Meeting Abstract

48.6  Monday, Jan. 5  Underwater gecko feet – how clingfish and snailfish adhere to wet surfaces SUMMERS, A.P.*; GORB, S.; UC Irvine; University of Kiehl asummers@uci.edu

Clingfishes (Gobiesocidae) and snailfishes (Liparidae) have independently evolved, ventral suction disks that they use to adhere to substrates with unpredictable surface characteristics. Adhesion is completely underwater and appears largely mediated by suction (see Maie et al. this meeting). In both groups of fishes there are regions of the suction disc covered in papillae: in the clingfishes these regions are around the edges of the disk and in the snailfish they are arranged in chevrons in the middle of the disc. Examination of these papillae with cryo and conventional SEM reveals them to be islands of densely packed simple rod like structures 300nm in diameter and 3000-4000nm in length. There is some evidence that that these are hierarchical structures with the small terminal tips emanating from larger rods 3000nm in diameter and 15um long. To test the adhesive properties of these nanostructured arrays we used a microscale material testing system in a chamber filled with artificial seawater. We pressed a sapphire ball into papillae from 4 clingfish and 2 snailfishes and found that the adhesive forces were up to 70% of the force used to press the ball into the papilla. We conclude that, much like the spatulate hairs on the foot of a gecko or insect, these rods are making very close contact with the substrate allowing van der Waals forces to play a role in adhesion. The viscosity of water also pays a role, contributing substantially to adhesions as well.