Investigations into 3D-printed nautiloid-inspired pressure housings

Area of Science:

• Biomimetics and Bio-inspired Engineering
• Marine Robotics and Deep-Sea Technology
• Paleontology and Evolutionary Biology

Background:

• The chambered nautilus shell functions as a natural one-atmosphere pressure housing, enabling neutral buoyancy at deep-sea depths (200-800 m).
• Extinct ammonoids, relatives of the nautilus, likely inhabited similar depths, possessing complex shell morphologies that may offer insights into pressure tolerance.
• Conventional deep-sea robotics often utilize simple geometric shapes like spheres and cylinders for pressure housings due to their optimal surface area-to-volume ratio and manufacturability.

Purpose of the Study:

• To model and empirically test 3D-printed, bio-inspired pressure housings based on the *Nautilus pompilius* shell for deep-sea applications.
• To compare the pressure tolerance of nautilus-inspired designs against conventional spherical models with similar wall thicknesses and implodable volumes.
• To evaluate the potential of additive manufacturing for creating and testing complex, bio-inspired geometries for subsea robotic housings.

Main Methods:

• High-resolution stereolithography 3D printing was employed to fabricate bio-inspired pressure housings.
• Designs were modeled after the shells of *Nautilus pompilius*, including internal supports mimicking septal walls (concave and convex configurations).
• Empirical pressure testing was conducted to compare the performance of nautilus-inspired models against 3D-printed spherical controls.

Main Results:

• Nautilus-inspired models with internal supports demonstrated higher pressure tolerance than hollow models.
• However, neither the concave nor convex nautilus-inspired designs outperformed spherical models with equivalent outer-wall thickness.
• Additive manufacturing proved effective for producing and testing complex geometric pressure housings.

Conclusions:

• While simple spheres currently offer superior pressure tolerance in deep-sea applications compared to the tested nautilus-inspired designs, the study validates additive manufacturing as a viable method for creating and testing complex bio-inspired pressure housings.
• This research provides a novel approach for empirically assessing the depth tolerances of extinct cephalopod shell morphologies, contributing to both engineering and evolutionary biology.
• The findings pave the way for future development of advanced bio-inspired pressure vessels for subsea exploration and robotics.