Figure  3b,c shows approximately 700-nm-thick TiO2 nanotube arrays. Figure 2 FESEM images of a Ti surface patterned with protruding dots and anodized for 1 min. The Ti surface was anodized at 60 V in an ethylene glycol solution containing 0.5 wt% NH4F.

(a) × 2,000 magnification, (b) × 15,000 magnification, (c) × 15,000 magnification, and (d) × 50,000 magnification. Figure 3 FESEM images of a Ti surface patterned with protruding dots and anodized for 2 min. The Ti surface was anodized at 60 V in an ethylene glycol solution containing 0.5 wt% NH4F. (a) × 1,000 magnification, (b) × 5,000 magnification, (c) × 15,000 magnification, and (d) × 50,000 magnification. Figure 4 FESEM images of a Ti surface patterned with protruding dots selleck kinase inhibitor and anodized for 4 min. The Ti surface was anodized at 60 V in an ethylene glycol solution containing 0.5 wt% NH4F. (a) × 1,000 magnification, (b) × 5,000 magnification, (c) × 10,000 PLX3397 research buy magnification, and (d) × 45,000 magnification. Figure 5 FESEM images of a Ti surface patterned with protruding dots and anodized for 5 min. The Ti surface was anodized at 60 V in an ethylene glycol solution containing 0.5 wt% NH4F. (a) × 1,000 magnification,

(b) × 4,000 magnification, (c) × 10,000 magnification, and (d) × 40,000 magnification. Figure 6 FESEM images of a Ti surface patterned with protruding dots and anodized for 7 min. The Ti surface was anodized at 60 V in an ethylene glycol solution containing 0.5 wt% NH4F. (a) × 1,000 magnification, (b) × 4,000 magnification, (c) × 10,000 magnification, and (d) × 50,000

magnification. When the anodization time was increased to 4 min, beautiful TiO2 micro-flowers started to bloom. The arrays of TiO2 micro-flowers are shown in Figure  4a. The thickness of each TiO2 nanotube is linearly correlated with the extent to which the TiO2 micro-flowers bloom. The blooming of the TiO2 micro-flowers is due to the severe cleavages of the TiO2 nanotubes between the top areas and the side walls of the protruding dots. As the anodization time was increased to 5 min, core bundles of nanotubes in TiO2 micro-flowers were slightly bent in random directions, as shown in Figure  5a,b,c,d. This occurred due to the difference in the growing speed of each TiO2 nanotube in the CHIR-99021 supplier core bundles. The measured thickness of the TiO2 nanotubes in Figure  5d was 2 μm. As the anodization time was increased to 7 min, the center area of the core nanotube bundles in the TiO2 micro-flowers was removed, as shown in Figure  6a,b,c. Figure  6d shows the cleavage areas of the TiO2 micro-flowers. The structure of the TiO2 nanotubes in that area collapsed due to the additional etching by the fluorine ions in the anodizing solution. Figure  7 shows the schematic mechanism involved in the blooming of the TiO2 micro-flowers. One of the Ti-protruding dots from the photolithography and RIE process shows a cylindrical shape in Figure  7a.