Generalized Archimedes' principle in active fluids

Nitzan Razin; Raphael Voituriez; Jens Elgeti; Nir S. Gov

doi:10.1103/physreve.96.032606

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arXiv · 1703.07359

Generalized Archimedes' principle in active fluids

Nitzan Razin·Raphael Voituriez·Jens Elgeti·Nir S. Gov

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Abstract

We show how a gradient in the motility properties of non-interacting point-like active particles can cause a pressure gradient that pushes a large inert object. We calculate the force on an object inside a system of active particles with position dependent motion parameters, in one and two dimensions, and show that a modified Archimedes' principle is satisfied. We characterize the system, both in terms of the model parameters and in terms of experimentally measurable quantities: the spatial profiles of the density, velocity and pressure. This theoretical analysis is motivated by recent experiments, which showed that the nucleus of a mouse oocyte (immature egg cell) moves from the cortex to the center due to a gradient of activity of vesicles propelled by molecular motors; it more generally applies to artificial systems of controlled localized activity.

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Nitzan Razin, Raphael Voituriez, Jens Elgeti, Nir S. Gov. 2017-09-30. Generalized Archimedes' principle in active fluids. https://doi.org/10.1103/physreve.96.032606

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