An artist’s rendering of mechanical metamaterials. (Credit: Cockrell School of Engineering)

Engineers and scientists at the University of Texas at Austin and the AMOLF institute in the Netherlands have invented mechanical metamaterials that transfer motion in one direction while blocking it in the other. The material can be thought of as a mechanical one-way shield that blocks energy from coming in but easily transmits it going out the other side. The researchers developed the mechanical materials using metamaterials, which are synthetic materials with properties that cannot be found in nature.

Breaking the symmetry of motion may enable greater control of mechanical systems and improved efficiency. The researchers’ breakthrough lies in the ability to overcome reciprocity, a fundamental principle governing many physical systems. Reciprocity ensures the same response when an arbitrary structure is pushed from opposite directions. These nonreciprocal metamaterials can potentially be used to realize new types of mechanical devices, such as actuators (components of a machine that are responsible for moving or controlling a mechanism) and other devices that could improve energy absorption, conversion and harvesting, soft robotics, and prosthetics.