title: Composition and substrate-dependent strength of the silken attachment discs in spiders.
abstract: Araneomorph spiders have evolved different silks with dissimilar material properties, serving different purposes. The two-compound pyriform secretion is used to glue silk threads to substrates or to other threads. It is applied in distinct patterns, called attachment discs. Although ubiquitously found in spider silk applications and hypothesized to be strong and versatile at low material consumption, the performance of attachment discs on different substrates remains unknown. Here, we analyse the detachment forces and fracture mechanics of the attachment discs spun by five different species on three different substrates, by pulling on the upstream part of the attached thread. Results show that although the adhesion of the pyriform glue is heavily affected by the substrate, even on Teflon it is frequently strong enough to hold the spider's weight. As plant surfaces are often difficult to wet, they are hypothesized to be the major driving force for evolution of the pyriform secretion.
authors.affiliation: Department of Functional Morphology and Biomechanics, University of Kiel, Am Botanischen Garten 1-9, Kiel 24098, Germany Department of Mechanical Engineering, Westphalian Institute for Biomimetics, University of Applied Sciences, Münsterstrasse 265, Bocholt 46397, Germany.
authors.forename: Ingo
authors.initials: I
authors.lastname: Grawe
authors.affiliation: Department of Functional Morphology and Biomechanics, University of Kiel, Am Botanischen Garten 1-9, Kiel 24098, Germany jwolff@zoologie.uni-kiel.de.
authors.forename: Jonas O
authors.initials: JO
authors.lastname: Wolff
authors.affiliation: Department of Functional Morphology and Biomechanics, University of Kiel, Am Botanischen Garten 1-9, Kiel 24098, Germany.
authors.forename: Stanislav N
authors.initials: SN
authors.lastname: Gorb
mesh_terms: D000269:Adhesives; D000818:Animals; D001696:Biomechanical Phenomena; D005260:Female; D005349:Fibroins / Q000737:chemistry*; D008422:Materials Testing; D008853:Microscopy; D011138:Polytetrafluoroethylene / Q000737:chemistry*; D013045:Species Specificity; D013112:Spiders; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D000269:Adhesives; D011138:Polytetrafluoroethylene; D005349:Fibroins
keywords: Araneae; adhesion; compound material; hierarchical structure; silk; tensile test