Harnessing imperfections to elicit functionality in soft mechanical metamaterials

Elastic instabilities, traditionally avoided in mechanical structures, have become a powerful tool to attain novel functionalities well-suited for a wide range of applications in soft robotics, smart structures, and logic devices. Existing studies are limited to exploiting elastic instabilities in periodic systems where the response can be inferred from the underlying defect-free representative volume element. In this work, imperfections in the form of soft inclusions are introduced in biholar metamaterials to control instabilities, thereby achieving tunable mechanical responses and programmable logic. Using a combination of numerical simulations and mechanical testing, we unveil the emerging mechanics and mechanisms that trigger instability and non-trivial non-linear responses. Programming location, density, and distribution of defects in soft biholar metamaterials enable to impart unique functionality that would be otherwise unachievable in their defect-free counterparts.