A low dielectric constant filter membrane based on biological enzymes, its preparation method and application

Abstract

The present invention discloses a low dielectric constant filter membrane based on biological enzymes. The preparation method includes drying the low dielectric constant filter membrane, dropping biological enzymes onto the surface of the dried filter membrane and then freeze-drying. After the moisture has completely evaporated, the low dielectric constant filter membrane based on biological enzymes is obtained. At the same time, the present invention also discloses the application of the low dielectric constant filter membrane based on biological enzymes in a waveguide gas sensor. After fixing the low dielectric constant filter membrane based on biological enzymes on the resonance window of the resonator in the waveguide gas sensor, the sensor is assembled and tested. By using a filter membrane with a small volume that is convenient for installation and disassembly, the present invention is conducive to repeatedly testing the same sample multiple times, has good reusability, and the low dielectric constant filter membrane based on biological enzymes has good air permeability, which can enable the enzymes to fully contact with the gas, further improving the sensitivity of the sensor.

Description

Technical Field

[0001] This invention relates to the field of waveguide gas sensors, specifically to a low dielectric constant filter membrane based on biological enzymes, its preparation method, and its application. Background Technology

[0002] Currently, most microwave gas sensors use planar circuits, which offer advantages such as small size, simple fabrication, and low cost. However, electric and magnetic fields are often intertwined in planar circuits, and the quality factor and electromagnetic field strength are limited by the planar circuit structure. The three-dimensional structure of waveguide cavities can transmit TE and TM modes, effectively separating the concentrated electric and magnetic field regions. This results in a significantly higher quality factor than planar circuits, greatly improving the sensitivity of microwave sensors.

[0003] Currently, waveguide structure sensors are mainly used for non-destructive testing and imaging of objects, surface crack detection, thickness measurement, humidity detection, and dielectric constant detection. In the field of gas sensors, there is considerable research on optical waveguide gas sensors; however, optical waveguide testing systems are complex, with high instrument and manufacturing costs, and are easily affected by environments where light propagation is limited. Regarding microwave waveguide gas sensors, only JL Jordan et al. have proposed using a waveguide cavity structure in the microwave band to sense SO2 to date, but this sensor does not contain sensitive materials and has limited sensitivity and a low detection limit.

[0004] Currently, most bio-enzyme sensors are electrochemical sensors, and the most common enzyme immobilization method is to fix the enzyme onto the electrode using physical or chemical methods. There is currently no precedent for combining bio-enzymes with waveguides to create microwave gas sensors. The three-dimensional waveguide cavity structure is relatively large, with the sensitive area concentrated in the center of the cavity, making it impossible to directly immobilize the enzyme in the sensitive area, and lacking a fixation position similar to that of electrochemical sensors.

[0005] Currently, bioenzymes are widely used in electrochemical and resistive sensors. However, due to the special cavity structure of waveguide cavities, they cannot be directly used, rendering all gas-sensitive bioenzymes useless in waveguides. Furthermore, methods for immobilizing enzymes in electrochemical sensors also have many shortcomings. Since the enzymes used in gas biosensors are not in their natural environment, they are often unstable due to changes in environmental conditions. If naked enzymes (enzymes not immobilized in the material) are modified on the electrode surface, the enzyme loading capacity decreases, leading to reduced enzyme activity. In addition, the electron transfer efficiency between the enzyme and the electrode also decreases. Introducing binding materials during enzyme immobilization can block gas adsorption. Currently used sample tubes for waveguide cavity testing also have many drawbacks. First, their high dielectric constant significantly affects electromagnetic fields, reducing the sensitivity of the material to electromagnetic fields. Second, liquid bioenzymes cannot be directly placed in the sample tubes. Third, the large volume and poor permeability of the sample tubes greatly reduce the contact area between the enzyme and the sensitive gas, weakening the gas-sensing performance. Summary of the Invention

[0006] This invention designs and develops a low dielectric constant filter membrane based on biological enzymes. The purpose of this invention is to solve the problem in the prior art that biological enzymes cannot be fixed in the sensitive area of ​​the waveguide cavity.

[0007] This invention designs and develops a method for preparing low dielectric constant filter membranes based on biological enzymes. The purpose of this invention is to solve the problem of preparing low dielectric constant filter membranes based on biological enzymes.

[0008] The present invention also relates to the application of a low dielectric constant filter membrane based on biological enzymes. The present invention solves the problem in the prior art that biological enzymes cannot be used in waveguide cavities to realize gas detection using enzyme microwave sensors.

[0009] The technical solution provided by this invention is as follows:

[0010] A method for preparing a low dielectric constant filter membrane based on bio-enzymes includes: drying the low dielectric constant filter membrane, dropping bio-enzymes onto the surface of the dried filter membrane, cooling it, and obtaining the low dielectric constant filter membrane based on bio-enzymes after the moisture has completely evaporated.

[0011] Preferably, the low dielectric constant filter membrane is dried at 60°C.

[0012] Preferably, the bio-enzyme is dropped onto the dried filter membrane surface and then cooled for 24 hours.

[0013] Preferably, the bioenzyme is porcine pancreatic enzyme, alcohol dehydrogenase, secondary alcohol dehydrogenase, ethanol oxidase, or peroxidase.

[0014] Preferably, the low dielectric constant filter membrane is a quartz fiber filter membrane, paraffin wax, or molecular sieve.

[0015] Preferably, the bio-enzyme is a solution containing 2.5 g / L trypsin in an HBSS solution containing phenol red, and 20 μl to 60 μl is added dropwise to the surface of the filter membrane in multiple portions.

[0016] Preferably, the low dielectric constant filter membrane is cut into 0.9cm × 0.9cm squares and then dried.

[0017] A low dielectric constant filter membrane based on a biological enzyme is prepared using the aforementioned method for preparing a low dielectric constant filter membrane based on a biological enzyme.

[0018] An application of a low dielectric constant filter membrane based on bio-enzymes in a waveguide gas sensor: After fixing the low dielectric constant filter membrane based on bio-enzymes into the resonant window of the waveguide gas sensor, the sensor is assembled and tested.

[0019] Preferably, the waveguide cavity in the waveguide gas sensor is a rectangular waveguide cavity, a cylindrical waveguide cavity, or an annular cavity.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. The low dielectric constant filter membrane based on biological enzymes provided by this invention has little effect on the electromagnetic field of the waveguide. By using a filter membrane that is small in size and easy to install and remove, it is beneficial to repeatedly test the same sample and has good reusability.

[0022] 2. The low dielectric constant filter membrane based on biological enzymes provided by this invention can be weighed, thus allowing for the weighing and control of the quality of the coated sample, which is beneficial for variable control.

[0023] 3. The method for preparing a low dielectric constant filter membrane based on biological enzymes provided by the present invention can load biological enzymes by drop coating, so that the biological enzymes can be combined with waveguides to form a microwave gas sensor.

[0024] 4. The low dielectric constant filter membrane based on biological enzymes provided by this invention has good air permeability, which allows the enzyme to fully contact the gas, thereby further improving the sensitivity of the sensor. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the waveguide gas sensor structure using a rectangular waveguide resonant cavity as described in this invention.

[0026] Figure 2 This is a schematic diagram of the waveguide gas sensor structure using a rectangular waveguide resonant cavity as described in this invention.

[0027] Figure 3This is a digital photograph of the resonant plate with the biological enzyme-loaded filter membrane described in this invention.

[0028] Figure 4 This is a schematic diagram of the response curve of the porcine pancreatic enzyme-based quartz fiber filter membrane to ethanol at room temperature, prepared according to Example 1 of the present invention.

[0029] Figure 5 This is a schematic diagram of the response curve of the porcine pancreatic enzyme-based quartz fiber filter membrane to ethanol at room temperature, prepared according to Example 2 of the present invention.

[0030] Figure 6 This is a schematic diagram of the response curve of the porcine pancreatic enzyme-based quartz fiber filter membrane to ethanol at room temperature, prepared according to Example 3 of the present invention. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0032] This invention provides a method for preparing a low dielectric constant filter membrane based on biological enzymes, specifically including the following steps:

[0033] Step 1: Cut the low dielectric constant filter membrane into 0.9cm × 0.9cm rectangular pieces and dry them in an oven at 60℃ for later use.

[0034] Step 2: Use a pipette to repeatedly drop a fixed amount of biological enzyme liquid onto the fiber surface of the low dielectric constant filter membrane, and place it in a refrigerator to air dry for 24 hours.

[0035] Step 3: After the water has completely evaporated, the bio-enzyme attaches to the fiber to obtain a low dielectric constant filter membrane based on the bio-enzyme.

[0036] In another embodiment, the low dielectric constant filter membrane is a quartz fiber filter membrane, paraffin wax, or molecular sieve.

[0037] In another embodiment, the bioenzyme is porcine pancreatic enzyme, alcohol dehydrogenase, secondary alcohol dehydrogenase, ethanol oxidase, or peroxidase; as a preferred embodiment, the bioenzyme is a solution containing 2.5 g / L porcine pancreatic enzyme in an HBSS solution containing phenol red, and 20 μl to 60 μl is added dropwise to the surface of the filter membrane in multiple portions.

[0038] This invention also provides a low-dielectric-constant filter membrane based on biological enzymes, prepared using the above-described method. This invention utilizes a low-dielectric-constant filter membrane chip to drop-coat biological enzymes onto the membrane surface. Simply placing the filter membrane in the sensitive area of ​​the waveguide cavity solves the problem of enzyme loading limitations, simplifying the sensing system. The filter membrane is an ideal choice for carrying biological enzymes, combining with the waveguide cavity, and used for gas sensing. The three-dimensional structure of the waveguide cavity itself provides a closed atmosphere, further simplifying the testing system. Simultaneously, the low dielectric constant of the quartz fiber filter membrane minimizes its impact on the electromagnetic field of the waveguide. The small size and ease of installation and removal facilitate repeated testing of the same sample, resulting in good reusability. Furthermore, the coating method of the quartz fiber filter membrane can immobilize biological enzymes, solving the problem of waveguides being unable to immobilize enzymes. The excellent permeability of the filter membrane allows gas molecules to fully contact the enzymes, further improving the sensor's sensitivity.

[0039] The present invention also provides an application of a low dielectric constant filter membrane based on bio-enzymes in a waveguide gas sensor. The low dielectric constant filter membrane coated with bio-enzymes is fixed in the strong electric field region in the middle of the resonant window of the resonant plate in the waveguide gas sensor, and the sensor is assembled for testing.

[0040] In another embodiment, the waveguide cavity in the waveguide gas sensor is a rectangular waveguide cavity, a cylindrical waveguide cavity, or an annular cavity.

[0041] like Figure 1 , Figure 2 , Figure 3 As shown, this invention employs a rectangular waveguide resonant cavity waveguide gas sensor. The rectangular waveguide is a standard straight waveguide made of aluminum and without a coating. Two conductive metal housings 110 are coaxially arranged and have an axially penetrating waveguide cavity 111. The metal housings 110 do not absorb electromagnetic waves but only reflect them. An air inlet is formed on the outer surface of the cavity of the metal housing 110. The air inlet is connected to a glass tube 112 using hot melt adhesive to ensure its airtightness. A rubber hose is attached to the end of the glass tube 112. A window 121 of a specific size is fabricated on a flange (made of copper) to serve as a resonator 120. The two ends of the resonator 120 are fixedly connected to the ports of the metal casing 110. A low dielectric constant filter membrane 200 based on bio-enzymes is placed at the window 121. The resonator 120 is sandwiched between two identical waveguide cavities 111. The low dielectric constant filter membrane 200 based on bio-enzymes can adsorb gas and seal the ports of the metal casing 110, forming a closed cavity inside the entire device. A wave converter 130 is fixedly connected to the outer ports of the two metal casings 110. The two sides of the waveguide cavity 111 are connected to a vector network analyzer through ports 131 on the wave converter 130 and coaxial cables to perform real-time testing of the microwave signals transmitted in the waveguide cavity 111.

[0042] Example 1

[0043] The invention provides a method for preparing a low dielectric constant filter membrane based on biological enzymes, specifically including the following steps:

[0044] Step 1: Cut the quartz fiber filter membrane into 0.9cm × 0.9cm rectangular pieces and dry them in an oven at 60℃ for later use.

[0045] Step 2: Using a pipette, repeatedly drop 20 μl of porcine pancreatic enzyme liquid onto the fiber surface of a low dielectric constant filter membrane, and place it in a refrigerator to air dry for 24 hours.

[0046] Step 3: After the water has completely evaporated, the bio-enzyme attaches to the fiber to obtain a quartz fiber filter membrane based on porcine pancreatic enzyme.

[0047] Example 2

[0048] The invention provides a method for preparing a low dielectric constant filter membrane based on biological enzymes, specifically including the following steps:

[0049] Step 1: Cut the quartz fiber filter membrane into 0.9cm × 0.9cm rectangular pieces and dry them in an oven at 60℃ for later use.

[0050] Step 2: Using a pipette, repeatedly drop 40 μl of porcine pancreatic enzyme liquid onto the fiber surface of a low dielectric constant filter membrane, and place it in a refrigerator to air dry for 24 hours.

[0051] Step 3: After the water has completely evaporated, the bio-enzyme attaches to the fiber to obtain a quartz fiber filter membrane based on porcine pancreatic enzyme.

[0052] Example 3

[0053] The invention provides a method for preparing a low dielectric constant filter membrane based on biological enzymes, specifically including the following steps:

[0054] Step 1: Cut the quartz fiber filter membrane into 0.9cm × 0.9cm rectangular pieces and dry them in an oven at 60℃ for later use.

[0055] Step 2: Using a pipette, repeatedly drop 60 μl of porcine pancreatic enzyme liquid onto the fiber surface of a low dielectric constant filter membrane, and place it in a refrigerator to air dry for 24 hours.

[0056] Step 3: After the water has completely evaporated, the bio-enzyme attaches to the fiber to obtain a quartz fiber filter membrane based on porcine pancreatic enzyme.

[0057] Test case

[0058] The BJ32 waveguide (QWS-284-100) conforms to the national standard and has a strength of σ = 3.816107 S·m. -1Its operating frequency range is 2.60-3.95 GHz. The air inlet is integrated into the cavity surface and carefully sealed to the glass tube with hot melt adhesive to ensure airtightness. The end of the glass tube is connected to a rubber tube. The sealed measuring unit has a gas outlet on the opposite side.

[0059] The porcine pancreatic enzyme-based quartz fiber filter membranes prepared in Examples 1, 2, and 3 were securely fixed to the resonant window, and then the resonant plate was carefully clamped between two identical rectangular waveguides. A waveform converter and coaxial cable were used to connect both sides of the waveguide cavity to a vector network analyzer (VNA, Anritsu MS46122B) to measure the transmitted microwave signal in real time. The rectangular waveguide cavity was seamlessly connected to the VNA via input and output transmission lines. During measurement, the microwave transmission signal of the waveguide resonator was recorded by a laptop computer. A microwave gas sensing system was constructed using the above operations. All gas sensing tests were performed at room temperature (25°C) and 1 atm using the assembled microwave sensing system. Ethanol gas ranging from 10 ppb to 500 ppm was injected into the waveguide through the gas inlet. Subsequently, based on the response signal (especially S...), the signal was measured... 22 The gas sensing response is calculated. Therefore, the gas sensitivity is precisely defined as:

[0060] Response = S 22 air -S 22 gas

[0061] like Figure 4 , Figure 5 , Figure 6 As shown, with the increase of ethanol concentration, the sensor response (defined as S) increases. 22 air -S 22 gas The response of the porcine pancreatic enzyme microwave gas sensor increases linearly with increasing contact with gas molecules, indicating that the sensor can sensitively detect ethanol gas in a wide range of 10 ppb-500 ppm at room temperature. The sensor exhibits a high response of 1.14 in 500 ppm ethanol gas. The response increases rapidly with increasing contact between the porcine pancreatic enzyme and gas molecules, showing a good linear relationship. The porcine pancreatic enzyme microwave gas sensor material has a low detection limit (10 ppb) and a wide detection range (10 ppb-500 ppm), demonstrating the significant advantages of waveguide resonant cavity structure and enzyme-loaded quartz fiber chip in developing high-performance microwave gas sensors. This sensor ushers in a new era of gas-sensitive detection combining microwave sensors and biological enzymes.

[0062] This invention is the first to combine biological enzymes with waveguide structures to obtain a microwave gas sensor with high sensitivity, low detection limit, and wide detection range, which can replace expensive optical waveguides for gas sensing. Due to the characteristics of biological enzymes, it is difficult to place them directly inside the waveguide for detection. However, biological enzymes can be loaded onto a quartz fiber filter membrane by drop coating or other methods. The filter membrane is then attached to the location where the electromagnetic field of the resonant plate is concentrated, and the resonant plate is directly placed inside the waveguide cavity. This greatly improves the reconfigurability of the sensor: that is, different types of biological enzymes can be used to detect different target gases.

[0063] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a low dielectric constant filter membrane based on biological enzymes, characterized in that, include: After drying the low dielectric constant filter membrane, drop the bio-enzyme onto the surface of the dried filter membrane and then cool it until the moisture has completely evaporated to obtain the bio-enzyme-based low dielectric constant filter membrane. The bio-enzyme is a solution containing 2.5 g / L trypsin in an HBSS solution containing phenol red, and 20 μl, 40 μl, or 60 μl is added dropwise to the surface of the filter membrane in multiple portions. The low dielectric constant filter membrane is a quartz fiber filter membrane.

2. The method for preparing a low dielectric constant filter membrane based on biological enzymes as described in claim 1, characterized in that, The low dielectric constant filter membrane was dried at 60 °C.

3. The method for preparing a low-dielectric-constant filter membrane based on biological enzymes as described in claim 1 or 2, characterized in that, The bio-enzyme was dropped onto the dried filter membrane surface and then cooled for 24 hours.

4. The method for preparing a low dielectric constant filter membrane based on biological enzymes as described in claim 3, characterized in that, The low dielectric constant filter membrane was cut into 0.9cm × 0.9cm squares and then dried.

5. A low dielectric constant filter membrane based on biological enzymes, characterized in that, It was prepared using the method for preparing low dielectric constant filter membrane based on biological enzymes as described in any one of claims 1-4.

6. The application of a low-dielectric-constant filter membrane based on biological enzymes in a waveguide gas sensor, characterized in that, After fixing the resonant plate and resonant window in the waveguide gas sensor with the low dielectric constant filter membrane based on bio-enzymes as described in claim 5, the sensor is assembled and tested.

7. The application of the low dielectric constant filter membrane based on biological enzymes as described in claim 6 in a waveguide gas sensor, characterized in that, The waveguide cavity in the waveguide gas sensor can be a rectangular waveguide cavity, a cylindrical waveguide cavity, or an annular cavity.

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