Artificial synaptic biochemical sensor based on liquid-solid contact electrification effect

Abstract

The invention provides an artificial synaptic biochemical sensor based on a liquid-solid contact electrification effect, which is composed of a support layer, a sensitive layer, a functional layer and a top electrode layer which are sequentially superposed from bottom to top, the support layer and the sensitive layer form a power generation area, and the functional layer and the top electrode layer form a synaptic area. According to the invention, the principle of liquid-solid electrification effect is utilized, sensitive charges are generated and transmitted to the synaptic region, and the short-time plasticity of the artificial synaptic device in the synaptic region is utilized, so that the detection and memory of an object to be detected are realized, and the defect of instantaneity of a response result of liquid-solid contact electrification is overcome.

Description

Technical Field

[0001] The present invention relates to the technical fields of liquid-solid contact, artificial synapses, and sensors, and in particular, to an artificial synapse-type biochemical sensor based on the liquid-solid contact electrification effect. Background Art

[0002] (I) Introduction to the Liquid-Solid Contact Electrification Effect

[0003] The liquid-solid contact electrification effect is a case of the traditional contact electrification effect. As is well known, in the traditional contact electrification phenomenon, when two different solid materials come into contact, separate, and rub against each other, due to the difference in the relative polarities of the two materials, the electron clouds overlap when they come into contact, causing their surfaces to carry equal amounts of opposite charges. The most classic example is that a glass rod rubbed with silk carries a positive charge. If a series of external components such as electrodes are paired at this time, an alternating current can be generated during the repeated contact-separation process. The liquid-solid contact electrification breaks through the material limitations in the traditional solid-solid contact friction electrification, utilizes the natural and abundant water resources in nature, comes into contact with solid materials to make the solid surface carry charges, and an alternating current can be generated under the cyclic contact-separation of the liquid. The double-layer model in the liquid-solid contact electrification effect was explained in "Quantifying electron-transfer in liquid-solid contact electrification and the formation of electric double-layer" published in Nature Communications in 2020, and a simple structure of a liquid-solid contact electrification test device was proposed based on this principle. The results show that its electrical output performance is good. Currently, the liquid-solid contact electrification effect is mainly applied to the fields of energy harvesting and sensors, as illustrated below:

[0004] "Flexible triboelectric generator" in Volume 1, Issue 2 of Nano Energy proposed a triboelectric nanogenerator with superhydrophobic and self-cleaning functions based on the principle of liquid-solid contact electrification and using a single-electrode mode structure. When water droplets flow through a pipeline and polytetrafluoroethylene (PTFE), the triboelectric nanogenerator is relied on to obtain the energy generated by the friction between the water droplets and the solid. Due to its characteristics of easy manufacturing, low cost, high efficiency, and strong durability, the developed triboelectric nanogenerator extends potential applications to collecting energy from domestic wastewater and raindrops.

[0005] "Quantifying electron-transfer in liquid-solid contact electrification and the formation of electric double-layer" in Nature Communications, Volume 11, proposed a self-powered water temperature sensor. By using microfibers, a self-healing, waterproof, and adjustable triboelectric nanogenerator was fabricated, which has excellent superhydrophobicity. Its self-healing ability under heating ensures stable triboelectric performance and a long service life, thus enabling the collection of energy from cold and hot water.

[0006] "Self-Powered Distributed Water Level Sensors Based on Liquid–Solid Triboelectric Nanogenerators for Ship Draft Detecting" in Advanced Functional Materials, Volume 29, Issue 41, proposed a self-powered water level sensor based on liquid-solid triboelectric nanogenerators. Its water level measurement accuracy is ten times that of the measurement devices used in conventional ships. Due to its accuracy and real-time performance, it is expected to be applied to the real-time water level monitoring system of ships.

[0007] "A droplet-based electricity generator with high instantaneous power density" in Nature, Volume 578, proposed a droplet triboelectric nanogenerator with high instantaneous performance, which adopts a switch structure design. Due to the continuous contact between water droplets and PTFE, charges continuously accumulate on the solid, resulting in a high electrical energy output in an instant at the end. It has been experimentally demonstrated that the generated electrical energy can simultaneously light up 100 light-emitting diodes.

[0008] In "Energy Conversion Analysis of Multilayered Triboelectric Nanogenerators for Synergistic Rain and Solar Energy Harvesting" in Advanced Materials, Volume 34, Issue 28, based on the original droplet triboelectric nanogenerator, a new multi-layer collection structure was proposed, which can achieve continuous collection of droplets and convert the kinetic energy generated when droplets fall, realizing high-efficiency collection and energy conversion of droplets.

[0009] "Self-Powered Ion Concentration Sensor with Triboelectricity from Liquid–Solid Contact Electrification" in Volume 2, Issue 5 of *Advanced Electronic Materials* proposed a triboelectric self-powered ion concentration sensor (TSICS) that generates electrical signals through friction between a liquid and a PDMS microfluidic channel without an external power source. Experiments showed that its output signal decreases as the NaCl concentration increases, and its sensitivity is comparable to that of commercial NaCl sensors. Its narrow-channel design reduces liquid residue and improves stability. The sensor has a simple structure, can be integrated into a microfluidic system, and is suitable for chip-based self-powered detection.

[0010] However, the voltage generated by liquid–solid contact electrification only lasts for a very short moment, and then the voltage signal immediately disappears. Due to its transient limitation, this causes great trouble for the generation and detection of sensitive signals. In practical applications, the response of sensitive signals only lasts for a moment, far from meeting the basic performance requirements for biochemical sensor detection, which poses a great challenge to the application of biochemical sensors.

[0011] (II) Introduction to Artificial Synapse-Type Biochemical Sensors

[0012] An artificial synapse is a neuromorphic device that can directly simulate the behaviors of synapses and neurons at the physical level relying on unique mechanisms. Due to the bottleneck of energy efficiency and the leveling off of Moore's Law, the efficiency of traditional von Neumann-based computer systems has approached its limit, and the development demand for new hardware has been put on the agenda. As a bionic device, an artificial synapse can simulate biological neurons and synapses and implement the architecture and working mechanism of biological synapses, which is the key to realizing high-efficiency neural networks at present.

[0013] Currently, artificial synapse devices based on transistors and memristors have both been successfully used to simulate the synaptic characteristics of organisms and achieved bionic functions such as neural computing, vision, and touch. The channel conductivity of transistor devices can be controlled through mechanisms such as electrostatic attraction, electrochemical doping, and charge capture by defects, thereby simulating properties such as short-term plasticity and long-term plasticity of biological synapses.

[0014] Short-term plasticity of artificial synapses refers to the adjustable changes that occur in artificial synapses (i.e., the connections between artificial neurons) in a neural network within a short period due to changes in the frequency and intensity of input signals. This plasticity mimics the behavior of synapses in biological nervous systems, enabling artificial neural networks to enhance or weaken signal transmission by adjusting connection weights, thereby improving the network's learning ability and adaptability. This process is crucial for the dynamic learning and information storage of neural networks. Currently, researchers are continuously delving into the field of artificial synapses and making progress in the materials and properties of synapses.

[0015] In the article "Ferroelectric FET analog synapse for acceleration of deep neural network training" published in IEDM in 2017, a ferroelectric field-effect transistor (FET) fabricated using hafnium zirconium oxide (HZO) was used to simulate synapses, enabling the accelerated training of deep neural networks. HZO was deposited on a silicon substrate and annealed to form multiple ferroelectric domains. The threshold voltage was gradually adjusted using the multi-domain polarization switching of HZO, and its drain-source conductance was reduced by applying short voltage pulses to the gate.

[0016] Journal of Applied Physics, Volume 119, Issue 24, "A light-stimulated synaptic transistor with synaptic plasticity and memory functions based on InGaZnO x –Al2O3 thin film structure", the article discloses a synaptic transistor based on an indium gallium zinc oxide-aluminum oxide thin film structure. Before and after stimulation, a significant increase in the synaptic current of the device was observed, meeting synaptic plasticity. In addition, it also exhibited memory behaviors of the brain, including the transition from short-term memory to long-term memory and memory characteristics similar to the Ebbinghaus forgetting curve.

[0017] The article "Synergistic Gating of Electro-Iono-Photoactive 2D Chalcogenide Neuristors: Coexistence of Hebbian and Homeostatic Synaptic Metaplasticity" in Volume 30, Issue 25 of Advanced Materials discloses a three-terminal device prepared based on molybdenum disulfide (MoS2). This device can be controlled by two external stimuli: electrical stimulation and optical stimulation. Electrical stimulation is used to stimulate short-term synaptic plasticity, and optical stimulation is used to stimulate long-term synaptic plasticity. If both electrical stimulation and optical stimulation are used simultaneously, the classical conditioning function can be achieved. Tan et al. used tungsten trioxide (WO3) thin film as the resistive switching layer and inert metal platinum (Pt) as the electrode to prepare a memristor that not only successfully simulated the basic properties of biological synapses but also realized the reprogramming behavior of biological synapses. The discovery of this behavior helps to construct brain-like learning behaviors.

[0018] In the article "Artificial Synapses with Short-and Long-Term Memory for Spiking Neural Networks Based on Renewable Materials" published in ACS Nano in August 2017, a novel flexible memristor was prepared using withered leaves, silver, titanium, and polyethylene terephthalate (PET) as raw materials.

[0019] The article published in ACS Applied Materials & Interfaces in December 2020

[0020] "Harvesting Electricity from Water Evaporation through Microchannels of Natural Wood" combined tungsten (W), egg white film, and indium tin oxide (ITO) on a polyethylene terephthalate (PET) substrate to prepare a memristor with innovative morphology. There are various mineral ions, sodium salts, potassium salts, etc. in egg white itself. Since the diffusivity of metal tungsten itself is weak, the reduction of metal ions in the egg white film to form conductive filaments determines the resistive switching properties of the device. By regulating the pulse stimulation, the transformation from synaptic excitation to synaptic inhibition can be achieved.

[0021] "A Hippocampus-Inspired Dual-Gated Organic Artificial Synapse for Simultaneous Sensing of a Neurotransmitter and Light" in Volume 33, Issue 17 of Advanced Materials discloses a dual-gated organic artificial synapse that mimics the synaptic function of the hippocampus and can detect dopamine and light simultaneously. By combining chemical and optical sensors, the developed system can enhance memory consolidation function, providing new opportunities for the development of low-power, multi-functional artificial neural synapses and human-machine interfaces.

[0022] The article "Photoelectroactive Artificial Synapse and its Application to Biosignal Pattern Recognition" published in npj 2D Materials and Applications in 2021 discloses a photoelectroactive artificial synapse based on the MoS2 / h-BN heterojunction. Bidirectional update of synaptic weights is achieved through the co-stimulation of light pulses and electrical pulses, with high dynamic range and long retention characteristics. It can be used for electrocardiogram pattern recognition with an accuracy of 96.1%. It demonstrates excellent brain-like neural network performance and provides a new method for efficient biosignal pattern recognition.

[0023] The present invention innovatively couples the liquid-solid contact electrification with the characteristics of artificial synapses. The liquid-solid interface and the artificial synapse serve as the sensitive layer and the functional layer respectively, functionalizing the artificial synapse and preparing a novel biochemical sensor.

[0024] The primary technical problem to be solved by the present invention is: the defect of the instantaneous response result of liquid-solid contact electrification. Summary of the Invention

[0025] The object of the present invention is to design a principle using the liquid-solid electrification effect to generate sensitive charge transfer to the synaptic region, and utilize the short-term plasticity of the artificial synaptic device in the synaptic region to achieve the detection and memory of the analyte, solving the defect of the instantaneous response result of liquid-solid contact electrification.

[0026] To achieve the above object, the present invention provides the following technical solutions:

[0027] An artificial synaptic biochemical sensor based on the liquid-solid contact electrification effect, which is composed of a support layer, a sensitive layer, a functional layer, and a top electrode layer stacked in sequence from bottom to top. Among them, the support layer and the sensitive layer constitute the power generation region, and the functional layer and the top electrode layer constitute the synaptic region.

[0028] Further, the functional layer is composed of multiple coaxial cable-type artificial synapses tiled and stacked on the upper surface of the sensitive layer, and adjacent two coaxial cable-type artificial synapses are parallel and spaced apart from each other; the top electrode layer is composed of multiple platinum metal strips tiled and stacked on the upper surface of the functional layer, adjacent two platinum metal strips are parallel and spaced apart from each other, and each platinum metal strip of the top electrode layer is vertically stacked on all the coaxial cable-type artificial synapses of the functional layer.

[0029] Further, the power generation area is prepared by the following method:

[0030] S11. Attach a polymer thin film to a silicon wafer to form a support layer embryo;

[0031] S12. Dissolve zinc nitrate hexahydrate in a beaker with deionized water, slowly dropwise add ammonia water drop by drop while stirring to form a first mixed solution, and then immerse the support layer embryo in the first mixed solution; place the beaker containing the support layer embryo and the first mixed solution in an oven for drying;

[0032] S13. Take out after drying is completed to obtain a support layer and a sensitive layer embryo formed by a ZnO nanowire array thereon;

[0033] S14. Use a dropper to evenly drip the enzyme solution on the polymer thin film to which the ZnO nanowire array adheres, and naturally air dry at room temperature to adsorb the enzyme on the ZnO nanowire array, obtaining an enzyme-modified ZnO nanowire array, that is, a sensitive layer.

[0034] Further, the polymer thin film in S11 is a polydimethylsiloxane thin film.

[0035] Further, the drying process in S12 is to maintain in a constant temperature environment of 80 °C for 24 h.

[0036] Further, the coaxial cable-type artificial synapses in the synaptic area are prepared by the following method:

[0037] S21. Prepare a 0.2 mm flexible PLA fiber as the inner core of the coaxial cable-type artificial synapse;

[0038] S22. Dip-coat the conductive silver paste on the PLA fiber by dip-coating method and dry for 2 h to obtain a PLA / Ag fiber;

[0039] S23. Immerse the PLA / Ag fiber and the Pt electrode in the MXene nanosheet solution, and obtain a PLA / Ag / MXene fiber by electrophoresis deposition method, that is, the required coaxial cable-type artificial synapse.

[0040] Further, the MXene nanosheet solution is prepared by the following method:

[0041] S31. Mix HF, HCl, and Ti3AlC2 powders, add deionized water, and purge with nitrogen to create an inert environment and avoid subsequent oxidation reactions.

[0042] S32. React in a silicone oil bath at 40 °C for 24 h to obtain a MXene precursor reaction solution with a multi-layer structure.

[0043] S33. Add deionized water to the MXene precursor reaction solution, centrifuge at 4000 rpm for 5 minutes to remove impurities.

[0044] S34. After repeating the centrifugation and washing in S33 five times, dry the obtained solution for 24 h to obtain multi-layer MXene nanosheets.

[0045] S35. Add deionized water to the MXene nanosheets obtained in S34, ultrasonically treat the mixture to exfoliate the multi-layer MXene into uniform few-layer MXene nanosheets.

[0046] S36. Centrifuge at 4000 rpm for 10 minutes, collect the supernatant to obtain a uniformly dispersed few-layer MXene nanosheet solution.

[0047] Furthermore, in S21, a 0.2-mm flexible PLA fiber is prepared by a 3D printer.

[0048] The present invention utilizes the principle of the liquid-solid triboelectrification effect to generate sensitive charges and transfer them to the synaptic region. By using the short-term plasticity of the artificial synaptic device in the synaptic region, the detection and memory of the analyte are realized, solving the defect of the instantaneous response result of liquid-solid contact electrification. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.

[0050] Figure 1 It is a three-dimensional structure diagram of the present invention.

[0051] Figure 2 It is a front view of the structure of the present invention.

[0052] Figure 3 It is a top view of the structure of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0053] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0054] As shown in the figure, the structure of an artificial synaptic sensor device based on the liquid-solid contact electrification effect of the present invention is composed of a support layer 1, a sensitive layer 2, a functional layer 3, and a top electrode layer 4 stacked in sequence from bottom to top. Among them, the support layer 1 and the sensitive layer 2 constitute the power generation area, and the functional layer 3 and the top electrode layer 4 constitute the synaptic area.

[0055] Preferably, the functional layer 3 is composed of multiple coaxial cable-type artificial synapses laid flat and stacked on the upper surface of the sensitive layer 2, and adjacent two coaxial cable-type artificial synapses are parallel and spaced apart from each other; the top electrode layer 4 is composed of multiple platinum metal strips laid flat and stacked on the upper surface of the functional layer 3, and adjacent two platinum metal strips are parallel and spaced apart from each other. Each platinum metal strip of the top electrode layer 4 is vertically stacked on all the coaxial cable-type artificial synapses of the functional layer 3. This structure can simulate the plasticity of artificial synapses, and due to its flexible characteristics, this structure is easy to merge with the bottom power generation area.

[0056] The power generation area of the present invention is prepared by the following method:

[0057] S11. Attach a PDMS (polymer: polydimethylsiloxane) film to a silicon wafer to form a support layer embryo.

[0058] S12. Dissolve zinc nitrate hexahydrate (Zn(NO3)2·6H2O) in a beaker with deionized water, and slowly drop ammonia water (NH3·H2O) drop by drop while stirring to form a first mixed solution. Then immerse the support layer embryo in the first mixed solution; place the beaker containing the support layer embryo and the first mixed solution in an oven for drying, and the drying process is to maintain at a constant temperature of 80°C for 24 h.

[0059] S13. Take it out after drying to obtain the support layer and the sensitive layer embryo formed by the ZnO nanowire array on it.

[0060] S14. Use a dropper to evenly drip the enzyme solution on the PDMS film attached to the ZnO nanowire array, and let it air dry at room temperature to make the enzyme adsorbed on the ZnO nanowire array, obtaining the enzyme-modified ZnO nanowire array, that is, the sensitive layer. The present invention modifies and modifies the ZnO nanowire array with the corresponding enzyme to achieve selectivity for the analyte.

[0061] Furthermore, the coaxial cable-type artificial synapses in the synaptic area are prepared by the following method:

[0062] S21. Prepare a 0.2 mm flexible PLA (polylactic acid) fiber through a 3D printer as the inner core of the coaxial cable-type artificial synapse.

[0063] S22. Dip-coat the conductive silver paste on the PLA fiber through the dip-coating method and dry for 2 h to obtain the PLA / Ag fiber.

[0064] S23. Immerse the PLA / Ag fiber and the Pt electrode into the MXene nanosheet solution, and obtain the PLA / Ag / MXene fiber, i.e., the required coaxial cable-type artificial synapse, through electrophoretic deposition method.

[0065] Further, the MXene (two-dimensional transition metal carbides, nitrides and carbonitrides) nanosheet solution is prepared by the following method:

[0066] S31. Mix HF, HCL and Ti3AlC2 powder, add deionized water and purge with nitrogen to create an inert environment and avoid subsequent oxidation reactions.

[0067] S32. React in a silicone oil bath at 40 °C for 24 h to obtain a multi-layered MXene precursor reaction solution.

[0068] S33. Add deionized water to the MXene precursor reaction solution, centrifuge at 4000 rpm for 5 minutes to remove impurities.

[0069] S34. After repeating the centrifugal washing in S33 for 5 times, dry the obtained solution for 24 h to obtain multi-layer MXene nanosheets.

[0070] S35. Add deionized water to the MXene nanosheets obtained in S34, ultrasonically treat the mixture to exfoliate the multi-layer MXene into uniform few-layer MXene nanosheets.

[0071] S36. Centrifuge at 4000 rpm for 10 minutes, collect the supernatant to obtain a uniformly dispersed few-layer MXene nanosheet solution.

[0072] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An artificial synaptic biochemical sensor based on the liquid-solid contact electrification effect, characterized in that, It is composed of a support layer (1), a sensitive layer (2), a functional layer (3), and a top electrode layer (4) stacked successively from bottom to top. Among them, the support layer and the sensitive layer constitute the power generation area, and the functional layer and the top electrode layer constitute the synaptic area.

2. The artificial synaptic biochemical sensor based on the liquid-solid contact electrification effect according to claim 1, wherein The functional layer is composed of multiple coaxial cable-type artificial synapses tiled and stacked on the upper surface of the sensitive layer, and adjacent two coaxial cable-type artificial synapses are parallel and spaced from each other; the top electrode layer is composed of multiple platinum metal strips tiled and stacked on the upper surface of the functional layer, and adjacent two platinum metal strips are parallel and spaced from each other. Each platinum metal strip of the top electrode layer is vertically stacked on all the coaxial cable-type artificial synapses of the functional layer.

3. The artificial synaptic biochemical sensor based on the liquid-solid contact electrification effect according to claim 1, characterized in that The power generation area is prepared by the following method: S11. Attach a polymer thin film to a silicon wafer to form a support layer embryo. S12. Dissolve zinc nitrate hexahydrate in a beaker with deionized water, slowly dropwise add ammonia water drop by drop while stirring to form a first mixed solution, and then immerse the support layer embryo in the first mixed solution; place the beaker containing the support layer embryo and the first mixed solution in an oven for drying. S13. Take it out after drying is completed to obtain the support layer and the sensitive layer embryo formed by the ZnO nanowire array on it. S14. Use a dropper to evenly drip the enzyme solution on the polymer thin film attached to the ZnO nanowire array, and air-dry it naturally at room temperature to make the enzyme adsorbed on the ZnO nanowire array, obtaining the enzyme-modified ZnO nanowire array, that is, the sensitive layer.

4. The artificial synaptic biochemical sensor based on the liquid-solid contact electrification effect according to claim 3, wherein The polymer thin film in S11 is a polydimethylsiloxane thin film.

5. The artificial synaptic biochemical sensor based on the liquid-solid contact electrification effect according to claim 3, wherein The drying process in S12 is to maintain at a constant temperature of 80 °C for 24 h.

6. The artificial synaptic biochemical sensor based on the liquid-solid contact electrification effect according to claim 2, characterized in that, The coaxial cable-type artificial synapses in the synaptic area are prepared by the following method: S21. Prepare a 0.2 mm flexible PLA fiber as the inner core of the coaxial cable-type artificial synapse. S22. Dip-coat the PLA fiber with conductive silver paste and dry for 2 h to obtain PLA / Ag fiber. S23. Immerse the PLA / Ag fiber and the Pt electrode in the MXene nanosheet solution, and obtain the PLA / Ag / MXene fiber, that is, the required coaxial cable-type artificial synapse, by electrophoretic deposition.

7. The artificial synaptic biochemical sensor based on the liquid-solid contact electrification effect as described in claim 6, wherein The MXene nanosheet solution is prepared by the following method: S31. Mix HF, HCL, and Ti3AlC2 powder, add ionic water and purge with nitrogen to create an inert environment to avoid subsequent oxidation reactions. S32. React in a silicone oil bath at 40 °C for 24 h to obtain a multi-layered MXene precursor reaction solution. S33. Add deionized water to the MXene precursor reaction solution and centrifuge at 4000 rpm for 5 minutes to remove impurities. S34. Repeat the centrifugal washing in S33 5 times, and then dry the obtained solution for 24 h to obtain multi-layer MXene nanosheets. S35. Add deionized water to the MXene nanosheets obtained in S34, and ultrasonically treat the mixed solution to exfoliate the multi-layer MXene into uniform few-layer MXene nanosheets. S36. Centrifuge at 4000 rpm for 10 minutes and collect the supernatant to obtain a uniformly dispersed few-layer MXene nanosheet solution.

8. The artificial synaptic biochemical sensor based on the liquid-solid contact electrification effect according to claim 6, wherein In S21, a 0.2-mm flexible PLA fiber is prepared by a 3D printing mechanism.

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