Hypothesis: Considering the increasing advancements in the field of 3D printers and their ability to produce complex structures, it is possible to produce auxetic structures with unique performance using this method. Additionally, integrating re-entrant unit cells within conventional re-entrant unit cells and achieving a novel merged re-entrant structure can lead to improved properties Methods: A novel re-entrant auxetic structure is presented in this study, which is designed by merging four small re-entrant unit cells into a larger re-entrant unit cell and produced by 3D printing. The larger re-entrant unit cell is a conventional re-entrant unit cell, in which the novel merged structure is created by embedding the smaller unit cells within its ligaments. For comparison, the conventional re-entrant structure was also designed, and 3D printed. The Poisson's ratios of both structures were measured and compared at different longitudinal strains (from 5% to 25%) Findings: The results show that both structures have a negative Poisson's ratio and exhibit auxetic behavior. The novel merged re-entrant auxetic structure performed better at lower longitudinal strains (5%) compared to the conventional re-entrant auxetic structure, while at higher longitudinal strains (greater than 5%) the conventional re-entrant auxetic structure performed better. Additionally, the novel merged re-entrant auxetic structure demonstrated better capability in maintaining its hape at higher strains compared to the conventional structure. The highest negative Poisson's ratio values obtained in this study correspond to a longitudinal strain of 5%. In this case, the Poisson's ratio of the conventional re-entrant auxetic sample is -1.56, whereas the Poisson's ratio of the novel merged re-entrant auxetic sample is -1.58. These results indicate the high potential of the novel merged re-entrant auxetic structure in various engineering applications.
