E 1010 ion sputter

Difference analysis of bacterial community structure and bacterial load showed no significant differences between film-protected and non-film-protected smartphones, suggesting no obvious influence of screen protective films on microbes on the contacted smartphone surface. Therefore, we employed smartphone protector films as an alternative for scanning electron microscopy (SEM) observation. Smartphone protector films were cut into 1-cm² subareas as SEM specimens. Specimens were fixed in 2.5% glutaraldehyde in phosphate buffer (0.1 M, pH 7.0) for more than 4 h and then rinsed three times in phosphate buffer (0.1 M, pH 7.0) (15 min each time). Then specimens were postfixed with 1% osmium tetroxide (OsO₄) in phosphate buffer (0.1 M, pH 7.0) in a fume hood for 1 to 2 h at room temperature and washed three times in phosphate buffer (0.1 M, pH 7.0) for 15 min at each step. Afterward, specimens were dehydrated in a series of ethanol solutions (50%, 70%, 80%, 90%, 95%, and 100%) for 20 min at each step and incubated with absolute ethanol for 20 min, followed by dehydration in a Hitachi model HCP-2 critical point dryer. The dehydrated sample was coated with gold-palladium in a Hitachi model E-1010 ion sputter for 4 to 5 min and examined using a GeminiSEM 300 field emission scanning electron microscope (Zeiss, Göttingen, Germany).

Difference analysis of bacterial community structure and bacterial load showed no significant differences between film-protected and non-film-protected smartphones, suggesting no obvious influence of screen protective films on microbes on the contacted smartphone surface. Therefore, we employed smartphone protector films as an alternative for scanning electron microscopy (SEM) observation. Smartphone protector films were cut into 1-cm² subareas as SEM specimens. Specimens were fixed in 2.5% glutaraldehyde in phosphate buffer (0.1 M, pH 7.0) for more than 4 h and then rinsed three times in phosphate buffer (0.1 M, pH 7.0) (15 min each time). Then specimens were postfixed with 1% osmium tetroxide (OsO₄) in phosphate buffer (0.1 M, pH 7.0) in a fume hood for 1 to 2 h at room temperature and washed three times in phosphate buffer (0.1 M, pH 7.0) for 15 min at each step. Afterward, specimens were dehydrated in a series of ethanol solutions (50%, 70%, 80%, 90%, 95%, and 100%) for 20 min at each step and incubated with absolute ethanol for 20 min, followed by dehydration in a Hitachi model HCP-2 critical point dryer. The dehydrated sample was coated with gold-palladium in a Hitachi model E-1010 ion sputter for 4 to 5 min and examined using a GeminiSEM 300 field emission scanning electron microscope (Zeiss, Göttingen, Germany).