RU2712723C1 - Acoustic multichannel analyzer of micro samples of liquid media - Google Patents

Abstract

FIELD: analysis of liquid media.

SUBSTANCE: use for analysis of liquid media, including biological fluids. Summary of invention consists in the fact that analyzer comprises a piezoelectric plate in the center of which a radiating IDT is located. On both sides of the plate in direction of radiation with a gap receiving IDT are arranged, which form acoustic channels for samples of analyzed liquid and reference liquids. Piezoelectric plate has a thickness on the order of the length of the acoustic wave and provides excitation of plate-like vibration modes of PVM of several orders with different frequency and different direction of energy flows. Receiving IDT are arranged in pairs at equal distances relative to the geometric center of the radiating IDT and at angles selected from the condition of receiving PVM energy flows at discrete excitation frequencies of the emitting IDT. Receiving IDT pins are parallel to radiating IDT pins. Distances on which the receiving IDTs are placed in each channel relative to the geometrical center of the emitting IDT for each pair are the same. Acoustic channels for samples contain two cuvettes – one for analyzed, and another – for reference liquid media – with open neck of equal size and shape in form of sectors, which are symmetrical relative to plane passing through geometrical center of emitting IDT. Bottom of the cuvette is a piezoelectric plate.

EFFECT: high accuracy of analyzing liquid micro samples.

6 cl, 6 dwg

Description

The invention relates to measuring technique using acoustic vibrations and can be used to analyze liquid media, including biological fluids.

Conventional circuits of ultrasonic instruments for analyzing liquids contain two channels, each of which includes an emitter and a receiver of ultrasonic vibrations, and a measuring circuit. One of the channels is a reference, for example, it contains a reference liquid, and the second is a measuring one with a test medium (see Ultrasound, small. Encyclopedia, M., SE, 1979, edited by I.P. Golyamina, pp. 235-237) . Piezoceramic transducers are used as sources and receivers (see, for example, Ultrasonic monitoring and process control / NI Brazhnikov, VA Belevitin, AI Brazhnikov. - Moscow: Heat engineer, 2008. ISBN 5-98457 -056-4).

A large number of technical solutions are described, where Rayleigh-type surface acoustic waves (SAWs) and / or plate vibration modes (PMCs) excited in substrates in contact with which the medium under study are used as a tool for studying various physicochemical parameters of liquid media.

A sensor for detecting chemical vapors using surfactants (US 5325704 (A), US Army, 1994-07-05) provides for the simultaneous detection of several chemical agents. The sensor has a piezoelectric substrate and a bi-directional transducer of acoustic waves on the substrate. There are also several pairs of identical acoustic sensors and reference channels on the substrate, each on opposite sides of the sensor in mirror image. Reference channels are protected from environmental conditions, while sensitive channels are exposed to such conditions. The RF signal is supplied to the converter, causing the acoustic signal to propagate into each of the sensitive channels and reference channels. The output from the converter is then detected.

A multi-frequency acoustic sensor for analyzing liquids and gases is also described (US 5235235, Martin et al., 08/10/1993). The sensor includes several pairs of interdigital transducers (IDT) with different periods, which are located on the piezoelectric plate in one line and generate surfactants and PMCs and differing in frequency, the energy flows of each of which are collinear to the direction of propagation. Based on the difference in the interaction of acoustic waves excited at different frequencies with mass, viscous and other plate loads, the device is able to identify a gas or liquid mixture by several parameters. However, the use of a large number of IDTs located in a line entails an increase in the dimensions of the device and undesirable distortion of those acoustic waves that, propagating in one direction, pass through a large number of IDTs in the internal part.

In patent RU 2393467 C2, TECHNOLOGY INDUSTRIAL RESOURCE INSTITUTE (CN), INSTITUTE OF RADIO ENGINEERING AND ELECTRONICS OF THE RUSSIAN ACADEMY OF SCIENCES (RU), 06/27/2010 - a device for PMK for simultaneous determination of viscosity and temperature of a liquid in 100-1000 sample volumes is described . The device contains a pair of input and output IDTs with a period λ of the thickness h of a plate of LiNbO ₃ 128 ° Y, X + 90 ° - a cut formed on one surface of the said plate, designed to generate and receive PMC, the interaction zone of the PMC with a sample of liquid formed on the opposite surface of the plate, where the presence of liquid causes detectable changes in the speed and amplitude of the PMC; means generating an electrical signal of the corresponding frequency supplied to the input IDT; means receiving a signal from the output IDT. Changes in speed and amplitude are recorded by the magnitude of the phase shift or by the introduced path loss. The disadvantage of this device is the lack of a reference acoustic channel, which does not allow for temperature variations in the properties of the wave and the probe fluid.

In the invention (RU 2408881 C1, OJSC "Research Institute" Elpa ", 10.01.2011) a device for determining the characteristics of a liquid is described, comprising a plate sound duct, on one surface of which there is a liquid cuvette, the bottom of which is a sound duct, and electroacoustic transducers on the other excitation and reception in the PMK sound conduit The sound conduit is configured to excite at least five vibration modes in it, each of which is characterized by individual sensitivity to the desired parameters of density, viscosity, electric conductivity, dielectric constant and liquid temperature. The phase responses of the modes are recorded in the presence of the tested and reference liquids, as well as in their absence, after which the values of the independent values of the tested liquid are determined by numerical methods according to the system of equations. The disadvantage of the device is the effect on the measurement cross the sensitivity of each mode to all fluid parameters.

In another invention (RU 2533692 C1, IRE named after V.A. Kotelnikov, Russian Academy of Sciences, November 20, 2014), a multisensor acoustic array is described, in which IDTs form sets of acoustic channels whose acoustic wave propagation directions intersect at the conditional center of the plate and the area around conditional center in the form of a circle for testing. Acoustic channels are made with the possibility of excitation in the plate of the PMC family with a wavelength less than or equal to the thickness of the plate. IDTs in different channels have different values for the period of the pins and / or angles. In the invention “Acoustic sensor of the electronic nose and electronic language system” (RU 2649217 C1, IRE named after V.A. Kotelnikov RAS, 03.30.2018) electroacoustic interdigital transducers (IDT) placed in pairs and forming two sets of acoustic channels for SAW with a wavelength much less than the thickness of the plate, and the PMK family with a wavelength less than or equal to the thickness of the plate. IDTs for excitation of PMC are placed around the periphery around the cylindrical cell, and acoustic channels for surfactants are located outside the cell placement zone. The disadvantage of both devices is the inability to use a more informative phase response of the PMC due to the influence of temperature and the need for a two-stage analysis - first with a reference, then with the analyzed liquid at a strictly fixed temperature.

Turning to the mentioned sources of information, it should be noted that in none of them is it supposed to use a single PMK emitter for sounding both reference and measuring channels, which will sharply increase the reliability of measurements, since it becomes possible to simultaneously compare the analyzed and reference liquids in a single measuring process , and at any temperature of both liquids.

The closest analogue to the patented device is the analyzer described in patent US 9076956 (B2), SAMSUNG ELECTRONICS CO LTD, 07.07.2015. The acoustic analyzer contains a radiating IDT located in the central part of the piezoelectric plate, on both sides of which in the direction of radiation with a gap there are receiving IDTs that form acoustic channels for samples of the analyzed liquid media connected to the measuring path. The analyzer can analyze two independent target substances at the same time, but at the same time one emitting IDT simultaneously voices both channels. However, as indicated in the description of the invention itself, since the generation of surfactants in the forward and reverse directions is carried out along the same path (trajectory), temporary selection of pulses of direct passage and numerous reflections is necessary. This is difficult if there is a strong absorption of surfactants in the measuring channel.

The present invention is directed to solving the problem of implementing an acoustic multichannel analyzer of microprobe liquid media, free from the influence of interference due to the reflected signals.

The patented acoustic analyzer contains a radiating IDT located in the central part of the piezoelectric plate, on both sides of which in the direction of radiation with a gap there are receiving IDTs that form acoustic channels for samples of the analyzed liquid medium connected to the measuring path.

The difference is as follows.

The piezoelectric plate is made of crystalline material with a thickness of the order of the acoustic wavelength with a crystallographic orientation, which ensures the angular dependence of the PMC energy flux on the excitation frequency of the emitting IDT.

Receiving IDTs are arranged in pairs at equal distances relative to the geometric center of the emitting IDT and at angles selected from the conditions for receiving PMK energy flows at discrete excitation frequencies of the emitting IDT, the pins of all receiving IDTs being parallel to the emitting IDT pins.

Acoustic channels for samples contain two cuvettes - one for the analyzed one and the other for reference liquid media - with an open throat of the same size and shape in the form of sectors symmetrical with respect to the plane passing through the geometric center and parallel to the emitting IDT pins, the aforementioned piezoelectric bottom the plate, and the measuring path is configured to register the phase difference and signal amplitudes between the receiving IDTs of each pair.

The analyzer can be characterized in that the plate is made of single-crystal lithium niobate (LNO), has a crystallographic orientation of 128 ° YX + 30 ° -LNO, with a ratio of the thickness H of the plate to the length λ of the acoustic wave N / λ equal to 1.67. The receiving IDTs are arranged in pairs relative to the positive direction of the crystallographic axis X of the single-crystal LNO at five angles: minus 13.1 °, minus 8.9 °, plus 2.7 °, plus 5.2 ° and plus 5.7 °.

The analyzer can also be characterized by the fact that the emitting and receiving IDTs, as well as the cuvettes for liquids with an open neck, are located on one surface of the piezoelectric plate.

The analyzer can also be characterized by the fact that the emitting and receiving IDTs, as well as the cuvettes for liquids with an open neck, are located on different surfaces of the piezoelectric plate.

The analyzer can be characterized, in addition, by the fact that the measuring path includes a high-frequency generator with a scanning frequency, which is capable of controlling and exchanging information, connected to a radiating IDT, switches for pairwise connecting receiving IDTs to receivers, the outputs of which are connected to the first inputs of phase detectors, computer analyzer of fast processes, pulse generator, computing unit, control unit. The outputs of the phase detectors are connected to the signal inputs of a computer analyzer of fast processes, the output of which is connected to the first input of the computing unit, the outputs of the control unit are connected to the switches, the computational unit and the synchronization input of a pulse generator, the outputs of which are connected to the synchronization input of a high frequency generator, an analyzer of fast processes and the computing unit, while the outputs of the high-frequency generator are connected to the second inputs of the phase detectors.

The analyzer can be characterized by the fact that the analyzer of fast processes is a BoxCar integrator.

EFFECT: increased accuracy of analysis of microsamples of liquid media by eliminating the influence of the temperature difference of the analyzed and reference liquid media and reducing the mutual influence of acoustic beams while ensuring noncollinear propagation of their energy flows. An additional technical result is the possibility of fixing both the amplitude and phase responses directly during any measurement.

The invention is based on the provisions established by the applicant himself and confirmed by theoretical data and experimental results.

The main feature is the possibility, unknown from the prior art, of the practical use of the properties of fan-shaped radiation of energy flows of PMC modes of different orders in the measuring channels formed by the same bi-directional radiating IDT. Thanks to this solution, the appearance of re-reflection signals of acoustic waves and, accordingly, interference is eliminated.

The invention is illustrated in the drawings, where:

FIG. 1 is a schematic diagram of an analyzer;

FIG. 2 - one-sided placement of elements on the plate, view in section;

FIG. 3 - double-sided placement of elements on the plate, view in section;

FIG. 4 - channel topology of the analyzer;

FIG. 5 is a schematic representation of the fan-shaped radiation of the PMC energy flows from the excitation frequency of the emitting IDT for a 128 ° YX + 30 ° -LNO plate with a normalized thickness N / λ = 1.67;

FIG. 6 - orientation dependences of the angle of deviation of the energy flux Ψ _n for the PMC of the four first numbers n in the plate 128 ° Y-LNO (Euler angles 0 °, 37.86 °, Θ) with a thickness of N / λ = 1.67.

The acoustic analyzer contains a piezoelectric plate 1, in the central part 11 of which a radiating IDT 2 is located. On both sides of the plate 1, receiving IDTs 3 are placed with a gap in the direction of radiation 21, which form acoustic channels 4 for samples of the analyzed liquid medium. In FIG. Figures 1 and 4 show five channels 4: pos. 41, 42, 43, 44, 45.

The piezoelectric plate 1 is made of monocrystalline lithium niobate (LNO), has a crystallographic orientation of 128 ° YX + 30 ° -LNO, with a ratio of the thickness H of the plate to the length λ of the acoustic wave H / λ = 1.67. Such parameters provide the angular dependence of the PMC energy flux on the excitation frequency of the emitting IDT.

Receiving IDT 3 (31, 32, 33, 34, 35) are arranged in pairs at equal distances relative to the geometric center of the emitting IDT 2 and at angles α ₁ , α ₂ , α ₃ , α ₄ , α ₅ selected from the conditions for receiving PMC energy flows at discrete excitation frequencies of the emitting IDT 2. The readout of the angles α ₁ , α ₂ , α ₃ , α ₄ , α ₅ is made relative to the positive direction of the crystallographic axis X, which is perpendicular to the technological face 5. Pins for receiving IDT 31, 32, 33, 34, 35 are parallel to the pins of the emitting IDT 2.

The distances K at which the receiving IDTs 31, 32, 33, 34, 35 are located in each channel 41, 42, 43, 44, 45 should be the same relative to the geometric center of the emitting IDT 2 for each pair. So in FIG. 4, these distances are designated as K ₁ , K ₅ for channels 41 and 45 with respect to the plane 6 passing through the geometric center and parallel to the pins of the radiating IDT 2.

Acoustic channels for samples contain two cuvettes 51, 52 for the analyzed and reference liquid media with open neck 53 of the same size and shape in the form of sectors symmetrical about a plane 6 passing through the geometric center and parallel to the pins of the radiating IDT 2. The bottom of the cuvette 51, 52 is said piezoelectric plate 1.

Channels 41, 42, 43, 44, 45, in which the receiving IDTs are arranged in pairs relative to the positive direction of the crystallographic axis X of the single-crystal LNO, are located at five angles: α ₁ , α ₂ , α ₃ , α ₄ , α ₅ .

In FIG. 5 schematically shows the directions of the radiation of the energy flows of the indicated PMC modes for the corresponding excitation frequencies of the emitting IDT 2 in the plate 128 ° YX + 30 ° -LNO with a normalized thickness H / λ = 1.67. So, the frequency of 12.4 MHz provides the excitation of the zero order mode (n = 0), 12.7 MHz - the first order (n = 1), 14.2 MHz - the third order (n = 3), 16.2 MHz - the fifth order (n = 5) and 18.5 MHz - seventh order (n = 7).

In FIG. Figure 6 shows the results of our own calculations — the orientation dependences of the angle of deviation of the energy flux Ψ _n for the PMC of the first four mode numbers n in the 128 ° Y-LNO plate (Euler angles 0 °, 37.86 °, Θ) with a thickness of H / λ = 1.67. It can be seen that during propagation, for example, at an angle Θ = 30 ° to the X axis (vertical line), the deviations of the energy flows of modes of different orders of n (horizontal lines) are different, which ensures fan-shaped PMC radiation using a single radiating IDT.

An example embodiment of the measuring path of the analyzer is shown in FIG. 1. It should be noted that various well-known solutions can be used to record the “responses” of acoustoelectronic sensors in pulsed and continuous modes (see, for example, V.I. Anisimkin, I.I. Pyataykin. "Experimental installations for the study of acoustoelectronic sensors in pulsed and continuous modes "// Nonlinear World. 2015. V. 13. No. 4. P. 17-20). The measuring path is not the subject of the present invention.

The measuring path includes a high-frequency generator 7 with a scanning frequency configured to control and exchange information, connected to a radiating IDT 2, switches 8 for pairwise connecting receiving IDTs 3 (pos. 31, 32, 33, 34, 35) to receivers 9, outputs which are connected to the first inputs of the phase detectors 91, 92, a computer analyzer 93 of fast processes, a pulse generator 94, a computing unit 95, a control unit 96. However, several high-frequency generators (according to the number of channels and modes of the PMC) can be used, which are tuned to a specific frequency of each mode.

The outputs of the phase detectors 91, 92 are connected to the signal inputs of a computer analyzer 93 of fast processes. The output of the analyzer 93 is connected to the first input of the computing unit 95. The outputs of the control unit 96 are connected to the switches 8, the computing unit 95 and the synchronization input of the pulse generator 94. The second inputs of the phase detectors 91, 92 are connected to the synchronization outputs of the generator 7.

The outputs of the pulse generator 94 are connected to the synchronization input of a high frequency generator 7, an analyzer 93 of fast processes and a computing unit 95. A computer is used as a means of storing and processing the analysis results.

As an analyzer 93, it is convenient to use the BoxCar integrator, which eliminates the influence of electromagnetic interference on the selection of pulses of different modes. The integrator BoxCar integrator window moves sequentially from the pulse of one PMC to the pulse of another PMC, and does not coincide with the position of the electromagnetic interference, excluding its influence on the measurement results.

The device operates as follows.

Ditches 51, 52 are filled with the analyzed liquids. For example, a reference fluid is introduced into the cuvette 51, and a test fluid is introduced into the cuvette 52. The outputs of the receiving IDT 31-35 through the switches 8 are connected to each other in pairs with the formation of channels 41-45. The output signal is the difference between two signals - one that passed through the liquid of the cell 51, the second - through the liquid of the cell 52. If the liquids in the cells 51, 52 are the same, then the signal at the output of the analyzer 93 is zero. If the acoustic properties differ, then the signal at the output of the analyzer 93 is nonzero, and the measure of this difference is calculated in block 95 as a result of the analysis.

Measurements of the phase "response" in a pulsed mode are carried out, for example, as follows. The rectangular signal from the pulse generator 94 is supplied to the generator 7 of the high frequency. A modulated HF signal with a phase φ _HF = 2πf _о ⋅t enters the emitting IDT 2, which excites the PMC with a frequency f _о . A wave with a velocity v _о propagates through a piezoelectric plate 1 through a liquid in a cuvette 51 and enters a receiving IDT 3 (31), where it is again converted to a modulated RF signal with a phase φ = 2πf _о оt + 2πf _о ⋅ (L / v _о ) . In the phase detector 91, this signal is compared with the reference signal of the high-frequency generator 7, producing a video pulse whose amplitude is proportional to the phase difference of the signals, equal to φ _о = 2πf _о L (L / v _о ). The analyzer 93 (BoxCar integrator) measures the amplitude of the video pulse. The phase response Δφ / φ _о equal to ΔL / L - Δv / v _{о is} measured by an equivalent change in the wave frequency f _о giving the same change in φ _о as the change in speed (Δφ / φ _о = Δf / f _о ) The values of the initial and final frequency of the signal are measured by a frequency meter (not shown in Fig. 1). The accuracy of the “response” measurement is ± 10 × 10 ^-6 .

Measurements of the phase and amplitude "responses" in a continuous mode are carried out using a four-terminal analyzer (for example, KEYSIGHT 5061B), operating, respectively, in phase and amplitude modes for passage.

It should be noted that since the penetration depth of the PMC from the plate 1 into the liquid does not exceed 1 μm, an accurate determination of the mass (volume) of the analyzed liquids is not required. A typical volume of liquid samples is about 100 μl.

Comparison of the parameters of liquids can be carried out at any temperature, since the output signals from the receiving IDT 3 when passing the reference and testing liquids are subtracted.

Metallization of any channel 41-45 in the region of one of the cuvettes 51 or 52 and when subtracting the signals from the receiving IDT 31-35 that passed through the metallized portion in the cuvette 51 and the nonmetallized portion in the cuvette 52 eliminates the contribution from the viscosity of the test liquid and determines contribution only from its electrical conductivity.

When the same liquids, and then biological objects (for example, bacteria) are introduced into cuvette 51 and into cuvette 52, the presence of biological objects and their influence on the properties of the liquid can be detected.

Thus, the achievement of the technical result is achieved - increasing the accuracy of the analysis of microsamples of liquid media by eliminating the influence of the temperature difference of the analyzed and reference liquid media and reducing the mutual influence of the energy flows of acoustic beams.

Claims (11)

1. An acoustic analyzer containing emitting an interdigital transducer (IDT) located in the central part of the piezoelectric plate, on both sides of which in the direction of radiation with a gap there are receiving IDTs that form acoustic channels for samples of the analyzed liquid medium connected to the measuring path, characterized in that the piezoelectric plate is made of a crystalline material with a thickness of the order of the acoustic wavelength with a crystallographic orientation, which provides an angular dependence of the energy flow of acoustic plate-like vibration modes (PMC) on the excitation frequency of the emitting IDT, receiving IDTs are arranged in pairs at equal distances relative to the geometric center of the emitting IDT and at angles selected from the conditions for receiving PMK energy flows at discrete excitation frequencies of the emitting IDT, the pins of all receiving IDTs being parallel to the emitting IDT pins; acoustic channels for samples are formed by two cuvettes for the analyzed and reference liquid media with the same throat of the same size and shape in the form of sectors, the cuvettes are symmetrical about a plane passing through the geometric center and parallel to the pins of the emitting IDT, the bottom of the cuvette being the aforementioned piezoelectric plate, and the measuring path made with the possibility of registering the difference of the signals between the receiving IDT of each pair. 2. The analyzer according to claim 1, characterized in that the plate is made of monocrystalline lithium niobate (LNO), has a crystallographic orientation of 128 ° YX + 30 ° -LNO, with the ratio of the thickness H of the plate to the length λ of the acoustic wave N / λ equal to 1 , 67; receiving IDTs are arranged in pairs relative to the positive direction of the crystallographic axis X of single-crystal LNO at five angles: minus 13.1 °, minus 8.9 °, plus 2.7 °, plus 5.2 ° and plus 5.7 °. 3. The analyzer according to claim 1, characterized in that the emitting and receiving IDTs, as well as the cuvettes for liquids with an open neck, are located on one surface of the piezoelectric plate. 4. The analyzer according to claim 1, characterized in that the emitting and receiving IDTs, as well as the open cell throat cuvettes, are located on different surfaces of the piezoelectric plate. 5. The analyzer according to claim 1, characterized in that the measuring path includes a high-frequency generator with a scanning frequency, capable of controlling and exchanging information, connected to a radiating IDT, switches for pairwise connecting receiving IDTs to receivers, the outputs of which are connected to the first phase inputs detectors, a computer analyzer of fast processes, a pulse generator, a computing unit, a control unit, while the outputs of the phase detectors are connected to the signal inputs of a computer analyzer of fast processes, the output of which is connected to the first input of the computing unit, the outputs of the control unit are connected to the switches, the computing unit and the synchronization input of a pulse generator, the outputs of which are connected to the synchronization input of a high frequency generator, an analyzer of fast processes and the computing unit, while the outputs of the high-frequency generator are connected to the second inputs of the phase detectors. 6. The analyzer according to claim 5, characterized in that the analyzer of fast processes is a BoxCar integrator.

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