The Moses effect enables remote control of self-propulsion of a diamagnetic rotator

The experimental possibility of driving a floating self-propelled rotator by using the Moses effect is demonstrated. A steady magnetic field with a magnitude on the order of B ≅ 0·5 T formed the near-surface dip with a depth of c. 30 μm and lateral dimension of 5 mm, which attracted the floating, millimeter-scaled rotator, made from a polymer tubing filled by camphor and driven by the soluto-capillary Marangoni flows. The Marangoni flows driving the rotator are due to the dissolution of camphor. The Moses effect did not influence the angular velocity of the rotator. The characteristic time span of the rotation was established on the order of a dozen of hours. The longer rotators decrease their initial angular velocity slower. The qualitative analysis of the energy dissipation under rotation is provided. The model is qualitatively supported by the experimental data. The rotator may be exploited as a robotic propulsion unit and also for micro-generation of electrical power.