Experimental realization of broadband tunable resonators based on anisotropic metafluids

This letter demonstrates the mechanical tuning of modes confined in two-dimensional acoustic cavities based on anisotropic metafluids. The employed metafluids have been designed with effective parameters such that the radial component of the sound speed tensor keeps constant and the acoustic impedance remains finite along the tuning. It is shown that mode frequencies can be mechanically down shifted to extremely low values. Experiments confirm the model predictions and let us to conclude that this type of resonators can be employed for the miniaturization of standard resonators based on isotropic fluids such as air.