Flexible bio-memristor and preparation method thereof

Abstract

The application discloses a flexible bio-memristor and a preparation method thereof. The preparation method comprises the following steps: plugging the non-electrode area of a first filter membrane and a second filter membrane; filtering top electrode material solution by vacuum filtration to filter the top electrode material to the electrode area of the first filter membrane, and filtering bottom electrode material solution by vacuum filtration to filter the bottom electrode material to the electrode area of the second filter membrane; transferring the top electrode material on the first filter membrane to a first substrate film; coating a functional material on the bottom electrode of the bottom electrode layer to form an intermediate functional layer; and assembling the memristor. The method provided by the application is prepared based on a solution method, and has the advantages of simple process, low cost, and the core step of the whole process being performed at a relatively low temperature, so that high-temperature annealing, complex photolithography and vacuum deposition equipment required in traditional semiconductor processes are avoided, equipment investment, energy consumption and production cost are significantly reduced, and the method is especially suitable for large-scale production of flexible electronic devices.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a flexible bio-memristor and a preparation method thereof. Background Art

[0002] A memristor is a new type of electronic component (the fourth basic circuit element) defined based on the relationship between magnetic flux and charge. Its core characteristic is that it dynamically changes the resistance value by regulating internal ion migration or oxygen vacancy movement through an electric field, and "remembers" historical states, thereby simulating the information processing and storage functions of biological synapses.

[0003] With the development of flexible electronics, memristor design is gradually shifting towards a more flexible approach. By incorporating biocompatible polymers and biodegradable natural materials, combined with optimized microstructure interfaces, stable device operation and tissue adaptability under bending deformation are achieved. These flexible memristors can integrate sensing, storage, and computing functions, offering a new path for implantable health monitoring and neuromorphic systems. However, their fabrication processes still suffer from the following drawbacks: 1. The fabrication process is complex, typically requiring vacuum evaporation, photolithography, and etching; 2. Electrode materials are limited, typically requiring high-temperature resistant materials. Summary of the Invention

[0004] The main purpose of the present invention is to provide a flexible bio-memristor with simple process, no high temperature restriction on materials, good biocompatibility and a preparation method thereof.

[0005] To achieve the above objectives, the present invention provides a method for preparing a flexible bio-memristor, comprising the following steps:

[0006] S1. Preparation of top / bottom electrode layers:

[0007] S11. Blocking the non-electrode areas of the first and second filter membranes;

[0008] S12. The top electrode material solution is filtered by vacuum filtration to the electrode region of the first filter membrane, and the bottom electrode material solution is filtered by vacuum filtration to the electrode region of the second filter membrane;

[0009] S13. Transferring the top electrode material on the first filter membrane to the first substrate film to obtain a top electrode layer containing a top electrode, and transferring the bottom electrode material on the second filter membrane to the second substrate film to obtain a bottom electrode layer containing a bottom electrode;

[0010] S2. Preparation of intermediate functional layer:

[0011] Coating a functional material on the surface of the bottom electrode layer where the electrode is located and laminating the bottom electrode thereon, or coating a functional material on the surface of the top electrode layer where the electrode is located and laminating the top electrode thereon, to form an intermediate functional layer;

[0012] S3. Assembly of memristor:

[0013] The top electrode layer and the bottom electrode layer are pasted together with the surfaces where the electrodes are located facing each other, and the intermediate functional layer is pasted to the top electrode on the top electrode layer and the bottom electrode on the bottom electrode layer.

[0014] Furthermore, in step S11, the first filter membrane and the second filter membrane are both polyethersulfone (PES) filter membranes.

[0015] Furthermore, in step S11, the sealing is performed by printing graphite powder.

[0016] Furthermore, in step S12, the top electrode material is carbon nanotubes (CNTs), and the carbon nanotube solution is prepared by dispersing carbon nanotubes and sodium dodecyl sulfate in water, with a concentration of 0.2 mg / mL; the bottom electrode material is silver nanowires (AgNWs) with an average length of 20 μm and an average diameter of 70 nm, and the silver nanowire solution is prepared by dispersing silver nanowires in ethanol, with a concentration of 1 mg / mL.

[0017] Sodium dodecyl sulfate (SDS) is an anionic surfactant whose molecular structure consists of a hydrophilic head group (sulfate group) and a hydrophobic tail chain (long dodecyl chain). This amphiphilic structure enables it to effectively reduce interfacial tension. The hydrophobic tail adsorbs on the CNT surface, while the hydrophilic head extends into the water to form a hydration layer, thereby preventing CNT agglomeration and improving dispersion stability.

[0018] Furthermore, the preparation steps of silver nanowires include:

[0019] (1) uniformly dispersing polyvinyl pyrrolidone in ethylene glycol to obtain a polyvinyl pyrrolidone solution;

[0020] (2) Dissolve ferric chloride in ethylene glycol, add silver nitrate, and stir to dissolve in the dark to obtain a bimetallic solution;

[0021] (3) The polyvinyl pyrrolidone solution and the bimetallic solution were mixed and reacted at 130°C for 4 hours, followed by centrifugation to obtain a precipitate, which was then centrifuged and washed with ethanol.

[0022] Furthermore, in step S13, the transfer operation includes: mixing the raw monomers of the first substrate film or the second substrate film with a curing agent, applying the mixture to the substrate to form a semi-cured substrate film, drying the first filter membrane or the second filter membrane, attaching the membrane to the semi-cured substrate film, and further drying the membrane until the film is fully cured. Finally, the substrate and the first filter membrane or the second filter membrane are peeled off. Furthermore, the drying temperature is 65°C; the substrate is a silicon wafer.

[0023] Furthermore, in step S13, both the first and second substrate films are polydimethylsiloxane (PDMS) films. Furthermore, during transfer, the mass ratio of dimethylsiloxane monomer to curing agent is 10:1. This ratio allows for a slight excess of vinyl groups, ensuring complete reaction of the curing agent. Excessive curing agent can reduce material stability due to residual Si-H groups. However, excessive monomer content minimizes the impact of unreacted vinyl groups on performance. This condition ensures uniformity and consistent thickness of the PDMS film.

[0024] Furthermore, the operation steps of step S2 include:

[0025] S21. Plasma treatment of the top electrode layer or the bottom electrode layer;

[0026] S22. Spin-coat the functional material solution onto the processed top electrode layer or bottom electrode layer.

[0027] Furthermore, in step S2, the functional material is silk protein (Silk). Furthermore, during spin coating, the concentration of the Silk solution is 13.5 mg / mL.

[0028] Furthermore, step S3 includes applying a mixture of raw material monomers of the first substrate film or the second substrate film and a curing agent to the non-electrode area of ​​the surface where the electrodes of the top electrode layer and / or the bottom electrode layer are located, then attaching the surfaces where the electrodes of the top electrode layer and the bottom electrode layer are located, and finally drying and curing. Furthermore, the drying temperature is 65°C.

[0029] The present invention also provides a flexible bio-memristor, which is prepared according to the above preparation method.

[0030] The design principle of the present invention is:

[0031] Through laser printing technology, graphite powder acts as a physical barrier layer to form a physical barrier. The graphite powder layer after hot pressing and fixing densely fills the pores of the PES filter membrane to form a liquid-impermeable area. The covered area blocks the vacuum filtration path, so that CNTs are only deposited in the blank area without graphite powder. The blank area maintains the original porous structure of the filter membrane, allowing the CNT suspension to penetrate and deposit under negative pressure, thereby accurately replicating the electrode pattern.

[0032] Vacuum filtration rapidly removes the solvent from the CNT and AgNW solutions, while the conductive material is evenly deposited on the electrode area of ​​the PES membrane, forming a uniform conductive layer. This process not only improves electrode conductivity but also further removes impurities and bubbles from the solution through vacuum filtration, thereby improving electrode uniformity and stability.

[0033] During the transfer process, a semi-cured substrate film is first formed. This semi-cured substrate film is initially formed and has a certain degree of viscosity, which facilitates transfer. It is then dried until the film is fully cured, ensuring a tight bond between the substrate film and the electrode coating, preventing delamination or shedding during use.

[0034] Silk possesses a multi-level mesoscopic network structure, situated between the microscopic and macroscopic. Through clusters of silver nanoparticles, it forms a "mesoscopic potential energy well," significantly improving charge transfer efficiency. This is a necessary condition for the stable switching between high and low resistance states in flexible bio-memristors. Furthermore, unlike the inorganic materials commonly used as functional layers in memristors, Silk exhibits excellent biocompatibility and biodegradability.

[0035] The beneficial effects of the present invention are embodied in:

[0036] (1) The method provided by the present invention is based on solution preparation, which has simple process and low cost:

[0037] The core steps of the entire process (electrode preparation, functional layer coating, and assembly) are all performed at relatively low temperatures (drying is only 65°C) and rely primarily on solution processing and vacuum filtration. This avoids the high-temperature annealing, complex photolithography, and vacuum deposition equipment required by traditional semiconductor processes, significantly reducing equipment investment, energy consumption, and production costs, making it particularly suitable for the large-scale production of flexible electronic devices.

[0038] (2) The electrode prepared by the method provided by the present invention has high conductivity and large specific surface area:

[0039] Silver nanowires (20 μm long, 70 nm in diameter) synthesized by the ethylene glycol method have a high aspect ratio, forming a continuous conductive network that provides excellent conductivity. Their nanoscale and one-dimensional structure provide a huge specific surface area. In addition, CNT electrodes also have high conductivity, high mechanical strength and a large specific surface area.

[0040] (3) The method provided by the present invention has the advantages of layered electrode design:

[0041] The AgNWs bottom electrode provides the primary conductive pathway and excellent lateral conductivity. The CNT top electrode, covering the AgNWs, not only further enhances conductivity, but its porous network structure also facilitates penetration and contact with the intermediate functional layer (Silk), increasing the electrode / functional layer interface area and facilitating ion migration and resistive switching effects. The high mechanical strength of the CNTs also contributes to improved electrode durability.

[0042] (4) The method provided by the present invention has the capability of efficient and reliable flexible substrate integration:

[0043] The filter membrane is attached to the PDMS substrate film while it is in a semi-cured state, leveraging its adhesive properties to ensure good initial contact between the electrode and the PDMS. The subsequent complete curing process allows the PDMS molecules to form a tight physical bond with the electrode material (especially the embedded nanomaterial), firmly anchoring the electrode to the PDMS surface and effectively preventing peeling or shedding during use. This method not only avoids damage to the fragile nanowire / tube network structure caused by high temperatures, strong solvents, or strong peeling, but also perfectly compatibility with flexibility. PDMS is recognized as an excellent flexible and stretchable substrate, and the resulting transferred electrode naturally inherits the flexible properties of PDMS.

[0044] (5) The method provided by the present invention has good biocompatibility:

[0045] Silk is a natural biopolymer with excellent biocompatibility and controllable biodegradability, which provides a key foundation for the application of memristors in bioelectronics (such as implantable devices, wearable health monitoring, and neuromorphic computing interfaces). This is difficult to match with traditional inorganic or synthetic polymer memristive materials. At the same time, this method has excellent ion migration and resistive switching mechanisms. Silk contains hydrophilic amino acids and ions (such as Na + , K + ), which, under the influence of an electric field, can undergo ion migration, forming and breaking conductive filaments, thereby achieving resistive switching behavior. Its internal hydrogen bond network and β-pleated crystalline regions also provide the possibility of regulating ion transport. Silk is soluble in water to form a solution, facilitating the spin-coating process to prepare uniform, ultra-thin functional layers on flexible substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematic diagram of the structure of the flexible bio-memristor prepared in Example 2;

[0047] Figure 2 Schematic diagram of the resistive switching principle of the flexible bio-memristor prepared in Example 2;

[0048] Figure 3 This is a schematic diagram of the process for preparing a flexible bio-memristor according to Example 2;

[0049] Figure 4 This is a scanning electron microscopy image of the electrodes of the flexible bio-memristor prepared in Example 2 (AgNWs electrode on the left; CNT electrode on the right);

[0050] Figure 5 Graph showing the initial resistance and stability of the flexible bio-memristor prepared in Example 2;

[0051] Figure 6 : is a typical CV curve diagram of the flexible bio-memristor prepared in Example 2;

[0052] Figure 7 This is a diagram showing the high and low resistance state retention time of the flexible bio-memristor prepared in Example 2;

[0053] Figure 8 Graph showing the initial resistance of the two electrodes of the flexible bio-memristor prepared in Example 2;

[0054] Figure 9 This is a graph showing the tensile stability of the AgNWs electrode and CNT electrode of the flexible bio-memristor prepared in Example 2;

[0055] Figure 10 This is a graph showing 30 CV cycles of the flexible bio-memristor prepared in Example 2;

[0056] Figure 11 This is a graph showing the tensile stability of the flexible bio-memristor prepared in Example 2;

[0057] Figure 12 The CV graph of the memristor prepared using a CNT solution with a concentration of 0.8 mg / mL;

[0058] Figure 13 The CV graph of the memristor prepared using a CNT solution with a concentration of 0.1 mg / mL;

[0059] Figure 14 CV graph of the memristor made with 1.5 mg / mL AgNWs solution;

[0060] Figure 15 CV graph of the memristor made with 0.5 mg / mL AgNWs solution;

[0061] Figure 16 The CV graph of the memristor prepared using a 20 mg / mL Silk solution;

[0062] Figure 17 CV graph of a memristor fabricated using a 10 mg / mL Silk solution;

[0063] Figure 18 This is a physical photo of the flexible bio-memristor prepared in Example 2. DETAILED DESCRIPTION

[0064] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0065] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods. Unless otherwise specified, the methods used in the examples of the present invention are methods known to those skilled in the art. Unless otherwise specified, the operations are carried out at room temperature.

[0066] Curing agent, model Sylgard 184, brand SYLGARD™, purchased from Merck;

[0067] Carbon nanotubes, code number XFS16-1, were purchased from Xianfeng Nanotechnology;

[0068] Silk protein, model LL-STDB, was purchased from Blue Power Biotechnology (Xi'an) Co., Ltd.;

[0069] Plasma treatment equipment, model CPC-E, manufactured by Safe Instrument Chengde Co., Ltd.

[0070] Ultrasonic cleaner, model SK3310HP, manufacturer Shanghai Kedao Ultrasonic Co., Ltd.

[0071] Example 1

[0072] Preparation of silver nanowires (AgNWs)

[0073] (1) Add 0.16 g of polyvinyl pyrrolidone (360,000 kDa, K90) to 25 mL of ethylene glycol, vortex disperse, and then sonicate for 5 h to obtain a uniformly dispersed polyvinyl pyrrolidone solution;

[0074] (2) Using ethylene glycol as the solvent, prepare 2.5 mL of a 5 mM ferric chloride solution, then add 0.68 g of silver nitrate to it and stir in the dark for 15 min until the silver nitrate is completely dissolved to obtain a bimetallic solution;

[0075] (3) The polyvinyl pyrrolidone solution and the bimetallic solution were added to a flask and reacted at 130°C for 4 h. The flask was then placed in a centrifuge tube and centrifuged at 5000 rpm for 10 min to obtain a precipitate. 10 mL of ethanol was added to the precipitate, and the precipitate was centrifuged at 5000 rpm for 10 min and filtered. The above steps were repeated twice to obtain silver nanowires. The average length of the silver nanowires was measured to be 20 μm and the average diameter was 70 nm.

[0076] Example 2

[0077] Preparation of flexible bio-memristor based on AgNWs / Silk / CNT

[0078] See the process Figure 3 :

[0079] S1. Preparation of top / bottom electrode layers

[0080] S11. Take two circular polyethersulfone (PES) membranes with a diameter of 5 cm and a pore size of 0.45 μm. Use laser printing technology to print graphite powder onto the non-electrode areas of each PES membrane. (Print on one side, with the empty electrode area located in the middle of the membrane.) The shape is rectangular, 2 cm long and 1 mm wide.

[0081] S12. The silver nanowires prepared in Example 1 were added to ethanol and ultrasonically treated for 30 min to prepare a 1 mg / mL AgNWs solution. 2 mg of carbon nanotubes (CNTs) and 70 mg of sodium dodecyl sulfate (SDS) were added to 10 mL of ultrapure water and ultrasonically treated for 2 h to obtain a 0.2 mg / mL CNT solution. 200 μL of the CNT solution was vacuum filtered onto the electrode area of ​​one of the polyethersulfone filter membranes (the solution was first dripped onto the electrode area during filtration). Add to the electrode area, wait until the solution is evenly distributed before opening the vacuum filtration device to ensure that the extracted electrode surface is evenly distributed). Take 1 mL of AgNWs solution and filter the AgNWs into the electrode area of ​​another polyethersulfone filter membrane in the same way as above (filter in five times, 200 μL each time. After each filtration, take 1 mL of ethanol and drop it on the electrode surface to dissolve the PVP remaining inside the electrode and improve the electrode conductivity). Finally, place the two filtered polyethersulfone filter membranes in an oven and dry at 65°C for 30 minutes.

[0082] S13. Dimethylsiloxane monomer and curing agent were mixed in a mass ratio of 10:1, stirred for 20 minutes until no obvious bubbles were present, and then spin-coated onto a silicon wafer (spin-coating volume 5 mL, silicon wafer diameter 10 cm) using a spin coater and cured at 65°C for 20 minutes to form a semi-cured polydimethylsiloxane (PDMS) film. Two dried polyethersulfone filter membranes were attached to the two semi-cured polydimethylsiloxane films, respectively, and placed in an oven and dried at 65°C for 6 hours to completely cure the films. Finally, the silicon wafer, the first filter membrane, and the second filter membrane were peeled off to obtain a top electrode layer containing a top electrode (CNT electrode) and a bottom electrode layer containing a bottom electrode (AgNWs electrode).

[0083] S2. Preparation of intermediate functional layer

[0084] S21. The bottom electrode layer is placed in a plasma treatment device, oxygen is introduced, and the treatment is performed at a discharge power of 60W for 60s to improve the hydrophilicity;

[0085] S22. Dissolve 13.5 mg of silk protein (Silk) powder in 1 mL of deionized water to obtain a 13.5 mg / mL Silk solution. Place the treated bottom electrode layer on a gel coater and drop 20 μL of the Silk solution onto the electrode surface (specifically, the middle of the AgNWs electrode, with a coating area greater than 1 mm).2 ), spin coating at 500 rpm for 60 s, thereby forming an intermediate functional layer (i.e., Silk functional layer);

[0086] S3. Assembly of Memristor

[0087] 5 μL of PDMS solution (obtained by mixing dimethylsiloxane monomer and curing agent in a mass ratio of 10:1) was coated on the non-electrode area of ​​the electrode surfaces of the top electrode layer and the bottom electrode layer. Then, the electrode surfaces of the top electrode layer and the bottom electrode layer were attached to each other (the CNT electrode and the AgNWs electrode were cross-shaped). Finally, they were placed in an oven and cured at 65°C for 30 minutes to obtain a flexible bio-memristor based on AgNWs / Silk / CNT.

[0088] Experimental Example 1

[0089] Performance testing of flexible bio-memristors

[0090] The flexible bio-memristor prepared in Example 2 was analyzed for current-voltage (IV) characteristics, repeatability, and stretchability. The results are as follows:

[0091] As the fourth basic circuit element, memristor has a "memory mechanism" that can achieve "memory" of a certain electrical characteristic, such as resistance, through a specific device structure. Figure 1 The figure shows the structure diagram of the flexible bio-memristor of the present invention, and the actual photo is shown in FIG. Figure 18 As shown in the figure, it is a three-dimensional structure composed of CNT electrodes, Silk functional layer and AgNWs electrodes. By applying a positive voltage to the electrodes at both ends of the memristor, Silk induces the oxidation of silver ions into silver atoms, resulting in the formation of a conductive path between the two electrodes, and the resistance of the memristor switches from a high resistance state to a low resistance state. Similarly, as a device with a "memory" effect, the memristor also has the ability to switch from a low resistance state to a high resistance state. Under negative voltage bombardment, the conductive path is broken and the memristor returns to a high resistance state (such as Figure 2 shown).

[0092] The flexible bio-memristor of the present invention has a typical current-voltage (IV) characteristic curve and also has good repeatability and stretchability.

[0093] Figure 4Scanning electron microscope images of the AgNWs electrode (left) and CNT electrode (right) formed in Example 2. The AgNWs electrode's SEM image shows that a large number of AgNWs were successfully embedded within the PDMS film via pre-cured transfer, ensuring high conductivity even in a stretched state. The CNT electrode's SEM image reveals a certain amount of stacking between the carbon nanotubes. When the electrode is stretched, these carbon nanotubes slip relative to each other without breaking, maintaining the electrode's conductivity and providing a foundation for the stable operation of the core memristive functional layer.

[0094] To verify the core electrical performance of the constructed flexible bio-memristor, its typical current-voltage (IV) characteristic curve was tested. First, a constant voltage of 0.01V was applied to the two ends of the memristor to test its resistance. It was found that the initial state of the memristor was high resistance, and the resistance remained stable at about 10 within 1000s. 6 Ω, which is consistent with the situation that the initial resistance of the memristor is high resistance (such as Figure 5 ). Then, as Figure 6 As shown in the figure, by applying a 0-1.5-0V linear voltage sweep to both ends of the memristor, when the current limit is 10μA, the memristor is in a volatile state. When the voltage is 0.9V, the current suddenly increases and the memristor switches to a low-resistance state. When the voltage returns to 0V, the memristor spontaneously returns to its initial state, that is, a high-resistance state. When the current limit is 1mA, the memristor is in a non-volatile state. By applying a 0-1.5-0V linear voltage sweep, it can be found that the current of the memristor suddenly increases to 1mA at around 0.7V, and then as the voltage decreases, the memristor remains in a low-resistance state. When a 0-1.5-0V linear voltage sweep is applied in the negative voltage range, the bombardment of the negative voltage causes the memristor to return from a low-resistance state to a high-resistance state and remain stable. It has been tested that it can still maintain a stable resistance state within 1000s, and the high-resistance resistance is about 10 7 Ω, low resistance is about 10 3 Ω (such as Figure 7 ). Figure 6 The results of 7 confirm that the constructed flexible bio-memristor has controllable volatile and non-volatile switching characteristics, a significant high-low resistance state ratio and good state retention ability, showing its basic potential as a core storage / computing unit. In addition, the resistance of the CNT electrode is about 70Ω, and the resistance of the AgNWs electrode is about 50Ω (e.g. Figure 8 ).

[0095] For electrochemical sensor-memristor integrated systems for flexible wearable or bio-integrated applications, the long-term stability of the device under repeated operation and mechanical tensile deformation is crucial. In order to comprehensively evaluate the reliability of flexible bio-memristors in practical application scenarios, we further systematically tested their electrical cycle repeatability and performance stability under different tensile strains. The results are as follows: Figure 9 As shown. The flexible bio-memristor constructed by the present invention achieves excellent tensile stability and electrical reliability through innovative electrode and structural design. Figure 4 and Figure 9 As shown in the figure, the AgNWs electrode is deeply embedded in the PDMS film using a semi-cured transfer process, and maintains more than 90% of its initial conductivity under 50% tensile strain (the current drops from 0.20µA to 0.17µA). The CNT electrode disperses stress through the relative slip mechanism of the carbon nanotube stack, and the conductivity retention rate exceeds 75% under the same conditions (the current drops from 0.14µA to 0.09µA). The stability of the electrode effectively ensures the overall robustness of the device. Figure 10 As shown in the figure, even under 50% strain, the current-voltage (IV) curve of the AgNWs and CNT electrodes still maintains linear ohmic contact characteristics, and the electrode-memristive functional layer interface does not fail under deformation. Crucially, the core memristive functional characteristics of the device are effectively maintained under tension ( Figure 11 ).

[0096] Experimental Example 2

[0097] Effects of CNT solution concentration, AgNWs solution concentration, and Silk solution concentration on the performance of flexible bio-memristors

[0098] Based on Example 2, single factor influence experiments were conducted on the concentrations of the CNT solution and the AgNWs solution in step S12, and the concentration of the Silk solution in step S22. The results showed that:

[0099] During vacuum filtration, excessively high concentrations of CNT solution will cause agglomeration in the dispersion, affecting the subsequent printing effect and the conductive properties of the electrode. Figure 12 As shown in the figure, the memristor prepared in a 0.8mg / mL CNT solution has an excessively high CNT concentration, which leads to excessive enhancement of the conductivity of the composite film, forming a low-resistance bypass, thereby inhibiting or destroying the core resistance switching mechanism on which the memristor relies, causing the memristor to lose its resistance mutation or memory function. On the other hand, a too low concentration makes the CNT distribution on the electrode too sparse, which is also not conducive to improving the conductivity of the CNT electrode. Figure 13As shown in the figure, at a CNT concentration of 0.1 mg / mL, the memristor exhibits poor resistance stability in the low voltage range (within 1 V) and struggles to maintain a stable low resistance state at high voltages. Experimental verification shows that a concentration of 0.2 mg / mL ensures both adequate CNT dispersion and the formation of a uniform, dense conductive layer on the electrode, effectively improving sensor sensitivity.

[0100] During vacuum filtration, the concentration of the AgNWs solution is also crucial. Too high a concentration of AgNWs will make it difficult to disperse evenly in the solution, which will affect the electrode uniformity during filtration. Since AgNWs itself has good conductivity, its concentration will inevitably affect the conductivity of the electrode. Figure 14 As shown in the figure, using a 1.5mg / mL AgNWs solution will produce too high a conductivity, causing the memristor to be directly in a low-resistance state without a resistance switching mechanism. However, too low an AgNWs concentration, such as 0.5mg / mL, will not form an effective conductive network and provide sufficient Ag⁺ ion sources, causing the memristor to lose its switching characteristics, such as Figure 15 As shown in the figure, there is no resistive switching characteristic in the positive and negative voltage ranges. Experimental verification shows that the AgNWs solution with a concentration of 1 mg / mL has the best effect.

[0101] In addition, during the preparation of the intermediate functional layer, the concentration of the Silk solution will also affect the performance of the memristor, such as Figure 16 As shown in Figure 1, a Silk solution with too high a concentration, such as 20 mg / mL, will make it difficult for the memristor to be reset to a high-resistance state when a negative voltage is scanned, making it impossible for the memristor to effectively switch between high and low resistance states. Similarly, a Silk solution with too low a concentration, such as 10 mg / mL, will affect the thickness of the intermediate functional layer, making it easier for the CNT electrode and the AgNWs electrode to contact, thus making the initial resistance of the memristor low resistance. Figure 17 As shown, the memristor maintains its initial low-resistance state, exhibiting no resistance switching characteristics. Experimental verification shows that at a concentration of 13.5 mg / mL, the memristor maintains both an initial high-resistance state and a transition from low-resistance to high-resistance within a given negative voltage range (0-6 V), ensuring the memristor exhibits excellent resistance switching characteristics.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. 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 method for preparing a flexible bio-memristor, characterized in that: The following steps are involved: S1. Preparation of top / bottom electrode layers: S11. Blocking the non-electrode areas of the first and second filter membranes; S12. The top electrode material solution is filtered by vacuum filtration to the electrode region of the first filter membrane, and the bottom electrode material solution is filtered by vacuum filtration to the electrode region of the second filter membrane; S13. Transferring the top electrode material on the first filter membrane to the first substrate film to obtain a top electrode layer containing a top electrode, and transferring the bottom electrode material on the second filter membrane to the second substrate film to obtain a bottom electrode layer containing a bottom electrode; The transfer operation steps include: mixing the raw material monomer of the first substrate film or the second substrate film with a curing agent, applying the mixture onto a substrate to form a semi-cured substrate film, drying the first filter membrane or the second filter membrane and attaching the mixture onto the semi-cured substrate film, drying the mixture until the film is completely cured, and finally peeling off the substrate and the first filter membrane or the second filter membrane; S2. Preparation of intermediate functional layer: Coating a functional material on the surface of the bottom electrode layer where the electrode is located and laminating the bottom electrode thereon, or coating a functional material on the surface of the top electrode layer where the electrode is located and laminating the top electrode thereon, to form an intermediate functional layer; S3. Assembly of memristor: The top electrode layer and the bottom electrode layer are pasted together with the surfaces where the electrodes are located facing each other, and the intermediate functional layer is pasted to the top electrode on the top electrode layer and the bottom electrode on the bottom electrode layer.

2. The method for preparing a flexible bio-memristor according to claim 1, wherein: In step S11, the first filter membrane and the second filter membrane are both polyethersulfone filter membranes, and the sealing is performed by printing graphite powder.

3. The method for preparing a flexible bio-memristor according to claim 1 or 2, wherein: In step S12, the top electrode material is carbon nanotubes, and the carbon nanotube solution is prepared by dispersing carbon nanotubes and sodium dodecyl sulfate in water, with a concentration of 0.2 mg / mL; the bottom electrode material is silver nanowires with an average length of 20 μm and an average diameter of 70 nm, and the silver nanowire solution is prepared by dispersing silver nanowires in ethanol, with a concentration of 1 mg / mL.

4. The method for preparing a flexible bio-memristor according to claim 3, wherein: The preparation steps of silver nanowires include: (1) uniformly dispersing polyvinyl pyrrolidone in ethylene glycol to obtain a polyvinyl pyrrolidone solution; (2) Dissolve ferric chloride in ethylene glycol, add silver nitrate, and stir to dissolve in the dark to obtain a bimetallic solution; (3) The polyvinyl pyrrolidone solution and the bimetallic solution were mixed and reacted at 130°C for 4 hours, followed by centrifugation to obtain a precipitate, which was then centrifuged and washed with ethanol.

5. The method for preparing a flexible bio-memristor according to claim 1 or 2, wherein: In step S13 , both the first substrate film and the second substrate film are polydimethylsiloxane films.

6. The method for preparing a flexible bio-memristor according to claim 1 or 2, wherein: In step S2, the functional material is silk protein.

7. The method for preparing a flexible bio-memristor according to claim 1 or 2, wherein: The operation steps of step S2 include: S21. Plasma treatment of the top electrode layer or the bottom electrode layer; S22. Spin-coat the functional material solution onto the processed top electrode layer or bottom electrode layer.

8. The method for preparing a flexible bio-memristor according to claim 1 or 2, wherein: The operation steps of step S3 include: coating a mixture of raw material monomers of the first substrate film or the second substrate film and a curing agent on the non-electrode area of ​​the surface where the electrodes of the top electrode layer and / or the bottom electrode layer are located, then sticking the surfaces where the electrodes of the top electrode layer and the bottom electrode layer are located together, and finally drying and curing.

9. A flexible bio-memristor, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 8.

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