The neighbouring membranes are overlapped to create mechanical coupling. By changing the distance between etch holes, the researchers were able to control the amount of lattice coupling. Their work has been theoretical, beginning with a discrete mass-spring model and the many forces on each element (see figure 2).
They then proceeded to in-depth, deep-dive physics analysis of the lattice’s electromechanical and related properties, as well as its responses. Finally, they went beyond the theory and its postulated performance by fabricating and evaluating several devices. By applying a dc gate voltage VT to create a voltage-dependent electric field, they were able to significantly shift the frequency bands of the device (see figures 3 and 4).
It’s desirable that a physical channel being used as a waveguide be both stable and defect-free for reliable, consistent performance. However, they noted that energy transport in high-frequency mechanical systems, such as these microscale phononic devices, is particularly sensitive to defects and sharp turns because of backscattering and losses.
Since actual devices aren’t perfect, they also investigated the influence of possible fabrication errors that happen during the deposition process. In this case, the non-uniformity in the film thickness causes disorder in the mass matrix parameters used in the many equations of the dynamics.