*2.1. Laser Set-Up*

Periodic radial straight grooves patterned with LIPSS were generated on 30 mm diameter discs made of X5CrNi1810 steel. The discs were previously lapped to have a 30 nm average roughness (Root Mean Square).

In the experiment, Yb:KGW a chirped-pulse application laser system (model PHAROS 20W from Light Conversions Ltd. was used. Optical pulses (central wavelength 1030 nm, pulse width 213 fs, repetition rate 600 kHz) were forwarded to a galvanometric scanning head (Cambridge Technology). Alignment of linearly polarized laser light was controlled by a half-wave plate. The surface treatment was done in air at room temperature by scanning a laser beam across the sample surface. The laser beam was focused by an F-theta lens with a focal length of 56 mm that produced an approximate diameter of the irradiation spot of 10.6 microns (1/e<sup>2</sup> of peak intensity) on the sample. The transmittance of the focusing system was measured independently prior to the experiments and was found to be 80% at the laser wavelength. With this data, a peak fluence of 0.51 J/cm2 was estimated on the surface.

Figure 1 shows the strategy of laser treatment. For the scanning approach, 5 mm long scanlines were formed in the radial direction by moving the laser spot with the galvanometric scanner at a scanning speed *vs* equal to 3 m/s, while rotational motorized stage with circumferential speed ω of 1.45–2.5 rad/s generated circular patterned tracks with 4 microns of interline spacing. The polarization plane was set-up to uniformly orient LIPSS in the circumferential directions.

**Figure 1.** (**a**) Schematic of the laser treatment as a laser beam is scanned over a sample. (**b**) Details of laser patterning strategy: the laser beam is moving forth and back, while the sample is rotating by angular stage.
