Phys. Rev. Lett. 113, 175503 (2014)

Credit: © American Physical Society

The deformation behaviour of mechanical metamaterials results from their unique architectures responding to applied loads. Various non-trivial mechanical properties have been demonstrated in these systems, including negative Poisson's ratio and the cloaking of a rigid core inside an external structure. One type of mechanical metamaterial utilizes a uniform network of equally sized cavities that buckle under load, leading to unique mechanical functions. However, each structure can display only one mechanical function, due to the cavities being identically sized. Martin van Hecke and colleagues now introduce a periodic distribution of two hole sizes in quasi-two-dimensional elastomeric sheets. By confining deformation along one axis of the sheet, and deforming it at 90 degrees to the confined axis, they find there is a switching in the polarization of the buckled holes. Then, through systematic variation in the extent of confinement and load, switching can occur in either a monotonic or non-monotonic process, or via hysteresis, in the force–displacement curves. Such structures offer potential for tuning complex mechanical functions in architectured systems.