A novel lamb - mode liquid sensor array

New type of an acoustic plate mode: quasi-longitudinal normal wave

“…Defining the polarization of the mode is based upon two well-known experimental data [3,11,12]: (i) an acoustic wave, having nonzero vertical displacement U 3 at the liquid/solid interface and large propagation velocity v n as compared with compressional wave velocity in the liquid v lq , is suffered from attenuation a because the wave energy is continuously radiated into the liquid medium--therefore, the magnitude of the U 3 component at the plate surface may be qualitatively estimated for any mode from the value of the attenuation a n measured for water as a liquid with low viscosity g: the less the a n , the smaller the U 3 for a given mode; (ii) an acoustic wave, having nonzero shear-horizontal displacement U 2 at the liquid/solid interface, is suffered from viscoelastic loss increased proportionally to the liquid viscosity g--therefore, the magnitude of the U 2 component at the plate surface may be qualitatively estimated for any mode from the attenuation a n measured for glycerin as a liquid with high viscosity g: the less the a n , the smaller the U 2 for a given mode. As a result, modes, whose attenuation a n is relatively small for both liquids, contain smallest U 3 and U 2 components, and, thereby, might be identified as quasi-longitudinal.…”

“…They show that for quartz plate with free surfaces and normalized thickness H =k ¼ 1:485 the attenuation of the modes a n depends on the mode order n and the type of the liquid. For water (small viscosity) the modes ordered as n ¼ 2, 3,6,8,9,13,19,20,25,27, 29 are characterized by low attenuation a n < 10 dB and because of that they possess small vertical component U 3 . Furthermore, if compared the same modes with each other for glycerin (large viscosity), there is only mode n ¼ 6, whose attenuation is noticeably small ða 6 < 4 dB).…”

“…The author of the paper has already reported on a new type of an acoustic wave belonging to the family of the normal plate modes [3]. In this article he presents detailed properties of the wave for ST, x-quartz plates with free surfaces.…”

Viscosity and density decoupling method using a higher order Lamb wave sensor

“…Another limitation is from the widely adopted delay line configuration [24][25][26]. Although the Lamb wave sensor is a powerful device for liquid sensing [27][28][29][30][31], the delay line configuration has issues of low quality factor, low stability and low reproducibility.…”

A CMOS-compatible lamb wave resonator for liquid properties sensing

“…However, most of the reported acoustic wave sensors employed delay line as the sensing element [21][22][23]. Delay line faced issues of low quality factor, low stability and reproducibility, from which signals were hard to extract [10].…”