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Mechanical metamaterials can be designed to give rise to exotic properties such as negative stiffness, negative Poisson’s ratio (auxeticity), and tailorable buckling by selectively designing the geometry of the host material. However, these behaviors are typically fixed and cannot be changed once the metamaterial has been fabricated. Motivated by the goal of post-manufactured application-specific adaptability, we present a soft mechanical metamaterial with pressurized circular voids for in-situ tunable mechanical properties. Prototypes are created by curing a two-component silicone rubber in a 3D printed mold. The circular voids are sealed at one end and independently connected to a pressure source on the opposite side, allowing any subset of the voids to be pressurized. Uniaxial compression tests are then conducted on a universal testing machine. Through selective pressurization of the voids, we demonstrate tunability of the material’s stiffness profiles and the critical loads that lead to the onset of auxeticity and/or buckling. Numerical investigations allow deeper insight, revealing that selective pressurization affects the qualitative shape of the first buckling mode and illustrating how pressurization can break the auxetic behavior of the nominal, unpressurized specimen. Overall, the outcomes demonstrate that soft elastomers with selectively pressurized voids can express quantitatively and qualitatively tunable responses, offering potential for new types of mechanical metamaterials with predictable, in-situ tunability.
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