Göttingen University Researchers Part of Team Detecting Magnus Effect at Microscopic Scale

Detecting Magnus Effect: You have undoubtedly witnessed the “Magnus effect” in action, whether or not you are familiar with the phrase. It occurs when a spinning ball, such as one used in baseball, cricket, or football, veers off course from its anticipated trajectory, frequently surprising the opposing team. The idea can also be applied in engineering, such as when using a “Flettner rotor” to propel specific kinds of ships or aircraft.

Scientists have now established that the Magnus effect also occurs at the microscopic level, where its effects can occasionally become very important. This was experimentally discovered by a team at the University of Konstanz, and the underlying science has been clarified by a team at the University of Göttingen. These discoveries might be applied to the creation of novel methods for the exact movement and control of minuscule particles. Miniature robots that move through the bloodstream and target particular areas of the body are another possible use. In Nature Physics, the findings were published.

Usually, when a rotating object moves through liquid or air, the Magnus effect can be seen. The flow in the area is deformed by the rotation in such a way that there are velocity differences on the opposing sides of the item. This causes a force to act, deflecting the object from moving in a straight line. As the thing gets smaller, the effect gets smaller and smaller. It should virtually vanish for spheres with a diameter of just a few thousandths of a millimetre.

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Göttingen University Researchers Part of Team Detecting Magnus Effect

However, in their research at the University of Konstanz, the team found that when tiny magnetic glass spheres were forced to rotate by a rotating magnetic field and pushed at a constant speed through a viscoelastic fluid, a surprisingly substantial Magnus effect was present. Viscoelastic fluids, such as blood or polymer solutions, differ from water in that they have both fluid and elastic properties. They respond to change with a delay, much like bread dough does when prodded quickly and allowed to slowly return to its previous shape.

Theoretical physicists Dr. Debankur Das and Professor Matthias Krüger from the University of Göttingen’s Institute for Theoretical Physics created a model to demonstrate that it is precisely this delay that causes the Magnus effect at a microscopic level: the surrounding viscoelastic fluid does not immediately follow the rotating sphere and is distorted as a result. Rotation and translation are connected because the distortion spins alongside the sphere and pushes it to one side.

The delay is also noticeable when the rotation abruptly ceases: unlike with a sports ball in the air, the Magnus effect in small spheres in viscoelastic fluids does not immediately vanish but instead persists for a few seconds. That was the key to helping us comprehend what is actually happening, according to Krüger. The result was predicted by our model. The enigma of the Magnus effect at a microscopic level was clarified when we could infer this from the experimental data.