Micro-scale Mechanical Metamaterial with a Controllable Transition in the Poisson's Ratio and Band Gap Formation

The ability to change significantly mechanical and wave propagation properties of a structure without rebuilding it has been one of the main challenges in the field of mechanical metamaterials. This stems from the enormous appeal that, especially in the case of micro-scale systems, such tunable behavior may offer from the perspective of applications ranging from biomedical to protective devices. In this work, a novel micro-scale mechanical metamaterial is proposed that can undergo a transition from one type of configuration to another, with one configuration having a very negative Poisson's ratio, corresponding to strong auxeticity, and the other having a highly positive Poisson's ratio. The formation of phononic band gaps, at the same time, can be controlled, which can be very useful in the design of vibration dampers and sensors. Finally, it is shown experimentally that reconfiguration of the system, leading to a change in its properties, can be induced and controlled remotely through application of a magnetic field, thanks to appropriately distributed magnetic inclusions.