Meeting Abstract
Cephalopods can hold onto non-porous substrates with high force for long periods of time while expending minimal muscular energy and are thus particularly inspiring models for soft robots. This is accomplished in part by inducing vacuum with their hydrostatic suckers. In this study, we test the hypothesis that infundibular grooves increase the shear force of suckers by distributing the vacuum of the acetabular chamber to the interface between the infundibulum and the target surface. We show that morphological parameters (shape, size, roughness, direction, and spacing) of grooves and denticles on the infundibulum affect the load-bearing capacity of suckers. To isolate effects of specific parameters, we used 3D printed molds and soft silicone rubbers to fabricate an array of artificial suckers with initial design inspiration taken from Octopus vulgaris. The load capacity of the suckers with an applied internal vacuum of 90kPa was measured for loading angles ranging from 0º (shear) to 90º (normal) using a custom fixture in a tensile testing machine. The load capacity was recorded as the maximal force exerted before failure, (releasing the target surface). Results showed sensitivity to the presence of grooves and denticles in the shear direction but not the normal direction. The highest capacity for designs with a 2 cm wide infundibular disc was 1.7 kg in shear and 1.75kg in the normal direction. Compared to plain suckers with smooth infundibula resembling commercial suction cups, radial grooves increased the shear load capacity of a sucker up to 21% and concentric grooves decreased it up to 31%. The results of this study can be used to better understand the morphological function of suckers and inform the design of artificial soft robotic grasping mechanisms for improved load bearing capacity, dexterity, and energy efficiency.
