Asymmetric Fluid Flow in Helical Pipes Inspired by Shark Intestines

TL;DR

This study designs and tests 3D-printed biomimetic shark intestine models to explore how interior helical structures influence asymmetric fluid flow, revealing significant amplification when using deformable materials, with potential applications in various fluidic systems.

Contribution

The paper introduces biomimetic, 3D-printed shark intestine models to analyze flow asymmetry, demonstrating how interior helices and material deformability enhance flow control beyond traditional designs.

Findings

Deformable models amplify flow asymmetry 7-fold compared to rigid ones.

Biomimetic models achieve flow asymmetry comparable to Tesla valves.

Interior helical parameters significantly influence flow directionality.

Abstract

Unlike human intestines, which are long, hollow tubes, the intestines of sharks and rays contain interior helical structures surrounding a cylindrical hole. One function of these structures may be to create asymmetric flow, favoring passage of fluid down the digestive tract, from anterior to posterior. Here, we design and 3D print biomimetic models of shark intestines, in both rigid and deformable materials. We use the rigid models to test which physical parameters of the interior helices (the pitch, the hole radius, the tilt angle, and the number of turns) yield the largest flow asymmetries. These asymmetries exceed those of traditional Tesla valves, structures specifically designed to create flow asymmetry without any moving parts. When we print the biomimetic models in elastomeric materials so that flow can couple to the structure's shape, flow asymmetry is significantly amplified; it is 7-fold larger in deformable structures than in rigid structures. Last, we 3D-print deformable versions of the intestine of a dogfish shark, based on a tomogram of a biological sample. This biomimic produces flow asymmetry comparable to traditional Tesla valves. The ability to influence the direction of a flow through a structure has applications in biological tissues and artificial devices across many scales, from large industrial pipelines to small microfluidic devices.