A press-fit surface acoustic wave PM2.5 monitor

Abstract

The present invention relates to a press-fit surface acoustic wave PM2.5 monitor, comprising a temperature control unit, a press-fit monitoring probe, a gas collection and flow control unit, and a data acquisition and calculation unit. The present invention is characterized in that the press-fit monitoring probe comprises: an upper shell (1), a sealing ring (4), an upper press-fit structure (13), a sealing gasket (14), an upper microfluidic channel layer (5), a lower microfluidic channel layer (12), a lower press-fit structure (23), a lower shell (18), a refrigerator (20), and a radiator (21). The present invention has the advantages that the surface acoustic wave chip can be easily replaced, the monitoring probe can be reused, the airtightness is high, and the integrity is strong.

Description

Technical Field

[0001] The present invention relates to the field of air pollutant monitoring, and in particular to a press-fit surface acoustic wave PM2.5 monitor. Background Art

[0002] PM2.5 has become a hot topic over the past decade. PM2.5 is a complex air pollutant composed of multiple components, which can be emitted from both natural and human sources. Currently, the main PM2.5 monitoring methods used internationally include gravimetric methods, micro-oscillating balance methods, beta-ray methods, and light scattering methods.

[0003] The gravimetric method is the most basic measurement method and is also a method that provides a reference standard for automatic monitoring data. my country currently mainly uses the gravimetric method to monitor PM2.5. Although the gravimetric method has a high monitoring accuracy, it is a manual method that takes a long time and is therefore not suitable for automatic monitoring networks. The micro-oscillating balance method is a fast and accurate measurement method that can automatically perform temperature and pressure compensation and provide high-precision measurements. However, it requires a lot of maintenance and is easily affected by air humidity, so it is often necessary to install a dynamic measurement system to monitor the filter membrane to correct errors. The β-ray method is based on the effect of particulate matter on the 14 The light scattering method uses the absorption intensity of C-emission radiation to analyze the PM2.5 concentration. This method is simple to operate and requires minimal maintenance, but its measurement accuracy is relatively low. The light scattering method is based on the Mie scattering theory of particles. This method has poor accuracy in detecting PM2.5 and often requires additional auxiliary methods to compensate for errors.

[0004] Because surface acoustic wave sensors have the characteristics of small size, simple process and high sensitivity, they match the trend of PM2.5 monitors towards miniaturization and integration. Patent 201610463140.1 discloses a PM2.5 detector based on surface acoustic waves, which includes an upper shell, a lower shell, a virtual impactor, a surface acoustic wave detector, a heating source, a left airflow channel, a middle airflow channel and a right airflow channel. When the airflow flows into the PM2.5 monitor, the airflow containing PM2.5 particles is separated from the airflow by the virtual impactor. The airflow containing PM2.5 particles flows into the middle airflow channel, and the remaining airflow flows out from the left and right airflow channels. The PM2.5 particles are deposited on the surface acoustic wave monitor through the thermophoresis field generated by the heating source. The surface acoustic wave detector detects the change in the propagation velocity of the surface acoustic wave generated along the surface after it captures the particles to obtain the change in the operating frequency of the surface acoustic wave detector, and then calculates the mass concentration of PM2.5 in the air.

[0005] However, existing surface acoustic wave PM2.5 monitors based on the thermophoretic deposition method have problems such as poor airtightness and integrity, and the inability to replace the surface acoustic wave chip. At the same time, the combination of microfluidic channels often introduces impurities such as colloidal particles to contaminate the surface acoustic wave chip, resulting in certain errors in the monitoring results. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems existing in the current surface acoustic wave PM2.5 monitor using the thermophoretic deposition method, such as the inability to replace the surface acoustic wave chip, poor air tightness of the monitoring probe, and easy introduction of foreign particles to interfere with the monitoring results. The present invention thus provides a press-fit surface acoustic wave PM2.5 monitor, which enables the surface acoustic wave chip to be easily replaced while protecting the integrity of other key components inside the probe. The monitoring probe has the advantages of being reusable, highly airtight, and highly integrated, and the combination method of the monitoring probe avoids the introduction of other foreign particles, thereby preventing interference with the monitoring results.

[0007] To achieve the above-mentioned purpose, the present invention provides a press-fit surface acoustic wave PM2.5 monitor, wherein the press-fit monitoring probe comprises, from top to bottom, an upper shell (1), a sealing ring (4), an upper layer of a microfluidic channel (5), a lower layer of a microfluidic channel (12), an upper press-fit structure (13), a sealing gasket (14), a lower press-fit structure (23), and a lower shell (18);

[0008] An air inlet channel interface (2) and an air outlet channel interface (3) are respectively provided on the upper shell (1), and a sealing ring placement groove is provided inside the upper shell (1) at positions corresponding to the air inlet channel interface (2) and the air outlet channel interface (3), and the sealing ring (4) is placed in the sealing groove;

[0009] The upper layer (5) of the microfluidic channel is provided with an air inlet (6) and an air outlet (7), which correspond to the air inlet channel interface (2) and the air outlet channel interface (3); a micro heat source (8) is made on the lower surface of the upper layer (5) of the microfluidic channel;

[0010] The microfluidic channel lower layer (12) is located below the microfluidic channel upper layer (5), and a virtual impactor (9) and a microfluidic channel (10) are made on the upper surface, and a surface acoustic wave chip placement window (11) and a micro heat source lead placement groove (22) are opened; the microfluidic channel lower layer (12) forms a microfluidic channel assembly with the microfluidic channel upper layer (5) through bonding technology, and the micro heat source (8) lead is embedded in the micro heat source lead placement groove (22);

[0011] The upper pressing structure (13) is provided with an embedding groove of the microfluidic channel assembly in the middle, fixed to the microfluidic channel assembly by gluing, and connected to the micro heat source (8) by a lead wire, and a radio frequency connection window (24) is also provided on the outside;

[0012] The lower pressing structure (23) is provided with a surface acoustic wave chip placement groove (16) at a position corresponding to below the surface acoustic wave chip placement window (11); the surface acoustic wave chip (15) is placed above the surface acoustic wave chip placement groove (16) and embedded in the surface acoustic wave chip placement window (11); and a sealing gasket placement groove (25) is provided at a position corresponding to below the microfluidic channel lower layer (12); the sealing gasket (14) is placed in the sealing gasket placement groove (25); surface acoustic wave chip connection ports (26) are provided on both sides of the surface acoustic wave chip placement groove (16); and the lower pressing structure (23) is provided with a radio frequency connection port (17) at a position corresponding to the radio frequency connection window (24);

[0013] The lower shell (18) is fixed to the upper shell (1).

[0014] As a further improvement of the above solution, the microfluidic channel upper layer (5) in the microfluidic channel assembly extends with an outer edge that is larger than the microfluidic channel lower layer (12), and the microfluidic channel lower layer (12) is embedded in the embedding groove of the upper press-fit structure (13) and is fixed to the upper press-fit structure (13) through the outer edge of the microfluidic channel upper layer (5).

[0015] As a further improvement of the above solution, the sealing gasket placement groove (25) is arranged on the periphery of the area of ​​the virtual impactor (9), wherein each side of the microfluidic channel lower layer (12) maintains a suitable distance from the corresponding outer edge of the virtual impactor (9), and the increased area can prevent the microfluidic channel assembly from being deformed or broken due to the small contact area between the sealing gasket (14) and the microfluidic channel lower layer (12).

[0016] As a further improvement to the above solution, the surface acoustic wave chip utilizes a resonator structure or a delay line structure. The resonator structure can be either a single-ended or double-ended resonator, containing a single or multiple transducers and a reflector grating; the delay line structure consists of an input transducer and an output transducer. Particles in the main airflow are deposited on sensitive areas of the surface of the surface acoustic wave chip under the action of thermophoretic forces, disrupting the propagation of the surface acoustic waves on the piezoelectric substrate, causing a change in the speed of sound and, in turn, a change in the frequency of the surface acoustic wave chip, enabling particle mass detection.

[0017] As a further improvement of the above solution, the microfluidic channel upper layer (5) forms a microfluidic channel assembly with the microfluidic channel lower layer (12) through a silicon-silicon bonding method.

[0018] As a further improvement of the above solution, the surface acoustic wave chip placement window (11) is located in the microfluidic channel (10) and is used to accommodate the surface acoustic wave chip (15) and the surface acoustic wave chip connection port (26), and is used to prevent the surface acoustic wave chip leads from touching the microfluidic channel after pressing; the micro heat source lead placement groove (22) coincides with the surface acoustic wave chip placement window (11) and has the same width as the micro heat source (8).

[0019] As a further improvement of the above solution, the lower housing (18) is provided with a refrigerator installation window (19) at a corresponding position below the surface acoustic wave chip placement groove (16), and the refrigerator (20) is embedded in the refrigerator installation window (19) and fixed on the upper surface of the radiator (21).

[0020] As a further improvement of the above solution, the microchannel upper layer (5) and the microchannel lower layer (12) are made of non-metallic materials; the micro heat source (8) is made of metallic materials; the upper shell (1) and the lower shell (18) are made of high-temperature resistant materials with good mechanical strength; and the sealing ring (4) and the sealing gasket (14) are made of high-temperature resistant elastic materials.

[0021] As a further improvement of the above scheme, the micro heat source (8) is manufactured using MEMS micromachining technology and includes a heating film resistor, a temperature measuring film resistor and a contact electrode; wherein the heating film resistor serves as a heat source for the microfluidic channel (10), the temperature measuring film feeds back the heat source temperature through the resistance value, and the contact electrode is connected to the heating film resistor and the temperature measuring film resistor to provide input current and measure the resistance value of the temperature measuring film resistor.

[0022] As a further improvement of the above solution, the lower surface of the glue-coated area of ​​the upper layer (5) of the microfluidic channel is fixed to the upper pressing structure (13) by applying glue or snaps, screws, etc.

[0023] As a further improvement of the above solution, the depth of the surface acoustic wave chip placement groove (16) is set to ensure that after the surface acoustic wave chip (15) is attached, the sensitive area of ​​the surface acoustic wave chip (15) is flush with the bottom of the microfluidic channel assembly.

[0024] As a further improvement of the above technical solution, the size design of the virtual impactor includes the nozzle aperture, the ratio of nozzle length to aperture, the closing distance to nozzle aperture ratio, the airflow collection and flow control unit extracts air at a fixed flow rate, the airflow Reynolds number is between 500 and 3000, and it is verified through simulation software that when the particle size is 2.5μm, the cutting efficiency meets 50%.

[0025] As a further improvement to the above technical solution, the SAW chip in the press-fit monitoring probe can accumulate excessive particles in the sensitive area after long-term use, ultimately affecting monitoring effectiveness. In this press-fit monitoring probe, the SAW chip is separated from the virtual impactor and microfluidic channel. The lower press-fit structure can be removed and replaced by removing screws or snaps, allowing the SAW chip to be replaced while maintaining the airtightness of the monitoring probe and protecting the integrity of the microfluidic channel and microheat source.

[0026] Compared with the existing technology, the beneficial effects of the present invention are: the surface acoustic wave PM2.5 monitor with a replaceable sensitive chip of the present invention integrates particle screening, particle attachment, and particle measurement, so that the surface acoustic wave chip can be easily replaced while protecting the integrity of other key components inside the probe. The monitoring probe has the advantages of reusability, high airtightness, and strong integrity, and the combination method of the monitoring probe avoids the introduction of other impurity particles, preventing interference with the monitoring results. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A structural diagram of a press-fit probe for a press-fit surface acoustic wave PM2.5 monitor provided in an embodiment of the present invention;

[0028] Figure 2 A bottom view of the upper layer of a microfluidic channel of a press-fit probe of a press-fit surface acoustic wave PM2.5 monitor provided in an embodiment of the present invention;

[0029] Figure 3 This is a structural block diagram of a press-fit surface acoustic wave PM2.5 monitor provided in an embodiment of the present invention;

[0030] Figure 4 This is a basic flow chart of a method based on a press-fit surface acoustic wave PM2.5 monitor provided in an embodiment of the present invention.

[0031] Reference numerals

[0032] 1. Upper shell 2. Air inlet channel interface 3. Air outlet channel interface

[0033] 4. Sealing ring 5. Microfluidic channel upper layer 6. Air inlet

[0034] 7. Air outlet 8. Micro heat source 9. Virtual impactor

[0035] 10. Microfluidic channel 11. Surface acoustic wave chip placement window

[0036] 12. Microfluidic channel lower layer 13. Upper pressing structure 14. Sealing gasket

[0037] 15. Surface acoustic wave chip 16. Surface acoustic wave chip placement groove

[0038] 17. RF connection port 18. Lower housing 19. Refrigerator installation window

[0039] 20. Refrigerator 21. Radiator 22. Micro heat source lead placement slot

[0040] 23. Lower pressing structure 24. RF connection window 25. Sealing gasket placement groove

[0041] 26. Surface acoustic wave chip connection port DETAILED DESCRIPTION

[0042] The following describes in detail a press-fit surface acoustic wave PM2.5 monitor according to the present invention in conjunction with the accompanying drawings and embodiments.

[0043] The present invention provides a press-fit surface acoustic wave PM2.5 monitor, comprising a temperature control unit, a press-fit monitoring probe, a gas collection and flow control unit, and a data collection and calculation unit, wherein the press-fit monitoring probe comprises: an upper shell (1), a sealing ring (4), an upper press-fit structure (13), a sealing gasket (14), a lower press-fit structure (23), and a lower shell (18). The press-fit monitoring probe based on the above structure has the following working principle: an airflow conduit is connected to an air inlet channel interface, sampling gas containing aerosol particles enters the virtual impactor inlet through the conduit, particles of different particle sizes are screened by the virtual impactor, and aerosol particles with a particle size of less than 2.5 μm enter the micro-flow channel along with the mainstream airflow.

[0044] The virtual impactor adjustment parameter design includes: nozzle width, closing width, nozzle length, nozzle and closing distance, closing top fillet, nozzle and closing coaxiality, so that the cutting particle size D of the virtual impactor is 50 The collection efficiency curve is located at D 50 The sampled airflow is accelerated at the inlet of the virtual impactor and separated at the constriction into a primary airflow containing particles with a size of 2.5±0.2μm or less and a secondary airflow containing particles with a size of 2.5±0.2μm or more.

[0045] The upper layer (5) of the microfluidic channel in the microfluidic channel assembly extends with an outer edge larger than the lower layer (12) of the microfluidic channel. The lower layer (12) of the microfluidic channel is embedded in the embedding groove of the upper pressing structure (13) and is fixed to the upper pressing structure (13) by gluing the outer edge of the upper layer (5) of the microfluidic channel. The surface acoustic wave chip has various structures and can be mainly divided into resonator type and delay line type. This embodiment takes the resonator type surface acoustic wave chip as an example, and prepares a transducer and a reflection grating on the surface of the piezoelectric substrate. When an electrical signal is applied to the input transducer, the electrical signal is converted into mechanical energy through the inverse piezoelectric effect, propagates along the surface of the piezoelectric substrate within a depth range of 1 to 2 wavelengths in the form of a surface acoustic wave, and forms a standing wave resonant cavity together with the reflection grating, and then is converted into an electrical signal output through the piezoelectric effect. Particles in the main airflow of the virtual impactor are deposited on the sensitive area of ​​the surface of the surface acoustic wave chip under the action of thermophoretic force, interfering with the propagation of the surface acoustic wave on the piezoelectric substrate, causing the sound speed to change, and thus causing the frequency of the surface acoustic wave chip to change. The data acquisition and calculation unit collects and calculates the change in the chip's operating frequency to realize the detection of particle quality.

[0046] In this embodiment, the dimensions of the upper and lower press-fit structures are approximately 40 mm x 50 mm. The microfluidic channel of the upper press-fit structure has a window, allowing the lower layer of the microfluidic channel to be embedded. The depth of the SAW chip placement groove and the thickness of the sealing gasket in the lower press-fit structure are appropriately designed based on the selected SAW chip size, ensuring that the SAW chip surface and the microchannel are aligned horizontally. The depth of the sealing gasket placement groove in the lower press-fit structure is appropriately designed to ensure the probe's airtightness after the sealing gasket is inserted and pressed together.

[0047] In this embodiment, the upper layer (5) of the microfluidic channel is made of quartz material; the micro heat source (8) is made of metal film material; the lower layer (12) of the microfluidic channel is made of silicon wafer material; the upper shell (1) and the lower shell (18) are made of polytetrafluoroethylene material to fully protect the internal structure; the sealing ring (4) and the sealing gasket (14) are made of silicone rubber material.

[0048] In this embodiment, the upper shell (1) and the lower shell (18) are provided with screw holes and are fixed by screws after assembly. When the surface acoustic wave chip needs to be replaced, the fixing screws are unscrewed and the lower press-fit structure (23) on which the surface acoustic wave chip is placed is taken out for replacement. This achieves replacement of the surface acoustic wave chip while ensuring the airtightness of the monitoring probe and protecting the integrity of the microfluidic channel and the micro heat source.

[0049] Figure 3A block diagram of the structure of a press-fit surface acoustic wave (SAW) PM2.5 monitor provided in an embodiment of the present invention is shown. The gas collection and flow control unit, located at the end of the monitor's airflow channel, consists of a logic control module, an electromagnetic control valve, a flow sensor, a calibration circuit, and a collection air pump. It dynamically controls and regulates the monitor's sampled airflow. The gas collection and flow control unit inputs the desired sampled airflow rate into the logic control module. This module controls the supply voltage of the collection air pump based on the desired flow rate, adjusting the pump to generate an appropriate negative pressure to meet the collection flow rate. The collection air pump generates negative pressure at the end of the monitor's airway and collects sampled air through the airway inlet. The flow sensor measures the gas mass flow rate using capillary heat transfer temperature differential calorimetry and feeds a voltage signal back to the calibration circuit. The calibration circuit adjusts the opening degree of the electromagnetic control valve based on the difference between the feedback voltage signal and the set voltage. The temperature control unit generates a stable temperature gradient field according to set parameters. The data acquisition and calculation unit reads the frequency signal from the SAW chip as the initial frequency f0 and calculates the corresponding mass as the zero mass value m0. After the sampled gas enters the press-fit monitoring probe from the sampling inlet, a virtual impactor is used to filter particles. The PM2.5 carrier gas flows into the mainstream channel toward the temperature gradient field generated by the microheater and cooler, while the remaining gas flows into the secondary channel for large-particles and flows toward the sampling outlet. A temperature control unit dynamically adjusts the microheat source to generate a stable temperature gradient field. The PM2.5 particles are deposited in the sensitive area of ​​the surface acoustic wave chip under the action of thermophoretic forces, resulting in a corresponding frequency shift. The carrier gas flows out of the press-fit monitoring probe with the mainstream gas flow toward the sampling outlet. The data acquisition and calculation unit collects the frequency shift signal based on the set sampling time period T and calculates Δf. The data acquisition and calculation unit also calculates the corresponding particle mass change Δm within this period T. The mass concentration of the sampled gas is calculated based on the set sampling gas flow parameters and the frequency shift feedback from the surface acoustic wave chip.

[0050] Figure 4 A basic flow chart of a monitoring method based on a press-fit surface acoustic wave PM2.5 monitor provided in an embodiment of the present invention is shown. The method includes the following steps:

[0051] Step 1: Set the sampling period T of the data acquisition and calculation unit and the flow parameter L of the gas acquisition and flow control unit;

[0052] Step 2: Control the micro heat source and the refrigerator to generate a temperature gradient field through the temperature control unit;

[0053] Step 3: Start sampling, the data acquisition unit reads the SAW chip frequency f0,

[0054] Step 4: The data acquisition and calculation unit calculates and stores the initial mass m0 as the mass zero value;

[0055] Step 5: The PM2.5 particles flow through the temperature gradient field and are deposited on the sensitive area of ​​the SAW chip under the action of thermophoretic force, resulting in frequency shift.

[0056] Step 6: The data acquisition and calculation unit reads the frequency change Δf caused by the particles deposited on the surface of the surface acoustic wave chip according to the set period T, and calculates the corresponding particle mass change Δm within the period T;

[0057] Step 7: The data acquisition and calculation unit calculates the volume V of the sampled gas flowing through the press-fit monitoring probe within the period T according to the set flow parameter L, and obtains the PM2.5 mass concentration C in the sampled gas within the period T. T =Δm / V.

[0058] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention and are intended to be encompassed by the claims of the present invention.

Claims

1. A press-fit surface acoustic wave PM2.5 monitor, comprising a temperature control unit, a press-fit monitoring probe, a gas collection and flow control unit, and a data acquisition and calculation unit, characterized in that: The press-fit monitoring probe comprises, from top to bottom, an upper shell (1), a sealing ring (4), an upper layer of a microfluidic channel (5), a lower layer of a microfluidic channel (12), an upper press-fit structure (13), a sealing gasket (14), a lower press-fit structure (23), and a lower shell (18); An air inlet channel interface (2) and an air outlet channel interface (3) are respectively provided on the upper shell (1), and a sealing ring placement groove is provided inside the upper shell (1) at positions corresponding to the air inlet channel interface (2) and the air outlet channel interface (3), and the sealing ring (4) is placed in the sealing groove; The upper layer (5) of the microfluidic channel is provided with an air inlet (6) and an air outlet (7), which correspond to the air inlet channel interface (2) and the air outlet channel interface (3); a micro heat source (8) is made on the lower surface of the upper layer (5) of the microfluidic channel; The microfluidic channel lower layer (12) is located below the microfluidic channel upper layer (5), and a virtual impactor (9) and a microfluidic channel (10) are made on the upper surface, and a surface acoustic wave chip placement window (11) and a micro heat source lead placement groove (22) are opened; the microfluidic channel lower layer (12) forms a microfluidic channel assembly with the microfluidic channel upper layer (5) through bonding technology, and the micro heat source (8) is embedded in the micro heat source lead placement groove (22); The upper pressing structure (13) is provided with an embedding groove of the microfluidic channel assembly in the middle, fixed to the microfluidic channel assembly by gluing, and connected to the micro heat source (8) by a lead wire, and a radio frequency connection window (24) is also provided on the outside; The lower pressing structure (23) is provided with a surface acoustic wave chip placement groove (16) at a position corresponding to below the surface acoustic wave chip placement window (11); the surface acoustic wave chip (15) is placed above the surface acoustic wave chip placement groove (16) and embedded in the surface acoustic wave chip placement window (11); and a sealing gasket placement groove (25) is provided at a position corresponding to below the microfluidic channel lower layer (12); the sealing gasket (14) is placed in the sealing gasket placement groove (25); surface acoustic wave chip connection ports (26) are provided on both sides of the surface acoustic wave chip placement groove (16); and the lower pressing structure (23) is provided with a radio frequency connection port (17) at a position corresponding to the radio frequency connection window (24); The lower shell (18) is fixed to the upper shell (1).

2. The press-fit surface acoustic wave PM2.5 monitor according to claim 1, characterized in that: The microfluidic channel upper layer (5) forms a microfluidic channel assembly with the microfluidic channel lower layer (12) through a silicon-silicon bonding method.

3. The press-fit surface acoustic wave PM2.5 monitor according to claim 1, characterized in that: The microfluidic channel upper layer (5) in the microfluidic channel assembly extends to have an outer edge that is larger than the microfluidic channel lower layer (12); the microfluidic channel lower layer (12) is embedded in the embedding groove of the upper press-fit structure (13) and is fixed to the upper press-fit structure (13) through the outer edge of the microfluidic channel upper layer (5).

4. The press-fit surface acoustic wave PM2.5 monitor according to claim 1, characterized in that: The sealing pad placement groove is arranged on the periphery of the area of ​​the virtual impactor (9).

5. The press-fit surface acoustic wave PM2.5 monitor according to claim 1, characterized in that: The surface acoustic wave chip (15) uses a resonator structure or a delay line structure, wherein: the resonator structure is divided into a single-end resonator or a double-end resonator, and is composed of a piezoelectric substrate and a single or multiple transducers and reflectors arranged on the surface of the piezoelectric substrate; the delay line structure is composed of a piezoelectric substrate and an input transducer and an output transducer arranged on the surface of the piezoelectric substrate.

6. The press-fit surface acoustic wave PM2.5 monitor according to claim 1, characterized in that: The surface acoustic wave chip placement window (11) is located in the microfluidic channel (10) and is used to accommodate the surface acoustic wave chip (15) and the surface acoustic wave chip connection port (26); the micro heat source lead placement groove (22) overlaps with the surface acoustic wave chip placement window (11) and is wider than the lead of the micro heat source (8).

7. The press-fit surface acoustic wave PM2.5 monitor according to claim 1, characterized in that: The lower housing (18) is provided with a refrigerator installation window (19) at a corresponding position below the surface acoustic wave chip placement groove (16); the refrigerator (20) is embedded in the refrigerator installation window (19) and fixed on the upper surface of the radiator (21).

8. The press-fit surface acoustic wave PM2.5 monitor according to claim 1, characterized in that: The microchannel upper layer (5) and the microchannel lower layer (12) are made of non-metallic materials, the micro heat source (8) is made of metallic materials, the upper shell (1) and the lower shell (18) are made of high-temperature resistant materials with good mechanical strength; and the sealing ring (4) and the sealing gasket (14) are made of high-temperature resistant elastic materials.

9. The press-fit surface acoustic wave PM2.5 monitor according to claim 1, characterized in that: The micro heat source (8) is manufactured using a MEMS micro-manufacturing process and comprises a heating film resistor, a temperature measuring film resistor and a contact electrode; wherein the heating film resistor serves as a heat source for the microfluidic channel (10), the temperature measuring film feeds back the heat source temperature through the resistance value, and the contact electrode is connected to the heating film resistor and the temperature measuring film resistor.

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