Size matters: how periodicity and depth of LIPSS influences E. coli adhesion on ferritic stainless steel.

[Display omitted] • LIPSS with a periodicity of 270 nm can reduce adhesion of E. coli in more than 35 %. • LIPSS periodicity is a key factor in bacteria adhesion process. • LIPSS with the greatest depth (highest SDAEs) favour E. coli adhesion in every case. • LIPSS with a periodicity higher than bacterial size favour biofilm formation. • Same LIPSS can lead to differences in bacterial adhesion depending on wettability. Bacterial adhesion is a serious problem in the healthcare and food industries, causing health problems and economic losses. This study evaluates the generation of Laser-Induced Periodic Surface Structures (LIPSS) with different periodicities to reduce bacterial adhesion on ferritic stainless steels. LIPSS nanostructuring evolves from hydrophilic to hydrophobic with air exposure. Fresh samples with 870 nm LIPSS show nearly 50 % reduced E. coli adhesion, but this effect diminishes in stabilized samples. This effect on bacterial adhesion can be attributed to LIPSS periodicity being like bacterial size, which would allow bacteria to accommodate and provide a suitable environment for their adhesion. Our results show that, in stable samples when the LIPSS periodicity is around 400 nm, reductions by almost 30 % are achieved and this reduction reaches 35 % when periodicity is close to 270 nm. These results indicate that smaller spatial periods prevent bacteria from fitting into valleys, so they remain on the peaks, hindering bacterial adhesion. Additionally, deeper LIPSS produced by a higher Surface Density of Applied Energy (SDAE), enhance bacteria-material interaction and, thus, increases adhesion. [ABSTRACT FROM AUTHOR]