Figure 2.

Fabrication and characterization of the double-layer composite. (a) Schematic and digital image of printing the magnetic basement on a glass plate. (b) Schematic and digital image of printing the middle layer on the magnetic basement. (c) Optical image of an array of double-layer composite. (d) Digital image of a double-layer composite standing on a petal under the guidance of a magnet. (e) Pseudocolor SEM image showing the different layers of the double-layer composite. Purple: the middle layer; brown: the basement layer. (f) Diameter distribution of the double-layer composite. (g) Thickness distribution of the double-layer composite. The scale bars are 5 mm in (a, b), 2 mm in (c, d), and 200 μm in (e).