Dual-directionally tunable metamaterial for low-frequency vibration isolation

This letter reports a dual-directionally tunable acoustic metamaterial comprising a matrix and two spiral beams with an embedded permanent magnet. Two types of vibration modes associated with band gaps can be excited under out-of-plane and in-plane excitations. The out-of-plane and in-plane transmissions of the metamaterial move toward two directions because of their modal characteristics when external magnets are introduced to tune the magnetic force monotonically. The mechanism of the dual-directional tunability is theoretically clarified. A composite dual-directionally tunable metamaterial prototype achieves the flexible tuning of the metamaterial band gap. Such effect provides broad application prospects for low-frequency vibration isolation in practical environments.