Multipurpose microwave sensor capable of detecting gas flow and liquid flow

Abstract

The invention discloses a multipurpose microwave sensor capable of detecting gas and liquid flow, and belongs to the field of microwave sensors. The sensor comprises a micro-fluidic chip and an LC resonator, the micro-fluidic chip comprises an LC resonator etching tank and a pipeline for injecting and exporting a substance to be detected into and out of the LC resonator etching tank, the LC resonator comprises an inductance coil and a capacitor array, and a metal block array is arranged in the capacitor array; the micro-fluidic chip is tightly attached to the LC resonator, an etching groove of the LC resonator covers the capacitor array, and a cavity is formed in the metal block array. According to the microwave flow sensor, the influence of the content of a substance to be detected on the resonant frequency is utilized, accurate detection of gas and liquid flow can be achieved, the microwave flow sensor can also be used for detecting the purity of the substance, and compared with an existing microwave flow sensor, the microwave flow sensor is not limited to detection of single gas or liquid flow, has high universality and wide application and is suitable for popularization and application. And relatively high detection precision can be achieved.

Description

Technical Field

[0001] The invention relates to a multi-purpose microwave sensor capable of detecting gas and liquid flow, belonging to the field of microwave sensors. Background Art

[0002] With the continuous development of science and technology, flow sensors, as a key sensor, have received more and more attention and are also playing a role in various practical application fields. Flow sensors are important tools for real-time monitoring of fluid status. They can be widely used in automated production, fire safety, medical oxygen, mine gas detection, environmental waste gas detection and other fields. Its function is to detect the flow rate of gas or liquid in the pipeline, and then convert the flow value into an electrical signal output. First of all, taking the medical industry as an example, the successful use of gas flow sensors and their use as a key part of new medical instruments is of great significance for medical therapies that mainly treat respiratory diseases. For example, gas flow sensors are needed for the treatment of major diseases such as COPD (chronic obstructive pulmonary disease) at this stage. For example, they are used on oxygen supply devices to accurately provide patients with the required oxygen supply. Some high-end wearable devices can also draw individual breathing curves based on the data collected by gas flow sensors for personalized adjustment and treatment. In addition, in the field of environmental protection, flow sensors are used as monitoring tools for the control of waste gas emissions, especially the monitoring of the emission of harmful gases and the monitoring of atmospheric environmental quality, playing a very important role in environmental protection. For example, when used in the online automatic monitoring system of air pollution sources, the pollutant concentration and emission in the exhaust gas can be accurately measured, which is of great significance to the environmental compliance of enterprises, the supervision of government environmental protection, and the promotion of social environmental protection. Therefore, whether in the medical or environmental protection field, flow sensors can provide us with accurate data support, so that we can control and utilize gas resources within a reasonable range, potentially improve the quality of life, and protect the environment. At the same time, the future development of flow sensors will also be more diversified, high-precision, and miniaturized to meet a wider range of application needs.

[0003] In addition to the huge impact at the application level, flow sensors still have great practical significance in terms of detection objects and detection principles, but there are also some problems and challenges. In terms of detection objects, a single liquid or gas sensor may not fully meet the needs of certain specific applications in terms of accuracy. In some fields that require extremely precise measurements, such as medical equipment and precision chemicals, a little error may lead to serious consequences. Although many flow sensors on the market claim to have high measurement accuracy, in actual operation, accuracy is often affected by various factors, such as changes in fluid pressure, temperature fluctuations, air humidity, pipeline vibration, etc. In addition, a single gas or liquid flow sensor may experience performance degradation when dealing with different types of fluids. Some flow sensors may only have good measurement effects on specific types of gases or liquids, but poor results on other types. For mixed fluids containing multiple components, such as industrial wastewater or chemical mixed gases, a single flow sensor may not be able to measure accurately and effectively. Therefore, flow sensors that detect mixed gases and liquids, or flow sensors that can perform both, are the future development direction of flow sensors. Summary of the invention

[0004] In order to solve the problems commonly found in existing traditional flow sensors: single fluid detection, low accuracy, limited application direction, and large area, the present invention provides a multi-purpose microwave sensor that can detect gas and liquid flow. The technical solution is as follows:

[0005] The present invention provides a microwave sensor, comprising: a microfluidic chip and an LC resonator;

[0006] The microfluidic chip comprises: an LC resonator etching groove and a pipeline for injecting and exporting the substance to be tested into and out of the LC resonator etching groove;

[0007] The LC resonator comprises an inductor coil and a capacitor array, wherein the capacitor array is provided with a metal block array;

[0008] The microfluidic chip and the LC resonator are closely attached, and the LC resonator etching groove covers the capacitor array, forming a cavity in the metal block array.

[0009] In the case where the microwave flow sensor of the present invention is not combined with a microfluidic chip, the LC resonator can be regarded as a specific frequency filter of a pure electronic chip, and can be adapted to a variety of uses when connected to circuits with different structures. For example, when connected to a high-power circuit containing a power supply, it can be used as an important part of the filter circuit to filter out the remaining high-frequency disturbance components in the power supply, which is of great significance to the stability and interference removal of the power supply voltage. In addition, when the filter is connected to a high-frequency line and a specific resonant frequency is set, it can be used as an important component of the communication system, mainly used to select the signals we need and eliminate signal interference from other frequency bands, which is of great significance for signal modulation and demodulation.

[0010] Optionally, the pipeline includes: a plurality of pipelines for introducing the base fluid and the substance to be tested.

[0011] Optionally, the microfluidic chip is made of PDMS material.

[0012] Optionally, the inductor coil adopts a bridge-type cross structure.

[0013] Optionally, the substance to be tested includes: gas and liquid.

[0014] The present invention provides a liquid flow detection method, which uses the microwave sensor as described in any one of the above items to calculate the flow rate of liquid substances, and the method comprises:

[0015] Injecting substrate liquid into the LC resonator etching groove through the first pipeline, detecting and recording the resonant frequency of the LC resonator;

[0016] While continuously injecting the base liquid, introducing the liquid to be tested into the LC resonator etching groove through the second pipeline, detecting and recording the resonant frequency of the LC resonator;

[0017] The flow rate of the liquid to be measured is obtained according to the fitting relationship between the change of the resonance frequency and the concentration of the liquid to be measured.

[0018] The present invention provides a method for detecting liquid concentration, wherein the method uses a microwave sensor as described in any one of the above items to perform concentration detection, and the method comprises:

[0019] The liquid to be tested is injected into the etching groove of the LC resonator, the resonant frequency of the LC resonator is detected, and the concentration of the liquid to be tested is obtained according to the fitting relationship between the resonant frequency and the concentration.

[0020] The present invention provides a gas flow sensing method, the method adopts the microwave sensor as described in any one of the above items to calculate the flow rate of gaseous substances, the method comprising:

[0021] Injecting substrate liquid into the LC resonator etching groove through the first pipeline, detecting and recording the resonant frequency of the LC resonator;

[0022] While continuously injecting the base liquid, the liquid to be tested is introduced into the LC resonator etching groove through the second pipeline to detect and record the resonant frequency of the LC resonator;

[0023] The flow rate of the gas to be measured is obtained according to the fitting relationship between the change of the resonance frequency and the flow rate of the gas to be measured.

[0024] The beneficial effects of the present invention are:

[0025] (1) The present invention utilizes the microwave resonance principle to detect the flow value by changing the resonant frequency, which can make a small change in the fluid produce a significant change in the resonant frequency, thereby improving the accuracy of the sensor to a certain extent.

[0026] (2) Since the present invention adopts a non-contact detection method and the microfluidic chip can use PDMS, a biocompatible material, it has a good effect on the detection of special materials and some medical fluids, and broadens the detection fluid range of traditional flow sensors.

[0027] (3) The present invention carries out a targeted structural design for the LC resonator. For the inductor element, a bridge-type cross structure is used to achieve a suitable inductance value while ensuring a relatively small area. For the capacitor element, a metal block array is used to help influence the mixing of the fluid into the base fluid. Therefore, compared with the traditional microwave flow sensor, the present invention has a stronger professionalism in fluid detection.

[0028] (4) The present invention is a specific filter in principle, which can not only play a role in detecting the flow rate of fluid, but also can detect the content of impurities that affect the dielectric constant of the fluid, reflecting the multi-purpose characteristics of this invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 It is an integrated structural diagram of a multi-purpose microwave sensor capable of detecting gas and liquid flow provided by the present invention.

[0031] Figure 2 It is a structural diagram of the microfluidic chip provided in Example 2 of the present invention.

[0032] Figure 3 It is a structural diagram of the LC resonator provided in the second embodiment of the present invention.

[0033] Figure 4 The position relationship diagram of the sensor and the microfluidic structure provided in the second embodiment of the present invention is

[0034] Figure 5 This is a position boundary relationship diagram of the sensor and the microfluidic structure provided in the second embodiment of the present invention.

[0035] Figure 6 is the S-parameter resonance diagram of an example of the present invention.

[0036] Figure 7 This is the S11 parameter simulation curve of the sensor in the glucose solution environment

[0037] Figure 8 This is the S11 parameter simulation curve of the sensor in a nitrogen environment

[0038] Fig. 9 This is the S11 parameter simulation curve of the sensor in an oily reagent environment DETAILED DESCRIPTION

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0040] Embodiment 1:

[0041] This embodiment provides a microwave sensor, such as Figure 1 As shown, it includes: a microfluidic chip and an LC resonator.

[0042] The microfluidic chip of this embodiment uses PDMS material, which has the following advantages: first, it has a lower cost and is more economical and applicable than many commonly used materials for microfluidic chips (such as corrosion-resistant metals or semiconductor materials), which greatly reduces the manufacturing cost of the microfluidic chip; second, it is non-toxic and environmentally friendly. PDMS is a biocompatible material that can directly contact biological samples without contaminating the samples, thus broadening the scope of fluid detection objects; and finally, it has good transparency. PDMS has good transparency, which makes it easy for researchers to directly observe the flow phenomenon in the chip, which allows them to always pay attention to the situation of the fluid itself during actual use.

[0043] The structure of the microfluidic chip in this embodiment is as follows Figure 2As shown, it includes: an LC resonator etching groove, a main pipe for injecting the base fluid into the LC resonator etching groove, a secondary pipe for injecting the fluid to be tested, and a liquid outlet pipe. The main pipe has a larger diameter than the secondary pipe, in order to prevent the overflow and splashing of the fluid to be tested when it is mixed into the fluid to be tested in actual use. After subsequent use, it was found that this phenomenon can be better avoided. In addition, the LC resonator etching groove can be accurately fitted to the LC resonator part located below the microfluidic chip by using a special process and taking advantage of the good flexibility of the PDMS material.

[0044] The base fluid is a liquid that is not easily miscible or reactive with the liquid or gas being tested. If nitrogen is to be tested, water can be used; if benzene is to be tested, water can also be used.

[0045] The LC resonator structure of this embodiment is as follows Figure 3 As shown in the figure, it consists of two parts, namely the inductor coil and the capacitor array. For the inductor coil, in addition to the common coil winding method, a bridge-type cross structure is also used to successfully increase the inductance value while using a smaller area. In addition, for the capacitor array, the capacitor area in the middle is designed as a metal block array, which helps to fully mix the liquid and generate bubbles.

[0046] The microfluidic chip and the LC resonator fit tightly together, such as Figure 4 , 5 As shown, the LC resonator etching groove covers the capacitor array, and a cavity is formed in the metal block array.

[0047] Based on the above structure, the working principle of the microwave sensor in this embodiment is described as follows:

[0048] The flow sensor uses the microwave principle, and when the substance to be tested (including gas and liquid) is mixed into the base liquid, the content of the substance to be tested mixed into the liquid per unit time changes with the change of the flow rate of the substance to be tested, thereby causing the dielectric constant of the fluid to change, affecting the overall capacitance value, and then affecting the resonant frequency. A specific electrical signal with fluid flow information will be generated in the access circuit, and the fluid flow information can be obtained through subsequent circuit design or VNA instrumentation. From the perspective of principle, unlike traditional micromachines, this microwave principle flow sensor will not produce common mechanical structural strain. In addition, at the level of the targeted measurement object, since the microwave flow sensor uses a microfluidic chip for flow guidance, it overcomes the disadvantage that the traditional micromechanical structure needs to directly contact the detection object, and broadens the fluid detection object, especially for some sample fluids that are prohibited from contact in medical aspects and special materials in special engineering.

[0049] In addition, in terms of the essence of the principle, the microwave flow sensor of this embodiment can be understood as a specific filter, which uses the influence of the gas in the fluid or substances other than the base liquid itself on the dielectric constant of the fluid to detect the substance content in the fluid.

[0050] Finally, the LC resonance effect after ADS and HFSS simulation is as follows Figure 6 As shown. Figure 6 In the figure, the red parameter curve represents the S11 reflection coefficient, and S21 represents the forward transmission coefficient. From the peaks and troughs of the two curves, it can be concluded that the microwave resonant sensor has good frequency selectivity.

[0051] In summary, the microwave flow sensor of this embodiment can solve the problems of single fluid detection, low accuracy, limited application direction and large area while achieving basic functions.

[0052] Embodiment 2

[0053] This embodiment uses the sensor described in the first embodiment to detect the flow rate of the glucose solution. The flow rate detection here can be reflected by the concentration of the glucose solution per unit time, that is, the content of the glucose solution passed in per unit time is detected.

[0054] The main principle is that the different contents of substances in the measured liquid lead to different dielectric constants between capacitors, which affects the capacitance value and finally affects the resonant frequency of the LC resonator. The concentration information of the measured liquid is obtained by detecting the resonant frequency signal in the circuit.

[0055] To detect the purity of glucose in a laboratory environment, the glucose solution to be tested can be mixed into the auxiliary pipe, and pure water can be added into the main pipe as a mixing base. Based on the above principle, different contents of glucose in the mixed solution injected into the etching tank of the LC resonator correspond to different dielectric constants between capacitors, that is, they correspond to different resonant frequencies of the LC resonator. There is a fitting relationship between the two. Based on this fitting relationship, the concentration of glucose can be obtained. Combined with the flow rate of the injected pure water, the actual content of glucose can be obtained, and finally the purity of glucose can be obtained. The resonance characteristic curve of the actual concentration of the glucose solution is shown in the figure below: Figure 7 shown.

[0056] It is worth noting that if only the concentration of the mixed glucose solution needs to be detected, the solution to be tested can be directly introduced into the LC resonator etching tank, which is more convenient. The glucose content in the solution is determined by detecting different resonance frequencies, which also reflects the flow rate of the glucose solution to be tested.

[0057] Embodiment three:

[0058] This embodiment provides a gas flow detection method, which uses the sensor described in the first embodiment to detect the gas flow. The main detection method is to introduce the base liquid and the gas to be measured into the main pipe and the auxiliary pipe respectively, and the mixed fluid flows into the capacitor array in the LC resonator. Due to the amount of gas mixed in, the dielectric constant of the mixed fluid will change accordingly, so the flow of the gas to be measured can be obtained after detecting the resonance frequency.

[0059] This method of detecting gas has a high detection accuracy, so it is well suited for the patient vital sign monitoring system for respiratory monitoring in medical treatment. In particular, in the context of the mixed gas with complex components, it is difficult for the sensor to measure the effect. The microwave flow sensor proposed in the present invention detects the change of the dielectric constant of the mixed fluid, and does not need to detect a specific gas, so it has a natural advantage in this respect.

[0060] In addition, when detecting nitrogen (N 2 ) Such gases that are difficult to dissolve in liquids, the sensor can use the physical properties of the gas to better promote the mixing of the measured gas with the base fluid to form bubbles, thereby improving the accuracy of detection. In the field of food preservation and storage, the present invention can monitor the nitrogen filling packaging machine 2 Compared with the conventional flow monitoring instruments or sensors with large volume, the compact size of the present invention enables it to be flexibly integrated with a variety of inflatable devices, thus achieving more convenient applications.

[0061] This embodiment uses nitrogen gas as an example to verify the feasibility and detection effect of gas flow detection. The value of the resonant frequency of the microwave device is detected, and the gas content is deduced by comparing the resonance fitting curve to reflect the value of the gas flow. The actual resonance characteristic curve of the concentration of the glucose solution is as follows: Figure 8 shown.

[0062] Embodiment 4:

[0063] This embodiment provides a liquid flow detection method, which uses the sensor described in the first embodiment to detect the flow of an oily reagent. The oily reagent is a type of liquid fluid that is immiscible with water. Consistent with the above embodiment, the oily reagent is introduced into the auxiliary pipe and water is introduced into the main pipe. The dielectric constant in the resonator changes due to the gradual change from the initial water to the oily reagent. Similarly, if the flow of the oily reagent decreases, the dielectric constant will change in the opposite direction accordingly. The flow of the corresponding oily reagent can be deduced from the frequency fitting curve of the corresponding substance. The actual resonance characteristic curve of the concentration of the glucose solution is shown in FIG. Fig. 9 shown.

[0064] Some steps in the embodiments of the present invention may be implemented using software, and the corresponding software program may be stored in a readable storage medium, such as a CD or a hard disk.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A microwave sensor, characterized in that: The microwave sensor comprises: a microfluidic chip and an LC resonator; The microfluidic chip comprises: an LC resonator etching groove and a pipeline for injecting and exporting the substance to be tested into and out of the LC resonator etching groove; The LC resonator comprises an inductor coil and a capacitor array, wherein the capacitor array is provided with a metal block array; The microfluidic chip and the LC resonator are closely attached, and the LC resonator etching groove covers the capacitor array, forming a cavity in the metal block array.

2. The microwave sensor according to claim 1, characterized in that: The pipeline includes: a plurality of pipelines for introducing the base fluid and the substance to be tested.

3. The microwave sensor according to claim 1, characterized in that: The microfluidic chip is made of PDMS material.

4. The microwave sensor according to claim 1, characterized in that: The inductor coil adopts a bridge-type cross structure.

5. The microwave sensor according to claim 1, characterized in that: The substances to be tested include: gas and liquid.

6. A liquid flow detection method, characterized in that: The method uses the microwave sensor according to any one of claims 1 to 5 to calculate the flow rate of liquid substances, and the method comprises: Injecting substrate liquid into the LC resonator etching groove through the first pipeline, detecting and recording the resonant frequency of the LC resonator; While continuously injecting the base liquid, introducing the liquid to be tested into the LC resonator etching groove through the second pipeline, detecting and recording the resonant frequency of the LC resonator; The flow rate of the liquid to be measured is obtained according to the fitting relationship between the change of the resonance frequency and the concentration of the liquid to be measured.

7. A method for detecting liquid concentration, the method using the microwave sensor according to any one of claims 1 to 5 to perform concentration detection, the method comprising: The liquid to be tested is injected into the etching groove of the LC resonator, the resonant frequency of the LC resonator is detected, and the concentration of the liquid to be tested is obtained according to the fitting relationship between the resonant frequency and the concentration.

8. A gas flow sensing method, characterized in that: The method uses the microwave sensor according to any one of claims 1 to 5 to calculate the flow rate of gaseous substances, and the method comprises: Injecting substrate liquid into the LC resonator etching groove through the first pipeline, detecting and recording the resonant frequency of the LC resonator; While continuously injecting the base liquid, the liquid to be tested is introduced into the LC resonator etching groove through the second pipeline to detect and record the resonant frequency of the LC resonator; The flow rate of the gas to be measured is obtained according to the fitting relationship between the change of the resonance frequency and the flow rate of the gas to be measured.

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