22.2 Wednesday, Jan. 4 These Dead Fish Really Suck: Adhesion performance of the Northern Clingfish WAINWRIGHT, D/K*; KLEINTEICH, T; GORB, S/N; KLEINTEICH, A; SUMMERS, A/P; Duke University; University of Washington, Friday Harbor Marine Lab; University of Kiel, Germany; University of Washington, Friday Harbor Marine Lab; University of Washington, Friday Harbor Marine Lab firstname.lastname@example.org
The Northern Clingfish, Gobeisox maeandricus, lives in the Pacific Northwest’s rocky intertidal zone. Its pelvic fins and parts of the pectoral fins have been fused into a suction-cup-like structure that allows the fish to adhere to varied substrates. Our study compared the adhesive strengths of 22 clingfish and eight manufactured suction cups using eight surfaces of different roughness. All surfaces were made from the same material to control for variables besides roughness. Results show that freshly killed clingfish stuck to all surfaces, while manufactured suction cups were only able to adhere to the three smoothest surfaces. Furthermore, clingfish performance was lowest on the flat surface, with no other pattern observed in surfaces with any roughness. The fish adhered with an average of 39 kPa of adhesive stress or 180 times their body weight over all eight surfaces but suction cups adhered with ~70% more force than clingfish on the three smoothest surfaces. While these results make functional sense, they do not fit with what we know about suction adhesion’s poor performance on rough surfaces. Scanning electron microscopy shows the presence of 0.3 micrometer diameter hair-like structures on the cling. These hairs, or microvilli, allow the generation of Van der Waals forces and enhance the fish’s adhesion to rough surfaces. Van der Waals forces would increase friction of the cling, providing resistance to slipping and buckling, while microvilli would also increase the sealing ability of the suction disc by conforming to uneven substrates.