## 3 Results
### Single- and Multiple-Overscan Lines  
For PC, we systematically investigated the dimensions of the laser-written lines. The line width was measured with SEM. The main results are shown as Figure S2 in the Supplementary Materials. We observed a linear dependence of the square of the line width (or line radius) and the natural logarithm of the laser pulse energy, as is expected for a Gaussian laser beam profile. This has been discussed in more detail, for instance in [25].  
The most promising results for the manufacturing of HSF-LIPSS-covered lines on PC were obtained using up to 100 overscans with moderate laser powers and relatively low repetition rates. Figure 5a shows an overscan line which is almost completely covered with HSF-LIPSS. This line showed a uniform distribution of HSF-LIPSS at the sidewalls and the formation of a debris area around the line. In this debris area, LSF-LIPSS are sometimes faintly visible, as previously observed in the craters (see Figure 2c). However, they are so indistinct that obtaining images of them was found to be difficult, and no good image can be presented here. The line width for 9 mW was 50 \(\upmu\)m and the line width including the debris area (referred to as the outer line) 63 \(\upmu\)m. Figure 5b shows a higher-magnification image of an 8 mW overscan line. The depth and the width of this line are slightly smaller than for the 9 mW line. The sidewalls are still not entirely covered with HSF-LIPSS, which form preferentially on some plateaus, similarly to in the crater in Figure 3.  
Figure 5: SEM images of laser-written lines on PC: (**a**) multiple-overscan line with \(p=9\) mW, \(f=0.5\) kHz, \(v_{scan}=2000\)\(\upmu\)m/s, \(N_{line}=18.75\), \(\#\)\(\)\(\approx\)\(50\) and \(F_{0}=0.75\) J/cm\({}^{2}\); (**b**) detail of multiple-overscan line with \(p=8\) mW, \(f=0.5\) kHz, \(v_{scan}=2000\)\(\upmu\)m/s, \(N_{line}=18.75\), \(\#\)\(\approx\)\(50\) and \(F_{0}=0.67\) J/cm\({}^{2}\); (**c**) multiple-overscan lines (\(\Delta S=70\)\(\upmu\)m) with \(p=9\) mW,\(f=0.5\) kHz, \  
To structure an area at least 2 \(\times\) 1 mm\({}^{2}\) (necessary for the cell experiments), multiple 100-overscan lines must be stacked. The whole line array was written once before starting the next overscan. Figure 5c shows an image of multiple-overscan lines with \(\Delta\)S = 70 \(\upmu\)m line spacing. The unstructured flat PC surface remains unaffected between the lines, and some debris fragments are also clearly visible. The LIPSS on the sidewalls of the lines can be seen by zooming in.  
With 100 overscans, HSF-LIPSS-covered lines were found in a power range between 7 and 11 mW. Lines with fewer overscans at 9 mW power already showed some HSF-LIPSS with 20 overscans (slightly less than the 7 mW line with 100 overscans). For the other powers in this range, we only observed HSF-LIPSS after at least 50 overscans. An increase in laser power could also cause the HSF-LIPSS to disappear. Instead, an irregular sponge-like structure appeared, as previously observed for the craters at high laser powers (see, for instance, Figure 2a). An exemplary line pattern, where only irregular sponge-like structures can be seen on the laser-irradiated surface, is shown in Figure 5d.  
For pure CAB, the best, most promising line results were obtained with a laser power of 20 mW. This is shown exemplarily in Figure 6. In this image, the irregular sponge-like structure previously observed in the craters (see, for instance, Figure 4) can be seen on the sidewalls of the line. The line shows a width of 50 \(\upmu\)m, which should be well suited for the cell experiments. At considerably lower laser powers, the material just melts, which was confirmed with multiple-overscan lines as well as with craters.