Dynamic control of Lamb modes in phononic crystals

This study explores the possibilities of temporal control of one-dimensional phononic crystal consisting of a homogeneous piezoelectric plate on which metallic electrodes are structured. Previous works [1] have shown that Lamb-type guided modes in these periodically structured piezoelectric ceramic plates exhibit a tunable frequency dispersion that can be controlled by external electric circuits connected to the electrodes. In this study we develop a device enabling changes in the electric boundary conditions (EBC) from one condition to another by making use of switches driven by a microcontroller. This device agility is exploited to perform dynamic control of the crystal properties. To our knowledge, this is the first study devoted to the dynamic modulation of Lamb-type guided waves. Here, we do not simply change the EBCs as a function of time, but we create a "wave" of modulation of properties. Broadband translation of Lamb-wave dispersion curves in the frequency-wavenumber space (f, k) are observed, depending on the modulation speed. Experimentally, the translation of the S0 mode is detected. The relationship between the position of static bands and the position of bands after temporal modulation obeys a very simple vector rule in the (f, k) space. [1] Phys. Rev. B 99, 094302 (2019).