Static non-reciprocity in mechanical metamaterials

TL;DR

This paper demonstrates that static mechanical metamaterials can break reciprocity, enabling asymmetric responses and one-way displacement amplification through nonlinearities and geometrical asymmetries, with potential applications in energy and robotics.

Contribution

It introduces a novel approach to achieve non-reciprocity in static systems using nonlinearities and geometrical asymmetries, expanding the scope beyond dynamic wave-based systems.

Findings

Static non-reciprocity achieved in mechanical metamaterials.

Large nonlinearities enable asymmetric displacement responses.

Potential applications in energy harvesting and soft robotics.

Abstract

Reciprocity is a fundamental principle governing various physical systems, which ensures that the transfer function between any two points in space is identical, regardless of geometrical or material asymmetries. Breaking this transmission symmetry offers enhanced control over signal transport, isolation and source protection. So far, devices that break reciprocity have been mostly considered in dynamic systems, for electromagnetic, acoustic and mechanical wave propagation associated with spatio-temporal variations. Here we show that it is possible to strongly break reciprocity in static systems, realizing mechanical metamaterials that, by combining large nonlinearities with suitable geometrical asymmetries, and possibly topological features, exhibit vastly different output displacements under excitation from different sides, as well as one-way displacement amplification. In addition to extending non-reciprocity and isolation to statics, our work sheds new light on the understanding of energy propagation in non-linear materials with asymmetric crystalline structures and topological properties, opening avenues for energy absorption, conversion and harvesting, soft robotics, prosthetics and optomechanics.