## 2 Materials and Methods
### Extrusion-Based 3 DFP  
To proceed with the extrusion-based 3 DFP process, two square pillars were initially designed using FreeCAD version 0.19 (Figure 1). The first square pillar corresponded to a single-material square pillar using only the NCD, with a diameter of 30 mm and a height of 10.5 mm (Figure 1a). In contrast, the second square pillar corresponded to a multi-material pillar using NCD and CP, with a diameter of 30 mm and a height of 10.5 mm (Figure 1b). The height of the second square pillar was divided into three layers: 3.0, 4.5, and 3.0 mm each. The outer 3 mm layers were formed using NCD, and the central 4.5 mm layer was formed using CP. After that, the.stl files for each of the designed square pillars were exported and uploaded to the slicer software Slic3r (version 1.2.9), where the printing parameters were established (Table 1), and the corresponding G-codes were generated. The printing parameters used (Table 1) were derived from previous research done on printability of NCD [12]. The printing speed was set to 20 mm/s. This corresponds to the speed at which the moving stage shifts. The values of the inner diameter and initial nozzle height were matched to 1.5 mm. The rate at which the 3D food printer extrudes the food paste is determined by the extrusion multiplier, which increases or decreases the screw rotation of the 3D food printer at higher or lower values, respectively. Since the printing behaviors of the NCD and CP are different, the extrusion multiplier was chosen to be 5.0 and 12.0 for the NCD and CP, respectively. This was based on previous research [12] and trials to partially march the extrusion rate and printing speed. The infill pattern was set as \"Concentric\", and the number of outer shells was set to two. The infill percentage was set to 100%. Subsequently, the obtained G-codes were uploaded to a graphical user interface host for 3D printing, Pronterface (version 1.6.0). Finally, a screw-based 3D food printer (FP-2500, Seiki Co., Ltd., Yonezawa, Japan) equipped with two extruders (nozzles) moved by a motor each (Figure 2a) was used to print the square pillars. Each food paste container was filled with NCD or CP until the top. After that, each square pillar, single- or multi-material, was printed ten times using the printing parameters listed in Table 1. This experiment was carried out at a constant room temperature of 25 \({}^{\circ}\)C, and no heating was applied in the 3D food printer.  
Figure 1: The designed three-dimensional (3D) models: (**a**) Single-material square pillar made of nixtamalized corn dough (NCD) only; (**b**) Multi-material square pillar made of NCD and chickpea paste (CP).  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Condition** \\ \hline Print speed (stage movement speed) (mm/s) & 20 \\ Nozzle inner diameter (mm) & 1.5 \\ Initial nozzle height (mm) & 1.5 \\ Extrusion multiplier for the nixtamalized corn dough (-) & 5.0 \\ Extrusion multiplier for the chickpea paste (-) & 12.0 \\ Infill pattern (-) & Concentric \\ Infill percent (\%) & 100 \\ Number of outer shells (-) & 2 \\ Temperature (\({}^{\circ}\)C) & 25 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Printing parameters.  
Figure 2: (**a**) Photograph of the 3D printer used in this study; (**b**) Points of size measurements of the 3D-printed square pillars: (**b1**) Length; (**b2**) Height.