Propelling magnetic colloidal carpets on a periodic structured landscape

Abstract

Microswimmers are artificial microscopic entities able to propel in viscous fluids and have the ability to perform tasks at the microscale. This capacity allows to impact many scientific areas such as micromanipulation, lab-on-a-chip devices or targeted drug delivery. In this study, optical video microscopy was used to examine propelled paramagnetic colloidal carpets. First, previous results were reproduced by sliding carpets on top of a flat substrate. In order to investigate more complex situations as the one occurring in natural systems, a different substrate was used. We have slid carpets on top of a periodic structured landscape, namely a two-dimensional colloidal crystal, composed of silica particles. We observe the emergence of novel phenomena when external and time dependent magnetic fields are applied over a colloidal paramagnetic carpet driven across a periodic structured landscape. Stair-like trajectories, periodic oscillations and spontaneous reorientations of the carpet were observed. Also, the comparison of the average speed of the carpet on top of a flat substrate and on a patterned substrate is reported