Vibration in one direction only  October 10, 2019 Researchers in the Netherlands created a robotic mechanical metamaterial wherein they used local control loops to break reciprocity at the level of the interactions between the unit cells. They showed theoretically and experimentally that first-of-their-kind spatially asymmetric standing waves at all frequencies and unidirectionally amplified propagating waves emerge. These findings realize the mechanical analogue of the non-Hermitian skin effect. They significantly advance the field of active metamaterials for Hermitian physics and open avenues to channel mechanical energy in unprecedented ways. Non-reciprocal transmission of motion is potentially highly beneficial to a wide range of applications, ranging from […]