Transport and Assembly of Magnetic Surface Rotors**

Abstract

This minireview focuses on recent advances with surface magnetic rotors, namely field‐responsive spherical or anisotropic microparticles that translate close to, or are embedded in a confining surface. The application of external magnetic modulations allows these microscopic wheels to be remotely spun and steered while also tuning their interactions and inducing assembly from a collection of disordered, moving units. With optical microscopy one can observe and characterize the complex collective phenomena that emerge in dissipative colloidal systems driven far from equilibrium by external fields. From a technological point of view, magnetic surface rotors envisage implementation into microfluidic devices, and can be used for drug delivery, mixing as well as a model system for biological active matter.

Grain boundary dynamics driven by magnetically induced circulation at the void interface of 2D colloidal crystals

“…This translation is a result of the frictional shear force produced between the particle’s flow field and the surface. Otherwise known as a transverse force, this type of force has implications on structure and transport in collective systems ( 38 – 41 ). In the case of our collective system, the particles rotate parallel to the stationary chamber surface and, therefore, produce this frictional shear force with other in-plane rotating particles.…”

Chiral flow in a binary mixture of two-dimensional active disks

“…For more details on this 3D printing process, please refer to the Supplementary Material file. Consistent rotation of macroscopic particles can be achieved by means of other experimental methods such as imposing external electromagnetic fields [29,30] or by means of shape anisotropy in the particles [31].…”

Chiral flow in a binary mixture of two-dimensional active disks

“…For more details on this 3D printing process, please refer to the Supplementary Material file. Consistent rotation of macroscopic particles can be achieved by means of other experimental methods such as imposing external electromagnetic fields [25,26] or by means of a shape anisotropy in the particles [27].…”