Miniature multi-ion sensing system based on non-gate array and preparation method thereof

Abstract

The invention discloses a miniature multi-ion sensing system based on a non-gate array and a preparation method thereof, and belongs to the technical field of electrochemical sensing, and the miniature multi-ion sensing system comprises a multi-ion sensing unit and a molybdenum disulfide non-gate array; the multi-ion sensitive unit comprises a metal electrode array, an ion sensitive film array and a liquid storage tank, multiple ions are detected through the ion sensitive film array at the same time and converted into electric signals, and the electric signals are transmitted to the molybdenum disulfide non-gate array through the metal electrode array; the molybdenum disulfide NOT gate array comprises a plurality of molybdenum disulfide NOT gates, and each molybdenum disulfide NOT gate comprises a metal electrode layer, a molybdenum disulfide layer, a NOT gate input end and a NOT gate output end, so that two field effect transistors are formed, received electric signals are amplified, the Nernst limit is broken through a NOT gate structure, and tiny changes of ion concentration are accurately detected. The sensitivity is higher; molybdenum disulfide is used as a channel material of the NOT gate, so that the size and power consumption of the NOT gate are effectively reduced, the integration level of the system is improved, and the service life of the system is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical sensing, and in particular relates to a micro multi-ion sensing system based on a NAND gate array and a preparation method thereof. Background Art

[0002] The ion concentration in human body fluids is closely related to human health. Abnormal ion concentration in the human body, or electrolyte imbalance, is a common health problem in modern society. It can cause symptoms such as fatigue, dizziness, and headaches, and even induce serious illnesses such as hypertension, renal failure, and heart failure. Therefore, real-time monitoring of human ion concentration can help prevent and treat electrolyte imbalances at an early stage and effectively improve people's quality of life. However, current ion concentration detection technology mainly relies on blood tests in hospitals, which cannot meet the needs of portable and real-time health monitoring.

[0003] With the development of microelectronics technology, a method for ion detection based on field-effect transistors (FETs) has been proposed. The basic principle is to coat the gate surface of the transistor with a highly specific ion-sensitive film. A test liquid is then dripped onto the gate surface. When the concentration of the corresponding ion in the test liquid changes, the membrane surface potential (i.e., the gate equivalent potential) changes, causing the source-drain current to change. By measuring the transfer characteristic curve of the transistor, the concentration of the test ion can be calculated. This detection structure has the advantages of simple principle, low cost, fast response, and small size. Its processing is compatible with currently mature CMOS processes, and it has the potential for array fabrication.

[0004] However, the sensitivity of this detection method is limited by the Nernst limit. For example, at room temperature, a change in hydrogen ion concentration in the test liquid by one order of magnitude will result in a maximum change of 59.2 mV in the membrane surface potential. In actual testing, ion concentrations in the human body generally remain within a relatively stable range. With low sensitivity, even small concentration fluctuations may be difficult to detect. Furthermore, testing the transfer characteristic curve of a transistor requires measuring the source-drain current, which is related to the type of channel material used. Traditional field-effect transistors use silicon as their channel, which has low resistance, resulting in high source-drain currents and high power consumption. Newer field-effect transistors, represented by two-dimensional materials, have higher resistance and stronger gate control capabilities, but the lower source-drain currents place higher demands on subsequent processing circuits, making overall miniaturization of ion detection systems difficult. Summary of the Invention

[0005] In response to one or more of the above-mentioned defects or improvement needs of the prior art, the present invention provides a miniature multi-ion sensing system based on a non-gate array and a preparation method thereof, which can simultaneously detect the concentrations of multiple ions, has higher sensitivity, and can meet the miniaturization requirements of the sensing system.

[0006] To achieve the above objectives, one aspect of the present invention provides a micro multi-ion sensing system based on a NOT gate array and a preparation method thereof, which comprises a multi-ion sensitive unit and a molybdenum disulfide NOT gate array; The multi-ion sensitive unit includes a metal electrode array, an ion sensitive film array and a liquid reservoir; the liquid reservoir is arranged on the first substrate and is used to store the solution to be tested; the metal electrode array is arranged on the first substrate and in the liquid reservoir, and includes a plurality of first metal electrodes; the ion sensitive film array includes a plurality of ion sensitive films respectively arranged on each of the first metal electrodes, and different ion sensitive films contain different ion carriers; The MoS2 NOT gate array comprises a plurality of MoS2 NOT gates arranged on a second substrate; The molybdenum disulfide NOT gate comprises a metal electrode layer, a molybdenum disulfide layer, a NOT gate input terminal and a NOT gate output terminal; the NOT gate output terminal, the molybdenum disulfide layer and the metal electrode layer are arranged on the second substrate, and the molybdenum disulfide layer comprises a first molybdenum disulfide layer and a second molybdenum disulfide layer; the metal electrode layer comprises a second metal electrode and a third metal electrode spaced apart on both sides of the NOT gate output terminal, the second metal electrode and the NOT gate output terminal are connected to both ends of the first molybdenum disulfide layer, and the third metal electrode and the NOT gate output terminal are connected to both ends of the second molybdenum disulfide layer; a first insulating layer is arranged on one side of the NOT gate output terminal, the first molybdenum disulfide layer and the second metal electrode, and the NOT gate input terminal is arranged on the first insulating layer; a second insulating layer is arranged on the other side of the NOT gate output terminal, the second molybdenum disulfide layer and the third metal electrode, and the NOT gate output terminal extends from the second substrate and is arranged on the second insulating layer; Each of the first metal electrodes in the metal electrode array is connected to each of the NOT gate input terminals in the molybdenum disulfide NOT gate array in a one-to-one correspondence.

[0007] As a further improvement of the present invention, the molybdenum disulfide layer is a single atomic layer single crystal structure with a thickness of 0.5-1 nm.

[0008] As a further improvement of the present invention, the material of the first insulating layer and the second insulating layer is any one of aluminum oxide, hafnium oxide, and silicon dioxide, and the thickness is 30-50 nm.

[0009] As a further improvement of the present invention, the NOT gate input end, the NOT gate output end and the metal electrode layer are all double-layer metal stack structures; wherein the material of the lower metal layer is any one of Ti and Cr, with a thickness of 5~10nm, and the material of the upper metal layer is any one of Au, Ag, Cu, Pd, Pt, with a thickness of 20~30nm.

[0010] As a further improvement of the present invention, when the ion to be measured is a hydrogen ion, the corresponding first metal electrode is made of TiN with a thickness of 20 to 100 nm, and no ion-sensitive film is provided on the first metal electrode; when the ion to be measured is other ions, the corresponding first metal electrode is a double-layer metal stack structure, wherein the lower metal is any one of Ti and Cr with a thickness of 5 to 10 nm, and the upper metal is Au with a thickness of 20 to 30 nm.

[0011] As a further improvement of the present invention, both the first substrate and the second substrate are SiO2 / Si substrates, and the thickness of SiO2 in the SiO2 / Si substrate is 200-300 nm.

[0012] As a further improvement of the present invention, the material of the liquid storage tank is any one of polydimethylsiloxane and polymethyl methacrylate.

[0013] Another aspect of the present invention provides a method for preparing a multi-ion sensitive unit for use in the above-mentioned micro multi-ion sensing system based on a NOT gate array, comprising the following steps: (1) coating a photoresist on the surface of the first substrate and patterning the photoresist; (2) growing metal on the surface of the photoresist using a sputtering process, and removing the photoresist and the metal on the photoresist after sputtering to obtain a metal electrode array; (3) dropping each ion carrier and its corresponding sensitive solution onto the surface of its corresponding first metal electrode and drying them to obtain an ion-sensitive thin film array; (4) Bonding the liquid reservoir to the first substrate to complete the preparation of the multi-ion sensitive unit.

[0014] Another aspect of the present invention provides a method for preparing a molybdenum disulfide NOT gate array, which is used for preparing the molybdenum disulfide NOT gate array in the above-mentioned micro multi-ion sensing system based on the NOT gate array, comprising the following steps: (1) growing a monolayer of molybdenum disulfide on the surface of the second substrate by chemical vapor deposition; (2) coating a photoresist on the surface of the monolayer molybdenum disulfide and patterning the photoresist; (3) etching the molybdenum disulfide and removing the photoresist on the surface of the single-layer molybdenum disulfide after etching to obtain a molybdenum disulfide layer; (4) coating a photoresist on the surface of the second substrate and patterning the photoresist; (5) Using evaporation process to grow metal on the surface of photoresist, and removing the photoresist and the metal on the photoresist, the metal electrode layer and part of the NOT gate output end after evaporation; (6) Using evaporation technology to grow metal on the sample surface, and using atomic layer deposition technology to grow metal oxide on the sample surface; (7) Coating a photoresist on the surface of the metal oxide and patterning the photoresist; (8) etching the metal oxide and removing the photoresist on the surface of the metal oxide after etching to obtain a first insulating layer and a second insulating layer; (9) Spin-coat a layer of photoresist on the sample surface and pattern the photoresist; (10) A sputtering process is used to grow metal on the sample surface, and the photoresist and the metal on the photoresist are removed after sputtering to obtain the NOT gate input end and the remaining NOT gate output end, thereby completing the preparation of the MoS2 NOT gate array.

[0015] The above-mentioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0016] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art: The miniature multi-ion sensing system based on the NOT gate array of the present invention can simultaneously detect multiple ions through the design of each array structure in the system, which meets actual detection needs and facilitates large-scale preparation of sensors. By adopting the NOT gate structure to break the Nernst limit, it can accurately detect small changes in ion concentration and has higher sensitivity. The NOT gate output voltage is on the volt level, which is convenient for measurement, avoids the measurement of small currents, simplifies the circuit, is more conducive to subsequent processing of signals, and easily realizes the miniaturization of the sensing system. By utilizing the large band gap width of molybdenum disulfide, it is used as the channel material of the NOT gate to prepare field effect transistors with small channel current and strong gate control capability, and to build a low-power, high-gain NOT gate array, which can effectively reduce the size and power consumption of the NOT gate, improve the integration of the sensing system, and extend the service life of the sensing system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 1 is a schematic diagram of the overall structure of a micro multi-ion sensing system based on a NOT gate array in an embodiment of the present invention; Figure 2 1 is a schematic top view of the structure of a miniature multi-ion sensing system based on a NOT gate array according to an embodiment of the present invention; Figure 3is a transfer characteristic curve of a MoS2 field effect transistor formed in a micro multi-ion sensing system based on a NOT gate array in an embodiment of the present invention; Figure 4 is a transfer characteristic curve of a MoS2 NOT gate in a micro multi-ion sensing system based on a NOT gate array in an embodiment of the present invention; Figure 5 1 is a gain curve of the molybdenum disulfide NOT gate in the micro multi-ion sensing system based on the NOT gate array in an embodiment of the present invention.

[0019] In all the drawings, the same figure marks represent the same technical features, specifically: 1. MoS2 NOT gate; 11. NOT gate input; 12. NOT gate output; 13. First insulating layer; 14. Second insulating layer; 15. First MoS2 layer; 16. Second MoS2 layer; 17. Second metal electrode; 18. Third metal electrode; 19. Second substrate; 2. Multi-ion sensitive unit; 21. Liquid reservoir; 22. Ion sensitive film; 23. First metal electrode; 24. First substrate. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0021] In the description of the present invention, it should be understood that, unless otherwise expressly specified and limited, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0022] Furthermore, unless otherwise expressly specified or limited, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise expressly specified or limited.

[0023] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0024] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0025] Example: See also Figures 1 to 5 The micro multi-ion sensing system based on the NOT gate array in the preferred embodiment of the present invention includes a molybdenum disulfide NOT gate array and a multi-ion sensitive unit 2 connected to each other, so as to simultaneously detect the concentrations of multiple ions in the solution to be tested through the multi-ion sensitive unit 2, and convert the concentrations of multiple ions into electrical signals for output through the molybdenum disulfide NOT gate array.

[0026] Specifically, if Figure 1 As shown in FIG, the multi-ion sensitive unit 2 in the preferred embodiment includes a liquid reservoir 21, an ion sensitive film array, a metal electrode array and a first substrate 24 arranged in sequence from top to bottom.

[0027] Among them, the liquid reservoir 21 is a cylindrical structure with two ends open, one end of which is fixedly set on the first substrate 24 for storing the solution to be tested; the metal electrode array is set on the first substrate 24 and is set in the liquid reservoir 21, and the metal electrode array specifically includes a plurality of first metal electrodes 23; the ion-sensitive film array includes a plurality of ion-sensitive films 22, each ion-sensitive film 22 is correspondingly arranged on each first metal electrode 23, each ion-sensitive film 22 contains an ion carrier, and different ion-sensitive films 22 contain different ion carriers to detect the concentration of multiple ions in the solution to be tested in the liquid reservoir 21.

[0028] More specifically, the material of the liquid reservoir 21 is either polydimethylsiloxane (PDMS) or polymethyl methacrylate (PMMA). The material of each first metal electrode 23 in the metal electrode array is related to the type of ion being measured. If the ion being measured is hydrogen ion (i.e., measuring the pH value of the solution), the first metal electrode 23 is made of TiN (titanium nitride), preferably with a thickness of 20-100 nm, and the ion-sensitive film 22 is not provided on the first metal electrode 23. If the ion being measured is other ions, the metal electrode array is a double-layer metal stack structure, with the lower metal layer being made of either Ti (titanium) or Cr (chromium), preferably with a thickness of 5-10 nm, and the upper metal layer being made of Au (gold), preferably with a thickness of 20-30 nm. The first substrate 24 is a SiO2 / Si (silicon dioxide / silicon) substrate, where the SiO2 in the SiO2 / Si substrate is preferably 200-300 nm thick.

[0029] like Figure 2 The metal electrode array in the preferred embodiment shown is provided with four first metal electrodes 23, one of which is made of TiN and is used to detect the concentration of hydrogen ions; ion-sensitive films 22 containing different ion carriers are respectively provided above the other three first metal electrodes 23, forming a multi-ion sensitive unit 2 that can simultaneously detect the concentrations of four ions.

[0030] Further, if Figure 1 As shown in , the MoS2 NOT gate array in the preferred embodiment includes a plurality of MoS2 NOT gates 1 arranged on a second substrate 19 , and the number of MoS2 NOT gates 1 corresponds to the number of ions detectable by the multi-ion sensitive unit 2 .

[0031] Specifically, the molybdenum disulfide NOT gate 1 includes a metal electrode layer, a molybdenum disulfide layer, an insulating layer, a NOT gate input terminal 11, and a NOT gate output terminal 12. The molybdenum disulfide layer, the metal electrode layer, and the NOT gate output terminal 12 are disposed on a second substrate 19. The metal electrode layer includes a second metal electrode 17 and a third metal electrode 18, respectively, disposed on either side of the NOT gate output terminal 12 and spaced apart from the NOT gate output terminal 12. The molybdenum disulfide layer includes a first molybdenum disulfide layer 15 and a second molybdenum disulfide layer 16. The first molybdenum disulfide layer 15 is disposed between the second metal electrode 17 and the NOT gate output terminal 12, and its two ends are respectively connected to the second metal electrode 17 and the NOT gate output terminal 12. The second molybdenum disulfide layer 16 is disposed between the third metal electrode 18 and the NOT gate output terminal 12, and its two ends are respectively connected to the third metal electrode 18 and the NOT gate output terminal 12.

[0032] At the same time, a first insulating layer 13 is provided on one side of the NOT gate output terminal 12, the first molybdenum disulfide layer 15 and the second metal electrode 17, and the NOT gate input terminal 11 is provided on the first insulating layer 13; a second insulating layer 14 is provided on the other side of the NOT gate output terminal 12, the second molybdenum disulfide layer 16 and the third metal electrode 18, and the end of the NOT gate output terminal 12 facing away from the second substrate 19 is extended and provided on the second insulating layer 14.

[0033] Correspondingly, each first metal electrode 23 in the metal electrode array is connected to the NOT gate input terminal 11 in the MoS2 NOT gate array in a one-to-one correspondence via a wire.

[0034] It can be understood that the above-mentioned MoS2 NOT gate 1 constitutes two n-type MoS2 field effect transistors, such as Figure 1 As shown in the figure, the NOT gate input terminal 11, the second metal electrode 17, and the NOT gate output terminal 12 respectively form the gate, source, and drain of the first transistor; at the same time, the end of the NOT gate output terminal 12 away from the second substrate 19, the end of the NOT gate output terminal 12 close to the second substrate 19, and the third metal electrode 18 respectively form the gate, source, and drain of the second transistor.

[0035] When the molybdenum disulfide NOT gate 1 is actually working, the second metal electrode 17 is grounded and a fixed positive voltage is applied to the third metal electrode 18. Then, the output voltage of the NOT gate output terminal 12 will change with the input voltage of the NOT gate input terminal 11. When the input voltage of the NOT gate input terminal 11 is less than a certain threshold value (V th1 ), the first transistor is in the off state and the second transistor is in the on state. At this time, the resistance of the first transistor is much greater than the resistance of the second transistor, and the output voltage of the NOT gate output terminal 12 is substantially consistent with the voltage of the third metal electrode 18. When the input voltage of the NOT gate input terminal 11 is greater than a certain threshold (V th2 ), the first transistor is in the on state and the second transistor is in the off state. At this time, the resistance of the second transistor is much greater than the resistance of the first transistor, and the output voltage of the NOT gate output terminal 12 is substantially consistent with the voltage of the second metal electrode 17; when the input voltage of the NOT gate input terminal 11 is greater than V th1 and less than V th2 When , the output voltage of the NOT gate output terminal 12 will change sharply along with the input voltage of the NOT gate input terminal 11 .

[0036] After the test solution is injected into the liquid reservoir 21, according to the Nernst equation, the membrane potential of the ion-sensitive film 22 will change with the change of the corresponding ion concentration (for example, the membrane potential of the sodium ion-sensitive film 22 will increase with the increase of the sodium ion concentration in the solution), and the change in membrane potential ΔV1 will be transmitted to the NOT gate input terminal 11 through the first metal electrode 23. If the voltage of the NOT gate input terminal 11 is at V before and after the change, th1 With V th2Then a small change ΔV1 in the voltage at the NOT gate input 11 will cause a large change ΔV2 in the voltage at the NOT gate output 12, thereby amplifying and outputting the detection signal. The actual membrane potential change can then be calculated based on the output detection signal, and the corresponding ion concentration in the solution can be deduced.

[0037] Preferably, the molybdenum disulfide layer is a single atomic layer single atomic layer single crystal structure, and its thickness is 0.5-1 nm, more preferably 0.7 nm.

[0038] Preferably, the first insulating layer 13 and the second insulating layer 14 are made of any one of aluminum oxide, hafnium oxide, and silicon dioxide, and have a thickness of 30-50 nanometers.

[0039] Preferably, the NOT gate input terminal 11, the NOT gate output terminal 12 and the metal electrode layer are all double-layer metal stack structures; wherein the material of the lower metal layer is any one of Ti and Cr, with a thickness of 5~10nm, and the material of the upper metal layer is any one of Au, Ag (silver), Cu (copper), Pd (palladium), Pt (platinum), with a thickness of 20~30nm.

[0040] Preferably, the second substrate 19 is a SiO 2 / Si substrate, wherein the thickness of SiO 2 in the SiO 2 / Si substrate is 200-300 nm.

[0041] Furthermore, the present invention also relates to a method for preparing a multi-ion sensitive unit, which is used for preparing the multi-ion sensitive unit 2, and specifically comprises the following steps: (1) coating a photoresist on the surface of the first substrate 24 and patterning the photoresist; Specifically, a layer of negative photoresist was spin-coated on the sample surface using a spin coater at a speed of 700-3000 rpm for 9-40 seconds, and then baked on a 120°C hot plate for 2 minutes. The sample was then patterned by exposing it for 20 seconds, baking it at 120°C for 2 minutes, and soaking it in a developer for 1 minute.

[0042] (2) growing metal on the surface of the photoresist using a sputtering process, and removing the photoresist and the metal on the photoresist after sputtering to obtain a metal electrode array; Specifically, a sputtering process was used to grow 5-10 nanometers of Ti and 20-30 nanometers of Au on the sample surface. After sputtering, the sample was immersed in acetone to remove the photoresist and the metal on it, thus preparing a metal electrode array.

[0043] (3) Dropping each ion carrier and its corresponding sensitive solution onto the surface of the corresponding first metal electrode 23 and drying them to obtain an ion-sensitive thin film array; Taking the preparation of the sodium ion sensitive film 22 as an example, 10 mg of sodium ion carrier X, 5.5 mg of sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate (Na-TFPB), 330 mg of polyvinyl chloride (PVC), and 654.5 mg of dioctyl sebacate (DOS) were dissolved in 6.6 ml of tetrahydrofuran (THF), stirred evenly, and placed in a refrigerator at 4°C for 24 hours; 2 μl of the above mixed solution was dropped on the surface of the first metal electrode 23, and after drying in air for 24 hours, the sodium ion sensitive film 22 was obtained.

[0044] Accordingly, when preparing other ion-sensitive films 22, it is only necessary to replace the above-mentioned sodium ion carrier X with other ion carriers, such as valinomycin (potassium ion carrier), calcium ion carrier II, etc., and prepare sensitive solutions of other ions, drop them on the surface of the first metal electrode 23 and dry them to obtain the corresponding ion-sensitive films 22.

[0045] (4) The liquid reservoir 21 is bonded to the first substrate 24 to complete the preparation of the multi-ion sensitive unit 2.

[0046] A polymethyl methacrylate (PMMA) liquid reservoir 21 is processed by a numerical control machine tool, and the liquid reservoir 21 is bonded to the first substrate 24 by glue.

[0047] Furthermore, the present invention also relates to a method for preparing a molybdenum disulfide NOT gate array, which specifically comprises the following steps: (1) growing a monolayer of molybdenum disulfide on the surface of the second substrate 19 by chemical vapor deposition; (2) coating a photoresist on the surface of molybdenum disulfide and patterning the photoresist; In a preferred embodiment, a layer of positive photoresist is spin-coated on the surface of the SiO2 / Si substrate using a coater, the coater speed is 500~1000 rpm, the spin coating time is 9~40 seconds, and it is pre-baked on a 110°C hot plate for 2 minutes, and then exposed for 20 seconds, baked at 90°C for 1 minute, immersed in a developer for 1 minute, and post-baked at 110°C for 2 minutes to make it patterned.

[0048] (3) etching the molybdenum disulfide and removing the photoresist on the surface of the single-layer molybdenum disulfide after etching to obtain a molybdenum disulfide layer; In a preferred embodiment, an oxygen plasma etcher is used to etch a single layer of molybdenum disulfide. The etcher has a flow rate of 500 sccm, a power of 200 W, and an etching time of 4 min. After etching, the sample is immersed in an acetone solution to remove the positive photoresist on the surface of the molybdenum disulfide to prepare a molybdenum disulfide layer.

[0049] (4) coating a photoresist on the surface of the second substrate 19 and patterning the photoresist; In a preferred embodiment, a layer of negative photoresist is spin-coated on the surface of the second substrate 19 using a coating machine, wherein the rotation speed of the coating machine is 700~3000 rpm, the spinning time is 9~40 seconds, and after spin coating, it is baked on a 120℃ hot plate for 2 minutes, and then exposed for 20 seconds, baked at 120℃ for 2 minutes, and immersed in a developer for 1 minute to make it patterned.

[0050] (5) growing metal on the surface of the photoresist by an evaporation process, and removing the photoresist and the metal on the photoresist after evaporation to obtain a metal electrode layer and a portion of the NOT gate output terminal 12; In a preferred embodiment, a 5-10 nanometer thick layer of Ti and a 20-30 nanometer thick layer of Au are grown on the sample surface using an evaporation process. After evaporation, the sample is immersed in acetone to remove the photoresist and the metal on it, thereby forming the second metal electrode 17, the third metal electrode 18, and a portion of the NOT gate output terminal 12.

[0051] (6) Using evaporation technology to grow metal on the sample surface, and using atomic layer deposition technology to grow metal oxide on the sample surface; In a preferred embodiment, 1 nanometer Al (aluminum) is grown on the sample surface by an evaporation process; then, the sample is allowed to stand in air for at least 3 hours, and 30 nanometers of aluminum oxide is grown on the sample surface by an atomic layer deposition process.

[0052] (7) Coating a photoresist on the surface of the metal oxide and patterning the photoresist; A layer of negative photoresist was spin-coated on the sample surface using a spin coater at a speed of 700-3000 rpm for 9-40 seconds, followed by pre-baking on a 120°C hot plate for 2 minutes. The sample was then patterned by exposing for 20 seconds, baking at 120°C for 2 minutes, soaking in a developer for 1 minute, and post-baking at 120°C for 2 minutes.

[0053] (8) etching the metal oxide and removing the photoresist on the surface of the metal oxide after etching to obtain a first insulating layer 13 and a second insulating layer 14; In a preferred embodiment, the sample is immersed in a developer, removed every 5 minutes, and rinsed with deionized water until the surface aluminum oxide is completely etched. After etching, the sample is immersed in acetone to remove the photoresist on the aluminum oxide surface, thereby forming the first insulating layer 13 and the second insulating layer 14.

[0054] (9) Spin-coat a layer of photoresist on the sample surface and pattern the photoresist; In a preferred embodiment, a layer of negative photoresist is spin-coated on the surface of the sample using a spin coater at a speed of 700 to 3000 rpm for 9 to 40 seconds, and then baked on a 120°C hot plate for 2 minutes. The sample is then patterned by exposing it for 20 seconds, baking it at 120°C for 2 minutes, and soaking it in a developer for 1 minute.

[0055] (10) A sputtering process is used to grow metal on the sample surface, and the photoresist and the metal on the photoresist are removed after sputtering to obtain the NOT gate input terminal 11 and the remaining NOT gate output terminal 12, thereby completing the preparation of the MoS2 NOT gate array.

[0056] In a preferred embodiment, a sputtering process is used to grow 5-10 nanometers of Ti and 20-30 nanometers of Pd on the sample surface. After sputtering, the sample is immersed in acetone to remove the negative photoresist and the metal on the negative photoresist, thereby forming the NOT gate input terminal 11 and the remaining NOT gate output terminal 12.

[0057] Furthermore, in a preferred embodiment, the electrical performance of the MoS2 NOT gate array is tested.

[0058] The second metal electrode 17, the NOT gate output terminal 12 and the NOT gate input terminal 11 are used as the source, drain and gate of the MoS2 field effect transistor respectively, and the transfer characteristic curve of the MoS2 field effect transistor is tested, as shown in FIG. Figure 3 As shown in the figure, the prepared molybdenum disulfide field effect transistor is n-type and has an on / off ratio of 10 5 , the subthreshold swing is about 400mV / dec, and it has good gate control capability.

[0059] The NOT gate input terminal 11, the NOT gate output terminal 12, the second metal electrode 17 and the third metal electrode 18 are used as the NOT gate input terminal, output terminal, ground terminal and power terminal respectively, and the transfer characteristic curve of the MoS2 NOT gate 1 is tested, as shown in FIG. Figure 4 As shown in the figure, when the input voltage is less than -2V, the output voltage is close to the power supply voltage; when the input voltage is greater than -1.5V, the output voltage is approximately 0V, showing a good NOT gate switch characteristic.

[0060] Figure 5 Based on Figure 4 The calculated NOT gate gain curve shows that when the input voltage is in the range of approximately -1.8V to -1.6V, the NOT gate gain is greater than 1, which can achieve super-Nernstian limit detection.

[0061] Compared to conventional methods using field-effect transistors to detect ion concentrations, the miniature multi-ion sensing system based on the NOT gate array in this invention surpasses the Nernst limit, enabling ultra-high-sensitivity measurements of multiple ion concentrations simultaneously. Furthermore, because the NOT gate output is a voltage, it avoids the need to measure tiny currents, facilitating subsequent signal processing.

[0062] The present invention relates to a miniature multi-ion sensing system based on a NOT gate array and its preparation method. The prepared NOT gate array uses a single layer of MoS2 as the channel material, with lateral dimensions on the order of micrometers and a thickness on the order of nanometers. This significantly reduces the overall size of the device and enables a more integrated sensing system. Furthermore, compared to conventional NOT gates based on silicon-based field-effect transistors, the NOT gate based on MoS2 field-effect transistors has a lower turn-on voltage and on-state current, resulting in overall power consumption in the order of microwatts. Sodium ion sensing systems based on the NOT gate structure are more suitable for highly sensitive, long-term, real-time monitoring of ion concentrations in the human body.

[0063] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A micro multi-ion sensing system based on a NOT gate array, characterized in that: Including multiple ion sensitive units and molybdenum disulfide NOT gate array; The multi-ion sensitive unit includes a metal electrode array, an ion sensitive film array and a liquid reservoir; the liquid reservoir is arranged on a first substrate and is used to store a solution to be tested; the metal electrode array is arranged on the first substrate and in the liquid reservoir, and includes a plurality of first metal electrodes; The ion-sensitive film array includes a plurality of ion-sensitive films disposed on each of the first metal electrodes, and different ion-sensitive films contain different ion carriers; The MoS2 NOT gate array comprises a plurality of MoS2 NOT gates arranged on a second substrate; The molybdenum disulfide NOT gate comprises a metal electrode layer, a molybdenum disulfide layer, a NOT gate input terminal and a NOT gate output terminal; the NOT gate output terminal, the molybdenum disulfide layer and the metal electrode layer are arranged on the second substrate, and the molybdenum disulfide layer comprises a first molybdenum disulfide layer and a second molybdenum disulfide layer; the metal electrode layer comprises a second metal electrode and a third metal electrode spaced apart on both sides of the NOT gate output terminal, the second metal electrode and the NOT gate output terminal are connected to both ends of the first molybdenum disulfide layer, and the third metal electrode and the NOT gate output terminal are connected to both ends of the second molybdenum disulfide layer; a first insulating layer is arranged on one side of the NOT gate output terminal, the first molybdenum disulfide layer and the second metal electrode, and the NOT gate input terminal is arranged on the first insulating layer; a second insulating layer is arranged on the other side of the NOT gate output terminal, the second molybdenum disulfide layer and the third metal electrode, and the NOT gate output terminal extends from the second substrate and is arranged on the second insulating layer; Each of the first metal electrodes in the metal electrode array is connected to each of the NOT gate input terminals in the molybdenum disulfide NOT gate array in a one-to-one correspondence.

2. The micro multi-ion sensing system based on a NOT gate array according to claim 1, characterized in that: The molybdenum disulfide layer is a single atomic layer single crystal structure with a thickness of 0.5-1 nm.

3. The micro multi-ion sensing system based on a NOT gate array according to claim 1, characterized in that: The first insulating layer and the second insulating layer are made of any one of aluminum oxide, hafnium oxide, and silicon dioxide, and have a thickness of 30-50 nm.

4. The micro multi-ion sensing system based on a NOT gate array according to claim 1, characterized in that: The NOT gate input end, the NOT gate output end and the metal electrode layer are all double-layer metal stack structures; wherein the material of the lower metal layer is any one of Ti and Cr, with a thickness of 5~10nm, and the material of the upper metal layer is any one of Au, Ag, Cu, Pd, Pt, with a thickness of 20~30nm.

5. The micro multi-ion sensing system based on a NOT gate array according to claim 1, characterized in that: When the ion to be measured is a hydrogen ion, the corresponding first metal electrode is made of TiN with a thickness of 20 to 100 nm, and no ion-sensitive film is provided on the first metal electrode; when the ion to be measured is other ions, the corresponding first metal electrode is a double-layer metal stack structure, wherein the lower metal is any one of Ti and Cr with a thickness of 5 to 10 nm, and the upper metal is Au with a thickness of 20 to 30 nm.

6. The micro multi-ion sensing system based on a NOT gate array according to claim 1, characterized in that: The first substrate and the second substrate are both SiO2 / Si substrates, and the thickness of SiO2 in the SiO2 / Si substrate is 200-300 nm.

7. The micro multi-ion sensing system based on a NOT gate array according to claim 1, characterized in that: The material of the liquid storage tank is any one of polydimethylsiloxane and polymethyl methacrylate.

8. A method for preparing a multi-ion sensitive unit, used for preparing the multi-ion sensitive unit in the micro multi-ion sensing system based on a NOT gate array according to any one of claims 1 to 7, characterized in that: The steps include: (1) coating a photoresist on the surface of the first substrate and patterning the photoresist; (2) growing metal on the surface of the photoresist using a sputtering process, and removing the photoresist and the metal on the photoresist after sputtering to obtain a metal electrode array; (3) dropping each ion carrier and its corresponding sensitive solution onto the surface of its corresponding first metal electrode and drying them to obtain an ion-sensitive thin film array; (4) Bonding the liquid reservoir to the first substrate to complete the preparation of the multi-ion sensitive unit.

9. A method for preparing a molybdenum disulfide NOT gate array, used for preparing the molybdenum disulfide NOT gate array in a micro multi-ion sensing system based on a NOT gate array according to any one of claims 1 to 7, characterized in that: The steps include: (1) growing a monolayer of molybdenum disulfide on the surface of the second substrate by chemical vapor deposition; (2) coating a photoresist on the surface of the monolayer molybdenum disulfide and patterning the photoresist; (3) etching the molybdenum disulfide and removing the photoresist on the surface of the single-layer molybdenum disulfide after etching to obtain a molybdenum disulfide layer; (4) coating a photoresist on the surface of the second substrate and patterning the photoresist; (5) Using evaporation process to grow metal on the surface of photoresist, and removing the photoresist and the metal on the photoresist, the metal electrode layer and part of the NOT gate output end after evaporation; (6) Using evaporation technology to grow metal on the sample surface, and using atomic layer deposition technology to grow metal oxide on the sample surface; (7) Coating a photoresist on the surface of the metal oxide and patterning the photoresist; (8) etching the metal oxide and removing the photoresist on the surface of the metal oxide after etching to obtain a first insulating layer and a second insulating layer; (9) Spin-coat a layer of photoresist on the sample surface and pattern the photoresist; (10) A sputtering process is used to grow metal on the sample surface, and the photoresist and the metal on the photoresist are removed after sputtering to obtain the NOT gate input end and the remaining NOT gate output end, thereby completing the preparation of the MoS2 NOT gate array.

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