Antibacterial effect of periodic structure formed on SUS430 by using nanosecond pulsed laser

We investigated the laser-induced periodic surface structures (LIPSSs) formed on an SUS430 surface by irradiation with a nanosecond pulsed laser (Nd:YAG, wavelength of 532 nm, pulse width of 10 ns, number of pulses of 50, repetition rate of 10 Hz, and laser fluence of 1.2 J/cm2) and the antibacterial effect of the surface. LIPSSs with an interspacing of about 500 nm, which was close to the laser wavelength, were produced on the surface when the pulsed laser was near the ablation threshold. The film attachment method (JIS Z 2801) was used to measure the bacterial growth suppression on SUS430 surfaces with and without LIPSSs. On the surface without an LIPSS, the number of colonies was 1244, and on that with an LIPSS, the number was 198, indicating that the LIPSS formed by nanosecond pulsed laser irradiation inhibited the growth of bacteria. The chrome oxide layer on the SUS430 surface with the LIPSS may emit chrome ions from the edge of the LIPSS, enhancing the antibacterial effect.