and 4D LABS, Simon Fraser University , 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada.
authors.forename: Yasong
authors.initials: Y
authors.lastname: Li
authors.forename: James H-W
authors.initials: JH
authors.lastname: Zhou
authors.forename: Cheng
authors.initials: C
authors.lastname: Zhang
authors.forename: Carlo
authors.initials: C
authors.lastname: Menon
authors.forename: Byron D
authors.initials: BD
authors.lastname: Gates
mesh_terms: D000268:Adhesiveness; D000269:Adhesives / Q000737:chemistry*; D000818:Animals; D008116:Lizards; D064347:Microscopy, Electrochemical, Scanning; D049329:Nanostructures / Q000737:chemistry / Q000648:ultrastructure; D033081:Shear Strength; D013499:Surface Properties
chemical_list: D000269:Adhesives
keywords: adhesion forces; dry adhesive; nanostructured fibrils; scanning probe microscopy; shear loading