Study of broadband propagation characteristic of quasi-fractal phononic crystal for enhanced sensing applications

This paper reports on bulk acoustic wave (BAW) resonators with quasi-fractal perforations for increased sensitivity in bio-sensing applications and on the broadband transmission line (TL) model of such resonators. Fractal perforations are implemented in BAW resonators to increase their surface area-to-volume ratio and to thereby enhance the sensitivity. We found that a further improvement is expected at higher resonance frequencies for the quasi-fractal phononic crystal (PnC) we have designed. This particular PnC has local resonances entailing strongly dispersive effective acoustic properties. Therefore, we have modeled the device implementing this PnC as a broadband dispersive transmission line (TL) to account for all the essential modes of longitudinal resonance. Our measurements, in very good agreement with this model, confirm the existence of the propagation mode in the PnC with enhanced projected sensitivity.