2.4. Characterization. The air layer on the lotus layer wascharacterized by a Nikon C2 laser scanning confocal microscope(Nikon Co., Tokyo, Japan). The micro/nanostructures on the lotusand the aluminum plate were obtained by scanning electronmicroscopy (SEM, JEOL, JSM-7500F, Japan). The air layer on thealuminum plate by the laser etching method could be directlyobserved and measured by the optical microscope (Vision Engineering Co., U.K.) that was coupled to a charge-coupled device camera.