Highly tunable low frequency metamaterial cavity for vibration localization.

Metamaterial cavity has gathered much attention recently due to its capability of localizing vibration energy. Despite the active research, however, there are still big technical challenges not solved yet. Especially, there has been no approach to maximize the wave localization performance of metamaterial cavity; therefore, there has been a possibility that obtained cavity mode does not show sufficiently high performance. Also, there is a tunability issue that whole metamaterials should be re-designed to tune the cavity frequency. Here, we present the metamaterial cavity system that can control its cavity mode frequency from 589 to 2184 Hz by adjusting the cavity length from 140 to 60 mm without re-designing the whole metamaterial based on the broad bandgap. Also, the performance of the obtained cavity mode can be improved by adjusting the length of the side beam attached to the metamaterial; the displacements are amplified more than 18-110 times. Consequently, one may easily obtain the highly localized vibration energy at the desired frequency by adjusting two geometric parameters based on the proposed metamaterial cavity system. Numerical and experimental supports are provided to validate our new metamaterial cavity system. This metamaterial cavity system is expected to provide a guideline for localizing vibration energy in various applications, such as energy harvesting, sensing or vibration dissipation.