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