3D phononic-fluidic cavity sensor for resonance measurements of volumetric fluid properties

Additively manufactured 3D phononic crystals have demonstrated wide acoustic band gaps and strong acoustic mode suppression not attainable by corresponding 2D designs. In this work we present the combination of these air-filled 3D structures with an enclosed fluidic cavity resonator in a single printed sensor element for the first time. This combination drastically improves the sensitivity of the cavity resonance signal. An analytical 1D calculation demonstrates this phononic-fluidic sensor concept and is used to approximate suitable geometric designs, which are subsequently fabricated using microstereolithography printing. Our experimental results show clearly separated resonance frequencies for different liquids introduced into the cavity, with frequency shifts correlating to differences in density and speed of sound.