# Characterization of a Rectangular-Cut Kirigami Pattern for Soft Material Tuning
## 3 Results
### Experimental Results  
The experimental results demonstrate that there is a variation in the behavior of the different specimens in response to changes in the width of the cuts. Similarly, various types of variations can be assessed, such as changes in width, length, and distribution. However, the characterization of the specimens with rectangular cuts allows determining their behavior in response to cut variations. In Figure 7a, the specimen with minimal cuts is shown; these cuts were traced in the 3D printing process and subsequently made directly with a knife. In Figure 7b, the specimen with 1 mm thick cuts is displayed, while in Figure 7c, the specimen with 1.5 mm thick cuts is shown. A total of eighteen test specimens were manufactured for the experimental development, with six specimens for each type of cut and distribution presented. Finally, in Figure 7d, the tension test is shown being conducted on the Lloyd Instruments Texture Analyzer, where it can be observed that one end is secured while a vertical force is applied to the other end, causing displacements and stresses. Figure 8 displays the final condition before reaching the breaking point of the test specimen. In this state, it is observed that if the distribution of the cuts is uniform, all rectangular cuts deform uniformly along the test specimen, except for those at the extreme points. Therefore, understanding the deformation experienced by a rectangular cut enables the modeling of the behavior of an entire base material with rectangular-cut patterns uniformly distributed on it. Figure 6: FEM results show the evolution of kirigami cut deformation. (**a**) Test specimen deformation shown at transitional state. (**b**) Strain–time evolution on central nodes of the specimen test simulation. The variation in maximum elongation obtained with each cutting variation is displayed in Figure 9. For the test specimen in which cuts with the greatest width (1.5 mm) were performed, the highest average elongation of 218 percent was achieved. For the specimen  
Figure 8: Final state for experimental test on test specimen with rectangular 1 mm cuts. Figure 7: Different test specimens with a centimeter-scale background: (**a**) test specimen with almost zero width cuts; (**b**) test specimen with 1 mm width cuts; (**c**) test specimen with 1.5 mm cuts; (**d**) test specimen on texture analyzer. with 1 mm cuts, the average elongation was 188 percent, while for the specimen with the minimum cut, the average obtained elongation was 176 percent. In terms of the variation observed across the tests, it is noted that this variation in final elongation increases with the width of the cut applied to the specimen. Upon reviewing the experimental tests, it was observed that the specimens tended to slip from the grips of the testing device as the displacement increased. Additionally, for tests with a 1 mm wide cut, specimens reached the rupture point at different locations. These variations are believed to be primarily attributed to the manufacturing process. Furthermore, the stiffness associated with the response exhibited the following variation, as indicated by the results estimated by the testing device, and illustrated in Figure 10. For the test specimen with the widest cuts (1.5 mm), the stiffness was 1635 N/m. In the case of the specimen with 1 mm cuts, the average stiffness measured 3264.84 N/m, while for the specimen with the minimum cut, the average stiffness was 4020.29 N/m. In Figure 11, the stress-strain relationship is shown for a set of experimental tests. It can be observed that each group of specimens exhibits a behavior trend according to the type of rectangular kirigami cut they had. Specimens with minimal cuts show higher stress against the presented deformation, and similarly, the slope of these curves representing stiffness is also higher. Specimens with a 1 mm wide cut reduced the amount of stress for a similar unitary deformation, and the slope of the trend was also lower.