Instability of the origami of a ferrofluid drop in a magnetic field

TL;DR

This paper investigates the stability of a ferrofluid drop wrapped by an elastic membrane under magnetic fields, revealing an overturning instability driven by magnetic and gravitational forces, with implications for magnetic capillary origami.

Contribution

It introduces the first analysis of the instability in magnetic capillary origami, combining experimental observations with theoretical modeling of magnetic, elastic, and capillary effects.

Findings

Identified an overturning instability at a critical magnetic field.

Demonstrated the interplay of magnetic and gravitational energies in the instability.

Discussed effects of elasticity and capillarity on the behavior.

Abstract

Capillary origami is the wrapping of an usual fluid drop by a planar elastic membrane due to the interplay between capillary and elastic forces. Here, we use a drop of magnetic fluid whose shape is known to strongly depend on an applied magnetic field. We study the quasi-static and dynamical behaviors of such a magnetic capillary origami. We report the observation of an overturning instability that the origami undergoes at a critical magnetic field. This instability is triggered by an interplay between magnetic and gravitational energies in agreement with the theory presented here. Additional effects of elasticity and capillarity on this instability are also discussed.