Magnetic Stepwise-Organization of Periodically Arranged Micropillar Arrays

초록

Self-organization of magnetic composites that mimic the collective swarming of natural living creatures has been explored as potential means of accomplishing more complicated tasks. Micron/submicron-scale composite particles can organize into chain-like morphology which allows for directionality of the magnetic response. However, organized shapes and positions could not be reproduced due to unfixed positions of the composite particles. To develop the programmable and reproducible magnetic organization of microscale objects, we introduce periodically arranged micropillar arrays consisting of elastomeric polymer/magnetic particle composites. The magnetic polarities of embedded particles are arranged from S to N pole when an external magnetic field is applied using two permanent magnets. Accordingly, the micropillars act as individual micromagnets where quadrupolar magnetic interactions occur between two vicinal micropillars. As magnetic flux density increases, two vicinal pillar-tops assemble as a pair. At higher magnetic flux density, the two pairwise-assembled micropillars further assemble into a quad-body, and long-range connectivity is ultimately accomplished. We will delve into the mechanisms and governing parameters of this stepwise magnetic-organization via a thorough look into these micropillars consisting of isotropic/anisotropic cross-sections with the directionality of an external magnetic field relative to the geometry of the micropillars.