In this study, we developed a corrugated structure made of a smart material. A design theory of the structure was proposed, and its mechanical properties were evaluated. We denote the developed structure as a self-folded corrugated structure (SCS). Based on the reaction between a smart material and inkjet printer ink, the structure was formed autonomously without applying external energy. First, we proposed a structural model to predict the final shape of the SCS from the printed pattern. By calculating the fold angle from the proposed model, a linear relationship between the printed linewidth and the fold angle was obtained, similar to the conventional method \cite{shigemune2016origami}, which validated the proposed model. The design parameters of the SCS were the printed line width and number of printed lines. Self-folded corrugated structures with various amplitudes and wavelengths were formed by varying the parameters. Second, the mechanical properties of the SCS were evaluated by conducting a three-point bending test. The results revealed that the SCS exhibited anisotropic stiffness, which is one of the typical properties of corrugated structures. In addition, with an increase in the amplitude of the SCS, the second area moment increased, as expressed by the theoretical equation of the second area moment of corrugated structures. As a characteristic of the SCS, we confirmed that, for a large wavelength range, the structure collapses due to the flexibility of the paper. Furthermore, we found that the SCS is sufficiently flexible for easy stacking after self-folding. The structural strength of the SCS can be improved linearly by stacking structures. Thus, the fabrication system of the SCS provided stiffness to a sheet of paper, which is innately flexible to be applied as a core material. Given that the only fabrication method is the application of solution by inkjet printing, the corrugated structure with the desired stiffness can be created rapidly according to the desired applications. Moreover, the SCS can be stacked without occupying a significant amount of space, thus minimizing energy consumption during transportation and reducing the transportation costs. Therefore, the SCS will be developed as a novel smart core for future applications owing to its high stiffness, digital manufacturing ability, and high transportability.
Concept of the Self-Folded Corrugated Structure