Analysis of core-shell magnetic micropillars for reconfigurable bending actuation

Magnetic micropillars that can reversibly and dynamically bend actuated by external magnetic field have been increasingly studied for functional interfacial engineering and soft-robotics applications. Existing micropillars are usually fabricated by solidifying magnetic media (most often nanoparticles) premixed within elastomer solvent, thus the bent configurations of the pillars are fixed upon applying the magnetic stimuli. In this work, we study the fundamental mechanics of the reconfigurable and recyclable bending actuation for the recently proposed liquid-core/solid-shell magnetic micropillars. By dynamically modulating the spatial distribution of the magnetic nanoparticles inside the liquid resin cores of individual micropillars, the bending deformation can be reversibly tuned by near one order magnitude under the same actuation conditions. The regulated bending deformation is achieved by the different distributions of the magnetic actuation force applied on the solid shells of the micropillars. The liquid-core/solid-shell magnetic micropillars reported here provide a generic prototype for reconfigurable and recyclable stimuli-responsive microstructures.