Abstract
Inspired by the actomyosin cortex in biological cells, we investigate the spatiotemporal dynamics of a model describing a contractile active polar fluid sandwiched between two external media. The external media impose frictional forces at the interface with the active fluid. The fluid is driven by a spatially-homogeneous activity measuring the strength of the active stress that is generated by processes consuming a chemical fuel. We observe that as the activity is increased over two orders of magnitude the active polar fluid first shows spontaneous flow transition followed by transition to oscillatory dynamics with traveling waves and traveling vortices in the flow field. In the flow-tumbling regime, the active polar fluid also shows transition to spatiotemporal chaos at sufficiently large activities. These results demonstrate that level of activity alone can be used to tune the operating point of actomyosin layers with qualitatively different spatiotemporal dynamics.
Highlights
Inspired by the actomyosin cortex in biological cells, we investigate the spatiotemporal dynamics of a model describing a contractile active polar fluid sandwiched between two external media
Energy consumption in active matter leads to chaotic motion in bacterial suspensions[4], cell polarity inducing flows in the actomyosin cortex of single cell C. elegans embryos[7,8,9], and traveling waves and swirling motion of actin filaments in vitro[10]
These transitions are due to the nonlinearities in the hydrodynamic equations that are neglected in the linearized regime
Summary
Inspired by the actomyosin cortex in biological cells, we investigate the spatiotemporal dynamics of a model describing a contractile active polar fluid sandwiched between two external media. Biological systems like cytoskeletal filaments[1,2,3], bacterial suspensions[4], cell aggregates and tissues[4], and flocks of birds[5] are examples of active living matter[2,4,6] Such active systems consist of a set of interacting agents that exhibit coordinated motion or flows induced by energy consumption[4,6]. Energy consumption in active matter leads to chaotic motion in bacterial suspensions[4], cell polarity inducing flows in the actomyosin cortex of single cell C. elegans embryos[7,8,9], and traveling waves and swirling motion of actin filaments in vitro[10]. By using linearized hydrodynamical equations, instabilities of spatially-homogeneous steady states have been deciphered[2,17,18,19,20]
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