title: Stick-slip friction of gecko-mimetic flaps on smooth and rough surfaces.
abstract: The discovery and understanding of gecko 'frictional-adhesion' adhering and climbing mechanism has allowed researchers to mimic and create gecko-inspired adhesives. A few experimental and theoretical approaches have been taken to understand the effect of surface roughness on synthetic adhesive performance, and the implications of stick-slip friction during shearing. This work extends previous studies by using a modified surface forces apparatus to quantitatively measure and model frictional forces between arrays of polydimethylsiloxane gecko footpad-mimetic tilted microflaps against smooth and rough glass surfaces. Constant attachments and detachments occur between the surfaces during shearing, as described by an avalanche model. These detachments ultimately result in failure of the adhesion interface and have been characterized in this study. Stick-slip friction disappears with increasing velocity when the flaps are sheared against a smooth silica surface; however, stick-slip was always present at all velocities and loads tested when shearing the flaps against rough glass surfaces. These results demonstrate the significance of pre-load, shearing velocity, shearing distances, commensurability and shearing direction of gecko-mimetic adhesives and provide us a simple model for analysing and/or designing such systems.
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Saurabh
authors.initials: S
authors.lastname: Das
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Cadirov
authors.affiliation: Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Sathya
authors.initials: S
authors.lastname: Chary
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Yair
authors.initials: Y
authors.lastname: Kaufman
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Jack
authors.initials: J
authors.lastname: Hogan
authors.affiliation: Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106, USA turner@engineering.ucsb.edu.
authors.forename: Kimberly L
authors.initials: KL
authors.lastname: Turner
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA jacob@engineering.ucsb.edu.
authors.forename: Jacob N
authors.initials: JN
authors.lastname: Israelachvili
mesh_terms: D000268:Adhesiveness; D000269:Adhesives; D000818:Animals; D001696:Biomechanical Phenomena; D032701:Biomimetics; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D017276:Friction; D005898:Glass; D008116:Lizards / Q000502:physiology*; D008422:Materials Testing; D033081:Shear Strength; D012822:Silicon Dioxide / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D000269:Adhesives; D004129:Dimethylpolysiloxanes; C013830:baysilon; D012822:Silicon Dioxide
keywords: gecko-mimetic; rough surface friction; stick–slip friction