Method for measuring gas velocity using a gas flow sensor based on graphene oxide thin film

Abstract

This invention belongs to the field of sensor technology and discloses a method for measuring gas flow velocity using a gas flow sensor based on a graphene oxide thin film. The gas flow sensor includes a substrate and electrodes and a graphene oxide thin film that are in contact with each other disposed on the substrate. The electrodes include a source electrode and a drain electrode. The gas flow sensor of this invention utilizes the reversible adsorption-desorption property of water molecules in graphene oxide to achieve a dramatic change in conductivity induced by airflow, thus endowing the sensor with ultra-high sensitivity and a wide detection range.

Description

Technical Field

[0001] This invention relates to the field of semiconductor sensor technology, and in particular to a method for measuring gas flow rate using a gas flow sensor based on graphene oxide thin film. Background Technology

[0002] Airflow sensors are core sensing devices that convert parameters such as airflow velocity, flow rate, and pressure into measurable electrical signals. They are widely used in traditional fields such as industrial automation, automotive electronics, aerospace, medical equipment, and smart homes, and also have broad application prospects in emerging fields such as smart skin and wearable electronic devices. With the rapid development of nanotechnology, there is an urgent need for the miniaturization and integration of airflow sensors. Existing airflow sensors not only suffer from problems such as susceptibility to interference and insufficient response speed, but also have complex structures and high costs, making it difficult to meet the core requirements of miniaturization and low power consumption in emerging fields. Graphene oxide is an atomic-layer material with a surface rich in oxygen-containing functional groups, possessing advantages such as high specific surface area, excellent flexibility, and good biocompatibility. Utilizing the reversible water molecule adsorption energy of graphene oxide can effectively achieve ultra-high sensitivity, fast response, and wide detection range in airflow sensors. Summary of the Invention

[0003] The purpose of this invention is to address the technical deficiencies in the prior art by providing a method for measuring gas flow rate using an airflow sensor based on graphene oxide thin film.

[0004] The technical solution adopted to achieve the purpose of this invention is: A method for measuring gas flow velocity using a gas flow sensor based on graphene oxide thin film, wherein: The airflow sensor includes a substrate and electrodes and a graphene oxide film disposed on the substrate in contact with each other, the electrodes including a source electrode and a drain electrode; The method for measuring gas flow rate includes the following steps: Step 1: Connect the source electrode and drain electrode of the airflow sensor to the probe of the semiconductor characteristic analysis system. Connect the air valve and the glass rotor flow meter through the air tube. Target the output gas to the airflow sensor. Control the gas flow rate through the glass rotor flow meter. Record the corresponding electrical signals by passing different known gas flow rates through the airflow sensor. Plot a standard curve with the gas flow rate and electrical signal as the horizontal and vertical axes, respectively. Step 2: Pass the gas to be tested through the airflow sensor, measure the corresponding electrical signal, substitute the electrical signal into the standard curve, and read the corresponding flow rate, i.e., the flow rate of the gas to be tested.

[0005] In the above technical solution, the electrical signal is resistance, voltage, or current.

[0006] In the above technical solution, in the airflow sensor, the source electrode and the drain electrode are located between the substrate and the graphene oxide film.

[0007] In the above technical solution, in the airflow sensor, the source electrode and the drain electrode are located on the upper surface of the graphene oxide film.

[0008] In the above technical solution, the substrate of the airflow sensor is made of heavily doped silicon wafer, quartz glass, PDMS or SEBS, the source electrode and drain electrode are made of chromium, silver, aluminum or gold, the thickness of the source electrode and drain electrode is 20-30 nm, and the thickness of the graphene oxide film is 1-40 nm.

[0009] In the above technical solution, the airflow sensor is prepared through the following steps: Step S1: Pattern the source electrode and drain electrode on the substrate; Step S2: Treat the substrate surface with oxygen plasma; Step S3: Construct a graphene oxide film on the substrate.

[0010] In the above technical solution, the airflow sensor is prepared through the following steps: Step (1): The substrate surface is treated with oxygen plasma; Step (2): Construct a graphene oxide film on the substrate; Step (3): The source electrode and the drain electrode are patterned on the graphene oxide film.

[0011] In the above technical solution, the source electrode and the drain electrode are deposited by vapor deposition, and the vapor deposition rate is 0.01 to 0.1 Å / s.

[0012] In the above technical solution, when oxygen plasma is used to treat the substrate surface, the power of the oxygen plasma is 30-100W and the treatment time is 1-10min.

[0013] In the above technical solution, the method for constructing the graphene oxide film is as follows: using a 2.5~5 mg / mL graphene oxide aqueous dispersion as raw material, the graphene oxide film is constructed by spin coating, solution shearing, spraying, dipping or dripping.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. The airflow sensor based on graphene oxide film provided by the present invention uses graphene oxide aqueous dispersion as raw material and prepares the film using a solution method. The raw material is readily available, the processing is simple, and it is compatible with flexible substrates. 2. The oxygen-containing functional groups grafted onto the surface and edges of the graphene oxide film provide numerous sites for water molecule adsorption. The airflow sensor of this invention achieves electrical signal output through reversible water molecule adsorption. In a static environment, the oxygen-containing functional groups such as hydroxyl and carboxyl groups on the surface of graphene oxide adsorb environmental water molecules, forming an "electron transport bridge." When airflow occurs, it carries away the adsorbed water molecules, disrupting the "conductive bridge" and causing a sharp decrease in conductivity (by several orders of magnitude). After the airflow is turned off, the graphene oxide re-adsorbs water molecules, and its performance is reversibly restored. 3. The airflow sensor of this invention utilizes the reversible adsorption-desorption property of water molecules in graphene oxide to achieve a dramatic change in conductivity induced by airflow, thus endowing the sensor with ultra-high sensitivity (detection limit as low as 0.2 mm·s). -1 It features a sensory sensitivity far below the limits of human skin perception, a rapid response (≈1s), and a wide detection range (0.2mm·s). -1 ~590cm・s -1 The characteristics of ); 4. Thanks to the low cost, easy processing, light weight, flexibility, and biocompatibility of graphene oxide, the technology of this invention has broad application prospects in the fields of smart skin and wearable electronic devices. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of an airflow sensor structure based on graphene oxide film.

[0016] In the figure: 1-substrate, 2-source electrode, 3-drain electrode, 4-graphene oxide film.

[0017] Figure 2 This is a test diagram showing the sensing characteristics of an airflow sensor based on graphene oxide film for airflow at different velocities.

[0018] Figure 3 This is a test graph showing the sensing characteristics of an airflow sensor based on graphene oxide film at the same flow rate (590 cm / s).

[0019] Figure 4 This is a test graph showing the sensing characteristics of an airflow sensor based on graphene oxide film for the same flow rate (0.2 mm / s). Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0021] The sources of the medicines used in the following examples are as follows: Aqueous dispersion of monolayer graphene oxide, monolayer ratio: >99%, source: Hangzhou Gaoxi Technology Co., Ltd.

[0022] Example 1 Build as Figure 1 The airflow sensor structure shown includes a substrate 1, a source electrode 2 and a drain electrode 3 disposed on the upper surface of the substrate, and a graphene oxide film 4 located on the upper surface of the substrate 1 and covering the source electrode 2 and the drain electrode 3. The source electrode 2 and the drain electrode 3 can be located above or below the graphene oxide film 4, as long as they are in contact.

[0023] The method for preparing the airflow sensor includes the following steps: Step S1: Pattern the source electrode and drain electrode on the substrate. Flexible or rigid substrates can be selected. In this embodiment, a 500µm thick heavily doped silicon wafer is used as the substrate, with a 300nm thick layer of naturally oxidized silicon dioxide on the surface. Alternatively, any commercially available or literature-reported substrate can be used.

[0024] Patterned fabrication of source and drain electrodes: In this embodiment, a 20 nm thick chromium source and drain electrode is deposited on the substrate surface covering the mask using a vapor deposition method at a deposition rate of 0.05 Å / s. There are no restrictions on the patterning method, including the shape of the source and drain electrodes and the distance between them.

[0025] Step S2: The surface of the substrate is treated with oxygen plasma, wherein the power of the oxygen plasma is 30W and the treatment time is 5min.

[0026] Step S3: Construct a graphene oxide film on the substrate. The construction method includes, but is not limited to, traditional and commonly used commercial methods for preparing thin films, such as spin coating, solution shearing, spraying, dip coating, and drop casting. The thickness of the graphene oxide film is between 1 and 40 nm.

[0027] The following examples illustrate the construction methods of graphene oxide films: (1) A graphene oxide aqueous dispersion with a concentration of 5 mg / mL was spin-coated onto the substrate surface at a speed of 2000 rpm for 60 s, resulting in a graphene oxide film with a thickness of 30 nm. (2) A graphene oxide aqueous dispersion with a concentration of 2.5 mg / mL was deposited on the substrate surface by solution shearing at a shear rate of 0.5 mm / s to obtain a graphene oxide film with a thickness of 20 nm.

[0028] The principle of measuring gas flow velocity using the aforementioned airflow sensor is as follows: The source and drain electrodes of the airflow sensor are electrically connected to the probe of the semiconductor characteristic analysis system. The air valve and glass rotor flow meter are connected by an air tube, so that the gas to be tested passes through the airflow sensor. The sensing performance is tested by changing the gas flow rate input to the airflow sensor.

[0029] This sensor is suitable for almost all common gases, including but not limited to air, oxygen, nitrogen, argon, and methane.

[0030] The method for measuring gas flow velocity using the aforementioned airflow sensor includes the following steps: Step 1: Connect the source electrode and drain electrode of the airflow sensor to the probe of the semiconductor characteristic analysis system. Connect the air valve and the glass rotor flow meter through the air tube. Target the output gas to the airflow sensor. Control the gas flow rate through the glass rotor flow meter. Record the corresponding electrical signals by passing different known gas flow rates through the airflow sensor. Plot a standard curve with the gas flow rate and electrical signal as the horizontal and vertical axes, respectively. Step 2: Pass the gas to be tested through the airflow sensor, measure the corresponding electrical signal, substitute the electrical signal into the standard curve, and read the corresponding flow rate, i.e., the flow rate of the gas to be tested.

[0031] In this embodiment, the flow rate v Defined as V / S ,in V For input gas flow rate, S This refers to the cross-sectional area of ​​the gas tube. The output gas flow rate is changed by rotating the regulating valve of the glass rotor flowmeter, according to... S and V Calculations can yield the following results: Figure 2 The different gas flow rates shown (flow velocity) v The sensor characteristics test graph (2.6~472 cm / s) is shown. The resistance value can be obtained based on the current and applied voltage at different gas flow rates, and then a standard curve can be fitted. Next, gas with an unknown flow rate is passed through the gas flow sensor, the corresponding resistance value is calculated, and the gas flow rate can be read by substituting it into the curve.

[0032] When using a 6mm diameter endotracheal tube to deliver a flow rate of 10L / min, the following can be obtained: Figure 3 shown v The sensor characteristic test chart shows a velocity of 590 cm / s. The magnified view also shows a response time of <1 s. When using a 20 mm diameter tubing to deliver a flow rate of 4 mL / min, the following results can be obtained: Figure 4 shown v Sensing characteristic test chart with a speed of 0.2 mm / s.

[0033] Sensitivity calculation instructions: Sensitivity is defined as ( X - X min ) / X min ,in X To detect the output resistance value of the sensor when airflow passes through, Xmin This represents the resistance value output by the sensor when there is no airflow. The sensitivity is calculated using the device's resistance as the output signal. Based on... Figure 3 The flow velocity can be calculated v At a speed of 590 cm / s, the device's sensitivity can reach 10. 4 .according to Figure 4 It is evident that this sensor still exhibits significant signal changes even with extremely weak airflow (0.2 mm / s).

[0034] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for measuring gas flow velocity using a gas flow sensor based on a graphene oxide thin film, the gas flow sensor comprising a substrate and electrodes and a graphene oxide thin film disposed on the substrate in contact with each other, the electrodes comprising a source electrode and a drain electrode, characterized in that, The method includes the following steps: Step 1: Connect the source electrode and drain electrode of the airflow sensor to the probe of the semiconductor characteristic analysis system. Connect the air valve and the glass rotor flow meter through the air tube. Target the output gas to the airflow sensor. Control the gas flow rate through the glass rotor flow meter. Record the corresponding electrical signals by passing different known gas flow rates through the airflow sensor. Plot a standard curve with the gas flow rate and electrical signal as the horizontal and vertical axes, respectively. Step 2: Pass the gas to be tested through the airflow sensor, measure the corresponding electrical signal, substitute the electrical signal into the standard curve, and read the corresponding flow rate, i.e., the flow rate of the gas to be tested.

2. The method for measuring gas flow velocity using a gas flow sensor based on graphene oxide thin film as described in claim 1, characterized in that, The electrical signal is resistance, voltage, or current.

3. The method for measuring gas flow velocity using a gas flow sensor based on graphene oxide thin film as described in claim 1, characterized in that, In the airflow sensor, the source electrode and the drain electrode are located between the substrate and the graphene oxide film.

4. The method for measuring gas flow velocity using a gas flow sensor based on graphene oxide thin film as described in claim 1, characterized in that, In the airflow sensor, the source electrode and the drain electrode are located on the upper surface of the graphene oxide film.

5. The method for measuring gas flow velocity using a gas flow sensor based on graphene oxide thin film as described in claim 1, characterized in that, The substrate is made of heavily doped silicon wafer, quartz glass, PDMS or SEBS, the source electrode and drain electrode are made of chromium, silver, aluminum or gold, the thickness of the source electrode and drain electrode is 20-30 nm, and the thickness of the graphene oxide film is 1-40 nm.

6. The method for measuring gas flow velocity using a gas flow sensor based on graphene oxide thin film as described in claim 1, characterized in that, The airflow sensor is prepared by the following steps: Step S1: Pattern the source electrode and drain electrode on the substrate; Step S2: Treat the substrate surface with oxygen plasma; Step S3: Construct a graphene oxide film on the substrate.

7. The method for measuring gas flow velocity using a gas flow sensor based on graphene oxide thin film as described in claim 1, characterized in that, The airflow sensor is prepared by the following steps: Step (1): The substrate surface is treated with oxygen plasma; Step (2): Construct a graphene oxide film on the substrate; Step (3): The source electrode and the drain electrode are patterned on the graphene oxide film.

8. The method for measuring gas flow velocity using a gas flow sensor based on graphene oxide thin film as described in claim 6 or 7, characterized in that, The source and drain electrodes were deposited by vapor deposition at a rate of 0.01–0.1 Å / s.

9. The method for measuring gas flow velocity using a gas flow sensor based on graphene oxide thin film as described in claim 6 or 7, characterized in that, When oxygen plasma is used to treat the substrate surface, the power of the oxygen plasma is 30-100W and the treatment time is 1-10 minutes.

10. The method for measuring gas flow velocity using a gas flow sensor based on graphene oxide thin film as described in claim 6 or 7, characterized in that, The method for constructing graphene oxide films is as follows: using a 2.5~5 mg / mL graphene oxide aqueous dispersion as raw material, the graphene oxide film is constructed by spin coating, solution shearing, spraying, dip coating or drop casting.

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