A dual-resonant microstrip patch sensor

Abstract

The present invention discloses a dual-resonant microstrip patch sensor, which comprises an upper substrate, a middle flexible substrate and a lower substrate arranged in sequence from top to bottom. A copper-plated metal patch is attached to the upper surface of the upper substrate, and a copper-plated ground plane is attached to the lower surface of the lower substrate. A microfluidic channel is etched on the middle flexible substrate, and the microfluidic channel is arranged below the circular metal patch. The microfluidic channel is a serpentine-bent rectangular channel. The dual-resonant microstrip patch sensor of the present invention adopts a three-layer structure. The microfluidic channel on the middle flexible substrate is located below the circularly slotted patch antenna, so that the liquid to be measured is under a strong electromagnetic field, increasing the sensitivity of the microstrip patch sensor. The circularly slotted pentagram patch antenna on the upper layer enables the sensor to have two resonance frequencies, enhancing the accuracy of detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid detection sensors, and particularly relates to a dual-resonant microstrip patch sensor. Background Art

[0002] When frying food, the temperature of the oil is usually heated to 170 °C or even higher. At this time, many chemical reactions occur in the cooking oil, which will cause many toxic volatile and non-volatile compounds to appear in the fried food. The quality of fried food mainly depends on the nature and type of the oil. However, the quality of the oil used in fried food is uneven at present, and most of them are oils that have been repeatedly heated and used. After the oil is heated, it will be consumed and degraded, resulting in a series of chemical reactions. This heated oil can cause chronic diseases in the human body and seriously damage people's health. Therefore, it is necessary to detect the quality of cooking oil.

[0003] In recent years, many domestic and foreign scholars have conducted research on the quality detection of oil. Most scholars have studied the effects of heating temperature, heating duration, and heating times on the quality of cooking oil. These researchers mainly determine the quality of cooking oil by analyzing the contents such as acid value and oxidation value of the oil. However, this method is not very economical, and it also requires professional technical personnel for analysis. Moreover, the use of solvents will also cause environmental pollution. With the rapid development of microwave technology, many scholars have begun to consider using microwave technology to detect the quality of various substances. The microstrip line technology is a non-contact technology that can remotely detect and analyze liquids, and can identify liquids with different dielectric constants by detecting changes in resonance frequency. Therefore, microwave technology has broad application prospects in monitoring cooking oil. Summary of the Invention

[0004] The technical problem solved by the present invention is to provide a dual-resonant microstrip patch sensor with a simple structure and reasonable design, and the microstrip patch sensor can achieve a high-sensitivity detection function.

[0005] The present invention adopts the following technical solutions to solve the above technical problems. A dual-resonant microstrip patch sensor, characterized in that it includes an upper substrate, a middle flexible substrate and a lower substrate arranged in sequence from top to bottom. A metal copper-plated patch is attached to the upper surface of the upper substrate. The metal copper-plated patch is formed by radially opening a rectangular groove in a circular metal patch and connecting it to a rectangular metal microstrip line arranged in the middle of the rectangular groove. A pentagram-shaped groove is opened in the middle of the circular metal patch to enable the circular slotted patch antenna formed by the metal copper-plated patch to have two resonant frequencies. The end of the rectangular metal microstrip line is welded to an SMA connector, and the SMA connector is connected to a vector network analyzer to form a liquid detection system. A copper-plated floor is attached to the lower surface of the lower substrate. A microfluidic channel is etched on the middle flexible substrate. The microfluidic channel is arranged below the circular metal patch to obtain the best electric field strength. The microfluidic channel is a serpentine bent rectangular channel for enabling the fluid to be measured to flow in from one end of the rectangular channel and flow out from the other end of the rectangular channel.

[0006] Further defined, the upper substrate, the middle flexible substrate and the lower substrate are all rectangular structures, and the upper substrate, the middle flexible substrate and the lower substrate are fixedly combined by nylon buttons.

[0007] Further defined, the thickness of the metal copper-plated patch is 0.035 mm.

[0008] Further defined, the materials of the upper substrate and the lower substrate are both epoxy resin, the dielectric constant of the material is 4.4, the length and width of the upper substrate and the lower substrate are both 68 mm, and the thickness of the upper substrate and the lower substrate are both 0.6 mm.

[0009] Further defined, the material of the middle flexible substrate is polydimethylsiloxane (PDMS), the dielectric constant of the material is 2.65, the length and width of the middle flexible substrate are both 68 mm, the thickness of the middle flexible substrate is 0.8 mm, the width of the rectangular channel is 2 mm, and the depth of the rectangular channel is 0.3 mm.

[0010] Further defined, the material of the copper-plated floor is copper, and the thickness of the copper-plated floor is 0.035 mm.

[0011] Further defined, the upper substrate, the middle flexible substrate and the lower substrate are all rectangular structures, and connection holes are respectively provided at the corner parts of the upper substrate, the middle flexible substrate and the lower substrate. And after the upper substrate, the middle flexible substrate and the lower substrate are stacked and combined in sequence, they are connected and fixed by nylon buttons matching the connection holes.

[0012] Further limited, the rectangular metal microstrip line is vertically connected to the middle of the bottom edge of the rectangular groove radially opened on the circular patch. The width of the rectangular metal microstrip line is 1.9 mm, and the length of the rectangular metal microstrip line is 6 mm. The device uses the metal microstrip line feeding method, and the impedance of the feeding input port is 50 Ω.

[0013] Compared with the prior art, the present invention has the following advantages and beneficial effects: The dual-resonant microstrip patch sensor of the present invention adopts a three-layer structure. The microfluidic channel on the middle flexible substrate is located below the circularly slotted patch antenna, so that the liquid to be measured is under a strong electromagnetic field, increasing the sensitivity of the microstrip patch sensor. The circularly opened five-pointed star slot patch antenna on the upper layer enables the sensor to have two resonant frequencies, enhancing the detection accuracy. Brief Description of the Drawings

[0014] Figure 1 is a schematic structural diagram of the present invention;

[0015] Figure 2 is a schematic structural diagram of the basic unit of the circular patch antenna of the present invention;

[0016] Figure 3 is a schematic structural diagram of the middle flexible substrate of the present invention

[0017] Figure 4 is a characteristic diagram of the reflection coefficient of the present invention;

[0018] Figure 5 is a result diagram of the frequency shift of the first resonance point of the present invention with the change of the dielectric constant;

[0019] Figure 6 is a result diagram of the frequency shift of the second resonance point of the present invention with the change of the dielectric constant.

[0020] In the figure: 1 - upper substrate, 2 - middle flexible substrate, 3 - lower substrate. Detailed Embodiment

[0021] The above content of the present invention will be further described in detail below through embodiments, but it should not be understood that the scope of the above subject matter of the present invention is limited to the following embodiments. Any technology implemented based on the above content of the present invention belongs to the scope of the present invention.

[0022] Such as Figure 1-3As shown in the figure, a dual-resonant microstrip patch sensor includes an upper substrate 1, a middle flexible substrate 2, and a lower substrate 3 arranged in sequence from top to bottom. A copper-plated metal patch is attached to the upper surface of the upper substrate 1. The copper-plated metal patch is formed by radially opening a rectangular slot in a circular metal patch and connecting it to a rectangular metal microstrip line arranged in the middle of the rectangular slot. A five-pointed star-shaped slot is opened in the middle of the circular metal patch to enable the circular slotted patch antenna formed by the copper-plated metal patch to have two resonant frequencies. The end of the rectangular metal microstrip line is welded to an SMA connector, and the SMA connector is connected to a vector network analyzer to form a liquid detection system. A copper-plated floor is attached to the lower surface of the lower substrate 3. A microfluidic channel is etched on the middle flexible substrate 2. The microfluidic channel is arranged below the circular metal patch to obtain the best electric field intensity. The microfluidic channel is a serpentine-bent rectangular channel for enabling the fluid to be measured to flow in from one rectangular channel and flow out from the other rectangular channel.

[0023] In the present invention, the upper substrate 1, the middle flexible substrate 2, and the lower substrate 3 are all rectangular structures, and the upper substrate 1, the middle flexible substrate 2, and the lower substrate 3 are fixedly combined by nylon buttons; the thickness of the copper-plated metal patch is 0.035 mm; the materials of the upper substrate 1 and the lower substrate 3 are both epoxy resins, the dielectric constant of the material is 4.4, the length and width of the upper substrate 1 and the lower substrate 3 are both 68 mm, and the thickness of the upper substrate 1 and the lower substrate 3 are both 0.6 mm; the material of the middle flexible substrate 2 is polydimethylsiloxane, the dielectric constant of the material is 2.65, the length and width of the middle flexible substrate 2 are both 68 mm, the thickness of the middle flexible substrate 2 is 0.8 mm, the width of the rectangular channel is 2 mm, and the depth of the rectangular channel is 0.3 mm; the material of the copper-plated floor is copper, and the thickness of the copper-plated floor is 0.035 mm; the upper substrate 1, the middle flexible substrate 2, and the lower substrate 3 are all rectangular structures, and connection holes are respectively arranged at the corner parts of the upper substrate 1, the middle flexible substrate 2, and the lower substrate 3. After the upper substrate 1, the middle flexible substrate 2, and the lower substrate 3 are sequentially stacked and combined, they are fixedly connected by nylon buttons matching the connection holes; the rectangular metal microstrip line is vertically connected to the middle of the bottom edge of the rectangular slot radially opened in the circular patch. The width of the rectangular metal microstrip line is 1.9 mm, the length of the rectangular metal microstrip line is 6 mm, and the device uses a metal microstrip line feeding method, and the impedance of the feeding input port is 50 Ω.

[0024] The principle of the present invention is as follows:

[0025] The present invention mainly conducts sensing detection on trace liquid samples of oils and fats. By using the electromagnetic field generated by the circular slotted patch antenna, it is extremely sensitive to the change in the dielectric constant of the liquid to be measured in the microfluidic channel, thereby realizing the quantitative detection of liquid samples of oils and fats.

[0026] During use, a peristaltic pump is used to pump the liquid to be measured into the microfluidic channel, and microwave is incident on this sensor perpendicular to the upper substrate, then the mass of the liquid to be measured can be detected. Since the microfluidic channel is directly below the circular slotted patch antenna, all the liquid to be measured is under a strong electric field, enhancing the sensitivity of the sensor.

[0027] The flexible PDMS substrate used in the sensor of the present invention can not only enhance the sensitivity of the sensor, but also reduce the error caused by the air gap, thus minimizing the error. At the same time, the sensor can be reused and the operation is simple. If the microfluidic channel of the sensor is damaged, it can be replaced.

[0028] In this embodiment, the ANSYS High Frequency Structure Simulator (HFSS) is also used to verify the sensitivity of this sensor.

[0029] Figure 4 It is the S11 characteristic diagram of the dual-resonant microstrip patch sensor provided for the implementation of the present invention. It can be seen from the figure that this sensor has two resonant frequencies, and its resonance frequencies are about 1.43 GHz and 2.68 GHz respectively.

[0030] Figure 5 and Figure 6 It is the result diagram of the microstrip patch sensor simulation for detecting the offset of different dielectric constants and resonant frequencies in the embodiment of the present invention, which are the offset result diagrams of the first and second resonant frequencies respectively.

[0031] The present invention has the following beneficial effects: (1) The microfluidic channel of the present invention is etched on the middle flexible substrate, which can not only enhance the sensitivity of the sensor, but also reduce the error caused by the air gap. If the microfluidic channel of the sensor is damaged, it can be replaced. (2) The present invention uses a circular metal structure patch antenna as the resonant unit, strengthening the electric field intensity around the circular slot, thereby improving the sensitivity of the sensor.

[0032] The above embodiments describe the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the scope of the principles of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A dual-resonant microstrip patch sensor, characterized in that It includes an upper substrate, a middle flexible substrate, and a lower substrate that are sequentially arranged from top to bottom. A metal copper-plated patch is attached to the upper surface of the upper substrate. The metal copper-plated patch is formed by radially opening a rectangular groove in a circular metal patch and connecting it to a rectangular metal microstrip line disposed in the middle of the rectangular groove. A pentagram-shaped groove is opened in the middle of the circular metal patch to enable the circular slot patch antenna formed by the metal copper-plated patch to have two resonant frequencies. The end of the rectangular metal microstrip line is welded to an SMA connector, and the SMA connector is connected to a vector network analyzer to form a liquid detection system. A copper-plated floor is attached to the lower surface of the lower substrate. A microfluidic channel is etched on the middle flexible substrate. The microfluidic channel is disposed below the circular metal patch to obtain the best electric field intensity. The microfluidic channel is a serpentine-bent rectangular channel for enabling the fluid to be measured to flow in from one end of the rectangular channel and flow out from the other end of the rectangular channel; The upper substrate, the middle flexible substrate, and the lower substrate are all rectangular structures, and the upper substrate, the middle flexible substrate, and the lower substrate are fixed by a combination of nylon buttons; the upper substrate, the middle flexible substrate, and the lower substrate are all rectangular structures, and connection holes are respectively provided at the corner parts of the upper substrate, the middle flexible substrate, and the lower substrate. After the upper substrate, the middle flexible substrate, and the lower substrate are sequentially stacked and combined, they are connected and fixed by nylon buttons that match the connection holes; The rectangular metal microstrip line is vertically connected to the middle of the bottom edge of the rectangular groove radially opened in the circular patch. The width of the rectangular metal microstrip line is 1.9 mm, the length of the rectangular metal microstrip line is 6 mm, and the device uses a metal microstrip line feeding method. The impedance of the feeding input port is 50 Ω.

2. The dual-resonant microstrip patch sensor according to claim 1, characterized in that: The thickness of the metal copper-plated patch is 0.035 mm.

3. The dual-resonant microstrip patch sensor according to claim 1, characterized in that: The materials of the upper substrate and the lower substrate are both epoxy resin, the dielectric constant of the material is 4.4, the length and width of the upper substrate and the lower substrate are both 68 mm, and the thicknesses of the upper substrate and the lower substrate are both 0.6 mm.

4. The dual-resonant microstrip patch sensor according to claim 1, wherein: The material of the middle flexible substrate is polydimethylsiloxane, the dielectric constant of the material is 2.65, the length and width of the middle flexible substrate are both 68 mm, the thickness of the middle flexible substrate is 0.8 mm, the width of the rectangular channel is 2 mm, and the depth of the rectangular channel is 0.3 mm.

5. The dual-resonant microstrip patch sensor according to claim 1, wherein: The material of the copper-plated floor is copper, and the thickness of the copper-plated floor is 0.035 mm.

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