Stepwise magnetic self-assembly of micropillar arrays with long range order

Magnetically responsive microtextured surfaces have the advantage of being controlled remotely (i.e., no contact is required) at ambient conditions and short response times. Previously, synchronized bending or twisting actuations of micropillar arrays were demonstrated by programming the arrangement of the magnetic particles and by employing anisotropic micropillar geometry. In this case, magnetic particles are included in a polymer matrix at low concentrations to avoid magnetic interference and thereby achieve synchronized actuation. Researchers from Inha University (Jeong Eun Park and Jeong Jae (JJ) Wie), Air Force Research Laboratory (Augustine Urbas and Zahyun Ku), and Lawrence Livermore National Laboratory (Sei Jin Park) recently reported an opposite strategy to induce magnetic self-assembly of micropillar arrays. Highly concentrated magnetic micropillars act as micromagnets and collectively assemble with neighboring pillars under an applied magnetic field. For facile actuation, flexible rubber is utilized for pillar-base while relatively rigid and magnetically responsive pillar-tops undergo the magnetic assembly. As the pillar-base is magnetically inert and fixed to substrate, self-assembly of periodically arranged micropillars can repeat reversible and reproducible assembly and recovery by modulating the external magnetic field.