## 3 Results and Discussion
### Formation and Characterization of the Micro-Structured Surfaces  
We first designed polydimethylsiloxane (PDMS) substrates of known morphologies using replica demolding from a laser textured polycarbonate (PC) substrate. In our approach, the short pulse of 20 ns allowed a non-thermal ablative removal of the mold material and controlled formation of depth profiles with spatial resolution in the order of 0.1 and 1 \(\upmu\)m. Scanning electron microscopy (SEM) analysis (Figure 1a-c) and atomic force microscopy (AFM; Figure 1d-f) images allowed the evaluation of such structures and showed surfaces with a base unit of 250 nm/4 \(\upmu\)m square side size with varying spacing between their features. Moreover, analysis showed that such user-designed surfaces displayed multiscale level architectures of well-maintained dispositions (Supplementary Materials Figure S1). The distribution and density of the square units as well as root mean square (RMS) analysis revealed changes in surface roughness values from 11.5 mm for control (flat PDMS) [38; 39] to 110.7 nm for the PDMS-LDSU sample (Figure 2a), 226.9 nm for the PDMS-MDSU (Figure 2b), and 358.4 nm for the PDMS-HDSU sample (Figure 2c), respectively. Figure 1: Scanning Electron Microscopy images of surface structures polydimethylsiloxane (PDMS) (**a**) Low-density square unit (LDSU), (**b**) Medium-density square unit (MDSU), and (**c**) High-density square unit (HDSU), with scale bar of 50 \(\upmu\)m. Atomic Force Microscopy images of the PDMS structures of (**d**) LDSU, (**e**) MDSU, and (**f**) HDSU, respectively, with corresponding topographies in 3D and 2D representations combined with a synthetic illumination effect used to enhance the contour of each obtained slope. Figure 2: Profilometry analysis of the PDMS samples; top view results on the left-side and 3D maps on the right-side together with root mean square (RMS) values for: (**a**) LDSU; (**b**) MDSU and (**c**) HDSU, respectively. Sample microstructure height values were evaluated by the Abbott-Firestone algorithm and are revealed in Figure 3. As shown, for the PDMS-LDSU (Figure 3a), the predominant depths values were in the 0.164-0.330 \(\upmu\)m range, while the ranges for PDMS-MDSU (Figure 3b) and PDMS-HDSU (Figure 3c) samples were between 0.320-0.640 and 0.200-0.670 \(\upmu\)m, respectively. Further, analysis showed that PDMS-MDSU and PDMS-HDSU samples had approximately the same height of their surface structures, while PDMS-LDSU showed the smallest height structures. The above results were also confirmed by AFM analysis (Supplementary Materials Figure S3). Specifically, analysis showed a value of 0.67 \(\upmu\)m between two primary units (high and an intermediate), as well as between the intermediate and a shallow one for the HDSU probe. The force-displacement data were further used to estimate the elasticity of the samples; it is known that manipulating substrate's elasticity or topography could be used to promote organized epitheliogenesis and controlled cell proliferation and differentiation [40,41]. Previous studies have shown that a number of cellular processes including adhesion, migration and proliferation [40] could be influenced by the substrate itself to determine cell fate. Contact mode and force versus distance and tip-substrate adhesion AFM measurements were evaluated at shallow, medium and higher point of each substrate (Supplementary Materials Figure S2), revealing that most significant adhesion forces were held by the HDSU samples whose density of primary units were much higher than compared to the other two surfaces. Lastly, contact angle measurements and surface free energy analysis were performed to evaluate the degree of contact surface wetting and the hydrophobicity of PDMS, respectively. As shown in Figure 4a, even though the PDMS contact angles changed with the various types of structure densities, all surfaces remained hydrophobic. Analysis also showed that increasing the density of the primary  
Figure 3: Distribution of PDMS depths: (**a**) LDSU; (**b**) MDSU and (**c**) HDSU.