Tuning the working frequency of elastic metamaterials by heat

The limitation of passive elastic metamaterials is their fixed and narrow working frequency range. In this work, the manipulation of elastic waves using heat by an elastic metamaterial with resonant microstructures is presented for the first time. The effective density of the elastic metamaterial at different wave frequencies and temperatures is determined using effective continuum theory. We proved that the elastic metamaterial can have not only frequency - but also temperature-dependent negative effective density. By properly selecting materials for the building block, the effective mass density of the elastic metamaterial can be varied by increasing the temperature of the material. Elastic wave attenuation, waveguiding and wave focusing of the elastic metamaterial are then demonstrated by controlling the temperature of the elastic metamaterial. The developed methodology could significantly influence research areas including elastic wave attenuation, waveguiding, wave imaging and numerous other applications.