Phononic crystal locally-resonant cavity for sensing metallic oxides nano-powders

•Distinguishing metallic oxide nano-powders using phononic crystal-based structures is of interest in this research.•The structures were designed based on the PMMA matrix with tungsten inclusions.•At first, the phononic directional coupler consisting of two coupled phononic crystal waveguides was used in detection of metallic oxides and its performance was investigated.•Secondly, the novel locally-resonant phononic crystal was introduced to distinguish the metallic oxides.•The resonant-based structure was designed in such a way that it has two hollow cylinders in its cavity to fill with target materials. Filling the hollows results in a shift of resonance frequency related to the type of target material. On the other words, each resonance frequency is attributed to the existence of a metallic oxide. [Display omitted] In this paper, the goal is to specify the type of metallic oxides including Fe2O3, Fe3O4, ZnO, Al2O3, MgO, TiO2, and NiO, provided as nano-powders. The phononic directional coupler is firstly employed and investigated to detect the materials. Subsequently, a novel locally-resonant structure based on the solid-solid phononic crystal is proposed to be used as a mass sensor. This structure consists of the PMMA background with tungsten inclusions and three resonant cavities for increasing the quality factor. There are two hollow cylinders inside the middle cavity filled with the materials whose type should be determined. Filling these cylinders with different target materials results in different resonant frequencies. To specify these frequencies, the transmission spectrum of the structure is obtained via the 3-dimensional finite element simulation method.