Figure 1

Topographical and physicochemical features of titania nanosurfaces (A) Representative scanning electron microscope (SEM) images of titanium sheet with smooth (SM), micro-roughened (MR), and nano-roughened (NR) 1 and 2 surfaces. The histogram indicates spike density evaluated by counting the vertices per unit micron area on the MR, NR1, and NR2 surface. (B) Representative birds-eye views (upper panels) and vertical roughness parameters (lower histograms) such as Sa and Sp, determined by a laser microscope, (C) water contact angles determined by a sessile drop method, and (D) FTIR spectra of each type of surfaces. Yellow arrowheads, arrows, and double arrows in (A) high magnification SEM images indicate sharp ridges on the MR titanium surface and multiple nanospikes on NR1 and NR2 titania surfaces, respectively. Black arrows in (D) FTIR spectra indicate the peak of hydroxyl groups (-OH). Data presented as mean ± standard deviation (SD; N = 3). Different letters indicate statistically significant differences (P < 0.05; Tukey’s honestly significant difference [HSD] test). Sa, arithmetical mean height; Sp, maximum pit height; FTIR, Fourier transform infrared. Note that the NR1 and NR2 surfaces showed dense nanospikes (A and B), superhydrophilicity (C), and the presence of hydroxyl groups, consistent with a previous report ²⁷.