## 3 Results  
The chemical structure of the PGSU synthesised was previously confirmed using Fourier-transform infrared spectroscopy [6]. Figure 1 shows the SEM images from the PGSU-perpendicular scaffolds fabricated using mould-perpendicular. As expected, this scaffold had a unidirectional pore structure, moving from the bottom to top (perpendicular) forming porous channels (cross-section view), which interconnect with the top part of the scaffold. The pore size of the PGSU-perpendicular is significantly different between its cross-section and top section, with pore sizes of 34.1 \(\pm\) 9.6 \(\upmu\)m and 40.3 \(\pm\) 4.6 \(\upmu\)m, respectively. The SEM images of the PGSU-parallel scaffold are shown in Figure 2. As described before, the scaffold was rotated by 90\({}^{\circ}\) before investigation. The resulting scaffold had a rectangular parallelepiped shape and the pore direction was unidirectional from the left to right. A uniform structure is observed with porous channels formed along the horizontal axis. When it was examined for its cross-section, open pores were found throughout the scaffold. The uniformity of the pore structure is also demonstrated from the pore size measurements. The PGSU-parallel scaffold showed no significant difference in pore size between the top, cross- and bottom sections, and its pore sizes ranged from 67.8 \(\pm\) 20.0 \(\upmu\)m to 78.8 \(\pm\) 24.2 \(\upmu\)m.  
Figure 3 illustrates the microstructure of the PGSU-bilayer scaffolds. In this case, the top layer was made from PGSU-15% and bottom layer from PGSU-10%, thus there is a difference in pore structure when it is observed from the cross-section. The bilayer scaffold shows both isotropic and anisotropic structures. It is clear where the layers meet and a good attachment between them is also evident. The pore structure on the surface is similar to when the scaffold was being imaged from its top and bottom section. The pore sizes of the PGSU-bilayer were measured, and multiple pore sizes were found depending on the layer and the section. Considering each layer individually, there was a significant difference between the pore size of the top layer (PGSU-15%) when compared with that of its cross-section. A similar observation was found from the bottom layer (PGSU-10%). There was also a significant difference between the pore size of the different layers, especially in the cross-section. The pore size for the PGSU-15% layer was 26.2 \(\pm\) 4.9 \(\upmu\)m and the pore size for the PGSU-10% layer was 74.0 \(\pm\) 8.4 \(\upmu\)m, which is an approximately 2-fold difference. Figure 1: SEM images of PGSU-perpendicular scaffolds. (**A1**,**A2**) Top section and (**B1**,**B2**) cross-section showing anisotropic pores orienting from the bottom to the top of the scaffold. Figure 3: SEM images of PGSU-bilayer scaffolds. (**A1**,**A2**) Top section, (**B1**,**B2**) bottom section and (**C1**–**C4**) cross-section (**C2** = PGSU-15%, and **C3**,**C4** = PGSU-10%) showing isotropic and anisotropic porous microstructures. The red arrows show the intersection between the layers of the scaffold. Figure 2: SEM images of PGSU-parallel scaffolds. (**A1**,**A2**) Top section, (**B1**,**B2**) bottom section and (**C1**,**C2**) cross-section showing the anisotropic pores orienting from the left to the right of the scaffolds. The last scaffold that was fabricated was PGSU-trilayer and the results are shown in Figure 4. In this case, the top layer acts as a BM, which is a thin non-porous film (-92 \(\upmu\)m thick) and, at the same time, the bottom section has an open pore structure. The bottom two layers of the PGSU-trilayer scaffold exhibited both isotropic and anisotropic microstructures, similar to the case in the PGSU-bilayer. The connection between all three layers is also shown with red arrows, which confirms that one solid scaffold can be fabricated from three different layers, that can be distinguished by their difference in pore structure and porosities.