Reconfigurable enhancement of actuation forces by engineered losses in non-Hermitian metamaterials

While boosting signals with amplification mechanisms is a well-established approach, attenuation mechanisms are typically considered an anathema because they degrade the efficiency of the structures employed to perform useful operations on these signals. An emerging alternate viewpoint promotes losses as a novel design element by utilizing the notion of exceptional point degeneracies (EPDs)- points in parameter space where the eigenvalues of the underlying system and the associated eigenvectors simultaneously coalesce. Here, we demonstrate a direct consequence of such eigenbasis collapse in elastodynamics-an unusual enhancement of actuation force by a judiciously designed non-Hermitian metamaterial supporting an EPD that is coupled to an actuation source. Intriguingly, the EPD enables this enhancement while maintaining a constant signal quality. Our work constitutes a proof-of-principle design which can promote a new class of reconfigurable nano-indenters and robotic-actuators. Importantly, it reveals the ramifications of non-Hermiticity in boosting the Purcell emissivity enhancement factor beyond its expected value, which can guide the design of metamaterials with enhanced emission that does not deteriorate signal quality for mechanical, acoustic, optical, and photonic applications. (c) 2023 Elsevier Ltd. All rights reserved.

Automated summary

Boosting signals with amplification mechanisms is common, but attenuating mechanisms are less desired due to their negative impacts on efficiency. However, a new viewpoint suggests that attenuation can be used as a design element to enhance actuation force while maintaining signal quality. This study demonstrates the concept by designing a non-Hermitian metamaterial and provides a proof-of-principle for the design of reconfigurable nano-indenters and robotic actuators.