A triple-resonance microfluidic sensor

Abstract

The present invention discloses a three-resonance microfluidic sensor, which includes an upper substrate, an intermediate flexible substrate and a lower substrate arranged in sequence from top to bottom, wherein a metal copper-plated patch is attached to the upper surface of the upper substrate, the metal copper-plated patch is composed of a circular metal patch connected to a rectangular metal microstrip line, 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 intermediate flexible substrate, the microfluidic channel is arranged below the circular metal patch, the microfluidic channel body is an annular channel of an open-loop structure, and the two ends of the annular channel of the open-loop structure are respectively provided with rectangular channels connected to the annular channel. The present invention can measure the dielectric constant of different liquids, and can identify and distinguish liquids, and has the characteristics of small size, low manufacturing cost, high sensitivity, and convenient detection process.

Description

Technical Field

[0001] The invention belongs to the technical field of engine oil detection devices, and in particular relates to a triple-resonance microfluidic sensor. Background Art

[0002] With the rapid development of modern industry, mechanical equipment is used more and more frequently. However, the wear of mechanical equipment will affect the normal operation and service life of mechanical equipment. Wear is the most common fault phenomenon in the working process of diesel engines. Excessive wear between the piston ring and the cylinder can cause the pressure in the cylinder to drop to less than the working pressure, the oil to be diluted by the fuel, the oil film to become thinner, and the formation of boundary lubrication or dry friction between the piston ring and the cylinder liner. Severe wear of the cylinder will cause the power, economy and reliability of the diesel engine to decrease, and even affect the normal operation of the diesel engine. The degree of cylinder wear is the main basis for determining whether the engine needs to be overhauled. At the same time, the quality of cylinder repair has a great impact on the power, economy and reliability of the engine. Engine oil plays an important role in the normal operation of mechanical equipment. Therefore, it is very necessary to monitor the quality of engine oil.

[0003] Microwave refers to electromagnetic waves with a frequency of 300MHz-3000GHz. It is the abbreviation of a limited frequency band in radio waves, that is, electromagnetic waves with a wavelength between 1 meter (excluding 1 meter) and 0.1 mm. It is a general term for decimeter waves, centimeter waves, millimeter waves and submillimeter waves. Radio frequency and microwave technology used for sensing liquids are important non-contact technologies, especially in remote detection and analysis of liquids. It has broad application prospects for monitoring engine oil. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a triple-resonance microfluidic sensor with a simple structure and reasonable design, and the microfluidic sensor can realize a high-sensitivity detection function.

[0005] The present invention adopts the following technical scheme to solve the above technical problems: a three-resonance microfluidic sensor, characterized in that it includes an upper substrate, an intermediate flexible substrate and a lower substrate arranged in sequence from top to bottom, wherein a metal copper-plated patch is attached to the upper surface of the upper substrate, and the metal copper-plated patch is composed of a circular metal patch connected to a rectangular metal microstrip line, 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, and a microfluidic channel is etched on the intermediate flexible substrate, and the microfluidic channel is arranged below the circular metal patch to obtain an optimal electric field strength. The main body of the microfluidic channel is an annular groove of an open-loop structure, and rectangular grooves connected to the annular groove are respectively provided at both ends of the annular groove of the open-loop structure, so as to realize that the fluid to be measured flows into the annular groove from the rectangular groove on one side and flows out from the rectangular groove on the other side.

[0006] It is further defined that 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 nylon button combination.

[0007] It is further defined that the metal copper-plated patch is composed of a circular metal patch and a rectangular metal microstrip line radially connected to the outside of the circular metal patch, and the circular patch antenna formed by the metal copper-plated patch has three resonant frequencies, and the thickness of the metal copper-plated patch is 0.035 mm.

[0008] It is further defined that the material 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 66 mm, and the thickness of the upper substrate and the lower substrate is 0.4 mm.

[0009] It is further defined that the material of the intermediate flexible substrate is polydimethylsiloxane (PDMS), the dielectric constant of the material is 2.65, the length and width of the intermediate flexible substrate are both 66 mm, the thickness of the intermediate flexible substrate is 0.5 mm, the width of the annular groove and the rectangular groove are both 2 mm, and the depth of the annular groove and the rectangular groove are both 0.3 mm.

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

[0011] It is further defined that the upper substrate, the middle flexible substrate and the lower substrate are all rectangular structures and connection holes are respectively provided at the corners of the upper substrate, the middle flexible substrate and the lower substrate, and the upper substrate, the middle flexible substrate and the lower substrate are sequentially superimposed and combined and connected and fixed by nylon buttons matching the connection holes.

[0012] It is further defined that the width of the rectangular metal microstrip line is 1.9 mm, the length of the rectangular metal microstrip line is 7 mm, the device uses a rectangular metal microstrip line feeding method, and the impedance of the feeding input port is 50Ω.

[0013] Compared with the prior art, the present invention has the following beneficial effects: the three-resonance microfluidic sensor of the present invention can measure the dielectric constant of different liquids by connecting with a vector network analyzer, and can identify and distinguish the liquids, and has the characteristics of small size, low manufacturing cost, high sensitivity, and convenient detection process. The present invention adopts a three-layer structure, the microchannel of the middle layer is under the patch antenna, so that the liquid to be measured is in a strong electric field, which increases the sensitivity of the sensor, and the circular patch antenna of the upper layer enables the sensor to have three resonant frequency points, which enhances the accuracy of detection. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0016] Figure 3 This is a schematic diagram of the structure of the intermediate flexible substrate of the present invention.

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

[0018] Figure 5 is a result diagram showing the frequency offset of the first resonance point of the present invention as the dielectric constant changes;

[0019] Figure 6 is a result diagram showing the frequency offset of the second resonance point of the present invention as the dielectric constant changes;

[0020] Figure 7 This is a graph showing the frequency offset of the third resonance point of the present invention as the dielectric constant changes.

[0021] In the figure: 1-upper substrate, 2-middle flexible substrate, 3-lower base. DETAILED DESCRIPTION

[0022] The above contents of the present invention are further described in detail below through examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies implemented based on the above contents of the present invention belong to the scope of the present invention.

[0023] like Figure 1-3 As shown, a three-resonance microfluidic sensor comprises an upper substrate 1, an intermediate flexible substrate 2 and a lower substrate 3 which are arranged in sequence from top to bottom, wherein a metal copper-plated patch is attached to the upper surface of the upper substrate 1, and the metal copper-plated patch is composed of a circular metal patch connected to a rectangular metal microstrip line, 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 intermediate flexible substrate 2, and the microfluidic channel is arranged below the circular metal patch to obtain an optimal electric field strength, the microfluidic channel body is an annular groove of an open-loop structure, and rectangular grooves connected to the annular groove are respectively arranged at both ends of the annular groove of the open-loop structure, so as to realize that the fluid to be measured flows into the annular groove from the rectangular groove on one side and flows out from the rectangular groove on the other side.

[0024] The upper substrate 1, the intermediate flexible substrate 2 and the lower substrate 3 of the present invention are all rectangular structures, and the upper substrate 1, the intermediate flexible substrate 2 and the lower substrate 3 are fixed by a nylon button combination; the metal copper-plated patch is composed of a circular metal patch and a rectangular metal microstrip line radially connected to the outside of the circular metal patch, and the circular patch antenna formed by the metal copper-plated patch has three resonant frequencies, and the thickness of the metal copper-plated patch is 0.035mm; the material of the upper substrate 1 and the lower substrate 3 are both epoxy resin, 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 66mm, and the thickness of the upper substrate 1 and the lower substrate 3 is 0.4mm; the material of the intermediate flexible substrate 2 is polydimethylsiloxane, the dielectric constant of the material is 2.65, and the intermediate flexible substrate The length and width of the board 2 are both 66mm, the thickness of the middle flexible substrate 2 is 0.5mm, the width of the annular groove and the rectangular groove are both 2mm, and the depth of the annular groove and the rectangular groove are both 0.3mm; the material of the copper-plated floor is copper, and the thickness of the copper-plated floor is 0.035mm; the upper substrate 1, the middle flexible substrate 2 and the lower substrate 3 are all rectangular structures, and connecting holes are respectively provided at the corners of the upper substrate 1, the middle flexible substrate 2 and the lower substrate 3, and the upper substrate 1, the middle flexible substrate 2 and the lower substrate 3 are sequentially superimposed and combined and connected and fixed by nylon buttons matching the connecting holes; the width of the rectangular metal microstrip line is 1.9mm, the length of the rectangular metal microstrip line is 7mm, the device uses a rectangular metal microstrip line feeding method, and the impedance of the feeding input port is 50Ω.

[0025] The principle of the present invention is as follows:

[0026] The present invention mainly performs sensing detection on trace liquid samples of grease, and utilizes the electromagnetic field generated by the patch antenna to be extremely sensitive to the change of the dielectric constant of the liquid being measured in the microfluidic channel, thereby realizing quantitative detection of grease liquid samples.

[0027] When in use, the liquid to be tested is pumped into the microfluidic channel by a peristaltic pump, and microwaves are incident on the sensor of the present invention perpendicularly to the upper substrate, so that the quality of the liquid to be tested can be detected. Since the microfluidic channel is directly below the circular antenna, the liquid to be tested is completely in a strong electric field, which enhances the sensitivity of the sensor.

[0028] 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, thereby minimizing the error. At the same time, the sensor can be reused, the operation is simple, and if the microfluidic channel of the sensor is damaged, it can be replaced.

[0029] In this specific implementation, the sensitivity of the sensor in the present invention is verified by using ANSYS High Frequency Structure Simulator (HFSS). Figure 4This is a S11 characteristic diagram of the triple-resonance microfluidic sensor provided by the present invention. It can be seen from the diagram that the sensor of the present invention has three resonant frequencies, and the resonant frequencies are respectively around 3.3 GHz, 4.4 GHz and 5.4 GHz.

[0030] Figure 5 , Figure 6 and Figure 7 The microfluidic sensor provided by the present invention simulates the detection result diagrams of different dielectric constants and resonant frequency offsets, which are the first, second and third resonant frequency offset result diagrams respectively.

[0031] The present invention has the following beneficial effects: (1) The present invention etches the microfluidic channel on the intermediate 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 as a resonance unit, which enhances the electric field strength around the circular channel, 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 to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the scope of the principles of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A triple-resonance microfluidic sensor, characterized in that The invention comprises an upper substrate, an intermediate flexible substrate and a lower substrate which are arranged in sequence from top to bottom, wherein a metal copper-plated patch is attached to the upper surface of the upper substrate, the metal copper-plated patch is composed of a circular metal patch connected with a rectangular metal microstrip line, the end of the rectangular metal microstrip line is welded with an SMA connector, and the SMA connector is connected with 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 intermediate flexible substrate, the microfluidic channel is arranged below the circular metal patch, and is used to obtain an optimal electric field strength, the main body of the microfluidic channel is an annular groove of an open-loop structure, and rectangular grooves connected to the annular groove are respectively arranged at both ends of the annular groove of the open-loop structure, so as to realize that the fluid to be tested flows into the annular groove from the rectangular groove on one side and flows out from the rectangular groove on the other side, the upper substrate, the intermediate flexible substrate and the lower substrate are all rectangular structures, and the upper substrate, the intermediate flexible substrate and the lower substrate are connected by a nylon button assembly The metal copper-plated patch is composed of a circular metal patch and a rectangular metal microstrip line radially connected to the outside of the circular metal patch. The circular patch antenna formed by the metal copper-plated patch has three resonant frequencies. The thickness of the metal copper-plated patch is 0.035 mm. 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 66 mm, and the thickness of the upper substrate and the lower substrate is 0.4 mm. The material of the intermediate flexible substrate is polydimethylsiloxane, the dielectric constant of the material is 2.65, the length and width of the intermediate flexible substrate are both 66 mm, the thickness of the intermediate flexible substrate is 0.5 mm, the width of the annular groove and the rectangular groove are both 2 mm, and the depth of the annular groove and the rectangular groove are both 0.3 mm. The width of the rectangular metal microstrip line is 1.9 mm, and the length of the rectangular metal microstrip line is 7 mm.

2. The triple-resonance microfluidic sensor according to claim 1, characterized in that: The copper-plated floor is made of copper, and the thickness of the copper-plated floor is 0.035 mm.

3. The triple-resonance microfluidic sensor according to claim 1, characterized in that: The upper substrate, the middle flexible substrate and the lower substrate are all rectangular structures, and connection holes are respectively provided at the corners of the upper substrate, the middle flexible substrate and the lower substrate. The upper substrate, the middle flexible substrate and the lower substrate are sequentially stacked and combined and connected and fixed by nylon buttons matching the connection holes.

4. The triple-resonance microfluidic sensor according to claim 1, characterized in that: The triple-resonance microfluidic sensor uses a rectangular metal microstrip line feeding method, and the impedance of the feeding input port is 50Ω.

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