# Suppressing Interfacial Instability of Immiscible Liquid‐in‐Liquid Flow Using Magnetic Forces

## TL;DR

This paper shows how magnetic forces can stabilize liquid jets, preventing instability and enabling new applications in chemistry and biology.

## Contribution

A novel method using magnetic forces to suppress interfacial instability in immiscible liquid flows is introduced.

## Key findings

- Magnetic forces applied via a ferrofluid envelope can suppress interfacial instability in liquid jets.
- Instability can be externally controlled by adjusting magnetic force strength.
- The system allows for new applications in flow chemistry and transport of biological materials.

## Abstract

Interfacial instability prevents a liquid jet from flowing indefinitely within air or another liquid. An approach is presented here to suppress interfacial instability by means of a magnetic force applied by a ferrofluid envelope around the jet. The stability limits occurring within a large parameter window are experimentally investigated with length and time scales governed by the magnetic Bond number. Instabilities can be generated by modifying the magnetic force strength externally, with a remarkable return to stability when removing the external stimulus. The current system with soft and slippery interfaces enables investigations of flow systems beyond the limits of standard hydrodynamics allowing for exciting applications in flow chemistry, interface engineering and transport of biological materials.

This paper investigates the magnetic stabilization of an immiscible inner liquid surrounded by a ferrofluid sheath. Suppressing instabilities and thermomagnetic manipulation of the inner liquid are shown. The results provide insight into Ferrohydrodynamic jet control for applications of industrial, pharmaceutical and physiological relevance.