Three-dimensional reconfigurable magnetic microswarms with boundary-transcending capabilities.

Synchronizing a global rotating magnetic field with a co-rotating local gradient generates enhanced rotating fields that drive 3D movement of magnetic microparticles across solid-liquid and liquid-air boundaries. The resulting tornado-like microswarms reversibly switch between 2D and 3D patterns and between single and dual collectives, trap and transport cargo via convection flows, and carried levamisole vertically across intermediate barriers to induce localized arrhythmic beating of cardiomyocytes. The work points to uses in biological mechanism discovery and drug screening.