Carbon nanotube transistor flexible ion sensor array and preparation method thereof

Abstract

The present invention provides a carbon nanotube transistor flexible ion sensor array, comprising a flexible substrate and an ion sensitive array area and a transistor signal amplification area formed on the flexible substrate and connected by metal leads. The ion sensitive array area adopts a multi-sensitive electrode parallel structure with a common reference; the transistor signal amplification area includes a semiconductor single-walled carbon nanotube network film channel, a metal source and drain electrode, a high-K gate dielectric layer, and a metal gate electrode. The sensor array of the present invention adopts a structural form in which the sensitive area is separated from the channel interface, which gives full play to the intrinsic characteristics of the high carrier mobility of carbon nanotubes, improves the sensitivity of the device, and effectively improves its stability, accuracy and repeatability. The present invention also provides a method for preparing a carbon nanotube transistor flexible ion sensor array, which has the characteristics of mild process conditions, simple steps, and compatibility with flexible substrates.

Description

Technical Field

[0001] The invention belongs to the field of chemical sensing, and in particular relates to a carbon nanotube transistor flexible ion sensor array and a preparation method thereof. Background Art

[0002] Accurate, rapid and stable monitoring of ion concentrations in complex systems plays a vital role in many fields including genome sequencing, medical diagnosis, environmental monitoring, industrial production, smart home, etc. Compared with chromatography and spectral analysis techniques, potentiometric ion sensors have attracted more and more attention due to their compact structure, easy integration, and real-time, on-site measurement capabilities. As a common potentiometric ion sensor, ion sensitive field effect transistor (ISFET) is the product of the combination of ion-sensitive, selective electrode manufacturing technology and solid-state microelectronics.

[0003] However, in the existing technology, due to the particularity of the ISFET structure, its cumbersome preparation process is still an important bottleneck restricting its research and production. In addition, the channel part of the traditional ISFET device often acts directly on the test environment through the sensitive membrane, which is easily affected by other components in the complex system, resulting in a decrease in device performance. Although the concept of ion-sensitive arrays has been proven to effectively improve device selectivity issues in the past, these arrays still face important challenges in terms of resolution and detection limits required for real-time sensing applications. Summary of the invention

[0004] In order to solve the problems in the prior art, the present invention provides a carbon nanotube transistor flexible ion sensor array and a preparation method thereof. By adopting a carbon nanotube channel material with high carrier mobility, a sensor array with an extended top gate structure capable of detecting multiple ion targets and an effective preparation method thereof are proposed, thereby improving multiple performance indicators of the ion sensor, such as detection efficiency, sensitivity, stability and reliability.

[0005] According to a first aspect of the present invention, a carbon nanotube transistor flexible ion sensor array is provided, comprising:

[0006] a flexible substrate; and

[0007] An ion sensitive array region and a transistor signal amplification region are formed on the flexible substrate;

[0008] The ion-sensitive array area includes ion-sensitive electrodes composed of metal electrodes functionalized with multiple different ion-sensitive membranes and Ag / AgCl reference electrodes coated with polyvinyl butyral (PVB) arranged one-to-one with the ion-sensitive electrodes;

[0009] The ion-sensitive array area adopts a multi-sensitive electrode parallel structure with a common reference, forming a loop through the liquid to be tested;

[0010] The transistor signal amplification region includes, from bottom to top, a semiconductor single-walled carbon nanotube network film channel layer located above the flexible substrate, a metal source electrode and a metal drain electrode located on the semiconductor carbon nanotube network film, a gate dielectric layer located between the source and drain electrodes, and a metal gate electrode located on the gate dielectric layer, forming a transistor sensing unit, and each transistor sensing unit is correspondingly arranged with a group of ion-sensitive electrodes and a reference electrode;

[0011] Wherein, the transistor adopts an extended top gate structure, and the ion-sensitive electrode and the metal gate electrode are connected through multi-layer interconnection lines;

[0012] The ion sensitive array region and the transistor signal amplification region are separated from each other in space. The transistor signal amplification region is deposited with a thin film package for protection, and the ion sensitive array region is exposed outside the package region.

[0013] Therefore, the carbon nanotube transistor flexible ion sensor array applies a stable gate voltage to the gate electrodes of each transistor through the reference electrode via the electrolyte solution. The different ion concentrations in the test solution cause changes in the interface potential of the ion-sensitive electrode, which modulates the effective gate voltage and channel current of the transistor, thereby generating electrical signal changes that depend on specific ion concentrations.

[0014] Preferably, the flexible substrate includes polyethylene terephthalate (PET), polyparaxylene film (parylene C), polyetherimide (PEI), polyethylene naphthalate (PEN), polydimethylsiloxane (PDMS) and polyimide (PI).

[0015] Preferably, the purity of the semiconductor single-walled carbon nanotube network film in the channel is not less than 99.9%, and the linear density of the carbon nanotubes is 20-80 per micrometer.

[0016] Preferably, the metal source and drain electrodes are composed of three metals, Ti, Pd and Au, deposited in sequence on a flexible substrate, and their thicknesses are in the range of 0.2-1 nm, 15-40 nm and 30-60 nm respectively.

[0017] Preferably, the high-K gate dielectric layer comprises yttrium oxide, hafnium oxide, and a combination of the two in any thickness ratio, and has a thickness of 6-15 nm.

[0018] Preferably, the metal gate electrode and the metal parts of the ion-sensitive electrode and the reference electrode are all composed of two metals, Ti and Au, which are deposited in sequence on a flexible substrate, and their thicknesses are 3-10 nm and 30-80 nm, respectively.

[0019] According to a second aspect of the present invention, a method for preparing a carbon nanotube transistor flexible ion sensor array is provided, comprising the following steps:

[0020] (1) Preparing a semiconductor carbon nanotube network film on a flexible substrate using a solution deposition method;

[0021] (2) Evaporating a metal source electrode and a metal drain electrode: Ti, Pd, and Au are sequentially deposited on the semiconductor carbon nanotube network film by photolithography and electron beam evaporation to form a metal source and drain electrode; and the semiconductor carbon nanotube network film in other areas except between the metal source and drain electrodes is etched to obtain a CNT channel layer;

[0022] (3) growing a high-K gate dielectric layer of a certain thickness on the CNT channel layer;

[0023] (4) depositing Ti and Au metal layers in sequence by photolithography and electron beam evaporation to prepare metal gate electrodes, ion-sensitive electrodes, and metal substrates of reference electrodes, respectively; the ion-sensitive electrodes and the metal gate electrodes are connected by multi-layer interconnection lines;

[0024] (5) Depositing Parylene C film on the transistor signal amplification area to encapsulate and protect it;

[0025] (6) In the ion sensitive array region, an ion sensitive film is coated on the ion sensitive electrode connected to the metal gate electrode, and Ag / AgCl and PVB films are coated on the metal substrate of the reference electrode and activated in a 3M KCl solution.

[0026] Compared with the prior art, the carbon nanotube transistor flexible ion sensor array of the present invention has the following significant beneficial effects:

[0027] First, the use of semiconductor single-walled carbon nanotubes with extremely high carrier mobility as channel materials greatly improves the response speed of the sensor; and the ultra-thin carbon nanotube film is easily controlled by the gate, which can effectively reduce the device operating voltage and improve the sensor sensitivity;

[0028] Secondly, the transistor sensor array in the carbon nanotube transistor flexible ion sensor array adopts a structural design based on an extended top gate to avoid the influence of complex matrix on the channel material and give full play to the intrinsic characteristics of high carrier mobility of semiconductor single-walled carbon nanotubes; at the same time, by designing the sensor unit array, it can realize the simultaneous detection of multiple targets, greatly improve the detection flux, and effectively eliminate the influence of potential interfering ions, thereby improving the accuracy and repeatability of detection;

[0029] Finally, compared with the high temperature and complex process of silicon-based transistors, the method for preparing carbon nanotube transistors based on a low-temperature solution method provided in the preparation process of the present invention has the characteristics of mild process conditions and simple steps, which effectively overcomes the incompatibility problem of high-temperature doping and flexible substrates in micro-machining processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] For the sake of clarity, some of the schematic diagrams in the drawings are not drawn to scale.

[0031] Figure 1 It is a schematic structural diagram of a carbon nanotube transistor flexible ion sensor array according to an embodiment of the present invention.

[0032] Figure 2 This is a scanning electron microscope image of a semiconductor single-walled carbon nanotube network film deposited on a flexible substrate;

[0033] Figure 3 This is a schematic diagram of the structure of a flexible ion sensing unit of a carbon nanotube transistor;

[0034] Figure 4 are the transfer characteristic curves of carbon nanotube transistors prepared in different batches;

[0035] Figure 5 It is a schematic diagram of the preparation process of the carbon nanotube transistor flexible ion sensor array;

[0036] Figure 6 The carbon nanotube transistor flexible ion sensor array detects multiple ions, including:

[0037] (A) is the response curve of different concentrations of sodium ions, and (D) is the linear fitting diagram of sodium ions;

[0038] (B) is the response curve of different concentrations of potassium ions, and (E) is the fitted linear graph of potassium ions;

[0039] (C) is the response curve of different concentrations of chloride ions, and (F) is the chloride ion fitting linear graph. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific implementation examples, but the scope of the present invention is not limited thereto.

[0041] Combination Figure 1 , 3 The carbon nanotube transistor flexible ion sensor array of the illustrated example includes a flexible substrate; and an ion sensitive array region and a transistor signal amplification region formed on the flexible substrate.

[0042] The ion sensitive array area includes ion sensitive electrodes composed of metal electrodes functionalized with various ion sensitive membranes and Ag / AgCl reference electrodes coated with polyvinyl butyral (PVB) arranged one by one with the ion sensitive electrodes. The ion sensitive array area adopts a multi-sensitive electrode parallel structure with a common reference, and forms a circuit through the test liquid.

[0043] The transistor signal amplification area includes, from bottom to top, a semiconductor single-walled carbon nanotube network film channel layer located above the flexible substrate, a metal source electrode and a metal drain electrode located on the semiconductor carbon nanotube network film, a gate dielectric layer located between the source and drain electrodes, and a metal gate electrode located on the gate dielectric layer, forming a transistor sensing unit (i.e., a FET transistor structure), and each transistor sensing unit is arranged corresponding to a group of ion-sensitive electrodes and a reference electrode.

[0044] Combination Figure 1 , 3 As shown, the transistor sensing unit adopts an extended top gate structure, and the ion sensitive electrode is connected to the metal gate electrode through multi-layer interconnection lines.

[0045] Combination Figure 3 As shown, the ion sensitive array region and the transistor signal amplification region are separated from each other in space, the transistor signal amplification region is deposited with a thin film package for protection, and the ion sensitive array region is exposed outside the package region.

[0046] As an optional embodiment, the flexible substrate includes one of polyethylene terephthalate (PET), parylene C, polydimethylsiloxane (PDMS) and polyimide (PI).

[0047] As an optional implementation, the purity of the semiconductor single-walled carbon nanotubes in the channel layer of the semiconductor single-walled carbon nanotube network film reaches more than 99.9%, and the linear density is 20-80 tubes / micrometer.

[0048] As an optional implementation, the metal source electrode and the metal drain electrode are both composed of three metals, Ti, Pd, and Au, deposited in sequence on the semiconductor carbon nanotubes, and their thickness ranges are 0.2-1nm, 15-40nm, and 30-60nm, respectively.

[0049] As an optional implementation, the gate dielectric layer is a high-K gate dielectric layer, and the thickness of the high-K gate dielectric layer is 6-15 nm.

[0050] As an optional implementation, the high-K gate dielectric layer includes yttrium oxide, hafnium oxide, and a combination of the two in any thickness ratio.

[0051] As an optional implementation, a stable gate voltage is applied to the metal gate electrode of each transistor sensing unit through an Ag / AgCl reference electrode via an electrolyte solution. The different ion concentrations in the test liquid cause changes in the interface potential of the ion-sensitive electrode, which modulates the effective gate voltage and channel current of the transistor sensing unit, thereby generating electrical signal changes that depend on specific ion concentrations.

[0052] Combination Figure 1 In the example carbon nanotube transistor flexible ion sensor array structure shown, we have a group of multiple FET-type transistor sensor units corresponding to each ion sensitive electrode. In the figure, three transistor sensor units are taken as an example. The gate electrode layers of the transistor sensor units in each group are connected in sequence through metal leads, and the source and drain are led out to the PAD through their own separate metal leads. On the one hand, this ensures the normal operation of the transistor sensor unit, and on the other hand, multiple groups of parallel detections can be performed for the same type of ion detection, and the average value is taken during the detection process to reduce the detection error and ensure the reliability of the data.

[0053] According to an example disclosed in the present invention, a method for preparing a carbon nanotube transistor flexible ion sensor array is also provided, comprising the following steps:

[0054] (1) preparing a semiconductor carbon nanotube network film on the surface of a flexible substrate by a solution deposition method; thereby, a semiconductor carbon nanotube network film can be obtained on the entire surface of the flexible substrate;

[0055] (2) Evaporating a metal source electrode and a metal drain electrode: Ti, Pd, and Au are sequentially deposited on the semiconductor carbon nanotube network film by photolithography and electron beam evaporation to form a metal source and drain electrode; and the semiconductor carbon nanotube network film in other areas except between the metal source and drain electrodes is etched to obtain a CNT channel layer;

[0056] (3) growing a high-K gate dielectric layer of a certain thickness on the CNT channel layer;

[0057] (4) depositing Ti and Au metal layers in sequence by photolithography and electron beam evaporation to prepare metal gate electrodes, ion-sensitive electrodes, and metal substrates of reference electrodes, respectively; the ion-sensitive electrodes and the metal gate electrodes are connected by multi-layer interconnection lines;

[0058] (5) Depositing Parylene C film on the transistor signal amplification area to encapsulate and protect it;

[0059] (6) In the ion sensitive array region, an ion sensitive film is coated on the ion sensitive electrode connected to the metal gate electrode, and Ag / AgCl and PVB films are coated on the metal substrate of the reference electrode and activated in a 3M KCl solution.

[0060] Wherein, in the aforementioned step (1), the clean flexible substrate is completely immersed in the semiconductor carbon nanotube dispersion, and after being allowed to settle for a period of time, the flexible substrate is rinsed with toluene, acetone, ethanol and deionized water respectively, and then baked on a hot plate for 5-10 minutes.

[0061] As an optional example of the present invention, the operation of preparing a semiconductor carbon nanotube network film on the surface of a flexible substrate is specifically as follows: completely immerse the clean flexible substrate in a semiconductor single-walled carbon nanotube dispersion with a concentration of 2-20 μg / mL, and after standing and depositing for 8-24 hours, rinse the flexible substrate with toluene solution, acetone solution, ethanol solution, and deionized water respectively to remove impurities and polymers in the carbon nanotube solution, and then heat bake at 100-120 degrees Celsius for 5-10 minutes.

[0062] Wherein, in the aforementioned semiconductor single-walled carbon nanotube dispersion, the purity of the semiconductor single-walled carbon nanotube is not less than 99.9%, and the concentration is 2-20 μg / L.

[0063] Wherein, in step (6), before preparing the ion sensitive electrode and the reference electrode, the method further includes: etching the Parylene C film layer in the ion sensitive array region by photolithography and oxygen plasma etching process to expose the Parylene C film layer outside the packaging region.

[0064] The preparation process of the carbon nanotube transistor flexible ion sensor array of the present invention is further described below in combination with the accompanying drawings and specific implementation examples, but the scope of the present invention is not limited thereto.

[0065] (1) Preparation of semiconducting single-walled carbon nanotube network films by solution deposition

[0066] A clean flexible substrate (such as a P-type silicon substrate) was completely immersed in a dispersion of semiconductor single-walled carbon nanotubes with a purity of 99.9% and allowed to stand for 8 hours. It was then rinsed with toluene, acetone, ethanol and deionized water for 1 minute each, dried with a nitrogen gun and then baked on a hot plate at 120 degrees for 5 minutes. The scanning electron microscope results are shown in Figure 2. Figure 2 It shows that the semiconducting single-walled carbon nanotubes on the flexible substrate are well dispersed, highly uniform, and of moderate density, and their disordered arrangement forms a network-like film.

[0067] (2) Preparation of metal source and drain electrodes:

[0068] A 0.5 nm thick Ti, a 20 nm thick Pd and a 40 nm thick Au metal layer were sequentially deposited on the semiconductor single-walled carbon nanotube network film by photolithography and electron beam coating technology.

[0069] (3) Growth of gate dielectric layer

[0070] The carbon nanotube film outside the source and drain electrode regions is etched cleanly through photolithography and oxygen plasma etching technology, and then a 10nm thick hafnium oxide is grown on the transistor channel as a high-k gate dielectric layer through atomic layer deposition technology.

[0071] (4) Preparation of metal gate electrode and metal substrate of ion sensitive electrode and reference electrode

[0072] By photolithography and electron beam coating technology, 10nm thick Ti and 80nm thick Au are deposited in sequence as the metal gate electrode and the ion sensitive electrode and reference electrode metal substrate respectively. The transfer characteristic curve of the prepared top-gate carbon nanotube transistor is shown in Figure 4 shown.

[0073] (5)Parylene packaging

[0074] A 2μm thick layer of Parylene C is deposited on the sensor array by a Parylene thin film deposition system, an etching window is exposed by a photolithography process, and then the Parylene C film in the ion sensitive area is removed by oxygen plasma reaction etching, and then the photoresist is removed in a photoresist stripping solution.

[0075] (6) Preparation of ion-sensitive electrode and reference electrode:

[0076] 6-1) Modification of hydrogen ion sensitive electrode: pattern the hydrogen ion sensor to leave a window, deposit a 20 nm aluminum oxide film at low temperature using an atomic layer deposition system, remove the photoresist, and leave the aluminum oxide in the hydrogen ion sensitive area;

[0077] 6-2) Modification of sodium, potassium and chloride ion-sensitive electrodes: Cast sodium, potassium and chloride selective membranes on the corresponding ion-sensitive electrodes and dry them overnight under ambient conditions;

[0078] 6-3) Reference electrode modification: Ag / AgCl slurry was coated on the metal substrate as the reference electrode and dried overnight under ambient conditions. It was then cured at 120°C for 2 minutes; PVB solution was poured onto the prepared Ag / AgCl coating and allowed to stand for 2 hours to form a PVB film, and finally the PVB film was activated in 3M KCl for 6 hours.

[0079] Figure 1 , 3 The invention shows the carbon nanotube transistor flexible ion sensor array and the transistor sensor unit structure and basic principle. The sensor array includes a flexible substrate, an ion sensitive array and a transistor signal amplification area.

[0080] A stable gate voltage is applied through the reference electrode, and the sensitive membrane is used to selectively convert the ion concentration information in the test liquid into a potential disturbance signal, which is transmitted to the channel interface through the metal extension gate. The semiconductor carbon nanotubes are sensitive to changes in potential, causing significant changes in the transistor current channel current, thereby achieving highly sensitive quantitative analysis.

[0081] Figure 4 These are the transfer curve test results of multiple sensor array devices of different batches prepared by the present invention. It can be found that the prepared transistor sensor units all exhibit p-type FET characteristics and are highly uniform. The current switching ratio reaches 5 to 6 orders of magnitude, which effectively proves the superiority and reliability of transistor performance.

[0082] Figure 5 For preparation Figure 4 The process diagram of the carbon nanotube transistor flexible ion sensor array shown has the advantages of mild process conditions and simpler steps compared to the existing technology, and can effectively avoid the problem of incompatibility between high temperature process and flexible substrate during device preparation.

[0083] Figure 6 The results of the carbon nanotube transistor flexible ion sensor array prepared in the embodiment for different ions are shown. It can be seen that under a specific current intensity, combined with Figure 6 The A, B, and C of the detector correspond to the ion response curves of different concentrations. There is a good linear relationship between the gate voltage and the logarithm of the target ion concentration. Especially for the detection sensitivity of sodium and potassium ions, it reaches the Nernst limit. Figure 6 D, E, and F represent the linear fitting results of ions. The linear correlation coefficients of all ion standard curves are greater than 0.99, showing good accuracy and reliability.

[0084] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A carbon nanotube transistor flexible ion sensor array, characterized in that: include: Flexible substrate; as well as An ion sensitive array region and a transistor signal amplification region are formed on the flexible substrate; The ion-sensitive array area includes ion-sensitive electrodes composed of metal electrodes functionalized with multiple different ion-sensitive membranes and Ag / AgCl reference electrodes coated with polyvinyl butyral (PVB) arranged one-to-one with the ion-sensitive electrodes; The ion-sensitive array area adopts a multi-sensitive electrode parallel structure with a common reference, forming a loop through the liquid to be tested; The transistor signal amplification region includes, from bottom to top, a semiconductor single-walled carbon nanotube network film channel layer located above the flexible substrate, a metal source electrode and a metal drain electrode located on the semiconductor carbon nanotube network film, a gate dielectric layer located between the source and drain electrodes, and a metal gate electrode located on the gate dielectric layer, forming a transistor sensing unit, and each transistor sensing unit is correspondingly arranged with a group of ion-sensitive electrodes and a reference electrode; The gate dielectric layer is a high-K gate dielectric layer, the thickness of the high-K gate dielectric layer is 6-15 nm, and the high-K gate dielectric layer includes yttrium oxide, hafnium oxide, and a combination of the two in any thickness ratio; Wherein, the transistor adopts an extended top gate structure, and the ion-sensitive electrode and the metal gate electrode are connected through multi-layer interconnection lines; The ion sensitive array region and the transistor signal amplification region are separated from each other in space, the transistor signal amplification region is deposited with a thin film package for protection, and the ion sensitive array region is exposed outside the package region; By adopting an extended top-gate structural design, the influence of complex matrix on channel materials is avoided and the intrinsic characteristics of high carrier mobility of semiconductor single-walled carbon nanotubes are fully utilized. At the same time, by designing an array of sensor units, simultaneous detection of multiple targets is achieved, greatly improving the detection flux and effectively eliminating the influence of potential interfering ions, thereby improving the accuracy and repeatability of detection.

2. The carbon nanotube transistor flexible ion sensor array according to claim 1, characterized in that: The flexible substrate includes one of polyethylene terephthalate, polyparaxylene film, polydimethylsiloxane and polyimide.

3. The carbon nanotube transistor flexible ion sensor array according to claim 1, characterized in that: The purity of the semiconductor single-walled carbon nanotubes in the channel layer of the semiconductor single-walled carbon nanotube network film reaches more than 99.9%, and the linear density is 20-80 tubes / micrometer.

4. The carbon nanotube transistor flexible ion sensor array according to claim 1, characterized in that: The metal source electrode and the metal drain electrode are both composed of three metals, Ti, Pd and Au, which are deposited in sequence on the semiconductor carbon nanotubes, and their thickness ranges are 0.2-1 nm, 15-40 nm and 30-60 nm respectively.

5. The carbon nanotube transistor flexible ion sensor array according to any one of claims 1 to 4, characterized in that: A stable gate voltage is applied to the metal gate electrode of each transistor sensing unit through the Ag / AgCl reference electrode via the electrolyte solution. The different ion concentrations in the test solution cause the interface potential of the ion-sensitive electrode to change, so that the effective gate voltage and channel current of the transistor sensing unit are modulated, thereby generating an electrical signal change that depends on the specific ion concentration.

6. A method for preparing a carbon nanotube transistor flexible ion sensor array according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Prepare semiconductor carbon nanotube network films on the surface of flexible substrates by solution deposition method; (2) Evaporation of metal source electrode and metal drain electrode: Ti, Pd, and Au are sequentially deposited on the semiconductor carbon nanotube network film by photolithography and electron beam evaporation to form metal source and drain electrodes; and the semiconductor carbon nanotube network film in other areas except between the metal source and drain electrodes is etched to obtain a CNT channel layer; (3) growing a high-K gate dielectric layer of a certain thickness on the CNT channel layer; (4) depositing Ti and Au metal layers in sequence by photolithography and electron beam evaporation to prepare metal gate electrodes, ion sensitive electrodes, and metal substrates of reference electrodes, respectively; the ion sensitive electrodes and the metal gate electrodes are connected by multi-layer interconnects; (5) Depositing Parylene C film on the transistor signal amplification area to encapsulate and protect it; (6) In the ion sensitive array region, an ion sensitive film is coated on the ion sensitive electrode connected to the metal gate electrode, and Ag / AgCl and PVB films are coated on the metal substrate of the reference electrode and activated in a 3M KCl solution.

7. The method for preparing a carbon nanotube transistor flexible ion sensor array according to claim 6, characterized in that: In the step (6), before preparing the ion-sensitive electrode and the reference electrode, the method further includes: etching the Parylene C film layer in the ion-sensitive array region by photolithography and oxygen plasma etching to expose the Parylene C film layer outside the packaging region.

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