Fabrication and calibration of the magnetized surface. (a) Illustration of the surface’s size parameters and the snapshots from the top view and front view. (b) Fabrication procedures (including six steps). (c) (i) As the magnet moves from right to left, there are five stages that partially/fully contain four main surface morphologies (i.e., original, uniform bending, gradient (+), and gradient (-) regions). (ii)-(iii) experimental records of the five stages and the variation (the number of affected pillars and the position) of different regions. (d)-(f) The effect of different magnetic fields (adjusted by changing h) on the surface’s morphology.