Trace formaldehyde detection chip, device and method based on microfluidic technology

Abstract

The application provides a trace formaldehyde detection chip, device and method based on microfluidic technology. In the trace formaldehyde detection chip, the first liquid inlet flow channel is in communication with a plurality of reaction micro-flow channels, ensuring stable introduction and uniform distribution of reagents, and cooperating with the communication design of the gas flow channel and the reaction micro-flow channel to allow formaldehyde and formaldehyde detection reagents to fully contact; the multi-thread design of the plurality of reaction micro-flow channels increases the contact opportunity, overcomes the problem of insufficient reaction, realizes trace level detection precision, accurately controls the amount of reagent, reduces the cost and waste liquid pressure. At the same time, the chip integrates all detection links, without complicated steps, simplifies the operation and can be automated, reduces labor cost, and the closed flow channel system can also reduce the interference of external temperature and humidity, and takes into account the detection accuracy, low cost and convenience.

Description

Technical Field

[0001] This application belongs to the field of formaldehyde detection, and more specifically, relates to a trace formaldehyde detection chip, device and method. Background Technology

[0002] Formaldehyde is a common indoor air pollutant with a pungent odor that poses serious health risks. Long-term exposure can lead to respiratory illnesses and even cancer. Therefore, detecting formaldehyde concentration is crucial for ensuring indoor air quality and protecting human health. Currently, existing formaldehyde detection technologies face the challenge of achieving both low cost and high accuracy simultaneously. Summary of the Invention

[0003] The purpose of this application is to provide a trace formaldehyde detection chip, device and method based on microfluidic technology, so as to solve the technical problem that it is difficult to achieve both low cost and high accuracy in formaldehyde detection in the prior art.

[0004] To achieve the above objectives, the technical solution adopted in this application is: to provide a trace formaldehyde detection chip based on microfluidic technology, the trace formaldehyde detection chip based on microfluidic technology comprising:

[0005] First liquid inlet channel; The first liquid inlet channel is provided with a first liquid inlet for introducing formaldehyde detection reagent;

[0006] Multiple reaction microchannels; all of the multiple reaction microchannels are connected to the first liquid inlet channel, so that the formaldehyde detection reagent is diverted from the first liquid inlet channel to the multiple reaction microchannels;

[0007] Gas flow channel; the gas flow channel is provided with a first vent and a second vent. One of the first vent and the second vent is used to introduce the gas to be detected, and the other is used to discharge the gas after the reaction. The gas flow channel is connected to multiple reaction microchannels so that the formaldehyde in the gas to be detected and the formaldehyde detection reagent in the multiple reaction microchannels can come into contact and react.

[0008] The detection channel is connected to multiple reaction microchannels, and a detection instrument is installed on the detection channel to detect the formaldehyde detection reagent and the reaction products of formaldehyde.

[0009] Optionally, a connecting space is formed at the junction of the gas channel and the reaction microchannel, with the reaction microchannel located in the lower part of the connecting space and the gas channel located in the upper part of the connecting space.

[0010] Optionally, the trace formaldehyde detection chip includes a base plate and a top plate. A first groove is formed on the base plate to form a reaction microchannel, and a second groove is formed on the top plate to form a gas channel. The top plate covers the base plate so that the gas channel is located above the reaction microchannel.

[0011] Optionally, multiple reaction microchannels extend along a first direction, and gas channels extend along a second direction, with the first and second directions intersecting to connect the gas channels and the multiple reaction microchannels.

[0012] Optionally, a first vent pipe and a second vent pipe are respectively provided on both sides of the top plate. The first vent pipe has a first through hole and a first closed part, and the second vent pipe has a second through hole and a second closed part.

[0013] The first through hole is opposite to the top plate, and the first vent is located in the first through hole; the second through hole is opposite to the top plate, and the second vent is located in the second through hole.

[0014] The first and second sealing parts are positioned opposite the base plate so that the base plate is positioned between the first and second sealing parts on both sides.

[0015] Optionally, an expansion cavity is provided at each end of the gas flow channel, and the gas flow channel is connected to the first vent and the second vent through the expansion cavities at both ends, respectively.

[0016] Optionally, the trace formaldehyde detection chip also includes a second liquid inlet channel, which is provided with a second inlet for introducing a colorant, and the second liquid inlet channel is connected between the reaction microchannel and the detection channel.

[0017] Optionally, the trace formaldehyde detection chip also includes a coloring channel, which is connected between the second liquid inlet channel and the detection channel, and the coloring channel is arranged in a serpentine pattern.

[0018] Optionally, a mixing chamber is provided between the second inlet channel and the reaction microchannel to mix the fluids of the multiple reaction microchannels with the colorant of the second inlet channel in the mixing chamber.

[0019] Optionally, the trace formaldehyde detection chip also includes an exhaust channel connected above the mixing chamber for discharging the gas collected in the upper part of the mixing chamber.

[0020] Optionally, the detection instrument includes an ultraviolet light source and an optical probe. The ultraviolet light source is used to emit ultraviolet light into the detection channel, and the optical probe is used to receive the optical signal fed back by the fluid in the detection channel to detect the product after coloring with the colorant.

[0021] This application also provides a formaldehyde detection device, which includes the aforementioned trace formaldehyde detection chip based on microfluidic technology.

[0022] Optionally, the formaldehyde detection device also includes an airflow circulation drive and a buffer chamber;

[0023] One end of the airflow circulation drive is connected to the buffer chamber, and the other end is connected to the first vent. The second vent is also connected to the buffer chamber.

[0024] Optionally, the formaldehyde detection device includes a carrier, on which a trace formaldehyde detection chip is disposed;

[0025] The carrier is equipped with a heating mechanism, and the trace formaldehyde detection chip is equipped with a temperature measuring element for detecting the temperature of the trace formaldehyde detection chip. The heating mechanism is configured to heat the trace formaldehyde detection chip based on the temperature measured by the temperature measuring element.

[0026] This application also provides a formaldehyde detection method, which employs the aforementioned trace formaldehyde detection chip based on microfluidic technology. The formaldehyde detection method includes:

[0027] Formaldehyde detection reagent is introduced into the first liquid inlet channel so that the formaldehyde detection reagent enters multiple reaction microchannels;

[0028] The gas to be tested is introduced into the first vent and the gas after reaction is discharged from the second vent, so that the formaldehyde in the gas to be tested reacts with the formaldehyde detection reagent in multiple reaction microchannels and the reaction products of the formaldehyde detection reagent and formaldehyde enter the detection channel.

[0029] The formaldehyde concentration in the gas to be tested is obtained by detecting the reaction products in the detection channel using a detection instrument.

[0030] Optionally, after introducing the gas to be tested into the first vent and exiting the reacted gas through the second vent, the formaldehyde detection method further includes:

[0031] The reacted gas discharged through the second vent is introduced into the buffer chamber;

[0032] The gas in the buffer chamber is re-introduced into the first vent as the gas to be tested through the airflow circulation drive.

[0033] Optionally, after introducing the gas to be tested into the first vent and exiting the reacted gas through the second vent, the formaldehyde detection method further includes:

[0034] Stop introducing the gas to be tested into the first vent.

[0035] The gas to be tested is introduced into the second vent, and the gas after reaction is discharged from the first vent.

[0036] The beneficial effects of the trace formaldehyde detection chip, device, and method based on microfluidics technology provided in this application are as follows: Compared with the prior art, in the trace formaldehyde detection chip of this application, the first liquid inlet channel is connected to multiple reaction microchannels to ensure stable reagent introduction and uniform distribution. Combined with the connection design between the gas channel and the reaction microchannels, this allows for full contact between formaldehyde and the formaldehyde detection reagent. The multi-threaded design of the multiple reaction microchannels increases contact opportunities, overcomes the problem of incomplete reaction, achieves trace-level detection accuracy, and precisely controls reagent dosage, reducing cost and waste liquid pressure. Simultaneously, the chip integrates the entire detection process, eliminating cumbersome steps, simplifying and automating operation, reducing labor costs. The closed-channel system also reduces interference from external temperature and humidity, balancing detection accuracy, low cost, and convenience. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the trace formaldehyde detection chip in the embodiments of this application;

[0039] Figure 2 This is an explosion diagram of the trace formaldehyde detection chip in the embodiments of this application;

[0040] Figure 3 This is a schematic diagram of the base plate of the trace formaldehyde detection chip in the embodiments of this application;

[0041] Figure 4 This is a schematic diagram of the top plate of the trace formaldehyde detection chip in the embodiments of this application;

[0042] Figure 5 for Figure 4 Enlarged view of point A in the middle;

[0043] Figure 6 for Figure 4 Enlarged view of point B in the middle;

[0044] Figure 7 This is a schematic diagram of the formaldehyde detection device in the embodiments of this application;

[0045] Figure 8 This is an explosion diagram of the formaldehyde detection device in the embodiments of this application;

[0046] Figure 9 This is a flowchart illustrating the formaldehyde detection method in the embodiments of this application.

[0047] In the figure, the following labels are used: Trace formaldehyde detection chip 100; Top plate 10; Bottom plate 20; First liquid inlet channel 11; First liquid inlet 111; Reaction microchannel 12; Gas channel 13; First vent 131; Second vent 132; First vent pipe 133; First through hole 1331; First sealing part 1332; Second vent pipe 134; Second through hole 1341; Second sealing part 1342; Enlarged cavity 135; Detection channel 14; Detection instrument 141; Second liquid inlet channel 15; Second liquid inlet 151; Coloring channel 16; Mixing chamber 17; Exhaust channel 171; Airflow circulation drive 30; Buffer chamber 40; Support 50; First direction a; Second direction b. Detailed Implementation

[0048] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0049] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0050] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0051] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0052] Currently, existing formaldehyde detection technologies generally suffer from a trade-off between low cost and high accuracy. Low-cost detection technologies, such as sensor technology and desiccator methods, have high detection limits and are easily affected by environmental factors such as temperature, humidity, and other indoor volatile organic compounds (VOCs), resulting in insufficient accuracy and sensitivity, and poor long-term stability. For example, semiconductor gas sensors rely on changes in conductivity caused by the adsorption of gas molecules on the surface of metal oxides. However, their response to formaldehyde is not specific; various VOCs, such as ethanol and toluene, can also elicit similar signals, leading to severe cross-interference and extremely poor selectivity. Furthermore, their detection limits are typically high (often above 0.1 mg / m³), approaching or exceeding indoor safety standards (0.07-0.08 mg / m³), thus failing to effectively distinguish and quantify trace amounts of formaldehyde within safe limits. Fluctuations in ambient temperature and humidity also cause significant reading drift, resulting in insufficient long-term stability.

[0053] High-precision detection technologies, such as spectroscopy and chromatography, often require complex sample pretreatment procedures, making the detection process complex and demanding expensive precision instruments. Take the DNPH tube coupled with liquid chromatography for formaldehyde determination as an example: A sampling tube coated with DNPH (2,4-dinitrophenylhydrazine) is used to collect a certain volume of air sample via a sampling pump. Formaldehyde in the sample undergoes a derivatization reaction with DNPH under acidic conditions, generating a 2,4-dinitrophenylhydrazone derivative. This derivative is then extracted from the sampling tube into an organic solvent (acetonitrile or methanol), and after centrifugation and filtration, a liquid sample is obtained. Finally, a high-performance liquid chromatograph (HPLC) with an ultraviolet detector (UVD) or a diode array detector (DAD) is used to effectively separate and detect the derivative. This method requires consumables such as DNPH tubes and expensive precision instruments like HPLC.

[0054] While the DNPH tube coupled with liquid chromatography (HPLC) method allows for the quantitative detection of formaldehyde concentration in the gas phase, it suffers from several drawbacks: Complex pretreatment steps: It requires sampling tube enrichment, strong acid-catalyzed derivatization (e.g., a 20-minute reaction in a 60°C water bath), and organic solvent extraction (e.g., elution with cyclohexane or acetonitrile), making the process cumbersome and time-consuming; High environmental control requirements: The derivatization reaction is sensitive to temperature, humidity, and pH, necessitating operation in a temperature- and humidity-controlled laboratory. Temperature fluctuations significantly reduce derivatization efficiency; High equipment and actual costs: High-performance liquid chromatography (HPLC) instruments typically cost between 500,000 and 2 million RMB, and the accompanying ultraviolet (UV) detector or diode array detector (DAD) requires regular replacement of the UV bulb (approximately 30,000 RMB per replacement). DNPH reagents and organic solvents such as acetonitrile are also expensive. Based on testing 20 samples per day, the daily reagent consumption is approximately 1200 yuan; the accuracy of the test results is low: VOCs such as benzene series compounds and ketone compounds may compete with formaldehyde for DNPH, leading to false positives and reducing the accuracy of formaldehyde concentration detection.

[0055] Therefore, there is an urgent need to develop a formaldehyde detection technology that is easy to operate and balances sensitivity and accuracy. Based on this, this application provides a trace formaldehyde detection chip 100, please refer to [link to relevant documentation]. Figure 1 , Figure 2 , Figure 3 and Figure 4 The trace formaldehyde detection chip 100 based on microfluidic technology includes:

[0056] First liquid inlet channel 11; The first liquid inlet channel 11 is provided with a first liquid inlet 111 for introducing formaldehyde detection reagent;

[0057] Multiple reaction microchannels 12; all of the multiple reaction microchannels 12 are connected to the first liquid inlet channel 11, so that the formaldehyde detection reagent is diverted from the first liquid inlet channel 11 to the multiple reaction microchannels 12;

[0058] Gas flow channel 13; Gas flow channel 13 is provided with a first vent 131 and a second vent 132. One of the first vent 131 and the second vent 132 is used to introduce the gas to be detected, and the other is used to discharge the gas after the reaction. Gas flow channel 13 is connected to multiple reaction microchannels 12 so that the formaldehyde in the gas to be detected and the formaldehyde detection reagent in the multiple reaction microchannels 12 come into contact and react.

[0059] The detection channel 14 is connected to multiple reaction microchannels 12. A detection instrument 141 is installed on the detection channel 14 to detect the formaldehyde detection reagent and the reaction products of formaldehyde.

[0060] The first liquid inlet channel 11 is equipped with a dedicated first liquid inlet 111, which is used to introduce formaldehyde detection reagent. The first liquid inlet channel 11 is a dedicated channel for formaldehyde detection reagent to enter the chip system, which can ensure that the reagent flows into the subsequent reaction stage in a stable and uniform state, laying the foundation for the full reaction between formaldehyde and reagent, and avoiding the impact of unstable reagent introduction on the test results.

[0061] Multiple reaction microchannels 12 are connected to the first inlet channel 11. Formaldehyde detection reagent flowing in from the first inlet channel 11 can be evenly distributed into each of the multiple reaction microchannels 12 through this connection structure. The reaction microchannels 12 refer to micron-level reaction channels. These multiple reaction microchannels 12 are the main sites for the reaction between formaldehyde and the detection reagent. The multi-channel setup ensures the synchronicity of the reaction and provides structural support for improving the reliability of subsequent detection.

[0062] The gas flow channel 13 is equipped with two vents, namely a first vent 131 and a second vent 132. Their functions can be flexibly allocated; one is used to introduce the gas to be detected, while the other is used to exhaust the gas after the reaction. There are no fixed restrictions on gas inlet or outlet. The gas flow channel 13 is also interconnected with multiple reaction microchannels 12. Formaldehyde in the gas to be detected can contact and react with the formaldehyde detection reagents within the multiple reaction microchannels 12 through this interconnection structure, creating the necessary conditions for formaldehyde to transfer from the gas phase to the liquid phase.

[0063] Multiple reaction microchannels 12 are connected to the detection channel 14. The reaction products generated in each reaction microchannel 12 can be collected and gathered into the detection channel 14 through this connection structure. A detection instrument 141 is specially installed on the detection channel 14. The detection instrument 141 is used to detect the products generated by the reaction of formaldehyde with formaldehyde detection reagent. The concentration of formaldehyde in the gas to be tested is then calculated based on the detection results, completing the final data output of the entire detection process.

[0064] When the detection chip is working, the formaldehyde detection reagent enters the system through the first inlet 111 of the first liquid inlet channel 11, and is then evenly distributed into multiple reaction microchannels 12. The gas to be detected is introduced from one of the vents of the gas channel 13. In the region where the gas channel 13 connects with the multiple reaction microchannels 12, the formaldehyde molecules in the gas come into full contact with the formaldehyde detection reagent in the multiple reaction microchannels 12 and undergo a specific reaction. After the reaction is completed, the remaining gas is discharged from another vent, and the generated reaction products are collected into the detection channel 14 through the connecting structure. Finally, the detection instrument 141 on the detection channel 14 detects the products and calculates the concentration of formaldehyde in the gas to be detected based on the detection data, thus completing the entire detection process.

[0065] This trace formaldehyde detection chip 100 employs a multi-threaded design with multiple reaction microchannels 12. The gas to be detected is diverted into multiple independent channels, allowing formaldehyde molecules to simultaneously contact and react with the formaldehyde detection reagent. Compared to a single-channel structure, this design significantly increases the effective contact opportunities between formaldehyde molecules and the reagent, effectively overcoming the problem of incomplete reaction caused by uneven local gas concentrations and ensuring a more thorough reaction. This key design provides core support for significantly improving detection accuracy, ultimately enabling the sensor to stably achieve trace-level (i.e., one part per billion) formaldehyde detection accuracy. Simultaneously, each reaction microchannel 12 requires only a trace amount of reagent to meet the reaction requirements. The multi-channel diversion design allows for precise control of the overall reagent consumption, significantly reducing reagent usage compared to the large amounts consumed in traditional detection methods, thus reducing costs and the pressure on waste liquid treatment.

[0066] The trace formaldehyde detection chip 100 integrates the entire process of reagent introduction into gas contact reaction product detection into one unit. Unlike traditional high-precision detection methods such as DNPH tube coupled with liquid chromatography, it eliminates the need for cumbersome steps such as separate sampling tube enrichment, water bath derivatization, centrifugation, and filtration. The operation process is greatly simplified and can be automated, reducing labor costs. In addition, the trace reagent consumption characteristics of multiple reaction microchannels 12 and the integration of the detection instrument 141 into the detection channel 14 eliminate the need for large and expensive equipment such as high-performance liquid chromatographs. The reagent consumption cost and equipment purchase and maintenance cost can be significantly reduced, resulting in a clear overall cost advantage.

[0067] The reagents in the closed flow channel system move within the first liquid inlet flow channel 11, multiple reaction microchannels 12 and detection flow channel 14, while the gas moves within the gas flow channel 13. This reduces the impact of external temperature and humidity fluctuations on the reaction, and changes in the external environment are unlikely to directly interfere with the reaction system within the flow channel.

[0068] In some embodiments of this application, a connection space is formed at the junction of the gas channel 13 and the reaction microchannel 12, with the reaction microchannel 12 located in the lower part of the connection space and the gas channel 13 located in the upper part of the connection space.

[0069] After the gas to be detected is introduced into the upper gas channel 13, it first fills the upper area of ​​the connecting space. At this time, the reagents in the multiple reaction microchannels 12 at the bottom of the connecting space form a liquid interface. During this process of full contact between the gas and liquid interface, the connecting space acts as a buffer area, preventing the gas from rushing directly into the channel. Instead, it diffuses slowly within the space, and with the help of gravity, the formaldehyde molecules naturally move downwards to react with the reagents. This prolongs the gas residence time and makes the contact more uniform. For trace amounts of formaldehyde, the longer contact time reduces the amount of unreacted gas that may be drawn out due to excessive flow rate, and the more thorough reaction directly improves the detection accuracy. At the same time, the reagents accumulate at the bottom and the liquid surface is stable, preventing splashing to the upper area due to gas impact, thus avoiding ineffective losses. Furthermore, it eliminates the need to fill the entire connecting area. Combined with the trace requirements of multiple reaction microchannels 12, the amount of reagent can be more precisely controlled, significantly reducing costs.

[0070] After the reaction is complete, the unreacted gas is discharged from the upper gas channel 13, while the product remains in the multiple reaction microchannels 12 and is collected in the detection channel 14. The entire process is free from flow field disturbance. In addition, the transition design of the connecting space can also avoid damage to the multiple reaction microchannels 12 by gas pressure shocks and prevent reagent backflow from clogging the gas channel 13.

[0071] Please see Figure 2 , Figure 3 and Figure 4 In some embodiments of this application, the trace formaldehyde detection chip 100 includes a base plate 20 and a top plate 10. A first groove is formed on the base plate 20 to form a reaction microchannel 12, and a second groove is formed on the top plate 10 to form a gas channel 13. The top plate 10 covers the base plate 20 so that the gas channel 13 is located above the reaction microchannel 12.

[0072] The multiple reaction microchannels 12 formed by the first groove of the base plate 20 can stably contain the formaldehyde detection reagent. The groove structure can limit the flow range of the reagent and prevent it from spreading randomly. The gas channel 13 formed by the second groove of the top plate 10 is located above. After the gas to be detected is introduced into the gas channel 13, it can form a stable airflow path in the groove, directly covering the reagent in the multiple reaction microchannels 12 below. When the gas channel 13 and the multiple reaction microchannels 12 form a connection space, the gas channel 13 of the top plate 10 can smoothly introduce the gas into the upper part of the connection space, while the multiple reaction microchannels 12 of the base plate 20 stably confine the reagent in the lower part of the connection space. Formaldehyde molecules naturally diffuse downward into the reagent to react with gravity, without the need for additional structural guidance. In this process, the gas flows stably in the airflow path, and the reagent maintains a fixed range in the groove. The contact between the two is more sufficient, which can reduce the detection error caused by insufficient contact, especially for trace formaldehyde, and improve the detection accuracy.

[0073] The trace formaldehyde detection chip 100 constructs its core flow channel through a combination of a base plate 20 and a top plate 10. The base plate 20 is easy to process; multiple reaction microchannels 12 can be easily formed by simply creating a first groove, without complex processes. The top plate 10 has a second groove to form a gas flow channel 13, and after the top plate 10 covers the base plate 20, the gas flow channel 13 is naturally positioned above the multiple reaction microchannels 12. This split groove design allows both to be formed independently on their respective substrates, eliminating the need for complex groove cutting on a single substrate, significantly reducing the difficulty of chip manufacturing. At the same time, the assembly method of the top plate 10 and the base plate 20 can precisely ensure the vertical alignment of the flow channels, avoiding the positional offset problem of traditional integrated processing, laying the foundation for effective contact between gas and reagents.

[0074] The multiple reaction microchannels 12 of the base plate 20 stably contain the formaldehyde detection reagent through a groove structure, limiting the reagent's flow range and preventing random diffusion. After the gas to be detected is introduced into the gas channel 13 of the top plate 10, a stable airflow path is formed within the groove, directly covering the reagent below. When a connecting space is formed at the junction of the two, the gas enters the upper part of the connecting space from the gas channel 13 of the top plate 10, while the reagent is confined to the lower part. The formaldehyde molecules diffuse downwards naturally due to gravity, without the need for additional guidance.

[0075] Please see Figure 2 In some embodiments of this application, a plurality of reaction microchannels 12 extend along a first direction a, and a gas channel 13 extends along a second direction b. The first direction a and the second direction b intersect, so that the gas channel 13 and the plurality of reaction microchannels 12 are connected.

[0076] The trace formaldehyde detection chip 100 has multiple reaction microchannels 12 extending along a first direction a, and gas channels 13 extending along a second direction b, with the first direction a and the second direction b intersecting, allowing the gas channels 13 to form a cross-connection with the multiple reaction microchannels 12. Compared to a single connection point, multiple connection points can significantly increase the contact points between the gas and the reagent, allowing the gas to be detected to be more evenly distributed into each reaction microchannel 12, avoiding the problem of incomplete reaction caused by uneven gas distribution in some reaction microchannels 12. At the same time, the intersecting extension design does not require additional complex flow distribution structures; efficient connection between the gas channels 13 and multiple reaction microchannels 12 can be achieved simply by the intersection of directions, simplifying the flow channel layout and further reducing the design difficulty of the chip's internal structure.

[0077] Multiple reaction microchannels 12 extending along the first direction a provide a longer flow and reaction path for the formaldehyde detection reagent, allowing the reagent to flow smoothly within the extended channels and avoiding local accumulation. Gas channels 13 extending along the second direction b intersect with the multiple reaction microchannels 12. The gas to be detected is introduced through the gas channels 13 and comes into contact with the reagent within the reaction microchannels 12 at each intersection point. Because the intersection points are distributed along the extension direction of the reaction microchannels 12, the gas can gradually enter different locations within the reaction microchannels 12, rather than concentrating and rushing in at one point, reducing reagent flow field turbulence caused by gas impact. Especially when the first direction a and the second direction b intersect perpendicularly, the gas channels 13 can span multiple reaction microchannels 12 arranged along the first direction a, forming a transverse and longitudinal cross-connected structure, allowing the gas to contact the reagent over a wider range. For trace formaldehyde, more contact sites and more uniform gas distribution allow each formaldehyde molecule in the reaction microchannel 12 to have sufficient opportunity to react with the reagent, further reducing detection errors caused by uneven gas distribution and improving detection accuracy.

[0078] Please see Figure 4 , Figure 5 and Figure 6 In some embodiments of this application, a first vent pipe 133 and a second vent pipe 134 are respectively provided on both sides of the top plate 10. The first vent pipe 133 has a first through hole 1331 and a first closed part 1332, and the second vent pipe 134 has a second through hole 1341 and a second closed part 1342.

[0079] The first through hole 1331 is opposite to the top plate 10, and the first vent 131 is provided in the first through hole 1331. The second through hole 1341 is opposite to the top plate 10, and the second vent 132 is provided in the second through hole 1341.

[0080] The first sealing part 1332 and the second sealing part 1342 are positioned opposite to the base plate 20, so that the base plate 20 is positioned between the first sealing part 1332 and the second sealing part 1342 on both sides.

[0081] The first through-hole portion 1331 is positioned opposite to the top plate 10, and the first vent 131 is located within the first through-hole portion 1331. The second through-hole portion 1341 is positioned opposite to the top plate 10, and the second vent 132 is located within the second through-hole portion 1341. The gas to be detected can enter the first vent 131 through the first through-hole portion 1331 of the first vent pipe 133, and then flow into the gas flow channel 13 on the top plate 10. After the reaction, the gas exits from the gas flow channel 13 through the second vent 132 into the second through-hole portion 1341 of the second vent pipe 134, forming a complete and independent gas channel. Compared to directly opening a vent at the edge of the top plate 10, the through-hole portion of the vent pipe can extend the gas flow path, reduce the risk of gas leakage during the introduction and exit process, and at the same time allow for a more precise connection between the vent and the gas flow channel 13 on the top plate 10, avoiding airflow obstruction caused by opening position deviation.

[0082] The first sealing portion 1332 of the first vent pipe 133 and the second sealing portion 1342 of the second vent pipe 134 are positioned opposite to the base plate 20, and the base plate 20 is positioned between the first sealing portions 1332 and the second sealing portions 1342 on both sides. This design allows the base plate 20 to be assembled with the top plate 10 without the need for additional positioning clamps. The lateral movement of the base plate 20 can be restricted solely by the sealing portions of the vent pipes on both sides, ensuring that the multiple reaction microchannels 12 extending along the first direction a on the base plate 20 are precisely aligned with the gas channels 13 extending along the second direction b on the top plate 10.

[0083] This venting tube structure also enhances the overall practicality and ease of manufacturing of the trace formaldehyde detection chip 100. On one hand, the first venting tube 133 and the second venting tube 134 are set as independent components on both sides of the top plate 10, allowing for mass production using standardized molds. The diameters of the first through-hole 1331 and the second through-hole 1341, as well as the dimensions of the first sealing part 1332 and the second sealing part 1342, can be precisely controlled, ensuring consistent compatibility between each set of venting tubes and the top plate 10 and bottom plate 20. This reduces assembly errors caused by component differences and improves the consistency of mass production. On the other hand, the venting tubes simultaneously perform ventilation and positioning functions, eliminating the need for additional positioning structures or ventilation interfaces on the outside of the chip. This simplifies the overall chip structure layout. Especially when integrating the detection instrument 141 later, the presence of the venting tubes on both sides provides a clear interface for connecting the chip to the external gas path, facilitating quick connection of the gas path by operators and improving the convenience of the detection operation.

[0084] Please see Figure 5 and Figure 6 In some embodiments of this application, the gas flow channel 13 is provided with expansion cavities 135 at both ends, and the gas flow channel 13 is connected to the first vent 131 and the second vent 132 through the expansion cavities 135 at both ends.

[0085] The expansion cavity 135 allows the gas to be tested entering from the first vent 131 to be briefly buffered within the expansion cavity 135, preventing the gas from directly rushing into the narrow gas flow channel 13, which would cause a sudden increase in flow velocity and turbulent airflow. This allows the gas to flow more smoothly along the gas flow channel 13 and reach the connection point with the multiple reaction microchannels 12 evenly. After the reaction, the gas gathers in the expansion cavity 135 at the other end of the gas flow channel 13, and can also be buffered by the expansion cavity 135 before smoothly entering the second vent 132 for discharge, reducing gas flow resistance.

[0086] Please see Figure 2 and Figure 3 In some embodiments of this application, the trace formaldehyde detection chip 100 further includes a second liquid inlet channel 15, which is provided with a second liquid inlet 151 for introducing a colorant, and the second liquid inlet channel 15 is connected between the reaction microchannel 12 and the detection channel 14.

[0087] The trace formaldehyde detection chip 100 has a second liquid inlet 15 in its second liquid inlet channel 15, through which a colorant can be introduced. The second liquid inlet channel 15 is connected between the reaction microchannel 12 and the detection channel 14. After the colorant enters through the second liquid inlet channel 15, it can mix with the product generated by the reaction of formaldehyde in the reaction microchannel 12. If the product reacts with the colorant, the color change can visually reflect whether the reaction has occurred, making it easy to quickly determine whether the gas contains formaldehyde.

[0088] Taking the formaldehyde detection reagent using phenol and the colorant using ferric ammonium sulfate as an example, after the formaldehyde in the gas to be detected enters multiple reaction microchannels 12, it will react with the phenol reagent. The amino group in the phenol reagent can combine with the formaldehyde to form a azine compound. At this time, the ferric ammonium sulfate introduced through the second inlet 151 enters multiple reaction microchannels 12 through the second inlet channel 15. The ferric ions in the ferric ammonium sulfate will act as an oxidant and undergo a redox reaction with the azine compound to generate a blue-green indophenol blue substance. The blue-green indophenol blue product in the detection channel 14 can be accurately captured by the detection instrument 141. For example, by measuring the absorbance of the blue-green substance, based on the positive correlation between absorbance and indophenol blue concentration, and the positive correlation between indophenol blue concentration and formaldehyde concentration, the instrument can more accurately calculate the concentration of formaldehyde in the gas to be detected. Compared with the transparent product that may exist when there is no colorant, the blue-green signal is easier to identify, which can effectively reduce the detection error caused by low formaldehyde concentration and further improve the accuracy of trace formaldehyde detection.

[0089] Please see Figure 2 and Figure 3 The trace formaldehyde detection chip 100 also includes a coloring channel 16, which is connected between the second liquid inlet channel 15 and the detection channel 14, and the coloring channel 16 is arranged in a serpentine shape.

[0090] The coloring channel 16 is located between the second inlet channel 15 and the detection channel 14, and the coloring channel 16 is arranged in a serpentine pattern. The ferric ammonium sulfate colorant introduced through the second inlet channel 15, along with the reaction products of azircon compounds, formaldehyde, and phenol reagent flowing out from multiple reaction microchannels 12, will enter the coloring channel 16 together. The serpentine structure extends the flow path of the mixed fluid within the channel and generates slight turbulence at the bends, which can break up fluid stratification and allow the ferric ammonium sulfate and azircon compounds to come into more complete contact. This ensures that the ferric ions and azircon compounds undergo a complete redox reaction, generating a uniform blue-green indophenol blue substance. This avoids situations where there is no color development or uneven color development due to uneven mixing, thus improving the accuracy of detection visualization.

[0091] The serpentine coloring channel 16 slows down the flow rate of the mixed fluid, indophenol blue and ferric ammonium sulfate, preventing uneven product distribution caused by the fluid entering the detection channel 14 too quickly. Simultaneously, the extended channel length allows for more stable fluid flow, reducing product residue on the channel wall due to flow rate fluctuations, ensuring a smoother flow of more uniformly mixed product into the detection channel 14. Once in the detection channel 14, the uniform blue-green product allows the detection instrument 141 to capture a more stable absorbance signal. Based on the positive correlation between absorbance and formaldehyde concentration, the formaldehyde concentration can be calculated more accurately, further reducing detection errors caused by uneven mixing or residue, and improving the reliability of trace formaldehyde detection.

[0092] Please see Figure 2 and Figure 3 In some embodiments of this application, a mixing chamber 17 is provided between the second inlet channel 15 and the reaction microchannel 12 so that the fluids of the plurality of reaction microchannels 12 are mixed in the mixing chamber 17 before being mixed with the colorant of the second inlet channel 15.

[0093] The trace formaldehyde detection chip 100 has a mixing chamber 17 downstream of multiple reaction microchannels 12, and a second liquid inlet channel 15 is connected downstream of the mixing chamber 17. Within the multiple reaction microchannels 12, the products generated from the reaction of formaldehyde with the formaldehyde detection reagent flow into the mixing chamber 17 respectively. Utilizing the capacity of the mixing chamber 17, the multiple product streams can fully converge and eliminate concentration differences between individual streams, forming a uniformly composed overall product stream. This premixing step avoids color deviations caused by uneven local concentrations of the product when mixing with the colorant later, laying a stable material basis for the coloring reaction.

[0094] After the mixed product fluid flows out of the mixing chamber 17, it will meet and mix with the colorant introduced into the second inlet channel 15 downstream. This order of product premixing followed by colorant incorporation allows the colorant to be evenly dispersed in the homogenized product fluid, reducing the impact and stratification when the two are directly contacted. The evenly mixed product and colorant can smoothly enter the subsequent serpentine coloring channel 16. Relying on the extended path of the coloring channel 16 and the turbulence at the bend, the colorimetric reaction is further deepened, generating a uniformly colored product and improving the detection effect.

[0095] Please see Figure 2 In some embodiments of this application, the trace formaldehyde detection chip 100 further includes an exhaust channel 171, which is connected above the mixing chamber 17 and is used to discharge the gas collected in the upper part of the mixing chamber 17.

[0096] When the reaction products of formaldehyde and formaldehyde detection reagent in the multiple reaction microchannels 12 flow into the mixing chamber 17, they may carry trace amounts of gas (such as gas generated in the reaction or residual air in the channels). These gases tend to accumulate in the upper part of the mixing chamber 17 to form gas clouds. If the gas clouds accumulate, they will occupy the internal space of the mixing chamber 17, compress the area for containing the product fluid, and prevent multiple product fluids from fully diffusing and converging, making it difficult to form a uniform overall product fluid, which in turn affects the subsequent mixing effect with the colorant.

[0097] The exhaust channel 171, by venting the gas from the upper part of the mixing chamber 17, clears the gas clumps within the chamber, providing ample and complete mixing space for the product fluids. This allows multiple product fluids to fully contact each other, eliminating concentration differences and ensuring uniform composition of the premixed overall product fluid. Simultaneously, the presence of gas clumps can hinder the downstream flow of the product fluid from the mixing chamber 17, causing flow rate fluctuations or localized stagnation. Exhausting the gas through the exhaust channel 171 reduces fluid flow resistance, allowing the premixed overall product fluid to flow smoothly downstream and mix with the colorant in the second inlet channel 15, avoiding deviations in the colorant mixing ratio due to unstable flow rates.

[0098] Furthermore, the exhaust of gas from the upper part of the mixing chamber 17 prevents gas clouds from entering the subsequent serpentine coloring channel 16 or detection channel 14 with the fluid. If gas enters the coloring channel 16, it may form bubbles at the bends, interfering with the uniformity of the colorimetric reaction; if it enters the detection channel 14, the bubbles will affect the detection instrument 141's capture of the colorimetric product signal (e.g., by obstructing the optical signal), leading to detection errors. The exhaust channel 171 reduces such interference, further ensuring the accuracy and reliability of trace formaldehyde detection.

[0099] In some embodiments of this application, the detection instrument 141 includes an ultraviolet light source and an optical probe. The ultraviolet light source is used to emit ultraviolet light into the detection channel 14, and the optical probe is used to receive the optical signal fed back by the fluid in the detection channel 14 to detect the product after coloring with the colorant.

[0100] An ultraviolet (UV) light source is used to emit UV light into the detection channel 14. When the fluid fully reacts in the serpentine coloring channel 16, the coloring product formaldehyde reacts with the formaldehyde detection reagent to form a colorant, which then flows into the detection channel 14. UV light penetrates this coloring product. Different concentrations of the coloring product have different absorption capacities for specific wavelengths of UV light; the higher the concentration of the coloring product, the stronger the absorbed UV light and the weaker the transmitted light. This characteristic provides a direct basis for inferring the formaldehyde concentration from the optical signal. The optical probe is used to receive the optical signal fed back by the fluid in the detection channel 14, i.e., the UV light signal transmitted through the coloring product. It converts the optical signal into an electrical signal, processes the data to calculate the coloring product concentration, and then, based on the positive correlation between the coloring product concentration and the formaldehyde concentration, obtains the specific formaldehyde content in the gas to be detected.

[0101] The ultraviolet light source can be adjusted to match the characteristic absorption wavelength of the colored product, ensuring targeted detection of only the colored product and avoiding interference from unreacted formaldehyde detection reagents and other impurities on the optical signal, thus improving the specificity of the detection. The high-sensitivity design of the optical probe can capture the weak optical signal fed back by low concentrations of colored products. Even at extremely low formaldehyde concentrations, it can accurately identify the concentration of colored products through signal changes, making it suitable for trace formaldehyde detection scenarios and further ensuring the accuracy and applicability of the detection.

[0102] Please see Figure 7 Based on the trace formaldehyde detection chip 100 in the above embodiments, this application also provides a formaldehyde detection device, which includes the trace formaldehyde detection chip 100 in any of the above embodiments, and can realize accurate and low-cost detection of formaldehyde.

[0103] Please see Figure 1 , Figure 7 and Figure 8 In some embodiments of this application, the formaldehyde detection device further includes an airflow circulation drive 30 and a buffer chamber 40; one end of the airflow circulation drive 30 is connected to the buffer chamber 40, the other end is connected to the first vent 131, and the second vent 132 is connected to the buffer chamber 40.

[0104] One end of the airflow circulation drive 30 is connected to the buffer chamber 40, and the other end is connected to the first vent 131. The second vent 132 is also connected to the buffer chamber 40, forming a circulation path of buffer chamber 40, airflow circulation drive 30, first vent 131, gas flow channel 13, second vent 132, and buffer chamber 40. The airflow circulation drive 30 is usually an air pump or a micro fan, which can provide stable power to continuously push the gas to be detected in the buffer chamber 40 through the first vent 131 into the gas flow channel 13 of the trace formaldehyde detection chip 100, allowing the gas to repeatedly flow through multiple reaction microchannels 12 and come into contact with the formaldehyde detection reagent. Formaldehyde that does not fully react during the initial contact will flow back to the buffer chamber 40 with the gas, and then re-enter the gas flow channel 13 through circulation to come into contact with the formaldehyde detection reagent again. Through this cyclic contact process, the formaldehyde in the gas to be tested is more thoroughly reacted and absorbed, avoiding the omission of detection due to insufficient reaction in a single contact of low-concentration formaldehyde. It is especially suitable for the full reaction of low-concentration formaldehyde.

[0105] The buffer chamber 40 temporarily stores the gas to be detected, reducing flow rate fluctuations when the airflow circulation drive 30 directly supplies gas. This allows for a more stable gas flow rate entering the first vent 131, ensuring stable airflow within the gas channel 13 and preventing uneven gas distribution due to sudden changes in flow rate, such as insufficient gas in some reaction microchannels 12. Stable airflow ensures that the gas in each cycle is evenly distributed across multiple reaction microchannels 12, guaranteeing sufficient contact between the formaldehyde detection reagent and the gas, further promoting complete formaldehyde reaction and absorption. Simultaneously, unreacted gas flows back to the buffer chamber 40 through the second vent 132, re-entering the trace formaldehyde detection chip 100 for reaction. This improves gas utilization, reduces gas waste, and enhances formaldehyde conversion efficiency through multiple reactions, resulting in a final reaction product concentration that more closely matches the actual formaldehyde content. This leads to more accurate optical signals captured by the detection instrument 141, thereby improving detection precision and assisting the formaldehyde detection device in achieving more precise trace formaldehyde detection.

[0106] Based on the structural design of the formaldehyde detection device described above, the reaction process and color development process of gaseous formaldehyde and phenol reagent along the flow path can be simplified to a one-dimensional convective mass transfer model. The reaction kinetics process can also be used as a source and sink phase for comprehensive analysis of formaldehyde on the fluid side. Now, assuming that the fluid in the gas-liquid two-phase mixing section is fully mixed, the governing equations for the formaldehyde concentration on the fluid side in the microchannel and the aziridine compounds generated by the reaction with the phenol reagent are shown in equations (1) and (2).

[0107] (1)

[0108] (2)

[0109] in, C f (μg / mL)C p (μg / mL) and C t (μg / mL) represent the concentrations of formaldehyde, phenol reagent, and aziridine compounds on the fluid side, respectively. Since the consumption of phenol reagent is relatively small, C p It can be approximated as a constant; D w,f (cm) 2 / s) and D w,t (cm) 2 ( / s) represent the diffusion coefficients of formaldehyde and azircon compounds in aqueous solution, respectively; u 1 (cm / s) represents the fluid velocity in the microchannel of the gas-liquid two-phase mixing section; k 1 (ml / μg / s) is the reaction rate constant of the reaction between formaldehyde and phenol reagent. After the sample has fully reacted, the azine compound will react with the ferric ammonium sulfate chromogenic agent in the serpentine channel of the color development section to form an iron-azine complex for concentration detection by ultraviolet spectrophotometry. The control equations for the azine compound and the iron-azine complex in the color development section are shown in formulas (3) and (4).

[0110] (3)

[0111] (4)

[0112] in, C af (μg / mL) and C io (μg / mL) represent the concentrations of ferric ammonium sulfate and the iron-azine complex on the fluid side, respectively. Since the consumption of ferric ammonium sulfate as a colorimetric reagent is relatively small, C af It can be approximated as a constant; D w,io (cm) 2 / s) is the diffusion coefficient of the iron-azine complex in aqueous solution; u 2 (cm / s) represents the fluid velocity in the microchannel of the color development section; k 2 (ml / μg / s) is the reaction rate constant for the reaction between aziridine compounds and ferric ammonium sulfate colorimetric reagent.

[0113] From formulas (1) to (4), we can see that D w D, u, and k are all kinetic parameters that drive mass transfer and transformation on the fluid side, where D wk is strongly correlated with temperature. Based on this, in some embodiments of this application, the formaldehyde detection device includes a carrier 50, and a trace formaldehyde detection chip 100 is disposed on the carrier 50; a heating mechanism is disposed on the carrier 50, and the trace formaldehyde detection chip 100 is provided with a temperature measuring element for detecting the temperature of the trace formaldehyde detection chip 100; the heating mechanism is configured to heat the trace formaldehyde detection chip 100 based on the temperature measured by the temperature measuring element.

[0114] The temperature sensing element can detect the temperature of the trace formaldehyde detection chip 100 in real time and feed the temperature information back to the heating mechanism. When the chip temperature is detected to be lower than the suitable temperature required for the reaction between formaldehyde and the formaldehyde detection reagent, the heating mechanism will start and transfer heat to the carrier 50. The heat is conducted to the trace formaldehyde detection chip 100 through the carrier 50, gradually raising the chip temperature to the suitable range. When the temperature sensing element detects that the chip temperature has reached the suitable value, the heating mechanism will adjust the heating intensity or stop heating to avoid excessive temperature causing the formaldehyde detection reagent to fail or the reaction products to decompose, ensuring that the chip is always in a temperature environment conducive to the reaction. The heating mechanism can use an electric heating element, which can be used in conjunction with heat pipes, heat spreaders, and other components to evenly transfer heat to the trace formaldehyde detection chip 100.

[0115] A suitable temperature accelerates the reaction rate of formaldehyde and formaldehyde detection reagent within the multiple reaction microchannels 12, shortening the time required for the reaction to reach a sufficient state. This is especially beneficial for low-concentration formaldehyde, reducing the problem of excessively long detection times caused by slow reactions. Simultaneously, a stable temperature environment avoids differences in reaction efficiency due to temperature fluctuations. If the temperature is too low, the reaction may be incomplete, resulting in a lower concentration of the reaction product than the actual formaldehyde concentration; if the temperature is too high, side reactions may occur, generating interfering substances that affect the detection results. The heating mechanism achieves precise temperature control based on temperature feedback from the temperature sensing element, ensuring consistent reaction conditions for each test. This guarantees that the concentration of the generated reaction product accurately reflects the formaldehyde content in the gas being tested, making the optical signal captured by the subsequent detection instrument 141 more reliable and further improving the detection accuracy of the formaldehyde detection device.

[0116] Taking the color development of phenol reagent in combination with ferric ammonium sulfate as an example, the heating mechanism is usually not needed when the temperature is above 23℃, but can be activated when the temperature is below 23℃.

[0117] Based on the aforementioned trace formaldehyde detection chip 100, please refer to Figure 9 This application also provides a formaldehyde detection method, which includes:

[0118] S110. Formaldehyde detection reagent is introduced into the first inlet channel 11, allowing it to enter multiple reaction microchannels 12. When formaldehyde detection reagent is introduced into the first inlet channel 11, it naturally flows along the channel to the multiple reaction microchannels 12. The multiple reaction microchannels 12 of the trace formaldehyde detection chip 100 are branched and connected to the first inlet channel 11, ensuring even distribution of reagent to each microchannel 12 and preventing insufficient or excessive reagent in any single channel. Simultaneously, if the heating mechanism on the carrier 50 has been activated based on temperature sensor feedback, the multiple reaction microchannels 12 will be in a suitable temperature environment. The formaldehyde detection reagent entering at this time can maintain stable activity, preparing for subsequent reaction with formaldehyde without requiring additional reagent adjustments, ensuring smooth operation and stable reaction conditions.

[0119] S120: The gas to be tested is introduced into the first vent 131, and the reacted gas is discharged from the second vent 132, so that the formaldehyde in the gas to be tested reacts with the formaldehyde detection reagent in multiple reaction microchannels 12, and the reaction products of the formaldehyde detection reagent and formaldehyde enter the detection channel 14. After the gas to be tested is introduced into the first vent 131, the gas enters multiple reaction microchannels 12 through the gas channel 13 and comes into contact with the previously introduced formaldehyde detection reagent. The reaction products flow out along multiple reaction microchannels 12 and finally flow into the detection channel 14. The entire process does not require manual intervention in product transfer. The interconnected design of the channels guides the products to flow naturally to the detection channel 14, preparing for subsequent detection.

[0120] S130. The reaction products within the detection channel 14 are detected by the detection instrument 141 to obtain the formaldehyde concentration in the gas to be detected. The signal transmitting component of the detection instrument 141 emits a specific type of detection signal into the detection channel 14. After the signal penetrates the reaction products, the signal receiving component receives the feedback signal. Different concentrations of reaction products absorb or reflect the detection signal to different degrees. The detection instrument 141 processes the signal differences to calculate the concentration of the reaction products, and then obtains the formaldehyde concentration in the gas to be detected based on the correlation between the concentration of the reaction products and the formaldehyde concentration. Taking ultraviolet light source detection as an example, the detection instrument 141 emits ultraviolet light with a wavelength of 280-320nm into the detection channel 14. The signal receiving component can be specifically an optical probe that receives the ultraviolet light signal that passes through the blue-green substance formed by the reaction product of the coloring product formaldehyde and the phenol reagent combined with ferric ammonium sulfate. The instrument calculates the concentration of the coloring product by calculating the light absorbance, and then obtains the formaldehyde concentration.

[0121] In some embodiments of this application, after introducing the gas to be detected into the first vent 131 and exporting the reacted gas from the second vent 132, the formaldehyde detection method further includes: introducing the reacted gas exported from the second vent 132 into the buffer chamber 40; and re-introducing the gas in the buffer chamber 40 as the gas to be detected into the first vent 131 through the airflow circulation drive 30.

[0122] When the post-reaction gas discharged from the second vent 132 is introduced into the buffer chamber 40, the buffer chamber 40 can temporarily store the gas. At this time, the discharged post-reaction gas may still contain formaldehyde that has not completely reacted with the formaldehyde detection reagent. Especially in trace formaldehyde scenarios, a single contact may result in missed reactions. The storage function of the buffer chamber 40 can avoid detection errors caused by the direct emission of this part of the gas, and at the same time provide a gas source for subsequent cycles.

[0123] When the gas in the buffer chamber 40 is re-introduced into the first vent 131 via the airflow circulation drive 30, the airflow circulation drive 30, as the core component of the airflow control assembly, provides stable power to propel the gas back into the gas flow channel 13 of the trace formaldehyde detection chip 100, allowing residual formaldehyde to re-engage with the formaldehyde detection reagents in the multiple reaction microchannels 12. Compared to a single-pass ventilation process, this cyclical operation prolongs the contact time between formaldehyde and the reagents, allowing previously unreacted formaldehyde to fully participate in the reaction, improving the efficiency of formaldehyde conversion into reaction products, avoiding low concentrations of reaction products due to residual formaldehyde, and ensuring that the concentration of reaction products in the subsequent detection channel 14 more closely matches the actual formaldehyde content in the gas to be detected. Simultaneously, the buffer chamber 40 also plays a role in stabilizing the airflow during the circulation process. When the airflow circulation drive 30 directly propels the gas, flow rate fluctuations are likely to occur. The buffer chamber 40 can buffer the airflow through its internal space, keeping the gas flow rate returning to the first air inlet 131 stable. This avoids uneven gas distribution within the multiple reaction microchannels 12 due to sudden changes in flow rate, ensuring consistent contact conditions between formaldehyde and reagents in each cycle. Furthermore, this circulation step does not require the addition of additional gas to be detected; the detection effect can be improved simply by reusing existing gas. This reduces gas waste and eliminates the need for complex operations, maintaining consistency with the overall low-cost and easy-to-operate characteristics of the detection method, further ensuring the accuracy and reliability of trace formaldehyde detection results.

[0124] In some embodiments of this application, after introducing the gas to be detected into the first vent 131 and exiting the reacted gas from the second vent 132, the formaldehyde detection method further includes: stopping the introduction of the gas to be detected into the first vent 131; introducing the gas to be detected into the second vent 132 and exiting the reacted gas from the first vent 131.

[0125] After stopping the introduction of the gas to be tested into the first vent 131, the gas to be tested is introduced into the second vent 132. At this time, the gas flows along the path of the first vent 131 of the gas flow channel 13 of the second vent 132 and the multiple reaction microchannels 12 of the multiple reaction microchannels 12, which is opposite to the forward airflow direction of the second vent 132 of the gas flow channel 13 of the first vent 131 and the multiple reaction microchannels 12 in step S120. During forward airflow, the gas may not fully contact the formaldehyde detection reagent in some areas due to the resistance difference in the gas flow channel 13 or the slight uneven distribution of reagents in the multiple reaction microchannels 12. Reverse airflow changes the flow path of the gas in the channel, so that the gas more evenly covers every part of the reagent in the multiple reaction microchannels 12, allowing the residual formaldehyde detection reagent to fully participate in the reaction, and at the same time allowing the unreacted formaldehyde in the gas to be tested to come into contact with the reagent again, improving the overall reaction conversion rate and avoiding the problem of incomplete and uneven reaction caused by a single airflow direction.

[0126] Table 1. Comparison with typical methods such as phenol reagent spectrophotometry and DNPH-HPLC

[0127]

[0128] The trace formaldehyde detection chip based on microfluidic technology (hereinafter referred to as microfluidic chip) of this application has the characteristics of high detection accuracy, short detection time, low consumables and low cost.

[0129] Specifically, microfluidic channels typically range in size from tens to hundreds of micrometers, with volumes ranging from nanoliters to microliters. At this scale, the volume of reagents required to drive the fluid and conduct chemical reactions decreases exponentially. Therefore, the reagent volume per sample can be as low as 0.4 μL, resulting in a corresponding reduction in cost. In micrometer-scale channels, the fluid is predominantly laminar, with mass transfer relying mainly on diffusion over extremely short distances. This allows formaldehyde and reagents to mix and react thoroughly and uniformly in a very short time, with reaction efficiency far exceeding that of slow diffusion and stirring in macroscopic test tubes, significantly shortening sampling and measurement time. High-efficiency reactions mean that more analytes are converted into detectable signal molecules. Small sample volumes (as low as 0.4 μL) mean that reaction products are highly concentrated in a very small space. During optical detection, although the optical path may be short, the product concentration within the detection area is extremely high, generating a strong detection signal. Furthermore, realizing reactions and detection within a microfluidic chip reduces external interference, thereby lowering background noise. Therefore, the embodiments of this application have the characteristics of high detection accuracy, short detection time and low consumables of microfluidic chips.

[0130] Traditional microfluidic technology, while offering significant advantages due to its small reagent volume, also suffers from several drawbacks, primarily in two aspects. First, the signal intensity captured by the detection instrument is generally proportional to the amount of substances participating in the reaction. Fewer formaldehyde detection reagents and samples mean a relatively smaller absolute amount of reaction products, resulting in a weaker detection signal. Second, at the microscale, the influence of contaminants is significantly amplified, introducing substantial random errors. To address this, this application employs multiple reaction microchannels 12, allowing the formaldehyde detection reagents in the multiple reaction microchannels 12 and the formaldehyde from the gas channel 13 to contact and react independently, finally converging in the detection channel 14 for detection. On one hand, the final detection instrument detects the reaction products from the convergence of multiple reaction microchannels, which significantly increases the total amount of reaction products detected, thereby improving the detection signal intensity while maintaining a suitable microfluidic reaction. On the other hand, because this application employs multiple reaction microchannels 12, even if one reaction microchannel 12 becomes contaminated, leading to detection anomalies, the contamination will be significantly reduced when it merges with other reaction microchannels 12, thus mitigating the deviation in detection results caused by contamination. In addition, the detection gas is sequentially introduced into multiple reaction microchannels 12. In particular, the method of circulating the detection gas ensures that the formaldehyde in the detection gas can participate in the reaction more thoroughly, thereby effectively improving the detection precision and accuracy.

[0131] Finally, because the microfluidic chip uses multiple reaction microchannels 12 to participate in the absorption and reaction of formaldehyde simultaneously, the reaction time can be greatly shortened. The detection gas can continuously enter the gas channel 13 and react with the formaldehyde detection reagent in each reaction microchannel 12. The formaldehyde detection reagent can also be continuously replenished into each reaction microchannel 12. Therefore, continuous flow detection and online detection of formaldehyde can be achieved.

[0132] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A trace formaldehyde detection device based on microfluidic technology, characterized in that, The trace formaldehyde detection device based on microfluidic technology comprises a trace formaldehyde detection chip based on microfluidic technology, which comprises: a first liquid inlet channel, provided with a first liquid inlet for introducing a formaldehyde detection reagent; a plurality of reaction micro-channels, each in communication with the first liquid inlet channel, so that the formaldehyde detection reagent is shunted from the first liquid inlet channel to the plurality of reaction micro-channels; a gas flow channel, provided with a first gas inlet and a second gas inlet, one of which is used to introduce the gas to be detected, and the other is used to discharge the gas after reaction, the gas flow channel being in communication with the plurality of reaction micro-channels, so that the formaldehyde in the gas to be detected and the formaldehyde detection reagent in the plurality of reaction micro-channels are in contact and react; a detection channel, in communication with the plurality of reaction micro-channels, and provided with a detection instrument on the detection channel to detect the reaction product of the formaldehyde detection reagent and formaldehyde; the connection between the gas flow channel and the reaction micro-channels forms a connection space, the reaction micro-channels are located in the lower part of the connection space, and the gas flow channel is located in the upper part of the connection space; the formaldehyde detection device further comprises an air flow circulation driving member and a buffer chamber; one end of the air flow circulation driving member is in communication with the buffer chamber, the other end is in communication with the first gas inlet, the second gas inlet is in communication with the buffer chamber, forming a circulation path connecting the buffer chamber, the air flow circulation driving member, the first gas inlet, the gas flow channel and the second gas inlet, so that the gas to be detected repeatedly flows through the plurality of reaction micro-channels and contacts the formaldehyde detection reagent, the formaldehyde that has not completely reacted during the first contact is returned to the buffer chamber and reenters the gas flow channel through circulation to contact the formaldehyde detection reagent again.

2. The microfluidic-based trace formaldehyde detection device of claim 1, wherein, The trace formaldehyde detection device comprises a bottom plate and a top plate, the bottom plate is provided with a first recess to form the reaction micro-channels, and the top plate is provided with a second recess to form the gas flow channel, and the top plate covers the bottom plate so that the gas flow channel is located above the reaction micro-channels.

3. The microfluidic-based trace formaldehyde detection device of claim 2, wherein, The plurality of reaction micro-channels extend along a first direction, the gas flow channel extends along a second direction, and the first direction intersects the second direction, so that the gas flow channel and the plurality of reaction micro-channels are in communication.

4. The microfluidic-based trace formaldehyde detection device of claim 3, wherein, The top plate is provided with a first gas pipe and a second gas pipe on both sides, the first gas pipe has a first through hole part and a first closed part, and the second gas pipe has a second through hole part and a second closed part; the first through hole part is opposite to the top plate, and the first gas inlet is arranged in the first through hole part, the second through hole part is opposite to the top plate, and the second gas inlet is arranged in the second through hole part; the first closed part and the second closed part are opposite to the bottom plate, so that the bottom plate is positioned between the first closed part and the second closed part on both sides.

5. The microfluidic-based trace formaldehyde detection device of claim 4, wherein, The gas flow channel is provided with expansion cavities at both ends, and the gas flow channel is connected to the first vent and the second vent through the expansion cavities at both ends, respectively.

6. The microfluidic-based trace formaldehyde detection device according to any one of claims 1-5, wherein, The trace formaldehyde detection device further includes a second liquid inlet channel, which is provided with a second inlet for introducing a colorant, and the second liquid inlet channel is connected between the reaction microchannel and the detection channel.

7. The microfluidic-based trace formaldehyde detection device of claim 6, wherein, The trace formaldehyde detection device further includes a coloring channel, which is connected between the second liquid inlet channel and the detection channel, and the coloring channel is arranged in a serpentine shape.

8. The microfluidic-based trace formaldehyde detection device of claim 6, wherein, A mixing chamber is provided between the second inlet channel and the reaction microchannel so that the fluids of the multiple reaction microchannels are mixed in the mixing chamber before being mixed with the colorant of the second inlet channel.

9. The microfluidic-based trace formaldehyde detection device of claim 8, wherein, The trace formaldehyde detection device also includes an exhaust channel connected above the mixing chamber for discharging the gas collected in the upper part of the mixing chamber.

10. The microfluidic-based trace formaldehyde detection device of claim 6, wherein, The detection instrument includes an ultraviolet light source and an optical probe. The ultraviolet light source is used to emit ultraviolet light into the detection channel, and the optical probe is used to receive the optical signal fed back by the fluid in the detection channel to detect the product after coloring by the colorant.

11. The trace formaldehyde detection device as claimed in claim 1, wherein, The formaldehyde detection device includes a carrier, and the trace formaldehyde detection chip is disposed on the carrier; The carrier is provided with a heating mechanism, and the trace formaldehyde detection chip is provided with a temperature measuring element for detecting the temperature of the trace formaldehyde detection chip. The heating mechanism is configured to heat the trace formaldehyde detection chip based on the temperature measured by the temperature measuring element.

12. A method of detecting formaldehyde, characterized by, The formaldehyde detection method employs the trace formaldehyde detection device according to any one of claims 1-11, and the formaldehyde detection method includes: Formaldehyde detection reagent is introduced into the first liquid inlet channel so that the formaldehyde detection reagent enters the plurality of reaction microchannels; The gas to be tested is introduced into the first vent and the gas after reaction is discharged from the second vent, so that the formaldehyde in the gas to be tested reacts with the formaldehyde detection reagents in the multiple reaction microchannels, and the reaction products of the formaldehyde detection reagents and formaldehyde enter the detection channel. The reaction products within the detection channel are detected by the detection instrument to obtain the formaldehyde concentration in the gas to be detected.

13. The formaldehyde detection method according to claim 12, wherein, After introducing the gas to be detected into the first vent and exiting the reacted gas through the second vent, the formaldehyde detection method further includes: The reacted gas discharged from the second vent is introduced into the buffer chamber; The gas in the buffer chamber is re-introduced into the first vent as the gas to be tested through the airflow circulation drive.

14. The formaldehyde detection method according to claim 12, wherein, After introducing the gas to be detected into the first vent and exiting the reacted gas through the second vent, the formaldehyde detection method further includes: Stop introducing the gas to be tested into the first vent. The gas to be tested is introduced into the second vent, and the gas after reaction is discharged from the first vent.

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