Project MON-MOST (China) Agreement 075-15-2023-580 (Code 13.2251.21.0203) (2023-2025) “Key technologies for the research and development of high-performance acoustic liquid sensors”

Head: Doctor of Physico-mathematical Sciences Kuznetsova I.E.
Responsible executor: Ph.D. of Physico-mathematical Sciences Kolesov V.V.

As a result of the work carried out at the first stage of research, the following main results were obtained:
1. The analytical review showed the existence of a large number of methods for studying the mechanical and electrical properties of liquids and solutions, including cultural media with microbiological objects on various physical principles, however, the use of acoustoelectronic technologies and the development of new devices based on them is of significant interest for the study of liquid media, and also the development of new designs and the search for new materials for sound pipes, which will increase sensitivity, reduce response time and expand the functionality of liquid sensors.
2. Conducted patent research on acousto-electronic liquid sensors based on delay lines and FBAR showed that the multi-parameter acousto-electronic liquid sensors proposed by project participants, based on the use of several probing acoustic waves, as well as multilayer structures with strong anisotropy, can be the basis for creating a new generation of modern elements of an electronic tongue, as well as devices for express analysis of biological fluids to detect pathogenic microorganisms.
3. The mathematical modeling of the propagation of acoustic Lamb waves and waves with transverse-horizontal polarization of zero and higher orders in the structure “air – piezoelectric plate – air gap – liquid” showed that the greater the dielectric constant of the liquid, the more strongly the phase velocity of the wave depends on the distance from the liquid to the plate, and also the lower the dielectric constant of the liquid, the lower the value of the maximum wave attenuation at a certain value of the conductivity of the liquid. It is concluded that in order to develop a method for remote determination of liquid conductivity, it is necessary to obtain calibration curves taking into account the dielectric constant of the measured liquid. Or, to develop a method, it is necessary to apply a machine learning method that will take into account the values of phase velocity and attenuation depending on the dielectric constant of the liquid and the distance of the piezoelectric plate from it.
4. As a result of mathematical modeling of the propagation of acoustic Lamb waves and waves with transverse-horizontal polarization of zero and higher orders in the frequency range from 3 MHz to 50 MHz in plates of lithium niobate, lithium tantalate with a thickness of 350 microns and in the air-paratellurite plate structure (TeO2) – ZnO film – air” in the absence of liquid, the following recommendations for experiments were made. To implement an experimental sample of a multiparameter sensor, you can select the A1 wave in the structure “C-axis-ZnO film – TeO2 Z cut plate.” It was found that the electromechanical coupling coefficient of this wave strongly depends on the direction of propagation, as does its phase velocity. This corresponds to the conditions for searching for structures with strong anisotropy of properties.
5. Mathematical modeling of the propagation of acoustic Lamb waves and waves with transverse-horizontal polarization of zero and higher orders in the frequency range from 3 MHz to 200 MHz in the structures “air – piezoelectric plate (thickness 350 μm) – liquid”, “air – paratellurite plate ( TeO2) – ZnO film – liquid” showed that the presence of an inviscid and non-conducting liquid on the surface of the structure has virtually no effect on the phase velocity of the waves, but leads to their attenuation. It was discovered that there are propagation directions in which the wave attenuation in the presence of liquid is stronger than for other directions in the same plane. This suggests the possibility of developing a liquid sensor based on the strong anisotropy of the properties of acoustic waves.
6. Mathematical modeling of the propagation of acoustic Lamb waves and waves with transverse-horizontal polarization of zero and higher orders in the frequency range from 3 MHz to 50 MHz in plates of lithium niobate, lithium tantalate with a thickness of 350 μm and in the air-paratellurite plate (TeO2) structure ) – ZnO film – air” at different ambient temperatures showed that the TCD range for waves in lithium niobate plates lies in the range from -115 ppm/C to -30 ppm/C, and for lithium tantalate the TCD of these waves lies in the range from -60 ppm/C to -10 ppm/C. This suggests that higher-order waves in lithium tantalate plates are less dependent on temperature changes than in lithium niobate plates. For waves recommended for creating a multichannel multiparameter liquid sensor, TCD is 0.05 ppm/C.
7. The developed microbiological method for obtaining bacterial cells based on a culture of methylotrophic mycobacteria (Methylobacterium, Rhodococcus) encapsulated with biogenic silver nanoparticles allows them to be obtained in an amount of at least 30 ml of analyte.
8. A study of the morphology and composition of the resulting bacterial cells based on a culture of mycobacteria encapsulated with biogenic silver nanoparticles confirmed their formation. A conclusion is drawn about the possibility of using the obtained microbiological objects to verify the biological acoustic liquid sensor being developed.
9. As part of the work, the Chinese participants developed a theoretical model of a parametric thin-film bulk acoustic resonator (FBAR) using the finite element method, taking into account reflections from boundaries and the excitation of spurious modes, carried out an experimental test of the model’s performance and analyzed the effectiveness of the measurement technique, as well as The influence of temperature on acoustic FBAR devices was studied.
All work planned for 2023 has been successfully completed. The results obtained correspond to, and in some cases exceed, the world level in this field of research.

The need for international cooperation is due to the possibility of access to the technological lines for creating acoustoelectronic devices from Chinese partners. In addition, due to the practical orientation of this work, an additional opportunity opens up for international cooperation to implement the results of this work into real sensor devices and organize their production.