Abstract
In nature, interactions between biopolymers and motor proteins give rise to biologically essential emergent behaviors. 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 behavior 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.
Highlights
Active matter is a state of matter where large-scale dynamical structures emerge from the interaction of individual active components each driven by their own internal energy source
A well investigated class of such systems comprises active nematics[1,2] where individual elongated components selforganize into a dynamic state with spatiotemporal chaos with topological defects a behavior known as active turbulence.[3−10] Several experimental and theoretical model systems have been developed to study networks of cytoskeletal filaments and motor proteins fueled by ATP.[11−13] A remarkable example is the emergent behavior in 2D observed in mixtures of microtubules and kinesin motors arranged in bundles by a depletion agent pioneered by Sanchez et al.[12]
We experimentally investigate the dynamics of an active nematic, confined in a long rectangular channel of size 30 mm × 1.5 mm × 100 μm
Summary
Active matter is a state of matter where large-scale dynamical structures emerge from the interaction of individual active components each driven by their own internal energy source. A well investigated class of such systems comprises active nematics[1,2] where individual elongated components selforganize into a dynamic state with spatiotemporal chaos with topological defects a behavior known as active turbulence.[3−10] Several experimental and theoretical model systems have been developed to study networks of cytoskeletal filaments and motor proteins fueled by ATP.[11−13] A remarkable example is the emergent behavior in 2D observed in mixtures of microtubules and kinesin motors arranged in bundles by a depletion agent pioneered by Sanchez et al.[12] Internally generated spatiotemporally chaotic flows at the millimeter scale were observed that persisted as long as ATP was available. With stochastic simulations and a quantitative theory that describes the wrinkling instability
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