A Plug-and-Play Composite Ion Detector Based on OECT Array and Its Preparation Method

Abstract

The present invention discloses a pluggable composite ion detector based on an OECT array and its preparation method, belonging to the technical field of organic electrochemical transistors. The detector includes a substrate, a source electrode line, a semiconductor layer, a drain electrode line, a packaging layer, an ion driving layer, a sodium ion selective membrane, a potassium ion selective membrane, a calcium ion selective membrane, and a protective layer. In addition, the present invention also proposes a preparation method for a pluggable composite ion detector based on an OECT array. The present invention breakthroughly introduces an innovative pluggable composite ion detection scheme, realizing high-precision real-time monitoring of ion concentration in liquid samples. Through unique principles and methods, this technology has achieved a major breakthrough in the field of biomedical research, significantly expanding the scope and depth of biomedical research. The present invention has opened up new application avenues in key fields such as drug screening and disease diagnosis, providing an efficient, accurate, and innovative solution.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic electrochemical transistors, and particularly relates to a pluggable composite ion detector based on an organic electrochemical transistor (OECT) array and a preparation method thereof. Background Art

[0002] Organic Electrochemical Transistor (OECT) has a simple preparation process, low power consumption characteristics and flexible design, and has emerged in the field of organic electronics, being hailed as a rising star. The high sensitivity, low operating voltage and high transconductance of OECT make it an ideal choice for detecting biochemical signals, especially showing broad application prospects in the field of health detection. Particularly notable is that OECT can be fabricated into various forms and sizes according to different design and manufacturing processes, which endows them with the ability to adapt to different application scenarios, such as realizing specific detection and real-time monitoring of biological metabolites and biomarkers. This unique advantage enables OECT to show great application potential in many frontier fields such as biochemical sensors, neural interface devices and neuromorphic computing.

[0003] The OECT array, a precision microarray composed of numerous independent OECTs, where each transistor can operate individually or cooperate with other transistors to perform specific detection tasks. Such an array has extensive application potential in the fields of monitoring and detection. In the design of the pluggable composite ion detector of the OECT array, the key technology lies in ensuring the excellent stability of the probe-type detector, enabling it to be fully immersed in the detection liquid and maintaining long-term ion detection stability. By finely dividing the working area inside the array, this technology can achieve sensitive sensing of multiple ions, thus providing diverse ion detection regions in a single array, enhancing the accuracy and flexibility of detection. This design not only improves the detection efficiency but also expands the application scope of the OECT array in the analysis of complex samples, providing strong technical support for high-precision ion monitoring. In addition, the external circuit in the pluggable composite ion detection technology of the OECT array can independently drive each transistor in the array, which brings great flexibility in device control. Currently, there are still the following problems in ion concentration detection technology. One is the problem of insufficient uniformity and stability in the thickness of the ion-selective membrane prepared by traditional processes; the second is the insufficient sensitivity of traditional transistors in ion detection, making it difficult to achieve precise identification and quantitative analysis of specific ions in body fluids; the third is that traditional ion detection technology faces cost-benefit challenges, with expensive equipment investment and long detection cycles, which limits its popularization in rapid detection and large-scale applications.

[0004] The application of the pluggable composite ion detector based on the OECT array in the detection field marks an interdisciplinary innovation wave, integrating research results from multiple fields such as materials science, electronic engineering, and biomedicine. The exploration in this field not only indicates the forefront of technological innovation but also has the potential to become a new engine leading future technological development, showing great development potential and broad application prospects. Summary of the Invention

[0005] The object of the present invention is to provide a pluggable composite ion detector based on an organic electrochemical transistor (OECT) array and its preparation method to solve the technical problems of insufficient sensitivity of traditional transistors in ion detection in the prior art, difficulty in accurately identifying and quantitatively analyzing specific ions in body fluids, and high cost.

[0006] To solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0007] A pluggable composite ion detector based on an OECT array, the detector includes a substrate, a source electrode line, a semiconductor layer, a drain electrode line, a packaging layer, an ion driving layer, a sodium ion selective membrane, a potassium ion selective membrane, a calcium ion selective membrane, and a protective layer;

[0008] On the surface of the substrate with three parallel micro-needle protrusions, a rectangular strip-shaped source electrode line is provided. The source electrode line is closely attached to the horizontal center position at the top of each micro-needle protrusion on the substrate, vertically extends upward along one side of the micro-needle protrusion on the substrate, penetrates the substrate, and is exposed at the other end of the substrate; a square semiconductor layer is precisely covered on the surface of the source electrode line at the top of the micro-needle protrusion, and the width of the semiconductor layer is greater than the width of the source electrode line; in the central surface of the semiconductor layer, a drain electrode line is provided. The drain electrode line starts from the surface of the semiconductor layer, vertically extends upward along one side of the micro-needle protrusion of the substrate, penetrates the substrate, and is exposed at the other end of the substrate; the source electrode line and the drain electrode line at the top of the micro-needle protrusion are perpendicular to each other; the width of the drain electrode line is less than the width of the semiconductor layer, and the drain electrode line does not completely cover or block the semiconductor part; a packaging layer is provided in the area at the top of the micro-needle protrusion of the substrate, and a square hole is provided in the center of the packaging layer to expose the semiconductor layer at the perpendicular intersection position of the drain electrode line and the source electrode line; the substrate with three parallel micro-needle protrusions forms three basic OECT devices by setting the source electrode line, the semiconductor layer, the drain electrode line, and the packaging layer;

[0009] An ion drive layer is provided on the surface of the encapsulation layer, covering the working area at the top of the microneedle protrusions; three basic OECT devices covered with the ion drive layer are respectively sleeved with sleeve-shaped sodium ion selective membranes, potassium ion selective membranes, and calcium ion selective membranes to form three OECT devices with the ability to selectively detect specific ions; at the open ends of the sodium ion selective membrane, potassium ion selective membrane, and calcium ion selective membrane, that is, at the ends of the sleeve-like structure, a surrounding sealing protection layer is provided; after the three OECT devices with the ability to selectively detect specific ions are provided with the sealing protection layer, a multifunctional OECT array is formed.

[0010] Furthermore, the size of each individual OECT device does not exceed 10 µm × 10 µm; during the process of detecting the ion concentration, the OECT array is inserted into the test solution so that the devices in each working area can independently detect specific ions.

[0011] Furthermore, the substrate is one of glass, silicon wafer, polyethylene terephthalate PET, polyethylene naphthalate PEN, polydimethylsiloxane PDMS, or polyurethane PU.

[0012] Furthermore, the electrode width range of the source line and the drain line is 1 to 10 µm, the interval between parallel source lines or drain lines is 1 to 100 µm, and the source line and the drain line are composed of electrochemically stable conductive materials; the gate is selected from conductive materials with or without electrochemical activity.

[0013] Furthermore, the thickness of the semiconductor layer is 10 to 200 nm, and it is composed of a composite semiconductor material that can conduct both ions and electrons, such as poly[thiophene-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-2,2'-bithiophene], poly[2,5-bis(2,5,8,11,14-pentaoxa-16)-3,6-bis(thiophen-2-yl)-2,5-dihydropyrrolo(3,4)pyrrole-1,4-dione], poly[thieno[3,2-b]thiophene-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-2,2'-bithiophene], poly(benzimidazole dibenzophenanthroline), or polyethylene glycol (diol) diacrylate.

[0014] Furthermore, the encapsulation layer is composed of an electrochemically stable insulating material, specifically one of parylene Parylene-C, cellulose, photoresist SU-8, polystyrene, polydimethylsiloxane PDMS, and polystyrene-ethylene-butene SEBS.

[0015] Furthermore, the ion drive layer is composed of an efficient ion electrolyte material, specifically one of poly(4-styrenesulfonic acid sodium salt), polyethylenedioxythiophene, or polyaniline.

[0016] Furthermore, the sodium ion selective membrane adopts multiple components including sodium ions, tetrahydrofuran, high molecular weight PVC, and bis(2-ethylhexyl) phthalate plasticizer mediator, and bis(2-ethylhexyl) phthalate plasticizer; the potassium ion selective membrane adopts multiple components including potassium ions, tetrahydrofuran, high molecular weight PVC, and bis(2-ethylhexyl) phthalate plasticizer; the calcium ion selective membrane adopts multiple components including calcium ions, tetrahydrofuran, high molecular weight PVC, and bis(2-ethylhexyl) phthalate plasticizer.

[0017] Furthermore, the protective layer is selected from materials with electrochemical stability and protective effects, specifically AR9403 transparent glue.

[0018] In addition, the present invention also proposes a preparation method of a pluggable composite ion detector based on an OECT array, and the method includes the following steps:

[0019] Step S1: Use isopropanol to ultrasonically clean the substrate with three parallel micro-needle protrusions; after cleaning, perform ultraviolet ozone treatment.

[0020] Step S2: Evaporate and deposit on the top and side surfaces of each micro-needle protrusion of the substrate. First, deposit 3 nm thick chromium; subsequently, evaporate and deposit 150 nm thick gold on the chromium to form the source electrode line.

[0021] Step S3: Clean the substrate with the evaporated source electrode line layer again by ultraviolet ozone treatment.

[0022] Step S4: Spin-coat to prepare the semiconductor layer.

[0023] Step S5: On the surface of the semiconductor layer and the side surfaces of the micro-needle protrusions, prepare a 150 nm thick gold layer as the drain electrode line through evaporation and deposition process.

[0024] Step S6: Spin-coat to prepare the encapsulation layer; the substrate with three parallel micro-needle protrusions forms three basic OECT devices by preparing the source electrode line, semiconductor layer, drain electrode line, and encapsulation layer.

[0025] Step S7: Spin-coat to prepare the ion driving layer.

[0026] Step S8: Prepare sodium ion selective membrane, potassium ion selective membrane, and calcium ion selective membrane; insert the three basic OECT devices covered with the ion driving layer into the sleeve-shaped sodium ion selective membrane, potassium ion selective membrane, and calcium ion selective membrane respectively, and completely cover most areas of the micro-needle protrusion structure.

[0027] Step S9: At the open ends of the sodium ion selective membrane, potassium ion selective membrane, and calcium ion selective membrane, i.e., the ends of the sleeve-like structure, a circumferential sealed protective layer is prepared for each to form a multi-functional OECT array, and a pluggable composite ion detector based on the OECT array is obtained.

[0028] Compared with the prior art, the present invention has the following beneficial technical effects:

[0029] 1) On the one hand, the present invention ensures that a single OECT device has a uniform ion selective membrane and a highly stable protective layer. On the other hand, it further improves the sensitivity of the OECT array in ion concentration detection. Through the pluggable composite ion detector of the OECT array of the present invention, not only the working efficiency of each device in the OECT array is significantly improved, but also the high-precision simultaneous detection of multiple ions by a single sensor is realized.

[0030] 2) The pluggable OECT array composite ion detector adopted by the present invention performs excellently in reducing energy consumption and heat release, and at the same time achieves higher transconductance and better detection accuracy. In the external circuit design, the present invention effectively avoids the limitations of traditional single-drive and read circuits, and precisely reads and monitors the signals of specific OECTs by using the structural advantages. The OECT array ion detection technology of the present invention shows obvious advantages in terms of accuracy, occupied area, energy consumption, driving flexibility, and signal amplification accuracy, fully meeting the detection requirements based on the OECT array.

[0031] 3) By using a vertical structure device, the channel length can be controllably adjusted within the range of 1 - 10 µm, and then various transistor indexes such as current density, switching rate, and capacitance size can be adjusted according to the channel length;

[0032] 4) By using an organic semiconductor layer, under the action of the gate voltage, ions in the electrolyte layer are incorporated into or precipitated from the semiconductor, effectively controlling the carrier concentration in the semiconductor and changing the conductivity of the semiconductor;

[0033] 5) The ion selective membrane prepared by using a sleeve-like structure can precisely control the thickness of the ion selective membrane, thus significantly improving the accuracy of the detection signal;

[0034] 6) The protective layer designed with a circumferential sealed structure can significantly enhance the effectiveness of the protective layer, ensuring excellent long-term stability of the detection device in the liquid to be measured;

[0035] 7) By using a pluggable detection technology, the detection efficiency can be significantly improved and the accuracy of the detection result can be ensured;

[0036] 8) When preparing the drain line of the present invention, the contact between the drain and the source can be effectively avoided, thus preventing device short - circuit; meanwhile, this structure is applicable to various electrode preparation methods, including evaporation, sputtering, etc.;

[0037] 9) The plug - and - play composite ion detection method based on the OECT array provided by the present invention can simultaneously detect and analyze the concentrations of multiple ions at the micron scale, thus having the ability to observe and analyze human blood and waste liquid;

[0038] 10) The present invention proposes an innovative plug - and - play composite ion detection technology based on the OECT array. This technology allows for the detection of multiple different ions by replacing specific ion carriers in the ion - selective membrane. This method significantly reduces the manufacturing and design costs, while improving the preparation speed and efficiency of the OECT ion sensor.

[0039] 11) The present invention has break - throughly introduced an innovative plug - and - play composite ion detection scheme, achieving high - precision real - time monitoring of ion concentrations in liquid samples. This innovation not only broadens the boundaries of biomedical research, but also opens up new application paths in fields such as drug screening and disease diagnosis. It brings unprecedented detection tools and methods to clinical research, indicating a revolution in the fields of medicine and life sciences. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0041] Figure 1 are the front - view cross - sectional view, bottom view and top view of the plug - and - play composite ion detector based on the OECT array of the present invention.

[0042] Figure 2 are the front - view and bottom - view hierarchical structure diagrams of the plug - and - play composite ion detector based on the OECT array of the present invention.

[0043] Figure 3 is the transfer characteristic curve of the output current.

[0044] Figure 4 are the detection curves of different ion concentrations.

[0045] Description of the reference numerals in the figure: 1 - substrate; 2 - source line; 3 - semiconductor layer; 4 - drain line; 5 - encapsulation layer; 6 - ion driving layer; 7 - sodium ion selective membrane; 8 - potassium ion selective membrane; 9 - calcium ion selective membrane; 10 - protective layer; 11 - detection liquid; 12 - gate; 13 - circuit probe clamp. Detailed implementation manners

[0046] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0047] A pluggable composite ion detector based on an OECT array proposed by the present invention, as Figure 1 - Figure 2 shown, the detector includes a substrate 1, a source line 2, a semiconductor layer 3, a drain line 4, an encapsulation layer 5, an ion driving layer 6, a sodium ion selective membrane 7, a potassium ion selective membrane 8, a calcium ion selective membrane 9, and a protective layer 10.

[0048] Figure 1 In (a), (b), and (c) in, the front view cross-sectional view, bottom view, and top view of the pluggable composite ion detector based on the OECT array of the present invention are respectively shown. Figure 2 is the front view and bottom view hierarchical structure diagram of the pluggable composite ion detector based on the OECT array of the present invention.

[0049] In Figure 2 on the surface of the substrate 1 with three parallel micro-needle protrusions shown in (a) in, a rectangular strip-shaped source line 2 is arranged. The source line 2 is closely attached to the horizontal center position at the top of each micro-needle protrusion on the substrate 1, and vertically extends upward along one side of the micro-needle protrusion on the substrate 1, penetrating the substrate 1 and exposing at the other end of the substrate, as Figure 2 shown in (b) in. As Figure 2 shown in (c) in, a square semiconductor layer 3 is precisely covered on the surface of the source line 2 at the top of the micro-needle protrusion. The width of the semiconductor layer 3 is greater than the width of the source line 2. As Figure 2 shown in (d) in, on the central surface of the semiconductor layer 3, a drain line 4 is arranged. The drain line 4 starts from the surface of the semiconductor layer 3 and vertically extends upward along one side of the micro-needle protrusion on the substrate 1 (adjacent to the source line 2 but on a different side). The drain line 4 penetrates the substrate 1 and exposes at the other end of the substrate to realize external connection; the source line 2 at the top of the micro-needle protrusion is perpendicular to the drain line 4; the width of the drain line 4 is less than the width of the semiconductor layer 3, and the drain line 4 does not completely cover or block the semiconductor part. As Figure 2As shown in (e), an encapsulation layer 5 is provided at the top region of the micro-needle protrusions of the substrate 1. A square hole is provided at the exact center of the encapsulation layer 5 to expose the semiconductor layer located at the perpendicular intersection position of the drain line and the source line. Three substrates with parallel micro-needle protrusions form three basic OECT devices by arranging the source line 2, the semiconductor layer 3, the drain line 4, and the encapsulation layer 5.

[0050] The size of each individual OECT device does not exceed 10 µm × 10 µm. During the process of ion concentration detection, the OECT array is inserted into the liquid to be measured, enabling the devices in each working area to independently detect specific ions.

[0051] As Figure 2 shown in (f), an ion driving layer 6 is provided on the surface of the encapsulation layer 5, covering the working area at the top of the micro-needle protrusions. As Figure 2 shown in (g), three basic OECT devices covered with the ion driving layer 6 are respectively sleeved with a sleeve-shaped sodium ion selective membrane 7, a potassium ion selective membrane 8, and a calcium ion selective membrane 9 to form three OECT devices capable of selectively detecting specific ions. As Figure 2 shown in (h), at the open ends of the sodium ion selective membrane 7, the potassium ion selective membrane 8, and the calcium ion selective membrane 9, that is, at the end of the sleeve-like structure, a surrounding sealing protection layer 10 is provided to ensure the stability and sealing of the selective membrane. After the three OECT devices capable of selectively detecting specific ions are provided with the sealing protection layer, a multi-functional OECT array is formed, that is, a pluggable composite ion detector based on an OECT array proposed by the present invention.

[0052] The pluggable composite ion detector based on an OECT array proposed by the present invention is detected in the following manner:

[0053] As Figure 2 shown in (i), the working area of the multi-functional OECT array is completely immersed in the liquid to be detected 11. As Figure 2 shown in (j), the gate 12 is partially inserted into the liquid to be detected 11 to ensure sufficient contact with the liquid to be detected 11, while the other part of the gate remains outside the liquid for electrical connection and control. As Figure 2 shown in (k), external circuit probe clips 13 are applied to the exposed ends of the source line 2 and the drain line 4 penetrating the substrate 1 for connection; voltage signals are applied to the gate 12 and the drain line 4, and the source line 2 is grounded. Under the action of the gate voltage and the source-drain voltage between the drain line 4 and the source line 2, the ions in the liquid to be detected 11 can drive the ions in the ion driving layer to penetrate into or precipitate out of the semiconductor layer through osmosis, thereby realizing the detection of the ion concentration in the liquid to be detected on the surface of the OECT array device.

[0054] The pluggable composite ion detector based on the OECT array is detected through an external circuit, and the external circuit includes a gate driving module, a drain driving module, a current signal acquisition module, and a voltage signal reading module. The gate driving module is connected to the gate of the OECT array to apply a DC bias voltage with a digital-to-analog converter; the drain driving module is connected to the ends of the drain line electrodes of the OECT array one by one. According to the ion detection requirements, a multiplexer (MUX) is used to select one of the multiple drain lines in the OECT array, and a digital-to-analog converter is used to apply a DC bias voltage; the current signal acquisition module is connected to the ends of the source line electrodes of the OECT array one by one, and is used to acquire the current output from multiple source lines in the OECT array; the voltage signal reading module is connected to the output ends of the current signal acquisition module one by one, and an analog-to-digital converter is used to acquire the voltage output by the current signal acquisition module after passing through a transconductance amplifier.

[0055] The external circuit can interact with all devices in the OECT array. The interaction is defined as achieving the gating control and reading operation of any single OECT device by defining the combination of rows and columns, that is, driving a single OECT device by applying gate and drain voltages, and obtaining a readable voltage signal through source current acquisition and transconductance amplification. The external circuit has the ability to configure logic codes, and can flexibly set and adjust the combination of rows and columns according to different detection requirements to achieve the gating control and reading of specific OECT devices, and achieve the effect of OECT array signal acquisition.

[0056] Further, the substrate is one of glass, silicon wafer, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polydimethylsiloxane (PDMS), or polyurethane (PU).

[0057] Further, the electrode widths of the source line and the drain line range from 1 to 10 µm, and the distance between parallel source lines or drain lines is from 1 to 100 µm. The source line and the drain line are composed of electrochemically stable conductive materials, specifically one of gold, platinum, carbon nanotubes, or graphene; the gate is made of a conductive material with or without electrochemical activity, specifically one of gold, silver, poly(3,4-ethylenedioxythiophene):polystyrenesulfonate, carbon nanotubes, graphene, or graphdiyne.

[0058] Further, the thickness of the semiconductor layer is 10 to 200 nm, and a composite semiconductor material having both ion-conducting and electron-conducting properties is used, such as poly[thiophene-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-2,2'-bithiophene], poly[2,5-bis(2,5,8,11,14-pentaoxa-16)-3,6-bis(thiophen-2-yl)-2,5-dihydropyrrolo(3,4)pyrrole-1,4-dione], poly[thieno[3,2-b]thiophene-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-2,2'-bithiophene], poly(benzimidazole dibenzophenanthroline) or polyethylene glycol (diol) diacrylate.

[0059] Further, the encapsulation layer is made of an electrochemically stable insulating material, specifically one of parylene Parylene-C, cellulose, photoresist SU-8, polystyrene, polydimethylsiloxane PDMS, and polystyrene-ethylene-butene SEBS.

[0060] Further, the ion driving layer is made of an efficient ion electrolyte material, specifically one of poly(4-styrenesulfonic acid sodium salt), poly(ethylenedioxythiophene) or polyaniline.

[0061] Further, the sodium ion selective membrane, potassium ion selective membrane, and calcium ion selective membrane are made of electrochemically stable materials. Specifically, the sodium ion selective membrane is composed of sodium ions and various components such as tetrahydrofuran, high molecular weight PVC, bis(2-ethylhexyl) phthalate plasticizer mediator, and bis(2-ethylhexyl) phthalate plasticizer; the potassium ion selective membrane is composed of potassium ions and various components such as tetrahydrofuran, high molecular weight PVC, and bis(2-ethylhexyl) phthalate plasticizer; the calcium ion selective membrane is composed of calcium ions and various components such as tetrahydrofuran, high molecular weight PVC, and bis(2-ethylhexyl) phthalate plasticizer.

[0062] Further, the protective layer is made of a material having electrochemical stability and a protective effect, specifically AR9403 transparent adhesive.

[0063] Further, the liquid to be detected is a solution similar to human body fluid, mainly containing potassium ions, calcium ions, magnesium ions, sodium ions, phosphate ions, etc.

[0064] Next, we will specifically describe the preparation method of a pluggable composite ion sensor based on an OECT array according to the present invention in detail with reference to the above materials, which specifically includes the following steps:

[0065] Step S1: Ultrasonic cleaning with isopropyl alcohol Figure 2The substrate with three parallel micro-needle protrusions shown in (a) is cleaned for 15 minutes to remove surface dirt and organic matter. After cleaning, ultraviolet ozone treatment is carried out. Using the synergistic effect of ultraviolet light and ozone, the substrate is further surface-cleaned and disinfected for 15 minutes as well.

[0066] Step S2: On the cleaned substrate with three parallel micro-needle protrusions, evaporation is carried out on the top and side of each micro-needle protrusion. First, 3 nm thick chromium is deposited to enhance the adhesion of the gold layer. Subsequently, 150 nm thick gold is evaporated on the chromium to form a source line with a width of 10 µm, as Figure 2 shown in (b).

[0067] Step S3: The substrate with a layer of source line deposited is subjected to ultraviolet ozone cleaning treatment again for about 15 minutes.

[0068] Step S4: Spin-coating to prepare the semiconductor layer: The humidity is controlled below 10%. The top area of the micro-needle protrusions on the substrate is spin-coated with semiconductor material at a speed of 3000 rpm for 10 s; Lithography: The lithography mask is strictly aligned with the substrate coated with the organic semiconductor layer material. 365 nm ultraviolet light is used to lithograph the semiconductor thin film at the channel to crosslink it, and the uncrosslinked part is washed away to form a semiconductor layer in the channel area, as Figure 2 shown in (c).

[0069] Step S5: On the surface of the semiconductor layer and the side of the micro-needle protrusions, a 150 nm thick gold layer is prepared as the drain line by evaporation, and the width of the drain line is 10 μm, as Figure 2 shown in (d).

[0070] Step S6: Spin-coating to prepare the encapsulation layer: The humidity is controlled below 10%. The top area of the micro-needle protrusions on the substrate is spin-coated with encapsulation layer material at a speed of 3000 rpm for 10 s; Lithography: The lithography mask is strictly aligned with the substrate coated with the encapsulation layer material. 365 nm ultraviolet light is used to lithograph the encapsulation layer material outside the central position where the drain line and the source line are perpendicular to each other to crosslink it, and the uncrosslinked part is washed away, exposing the semiconductor layer at the central position where the drain line and the source line are perpendicular to each other, as Figure 2 shown in (e). The substrate with three parallel micro-needle protrusions forms three basic OECT devices by preparing the source line, semiconductor layer, drain line and encapsulation layer.

[0071] Step S7: Spin-coating to prepare the ion driving layer: Control the humidity below 10%, and spin-coat the top region of the microneedle protrusions on the substrate at a speed of 3000 rpm to uniformly coat the ion driving layer material. The spin-coating time is 10 s. Then, dry the spin-coated substrate at 130 °C for 1 hour to form the ion driving layer, as shown in (f) of Figure 2 .

[0072] Step S8: Prepare the sodium ion selective membrane, potassium ion selective membrane, and calcium ion selective membrane: Immerse three sleeve-shaped molds into electrolytes containing sodium ion selective membrane material, potassium ion selective membrane material, and calcium ion selective membrane material respectively, and then quickly pull them out to ensure that a layer of sodium ion selective membrane material, potassium ion selective membrane material, and calcium ion selective membrane material are uniformly covered on the outer walls of the three molds. Dry them at 50 °C for 10 min, and finally peel off the sodium ion selective membrane, potassium ion selective membrane, and calcium ion selective membrane from the outer walls of the molds to form the sleeve-shaped sodium ion selective membrane, potassium ion selective membrane, and calcium ion selective membrane. Insert the three basic OECT devices covered with the ion driving layer into the sleeve-shaped sodium ion selective membrane, potassium ion selective membrane, and calcium ion selective membrane respectively, ensuring that the sodium ion selective membrane, potassium ion selective membrane, and calcium ion selective membrane are in close contact with the OECT devices and completely cover most of the microneedle protrusion structures.

[0073] Step S9: Prepare a circular surrounding sealing protective layer at the open ends of the sodium ion selective membrane, potassium ion selective membrane, and calcium ion selective membrane, that is, the ends of the sleeve-shaped structures, to form a multifunctional OECT array, and obtain a pluggable composite ion detector based on the OECT array, as shown in (h) of Figure 2 .

[0074] Furthermore, when detecting composite ions, it is achieved through the following steps:

[0075] Step S10: Insert the working regions covered with the sodium ion selective membrane, potassium ion selective membrane, and calcium ion selective membrane into the liquid to be detected as the electrolyte layer, and connect the gate through the liquid to be detected, as shown in (i) and (j) of Figure 2 .

[0076] Step S11: Apply external circuit probe clips at the ends of the source line and the drain line, and detect multiple ions simultaneously, as shown in (k) of Figure 2 .

[0077] In this embodiment, the source line, drain line, and gate are prepared by one of evaporation, magnetron sputtering, spraying, inkjet printing, aerosol printing, screen printing, and laser engraving. The semiconductor layer, encapsulation layer, and electrolyte layer are prepared by one of spin coating, spraying, screen printing, inkjet printing, 3D printing, aerosol printing, electrohydrodynamic printing, or blade coating.

[0078] Next, we use a source meter to test the pluggable composite ion detector of the prepared OECT array. The test conditions are as follows:

[0079] Under the condition of a constant drain voltage (Vd = -0.1 V), during the forward scan of the gate voltage in the range from 0 V to +0.8 V, the transfer characteristics of the source output current of a single device in the OECT array are captured, and the transfer characteristic curve is plotted, as Figure 3 shown. According to the graphical results, it can be seen that under this test condition, the pluggable composite ion detector of the OECT array exhibits excellent current regulation effects. The source current (solid line) can be controlled between the orders of magnitude from 10-8 A to 10-2 A, and its transfer characteristics have good consistency.

[0080] For cation detection, under the condition of a constant drain voltage (Vd = 0.1 V), a forward scan of the gate-source voltage is performed from +0.1 V to +0.8 V, the transfer characteristics of the output current of a single OECT device in the whole column are captured, and the transfer characteristic curve is plotted, as Figure 4 shown. According to the graphical results, it can be seen that under this test condition, the pluggable composite ion detector of the OECT array exhibits excellent current regulation effects, and its on-state current increases with the increase of the corresponding ion concentration, while the gate current remains at a relatively low level (<10-5 A), Figure 4 where (a), (b), and (c) in Figure 4 are the concentration detection curves of sodium ions, potassium ions, and calcium ions, respectively. Figure 4 In (a) of Figure 4 , the solid line represents the transfer characteristic curve of a single OECT device with a sodium ion selective membrane detecting sodium ion solutions with different concentrations, while the dashed line represents the transfer characteristic curves when detecting potassium ion and calcium ion solutions with different concentrations.

[0081] It will be understood that the present invention is described by way of some embodiments, and those skilled in the art will know that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the present invention. Additionally, under the teaching of the present invention, these features and embodiments can be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. A plug-in composite ion detector based on an OECT array, characterized in that: The detector comprises a substrate, a source line, a semiconductor layer, a drain line, a packaging layer, an ion driving layer, a sodium ion selective membrane, a potassium ion selective membrane, a calcium ion selective membrane and a protective layer; A rectangular strip source line is arranged on the surface of a substrate with three parallel microneedle protrusions. The source line is close to the horizontal center position of the top of each microneedle protrusion on the substrate, extends vertically upward along one side of the microneedle protrusion on the substrate, penetrates the substrate, and is exposed at the other end of the substrate; the surface of the source line at the top of the microneedle protrusion is accurately covered with a square semiconductor layer, and the width of the semiconductor layer is greater than the width of the source line; a drain line is arranged on the central surface of the semiconductor layer, starting from the surface of the semiconductor layer, and extending vertically upward along one side of the microneedle protrusion of the substrate, The drain line penetrates the substrate and is exposed at the other end of the substrate; the source line and the drain line at the top of the microneedle protrusion are perpendicular to each other; the width of the drain line is less than the width of the semiconductor layer, and the drain line does not completely cover or block the semiconductor part; an encapsulation layer is arranged in the top area of ​​the microneedle protrusion of the substrate, and a square hole is arranged in the center of the encapsulation layer to expose the semiconductor layer located at the mutually perpendicular intersection position of the drain line and the source line; the substrate with three parallel microneedle protrusions forms three basic OECT devices by arranging source lines, semiconductor layers, drain lines and encapsulation layers; An ion driving layer is provided on the surface of the encapsulation layer, covering the working area of ​​the top of the microneedle protrusion; The three basic OECT devices covered with the ion driving layer are respectively covered with a sleeve-shaped sodium ion selective membrane, a potassium ion selective membrane, and a calcium ion selective membrane, so as to form three OECT devices with the ability to selectively detect specific ions; a surrounding sealing protective layer is provided at the open ends of the sodium ion selective membrane, the potassium ion selective membrane, and the calcium ion selective membrane, i.e., the ends of the sleeve-shaped structure; after the three OECT devices with the ability to selectively detect specific ions are provided with the sealing protective layer, a multifunctional OECT array is formed; OECT uses a vertical structure device, and the channel length can be controlled and adjusted in the range of 1 ~ 10 µm.

2. The plug-in composite ion detector based on the OECT array according to claim 1, characterized in that: The size of each individual OECT device does not exceed 10 µm × 10 µm.

3. The plug-in composite ion detector based on OECT array according to claim 1, characterized in that: The substrate is one of glass, silicon wafer, polyethylene terephthalate PET, polyethylene naphthalate PEN, polydimethylsiloxane PDMS or polyurethane PU.

4. The plug-in composite ion detector based on the OECT array according to claim 1, characterized in that: The electrode width of the source line and the drain line ranges from 1 to 10 µm, the interval between parallel source lines or drain lines is 1 to 100 µm, the source line and the drain line are made of electrochemically stable conductive materials; the gate is made of electrochemically active or inactive conductive materials.

5. The plug-in composite ion detector based on OECT array according to claim 1, characterized in that: The thickness of the semiconductor layer is 10-200 nm, and a composite semiconductor material having both ion-conducting and electron-conducting properties is used.

6. The plug-in composite ion detector based on OECT array according to claim 1, characterized in that: The packaging layer is made of an electrochemically stable insulating material.

7. The plug-in composite ion detector based on OECT array according to claim 1, characterized in that: The ion driving layer is made of high-efficiency ion electrolyte material.

8. The plug-in composite ion detector based on OECT array according to claim 1, characterized in that: The protective layer is made of a material having electrochemical stability and protective effect.

9. A method for preparing a pluggable composite ion detector based on an OECT array, used for preparing the pluggable composite ion detector based on an OECT array according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: Step S1: using isopropyl alcohol to ultrasonically clean the substrate having three parallel microneedle protrusions; after cleaning, performing ultraviolet ozone treatment; Step S2: Evaporation is performed on the top and side of each microneedle protrusion of the substrate, firstly depositing 3 nm thick chromium; then, 150 nm thick gold is evaporated on the chromium to form a source line; Step S3: performing UV ozone cleaning again on the substrate on which a layer of source lines is deposited; Step S4: preparing a semiconductor layer by spin coating; Step S5: On the surface of the semiconductor layer and the side of the microneedle protrusion, a 150 nm thick gold layer is prepared as a drain line by evaporation process; Step S6: spin coating to prepare an encapsulation layer; three substrates with parallel microneedle protrusions are used to form three basic OECT devices by preparing source lines, semiconductor layers, drain lines and encapsulation layers; Step S7: preparing an ion driving layer by spin coating; Step S8: preparing a sodium ion selective membrane, a potassium ion selective membrane, and a calcium ion selective membrane; The three basic OECT devices covered with the ion driving layer are respectively inserted into the sleeve-shaped sodium ion selective membrane, potassium ion selective membrane, and calcium ion selective membrane, and completely cover most areas of the microneedle protrusion structure; Step S9: A surrounding sealing protective layer is prepared at the open ends of the sodium ion selective membrane, the potassium ion selective membrane, and the calcium ion selective membrane, i.e., the ends of the sleeve-like structure, to form a multifunctional OECT array, thereby preparing a plug-in composite ion detector based on the OECT array.

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