How many ways a cell can move: the modes of self-propulsion of an active drop

Abstract

Numerous physical models have been proposed to explain how cell motility emerges from internal activity, mostly focused on how crawling motion arises from internal processes. Here we offer a classification of self-propulsion mechanisms based on general physical principles, showing that crawling is not the only way for cells to move on a substrate. We consider a thin drop of active matter on a planar substrate and fully characterize its autonomous motion for all three possible sources of driving: (i) the stresses induced in the bulk by active components, which allow in particular tractionless motion, (ii) the self-propulsion of active components at the substrate, which gives rise to crawling motion, and (iii) a net capillary force, possibly self-generated, and coupled to internal activity. We determine travelling-wave solutions to the lubrication equations as a function of a dimensionless activity parameter for each mode of motion. Numerical simulations are used to characterize the drop motion over a wide range of activity magnitudes, and explicit analytical solutions in excellent agreement with the simulations are derived in the weak-activity regime.

to appear in Soft Matter (2020)

References in corpus (7)

• Spontaneous motion in hierarchically assembled active matter
• Turning bacteria suspensions into a "superfluid"
• A minimal physical model captures the shapes of crawling cells
• Directed transport of active particles over asymmetric energy barriers
• Instabilities and waves in thin films of living fluids
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Cited by in corpus (8)

• Onsager's variational principle in active soft matter
• Optimal transport and control of active drops
• Gradient-dynamics model for liquid drops on elastic substrates
• Fingering Instability of Active Nematic Droplets
• Derivation and analysis of a phase field crystal model for a mixture of active and passive particles
• Symmetry-breaking, motion and bistability of active drops through polarization-surface coupling
• Shapes and dynamic regimes of a polar active fluid droplet under confinement
• What is active wetting?