Computational and Experimental Investigation of Batoid Pectoral Fin Biomechanics

Batoids (e.g., stingrays, manta rays, and skates) have garnered significant interest in the underwater robotics community due to their superior swimming efficiency and maneuverability compared to traditional autonomous underwater vehicles (AUVs). Remarkable skeletal structures within their enlarged pectoral fins comprise thousands of rigid cartilaginous “radials” catenated together into long, chain-link “rays,” all surrounded by layers of muscle tissue. Limited efforts have been made, however, to systematically understand the mechanical effect of these muscoloskeletal structures. In this work, we use a combination of computational and experimental techniques to investigate this question. Drawing from X-ray data of three representative species, we first quantify the spatial variations in skeletal structure across the fins. Through finite element simulations, we then relate these geometric variations to corresponding effective material property variations under membrane and bending loading. Due to computational limitations, these numerical simulations cannot evaluate hydrodynamic effects or fluid-structure interaction properties. We therefore developed a skeletonized soft robotic testing platform to empirically evaluate the fins’ hydrodynamic performance. Through this two-pronged numerical/empirical approach, we aim to develop a comprehensive understanding of the relationship between fin morphology and functional swimming performance to inform future next-generation AUV designs.