Compact liquid analyzer based on a resonator with a lateral excitation electric field

A compact hardware-software complex for measuring the electrical and mechanical parameters of a liquid based on a piezoelectric resonator with a lateral exciting electric field has been developed. It is shown that the modulus of the electrical impedance of the resonator near the resonant frequency decreases monotonically with an increase in conductivity of the contacting liquid. The obtained dependences can be used as calibration curves for measuring conductivity in the range of 100-10,000 μS/cm. A method for the simultaneous determination of the modulus of elasticity, viscosity, and permittivity of a liquid using the electromechanical equivalent scheme was developed and tested on a mixture "water - glycerol" with the different glycerol content.

Microbial acoustic sensor test-system based on a piezoelectric resonator with a lateral electric field for kanamycin detection in liquid

A microbial test-system for real-time determination of low/residual concentrations of kanamycin in a liquid without the need for special labels is presented. The main element of the system was a piezoelectric resonator excited by a lateral electric field based on an X-cut lithium niobate plate 0.5 mm thick with two rectangular electrodes on one side. On the other side of the resonator, there was a 1.5 ml liquid container. As a sensory element we used Escherichia coli B-878 microbial cells, which are sensitive to kanamycin. For measurement 1 ml of this cells suspension was placed in a liquid container and then the test liquid in the amount of 2 μl containing kanamycin was added. The change in the real part of the electrical impedance of the resonator before and after the test liquid addition was used as an analytical signal which indicated the presence of kanamycin. The lower limit of determination of kanamycin turned out to be 1.0 μg/ml with an analysis time of 10 min. The test-system allows to detect kanamycin in the presence of such antibiotic as ampicillin and polymixin.

Newborns from women infected with COVID-19: somatic and metabolic status

To date, there are limited data regarding manifestations of new coronavirus infection in infants born of SARS-CoV-2 infected mothers, so the aim of this study is to investigate somatic and metabolic status of newborn infants born to mothers diagnosed with COVID-19. The investigation was carried out on the bases of Laboratory Diagnostic Department of Samara Regional Clinical Hospital named after V.D. Seredavin and the Department of Fundamental and Clinical Biochemistry with Laboratory Diagnostics of Samara State Medical University. Under observation were 85 newborns, including 35 born of healthy mothers and 50 born of COVID-19 mothers.The somatic status of all newborns was assessed using the Apgar scale at the 1st and 5th minutes after birth. Also all newborns had general and biochemical blood tests and newborns from mothers with COVID-19 were tested for the presence of SARS-CoV-2 RNA in oral and nasopharyngeal swabs. Thus, the study of somatic status revealed that of 50 neonates from women infected with COVID-19, only 18% were practically healthy, the rest had signs of prematurity, hypotrophy, perinatal CNS damage, diabetic fetopathy, pulmonary atelectasis, delayed intrauterine development, asphyxia. The metabolic state is characterised by decreased haemoglobin and platelets, increased concentration of total protein, including C-reactive protein, high transaminase activity, decreased sodium and chloride content. These parameters of general and biochemical blood tests can be considered as indicators for the evaluation of the condition of newborns from mothers with COVID-19.

Molecular profile of oral fluid in new coronavirus infection

Oral fluid is an alternative biological material that confirms correlations with blood parameters in various pathological conditions of the body. In order to find a non-invasive approach to stratification of patients with COVID-19 disease, molecular biomarkers of the oral fluid have been determined in patients with moderate coronavirus infection in comparison with clinically healthy individuals. It has been shown that proteomic, carbohydrate, macro- and microelement profiles of the oral fluid in coronavirus infection can be used for diagnostics. The features of protein metabolism were revealed: an increase in the content of total protein, urea; increased activity of enzymes aspartate aminotransferase, gamma glutamyl transpeptidase, creatine phosphokinase, alkaline phosphatase; changes in carbohydrate metabolism, which is expressed by an increase in glucose and lactate levels, an increase in lactate dehydrogenase activity, sodium, chloride, calcium, magnesium, iron content.

[Blood group and human diseases (review of literature).]

AB0 blood group antigens were discovered over a century ago; however, it is still important to study their role in development of various pathological conditions. Today it is known that antigenic determinants of this blood group are present not only on erythrocyte membrane but also on other cells and tissues: platelets, gastrointestinal epithelium and salivary glands, respiratory system cells. In the last decade, a large number of studies have appeared to reveal the relationship between a specific disease and blood group type, meta-analyses have been published. Previously, the authors have studied the metabolic status, cell composition and coagulation profile of clinically healthy individuals for more than on 180,000 donations, that allowed to identify groupspecific features for each blood group. This review presents generalized data on the association of such pathological conditions as coronary heart disease, thromboembolic complications, tumors of various localizations, inflammatory and destructive oral diseases, psychiatric and some infectious diseases with the presence or absence of antigenic determinants A and B. Carriers of blood group 0 (I) are generally more resistant to diseases, with the exception of H.pylori-associated gastrointestinal diseases. Carriers of «antigenic» blood groups A (II), B (III), AB (IV) are more susceptible to development of infectious, cardiovascular and cancer diseases. The presented data demonstrate clinical significance of the definition of group typing not only for selection of blood and its components during transfusion and transplantation, but also for diagnostics, determination of risk group and tactics for treatment patients with different nosologies.

Influence of the conductivity of a liquid contacting with a lateral electric field excited resonator based on PZT ceramics on its characteristics

The influence of the conductivity of a liquid contacting with a piezoelectric resonator with a lateral electric field based on a PZT piezoceramic plate was experimentally and theoretically investigated. In this resonator the shear component of the mechanical displacement, which does not lead to radiation losses upon contact with the liquid, was prevalent. The frequency dependences of the real and imaginary parts of the electrical impedance of the resonator in the frequency range 50-300 kHz showed the presence of three resonances at frequencies of 68.7, 97.8 and 264 kHz with the values of the electro-mechanical coupling coefficient of 12.2%, 14.7% and 6.5%, respectively. The quality factor of each resonance in contact with the liquid turned out to be significantly higher than the quality factor of the resonator with a longitudinal acoustic wave based on lithium niobate. The dependences of the maximum value of the real part of the electrical impedance of such a resonator on the conductivity of the liquid for each resonance were obtained. This experimental data turned out to be in a good agreement with theoretical results obtained by using the method of equivalent circuit.

[Сlinicmolecular indicators of inflammatory destructive damage of the oral cavity in periodontitis in persons with various group accessories of blood.]

In order to find a connection between the alteration of oral tissues and genetic predisposition to inflammatory and destructive processes in oral media, the cytokine profile of the oral fluid of clinically healthy individuals was determined for various blood group affiliations according to the AB0 system. The group-specific features of individuals with B(III) blood group were revealed: an increase of 32,5% in the content of interleukin-6 and 63,1% in the content of interleukin-8 compared with similar data for people with 0(I), A(II), AB(IV) blood groups, which can predispose to the greatest activity of the inflammatory process in the oral cavity in individuals with antigen B. Confirmation of this fact is an increase of IgA antibodies to gliadin in the blood among patients with chronic generalized periodontitis with B(III) blood group, up to 5,00 U/ml (p<0,01), which indicates the processes of acute inflammation, and along with an increase in blood IgG antibodies to transglutaminase in comparison with a group of clinically healthy individuals, it serves as an indicator of damage to the body's connective tissue at the molecular level. When examining the dental status, pronounced clinical manifestations of chronic generalized periodontitis were found in patients with A(II) blood group, the molecular foundation of which is the highest content of IgA and IgG antibodies to transglutaminase in the oral fluid (0,35 U/ml and 0,45 U/ml), which contributes to the activation of periodontal-destroying inflammatory and inflammatory processes, obviously, with a tendency to the chronic course of the disease. The studies performed allowed us to analyze in clinically healthy individuals a predisposition to alternative processes in oral environments, using gradation by group blood affiliation.

New approach for determination of antimicrobial susceptibility to antibiotics by an acoustic sensor

For the first time, a rapid method was proposed to determine the susceptibility of Escherichia coli cells to antibiotics by the example of ampicillin by using a biological sensor based on a slot mode in an acoustic delay line. It has been established that an indicator of the antibiotic activity to microbial cells is the difference between the recorded sensor's signal before and after exposure cells with antibiotic. The depth and frequency of the peaks of resonant absorption in the frequency dependence of the insertion loss of sensor varied after adding an antibiotic with different concentrations to the microbial cells. By using the acoustic sensor based on slot-mode a criterion of E. coli sensitivity to ampicillin was established. The advantages of this method are the ability to carry out the analysis directly in the liquid, the short analysis time (within 10-15 min), and the possibility to reusable sensor.

The sensor for measuring the micro-displacements based on the piezoelectric resonator with lateral electric field

Theoretical and experimental studies of the influence of a thin metal film on the characteristics of a piezoelectric resonator with a lateral electric field showed the possibility of creating a micro-displacement meter in the range of 10-300 μm. For the experiments, two resonators based on the plates of PZT piezoceramics with a thickness of 3.56 and 4.46 mm with resonant frequencies of ~96 and ~260 kHz for both resonators were used. It has been experimentally established that in both cases, with an increase in the width of the gap between the free side of the piezoelectric resonator and thin aluminum film, the frequency of the parallel resonance and maximum value of the real part of the electrical impedance increase and reach saturation. Besides, it has been shown that the relative change of these values with a change in the width of the gap in the range 10-300 μm increases with decreasing the thickness of the resonator. In this case, the frequency of the series resonance practically does not change. It has been also established that the sensitivity of the resonator to the presence of a conducting film at the resonant frequency of ~96 kHz is significantly higher in comparison with the resonant frequency of ~260 kHz. The experimental results are in the qualitative agreement with the theoretical data.

The effect of the conductivity of a film located near a piezoelectric resonator with a lateral electric field based on the PZT ceramics on its characteristics

In this paper, we investigated theoretically and experimentally the effect of the conductivity of the film located in the immediate vicinity of the free side of a piezoelectric resonator based on the PZT ceramics on its characteristics. It is shown that with increasing the conductivity of the film at first the parallel resonant frequency does not change, then it decreases in a certain interval and after that remains practically constant. With increasing the width of the gap between the film and the resonator, the resonant frequency increases and reaches the saturation. At that the degree of the total frequency change decreases with decreasing the conductivity of the film. We also investigated the dependence of the maximum value of the real part of the electrical impedance on the film conductivity at the different values of the width of the gap between the film and the resonator. The dependences of the maximum value of the real part of the electrical impedance on the width of the gap between the film and the resonator are also obtained for different values of the film conductivity. A comparison of the theoretical and experimental data showed their good qualitative agreement.

[Coagulation test features depending on the AB0-blood groups system antigenic composition.]

The maintenance of normal blood flow through the vessels is the result of the coordinated work of the coagulation and anticoagulation systems of our body. The balance of this system depends on many factors, including endothelial, humoral, platelet ones, however, we still lack knowledge about the effect of antigenic determinants on the state of the hemostatic system. This study is devoted to assessing the effect of the presence and absence of antigens on the AB0 system, presented on erythrocyte and platelet membranes, on hemostatic parameters. The study was conducted in the Clinics of Samara State Medical University and consisted of127 clinically healthy individuals who underwent a general analysis and biochemical blood analysis, 52 people with the most stable indicators of cell composition and metabolic profile were selected for a coagulation test, including determination of the activity of coagulation factors and routine tests. A significant decrease in the activity of the VIII and VII coagulation factors was revealed, as well as an increase in the prothrombin time in patients with 0 (I) blood group compared to the "antigenic" blood groups. The presence of biological variation for indicators of external and internal coagulation paths was noted, depending on the group of blood belonging to the AB0 system. The findings suggest that there is an increased susceptibility to bleeding in patients with 0 (I) blood groups due to the absence of antigenic determinants on the cell membrane, while for "antigenic" blood groups, on the contrary, there is a susceptibility to thrombosis due to increased activity of the components of the coagulation system.

Effect of the conductivity of a thin film located near the acoustic delay line on the characteristics of propagating SH0 wave

The results of the study of the influence of the conductivity of a thin film located with a certain gap above the acoustic delay line on the characteristics of propagating acoustic wave with a quasi-shear-horizontal polarization (SH₀) are presented. The delay line was made of Y-X lithium niobate plate with a thickness of 200 μm containing two interdigital transducers for exciting and receiving SH₀ wave. The operating frequency range of the delay line was equal to 2.6-3.8 MHz. The 1 mm thick glass plate with a film of the given conductivity applied on one plate's side was placed above this delay line with the some air gap. The change in the phase of output signal of the delay line was measured at the various values of the width of this gap. As films with the various values of the conductivity, tin dioxide films deposited on a glass plate by high-frequency reactive magnetron sputtering in the oxygen-argon mixture were used. It has been shown that the velocity of SH₀ wave propagating in the delay line under investigation depends on the film conductivity and the width of the gap between the delay line and conductive film. The dependences of the change in the SH₀ wave velocity on a width of the gap between the surface of the delay line and conductive film were constructed, as well as on the film conductivity. The comparison of the experimental results with the theoretical data showed their good agreement.

Analysis of the microbial cell-Ab binding in buffer solution by the piezoelectric resonator

The possibility of the registration of the interaction of the cells Azospirillum lipoferum Sp59b with the specific antibodies directly in the conducting suspensions by using an acoustic sensor was shown. The main element of the sensor is a piezoelectric resonator with a lateral electric field. The analysis is based on a comparison of the resonator's electrical impedance before and after the specific biological interaction between the cells and antibodies. By using this sensor one can detect and identify the bacterial cells directly in the buffer solution with the conductivity between 2.4 and 20 μS/cm. The minimum detectable concentration of the bacterial cells turned out to be ∼10³ cells/ml and for a short time (less than 10 min). Also the possibility of the detection of the cells in the presence of the extraneous microflora was shown. The results provide the opportunities for the development of a new class of the methods for the analysis of the microbial cells in real-time directly in the buffer solution.

The influence of the metal film, placed close to the free side of the piezoelectric lateral electric field excited resonator, on its characteristics

The influence of the width of the gap between the free side of the piezoelectric lateral electric field excited resonator and the metal film placed on the dielectric plate on the frequencies of the parallel and series resonances was experimentally and theoretically studied. The measurements were carried out in the temperature range of 14-45 °C. It has been shown that the change of the gap width from 0 up to 3.5 mm leads to the change of the parallel resonant frequency on 1.3% at the constant temperature. At the same conditions the change of the series resonant frequency does not exceed 0.07%. Theoretical analysis quantitatively confirmed the experimental dependencies of the aforementioned frequencies on the gap width at the room temperature. At that the maximum difference between the theoretical and experimental values of the parallel and series resonant frequencies in all cases does not exceed 1.2%. The obtained results may be used as the basis for the development of the sensors for the measurement of the displacement in the interval of 0.2-2 mm in the temperature range of 15-45 °C.

The influence of the conducting film on the characteristics of the lateral electric field excited piezoelectric resonator

The effect of a thin layer with the finite surface conductivity located near the lateral electric field excited resonator on its characteristics is studied theoretically and experimentally. It has been shown that for the fixed distance between the free side of the resonator and conducting layer with increasing the surface conductivity of the layer the resonant frequency of the parallel resonance remains initially practically constant, then sharply decreases in a certain range and then insignificantly changes. For the fixed value of the layer conductivity the parallel resonant frequency increases at the increase in the gap between the resonator and layer and then achieves the saturation. The maximum change in the frequency of the parallel resonance corresponds to a zero gap when the layer conductivity varies over the wide range is equal to ∼1%. The frequency of the series resonance decreases only by ∼0.08% due to the change in the layer conductivity. The obtained results may be useful for the development of the gas sensors based on the lateral electric field excited piezoelectric resonator conjugated to the gas sensitive film, the conductivity of which changes in the presence of the given gas.

The influence of viscous and conducting liquid on the characteristics of the slot acoustic wave

The influence of the liquid with the different values of conductivity, permittivity, and viscosity on the characteristics of the slot mode in the structure consisting of delay line with propagating shear - horizontal acoustic wave of zero order (SH₀) and upper piezoelectric plate separated by the air gap was experimentally investigated. The delay line made of the Y-X lithium niobate plate 0.2mm thick contained two interdigital transducers for the excitation and reception of acoustic wave in the frequency range of 2.6-3.8MHz. The upper plate represented the 0.5mm thick plate of Z-X lithium niobate. The excitation of the slot mode led to the appearance of the sharp resonant peaks on the frequency dependencies of insertion loss and phase of the output signal. It has been found that the depth and frequency of these peaks depend on the parameters of liquid contacting with the upper plate. The possibility of the use of the slot mode in the pointed structure for the identification of liquids with the different values of the conductivity, viscosity, and permittivity was shown. The qualitative explanations of the obtained experimental results are presented.

The acoustic sensor for rapid analysis of bacterial cells in the conductive suspensions

The possibility of using the acoustic sensor on the basis of a two-channel delay line for rapid analysis of bacterial cells in the conductive suspensions was investigated. The dependencies of change in phase and insertion loss of output signal of the sensor on conductivity of buffer solution with various concentrations of cells due to a specific interaction "bacterial cells - mini-antibodies" for electrically open and electrically shorted channels of delay line were measured. It has been found that these changes have the most values for the electrically open channel. It has been also shown that the sensor rapidly responds to the specific interaction and the time stabilization of the phase and insertion loss of output signal is less than 10min.

The biological acoustic sensor to record the interactions of the microbial cells with the phage antibodies in conducting suspensions

The acoustic biological sensor for the analysis of the bacterial cells in conducting suspension was developed. The sensor represented the two channel delay line based on the piezoelectric plate of Y-X lithium niobate thick of 0.2mm. Two pairs of the interdigital transducers (IDT) for the excitation and reception of shear horizontal acoustic wave of zero order (SH₀) in each channel were deposited by the method of photolithography. One channel of the delay line was electrically shorted by the deposition of thin aluminum film between IDTs. The second channel remained as electrically open. The liquid container with the volume of 5ml was fixed on the plate surface between IDTs by the glue, which did not cause the additional insertion loss. For the first time the influence of the conductivity of the cell suspension on the registration of the specific and nonspecific interactions of the bacterial cells with phage-antibodies (phage-Abs) was studied by means of the developed sensor. The dependencies of the change in insertion loss and phase of the output signal on the conductivity of the buffer solution at specific/nonspecific interactions for the electrically open and shorted channels of the delay line were obtained. It was shown that the sensor successfully registered the interactions of microbial cells with phage-Abs in the range of the conductivity of 2-20 μS/cm on the model samples A. brasilense Sp245 - specific phage-Abs. The sensor in the time regime of the operation fast reacted on the specific/nonspecific interaction and the time of the stabilization of the output parameters did not exceed 10min.

Gasoline sensor based on piezoelectric lateral electric field excited resonator

It has been shown that by using piezoelectric lateral electric field excited resonators based on X - cut LiNbO₃, one can determine the octane number of gasoline. The measured dependence of gasoline permittivity on its octane number has shown that there is an ambiguous connection between pointed parameters. We have demonstrated both theoretically and experimentally that the value of the real part of the electrical impedance on the frequency of parallel resonance uniquely associates with the octane number of gasoline contacting the free side of the resonator. At that the frequency of parallel resonance does not depend on permittivity/octane number of gasoline. An example of determination of the octane number of a mixture of two different samples of gasoline is given.

Composite lateral electric field excited piezoelectric resonator

The novel method of suppression of parasitic oscillations in lateral electric field excited piezoelectric resonator is suggested. Traditionally such resonator represents the piezoelectric plate with two electrodes on one side of the plate. The crystallographic orientation of the plate is selected so that the tangential components of electric field excite bulk acoustic wave with given polarization travelling along the normal to the plate sides. However at that the normal components of field excite the parasitic Lamb waves and bulk waves of other polarization which deteriorate the resonant properties of the resonator. In this work we suggest to separate the source of the HF electric field and resounded piezoelectric plate by air gap. In this case the tangential components of the field in piezoelectric plate do not practically weaken but normal components significantly decrease. This method is realized on the composite resonator having the structure "glass plate with rectangular electrodes - air gap - plate of 128 Y-X lithium niobate." It has been shown that there exist the optimal value of the width gap which ensure the good quality of series and parallel resonances in frequency range 3-4MHz with record values of Q-factor of ∼15,000 in both cases.

Array of piezoelectric lateral electric field excited resonators

An array containing two resonators placed on X-cut lithium niobate plate has been experimentally investigated. The resonator's lateral electric field was directed along the Y-crystallographic axis. It has been shown that stable resonance exists for a longitudinal acoustic wave propagating along the X-axis in the area between the electrodes. A layer of special damping coating was deposited around the resonators and on the part of electrodes to suppress parasitic oscillations induced mainly by Lamb waves. Frequency dependences of the real and imaginary parts of electric impedance/admittance were measured for every resonator to find resonant frequency and Q-factor with series and parallel resonances. The optimal values of width of electrode coating for every resonator were revealed which provide good resonance quality. The measurements of parameter S12, which characterizes a degree of acoustical coupling between the resonators, have shown its value to be higher than 50dB in the absolute value in all the cases considered. This means that the resonators under study are entirely acoustically decoupled. Thus it has been demonstrated that the damping layer not only provides a sufficiently good quality of every resonator's resonance, but it also assures their entire acoustical decoupling.

The peculiarities of propagation of the backward acoustic waves in piezoelectric plates

The characteristics of backward acoustic waves in piezoelectric plates under different electrical boundary conditions were investigated. It has been shown that electrical shorting of the plate leads to increasing and decreasing the phase velocity for backward and forward branches, respectively. The peculiarities of the hybridization effect of backward waves were studied.

Investigation of acoustic waves of higher order propagating in plates of lithium niobate

This paper presents theoretical investigation of higher order acoustic plate waves propagating in single crystals of lithium niobate. The dependencies of wave velocity and electromechanical coupling coefficient of antisymmetric, symmetric, and shear horizontal modes on the parameter hf (h=plate thickness, f=operating frequency) are calculated as a function of propagation direction on X-, Y-, and Z-cut lithium niobate plates. It is found that several modes can provide values of K2 that are much greater than can be obtained with surface acoustic waves (SAWs). For example, K2 as high as 0.26 and 0.38 can be obtained from SH1 and A2 modes, respectively. This compares with a maximum value of K2=0.055 for SAWs. It is further shown that there are several crystal cut and propagation directions that can allow efficient excitation and detection of a single mode with minimal interference due to other modes.

Shear-horizontal acoustic waves in piezoelectric plates bordered with conductive liquid

The influence of a conductive liquid on the characteristics of shear-horizontal acoustic waves of zeroth order (SH0 mode) propagating in thin piezoelectric plates of lithium tantalate, lithium niobate, and potassium niobate was investigated. Experimental results obtained for SH0 mode devices fabricated on lithium niobate plates are found to be in good agreement with theory. The data presented in this paper is useful for a proper design of various acoustic wave sensors operating in contact with conductive liquids.

Influence of conducting layer and conducting electrode on acoustic waves propagating in potassium niobate plates

The influence of a thin conducting layer and a conducting electrode on the characteristics of acoustic waves propagating in thin plates of potassium niobate is investigated theoretically. The variations in velocity and attenuation as high as 50% and 30 dB per wavelength, respectively, can be achieved for a change in conductance of the thin film layer from 10(-7) to 10(-5) S.

Investigation of acoustic waves in thin plates of lithium niobate and lithium tantalate

The general properties of fundamental antisymmetric A0, symmetric S0, and shear horizontal SH0 acoustic waves propagating in thin piezoelectric plates have been theoretically investigated on samples of lithium niobate (LiNbO3) and lithium tantalate (LiTaO3). The results obtained will be useful for a proper development of various physical, chemical, and biological sensors and devices for signal processing based on plate acoustic waves.