We designed equivalent corrugated models using CAD software (SolidWorks) and derived the second area moment. The values obtained from the experiment and CAD software were compared using SCSs fabricated with = 10 (Figure 11a). We created the SCS models using the measured amplitude d and half-wavelength w, as shown in Figure 6d and the equation shown in Figure 11a. Figure 11b presents the results of the comparison. The simulation results were consistent with the experimental results, and the second area moment increased with an increase in amplitude. However, there were significant differences in the values. Furthermore, the amplitude dependence of the SCS stiffness exhibited a linear scaling relationship, which is different from the quadratic scaling expressed by Equation (12) and previous studies  \cite{hubbard2021stiff} . This is one of the characteristics of SCSs fabricated from flexible sheet materials and may be because the structure has not been deformed with maintaining the corrugated cross section. Figure 11c presents the mountain fold parts after the three-point bending test. The deformation of the mountain fold parts can be observed.  
Due to the flexibility of the developed SCS, we found that the SCS can be stacked and strengthened without occupying space. Stacking a large number of sheets allows for the realization of the same strength as that of a sheet of thickness that would not inherently undergo self-folding. We fabricated 2, 3, and 10 sheets of the SCS with = 10 and linewidth = 15 mm. Figure S3 presents the comparison between a one-sheet SCS and a 10-sheet SCS. Given that the SCS is thin and flexible, 10 sheets could be stacked without occupying a significant amount of space. We conducted a three-point bending test on the 2, 3, and 10 sheets of the stacked SCSs. Figure 11d and e present the results. As shown in Figure 11d (load-deflection curves), the slope of the initial stage increased, and the stiffness increased as the number of sheets stacks increased. Furthermore, the second area moment increased linearly with the number of sheets (181% for 1–2 sheets, 452% for 3 sheets, and 1461% for 10 sheets), as shown in Figure 11e. Hence, the stiffness of an SCS is dependent on the design parameters of the corrugated structures and the number of stacked sheets. Moreover, the load-deflection curve for 10-sheet stacking did not increase or decrease the load, as shown in Figure 11d. Based on this result, we inferred that only the mountain-folded part of the sheet buckled when 10 sheets were stacked, and the residual part of the SCS does not buckle. This can be attributed to the improvement of material strength by stacking 10 sheets.