Phononic crystal sensors

A phononic crystal device is investigated as a sensor platform combining band gap engineering with resonant transmission. A slit cavity perpendicular to the propagation direction of ultrasound and placed in the middle of a phononic crystal causes a peak in the transmission spectrum with the peak frequency strongly dependent on the speed of sound of the liquid filling the slit. A resonant transmission peak through a plate regularly perforated by holes arranged in square lattice can also be found in case of normal incidence of sound. In this arrangement the peak frequency is strongly dependent on speed of sound of the liquid surrounding the plate and filling the holes. These findings are the basis of two resonant liquid sensor platforms based on phononic crystals.