Acoustic waves guided by a fluid layer on a piezoelectric substrate

Abstract

This paper theoretically studies the propagation and the generation of leaky acoustic waves in a fluid layer enclosed between the half-infinite YZ-LiNbO3 (lithium niobate) substrate coated with a thin SiO2 (silicone dioxide) layer and the half-infinite domain occupied by silicone rubber. The plane wave spectrum in the structure is computed, and the specific features of the behavior of the real and imaginary parts of the leaky wave velocity depending on the fluid layer thickness and the electric boundary conditions are analyzed. Besides, the numerical estimations are made of the coupling-of-mode (COM) parameters describing a periodic grating deposited on the LiNbO3 substrate under the SiO2 layer. The dependence of the COM parameters is investigated on characteristics and conditions specifying the structure, such as the fluid layer thickness, the SiO2 coating thickness, and the presence or the absence of projections on the SiO2 coating face in contact with the fluid. In particular, it is found that the reflection and the transduction coefficients remain high enough even when the fluid layer is several wavelengths thick provided that the frequency is close to the value f0=vl0′∕2p, where vl0′ is the real leaky wave velocity at the zeroth thickness of the fluid layer and p is the grating period. It is also found that projections on the SiO2-fluid interface significantly increase the reflection coefficient.

Combination of surface acoustic wave measurement and impedance spectroscopy for detection of cell adhesion process

“…One possibility is the formation of a thin layer as it appears while the cells express their proteins of ECM. Through acoustic wave modeling (see for instance [7]) was found, that if the shear elasticity and density of growing layers are small compared to the sensor substrate, always an increase of the wave propagation speed and thus an increase of the resonant frequency would occur. A change in the range of 35 ppm per nm layer thickness was calculated.…”

A new tool to assess mechanical and dielectric properties of tissues

“…The most notable increase of resonant frequency during cell adhesion can arise from the shear elasticity of ECM or of the cells as implied from acoustic wave modeling (details of the method used are given in [11]). In addition, the changes in the dielectric properties of the ECM/cell coating on the SAW resonator compared to the situation at the beginning of the measurement can affect the SAW resonant frequency in the observed manner (figs.…”

Acoustic waves in LiNbO<inf>3</inf>/SiO<inf>2</inf>/water/silicon rubber structures

“…The wave field includes the mechanical displacements in the solids, the pressure in water, and the electric potential everywhere except the interior of the electrodes. Since the sound velocities in silicone rubber are far smaller than the sound velocities in all other materials, we neglect the elastic fields in silicone rubber, considering it as vacuum with dielectric permittivity ε sr (see additional comments in [8]). …”

“…The wave fields outside the cell, i.e., the electric potential above EJ as well as the mechanical displacements and the electric potential below AF, are saught as superpositions of plane modes (the eigenfunction expansion method). The unknown amplitudes of these modes are introduced into the FEM problem as additional degrees of freedom defined on EJ and AF (see [8] for more details). …”