Microfluidic device based on wafer bonding and control method thereof

Abstract

The application discloses a kind of microfluidic device based on wafer bonding and its control method, device first substrate and second substrate, a group of end faces of the first substrate is formed with first recess, another group of end faces of the first substrate is provided with first perforation that communicates the first recess;A group of end faces of the second substrate is formed with second recess;Another group of end faces of the second substrate is provided with second perforation that communicates the second recess;Wherein, the first substrate and the second substrate are connected by bonding process, make the first recess and the second recess closed formation as the micro flow pipe for fluid movement, the first perforation and the second perforation are located at both ends of the micro flow pipe, flow sensing unit is arranged in the micro flow pipe.The present application utilizes micro flow pipe micro machining to combine flow sensing unit, improves the detection precision of fluid, improves fluid control flexibility and fluid control precision, effectively simplifies the device structure.

Description

Technical Field

[0001] This invention relates to the field of microfluidics, and more specifically, to a microfluidic device and its control method based on wafer bonding. Background Technology

[0002] Microfluidics, as a laboratory chip technology, has advantages such as high integration, small size, low cost, and fast response. It is widely used in fields such as biomedicine, chemical analysis, and environmental monitoring. Microfluidic devices are the core components of microfluidics, and their performance directly affects the operating efficiency and accuracy of the entire microfluidic system. Therefore, research on microfluidics has important practical significance.

[0003] Currently, microfluidic devices are mainly used in product dispensing technology. Dispensing technology involves applying, potting, or dripping liquids onto products to achieve functions such as adhesion, encapsulation, insulation, fixation, and surface smoothing. Traditional microfluidic devices used for dispensing primarily rely on mechanical microchannel fabrication, which lacks flexibility. The microchannels are extremely small and complex, and the mechanical processing is easily affected by complex factors such as surface tension, capillary forces, and adhesive forces, making it difficult to ensure the uniformity of microchannel fabrication. In other words, mechanically fabricating the microchannels of a microfluidic device is very difficult. Furthermore, it is impossible to precisely detect and control the dispensing volume and flow rate, leading to uneven dispensing or inaccurate positioning of the liquid on the product surface.

[0004] Therefore, how to design a microfluidic device with strong control flexibility, simple structure and high detection accuracy is an extremely important technical problem to be solved. Summary of the Invention

[0005] To overcome the shortcomings of existing equipment for dispensing, dripping, and other processes, such as weak fluid control flexibility, complex structure, and low detection accuracy, this invention provides a microfluidic device and its control method based on wafer bonding.

[0006] The primary objective of this invention is to solve the aforementioned technical problems. The technical solution of this invention is as follows:

[0007] The first aspect of the present invention provides a microfluidic device based on wafer bonding, comprising: a first substrate and a second substrate, wherein a first groove is formed on a set of end faces of the first substrate, and a first through hole communicating with the first groove is provided on another set of end faces of the first substrate; a second groove is formed on a set of end faces of the second substrate; and a second through hole communicating with the second groove is provided on another set of end faces of the second substrate; wherein the first substrate and the second substrate are connected by a bonding process, such that the first groove and the second groove are closed to form a microfluidic channel for fluid movement, the first through hole and the second through hole are located at both ends of the microfluidic channel, and a flow sensing unit is disposed inside the microfluidic channel.

[0008] Preferably, the first groove and the first perforation are formed on two sets of opposite end faces of the first substrate; the second groove and the second perforation are formed on two sets of opposite end faces of the second substrate, the first groove and the second groove have the same size specifications, and the microfluidic channel, the first perforation and the second perforation have the same radius.

[0009] Preferably, the first perforation and the second perforation are distributed in a 180° centrally symmetrical manner with the middle position of the microfluidic channel as the center.

[0010] Preferably, the second substrate comprises a first wafer and a second wafer, with one side of the first wafer connected to one side of the second wafer; the lower end face of the first wafer is provided with a first channel, and the lower end face of the second wafer is provided with a second channel, the first channel and the second channel being connected to form the first groove; the first through hole is disposed on the first wafer.

[0011] Preferably, the first wafer includes a rectangular body and a trapezoidal frustum with trapezoidal surfaces on all four sides. The lower end face of the rectangular body is connected to the upper end face of the trapezoidal frustum. A first through hole is provided in the middle of the rectangular body, and a second through hole is provided in the middle of the trapezoidal frustum. The first through hole and the second through hole are connected to form the second through hole.

[0012] Preferably, the trapezoidal angle of the trapezoidal surface of the frustum is 45 degrees.

[0013] Preferably, the flow sensing unit includes a first resistive film, a heating resistive film, and a second resistive film. The first and second resistive films are disposed on both sides of the heating resistive film, and the heating resistive film heats up the first and second resistive films on both sides of the heating resistive film through thermal conduction.

[0014] Preferably, there are two sets of the first perforations, with the two sets of the first perforations respectively connected to both ends of the first groove, and the second perforation connected to the middle position of the second groove;

[0015] Alternatively, there may be two sets of the second perforations, with the two sets of the second perforations respectively connected to both ends of the second groove, and the first perforation connected to the middle position of the first groove.

[0016] This invention also proposes a control method for a microfluidic device based on wafer bonding, comprising the following steps:

[0017] S1. Driving fluid is injected from a first perforation in the first substrate;

[0018] S2. The fluid injected into the first perforation flows through the flow sensing unit in the microfluidic channel, and the flow rate of the fluid flowing through the flow sensing unit is detected by the flow sensing unit;

[0019] S3. Determine whether the flow rate of the fluid is greater than a preset threshold. If yes, stop the injection of the fluid from the first perforation in the first substrate, so that the fluid stops flowing in the microfluidic channel. If no, the fluid continues to flow in the microfluidic channel, and proceed to step S4.

[0020] S4. The fluid flowing in the microfluidic channel is dripped from the second perforation in the second substrate onto a preset workpiece below the second perforation.

[0021] Preferably, the flow sensing unit includes a first resistive film, a heating resistive film, and a second resistive film. The first and second resistive films are disposed on both sides of the heating resistive film, and the heating resistive film heats up the first and second resistive films on both sides of the heating resistive film through heat conduction.

[0022] When no fluid flows through the microfluidic channel, the temperatures of the first resistive membrane and the second resistive membrane are the same. When fluid flows through the microfluidic channel, heat transfer occurs in the first resistive membrane, the heating resistive membrane, and the second resistive membrane along the fluid flow direction. The first resistive membrane, which comes into contact with the fluid first, cools down. The second resistive membrane, which comes into contact with the fluid later, experiences heat transfer through the heating resistive membrane in the middle, causing the second resistive membrane to heat up. A temperature difference is generated between the first and second resistive membranes. Based on this temperature difference, the flow rate is calculated using a flow rate formula to convert the temperature difference into the flow rate of the fluid.

[0023] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0024] This invention proposes a microfluidic device and its control method based on wafer bonding. The microfluidic device is constructed by bonding a first substrate and a second substrate, so that the first groove and the second groove are closed to form a microfluidic channel for fluid movement. The bonding process improves the sealing performance of the microfluidic channel. A flow sensing unit is set in the microfluidic channel to improve the detection accuracy of the fluid. By combining the microfabrication of the microfluidic channel with the flow sensing unit, the flexibility and accuracy of fluid control are improved, and the device structure is effectively simplified. Attached Figure Description

[0025] Figure 1 A cross-sectional view of a microfluidic device based on wafer bonding provided in an embodiment of this application;

[0026] Figure 2 An exploded view of a microfluidic device based on wafer bonding provided in an embodiment of this application;

[0027] Figure 3 A first structural diagram of a microfluidic device based on wafer bonding provided in an embodiment of this application;

[0028] Figure 4 A second substrate structure diagram provided for an embodiment of this application;

[0029] Figure 5 A second structural diagram of a microfluidic device based on wafer bonding is provided for an embodiment of this application;

[0030] Figure 6 A third structural diagram of a microfluidic device based on wafer bonding is provided for an embodiment of this application;

[0031] Figure 7 This is a flowchart illustrating a control method for a microfluidic device based on wafer bonding, provided in an embodiment of this application. Detailed Implementation

[0032] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0033] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0034] Example 1

[0035] like Figure 1As shown, the present invention provides a microfluidic device based on wafer bonding, comprising: a first substrate 1 and a second substrate 2; a first groove 3 is formed on one set of end faces of the first substrate 1, and a first through hole 4 communicating with the first groove 3 is provided on the other set of end faces of the first substrate 1; a second groove 5 is formed on one set of end faces of the second substrate 2; and a second through hole 6 communicating with the second groove 5 is provided on the other set of end faces of the second substrate 2; wherein, see Figure 2 and Figure 3 The first substrate 1 and the second substrate 2 are connected by a bonding process, so that the first groove 3 and the second groove 5 are closed to form a microfluidic channel 7 for fluid movement. The first perforation 4 and the second perforation 6 are located at both ends of the microfluidic channel 7. A flow sensing unit 8 is provided inside the microfluidic channel 7. The first groove 3, the first perforation 4, the second groove 5 and the second perforation 6 are all formed by dry etching.

[0036] In this design, the first perforation 4 and the second perforation 6 are symmetrically distributed at 180° with the center of the microfluidic channel 7. The symmetry of the first perforation 4 and the second perforation 6 with the center of the center of the microfluidic channel 7 allows for sufficient channel space for the flow sensing unit 8 to perform detection. At the same time, the symmetrical structure allows the dimensions of the first groove 3 and the second groove 5 to be set to be the same. The etching positions of the first perforation 4 and the second perforation 6 can be aligned with the extreme ends of the first groove 3 and the second groove 5. The ends of the first groove 3 and the second groove 5 are easy to identify and locate, reducing the processing difficulty and preventing misalignment and leakage of the inner wall of the microfluidic channel 7.

[0037] In this design, the first groove 3 and the first perforation 4 are formed on two sets of opposite end faces of the first substrate 1; the second groove 5 and the second perforation 6 are formed on two sets of opposite end faces of the second substrate 2. The first groove 3 and the second groove 5 have the same size specifications, and the microfluidic channel 7, the first perforation 4, and the second perforation 6 have the same radius. This minimizes the length of the first perforation 4 and the second perforation 6, and makes the processing of the two sets of opposite end faces most convenient. The radius of the microchannel is in the range of 15-50 μm.

[0038] In this plan, see Figure 4 The second substrate 2 has a first wafer 21 and a second wafer 22, with one side of the first wafer 21 connected to one side of the second wafer 22; the lower end face of the first wafer 22 is provided with a first channel, and the lower end face of the second wafer 22 is provided with a second channel, with the first channel and the second channel connected to form the first groove 3; the first through hole 4 is provided on the first wafer 22.

[0039] In this design, the first wafer 21 includes a rectangular body 211 and a trapezoidal frustum 212 with trapezoidal surfaces on all four sides. The lower end face of the rectangular body 211 is connected to the upper end face of the trapezoidal frustum 212. A first through hole is provided in the middle of the rectangular body 211, and a second through hole is provided in the middle of the trapezoidal frustum 212. The first through hole and the second through hole are connected to form the second through hole 6. The trapezoidal angle of the trapezoidal surface of the trapezoidal frustum 212 is 45 degrees, and the narrow end extends away from the body. The second through hole is located in the middle of the trapezoidal frustum 212. With this design, the trapezoidal frustum 212 structure makes it easy for the operator to identify the current position of the first through hole and to locate the adhesive dots. It should be noted that the trapezoidal frustum 212 can be formed by side etching technology in etching. Side etching technology refers to the etching of the side of the material by the etchant. This technology is often used in the fabrication of... The formation of the trapezoidal frustum 212, which has a specific shape and depth, utilizes the characteristics of lateral etching. By controlling the time and degree of etching, the material is gradually etched in a specific direction to form the structure of the trapezoidal frustum 212. Transforming the negative effects of lateral etching into a frustum forming process requires precise process control and design. This involves selecting appropriate etchants, controlling reaction conditions such as temperature, concentration, and time, and pre-designing the required frustum shape. By precisely controlling these factors, the impact of lateral etching can be minimized, ensuring that the formation of the trapezoidal frustum 212 meets the design requirements. This lateral etching process design is highly ingenious, not only overcoming the effects of lateral etching in traditional etching processes but also transforming this negative effect into a practical frustum forming process. The process design is ingenious.

[0040] In this scheme, the flow sensing unit 8 includes a first resistive film 81, a heating resistive film 82, and a second resistive film 83. The first resistive film 81 and the second resistive film 83 are disposed on both sides of the heating resistive film 82. The heating resistive film 82 heats up the first resistive film 81 and the second resistive film 83 on both sides of it through heat conduction.

[0041] When no fluid flows through the microfluidic channel 7, the temperatures of the first resistive membrane 81 and the second resistive membrane 83 are the same. When fluid flows through the microfluidic channel 7, heat transfer occurs in the first resistive membrane 81, the heating resistive membrane 82, and the second resistive membrane 83 along the fluid flow direction. The first resistive membrane 81, which comes into contact with the fluid first, cools down. The second resistive membrane 83, which comes into contact with the fluid later, experiences heat transfer from the heating resistive membrane 82 in the middle, causing the second resistive membrane 83 to heat up. A temperature difference is generated between the first resistive membrane 81 and the second resistive membrane 83. Based on this temperature difference, the flow rate is calculated using a flow rate calculation formula to convert the temperature difference into the flow rate of the fluid.

[0042] In this embodiment, a microfluidic device is constructed by bonding a first substrate and a second substrate together, so that the first groove and the second groove are closed to form a microfluidic channel for fluid movement. The bonding process improves the sealing performance of the microfluidic channel. A flow sensing unit is provided in the microfluidic channel to improve the detection accuracy of the fluid. By combining the micro-machining of the microfluidic channel with the flow sensing unit, the flexibility and accuracy of fluid control are improved, and the device structure is effectively simplified.

[0043] Example 2

[0044] See Figure 5 The number of the first perforations 4 is two sets, with the two sets of first perforations 4 respectively connected to the two ends of the first groove 3, and the second perforation 6 connected to the middle position of the second groove 5; wherein the number of the flow sensing units 8 is two sets, respectively disposed on both sides of the center of the microfluidic channel 7, and the flow sensing unit 8 includes a first resistive film 81, a heating resistive film 82 and a second resistive film 83, the first resistive film 81 and the second resistive film 83 are disposed on both sides of the heating resistive film 82, and the heating resistive film 82 heats up the first resistive film 81 and the second resistive film 83 on both sides of it through heat conduction; the purpose is to realize that the fluid is forked into the two sets of first perforations 4 respectively, and enters the microfluidic channel 7 from the two sets of first perforations 4, increasing the flow rate of the input fluid in the microfluidic channel 7. Using two sets of first perforations 4, when fluid is injected into one set of first perforations 4 and fluid blockage occurs in the first perforation 4, the other set of first perforations 4 can still Fluid can be injected normally and flow into the microfluidic channel 7, avoiding the inability to continue feeding fluid into the microfluidic channel 7 after a single input failure, while improving fluid input efficiency. Then, when there is no blockage in the two sets of first perforations 4, fluid is input into the microfluidic channel 7 from the two sets of first perforations 4. The fluid input from both sides of the microfluidic channel 7 flows into the flow sensing units 8 on both sides of the center of the microfluidic channel 7. The flow sensing units 8 detect the flow rate of the fluid flowing through them and determine whether the flow rate is greater than the control threshold. If so, the injection of fluid from the two sets of first perforations 4 is stopped, and the fluid stops flowing in the microfluidic channel 7. If not, the fluid continues to flow in the microfluidic channel 7, and the fluid flowing in the microfluidic channel 7 drips from the second perforation 6 onto the preset workpiece below the second perforation 6, thus realizing the centralized output of the second perforation 6 and improving fluid input efficiency.

[0045] Example 3

[0046] See Figure 6The second perforation 6 is in two sets, with each set connected to one end of the second groove 5. The first perforation 4 is connected to the middle of the first groove 5. The flow sensing unit 8 is in two sets, respectively disposed on both sides of the center of the microfluidic channel 7. Each flow sensing unit 8 includes a first resistive membrane 81, a heating resistive membrane 82, and a second resistive membrane 83. The first resistive membrane 81 and the second resistive membrane 83 are disposed on both sides of the heating resistive membrane 82. The heating resistive membrane 82 heats up the first resistive membrane 81 and the second resistive membrane 83 on both sides through thermal conduction. The purpose is to achieve concentrated fluid input into the first perforation 4, from the first perforation 4 into the microfluidic channel 7, and then through the flow sensing units 8 on both sides of the center of the microfluidic channel 7. The flow sensing unit 8 detects the flow... The flow rate of the fluid is measured by the flow sensing unit 8, and it is determined whether the flow rate of the fluid is greater than a preset threshold. If so, the injection of fluid from the first perforation 4 is stopped, and the fluid stops flowing in the microfluidic channel 7. If not, the fluid continues to flow in the microfluidic channel 7, and the fluid flowing in the microfluidic channel 7 drips from the two sets of second perforations 6 onto a preset workpiece below the second perforations 6. This increases the output fluid flow rate of the microfluidic channel 7. By using two sets of second perforations 6, when the fluid cannot be output from one set of second perforations 6, the other set of second perforations 6 can still output fluid normally. This avoids the situation where the fluid cannot be output from the microfluidic channel 7 after a single output fails, and at the same time improves the fluid output efficiency. That is, it realizes the forked output of the second perforations 6 and improves the fluid output efficiency.

[0047] Example 4

[0048] This embodiment also proposes a control method for a microfluidic device based on wafer bonding. In this embodiment, the control method is used in the dispensing process. See [link to relevant documentation]. Figure 7 This includes the following steps:

[0049] S1. Driving fluid is injected from the first perforation 4 in the first substrate 1;

[0050] S2. The fluid injected into the first perforation 4 flows through the flow sensing unit 8 in the microfluidic channel 7, and the flow rate of the fluid flowing through the flow sensing unit 8 is detected by the flow sensing unit 8.

[0051] In S2, the flow sensing unit 8 includes a first resistive membrane 81, a heating resistive membrane 82, and a second resistive membrane 83. The first resistive membrane 81 and the second resistive membrane 83 are disposed on both sides of the heating resistive membrane 82. The heating resistive membrane 82 heats up the first resistive membrane 81 and the second resistive membrane 83 on both sides through heat conduction. When no fluid passes through the microfluidic channel 7, the temperatures of the first resistive membrane 81 and the second resistive membrane 83 are the same. When fluid passes through the microfluidic channel 7, heat transfer occurs in the first resistive membrane 81, the heating resistive membrane 82, and the second resistive membrane 83 along the fluid flow direction. The first resistive membrane 81, which comes into contact with the fluid first, cools down. The second resistive membrane 83, which comes into contact with the fluid later, heats up due to the heat transfer from the heating resistive membrane 82 in the middle driven by the fluid. A temperature difference is generated between the first resistive membrane 81 and the second resistive membrane 83. Based on this temperature difference, the flow rate calculation formula is used to convert the temperature difference into the flow rate of the fluid.

[0052] S3. Determine whether the flow rate of the fluid is greater than the dispensing threshold. If yes, stop the fluid from being injected from the first perforation 4 in the first substrate 1, so that the fluid stops flowing in the microfluidic channel 7. If no, the fluid continues to flow in the microfluidic channel 7, and proceed to step S4.

[0053] S4. The fluid flowing in the microfluidic channel 7 is dripped from the second perforation 6 in the second substrate 2 onto the adhesive material to be applied below the second perforation 6.

[0054] In this embodiment, a microfluidic device is constructed by bonding an upper wafer and a lower wafer. After the upper wafer and the lower wafer are bonded together, a microchannel is formed by the first groove of the upper wafer and the second groove of the lower wafer, through which fluid passes and is provided with the first resistive film and the second resistive film. The microchannel can enhance the dispensing flexibility of the microfluidic device, effectively simplify the device structure, and improve the accurate detection and control of the fluid in the microchannel.

[0055] The same or similar labels correspond to the same or similar parts;

[0056] The terms used to describe positional relationships in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0057] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A microfluidic device based on wafer bonding, characterized in that, include: A first substrate (1) and a second substrate (2) are provided. A first groove (3) is formed on one set of end faces of the first substrate (1), and a first through hole (4) is provided on the other set of end faces of the first substrate (1) to connect the first groove (3). A second groove (5) is formed on one set of end faces of the second substrate (2), and a second through hole (6) is provided on the other set of end faces of the second substrate (2) to connect the second groove (5). The first substrate (1) and the second substrate (2) are connected by a bonding process, so that the first groove (3) and the second groove (5) are closed to form a microfluidic channel (7) for fluid movement. The first through hole (4) and the second through hole (6) are located at both ends of the microfluidic channel (7), and a flow sensing unit (8) is provided inside the microfluidic channel (7). The flow sensing unit (8) includes a first resistive film (81), a heating resistive film (82), and a second resistive film (83). The first resistive film (81) and the second resistive film (83) are disposed on both sides of the heating resistive film (82). The heating resistive film (82) heats up the first resistive film (81) and the second resistive film (83) on both sides of it through heat conduction.

2. The microfluidic device based on wafer bonding according to claim 1, characterized in that, The first groove (3) and the first perforation (4) are formed on two sets of opposite end faces of the first base (1); the second groove (5) and the second perforation (6) are formed on two sets of opposite end faces of the second base (2), and the first groove (3) and the second groove (5) have the same size specifications.

3. The microfluidic device based on wafer bonding according to claim 1, characterized in that, The first perforation (4) and the second perforation (6) are symmetrically distributed at 180° with the middle position of the microfluidic channel (7) as the center.

4. The microfluidic device based on wafer bonding according to claim 1, characterized in that, The second substrate (2) includes a first wafer (21) and a second wafer (22), one side of the first wafer (21) is connected to one side of the second wafer (22); the lower end face of the first wafer (21) is provided with a first channel, the lower end face of the second wafer (22) is provided with a second channel, and the first channel and the second channel are connected to form the first groove (3); the first through hole (4) is disposed on the second wafer (22).

5. The microfluidic device based on wafer bonding according to claim 4, characterized in that, The first wafer (21) includes a rectangular body (211) and a trapezoidal frustum (212) with trapezoidal surfaces on all four sides. The lower end face of the rectangular body (211) is connected to the upper end face of the trapezoidal frustum (212). A first through hole is provided in the middle of the rectangular body (211), and a second through hole is provided in the middle of the trapezoidal frustum (212). The first through hole and the second through hole are connected to form the second through hole (6).

6. The microfluidic device based on wafer bonding according to claim 5, characterized in that, The trapezoidal angle of the trapezoidal surface of the trapezoidal frustum (212) is 45 degrees.

7. The microfluidic device based on wafer bonding according to claim 1, characterized in that, The number of the first perforation (4) is two sets, and the two sets of the first perforation (4) are respectively connected to the two ends of the first groove (3), and the second perforation (6) is connected to the middle position of the second groove (5); Alternatively, there may be two sets of the second perforations (6), with the two sets of the second perforations (6) connected to the two ends of the second groove (5) respectively, and the first perforation (4) connected to the middle position of the first groove (3).

8. A control method for a microfluidic device based on wafer bonding as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Driving fluid is injected from the first perforation (4) in the first substrate (1); S2. The fluid injected into the first perforation (4) flows through the flow sensing unit (8) in the microfluidic channel (7), and the flow rate of the fluid flowing through the flow sensing unit (8) is detected by the flow sensing unit (8); S3. Determine whether the flow rate of the fluid is greater than a preset threshold. If yes, stop the fluid from being injected through the first perforation (4) in the first substrate (1) so that the fluid stops flowing in the microfluidic channel (7). If no, the fluid continues to flow in the microfluidic channel (7) and step S4 is executed. S4. The fluid flowing in the microfluidic channel (7) is dripped from the second perforation (6) in the second substrate (2) onto the preset workpiece below the second perforation (6).

9. The control method for a microfluidic device based on wafer bonding according to claim 8, characterized in that, When no fluid passes through the microfluidic channel (7), the temperatures of the first resistive membrane (81) and the second resistive membrane (83) are the same. When fluid passes through the microfluidic channel (7), heat transfer occurs in the first resistive membrane (81), the heating resistive membrane (82), and the second resistive membrane (83) along the fluid flow direction. The first resistive membrane (81), which comes into contact with the fluid first, cools down. The second resistive membrane (83), which comes into contact with the fluid later, experiences heat transfer from the heating resistive membrane (82) in the middle, driven by the fluid. This results in a temperature difference between the first resistive membrane (81) and the second resistive membrane (83). Based on this temperature difference, the flow rate is calculated using a flow rate calculation formula to convert the temperature difference into the flow rate of the fluid.

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