Magnetic Levitation Stabilized by Streaming Fluid Flows

TL;DR

This paper reveals that a simple magnetic stirrer can passively levitate a small magnet through fluid flow-induced stabilization, offering new insights into magnetic levitation and potential microfluidic applications.

Contribution

It introduces a passive magnetic levitation method using a standard laboratory stirrer, supported by a mechanical model and flow analysis, expanding the understanding of fluid-driven stabilization.

Findings

Flea magnet levitates indefinitely with fluid flow.

Waggling motion induces recirculating flows that stabilize the magnet.

The model accurately predicts the onset and motion of levitation.

Abstract

We demonstrate that the ubiquitous laboratory magnetic stirrer provides a simple passive method of magnetic levitation, in which the so-called `flea' levitates indefinitely. We study the onset of levitation and quantify the flea's motion (a combination of vertical oscillation, spinning and "waggling"), finding excellent agreement with a mechanical analytical model. The waggling motion drives recirculating flow, producing a centripetal reaction force that stabilises the flea. Our findings have implications for the locomotion of artificial swimmers, for the development of bidirectional microfluidic pumps and provide an alternative to sophisticated commercial levitators.