Fig. 3
From: Manipulation of emergent vortices in swarms of magnetic rollers
Potential stiffness manipulation with passive scatterers. a Trapping potential stiffness as a function of number of magnetic rollers comprising the vortex NNi. The number of rollers has a weak influence on the trapping potential. Black solid line is a linear fit. B0 = 5.78 mT, fB = 40 Hz. b Effect of small scatterers (dbead = 150 ± 9 μm) on the vortex trapping potential kp (blue triangles, dashed line marks the value for a pristine vortex). Vortex angular speed ω (inset) decreases with the scatterers number. Black solid lines are linear fits. B0 = 5.78 mT, fB = 40 Hz, NNi = 214. c Pinning of the roller vortex by intermediate bead sizes. Three-fold increase in stiffness of the trapping potential kp for intermediate sized scatterers (red squares, dashed line marks the value for a pristine vortex). The blue region indicates the system response as in b and the green area shows the bead sizes, where even a single scatterer destroys the vortex state. B0 = 7.54 mT, fB = 43 Hz, NNi = 271. Error bars in all panels are the standard deviation of the measurements
