Design of Acoustic MEMS Metamaterials with Programmable Nonreciprocity

An increasing number of non-reciprocal acoustic devices have been developed in recent years as potential methods of solving problems in wave-guiding, vibration isolation, and energy harvesting. Yet to date, non-reciprocal acoustic behavior has not been demonstrated at a micro-scale and has largely been limited to frequency regions close to existing resonances or band gaps. In this paper, we present the design of MEMS metamaterial capable of demonstrating non-reciprocal acoustic behavior, which could potentially contribute to new applications at the micro-scale. Several chip designs are presented that contain longitudinal chains of symmetric parallel-plate unit cells that possess open loop controllable stiffness, designed in line with SOIMUMPs and POLYMUMPs fabrication standards. The device designs demonstrate that electronically controlled unidirectional bandgaps are achievable at the micro-scale with designs subject to traditional MEMS fabrication constraints.