Novel passive amplitude-independent nonreciprocal metamaterial based on locking mechanism

Nonreciprocal metamaterials constitute a significant area of research in engineering and physics. These metamaterials offer numerous advantages across various fields by enabling a unidirectional response to dynamic and static loads, a critical feature for wave manipulation applications such as isolation. However, most existing passive nonreciprocal metamaterial designs exhibit amplitude-dependent behavior, achieving peak performance primarily at large amplitudes, which restricts their practical use. To overcome this limitation, the current study introduces a passive, 3D-printed nonreciprocal metamaterial featuring amplitude-independent behavior achieved through an integrated locking mechanism. This design attains a nonreciprocity level exceeding 0.5, a threshold commonly required for practical applications. The proposed metamaterial consists of irregular pentagon-shaped unit cells fabricated using TPU 95 A via 3D printing. Experimental analyses were conducted using tensile testing, complemented by preliminary finite element analysis, to validate the locking behavior. The results demonstrate that the designed metamaterial achieves a high nonreciprocity level of 0.61, exhibiting minimal or no variations with amplitude. Additionally, an alternative configuration is proposed, offering dual-mode nonreciprocity-behaving reciprocally at low amplitudes and nonreciprocally at high amplitudes-by tuning the amplitude at which locking occurs. These findings provide valuable insights into the design of amplitude-independent nonreciprocal metamaterials, marking significant progress toward their practical implementation.