## 5 Conclusions  
Laser-induced micro- and nanostructures on PC and CAB surfaces were used for achieving the directed growth of Schwann cells, which are of special interest as they support the regeneration of the nerve pathways by guiding the neuronal axons in the direction of their alignment. Schwann cells can grow in a certain direction, predetermined by micro-groove orientation. In contrast, cells cultivated on unstructured surfaces show an omnidirectional growth behavior. For PC, the LIPSS at the walls of the micro-grooves led to an additional orientation effect by guiding the protrusions of the Schwann cells, even though the orientation was not perfect. The sponge-like nanostructure on the walls of the micro-grooves of CAB seems to have this effect only to a minor degree. The next step in the direction of a potential application of these structures would be to obtain the investigated  
Figure 8: SEM images of Schwann cells (after 3 days in culture) on multiple-overscan lines (\(\Delta S=60\) μm) on PC with \(p=9\) mW, \(f=0.5\) kHz, \(v_{scan}=2000\) μm/s, \(N_{line}=18.75\), \(\#os=100\) and \(F_{0}=0.75\) J/cm\({}^{2}\), viewed under a tilt angle of \(45^{\circ}\): (**a**) a line written in the x-direction; (**b**) lines written the in y-direction. The red arrow in images (**a,b**) indicates the direction of the HSF-LIPSS.  
materials in fiber form (as fillers for nerve conduits) and to test whether laser treatment improves nerve regeneration capability.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app15126754/s1](https://www.mdpi.com/article/10.3390/app15126754/s1)]([https://www.mdpi.com/article/10.3390/app15126754/s1](https://www.mdpi.com/article/10.3390/app15126754/s1)), Figure S1: FTIR-ATR spectra of investigated polymer materials; Figure S2: Width of 1040 nm fs laser-written lines on PC as function of laser pulse energy.  
Conceptualization, J.H.; methodology, L.W., S.L., W.B. and J.H.; investigation, L.W., W.B. and A.W.; resources, J.H. and W.B.; writing--original draft preparation, L.W., S.L. and J.H.; writing--review and editing, L.W., W.B., A.W., S.L. and J.H.; visualization, L.W. and J.H.; supervision, W.B. and J.H.; project administration, J.H.; funding acquisition, J.H. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Austrian Federal State of Upper Austria, in the frame of the scheme OO. ANBAHUNOSFORDERUNG EXPANDING HORIZON.  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} ATR & Attenuated total reflection \\ CAB & Cellulose acetate butyrate \\ CAGR & Compound annual growth rate \\ CDs & Compact disks \\ ECM & Extracellular matrix \\ FTIR & Fourier transform infrared \\ fs & Femtosecond \\ HMDS & Hexamethyldisilazane \\ HSF & High-spatial-frequency \\ HSFL & High-spatial-frequency LIPSS \\ KrF* & Krypton fluoride excimer \\ LIPSS & Laser-induced periodic surface structure \\ LSF & Low-special-frequency \\ LSFL & Low-special-frequency LIPSS \\ NIR & Near-infrared \\ ns & Nanosecond \\ PBS & Phosphate-buffered saline \\ PC & Polycarbonate \\ PET & Polyethylene terephthalate \\ ps & Picosecond \\ SCs & Schwann cells \\ SEM & Scanning electron microscopy \\ USD & United States Dollar \\ UV & Ultraviolet \\ \end{tabular}