Flexible paramagnetic membranes in fast precessing fields

TL;DR

This paper develops a theoretical framework to analyze the shapes and stresses of elastic paramagnetic membranes under fast precessing magnetic fields, revealing how magnetic parameters influence their conformations.

Contribution

The authors introduce a continuum limit energy model and derive equilibrium equations for paramagnetic membranes subjected to precessing magnetic fields, extending understanding of their shape control.

Findings

Membrane shapes can be tuned by magnetic field parameters.

Shape, energy, and stresses depend mainly on the precession angle.

The framework applies to quasiplanar, cylindrical, and helicoidal geometries.

Abstract

Elastic membranes composed of paramagnetic beads offer the possibility of assembling versatile actuators operated autonomously by external magnetic fields. Here we develop a theoretical framework to study shapes of such paramagnetic membranes under the influence of a fast precessing magnetic field. Their conformations are determined by the competition of the elastic and magnetic energies, arising as a result of their bending and the induced dipolar interactions between nearest neighbors beads. In the harmonic approximation, the elastic energy is quadratic in the surface curvatures. To account for the magnetic energy we introduce a continuum limit energy, quadratic in the projections of the surface tangents onto the precession axis. We derive the Euler-Lagrange equation governing the equilibria of these membranes, as well as the corresponding stresses. We apply this framework to examine paramagnetic membranes with quasiplanar, cylindrical, and helicoidal geometries. In all cases we found that their shape, energy, and stresses can be modified by means of the parameters of the magnetic field, mainly by the angle of precession.