Figure 3
a Evaporation-induced ring formation technique for sphere-on-flat geometry, b AFM height image of highly ordered MWNT rings at the region in between ×1 and ×2 as shown in Fig. 3a. c The close-up AFM topographical images marked in b. The image size is 50 × 50 μm2 in b, and 5.8 × 5.8 μm2 in c. The z scale is 50 nm for all images [52]