Systematic design of 2D and 3D vibroacoustic fluidic cavity sensors using topology optimization

In this research we investigate a novel sensor concept, which utilizes a standing acoustic wave inside a liquid-filled cavity to probe volumetric properties of a fluid analyte. However, realizing a high-Q cavity resonator is a challenge because of low acoustic impedance contrast between liquids and solids. In our previous studies, we surround the cavity resonator with phononic crystal layers that provide a strong cavity resonance within the phononic band gap. The quality factor drastically depends on the geometry of the metamaterial lattice. Therefore, the main aim of this study is to find an optimal material layout of the solid domain around the cavity by employing topology optimization. We formulate the optimization problem as maximization of the Q-factor of the cavity resonance. We consider the sensor as a fully coupled vibroacoustic system, taking into account material losses and frequency-dependent material properties. Since resonance problems are very sensitive to minor variations in geometry, we apply a gray scale suppression constraint to minimize the influence of geometrical uncertainties and make the optimized designs suitable for additive manufacturing