YAG laser (wavelength of 532 nm and a pulse width of 10 ns) was irradiated to SUS430 surface to produce a periodic structure with an interspace of approximately laser wavelength.
The material is used mirror-polished SUS430 (25 mm x 25 mm, thickness 1 mm).
For the periodic structure formation experiment, the melting threshold fluence (F_Melt) of SUS430 was evaluated from the laser fluence dependence of the crater diameter, and it was found to be F_Melt = 1.18 J/cm².
A periodic structure was produced at a laser fluence F=0.8 J/cm² below the melting threshold and near the ablation threshold (F_th=0.96 J/cm²).
Escherichia coli DH5α with a size of about 500 nm to 1000 nm was used for film adhesion method as an antibacterial method. The periodic structure given to the material surface was about 500 nm, which was smaller than that of Escherichia coli DH5α.
In the film adhesion method, first, the cultured bacterial solution was dropped on the surface, covered with a film, and cultured for 24 hours.
After that, the bacterial solution was diluted and cultured again in a solid medium for 24 hours, and the antibacterial function was examined from the number of colonies formed.
As a result, it was found that the number of colonies of SUS430 with microstructure was 198 compared to the number of colonies of 1244 of the bacterial solution, which is about an order of magnitude decrease.