Flexible field effect transistor for detecting dopamine in sweat and application

Abstract

The invention discloses a flexible field effect transistor for detecting dopamine in sweat and a preparation method of the flexible field effect transistor. The flexible field effect transistor is subjected to surface modification through a high-entropy Prussian blue analogue material, so that the electrochemical sensing performance of the device is remarkably improved, and the device has a relatively low detection limit and a relatively wide detection range on dopamine. The flexible field effect transistor takes polyimide as a substrate, has good flexibility and stability, and is suitable for wearable application scenes. The device is simple in structure, flexible in preparation process and suitable for mass production. The flexible field effect transistor modified based on the high-entropy Prussian blue analogue provides a new technical scheme for the flexible biosensor in the sweat detection field, and provides a new technical means for early diagnosis of diseases and personalized medical treatment.

Description

Technical Field

[0001] The present invention belongs to the fields of biosensing and flexible electronics, and particularly relates to a flexible field-effect transistor for detecting dopamine in sweat and its applications. Background Art

[0002] As a key neurotransmitter, dopamine plays a crucial role in neural signal transmission, mood regulation, motor control, and endocrine function in the human body. The concentration change of dopamine in sweat is closely related to the occurrence and development of various diseases, such as Parkinson's disease, schizophrenia, cardiovascular diseases, etc. Therefore, accurately detecting dopamine in sweat is of great significance for early disease diagnosis, disease monitoring, and personalized treatment.

[0003] However, the low concentration of dopamine in sweat poses challenges to detection. To this end, researchers have developed various highly sensitive detection methods, such as high-performance liquid chromatography, fluorescence analysis, and mass spectrometry. However, these methods still have limitations such as expensive equipment, complex operation, and long detection time. In contrast, electrochemical sensing technology has the advantages of high precision, fast response, and low cost. Among them, the ion-sensitive field-effect transistor (ISFET) has been widely used due to its high sensitivity, low power consumption, and miniaturization characteristics. However, traditional ISFETs usually use silicon substrates, and their rigidity and brittleness limit their application in flexible devices. In addition, existing ISFET devices have poor stability in complex environments, are easily affected by external interference, and are difficult to detect low-concentration dopamine in sweat, showing obvious limitations. Summary of the Invention

[0004] The present invention proposes a novel flexible field-effect transistor for detecting dopamine in sweat and its applications to address the problems existing in traditional sweat dopamine detection.

[0005] To achieve the above object, the present invention is implemented by the following technical solutions: A flexible field-effect transistor for detecting dopamine in sweat, comprising a flexible substrate and a bottom gate dielectric layer covering the flexible substrate. A source electrode and a drain electrode are provided on the bottom gate dielectric layer, and a semiconductor conductive channel is arranged between the source electrode and the drain electrode. A top gate dielectric layer is provided on the surface of the semiconductor conductive channel; A functional layer is provided on the surface of the top gate dielectric layer. The preparation steps of the functional layer are as follows: (1) Add the transition metal salt solution and the surfactant to deionized water, and stir evenly to obtain the mixed solution A; dissolve the transition metal potassium cyanide in deionized water to obtain the solution B; mix the mixed solution A and the solution B and stir evenly to carry out the synthesis reaction; after the reaction is completed, centrifuge and dry to obtain the high-entropy Prussian blue analogue powder.

[0006] (2) Disperse the high-entropy Prussian blue analogue powder in deionized water to obtain a dispersion liquid. After mixing the linking aid and the dispersion liquid, obtain the mixed solution C. Drop the mixed solution C onto the surface of the top gate dielectric layer and let it stand and dry.

[0007] Preferably, the flexible substrate material is polyimide or polydimethylsiloxane, with a thickness of 10 - 20 μm; the bottom gate dielectric layer material includes Ta2O5, with a thickness of 200 - 300 nm; the semiconductor conductive channel material is In2O3, with a thickness of 50 - 80 nm; the conductive materials of the source and drain are Cr / Au (mass ratio 1:9), with a thickness of 50 - 80 nm; the top gate dielectric layer material includes Ta2O5 or HfO2, with a thickness of 100 - 200 nm.

[0008] Preferably, the flexible substrate is prepared by spin coating, with an annealing temperature of 250 - 300 °C, an annealing atmosphere of oxygen, and an annealing time of 0.5 - 1 h; cure PDMS in an oven, with a curing temperature of 80 - 100 °C. The bottom gate dielectric layer and the top gate dielectric layer are prepared by plasma-enhanced chemical vapor deposition, with an annealing temperature of 200 - 250 °C, an annealing atmosphere of oxygen, and an annealing time of 0.5 - 1 h. The source and drain are deposited by electron beam evaporation. The preparation process is: anneal in a nitrogen atmosphere at 200 - 250 °C for 0.5 - 1 h. Deposit the conductive channel In2O3 by magnetron sputtering technology. The preparation process is to anneal in an oxygen atmosphere at 250 - 300 °C for 0.5 - 1 h.

[0009] Preferably, in the mixed solution A in step (1), the transition metal salt is one or several of FeCl2, CoCl2, NiCl2, CuCl2 or MnSO4, and the concentration of the transition metal salt solution is 1 - 50 mM; the surfactant in the mixed solution A is sodium citrate, and the concentration of the surfactant is 1 - 100 mM; the transition metal potassium cyanide in the solution B is potassium ferricyanide, and the concentration is 2 - 60 mM; the synthesis reaction time is 18 - 30 h, and the synthesis reaction temperature is 10 - 50 °C.

[0010] Preferably, in the step (2), the concentration of the dispersion liquid is 5-15 mg / mL, the linking auxiliary is a chitosan solution with a concentration of 4-8 mg / mL; in the mixed solution C, the volume of the dispersion liquid is 0.5-1.5 μL, and the volume of the chitosan solution is 0.2-0.5 μL; the static drying temperature is 20-60 °C, and the static drying time is 6-12 h. After the reaction is completed, the centrifugation speed of the suspension is 6000-8000 rpm, the drying temperature of the centrifugation product is 40-70 °C, and the drying time is 8-20 h.

[0011] The present invention provides the application of the above flexible field effect transistor in the detection of sweat dopamine.

[0012] When dopamine undergoes an oxidation reaction on the electrode surface, two hydroxyl groups (-OH) in the dopamine molecule lose electrons (oxidation) on the electrode surface and are converted into quinone groups (C=O). The two hydroxyl groups (-OH) are oxidized to two carbonyl groups (C=O) to form dopaquinone (DAQ). During the oxidation process, the dopamine molecule loses two electrons (2e⁻), and these electrons are accepted by the electrode surface, resulting in a change in the charge state of the electrode surface. The applied gate-source voltage (VGS) is a positive voltage, which is used to attract electrons and increase the carrier concentration in the channel. When dopamine is oxidized on the electrode surface, the generated electrons are accepted by the electrode surface, resulting in an increase in negative charges on the gate surface, which will offset part of the positive gate-source voltage (V GS ), which is equivalent to reducing the effective potential of the gate (V GS ), thereby weakening the ability to regulate the current in the channel. Therefore, the measured drain-source current (I DS ) becomes smaller. So the greater the dopamine concentration, the smaller the measured drain-source voltage. In the above preparation process, transition metal ions (M 2+ , etc.) and [Fe(CN)6] 3- ligands are bridged through cyano groups (CN⁻) to form a three-dimensional network structure. Sodium citrate coordinates with transition metal ions through carboxyl groups to regulate the release rate of metal ions, thereby controlling crystal growth; sodium citrate can also adsorb on the crystal surface to prevent particle aggregation and promote the formation of uniform nanoparticles, so that the flexible field effect transistor has higher sensitivity. The present invention uses a high-entropy Prussian blue analogue as the surface modification layer of the flexible field effect transistor. The high-entropy Prussian blue analogue modification layer can significantly increase the surface charge density and carrier mobility of the flexible field effect transistor, thereby enhancing the response signal to dopamine molecules and realizing specific recognition and signal amplification. In addition, by optimizing the flexible substrate material and preparation process, the flexible field effect transistor exhibits excellent stability and anti-interference ability in a complex environment and can realize rapid and accurate detection of low-concentration dopamine in sweat.

[0013] Compared with the prior art, the advantages and positive effects of the present invention are as follows: 1. In the present invention, a flexible substrate is adopted, enabling the flexible field-effect transistor to cope with various deformations such as bending and folding, adapting to diverse usage scenarios, and providing a solid foundation for the application of wearable devices.

[0014] 2. The manufacturing process flow adopted in the present invention is simple and efficient, with easy-to-operate steps, shortening the production cycle, reducing the production cost, facilitating mass production, and meeting the growing market demand for flexible field-effect transistors.

[0015] 3. The present invention prepares a high-performance flexible field-effect transistor based on a high-entropy Prussian blue analogue material, which exhibits excellent performance in the detection of dopamine in sweat. Its detection sensitivity is significantly improved, capable of accurately detecting changes in extremely low concentrations of dopamine in sweat, and having a wide detection range, providing strong technical support for early disease diagnosis, sports monitoring, and personalized medicine, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic structural diagram of the flexible field-effect transistor in Example 1.

[0017] Figure 2 It is a scanning electron microscope image of the high-entropy Prussian blue analogue powder prepared in Example 1.

[0018] Figure 3 It is a calibration curve graph of the dopamine detection concentration.

[0019] Figure 4 It is a graph of the dopamine repeatability test results of the flexible field-effect transistor.

[0020] Figure 5 It is a graph of the dopamine specificity test results of the flexible gate field-effect transistor.

[0021] The reference numerals are: 1 flexible substrate, 2 bottom gate dielectric layer, 3 source / drain, 4 semiconductor conductive channel, 5 top gate dielectric layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] In order to more clearly understand the above-mentioned objects, features, and advantages of the present invention, the present invention will be further described below with reference to specific embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0023] Many specific details are set forth in the following description in order to provide a thorough understanding of the present invention. However, the present invention can be implemented in other ways different from those described herein. Therefore, the present invention is not limited by the specific embodiments disclosed in the following specification.

[0024] Example 1 The flexible field-effect transistor structure provided in this embodiment is as follows Figure 1 shown, including a flexible substrate 1, a bottom gate dielectric layer 2, source / drain electrodes 3, a semiconductor conductive channel 4, and a top gate dielectric layer 5, which are stacked in sequence. Polyimide is used as the flexible substrate with a thickness of 11.5 μm. Polyimide is prepared by spin coating, with an annealing temperature of 250 °C, an annealing atmosphere of oxygen, and an annealing time of 1 h. The bottom gate dielectric layer Ta2O5 is deposited on the flexible substrate by plasma-enhanced chemical vapor deposition, with a thickness of 200 nm, an annealing temperature of 200 °C, an annealing atmosphere of oxygen, and an annealing time of 1 h. The conductive channel In2O3 is deposited on the bottom gate dielectric layer by magnetron sputtering, with a thickness of 50 nm, an annealing temperature of 250 °C, an annealing atmosphere of oxygen, and an annealing time of 1 h. The source and drain electrodes are deposited on the conductive channel by electron beam evaporation, with a conductive material of Cr / Au (mass ratio of 1:9) and a thickness of 50 nm, an annealing temperature of 200 °C, an annealing atmosphere of nitrogen, and an annealing time of 0.5 h. The top gate dielectric layer Ta2O5 is deposited on the conductive channel by plasma-enhanced chemical vapor deposition, with a thickness of 100 nm, an annealing temperature of 200 °C, an annealing atmosphere of oxygen, and an annealing time of 1 h.

[0025] Preparation of high-entropy Prussian blue analogue material: Prepare a transition metal salt solution composed of FeCl2, CoCl2, NiCl2, CuCl2, and MnSO4, with the concentration of each metal salt being 2 mM; then add sodium citrate to a concentration of 15 mM and stir at 200 rpm for 0.5 h to obtain solution A. Prepare an aqueous potassium ferricyanide solution with a concentration of 10 mM, denoted as solution B. Mix solution A and solution B, stir at room temperature for 1 hour at a stirring rate of 200 rpm, and then let it stand at room temperature for 18 hours for the synthesis reaction. After the reaction, centrifuge at 8000 rpm for 5 minutes, and dry the obtained solid at 60 °C for 12 hours to obtain high-entropy Prussian blue analogue powder, as Figure 2 .

[0026] Flexible field-effect transistor for dopamine detection: Disperse the high-entropy Prussian blue analogue powder in deionized water to obtain a dispersion with a concentration of 5 mg / mL. Take 0.8 μL of the dispersion and mix it with 0.3 μL of a chitosan solution with a concentration of 6 mg / mL as a linking aid, and drop the linking aid on the surface of the top gate dielectric layer of the flexible field-effect transistor, and let it stand and dry at 20 °C for 8 h to obtain a flexible field-effect transistor for dopamine detection.

[0027] Example 2 Unless otherwise specified in this example and subsequent examples, the conditions are the same as those in Example 1. This example provides a preparation method of a flexible field-effect transistor for dopamine detection.

[0028] Preparation of flexible field-effect transistor: Polyimide was used as the flexible substrate with a thickness of 20 μm. Polyimide was prepared by spin coating with an annealing temperature of 300 °C, an annealing atmosphere of oxygen, and an annealing time of 1 h. The bottom gate dielectric layer Ta2O5 with a thickness of 200 nm was deposited on the flexible substrate by plasma-enhanced chemical vapor deposition; the annealing temperature was 250 °C, the annealing atmosphere was oxygen, and the annealing time was 0.5 h. The conductive channel In2O3 with a thickness of 60 nm was deposited on the bottom gate dielectric layer by magnetron sputtering, the annealing temperature was 250 °C, the annealing atmosphere was oxygen, and the annealing time was 1 h. The source and drain were deposited on the conductive channel by electron beam evaporation, the conductive material was Cr / Au with a thickness of 60 nm, the annealing temperature was 200 °C, the annealing atmosphere was nitrogen, and the annealing time was 0.5 h. The top gate dielectric layer HfO2 with a thickness of 100 nm was deposited on the conductive channel by plasma-enhanced chemical vapor deposition, the annealing temperature was 200 °C, the annealing atmosphere was oxygen, and the annealing time was 1 h.

[0029] Preparation of high-entropy Prussian blue analogue material: A transition metal salt solution composed of FeCl2, CoCl2, NiCl2, CuCl2, and MnSO4 was prepared, and the concentration of each metal salt was 50 mM; sodium citrate was added until the concentration reached 100 mM, and it was stirred for 0.5 h to obtain solution A. An aqueous potassium ferricyanide solution with a concentration of 60 mM was prepared and denoted as solution B. Solution A was mixed with solution B, stirred at room temperature for 1 hour, and left standing for 24 hours for the synthesis reaction. After the reaction, it was centrifuged at 7000 rpm for 5 minutes to separate the reactants. Finally, it was dried at 70 °C for 8 hours to obtain high-entropy Prussian blue analogue powder.

[0030] (3) Flexible field-effect transistor for dopamine detection: The high-entropy Prussian blue analogue powder was dispersed in deionized water to obtain a dispersion with a concentration of 10 mg / mL. 0.5 μL of the dispersion and 0.2 μL of a chitosan solution with a concentration of 4 mg / mL were mixed evenly as a linking aid, and the linking aid was dropped onto the surface of the top gate dielectric layer of the flexible field-effect transistor and left standing to dry at 40 °C for 12 h to obtain a flexible field-effect transistor for dopamine detection.

[0031] Example 3 This example provides a preparation method of a flexible field-effect transistor for dopamine detection, and the steps are as follows: (1)Preparation of flexible field-effect transistor: PDMS was used as the flexible substrate with a thickness of 10 μm. PDMS was prepared by spin coating and cured in an oven at a curing temperature of 100 °C. The bottom gate dielectric layer Ta2O5 was deposited on the flexible substrate by plasma-enhanced chemical vapor deposition with a thickness of 300 nm; the annealing temperature was 250 °C, the annealing atmosphere was oxygen, and the annealing time was 1 h. The conductive channel In2O3 was deposited on the bottom gate dielectric layer by magnetron sputtering with a thickness of 80 nm, the annealing temperature was 300 °C, the annealing atmosphere was oxygen, and the annealing time was 1 h. The source and drain were deposited on the conductive channel by electron beam evaporation, and the conductive material was Cr / Au with a thickness of 80 nm, the annealing temperature was 250 °C, the annealing atmosphere was nitrogen, and the annealing time was 1 h. The top gate dielectric layer Ta2O5 was deposited on the conductive channel by plasma-enhanced chemical vapor deposition with a thickness of 200 nm; the annealing temperature was 250 °C, the annealing atmosphere was oxygen, and the annealing time was 1 h.

[0032] (2)A transition metal salt solution composed of FeCl2, CoCl2, NiCl2, CuCl2 and MnSO4 was prepared, and the concentration of each metal salt was 1 mM; in addition, sodium citrate was added to a concentration of 1 mM and stirred for 0.5 h to mix evenly to obtain solution A. An aqueous solution of potassium ferricyanide at 2 mM was prepared and denoted as solution B. Solution A and solution B were mixed and stirred at room temperature for 1 h and then left standing for 30 h for the synthesis reaction. After the reaction was completed, it was centrifuged at 6000 rpm for 5 minutes to separate the reactants. Finally, it was dried at 40 °C for 20 h to obtain high-entropy Prussian blue analogue powder.

[0033] (3)Flexible field-effect transistor for dopamine detection: The high-entropy Prussian blue analogue powder was dispersed in deionized water to obtain a dispersion with a concentration of 15 mg / mL. 1.5 μL of the dispersion and 0.5 μL of a chitosan solution with a concentration of 8 mg / mL were mixed evenly as a linking aid, and the linking aid was dropped onto the surface of the top gate dielectric layer of the flexible field-effect transistor and left standing at 60 °C for drying for 6 h to obtain a flexible field-effect transistor for dopamine detection.

[0034] The flexible field-effect transistors prepared in each example were subjected to dopamine performance testing.

[0035] 1. Performance testing of flexible field-effect transistor Inject 1 mL of pre-prepared PBS buffer (prepared by adding 32.275 g of potassium chloride, 40.8275 g of potassium dihydrogen phosphate, 45.643 g of disodium hydrogen phosphate, and 10 g of potassium sorbate to 5 L of deionized water and mixing evenly) into the detection cell. Cover the surface of the gate dielectric layer evenly with the buffer, and immerse the Ag / AgCl reference electrode to construct a liquid junction interface. Connect the gate, drain, and source of the flexible FET device to an electrochemical workstation (CHI660E, Shanghai Chenhua Instrument Co., Ltd.) respectively. Set the gate-source voltage to be constant at 1 V, and set the source-drain scan voltage to 0 - 1.5 V with a step size of 0.05 V to obtain the reference response curve at a dopamine concentration of 0 pM. Remove the buffer in the original detection cell and replace it successively with 1 mL of dopamine solutions with different concentrations (concentration gradient: 1 pM, 10 pM, 100 pM, 1 nM, 10 nM, 100 nM, 1 μM, 10 μM, 100 μM, 1 mM, 10 mM). The raw material of dopamine hydrochloride used in the experiment (Aladdin Biochemical Technology, Shanghai) is stored in a low-temperature environment of 2 - 8 °C according to the specification, and each gradient solution is prepared immediately with PBS buffer before detection. The device shows excellent linear response (R² = 0.991) in the concentration range of 1 pM - 10 mM. In addition, the current responses of dopamine solutions with different concentrations (concentration gradient as above) were also compared under an ISFET device without high-entropy Prussian blue analogue modification. The test results are as Figure 3 shown. The sensitivity and linearity of the device modified with high-entropy Prussian blue analogue are both higher than those of the device without high-entropy Prussian blue analogue modification, which proves that the high-entropy Prussian blue analogue has a significant promoting effect on the device performance.

[0036] 2. Repeatability test According to the process described in Example 1, batch-prepare 6 groups of flexible field-effect transistor devices dedicated to dopamine detection. Number the devices sequentially according to the preparation batch (labeled 1 - 6). Select the No. 1 device as the first test sample, inject 1 mL of dopamine test solution with a concentration of 1 mM, set the source-drain voltage scan range to 0 - 1.5 V, and the gate-source voltage to be constant at 1 V, and the response curve of the device at a dopamine concentration of 1 mM can be obtained. After completing the test of device 1, replace it with device 2, keep the test solution concentration (1 mM) and detection parameters constant, and repeat the complete test process. Complete the tests of devices 3 - 6 in this way. The test results are as Figure 4 shown. The corresponding signals of each flexible field-effect transistor have small differences and have good repeatability.

[0037] 3. Anti-interference test The prepared flexible extended-gate field-effect transistor was subjected to dopamine anti-interference testing. Add 1 mL of the test solution with a dopamine concentration of 1 mM. Set the source-drain voltage of the flexible field-effect transistor to 0 - 1.5 V and the gate-source voltage to 1 V; the detection curve at a dopamine concentration of 1 mM can be obtained. After the test, change the detection system and add 1 mL of the test solutions of glycine (Gly), ascorbic acid (AA), urea (Urea), uric acid (UA), glucose (Glu), potassium ion (KCl), and sodium ion (NaCl) diluted with PBS buffer respectively. The concentration of each test solution is 10 mM. Among them, AA, Glu, and NaCl were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., UA was purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd., Gly was purchased from Sinopharm Reagent, KCl was purchased from Shanghai Lingfeng Chemical Reagent Co., Ltd., Urea was purchased from Macklin Reagent, and the storage method for all of them is at room temperature. The anti-interference test results of the flexible field-effect transistor are as Figure 5 shown. The test results show that it can still maintain a specific signal response to dopamine in a detection system with multiple interfering substances, demonstrating excellent anti-interference ability. The above results all indicate that this flexible field-effect transistor has excellent dopamine recognition ability.

[0038] 4. Long-term stability test The flexible field-effect transistor device prepared based on the process of Example 1 was subjected to a 28-day long-term stability test in a constant temperature environment of 10°C. Quantitatively test 1 mL of the dopamine detection solution with a concentration of 1 nM every week, keep the gate-source voltage constant at 1 V, and the source-drain scanning voltage at 0 - 1.5 V to obtain its response curve. The experimental data show that after the 28-day long-term stability test, the signal retention rate of the device reaches 89.2% (relative to the initial value), confirming that this flexible field-effect transistor has good long-term stability.

[0039] Comparative Example 1 The difference between this comparative example and Example 1 is that when preparing the flexible field-effect transistor, neither the top gate dielectric layer Ta2O5 nor the source-drain electrodes Cr / Au were annealed, and the other conditions remained unchanged. During the test, this flexible field-effect transistor was easily corroded by the test liquid, showing poor durability.

[0040] Comparative Example 2 The difference between this comparative example and Example 1 is that when preparing the high-entropy Prussian blue analogue material, sodium citrate surfactant was not added to Solution A, and the other conditions remained unchanged. Under this synthesis condition, regular cubic-structured high-entropy metal particles could not be formed, and the product mainly consisted of a large number of aggregated large-sized particles. The device prepared based on this material had a weak response signal to dopamine.

[0041] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention in other forms. Any person skilled in the relevant art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes and apply them to other fields. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A flexible field effect transistor for detecting dopamine in sweat, characterized in that: It comprises a flexible substrate and a bottom gate dielectric layer covering the flexible substrate, wherein a source electrode and a drain electrode are arranged on the bottom gate dielectric layer, a semiconductor conductive channel is arranged between the source electrode and the drain electrode, and a top gate dielectric layer is arranged on the surface of the semiconductor conductive channel; A functional layer is disposed on the surface of the top gate dielectric layer, and the functional layer is prepared in the following steps: (1) adding a transition metal salt solution and a surfactant into deionized water and stirring them to obtain a mixed solution A; dissolving transition metal potassium cyanide in deionized water to obtain a solution B; mixing the mixed solution A and the solution B and stirring them to perform a synthesis reaction; after the reaction is completed, centrifuging and drying to obtain a high entropy Prussian blue analog powder; (2) Dispersing high entropy Prussian blue analog powder in deionized water to obtain a dispersion, mixing the linking aid and the dispersion to obtain a mixed solution C, dropping the mixed solution C onto the surface of the top gate dielectric layer, and standing to dry.

2. The flexible field effect transistor for detecting dopamine in sweat according to claim 1, characterized in that: The flexible substrate is made of polyimide or polydimethylsiloxane with a thickness of 10-20 μm; the bottom gate dielectric layer is made of Ta2O5 with a thickness of 200-300 nm; the semiconductor conductive channel material is In2O3 with a thickness of 50-80 nm; the conductive material of the source and drain is Cr / Au with a thickness of 50-80 nm; the top gate dielectric layer is made of Ta2O5 or HfO2 with a thickness of 100-200 nm.

3. The flexible field effect transistor for detecting dopamine in sweat according to claim 2, characterized in that: The flexible substrate is prepared by spin coating, the bottom gate dielectric layer and the top gate dielectric layer are prepared by plasma enhanced chemical vapor deposition, the source and the drain are deposited by electron beam evaporation, and the semiconductor conductive channel is deposited by magnetron sputtering.

4. The flexible field effect transistor for detecting dopamine in sweat according to claim 1, characterized in that: In the step (1), the transition metal salt in the mixed solution A is one or more of FeCl2, CoCl2, NiCl2, CuCl2 or MnSO4, and the concentration of the transition metal salt solution is 1-50 mM; the surfactant in the mixed solution A is sodium citrate, and the concentration of the surfactant is 1-100 mM; the transition metal potassium cyanide in solution B is potassium ferrocyanide, and the concentration is 2-60 mM; the synthesis reaction time is 18-30 h, and the synthesis reaction temperature is 10-50 °C.

5. The flexible field effect transistor for detecting dopamine in sweat according to claim 1, characterized in that: In step (2), the concentration of the dispersion is 5-15 mg / mL, the linking aid is a chitosan solution with a concentration of 4-8 mg / mL; the volume of the dispersion in the mixed solution C is 0.5-1.5 μL, and the volume of the chitosan solution is 0.2-0.5 μL; the static drying temperature is 20-60°C, and the static drying time is 6-12 h.

6. Use of the flexible field effect transistor according to any one of claims 1 to 5 in sweat dopamine detection.

Images