Electrohydraulic Fields Generated by Active Transport at Tissue Interfaces

TL;DR

This paper develops a unified electrohydraulic framework to understand how ion transport at tissue interfaces generates electric fields, fluid flows, and complex patterns, revealing new mechanisms of biological self-organization.

Contribution

It introduces a comprehensive model coupling electric fields, osmotic pressures, and fluid flows at biological interfaces, highlighting novel electrohydraulic effects and symmetry-breaking phenomena.

Findings

Ion transport acts as a distributed current source generating long-range fields.

External electric fields and internal pumping patterns can produce equivalent effects.

Nonlinear coupling causes isotropic swelling in cell spheroids, explaining experimental observations.

Abstract

Living cells and tissues can generate complex patterns of electric fields and fluid flows which can play important role in physiology. Both, fields and flows are rooted in ion transport across biological interfaces: cell membranes and epithelial cell layers. Here we develop a unified electrohydraulic framework that combines electric fields, osmotic pressures, and fluid flows, emphasising their couplings. We consider an active, permeable interface that drives electrohydraulic fields in the surrounding bulk. We show that spatially heterogeneous ion transport acts as a distributed current source, generating long-range electric fields, osmotic gradients, and fluid flows. Using this framework, we show that patterns of ion pumping at cell and tissue boundaries can simultaneously produce large-scale electric fields and fluid flows due to electrohydraulic coupling. A key insight is that an external electric field and an internal dipolar pumping pattern can be physically equivalent and can generate the same pattern of ion current and fluid flows. The induced dipolar osmotic pressure can drive self-propulsion through bulk osmotic coupling, with a mobility determined by interfacial permeability and system size, a mechanism distinct from classical electrophoresis or electro-osmosis. We further show that for strong fields a new effect emerges. Nonlinear coupling can lead to isotropic swelling of a hollow ball of cells. This can explain recent experiments on epithelial organoids. Finally, we show that feedback between ion transport and resulting electric fields can drive spontaneous symmetry breaking, generating dipolar or multipolar fields and patterns. Our work highlights the importance of electrohydraulic coupling in the emergence in currents and fields in the biological systems.