Microwave flow sensing chip applied to fuel cell control

Abstract

The invention discloses a microwave flow sensing chip applied to fuel cell control. The microwave flow sensing chip comprises a micro-fluidic chip and a capacitor array sensor chip, the micro-fluidic chip comprises a micro-fluidic gas channel, a micro-fluidic liquid channel and a micro-fluidic mixing channel which are connected with one another; the micro-fluidic mixing channel comprises a plurality of micro-fluidic mixing channel units; the capacitor array sensing chip comprises a substrate and a capacitor sensing structure arranged on the substrate, the capacitor sensing structure comprises a plurality of bubble measuring units, and the plurality of bubble measuring units are bonded with the plurality of microfluidic mixing channel units one by one. The microwave flow sensing chip provided by the invention is formed by combining the micro-fluidic chip and the capacitor array sensing chip, has the capability of quickly and accurately measuring and controlling the gas flow, and can perform more reliable and efficient flow monitoring. According to the microwave flow sensing chip, the stability and performance of a fuel cell system can be remarkably improved, so that the application development of the microwave flow sensing chip in the field of energy conversion is promoted.

Description

Technical Field

[0001] The invention relates to a microwave flow sensor chip used for fuel cell control, belonging to the technical field of microwave flow sensors. Background Art

[0002] Against the backdrop of growing global energy demand and increasingly prominent environmental pollution issues, renewable energy technology is gradually becoming a hot area of ​​research. Among many renewable energy technologies, fuel cells show great application potential due to their high efficiency, cleanliness and sustainability. For fuel cells, their control technology is particularly critical, which is directly related to the efficiency of energy output, the safety of the system and the stability of operation. Fuel cells directly convert chemical energy into electrical energy through electrochemical reactions. In this process, microwave flow sensor chips play a vital role. This chip can accurately measure and control the flow of the reaction gas, thereby optimizing battery performance and ensuring the efficiency and stability of the energy conversion process. It is of great significance to promote the development and application of fuel cell technology.

[0003] Microwave flow sensor chips use advanced microwave technology to measure fluid flow. They accurately detect the speed and flow of fluids by emitting and receiving microwave signals. This sensor chip uses a non-contact measurement method, making it very suitable for flow monitoring in high temperature, high pressure or corrosive environments. Thanks to its fast response time and high measurement accuracy, microwave flow sensor chips can provide stable and reliable data while being unaffected by the physical and chemical properties of the fluid. In the field of fuel cell technology, the key role of microwave flow sensor chips is reflected in the real-time monitoring and control of the flow of hydrogen, air and other reaction gases, which is crucial to ensuring the efficient energy output and system stability of fuel cells. By accurately controlling the gas flow, microwave flow sensor chips help optimize the performance of fuel cells, improve their energy conversion efficiency, and thus promote the widespread application of fuel cell technology in the field of clean energy.

[0004] Although traditional flow meters, such as differential pressure and mass flow meters, have made significant contributions in the field of gas flow measurement, they still have limitations in terms of measurement accuracy, stability, response speed, and the influence of fluid density changes. Microfluidic channel technology effectively reduces the interference of environmental factors on measurement by precisely controlling gas flow. Capacitor array sensors are arranged at key positions in the microfluidic channel. When the gas flows, the dielectric properties of the capacitor array in the channel, such as gas density and flow rate, will change, resulting in changes in capacitance. There is a certain functional relationship between this capacitance change and the gas flow, which enables the gas flow to be measured with high precision. Therefore, the use of microfluidic technology combined with capacitor array sensors as microwave flow sensors to measure gas flow is becoming a rapidly developing emerging technology. The development of this technology not only improves the energy output efficiency of fuel cells, but also optimizes operating parameters, reduces fuel consumption, and improves the overall efficiency of the system. With the continuous advancement of technology, the application prospects of microwave flow sensors in the energy field will be broader and are expected to play a more important role in the future. Summary of the invention

[0005] The purpose of the present invention is to provide a microwave flow sensor chip for fuel cell control, which can solve the challenges faced by existing microwave flow sensors in applications, including interference from environmental factors, temperature compensation problems, and limitations of intelligent algorithms. The microwave flow sensor chip is specially designed for flow control of fuel cells. It is composed of a microfluidic chip and a capacitor array sensor chip. It has the ability to quickly and accurately measure and control gas flow, and can perform more reliable and efficient flow monitoring. Through this design, the stability and performance of the fuel cell system can be significantly improved, thereby promoting its application development in the field of energy conversion.

[0006] In a first aspect, the present invention provides a microwave flow sensor chip, including a microfluidic chip and a capacitive array sensor chip;

[0007] The microfluidic chip comprises a microfluidic gas channel and a microfluidic liquid channel connected to each other, a microfluidic mixing channel is connected to the connection between the microfluidic gas channel and the microfluidic liquid channel, and the microfluidic mixing channel comprises a plurality of microfluidic mixing channel units; the microfluidic gas channel is used to introduce gas, the microfluidic liquid channel is used to introduce liquid, one end of the microfluidic mixing channel is used to mix the gas in the microfluidic gas channel and the liquid in the microfluidic liquid channel to form a liquid with bubbles, and the liquid with bubbles is dispersed from one end of the microfluidic mixing channel through a plurality of the microfluidic mixing channel units and then converges at the other end of the microfluidic mixing channel;

[0008] The capacitive array sensor chip comprises a substrate and a capacitive sensing structure arranged on the substrate, the capacitive sensing structure comprises a plurality of bubble measuring units, and the plurality of bubble measuring units are bonded one by one with the plurality of microfluidic mixing channel units.

[0009] In one embodiment of the present invention, electrically controlled valves are provided at the connection between the microfluidic gas channel and the microfluidic liquid channel and the microfluidic mixing channel.

[0010] In one embodiment of the present invention, the ends of the microfluidic gas channel and the microfluidic liquid channel away from the microfluidic mixing channel are both connected to pluggable pipes; the end of the microfluidic mixing channel away from the microfluidic gas channel and the microfluidic liquid channel is provided with a drain port.

[0011] In one embodiment of the present invention, the microfluidic gas channel and the microfluidic liquid channel are both linear structures, the number of the microfluidic mixing channel units is five, the five microfluidic mixing channel units are arranged in parallel, and each of the microfluidic mixing channel units is connected to both ends of the microfluidic mixing channel.

[0012] In one embodiment of the present invention, the bubble measurement unit includes a capacitive sensing array measurement area, and the capacitive sensing array measurement area includes a capacitor; the capacitor is an interdigital capacitor, which includes two groups of electrodes, the two groups of electrodes are arranged adjacently and staggered and not in direct contact, and each group of electrodes is independently connected to a corresponding port set on the capacitor.

[0013] In one embodiment of the present invention, the two groups of electrodes are in the shape of two combs that are placed obliquely and staggered.

[0014] In one embodiment of the present invention, the capacitor uses metal as the electrode material and is coated on an insulating substrate through a chemical deposition process; when the capacitor is connected to a power supply, the charge is stored in the electric field between the two electrodes, and the electric field is mainly concentrated in the area between the electrodes, thereby generating a significant capacitance effect; its capacitance value depends on the area of ​​the electrodes, the distance between adjacent electrodes, the dielectric constant of the dielectric material, and the arrangement of the electrodes; by adjusting the above parameters, the size of the capacitance can be accurately controlled to optimize the performance of the sensor;

[0015] The capacitance value 0 of the capacitor is calculated by the following formula:

[0016]

[0017] Among them, ε ris the relative dielectric constant of the dielectric material, ε0 is the vacuum dielectric constant, N is the total index of the interdigitated electrodes, i.e. the total number of electrodes, L is the length of each electrode, t is the thickness of the electrode, and d is the spacing between adjacent electrodes.

[0018] In a second aspect, the present invention provides a flow sensor, comprising the microwave flow sensor chip.

[0019] In a third aspect, the present invention provides a liquid concentration detection method for fuel cell control, using the microwave flow sensor chip, comprising the following steps:

[0020] Step S101, input the liquid to be tested into the microfluidic liquid channel through a pluggable pipe, and then flow through the microfluidic mixing channel and enter the microfluidic mixing channel unit with one branch into five branches;

[0021] Step S102, using a capacitance array sensor chip to measure the liquid to be tested in the five-channel microfluidic mixing channel unit to obtain the capacitance value of the liquid to be tested, and averaging the five collected capacitance values;

[0022] Step S103, changing the concentration of the liquid to be tested and repeating the above operation to obtain the capacitance values ​​of liquids with different concentrations;

[0023] Step S104 , using COMSOL Multiphysics to perform simulation, and obtaining a curve of the relationship between the concentration of the liquid to be tested and the capacitance value; it can be seen from the curve that the higher the concentration of the liquid to be tested, the greater the capacitance value.

[0024] In a fourth aspect, the present invention provides a gas concentration detection method for fuel cell control, using the microwave flow sensor chip, comprising the following steps:

[0025] Step S201, input the gas to be tested into the microfluidic gas channel through a pluggable pipe, pass the liquid into the microfluidic liquid channel, control the flow of gas and liquid through an electronically controlled valve, form a liquid with bubbles after passing through the microfluidic mixing channel, and enter the microfluidic mixing channel unit with one branch into five branches;

[0026] Step S202, using a capacitance array sensor chip to measure bubbles in the liquid with bubbles in the five-channel microfluidic mixing channel unit, and averaging the capacitance values ​​obtained by measuring the bubbles;

[0027] Step S203, changing the flow rate of the gas introduced, while the liquid still maintains a uniform flow, repeating the above operation to obtain the capacitance values ​​of the bubbles under multiple different gas flow rates;

[0028] Step S204, using COMSOL Multiphysics to perform simulation and obtain a curve showing the relationship between gas flow rate and capacitance value; it can be seen from the curve that after changing the gas flow rate, the size and flow rate of the bubbles change accordingly, thereby changing the dielectric constant in the channel, and ultimately causing a change in the capacitance value; when the bubbles pass through the interdigital capacitance sensor, the capacitance value changes significantly; by monitoring the change in capacitance value, the presence of bubbles is detected and their size and flow rate are measured, thereby determining the gas flow rate.

[0029] The beneficial effects of the present invention are:

[0030] The microwave flow sensor chip has high precision. Through the integration of microfluidic chip and capacitive array sensor chip, it can accurately measure tiny gas flow, and its measurement accuracy significantly exceeds that of traditional technology.

[0031] The microwave flow sensor chip can respond quickly; the capacitor array sensor chip used in the present invention has been optimized to achieve efficient use of capacitor electrodes and significantly improve measurement accuracy. This improvement can achieve real-time monitoring of gas flow, and is particularly suitable for tracking and analyzing dynamic gas flow;

[0032] The microwave flow sensor chip has a simple structure and low cost; the application of microfluidic technology greatly simplifies the structure and has a low cost, making it suitable for large-scale production and application.

[0033] The microwave flow sensor chip has wide applicability; the microwave flow sensor chip is suitable for a variety of gas flow measurement scenarios, can adapt to various industrial and laboratory environments, and has extremely high application flexibility.

[0034] In summary, the microwave flow sensor chip for fuel cell control provided by the present invention can solve the challenges faced by existing microwave flow sensors in applications, including interference from environmental factors, problems with temperature compensation, and limitations of intelligent algorithms. The microwave flow sensor chip is specially designed for flow control of fuel cells. It is composed of a combination of a microfluidic chip and a capacitor array sensor chip. It has the ability to quickly and accurately measure and control gas flow, and can perform more reliable and efficient flow monitoring. Through this design, the stability and performance of the fuel cell system can be significantly improved, thereby promoting its application development in the field of energy conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the disassembly of the microwave flow sensor chip provided by the present invention.

[0036] Figure 2 This is a schematic diagram of the structure of the microfluidic chip provided by the present invention.

[0037] Figure 3 This is a partial structural schematic diagram of the capacitive array sensor chip provided by the present invention.

[0038] Figure 4 This is a diagram of the capacitance simulation results of the present invention.

[0039] Figure 5 This is a simulation result diagram of the flow sensor of the present invention.

[0040] In the figure: 1. microfluidic gas channel; 2. microfluidic liquid channel; 3. microfluidic mixing channel; 31. microfluidic mixing channel unit; 4. capacitive array sensor chip; 41. substrate; 42. bubble measurement unit; 421. capacitive sensor array measurement area; 5. pluggable pipeline; 6. electrically controlled valve; 7. drain port; 8. microfluidic chip. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions.

[0043] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be a connection between two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] Please refer to Figure 1 , Figure 2 and Figure 3 An embodiment of the present application provides a microwave flow sensor chip, including a microfluidic chip 8 and a capacitor array sensor chip 4.

[0045] In some embodiments, the microfluidic chip 8 includes a microfluidic gas channel 1 and a microfluidic liquid channel 2 connected to each other, and a microfluidic mixing channel 3 is connected at the connection between the microfluidic gas channel 1 and the microfluidic liquid channel 2, and the microfluidic mixing channel 3 includes a plurality of microfluidic mixing channel units 31; the microfluidic gas channel 1 is used to pass gas, and the microfluidic liquid channel 2 is used to pass liquid, and one end of the microfluidic mixing channel 3 is used to mix the gas in the microfluidic gas channel 1 and the liquid in the microfluidic liquid channel 2 to form a liquid with bubbles, and the liquid with bubbles is dispersed from one end of the microfluidic mixing channel 3 through a plurality of the microfluidic mixing channel units 31 and then converges at the other end of the microfluidic mixing channel 3.

[0046] Optionally, the microfluidic gas channel 1 and the microfluidic liquid channel 2 are both linear structures, and a linear structure layout is adopted to facilitate direct flow of gas or fluid.

[0047] Furthermore, there are five microfluidic mixing channel units 31 , which are arranged in parallel, and each of the microfluidic mixing channel units 31 is connected to both ends of the microfluidic mixing channel 3 .

[0048] In this embodiment, gas and liquid enter the microfluidic mixing channel 3 through the microfluidic gas channel 1 and the microfluidic liquid channel 2 respectively, and then are accurately mixed in the microfluidic mixing channel 3. The microfluidic mixing channel 3 adopts a branching design, which is divided into five branches, each of which flows through a microfluidic mixing channel unit 31, and each microfluidic mixing channel unit 31 is bonded with a capacitive sensor chip. This layout allows the gas and liquid to be fully mixed in the microfluidic mixing channel 3, and then sensed and detected by five capacitive sensor chips in turn. After analysis by the capacitive array sensor chip 4, the mixed fluid converges again and finally converges to the outlet of the microfluidic mixing channel 3. This structural design optimizes the flow characteristics of the fluid, ensures that the sensor chip can effectively mix and detect gas and liquid, and improves the measurement accuracy and efficiency of the microfluidic system.

[0049] Optionally, an electrically controlled valve 6 is provided at the connection between the microfluidic gas channel 1 and the microfluidic liquid channel 2 and the microfluidic mixing channel 3 .

[0050] In this embodiment, the electric control valve 6 is used to accurately control the flow of gas and liquid. By adjusting the opening of the electric control valve 6, the flow rate of the fluid can be controlled, thereby achieving accurate regulation of the flow of liquid and gas in the microfluidic system to ensure the stability and repeatability of the system. At the same time, by adjusting the gas flow rate and maintaining the uniform flow of the liquid, gas-liquid mixing of different mixing ratios can be achieved to form a liquid with bubbles.

[0051] In some embodiments, the microfluidic gas channel 1 and the microfluidic liquid channel 2 are both connected to a pluggable pipe 5 at one end away from the microfluidic mixing channel 3 .

[0052] In some embodiments, a drain port 7 is provided at one end of the microfluidic mixing channel 3 away from the microfluidic gas channel 1 and the microfluidic liquid channel 2. The drain port 7 is connected to an outlet of the microfluidic mixing channel 3.

[0053] In some embodiments, the capacitive array sensor chip 4 includes a substrate 41 and a capacitive sensing structure disposed on the substrate 41 , the capacitive sensing structure includes a plurality of bubble measuring units 42 , and the plurality of bubble measuring units 42 are bonded one by one to a plurality of the microfluidic mixing channel units 31 .

[0054] In the present embodiment, the substrate 41 is made of glass, and the capacitor array sensor chip 4 uses the glass substrate 41 as its structural basis, and a precise capacitor sensing structure is arranged on the substrate 41. The capacitor sensing structure is provided with a bubble measuring unit 42, and a plurality of bubble measuring units 41 are bonded one by one with a plurality of microfluidic mixing channel units 31. The gas-liquid mixture flowing in the microfluidic mixing channel 3 will form a liquid flow containing bubbles. At this time, the capacitor array sensor chip 4 can accurately detect the generation of bubbles inside the microfluidic chip 8 by monitoring the change of the capacitance value in real time. Due to the significant difference in the dielectric constant between the bubble and the liquid medium, when the bubble passes through the capacitor sensing area, it will cause a significant fluctuation in the capacitance value. The capacitor array sensor chip 4 uses this principle to detect and identify bubbles in real time, ensuring the accuracy of the measurement process. Compared with directly measuring the capacitance value of the gas, the capacitor array sensor chip 4 shows higher accuracy when detecting the capacitance value of the bubble, providing an efficient and reliable technical means for monitoring bubbles in the microfluidic system.

[0055] Furthermore, the bubble measurement unit 42 includes a capacitive sensing array measurement area 421, and the capacitive sensing array measurement area 421 includes a capacitor, which is an interdigital capacitor, including two groups of electrodes, and the two groups of electrodes are arranged adjacently and staggered without direct contact, and each group of electrodes is independently connected to a corresponding port set on the capacitor.

[0056] Optionally, the two groups of electrodes are shaped like two combs that are placed obliquely and staggered.

[0057] In this embodiment, two groups of electrodes are arranged in a staggered manner, resembling two combs placed at an angle and in an staggered manner. The two groups of electrodes are adjacent to each other but not directly in contact with each other, and each group of electrodes is independently connected to the corresponding port of the capacitor. The overlapping area between the electrodes, i.e., the sensitive area of ​​the capacitor, determines the size of the capacitance value. By increasing the number of electrodes or extending their length, the capacitance value can be effectively increased, thereby improving the sensitivity of the sensor.

[0058] Compared with conventional interdigital capacitors, the electrodes of the interdigital capacitor provided by the present invention are designed in the shape of two combs placed obliquely and staggered, arranged in a staggered manner, while the conventional interdigital capacitors use vertically placed electrodes. This design makes the area utilization rate of the capacitor electrodes in the present invention higher, so the electrode overlap area is larger, the capacitance value is correspondingly larger, and thus a higher measurement sensitivity is achieved.

[0059] Optionally, the capacitor array in the present invention uses metal copper as the electrode material and is directly coated on an insulating substrate through a chemical deposition process. Its working principle is based on the electric field formed between two electrodes: when the capacitor is connected to a power supply, the charge is stored in the electric field between the two electrodes. Since the distance between the electrodes is very small and the arrangement is close, the electric field is mainly concentrated in the area between the electrodes, thereby producing a significant capacitance effect. Its capacitance value depends on the area of ​​the electrode, the distance between adjacent electrodes, the dielectric constant of the dielectric material, and the arrangement of the electrodes. By adjusting these parameters, the size of the capacitance can be accurately controlled, thereby optimizing the performance of the sensor.

[0060] The capacitance value C of the capacitor can be calculated by the following approximate formula:

[0061]

[0062] ε r is the relative dielectric constant of the dielectric material, ε0 is the vacuum dielectric constant, N is the total index of the interdigitated electrodes, i.e. the total number of electrodes, L is the length of each electrode, t is the thickness of the electrode, and d is the spacing between adjacent electrodes.

[0063] Specifically, in this embodiment, the capacitor line width is 100 μm, the spacing is 95 μm, the number of fingers is 42, and the length is 1.9 nm; the surface metal thickness of the two capacitors is 500 nm, and the substrate thickness is 1 mm; at an operating frequency of 1 MHz, the capacitance of the designed capacitor sensor is 17.29 pF, such as Figure 4 As shown, the simulation results show that the capacitance value of the device remains unchanged at an operating frequency of 0-1GHz, proving that the capacitor has good stability.

[0064] In addition, an embodiment of the present application also provides a flow sensor, including the microwave flow sensor chip.

[0065] In addition, the embodiment of the present application also provides a liquid concentration detection method for fuel cell control, using the microwave flow sensor chip, including the following steps:

[0066] Step S101, input the liquid to be tested into the microfluidic liquid channel 2 through the pluggable pipe 5, and then flow through the microfluidic mixing channel 3 and enter the microfluidic mixing channel unit 31 which is divided into five branches;

[0067] Step S102, using the capacitance array sensor chip 4 to measure the liquid to be tested in the five-channel microfluidic mixing channel unit 31, to obtain the capacitance value of the liquid to be tested, and averaging the five collected capacitance values;

[0068] Step S103, changing the concentration of the liquid to be tested and repeating the above operation to obtain the capacitance values ​​of liquids with different concentrations;

[0069] Step S104 , using COMSOL Multiphysics to perform simulation, and obtaining a curve of the relationship between the concentration of the liquid to be tested and the capacitance value; it can be seen from the curve that the higher the concentration of the liquid to be tested, the greater the capacitance value.

[0070] The microfluidic chip 8 uses a standard PDMS (polydimethylsiloxane) manufacturing process and is suitable for manufacturing microfluidic structures with high precision requirements; the capacitance array sensor chip 4 is used to measure the capacitance value of the liquid to be tested.

[0071] In addition, the embodiment of the present application also provides a gas concentration detection method for fuel cell control, using the microwave flow sensor chip, including the following steps:

[0072] Step S201, input the gas to be tested into the microfluidic gas channel 1 through the pluggable pipe 5, pass the liquid into the microfluidic liquid channel 2, control the flow of gas and liquid through the electronically controlled valve 6, form a liquid with bubbles after passing through the microfluidic mixing channel 3, and enter the microfluidic mixing channel unit 31 with one branch into five branches;

[0073] Step S202, using the capacitance array sensor chip 4 to measure the bubbles in the liquid with bubbles in the five-channel microfluidic mixing channel unit 31, and taking an average of the capacitance values ​​obtained by measuring the bubbles;

[0074] Step S203, changing the flow rate of the gas introduced, while the liquid still maintains a uniform flow, repeating the above operation to obtain the capacitance values ​​of the bubbles under multiple different gas flow rates;

[0075] Step S204, using COMSOL Multiphysics to perform simulation and obtain a curve showing the relationship between gas flow rate and capacitance value; it can be seen from the curve that after changing the gas flow rate, the size and flow rate of the bubbles change accordingly, thereby changing the dielectric constant in the channel, and ultimately causing a change in the capacitance value; when the bubbles pass through the interdigital capacitance sensor, the capacitance value changes significantly; by monitoring the change in capacitance value, the presence of bubbles is detected and their size and flow rate are measured, thereby determining the gas flow rate.

[0076] like Figure 5 As shown, a liquid with a dielectric constant of 80.36 is passed into microfluidic liquid channel 2, and no gas is passed, and the capacitance value is measured to be 94pF. Subsequently, a small amount of gas is passed into microfluidic gas channel 1, and the dielectric constant in the channel is reduced to 79.36, and the corresponding capacitance value is also reduced to 93pF. As the gas flow rate gradually increases, the dielectric constant further decreases, and the capacitance value also decreases therewith. The above-mentioned bubble generated can change the dielectric constant in the channel in the microfluidic channel, because the dielectric constant of the bubble is usually much lower than the dielectric constant of the liquid (such as water). Therefore, when the bubble passes through the interdigital capacitance sensor, the capacitance value will change significantly. By monitoring the change of the capacitance value, the existence of the bubble can be detected and its size and flow rate can be measured, so as to determine the flow rate of the gas.

[0077] Specifically, the microfluidic fluid channel has a diameter of 100μm, a thickness of 50μm, a capacitor thickness of 500nm, and a glass slide substrate. The microfluidic channel will be formed on the substrate by PDMS bonding after preparation. The capacitor electrode should be placed at the bottom of the microfluidic channel to ensure that the electric field can pass through the fluid in the channel. Metal electrodes are deposited on the glass substrate by photolithography. The specific steps include substrate cleaning, photoresist coating, mask alignment and exposure, development, electrode metal deposition, and stripping. The microfluidic channel is formed with a PDMS mold, which is then bonded to the electrode substrate to form a closed microfluidic system.

[0078] In addition, the present invention provides a microwave flow sensor chip for fuel cell control. Taking hydrogen fuel cells as an example, the technology directly converts the chemical energy of hydrogen (H2) and oxygen (O2) into electrical energy through electrochemical reactions. Therefore, the flow control of hydrogen and oxygen is crucial to the performance of fuel cells. The present invention passes hydrogen and oxygen into a microfluidic gas channel after mixing them in a precise proportion, and passes liquid into a microfluidic liquid channel at the same time. The flow of gas and liquid is precisely regulated by an electric control valve, and the mixed gas and liquid form a liquid containing bubbles in the mixing channel. The bubble-containing liquid is shunted into five independent microfluidic mixing channel units through a one-to-five branch channel, and each microfluidic mixing channel unit is equipped with a capacitor array sensor chip. The capacitance value obtained by measuring the bubbles is calculated and its average value is used as a quantitative indicator of the flow. The above measurement process is repeated by changing the mixing ratio of hydrogen and oxygen and the flow rate of the mixed gas. Finally, with the help of COMSOL Multiphysics simulation technology, the optimal hydrogen-oxygen mixing ratio and flow rate are determined to optimize the performance of the fuel cell.

[0079] At present, one of the commonly used flow sensors in hydrogen fuel cell control is the Siargo MF5000 series gas mass flow meter, which is favored for its high sensitivity, high precision and strong anti-interference ability. However, its cost is relatively high, and it is also large in size and weight, which limits its applicability in certain application scenarios. In contrast, the microwave flow sensor chip provided by the present invention has the advantages of small size and low cost. If applied to industrial production, it will significantly reduce costs and bring economic benefits.

[0080] In summary, the microwave flow sensor chip for fuel cell control provided by the present application shows great application potential in the field of precision fluid control and analysis, and the combination of microfluidic technology and capacitive array sensor chip. This technology provides support for high-precision microfluidic operations by accurately monitoring gas flow, thereby promoting progress in fields such as biomedicine, chemistry and environmental science. With the development of microfluidic technology, the integration and miniaturization level of capacitive sensors continue to improve, enabling them to better adapt to the needs of various microfluidic systems. If combined with artificial intelligence and big data analysis, the microfluidic capacitance detection system is expected to achieve functions such as automatic correction, environmental compensation and intelligent analysis. These advances will further improve the accuracy of detection and expand its scope of application in different fields.

[0081] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A microwave flow sensor chip, characterized in that: Including microfluidic chips and capacitive array sensor chips; The microfluidic chip comprises a microfluidic gas channel and a microfluidic liquid channel connected to each other, a microfluidic mixing channel is connected to the connection between the microfluidic gas channel and the microfluidic liquid channel, and the microfluidic mixing channel comprises a plurality of microfluidic mixing channel units; the microfluidic gas channel is used to introduce gas, the microfluidic liquid channel is used to introduce liquid, one end of the microfluidic mixing channel is used to mix the gas in the microfluidic gas channel and the liquid in the microfluidic liquid channel to form a liquid with bubbles, and the liquid with bubbles is dispersed from one end of the microfluidic mixing channel through a plurality of the microfluidic mixing channel units and then converges at the other end of the microfluidic mixing channel; The capacitive array sensor chip comprises a substrate and a capacitive sensing structure arranged on the substrate, the capacitive sensing structure comprises a plurality of bubble measuring units, and the plurality of bubble measuring units are bonded one by one with the plurality of microfluidic mixing channel units.

2. The microwave flow sensor chip according to claim 1, characterized in that: The microfluidic gas channel and the connection between the microfluidic liquid channel and the microfluidic mixing channel are provided with an electrically controlled valve.

3. The microwave flow sensor chip according to claim 1, characterized in that: The ends of the microfluidic gas channel and the microfluidic liquid channel away from the microfluidic mixing channel are both connected with pluggable pipes; the end of the microfluidic mixing channel away from the microfluidic gas channel and the microfluidic liquid channel is provided with a liquid discharge port.

4. The microwave flow sensor chip according to claim 1, characterized in that: The microfluidic gas channel and the microfluidic liquid channel are both linear structures. There are five microfluidic mixing channel units, which are arranged in parallel. Each of the microfluidic mixing channel units is connected to both ends of the microfluidic mixing channel.

5. The microwave flow sensor chip according to claim 1, characterized in that: The bubble measurement unit includes a capacitive sensing array measurement area, and the capacitive sensing array measurement area includes a capacitor; the capacitor is an interdigital capacitor, which includes two groups of electrodes, the two groups of electrodes are arranged adjacently and staggered and not in direct contact, and each group of electrodes is independently connected to a corresponding port set on the capacitor.

6. The microwave flow sensor chip according to claim 5, characterized in that: The two groups of electrodes are in the shape of two combs which are placed obliquely and staggered.

7. The microwave flow sensor chip according to claim 5, characterized in that: The capacitor uses metal as the electrode material and is coated on an insulating substrate through a chemical deposition process; when the capacitor is connected to a power source, the charge is stored in the electric field between the two electrodes, and the electric field is mainly concentrated in the area between the electrodes, thereby generating a significant capacitance effect; The capacitance value depends on the area of ​​the electrodes, the distance between adjacent electrodes, the dielectric constant of the dielectric material, and the arrangement of the electrodes. By adjusting the above parameters, the capacitance can be precisely controlled to optimize the performance of the sensor. The capacitance value C of the capacitor is calculated by the following formula: Among them, ε r is the relative dielectric constant of the dielectric material, ε0 is the vacuum dielectric constant, N is the total index of the interdigitated electrodes, i.e. the total number of electrodes, L is the length of each electrode, t is the thickness of the electrode, and d is the spacing between adjacent electrodes.

8. A flow sensor, characterized in that: The microwave flow sensor chip comprises the microwave flow sensor chip as described in any one of claims 1 to 7.

9. A liquid concentration detection method for fuel cell control, using the microwave flow sensor chip according to any one of claims 1 to 7, comprising the following steps: Step S101, input the liquid to be tested into the microfluidic liquid channel through a pluggable pipe, and then flow through the microfluidic mixing channel and enter the microfluidic mixing channel unit with one branch into five branches; Step S102, using a capacitance array sensor chip to measure the liquid to be tested in the five-channel microfluidic mixing channel unit to obtain the capacitance value of the liquid to be tested, and averaging the five collected capacitance values; Step S103, changing the concentration of the liquid to be tested and repeating the above operation to obtain the capacitance values ​​of liquids with different concentrations; Step S104, using COMSOL Multiphysics to perform simulation to obtain a curve showing the relationship between the concentration of the liquid to be measured and the capacitance value; It can be seen from the curve that the higher the concentration of the liquid to be tested, the larger the capacitance value.

10. A gas concentration detection method for fuel cell control, using the microwave flow sensor chip according to any one of claims 1 to 7, comprising the following steps: Step S201, input the gas to be tested into the microfluidic gas channel through a pluggable pipe, pass the liquid into the microfluidic liquid channel, control the flow of gas and liquid through an electronically controlled valve, form a liquid with bubbles after passing through the microfluidic mixing channel, and enter the microfluidic mixing channel unit with one branch into five branches; Step S202, using a capacitance array sensor chip to measure bubbles in the liquid with bubbles in the five-channel microfluidic mixing channel unit, and averaging the capacitance values ​​obtained by measuring the bubbles; Step S203, changing the flow rate of the gas introduced, while the liquid still maintains a uniform flow, repeating the above operation to obtain the capacitance values ​​of the bubbles under multiple different gas flow rates; Step S204, using COMSOL Multiphysics to perform simulation to obtain a curve showing the relationship between gas flow rate and capacitance value; It can be seen from the curve that after changing the gas flow rate, the size and flow rate of the bubbles will change accordingly, which in turn changes the dielectric constant in the channel, and ultimately leads to a change in the capacitance value; when the bubbles pass through the interdigital capacitance sensor, the capacitance value will change significantly; by monitoring the change in capacitance value, the presence of bubbles can be detected and their size and flow rate can be measured, thereby determining the gas flow rate.

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