Investigations into 3D-printed nautiloid-inspired pressure housings

Abstract

Abstract The shell of the chambered nautilus is one of the few examples in nature of a biologically derived one-atmosphere pressure housing, which the animal uses to maintain neutral buoyancy via a series of sealed chambers. Extant species such as Nautilus pompilius live at depths from 200 to 800 m, and similar depth ranges have been hypothesized for their hyper diverse but extinct relatives, the ammonoids. Given the evolutionary success of these molluscan clades, their complex shell morphologies may reveal pressure-tolerant geometries comparable to the ‘ideal’ ones currently used in deep-sea marine robotics: simple spheres and cylinders, which have minimized surface area to volume ratio and easier manufacturability. We modeled and empirically tested 3D-printed bioinspired pressure housings for deep-sea applications using high resolution stereolithography 3D printing. These designs were modeled on the shells of N. pompilius and were compared to conventional 3D-printed spheres with similar wall thicknesses and implodable volumes. Two nautilus-inspired models with internal supports designed after their septal walls (one concave, one convex) had a higher-pressure tolerance compared to hollow models, but none outperformed spherical models with the same outer-wall thickness. Although spheres outperform the nautilus-inspired housings, the methods developed here show that pressure housings with complex geometries can be printed by additive manufacturing and empirically tested. From a biological perspective, this method can be a new tool for empirically testing viable depth tolerances for extinct coiled cephalopod morphologies.