## 4 Manufacturing Experiment  
### Manufacturing Sheet Resistivity Resistor Types  
Conductivity (or resistance) is an important parameter for antennas. To improve the performance of the antenna, we need to increase the conductivity (reduce the resistance) as much as possible. Increased resistivity will cause increased attenuation of the transmitted signal, thus resulting in reduced antenna performance. The resistor manufactured below is a sheet resistivity resistor type. The characteristic feature of the sheet resistivity sample is that the resistances of the squares of any size are the same from side to side, regardless of whether the side length is 1 m or 0.1 m. Sheet resistivity is only related to the thickness of the conductive film. Therefore, the sheet resistivity is typically used to test the difference between the two printing methods. Figure 11 shows the size specifications and manufactured sheet resistivity resistor. It is difficult to assess the differences between the two types of sheet resistivity based on macroscopic observations. Correspondingly, we measured them with profilometry, as shown in Figure 12 below. As shown, when the sheet resistivity product is manufactured with conventional methodologies, its surface is uneven and the surface dimensional tolerance is large. Because the conductivity of the sheet resistivity product is determined by its thinnest area, the resistance value of the sheet resistivity product manufactured with conventional methods is significantly greater than that produced with the scheme proposed in this study. The measured results of the four-probe resistivity tester also confirmed this. Figure 11: (**a**) Drawings of sheet resistivity sample. (**b**) Sheet resistivity printed directly on conformal surfaces with conventional methodology, and (**c**) with the scheme proposed in this article. Figure 12: (**a**) Measured outcomes generated with direct printing with the conventional method, wherein the test area is the edge of the sheet resistivity sample. The lowest area on the left is the substrate, and the elevated area on the right denotes the solid nanosilver particle residue that remains after the ink is dried. The cumulative thickness of the ten-layer nanosilver ink is approximately 2 \(\upmu\)m. (**b**) Generated results with the use of this scheme have better surface flatness as those in Figure 12a. To verify the differences between the two sheet resistivity samples, we conducted microscopic observations. Figure 13a below is a micrograph printed with the conventional method, and Figure 13b below is an enlarged side view of Figure 13a, while Figure 13c is a micrograph printed with the method proposed in this study. In the figure, the black part is ink, and the white part is the substrate. It can be clearly observed that there are numerous pores in each line of ink dots. The printing outcome is not conductive. By controlling the size of the droplet to compensate for this drawback, we obtained Figure 13c wherein the ink deposition was very dense. Figure 13b is a better illustration of this problem. Figure 13a is acquired from the side. It can be clearly observed that the droplets are not fused. The results show that the sheet resistivity sample manufactured by the conventional method generates a rough surface, and the electrical conductivity is not as good as the sheet resistivity sample manufactured by the scheme proposed in this study. Finally, the scheme shown in Figure 8a was used and test layer samples were printed. Thus, to check the conductivity, we printed 10 layers of nanosilver solution to test the comparison. The appearances of the two sheet resistivities were similar, but after the four-probe resistivity tester test, the value of the conventionally printed sheet resistivity product was 3.51 \(\Omega\), and that printed using the model in this article was 0.05 \(\Omega\). The validity of the conformal array head print model proposed in this study was verified.