Ultra-soft liquid-ferrofluid interfaces

TL;DR

This paper demonstrates how magnetic forces can create ultra-soft, highly deformable liquid-liquid interfaces with tunable elasticity and viscosity, enabling new microfluidic and biological applications.

Contribution

It introduces a method to produce ultra-soft liquid-ferrofluid interfaces with nonlinear elasticity and adjustable viscous properties using magnetic fields.

Findings

Interfaces exhibit apparent elasticity of 2-10 kPa.

Magnetic pressure balances viscous and Laplace pressures.

Interfaces can be shaped arbitrarily and are highly deformable.

Abstract

Soft interfaces are ubiquitous in nature, governing quintessential hydrodynamics functions, like lubrication, stability and cargo transport. It is shown here how a magnetic force field at a magnetic-nonmagnetic fluid interface results in an ultra-soft interface with nonlinear elasticity and tunable viscous shear properties. The balance between magnetic pressure, viscous stress and Laplace pressure results in a deformed and stable liquid-in-liquid tube with apparent elasticity in the range 2 kPa -10 kPa, possibly extended by a proper choice of liquid properties. Such highly deformable liquid-liquid interfaces of arbitrary shape with vanishing viscous shear open doors to unique microfluidic phenomena, biomaterial flows and complex biosystems mimicking.