Heterogeneous magnetic micropillars for regulated bending actuation

Magnetic micropillars that can dynamically and reversibly bend actuated by external magnetic field have been widely studied for surface engineering and micromanipulation applications. However, current micropillars usually exhibit uniform distribution of the magnetic media inside and thus respond essentially the same way to external stimuli. Here we report a new concept and a corresponding experimental technique for heterogeneous magnetic micropillars with the placement of the inside magnetic nanoparticles being precisely controlled. By manipulating the spatial distribution of the magnetic nanoparticles from the base region to the tip region within the micropillars, we show that the actuated bending deformation can be tuned by as large as one order of magnitude under the same actuation condition. The different bending responses are enabled by the resulting different distributions of the local stiffness and the actuation force along the micropillars, in consistent with the fundamental bending principles for cantilever beams. The heterogeneous magnetic micropillars reported here provide a prototype for regulated and on-demand actuations using stimuli-responsive materials/structures. (C) 2020 Elsevier B.V. All rights reserved.