Asymmetric fluid flow in helical pipes inspired by shark intestines

The intestines of sharks and rays form helical structures. A recent study suggests that one function of these structures is to induce asymmetric flow down the digestive tract, favoring the movement of fluid from anterior to posterior. In this work, our goal is to achieve asymmetric flow in well-characterized, deformable, helical structures and to understand the underlying physics, which involves coupling between the flowing fluid and the solid structure. We designed and 3D-printed biomimetic models of helical shark intestines—tubular pipes with a thin inner helical structure—that are characterized by a small number of parameters: the inner and outer radii of the helix, the helical pitch, and the number of turns.