Fabrication and shape deformation of patterned hydrogels. (a) A patterned silica wafer with microchannel structures (width: 800 μm; spacing: 800 μm; height: 100 μm) was fabricated by photolithography. (b) A SA pregel solution was casted onto the silica wafer and dried at room temperature (c). (d) The patterned hydrogel on the silica wafer was first immersed into a 0.1 M CaCl2 solution for 10 min, then cut with microchannels in different orientations after peeling off from the patterned silica wafer (e), and finally immersed into a 0.1 M CaCl2 solution for another 24 h (f). (g) and (h) show the top view and side view of the patterned hydrogel sheet. (i)-(n) show the 3D deformation of the resulting hydrogel sheets with tube-curling structures, helical structures, and rolling structures in the 0.1 M CaCl2 solution and water for 24 h, respectively, with alignment of microchannels at angles θ = 0° (i, l), 45° (j, m), and 90° (k, n) correspondingly. The scale bars are 0.5 cm.