## 3 Results
### Macroscopical Features of the Island Scan Stripes Specimen  
The surface topography of the island scan stripes specimen clearly shows a pattern of height differences reflecting the 20 \(\times\) 20 island pattern (Figure 3a). All islands are higher in the first scanned corner, consistent with the same scan strategy for all islands (parallel-interlaced-reversed (PIR)). In general, the \"green valleys\" in Figure 3a were scanned later than the \"red ridges\". The degree and shape of the increase vary, which relates to the order in which the islands were scanned. This order was unchanged during building in the z-direction. The macrographs of the cross sections in Figure 3e,f show that most of the islands have a surface inclination towards the left-hand side (e.g., \(-\)x and \(-\)y), which is preserved in the build direction. Figure 3: Island scan stripes specimen: **(a)** IFM image showing the surface texture; 3D rendering of the internal porosities identified in Avizo from CT scans of **(b)** full specimen and **(c)** reduced area using 4\(\times\) objective; **(d)** sketch of specimen with placement of cuts for the **(e,f)** optical macrographs and **(g)** degree of porosity as function of x- and y-layer as calculated in Matlab from CT scan data. High resolution image of **(e,f)** is provided in Figure S4. This indicates that the height differences are introduced in an early stage of the build and are retained (and possibly aggravated) on continued building. This phenomenon is directly related to the scanning of individual islands, while they are completely surrounded by powder and have no immediate neighboring island that was scanned earlier. As convincingly demonstrated by [PERSON] et al. [PERSON] et al. (2018), the first melt track that is formed in a deep powder bed (first layer) sinks towards the bottom of the powder bed as the track proceeds, and undergoes bending during cooling, leaving the first scanned corner at a higher level than the part that is later melted and the solidified part. This is hereafter termed \"bending deflection\". In this respect, the first line of each island behaves similar to the line scan specimen in Figure 2, albeit on a smaller scale. It is noted that parallel line scanning applies for the islands in Figure 3, while antiparallel scanning applies for the lines in Figure 2. As a consequence, bending deflections in both x- and y-directions occur for the islands (the specimen bottoms in Figures 2f and 3e). In addition, the surface topography depends on the presence of completed neighboring islands in the same layer. If an island is scanned after an island to its right (+x) was completed earlier and, consequently, has already deflected slightly upwards on the left-hand side (\(-\)x), the island being scanned will be fused to the island on its right (+x) at a slightly lower position. If, on the other hand, an island is already present to the left (\(-\)x), the difference in surface height at fusion is not as prominent, because deflection is most prominent at the left-hand side (\(-\)x, first scanned). According to the same reasoning, the number of neighboring islands (up to 4) affects the surface topography. The same phenomenon means that scanning above (i.e., in the y-direction) an already scanned island leads to a smaller height difference than scanning below an already solidified island (\(-\)y), leading to the direction pattern of the deflections seen in the island scan stripes specimen (Figure 3a). Some islands have more material near the edges of the islands, showing that the edge effect is significant for this method. The first scanned island includes powder from the adjacent (non-scanned) islands, implying that the first scanned island has higher edges, and leaves less powder for melting at the borders for later scanned adjacent islands. As a consequence, pronounced fusion defects arise in-between the islands.