Wrinkling instability in 3D active nematics

TL;DR

This study investigates the behavior of 3D active nematics composed of microtubules and kinesin motors, revealing a transition from ordered bundles to wrinkling and active turbulence, with insights into the mechanisms and independence of wrinkle wavelength.

Contribution

It provides the first detailed experimental and theoretical analysis of wrinkling instability in 3D active nematics, highlighting the role of kinesin motors and the independence of wrinkle wavelength from ATP concentration.

Findings

Wrinkle wavelength is independent of ATP concentration.

Microtubule bundles transition into a wrinkled 2D ribbon and then to 3D turbulence.

Kinesin motors are crucial for cross-linking and sliding microtubules.

Abstract

In nature interactions between biopolymers and motor proteins give rise to biologically essential emergent behaviours. Besides cytoskeleton mechanics, active nematics arise from such interactions. Here we present a study on 3D active nematics made of microtubules, kinesin motors and depleting agent. It shows a rich behaviour evolving from a nematically ordered space-filling distribution of microtubule bundles toward a flattened and contracted 2D ribbon that undergoes a wrinkling instability and subsequently transitions into a 3D active turbulent state. The wrinkle wavelength is independent of the ATP concentration and our theoretical model describes its relation with the appearance time. We compare the experimental results with a numerical simulation that confirms the key role of kinesin motors in cross-linking and sliding the microtubules. Our results on the active contraction of the network and the independence of wrinkle wavelength on ATP concentration are important steps forward for the understanding of these 3D systems.