Controllable directional deformation of micro-pillars actuated by a magnetic field

It is well known that special surface functions can be designed by varying the topography of micro-structured surfaces. In the present paper, a simple but effective method to control the directional deformation of micro-pillar arrays is proposed through a rotating magnetic field. The large deformation of each micro-pillar can be tuned by the magnetic field strength and direction. When the magnetic field strength is fixed, the deformation direction of micro-pillars is controlled by the direction of magnetic field. When the direction of magnetic field is determined, the deflection of micro-pillars increases with the increase of magnetic field strength. Based on the principle of minimum potential energy, a theoretical model is further established to disclose such a large deformation mechanism of micro-pillars. The theoretically predicted morphology of deformed pillars is well consistent with the experimental results. The present experimental technique and theoretical results should be useful for the design and preparation of typical functional surfaces such as reversible adhesion, controllable wettability and directional surface transport.