## 2 Materials and Methods
### Modeling  
In order to model the TPMS structures, the input factors are cell types, lattice thickness, and cell size. The TPMS lattice structures are built using nTop with an overall dimension of 40 \(\times\) 40 \(\times\) 30 mm\({}^{3}\) with a base of 2 mm thickness in UVW orientation. The Peltier that is used to cool these models have 40 \(\times\) 40 mm\({}^{2}\) cooling surface. Hence the bottom surface of the models is identical in size to ensure uniform cooling effect throughout the structures. The model construction procedure was carried out using the guide from the nTop support knowledge base [43] and can be described in 7 simple steps that are shown in Figure 2.  
1. Creating the bounding box that defines the space for the lattice structure for the final part and the plate that resembles the base of the structure. The bounding box is 40 \(\times\) 40 \(\times\) 30 mm\({}^{3}\), and the plate is 40 \(\times\) 40 \(\times\) 2 mm\({}^{3}\). 2. With the operation of Boolean union, connect the bounding box and the plate as a single body. 3. Choosing the type of unit cell that is used to create the lattice model with the cell map type. A rectangular cell map is chosen to have a uniform design in all x-, y-, z-directions. 4. Additional information regarding building this lattice structure such as orientation (UVW is chosen here), cell size, and approx. thickness of the lattice or lattice thickness is defined here. Lattice thickness and cell size are the input factors for these design considerations. 5. Lattice structure within the cell map is generated in this step. 6. Boolean union is performed to attach the lattice structure to the base plate. Figure 2: Model construction steps. Since the generated lattice overhangs the bounding box because of its independent formation, Boolean intersection with the bounding box is performed resulting in the desired size of final parts. Cell types (C): In the nTop software, under TPMS structure options, there are a total of 6 types of lattice structures: Neovious, Schwartz, Lidinoid, Gyroid, Diamond, and SplitP (Figure 3a). The Neovious model has inner hollow structures (Figure 3b) that are mainly implemented to make the parts light in weight in different applications such as aerospace or automobiles. For the application of this study, only exposed surfaces are important. The calculated surface area by the software is misleading in this scenario and hence, Neovious is excluded from further consideration in this paper. Lattice thickness (T): Wall thickness of each cell in each cell type. In this study, three levels of T are considered: Thin, Moderate, and Thick. Values for 'Thin' are selected to be the lowest possible values that can support the structural integrity without distorting the cell design. Similarly, 'Thick' is selected to be the largest possible values that maintain the cell identity without decreasing too much surface area. The 'Moderate' values are in between Thick and Thin but not exactly a geometric mean of the highest and lowest values. A closer value to the geometric mean that does not produce broken corners is selected for each case. Because TPMS is basically stacks of multiple unit cells connected together, it is possible to generate a partial overhang from the main structure. This prohibits the next step, such as meshing and can lead to false values of surface area and volume. Depending on the C, the value for these three levels can vary. Such as for Gyroid, Thin (1.5 mm), Moderate (2 mm), and Thick (4 mm) whereas for Schwartz, Thin (1 mm), Moderate (1.5 mm), and Thick (2 mm). Cell size (X): The size of individual cells contained in the structure. The smaller the size, the greater the number of cells that can be packed in the same block. The three levels X's considered in the study are Small, Medium, and Large.