The influence of humidity on the density, shear elastic module, viscosity, and thickness of the mushroom Pleurotus eryngii and Ganoderma lucidum mycelium films was studied. These data were obtained by comparing the theoretical and experimental frequency dependencies of the complex electrical impedance of bulk acoustic wave (BAW) resonator loaded by mycelium film using the least-squares method. This procedure was performed for the BAW resonator with pointed films for the relative humidity range of 17%–56% at the room temperature. As a result, the changes of the density, shear elastic module, viscosity, and thickness of the films under study, due to the water vapor adsorption, were determined. It has been established that the properties of mycelium films are restored after removing from the water vapor. So, these results show the possibility of using investigated mycelium films as sensitive layers for acoustic humidity sensors.

No abstract

Evanescent acoustic waves are characterized by purely imaginary or complex wavenumbers. Earlier, in 2019 by using a three dimensional (3D) finite element method (FEM) the possibility of the excitation and registration of such waves in the piezoelectric plates was theoretically shown. In this paper the set of the acoustically isolated interdigital transducers (IDTs) with the different spatial periods for excitation and registration of the evanescent acoustic wave in Y-cut X-propagation direction of lithium niobate (LiNbO3) plate was specifically calculated and produced. As a result, the possibility to excite and register the evanescent acoustic wave in the piezoelectric plates was experimentally proved for the first time. The evanescent nature of the registered wave has been established. The theoretical results turned out to be in a good agreement with the experimental ones. The influence of an infinitely thin layer with arbitrary conductivity placed on a plate surface was also investigated. It has been shown that the frequency region of an evanescent acoustic wave existence is very sensitive to the changes of the electrical boundary conditions. The results obtained may be used for the development of the method of the analysis of thin films electric properties based on the study of evanescent waves.

In the paper, the results of production of Ag inkjet printed interdigital transducers to the acoustic delay line based on Y-cut X-propagation direction of lithium niobate plate for the frequency range from 1 to 14 MHz are presented. Additionally, morphological, structural, and electro-physical characteristics of the obtained electrodes were investigated. Mathematical modeling of the excitation of acoustic waves by these electrode structures was carried out. Comparison of the theoretical results with experimental ones showed their qualitative and quantitative coincidences. It was shown that conventional inkjet printing can replace the complex photolithographic method for production of interdigital transducers for acoustic delay lines working up to 14 MHz. The resulting electrode structures make it possible to efficiently excite acoustic waves with a high value of electromechanical coupling coefficient in piezoelectric plates.

No abstract