Figure 2.

(a) Schematic of the assembly of the confined chamber. The glass plates on both top and bottom were coated by the asymmetric micro-scales. The radius of the hydrogel particle was R = 0.35 mm and the height of the spacer was h = 0.4 mm. (b) Schematic of experimental setup, where the confined chamber was immersed in Tween 20 solution and exposed to an alternating magnetic field (AMF) to achieve heating. (c) Micro-patterns coated on the glass plates with the scale bar equal to 5 mm. (d) Schematic of the geometry of the ratchet-shaped surface micropatterns. The geometry of the patterns are characterized by the tilt angle θ and distance λ. (e) SEM image of the surface micropatterns with the scale bar equal to 100 μm.