Microfluidic mass flowmeter and measurement and control method

Abstract

The invention provides a micro-fluidic mass flowmeter and a measurement and control method, the micro-fluidic mass flowmeter comprises a micro-fluidic chip body, a fluid channel is arranged in the chip body, and a degassing chamber, an expansion chamber and at least one section of measurement flow channel are sequentially arranged between the inlet end and the outlet end of the fluid channel; through the design of the highly-integrated micro-fluidic chip, the thermal sensing unit, the pressure difference sensing unit and the vibration sensing unit cooperate with the multi-U-shaped channel structure with the gradually-decreased curvature radius, and wide-range and high-precision mass flow measurement is achieved; a self-adaptive weighted data fusion algorithm is adopted, high sensitivity of thermal measurement in a low-flow area and stability of differential pressure measurement in a high-flow area are fused, so that the inherent limitation of a single-principle flowmeter is overcome, meanwhile, the system solves the fluid density in real time through a vibration sensing unit, accurate dynamic compensation is provided for a differential pressure method, and the fluid density measurement accuracy is improved. And functions are expanded to comprehensive analysis of multiple parameters such as fluid density, viscosity and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a microfluidic mass flow meter and a measurement and control method, and belongs to the technical field of flow measurement. BACKGROUND

[0002] As a core device in the field of precise fluid measurement and control, the microfluidic mass flow meter has wide application requirements in high-tech fields such as biopharmaceuticals, chemical analysis, semiconductor cooling and fuel cells. At present, microfluidic flow meters based on different measurement principles have been proposed, for example, the thermal mass flow meter has high sensitivity and accuracy in the low flow range, but its measurement principle determines that the signal is saturated at high flow due to the short contact time of the fluid with the heater, and the measurement accuracy decreases significantly.

[0003] On the contrary, the flow meter based on the pressure difference principle has good performance at high flow, but its measurement result is seriously dependent on the density of the fluid, and the fluid density is easily affected by temperature, pressure and composition changes. At low flow, the pressure difference signal is weak, the signal-to-noise ratio is low, and complex density compensation is needed to obtain the mass flow, and the error is large in the application scene where the fluid properties change greatly; and the existing flow meter has single function, usually only flow parameters can be provided. However, in many precise process, the density, viscosity and other physical parameters of the fluid are also crucial. At present, to realize the synchronous measurement of these multiple parameters, multiple function-independent sensors are often connected in series in the flow path, which not only increases the complexity and volume of the system, but also introduces additional flow resistance and dead volume, which destroys the advantages of microfluidic system integration; and the sensor will inevitably drift or fail after long-term use, and in critical applications such as bioreactors that require long-term continuous operation, it is impossible to realize real-time sensing of its own health status, which will bring safety risks; therefore, a microfluidic mass flow meter and a measurement and control method are proposed. SUMMARY

[0004] Therefore, the present application provides a microfluidic mass flow meter and a measurement and control method to solve or alleviate the technical problems in the prior art, at least to provide a beneficial choice.

[0005] The technical solution of the present application is as follows: a microfluidic mass flow meter, comprising a microfluidic chip body, a fluid channel is arranged in the chip body, and a gas removal chamber, an expansion chamber and at least one measuring flow channel are sequentially arranged between the inlet end and the outlet end of the fluid channel. The at least one measuring flow channel comprises a first U-shaped channel, a second U-shaped channel and a third U-shaped channel connected in sequence. The fluid channel is also integrated with a thermal sensing unit, including a first temperature sensor and a second temperature sensor arranged at the straight section of the first U-shaped channel inlet, a micro-heater arranged at the end of the straight section of the first U-shaped channel inlet, and a third temperature sensor arranged at the straight section of the first U-shaped channel outlet. A differential pressure sensing unit, including a first pressure sensor arranged at the inlet of the second U-shaped channel and a second pressure sensor arranged at the outlet of the second U-shaped channel. A vibration sensing unit, including a first vibration sensor arranged at the outside of the U-shaped bend of the second U-shaped channel and a second vibration sensor arranged at the outside of the U-shaped bend of the third U-shaped channel. A signal processing unit electrically connected with the thermal sensing unit, the differential pressure sensing unit, and the vibration sensing unit, configured to receive signals of each sensor and calculate the mass flow of the fluid through a data fusion algorithm.

[0006] Further preferably, a reference pressure sensor is arranged in the expansion chamber to measure the absolute pressure of the fluid and provide a pressure reference for the differential pressure sensing unit.

[0007] Further preferably, the curvature radii of the first U-shaped channel, the second U-shaped channel, and the third U-shaped channel decrease in turn.

[0008] Further preferably, the first temperature sensor and the second temperature sensor are arranged in an asymmetric layout; the distance between the second temperature sensor and the micro-heater is smaller than the distance between the first temperature sensor and the second temperature sensor.

[0009] Further preferably, a hydrophobic microporous membrane structure is arranged in the degassing chamber, one side of the hydrophobic microporous membrane being in contact with the fluid channel and the other side being in communication with the exhaust channel.

[0010] In addition, the present application also provides a microfluidic mass flow meter measurement and control method, Step one, system initialization, drive the fluid to flow through the fluid channel, and simultaneously start the thermal sensing unit, the differential pressure sensing unit, and the vibration sensing unit; Step two, synchronously collect signals of each sensor, including temperature signals measured by the first temperature sensor and the second temperature sensor, a power signal of the micro-heater, a temperature signal measured by the third temperature sensor, differential pressure signals measured by the first pressure sensor and the second pressure sensor, and vibration frequency signals measured by the first vibration sensor and the second vibration sensor. Step three, transmit all the collected signals to the signal processing unit for parallel processing; wherein, based on the power of the micro-heater and the signals of the first, second and third temperature sensors, the first mass flow rate estimate of the fluid is calculated according to the thermal measurement principle; Based on the differential pressure signal of the first and second pressure sensors, combined with the flow resistance characteristics of the second U-shaped channel, the uncompensated instantaneous flow rate value is calculated; At the same time, based on the vibration frequency signals of the first and second vibration sensors, the real-time density value of the fluid is solved; Step four, using the real-time density value solved in step three, the uncompensated instantaneous flow rate value is dynamically density-compensated and corrected to obtain the second mass flow rate estimate; Step five, using an adaptive weighted data fusion algorithm, the first mass flow rate estimate and the second mass flow rate estimate are data fused; wherein, in the low flow range, the first mass flow rate estimate is preferentially adopted, and in the high flow range, the second mass flow rate estimate is preferentially adopted, and finally a full-range high-precision mass flow rate value is output.

[0011] Further preferably, the adaptive weighted data fusion algorithm in step five determines the weight coefficient specifically including the following steps, Step 5.1: calculate the signal-to-noise ratio of the thermal sensing unit output signal at the current flow rate, and the intensity of the differential pressure sensing unit output signal; Step 5.2: according to the preset mapping relationship, a higher fusion weight is allocated to the sensing unit with high signal-to-noise ratio, and a higher fusion weight is allocated to the sensing unit with high signal intensity; Step 5.3: according to the weight determined in step 5.2, the two mass flow rate estimates are weighted and averaged to obtain the final mass flow rate value.

[0012] Further preferably, it further includes a self-diagnosis process, which is executed when the device is powered on or at a preset period, and the specific steps are, Step A: in the static state of the fluid, a short-time heat pulse is applied to the micro-heater; Step B: the weak vibration signal generated by the thermal expansion and contraction of the fluid caused by the heat pulse is detected by the first and second vibration sensors; Step C: analyze the response amplitude and waveform of the vibration signal, if the response is within the expected range, it is determined that the vibration sensing unit is working normally and the zero point calibration is completed; if the response is abnormal or missing, a sensor fault alarm is triggered.

[0013] Further preferably, it further includes a fluid property comprehensive analysis step, specifically, Step X: reading the absolute pressure value of the fluid measured by the reference pressure sensor arranged in the expansion chamber; Step Y: combining the absolute pressure value with the real-time density value calculated by the vibration sensing unit in step three, and further calculating the dynamic viscosity or kinematic viscosity parameter of the fluid through the built-in fluid property model; Step Z: outputting the final mass flow value, density value, absolute pressure value and viscosity parameter as a comprehensive parameter set describing the current fluid state.

[0014] The embodiment of the present application has the following advantages due to the adoption of the above technical solutions: The present application realizes wide-range and high-precision mass flow measurement by highly integrated microfluidic chip design, in which the thermal, pressure difference and vibration sensing units work cooperatively with the multi-U-shaped channel structure with decreasing curvature radius; and adopts self-adaptive weighted data fusion algorithm to fuse the high sensitivity of thermal measurement in the low flow area and the stability of pressure difference measurement in the high flow area, thereby overcoming the inherent limitations of single principle flowmeter, and at the same time, the system calculates the fluid density in real time through the vibration sensing unit, not only providing accurate dynamic compensation for the pressure difference method, but also expanding the function to comprehensive analysis of multiple parameters such as fluid density and viscosity.

[0015] The above summary is only for the purpose of the description and is not intended to limit in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features will be readily apparent to those skilled in the art by reference to the drawings and the following detailed description. BRIEF DESCRIPTION OF DRAWINGS In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, brief introductions to the drawings needed in the embodiments or prior art descriptions will be given below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0016] Figure 1 The structural diagram of the present application.

[0017] Among them: 1-microfluidic chip body; 10-inlet end; 11-deaeration chamber; 12-expansion chamber; 13-outlet end; 20-first temperature sensor; 21-second temperature sensor; 22-third temperature sensor; 23-micro-heater; 30-reference pressure sensor; 31-first pressure sensor; 32-second pressure sensor; 40-first vibration sensor; 41-second vibration sensor; 50-first U-shaped channel; 51-second U-shaped channel; 52-third U-shaped channel. DETAILED DESCRIPTION In order to make the objects, technical solutions and advantages of the present application clearer, the following further describes the present application with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the scope of the present application. In addition, in the following description, the description of well-known structures and techniques is omitted to avoid unnecessary confusion of the concept of the present application.

[0018] In the description of the present application, it should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0019] In the description of the present application, it should be noted that the terms "center", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the present application is normally placed, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third", and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited. The meaning of "several" is one or more, unless otherwise explicitly specified and limited.

[0020] In the description of the present application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "disposed", "mounted", "connected", "linked" should be broadly understood, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be mechanically connected, can be electrically connected; can be directly connected, can be indirectly connected through an intermediate medium, can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0021] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0022] As Figure 1 shown, the embodiment of the present application provides a microfluidic mass flowmeter, comprising a microfluidic chip body 1, In one embodiment, a fluid channel is arranged in the chip body 1, and a degassing chamber 11, an expansion chamber 12 and at least one measuring flow passage are sequentially arranged between an inlet end 10 and an outlet end 13 of the fluid channel; The at least one measuring flow passage comprises a first U-shaped passage 50, a second U-shaped passage 51 and a third U-shaped passage 52 which are sequentially communicated; In this embodiment, a staged measurement system is formed by changing the layout of the flow passage, the degassing chamber 11 can effectively remove the bubbles in the fluid through its internal structure, avoiding the interference of the bubbles on the subsequent measurement; the expansion chamber 12 makes the fluid flow rate tend to be stable, creating good conditions for accurate measurement; and the three-stage U-shaped passages 50, 51 and 52 optimize the measurement environment of different sensors through their special curved structures. This staged and multi-form flow passage design ensures that each sensor can work in the best fluid state, thereby improving the accuracy and reliability of the overall measurement.

[0023] In one embodiment, a thermal sensing unit is further integrated on the fluid channel, comprising a first temperature sensor 20 and a second temperature sensor 21 arranged at the inlet straight section of the first U-shaped passage 50, a micro-heater 23 arranged at the end of the inlet straight section of the first U-shaped passage 50, and a third temperature sensor 22 arranged at the outlet straight section of the first U-shaped passage 50; A differential pressure sensing unit, comprising a first pressure sensor 31 arranged at the inlet of the second U-shaped passage 51 and a second pressure sensor 32 arranged at the outlet of the second U-shaped passage 51; A vibration sensing unit, comprising a first vibration sensor 40 arranged at the outside of the U-shaped bend of the second U-shaped passage 51 and a second vibration sensor 41 arranged at the outside of the U-shaped bend of the third U-shaped passage 52; A signal processing unit, which is electrically connected with the thermal sensing unit, the differential pressure sensing unit and the vibration sensing unit, is configured to receive the signals of each sensor and calculate the mass flow of the fluid through a data fusion algorithm.

[0024] In this embodiment, the thermal sensing unit 20, 21, 22 and 23 is arranged in the first U-shaped passage 50, and the stable flow characteristics of the straight section thereof are utilized for accurate thermal measurement; the differential pressure sensing unit 31 and 32 is arranged in the second U-shaped passage 51, and the differential pressure between the inlet and the outlet thereof is measured to reflect the flow rate; the vibration sensing unit 40 and 41 is arranged at the outside of the bend of the second and third U-shaped passages 51 and 52 respectively, and the Coriolis effect or flow-induced vibration generated when the fluid flows through the bend is utilized for measurement; the signal processing unit comprehensively utilizes the advantages of each sensor through a data fusion algorithm, realizing wide-range and high-precision mass flow measurement.

[0025] In one embodiment, a reference pressure sensor 30 is arranged in the expansion chamber 12 to measure the absolute pressure of the fluid and provide a pressure reference for the differential pressure sensing unit; the radii of curvature of the first, second and third U-shaped channels 50, 51 and 52 decrease in turn; the first and second temperature sensors 20 and 21 are arranged in an asymmetric layout; the distance between the second temperature sensor 21 and the micro-heater 23 is smaller than the distance between the first and second temperature sensors 20 and 21; a hydrophobic microporous membrane structure is arranged in the degassing chamber 11, one side of the hydrophobic microporous membrane is in contact with the fluid channel, and the other side is in communication with the exhaust channel; In this embodiment, the reference pressure sensor 30 provides an absolute pressure reference, making the differential pressure measurement have a clear physical meaning, and can also be used for fluid property calculation; the radii of curvature of the three U-shaped channels 50, 51 and 52 decrease in turn, so that the centrifugal effect and flow-induced vibration effect of the fluid are enhanced step by step, which is beneficial to the vibration sensing unit 40, 41 to detect the fluid characteristics more sensitively; the asymmetric layout of the first and second temperature sensors 20 and 21, especially the second temperature sensor 21 being closer to the micro-heater 23, can more accurately measure the initial temperature of the fluid before heating, improving the accuracy of thermal measurement. The hydrophobic microporous membrane structure in the degassing chamber 11 only allows gas to pass through while blocking liquid In addition, the present application also provides a microfluidic mass flowmeter measurement and control method, Step one, system initialization, drive the fluid to flow through the fluid channel, and synchronously start the thermal sensing unit, differential pressure sensing unit and vibration sensing unit; Step two, synchronously collect signals of each sensor, including temperature signals measured by the first and second temperature sensors 20 and 21, power signals of the micro-heater 23, temperature signals measured by the third temperature sensor 22, differential pressure signals measured by the first and second pressure sensors 31 and 32, and vibration frequency signals measured by the first and second vibration sensors 40 and 41; Step three, transmit all collected signals to the signal processing unit for parallel processing; based on the power of the micro-heater 23 and the signals of the first, second and third temperature sensors 20, 21 and 22, the first mass flow estimate of the fluid is calculated according to the thermal measurement principle; Based on the differential pressure signals of the first and second pressure sensors 31 and 32, and combined with the flow resistance characteristics of the second U-shaped channel 51, the uncompensated instantaneous flow value is calculated; At the same time, based on the vibration frequency signals of the first and second vibration sensors 40 and 41, the real-time density value of the fluid is calculated; Step four, using the real-time density value calculated in step three, dynamically density-compensate the uncompensated instantaneous flow rate value to obtain a second mass flow rate estimate; Step five, using an adaptive weighted data fusion algorithm, fuse the first mass flow rate estimate and the second mass flow rate estimate; wherein in the low flow range, the first mass flow rate estimate is preferred, and in the high flow range, the second mass flow rate estimate is preferred, and finally output a full-range high-precision mass flow rate value; This method uses multi-sensor signal parallel processing and adaptive data fusion, fully utilizes the advantages of each measurement principle, thermal measurement provides high sensitivity at low flow, differential pressure measurement provides stability at high flow, and vibration measurement provides real-time key density parameters for accurate compensation. The adaptive weighting algorithm intelligently adjusts the reliability of the two flow rate estimates in different flow ranges, thereby maintaining high measurement accuracy throughout the full flow range.

[0026] In one embodiment, the determination of the weight coefficient of the adaptive weighted data fusion algorithm in step five specifically includes the following steps, Step 5.1: Calculate the signal-to-noise ratio of the thermal sensor unit output signal at the current flow rate, and the intensity of the differential pressure sensor unit output signal; Step 5.2: According to the preset mapping relationship, assign a higher fusion weight to the sensor unit with high signal-to-noise ratio, and assign a higher fusion weight to the sensor unit with high signal intensity; Step 5.3: According to the weight determined in step 5.2, weighted average the two mass flow rate estimates to obtain the final mass flow rate value; In this embodiment, by evaluating the signal-to-noise ratio and intensity of each sensor signal in real time, the system can automatically identify which sensor data is more reliable under the current working condition and adjust its contribution to the final result accordingly. This dynamic weight adjustment ensures that the system can always maintain optimal measurement accuracy even when the fluid state changes, enhancing the adaptability and robustness of the flowmeter.

[0027] In one embodiment, a self-diagnosis process is also included, which is executed when the device is powered on or at a preset period, and the specific steps are, Step A: Apply a short heat pulse to the micro-heater 23 in the fluid static state; Step B: Detect the weak vibration signal caused by thermal expansion and contraction of the fluid due to the heat pulse through the first vibration sensor 40 and the second vibration sensor 41; Step C: analyze the response amplitude and waveform of the vibration signal, if the response is within the expected range, determine that the vibration sensing unit is working properly and complete the zero point calibration; if the response is abnormal or missing, trigger a sensor failure alarm; In this embodiment, the micro-heater 23 and the vibration sensors 40, 41 realize self-monitoring of the system. The thermal pulse causes the fluid to expand slightly, generating a pressure wave that is detected by the vibration sensor. This process verifies that the entire physical path from heating to vibration detection is working properly. This function not only ensures that the system is in good condition at startup, but also periodically checks during operation to detect sensor failures or performance degradation in a timely manner, greatly improving the reliability and maintainability of the system and reducing measurement errors caused by sensor drift or failure.

[0028] In one embodiment, a fluid property comprehensive analysis step is also included, specifically, Step X: read the absolute pressure value of the fluid measured by the reference pressure sensor 30 arranged in the expansion chamber 12; Step Y: combine the absolute pressure value with the real-time density value calculated by the vibration sensing unit in step three, and further calculate the dynamic or kinematic viscosity parameter of the fluid through the built-in fluid property model; Step Z: output the final mass flow rate value, density value, absolute pressure value, and viscosity parameter as a comprehensive parameter set describing the current fluid state; In this embodiment, by combining the absolute pressure measurement value 30 and the real-time density value, the viscosity parameter of the fluid can be calculated using fluid mechanics relationships. The final output is a comprehensive parameter set describing the fluid state, a multi-parameter fluid analyzer that can meet more complex process monitoring and quality control requirements.

[0029] In operation, the fluid flows from the inlet end 10, first passes through the degassing chamber 11, where the hydrophobic microporous membrane structure can effectively separate and discharge the gas bubbles entrained in the fluid, ensuring the accuracy of subsequent measurements. Then the fluid enters the expansion chamber 12, where the flow rate tends to be stable, and the reference pressure sensor 30 arranged here can measure the absolute pressure value of the fluid. Then the fluid flows through the first U-shaped channel 50, the second U-shaped channel 51, and the third U-shaped channel 52 to form a measurement flow channel; When the fluid flows through the first U-shaped channel 50, the thermal sensing unit starts to work: the micro-heater 23 heats the fluid, the first temperature sensor 20 and the second temperature sensor 21 (arranged in an asymmetric layout, with the second temperature sensor 21 closer to the micro-heater 23) measure the fluid temperature before heating, and the third temperature sensor 22 measures the fluid temperature after heating, and the first mass flow rate estimate is calculated by detecting the fluid temperature difference. The fluid then enters the second U-shaped channel 51, and the first pressure sensor 31 and the second pressure sensor 32 of the differential pressure sensing unit detect the pressure difference between the entrance and the exit of this section in real time, and the instantaneous flow rate value without compensation is calculated according to the flow resistance characteristics. At the same time, the first vibration sensor 40 and the second vibration sensor 41 arranged outside the U-shaped bends of the second U-shaped channel 51 and the third U-shaped channel 52 respectively detect the vibration frequency signals generated when the fluid flows through the U-shaped bends with decreasing curvature radius, and the real-time density value of the fluid is calculated by analyzing the differences between these signals. The signal processing unit synchronously receives and processes all sensor signals, first dynamically density-compensates the instantaneous flow rate value measured by the differential pressure sensing unit using the real-time density value, to obtain an accurate second mass flow rate estimate. Then, an adaptive weighted data fusion algorithm is used to dynamically allocate fusion weights according to the signal-to-noise ratio of the thermal sensing unit signals and the intensity of the differential pressure sensing unit signals at the current flow rate - preferentially using thermal measurement results at low flow rates, and preferentially using differential pressure measurement results at high flow rates, and finally calculating the final full-range high-precision mass flow rate value by weighted average; The system also has an online self-diagnosis function, which periodically or when the device is powered on, applies a short heat pulse to the micro-heater 23 in a fluid static state, and uses the first and second vibration sensors 40 and 41 to detect the weak vibration signals caused thereby, analyzes the response amplitude and waveform to judge the working state of the vibration sensing unit and complete zero-point calibration, ensuring the reliability of long-term operation of the system; Finally, the system not only outputs accurate mass flow rate values, but also combines the absolute pressure value measured by the reference pressure sensor 30 and the real-time density value calculated by the vibration sensing unit, uses the built-in fluid property model to further calculate the viscosity parameter of the fluid, and outputs a comprehensive parameter set including mass flow rate, density, absolute pressure and viscosity, to realize comprehensive monitoring of the fluid state.

[0030] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art can easily think of various changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A microfluidic mass flow meter, characterized in that: The device includes a microfluidic chip body (1), in which a fluid channel is provided. Between the inlet end (10) and the outlet end (13) of the fluid channel, a degassing chamber (11), an expansion chamber (12) and at least one measuring flow channel are arranged in sequence. The at least one measuring channel includes a first U-shaped channel (50), a second U-shaped channel (51), and a third U-shaped channel (52) connected in sequence. The fluid channel is also integrated with a thermal sensing unit, including a first temperature sensor (20) and a second temperature sensor (21) disposed in the inlet straight section of the first U-shaped channel (50), a micro heater (23) disposed at the end of the inlet straight section of the first U-shaped channel (50), and a third temperature sensor (22) disposed in the outlet straight section of the first U-shaped channel (50). The differential pressure sensing unit includes a first pressure sensor (31) disposed at the inlet of the second U-shaped channel (51) and a second pressure sensor (32) disposed at the outlet of the second U-shaped channel (51). The vibration sensing unit includes a first vibration sensor (40) disposed on the outside of the U-shaped bend of the second U-shaped channel (51) and a second vibration sensor (41) disposed on the outside of the U-shaped bend of the third U-shaped channel (52). The signal processing unit, electrically connected to the thermal sensing unit, differential pressure sensing unit, and vibration sensing unit, is configured to receive signals from each sensor and calculate the mass flow rate of the fluid using a data fusion algorithm.

2. The microfluidic mass flow meter according to claim 1, characterized in that: The expansion chamber (12) is equipped with a reference pressure sensor (30) for measuring the absolute pressure of the fluid and providing a pressure reference for the differential pressure sensing unit.

3. A microfluidic mass flow meter according to claim 1, characterized in that: The radii of curvature of the first U-shaped channel (50), the second U-shaped channel (51), and the third U-shaped channel (52) decrease sequentially.

4. A microfluidic mass flow meter according to claim 1, characterized in that: The first temperature sensor (20) and the second temperature sensor (21) are arranged in an asymmetrical layout; the distance between the second temperature sensor (21) and the micro heater (23) is smaller than the distance between the first temperature sensor (20) and the second temperature sensor (21).

5. A microfluidic mass flow meter according to claim 1, characterized in that: The degassing chamber (11) is provided with a hydrophobic microporous membrane structure. One side of the hydrophobic microporous membrane is in contact with the fluid channel, and the other side is connected to the exhaust channel.

6. A microfluidic mass flow meter measurement and control method according to any one of claims 1-5, characterized in that, Step 1: System initialization, drive fluid to flow through the fluid channel, and simultaneously start the thermal sensing unit, differential pressure sensing unit and vibration sensing unit; Step 2: Synchronously collect signals from each sensor, including the temperature signals measured by the first temperature sensor (20) and the second temperature sensor (21), the power signal of the micro heater (23), the temperature signal measured by the third temperature sensor (22), the pressure difference signal measured by the first pressure sensor (31) and the second pressure sensor (32), and the vibration frequency signal measured by the first vibration sensor (40) and the second vibration sensor (41). Step 3: Transmit all collected signals to the signal processing unit for parallel processing; wherein, based on the power of the micro heater (23) and the signals of the first, second, and third temperature sensors (20, 21, 22), the first mass flow rate estimate of the fluid is calculated according to the thermal measurement principle. Based on the pressure difference signal between the first pressure sensor (31) and the second pressure sensor (32), and combined with the flow resistance characteristics of the second U-shaped channel (51), the uncompensated instantaneous flow rate value is calculated. Meanwhile, based on the vibration frequency signals of the first vibration sensor (40) and the second vibration sensor (41), the real-time density value of the fluid is calculated; Step 4: Using the real-time density value calculated in Step 3, perform dynamic density compensation correction on the uncompensated instantaneous flow rate value to obtain the second mass flow rate estimate. Step 5: Use an adaptive weighted data fusion algorithm to fuse the first mass flow rate estimate and the second mass flow rate estimate; wherein, the first mass flow rate estimate is given priority in the low flow rate range, and the second mass flow rate estimate is given priority in the high flow rate range, and finally outputs a high-precision mass flow rate value across the entire range.

7. The method for measuring and controlling a microfluidic mass flow meter according to claim 6, characterized in that, The determination of the weight coefficients in the adaptive weighted data fusion algorithm described in step five specifically includes the following steps: Step 5.1: Calculate the signal-to-noise ratio of the output signal of the thermal sensing unit and the intensity of the output signal of the differential pressure sensing unit under the current flow rate; Step 5.2: According to the preset mapping relationship, assign higher fusion weights to sensing units with high signal-to-noise ratio and higher fusion weights to sensing units with high signal strength. Step 5.3: Based on the weights determined in Step 5.2, perform a weighted average of the two mass flow estimates to obtain the final mass flow value.

8. The microfluidic mass flow meter measurement and control method according to claim 6, characterized in that, It also includes a self-diagnostic process, which is executed when the device is powered on or at a preset cycle. The specific steps are as follows: Step A: While the fluid is stationary, apply a short-duration thermal pulse to the microheater (23); Step B: The weak vibration signal generated by the thermal expansion and contraction of the fluid caused by the thermal pulse is detected by the first vibration sensor (40) and the second vibration sensor (41); Step C: Analyze the response amplitude and waveform of the vibration signal. If the response is within the expected range, the vibration sensing unit is determined to be working normally and zero-point calibration is completed. If the response is abnormal or missing, a sensor fault alarm is triggered.

9. A microfluidic mass flow meter measurement and control method according to claim 6, characterized in that: It also includes a comprehensive analysis of fluid properties, specifically, Step X: Read the absolute fluid pressure value measured by the reference pressure sensor (30) installed in the expansion chamber (12); Step Y: Combine the absolute pressure value with the real-time density value calculated by the vibration sensing unit in step three, and further calculate the dynamic viscosity or kinematic viscosity parameter of the fluid using the built-in fluid property model; Step Z: Output the final mass flow rate, density, absolute pressure, and viscosity parameters together as a comprehensive parameter set describing the current fluid state.

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