Transportation, dispersion and ordering of dense colloidal assemblies by magnetic interfacial rotaphoresis†
Colloidal systems exhibit intriguing assembly phenomena with impact in a wide variety of technological fields. The use of magnetically responsive colloids allows one to exploit interactions with an anisotropic dipolar nature. Here, we reveal magnetic interfacial rotaphoresis – a magnetically-induced rotational excitation that imposes a translational motion on colloids by a strong interaction with a solid–liquid interface – as a means to transport, disperse, and order dense colloidal assemblies. By balancing magnetic dipolar and hydrodynamic interactions at a symmetry-breaking interface, rotaphoresis effectuates a translational dispersive motion of the colloids and surprisingly transforms large and dense multilayer assemblies into single-particle layers with quasi-hexagonal ordering within seconds and with velocities of mm s−1. We demonstrate the application of interfacial rotaphoresis to enhance molecular target capture, showing an increase of the molecular capture rate by more than an order of magnitude.