Transition from turbulent to coherent flows in confined three-dimensional active fluids

TL;DR

This paper demonstrates how active isotropic fluids made of microtubules and motors can autonomously generate and control flow in long 3D channels, transitioning from turbulence to coherence.

Contribution

It reveals the transition mechanism from turbulent to coherent flows in 3D active fluids and links it to microtubule bundle structure and channel geometry.

Findings

Active isotropic fluids flow autonomously in 3D channels.

Flow transition correlates with microtubule bundle order.

Flow control is achieved via channel profile and bundle structure.

Abstract

Transport of fluid through a pipe is essential for the operation of macroscale machines and microfluidic devices. Conventional fluids only flow in response to external pressure. We demonstrate that an active isotropic fluid, comprised of microtubules and molecular motors, autonomously flows through meter-long three-dimensional channels. We establish control over the magnitude, velocity profile and direction of the self-organized flows, and correlate these to the structure of the extensile microtubule bundles. The inherently three-dimensional transition from bulk-turbulent to confined-coherent flows occurs concomitantly with a transition in the bundle orientational order near the surface, and is controlled by a scale-invariant criterion related to the channel profile. The non-equilibrium transition of confined isotropic active fluids can be used to engineer self-organized soft machines.