Organic artificial synaptic transistor pressure sensor based on suspension structure and array, preparation method and application thereof

Abstract

The invention relates to an organic artificial synaptic transistor pressure sensor based on a suspension structure and an array, a preparation method and application thereof, and belongs to the technical field of semiconductor devices and sensing. The pressure sensor is composed of a substrate, source and drain electrodes, a supporting layer and a suspension structure based on an organic semiconductor layer, a dielectric passivation layer, a polyelectrolyte dielectric layer and a flexible grid electrode, and current change is caused through contact change between the organic semiconductor layer and the source and drain electrodes so as to achieve pressure response. The pressure sensor has the advantages of low power consumption, fast response, high sensitivity, wide detection range and the like, and can simulate a biological synapse function to realize a pressure synapse characteristic which is crucial to complex signal processing. In addition, the integrated array of the pressure sensors can be combined with an algorithm to realize high-accuracy touch recognition of braille characters. The results provide a new opportunity for the potential application of the method in bionic electronic skin, touch imaging, electrical equipment monitoring, sensing, storing and computing intelligent terminals and man-machine interaction systems.

Description

Technical Field

[0001] The present invention belongs to the technical fields of semiconductor devices and sensing technologies, and relates to an organic artificial synaptic transistor pressure sensor based on a suspension structure, an array thereof, a preparation method and an application. Background Art

[0002] With the rapid development of artificial intelligence, the Internet of Things and wearable devices, flexible electronic technology is gradually penetrating into frontier fields such as bionic electronic skin, intelligent tactile systems, and human-computer interaction interfaces. As the core component for sensing external mechanical signals, the performance of pressure sensors directly determines the sensitivity, response speed, and functional complexity of tactile systems. There are still many bottlenecks in the design concept, material system, and function realization of traditional pressure sensors, making it difficult to meet the growing intelligent requirements.

[0003] Traditional pressure sensors only detect changes in the magnitude of a single mechanical pressure, making it difficult to meet the application requirements of intelligent tactile systems and human-computer interaction interfaces. In addition, traditional pressure sensors rely on rigid materials (such as glass substrates or silicon-based semiconductors), resulting in poor flexibility of the devices and difficulty in conforming to complex curved surfaces, which limits their application in wearable devices or bionic skins. Under long-term cyclic loading, mechanical fatigue will also cause sensitivity attenuation, further weakening the reliability of pressure sensor devices.

[0004] In organisms, when the skin is stimulated externally, signals are transmitted to the brain through the interconnected network of neurons and synapses, thereby completing signal processing and realizing information memory and storage. Inspired by this, developing pressure sensors with neuromorphic synaptic functions, simulating the information transmission and processing mechanism of the biological nervous system, and endowing the sensors with real-time sensing, dynamic response, and memory storage functions has become a key technology that urgently needs to be broken through.

[0005] Organic field-effect transistor (OFET) has good signal amplification ability, good flexibility, solution processability and low power consumption. It is regarded as an ideal carrier of the new generation of flexible pressure sensors and a strong candidate for designing artificial synaptic pressure sensors. However, there are still many challenges in designing artificial synaptic pressure sensors through OFET, including: 1) Artificial synaptic pressure sensors need to have excellent response capabilities to tactile / pressure signals and have a fast response speed to external pressure stimuli. However, traditional floating gate OFET pressure sensors have extremely high sensitivity only in the initial stage of pressure application. After that, due to the polarization relaxation of the dielectric layer and the repeated deformation of the mechanical structure, the response ability of the sensor gradually weakens. The response time is usually difficult to exceed 10ms, and it is difficult to accurately capture the rapidly changing dynamic pressure signals. This has a considerable limitation on the OFET pressure sensor to simulate the biological synaptic function. 2) After receiving the pressure signal, the artificial synaptic pressure sensor needs to transmit and process the signal by simulating the dynamic weight adjustment mechanism of the synapse, and respond to multiple aspects such as pressure intensity, frequency and duration. However, traditional OFET pressure sensors focus on single pressure amplitude detection, lack the ability to intelligently process multiple pressure signals such as pressure pulse frequency, timing and cumulative effect, and are difficult to support advanced functions such as neuromorphic computing. Therefore, it is necessary to develop new organic artificial synaptic transistor pressure sensors, and through the design innovation of device structure and integrated materials, to realize pressure sensors and arrays with bionic synaptic sensing performance, so as to enhance their practical application value. Summary of the invention

[0006] In view of this, one of the objects of the present invention is to provide an organic artificial synapse transistor pressure sensor; a second object of the present invention is to provide a method for preparing an organic artificial synapse transistor pressure sensor; a third object of the present invention is to provide an organic artificial synapse transistor pressure sensor array; a fourth object of the present invention is to provide an organic artificial synapse transistor pressure sensor and its array for use in neuromorphic computing technologies such as biological synapse behavior simulation, intelligent touch recognition of Braille characters, as well as tactile imaging, electrical equipment monitoring, sensing, storage and computing integrated intelligent terminals, human-computer interaction, etc.

[0007] To achieve the above object, a first aspect of the present invention provides an organic artificial synaptic transistor pressure sensor based on a suspension structure, which includes a substrate, source-drain electrodes deposited on the surface of the substrate, support layers fixed on the surface of the substrate and distributed on both sides of the source-drain electrodes, and a suspension structure fixed on the support layers. The suspension structure includes an organic semiconductor layer, a dielectric passivation layer, a polyelectrolyte dielectric layer, and a flexible gate stacked in sequence from bottom to top. Among them, an air gap is formed between the organic semiconductor layer of the suspension structure, the substrate, the support layers on both sides of the substrate surface, and the source-drain electrodes.

[0008] By designing the novel suspension structure, the present invention simulates the force-bearing process of the biological skin under dynamically applied pressure, thereby realizing the simulation of basic biological synaptic behaviors, including excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), and the transition from short-term memory (STM) to long-term memory (LTM). In addition, by introducing a dielectric passivation layer on the surface of the polyelectrolyte dielectric layer of the transistor, unnecessary ion migration is avoided, and the interface trap recovery speed is accelerated to improve the slow response time of the pressure sensor, thereby improving the response time and stability of the pressure sensor.

[0009] Further, the material of the substrate is any one or several of polyethylene terephthalate, polyimide, polyethylene naphthalate, polydimethylsiloxane, polycarbonate, polyvinyl alcohol, glass, silicon wafer, or sapphire.

[0010] Preferably, the material of the substrate is any one of polyethylene terephthalate, polyimide, polyethylene naphthalate, polycarbonate, or polyvinyl alcohol.

[0011] Further, the source-drain electrodes are an electrode pair formed by a source electrode and a drain electrode; the electrode pair is in an interdigitated electrode structure; the material of the electrode pair is any one or several of gold, silver, aluminum, copper, chromium, platinum, titanium, nickel, indium tin oxide, fluorine-doped tin oxide, zinc aluminum oxide, carbon nanotubes, graphene, conductive polymer materials, or conductive polymers.

[0012] Preferably, the material of the electrode pair is any one of gold, aluminum, copper, or indium tin oxide.

[0013] Further, the material of the support layer is at least one of polyimide, polydimethylsiloxane, ethylene-vinyl acetate, thermoplastic polyurethane, or rubber; wherein, by controlling the support layer, the height of the air gap can be controlled, and the height range of the air gap is 10 - 800 μm.

[0014] Preferably, the material of the support layer is at least one of polyimide, thermoplastic polyurethane, or rubber; the height range of the air gap is 25 - 700 μm.

[0015] Further preferably, the material of the support layer is polyimide; the height range of the air gap is 50-500 μm.

[0016] Furthermore, the material of the organic semiconductor layer is any one or more of organic small molecule semiconductor materials, conjugated polymer semiconductor materials, or semiconductor composites of organic small molecules and conjugated polymers.

[0017] Among them, the organic small molecule semiconductor materials include any one or more of pentacene or its derivatives, 7,7,8,8-tetracyanoquinodimethane or its derivatives; the conjugated polymer semiconductor materials include poly{4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thiopheno[3,4-b]thiophenediyl} or its derivatives, indacenodithiophene-benzothiadiazole copolymer, or 7,7,8,8-tetracyanoquinodimethane-doped indacenodithiophene-benzothiadiazole copolymer.

[0018] Preferably, the material of the organic semiconductor layer is a conjugated polymer semiconductor material, selected from any one of indacenodithiophene-benzothiadiazole copolymer and 7,7,8,8-tetracyanoquinodimethane-doped indacenodithiophene-benzothiadiazole copolymer.

[0019] Furthermore, the material of the dielectric passivation layer is any one or more of pentaerythritol penta / hexacrylate-based photocurable crosslinked polymers and their derivatives, polymethyl methacrylate and its derivatives, polystyrene or its derivatives, amorphous fluororesins or their derivatives, and metal oxide dielectrics.

[0020] Preferably, the material of the dielectric passivation layer is any one or more of pentaerythritol penta / hexacrylate-based photocurable crosslinked polymers, polystyrene or its derivatives.

[0021] Further preferably, the material of the dielectric passivation layer is pentaerythritol penta / hexacrylate-based photocurable crosslinked polymers and their derivatives, and its preparation process is as follows:

[0022] First, mix pentaerythritol penta / hexacrylate monomers and a photoinitiator and dissolve them in a solvent, and stir evenly to obtain a precursor solution of the dielectric passivation layer material. The mass fraction of the pentaerythritol penta / hexacrylate monomers in the precursor solution is 0.5-10 wt.%, and the mass fraction of the photoinitiator is 0.01-1 wt.%; wherein, the solvent is any one or more of methanol, ethanol, or isopropanol.

[0023] Then, the precursor solution is processed into a film by the solution spin-coating method, with the rotation speed of spin-coating being 500 - 4000 rpm and the time of spin-coating being 30 - 120 s;

[0024] Finally, after spin-coating, ultraviolet cross-linking curing is carried out with a wavelength of 365 nm, the time of photo-curing being 2 - 30 min, and the environment of photo-curing being room-temperature atmospheric environment. After the photo-curing treatment, the dielectric passivation layer is prepared and formed.

[0025] Furthermore, the material of the polyelectrolyte dielectric layer is at least one of polyacrylic acid-based electrolytes, polyacrylamide-based electrolytes, polyethylene glycol and its derivatives, polyvinyl alcohol and its derivatives, dielectric materials formed by blending polyacrylic acid-based electrolytes and polymethyl methacrylate, polyelectrolyte composite dielectric materials formed by blending polyacrylic acid-based electrolytes and polyethylene glycol, or polyelectrolyte composite dielectric materials formed by blending polyacrylic acid-based electrolytes and polyvinyl alcohol.

[0026] Preferably, the material of the polyelectrolyte dielectric layer is at least one of polyacrylic acid-based electrolytes, polyethylene glycol and its derivatives, polyvinyl alcohol and its derivatives, dielectric materials formed by blending polyacrylic acid-based electrolytes and polymethyl methacrylate, and polyelectrolyte composite dielectric materials formed by blending polyacrylic acid-based electrolytes and polyethylene glycol.

[0027] More preferably, the material of the polyelectrolyte dielectric layer is at least one of polyacrylic acid-based electrolytes and their derivatives, polyvinyl alcohol and its derivatives, and polyelectrolyte composite dielectric materials formed by blending polyacrylic acid-based electrolytes and polyethylene glycol.

[0028] Furthermore, the material of the flexible gate is at least one of flexible polyethylene terephthalate containing a metal electrode thin film, flexible polyethylene naphthalate containing a metal electrode thin film, flexible polyethylene terephthalate containing indium tin oxide thin film, flexible polyethylene naphthalate containing indium tin oxide thin film, aluminum foil, silver nanowires, carbon nanotubes, graphene, and conductive polymers. Among them, the conductive polymer is a high molecular material with a conjugated main electron system on the main chain and reaching a conductive state through doping; the conductive polymer includes any one of polyaniline, polythiophene, poly(3,4-ethylenedioxythiophene), or polyacetylene. The material of the metal electrode thin film is any one of gold, silver, or aluminum.

[0029] Preferably, the material of the flexible gate is at least one of flexible polyethylene terephthalate containing a metal electrode thin film, flexible polyethylene naphthalate containing a metal electrode thin film, flexible polyethylene terephthalate containing indium tin oxide thin film, and flexible polyethylene naphthalate containing indium tin oxide thin film.

[0030] In a second aspect of the present invention, there is provided an organic artificial synaptic transistor pressure sensor array based on a suspension structure. The pressure sensor array includes a plurality of the pressure sensors described in the first aspect of the present invention arranged in an array, and the pressure sensor array includes at least four sets of source-drain electrodes.

[0031] In a third aspect of the present invention, there is provided a method for preparing an organic artificial synaptic transistor pressure sensor based on a suspension structure, the method including the following steps:

[0032] (1) Obtain a flexible substrate, and adopt a vacuum evaporation coating technique to deposit interdigital source-drain electrodes on the flexible substrate through a patterned mask template to obtain a flexible substrate / source-drain electrode assembly;

[0033] (2) Attach a supporting material to the left and right edges of the flexible substrate to form a support layer;

[0034] (3) Obtain a flexible gate, prepare a polyelectrolyte dielectric layer on the flexible gate by a solution spin-coating method combined with a low-temperature annealing treatment, and continue to form a dielectric passivation layer on the polyelectrolyte dielectric layer by a solution spin-coating method combined with a photocuring crosslinking process, so as to obtain a flexible gate / polyelectrolyte dielectric layer / dielectric passivation layer laminated structure;

[0035] Among them, the flexible gate can be prepared by a vacuum coating technique or directly use an existing flexible gate product;

[0036] (4) Prepare an organic semiconductor layer on the dielectric passivation layer by a solution spin-coating method to obtain a flexible gate / polyelectrolyte dielectric layer / dielectric passivation layer / organic semiconductor layer laminated structure;

[0037] (5) Orient the suspension structure composed of the flexible gate, the polyelectrolyte dielectric layer, the dielectric passivation layer, and the organic semiconductor layer towards the flexible substrate with source-drain electrodes deposited on the surface, and fix it on two support layers to form an air gap between the organic semiconductor layer, the support layer, the source-drain electrodes, and the flexible substrate, that is, the organic artificial synaptic transistor pressure sensor based on the suspension structure is prepared.

[0038] Among them, by controlling the height of the support layer, the height of the air gap can be controlled to be 10-800 μm.

[0039] Further, in step (3), when preparing the polyelectrolyte dielectric layer, the concentration of the polyelectrolyte material in the solution used in the solution spin-coating method is 5-50 mg / mL, the spinning speed is 200-4000 rpm, the spinning time is 30-120 s, the temperature of the annealing treatment is 50-200 °C, and the annealing time is not less than 60 min;

[0040] When preparing the dielectric passivation layer, it is necessary to first configure the precursor solution of the dielectric passivation layer. The mass fraction of the monomer of the dielectric passivation layer material in the solution is 0.5-10 wt.%, the mass fraction of the photoinitiator is 0.01-1 wt.%, and the solvent is any one or several of methanol, ethanol or isopropanol. Among them, the rotation speed of solution spin coating is 500-4000 rpm, and the time of ultraviolet light curing crosslinking is 2-30 min.

[0041] In the fourth aspect of the present invention, there is provided an application of the organic artificial synaptic transistor pressure sensor described in the first aspect or the organic artificial synaptic transistor pressure sensor array described in the second aspect in neuromorphic computing technologies such as biological synaptic behavior simulation and intelligent touch recognition of braille characters, as well as in fields such as tactile imaging, electrical equipment monitoring, integrated sensing and computing intelligent terminals, and human-computer interaction.

[0042] The beneficial effects of the present invention are as follows:

[0043] (1) The organic artificial synaptic transistor pressure sensor proposed by the present invention is realized based on a novel suspension structure of a flexible gate / polyelectrolyte dielectric layer / dielectric passivation layer / organic semiconductor layer. By applying different pressures to the sensor, the contact between the organic semiconductor layer and the source-drain electrodes is changed, causing a change in the interfacial contact resistance between the two, thereby resulting in a change in the output current of the sensor and achieving a highly sensitive response to tactile / pressure signals. Due to the innovative design of the suspension structure based on the flexible gate / polyelectrolyte dielectric layer / dielectric passivation layer / organic semiconductor layer in the present invention, the capacitance remains basically unchanged under external force stimulation. Therefore, the present invention breaks through the capacitance change mechanism of the traditional floating gate structure from the pressure response mechanism, but uses the control of the novel suspension structure and the interface contact of the source-drain electrodes to achieve a mechanism dominated by resistance change. Therefore, the present invention provides a beneficial exploration and new choice for the novel flexible organic transistor pressure sensor.

[0044] (2) By introducing a suitable dielectric passivation layer to passivate the polyelectrolyte dielectric layer, the present invention improves the stability of the sensor, and enhances the response speed and pressure detection range of the organic artificial synaptic transistor pressure sensor. The composite structure stacked between the polyelectrolyte dielectric layer and the dielectric passivation layer can combine the advantages of different dielectric layers (for example, the polyelectrolyte dielectric layer material used in the present invention has a double-layer effect, which can enable the gate dielectric layer to have a high capacitance, thereby endowing the transistor with the ability to operate at low voltage. The dielectric passivation layer material can effectively suppress the leakage and hysteresis of low-voltage organic transistors and sensors). As a result, the pressure sensor device proposed in the present invention achieves ultra-high sensitivity and fast response characteristics within a low operating voltage of -2V. Among them, the sensitivity is as high as 315.6 kPa-1, and the response time is less than 10 ms. Therefore, the organic artificial synaptic transistor pressure sensor provided by the present invention can maintain high sensitivity and fast response ability within a wide detection range of 0 to 70.1 kPa for pressure. This excellent sensing performance at low power consumption provides technical support for the practical applications of flexible wearable electronics and skin-like intelligent devices.

[0045] (3) The organic artificial synaptic transistor pressure sensor proposed by the present invention has the advantages of simple structure, excellent performance, and low energy consumption. By applying different voltages to the gate, it can simulate the key behavioral characteristics and functions of biological synapses, including excitatory postsynaptic currents with adjustable amplitudes, paired-pulse facilitation effects, and the conversion function from short-term memory to long-term memory. These pressure synaptic behaviors are crucial for processing complex tactile / mechanical signals and also provide a feasible hardware design basis for the development of brain-inspired neuromorphic tactile systems.

[0046] (4) The organic artificial synaptic transistor pressure sensor proposed by the present invention can be efficiently designed and integrated into a large-area flexible organic artificial synaptic pressure sensor array, realizing the reading of different pressure amplitudes and being able to accurately respond. The artificial synaptic transistor pressure sensor array provided by the present invention, combined with the convolutional neural network algorithm, can achieve accurate recognition of Braille letters, and the test accuracy can be as high as 98%. These results demonstrate their application potential in fields such as wearable assistive devices for the blind, electronic skin, and tactile imaging.

[0047] (5) The organic artificial synaptic transistor pressure sensor and its array proposed by the present invention can also be used as an important carrier to be fused and integrated with various flexible materials, devices, and chips, greatly improving the data acquisition and processing speed, as well as the storage and computing capabilities. Thereby, it provides an important basis and reference for the development of new sensing integrated electronic devices and sense-storage-computation integrated intelligent terminals, the intelligent monitoring of electrical equipment, and the development and application of human-computer interaction systems.

[0048] Other advantages, objects, and features of the present invention will be set forth in part in the description which follows and, in part, will be obvious to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present invention. The objectives and other advantages of the present invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter. Description of the Drawings

[0049] In order to make the objectives, technical solutions, and advantages of the present invention more apparent, the present invention will be described in detail below with reference to the accompanying drawings, where:

[0050] Figure 1 Schematic diagram of the structure of the organic artificial synaptic transistor pressure sensor prepared in Example 1;

[0051] Figure 2 Transfer characteristic curves of the organic artificial synaptic transistor pressure sensor prepared in Example 1 under different pressures;

[0052] Figure 3 Relative change of the output current of the organic artificial synaptic transistor pressure sensor prepared in Example 1 with the applied pressure;

[0053] Figure 4 Dynamic response of the organic artificial synaptic transistor pressure sensor prepared in Example 1 when applying and removing pressure;

[0054] Figure 5 Double-pulse facilitation behavior of the organic artificial synaptic transistor pressure sensor prepared in Example 1;

[0055] Figure 6 Pressure pulse amplitude dependence of the organic artificial synaptic transistor pressure sensor prepared in Example 1;

[0056] Figure 7 Pressure pulse number dependence of the organic artificial synaptic transistor pressure sensor prepared in Example 1;

[0057] Figure 8 Schematic diagram of the structure of the organic artificial synaptic transistor pressure sensor array prepared in Example 17;

[0058] Figure 9 Accuracy characteristic diagram of identifying Braille letters by the organic artificial synaptic transistor pressure sensor array prepared in Example 17 under different training times.

[0059] Reference numerals: 1 - substrate; 2 - source-drain electrode; 3 - support layer; 4 - air gap; 5 - organic semiconductor layer; 6 - dielectric passivation layer; 7 - polyelectrolyte dielectric layer; 8 - flexible gate. Detailed Description of the Embodiments

[0060] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0061] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as limiting the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0062] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0063] For those embodiments not specifying specific conditions, they can all be carried out according to the prior art. Unless otherwise specified, the raw materials and solvents in the embodiments of the present invention can all be obtained through public channels, where:

[0064] The chlorobenzene solvent and methanol solvent can be purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd.;

[0065] The polymer semiconductor material indacenodithiophene-benzothiadiazole copolymer (PIDT-BT) can be purchased from Shenzhen Ruixun Optoelectronic Materials Technology Co., Ltd.;

[0066] Polyacrylic acid (PAA) and polyethylene glycol (PEG) can be purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd.;

[0067] Pentaerythritol penta / hexacrylate monomer DPHA and photoinitiator Irgacure 184 can be purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd.;

[0068] In addition, glass substrates, plastic substrates such as polyethylene terephthalate (PET) films, polyethylene naphthalate (PEN) films, PET films coated with ITO electrodes, and PEN films coated with ITO electrodes can all be purchased from Shenzhen Huanan Xiangcheng Technology Co., Ltd.

[0069] The analysis methods used in the following examples are as follows: the Agilent 4155C semiconductor analyzer is used to test the current changes of the organic artificial synaptic transistor pressure sensor and its array, and the digital oscilloscope DS1102CA is used to test the response time of the organic artificial synaptic transistor pressure sensor.

[0070] Example 1

[0071] 1. This example provides an organic artificial synaptic transistor pressure sensor based on a suspension structure, and its preparation method is as follows:

[0072] (1) Prepare source and drain electrodes using vacuum evaporation coating technology

[0073] By means of vacuum evaporation coating, on a 125-μm flexible PEN substrate 1, a 50-nm-thick gold is prepared as the source and drain electrodes 2 using a mask template with an interdigital pattern having an aspect ratio of 150:1. The vacuum degree of thermal evaporation is about 2×10 -4 Pa, and the evaporation rate is about to obtain a flexible substrate / source and drain electrode assembly.

[0074] (2) Prepare a support layer

[0075] In an air environment, PI tapes are attached to the left and right edges of the flexible PEN substrate 1 of the above flexible substrate / source and drain electrode assembly as the support layer 3, and the height of the support layer 3 is controlled to be about 160 μm by controlling the number of layers of the PI tapes.

[0076] (3) Prepare a laminated structure of a polyelectrolyte dielectric layer and a dielectric passivation layer

[0077] First, prepare the polyelectrolyte dielectric layer 7 using the solution spin-coating method and the low-temperature annealing process:

[0078] Step 1: In a fume hood, weigh PAA and PEG with a mass ratio of 4:6 and dissolve them in 4 mL of methanol solvent, and keep the PAA concentration at 30 mg / mL. Then, place the solution on a magnetic stirring table and stir at room temperature to form a clear and transparent PAA:PEG solution;

[0079] Step 2: Spin-coat the PAA:PEG solution prepared in Step 1 on the PEN-ITO flexible gate 8 at a spin coater speed of 500 rpm for 60 s, and spin-coat twice. After spin-coating, transfer them to a heating stage at 80 °C for thermal annealing for 2 h to form a polyelectrolyte dielectric layer 7, thereby obtaining a flexible gate / polyelectrolyte dielectric layer assembly.

[0080] Secondly, a dielectric passivation layer 6 is prepared by a solution spin-coating method and an ultraviolet curing process

[0081] Step 1: In a fume hood, weigh DPHA and photoinitiator Irgacure 184 with a mass ratio of 10:1 and dissolve them in 4 mL of methanol solvent, controlling the DPHA content to account for 2 wt.% of the total solution. Then place the solution on a magnetic stirring table and stir at room temperature to form a clear and transparent DPHA solution;

[0082] Step 2: Spin-coat the DPHA solution prepared in Step 1 on the PAA:PEG polyelectrolyte dielectric layer 7 at a spin coater speed of 3000 rpm for 60 s, and spin-coat once. After spin-coating, transfer them to an ultraviolet curing box for curing for 10 min to form a pentaerythritol penta / hexacrylate photocurable cross-linked polymer dielectric passivation layer 6, thereby obtaining a flexible gate / polyelectrolyte dielectric layer / dielectric passivation layer assembly.

[0083] (4) Prepare an organic semiconductor layer by a solution spin-coating method and a low-temperature annealing process in an air environment

[0084] Step 1: Weigh 10 mg of PIDT-BT, add 2 mL of chlorobenzene as a solvent, and after mixing, place it on a magnetic stirring table and stir at room temperature for 12 h to form a dark and clear solution;

[0085] Step 2: Spin-coat the PIDT-BT chlorobenzene solution from Step 1 on the surface of the dielectric passivation layer 6 sample in a nitrogen environment, controlling the speed to 2000 rpm and the time to 60 s; after spin-coating, place the sample on a heating stage at 80 °C for thermal annealing for 20 min to obtain a flexible gate / polyelectrolyte dielectric layer / dielectric passivation layer / organic semiconductor layer assembly.

[0086] (5) Press the upper and lower parts together to form an organic artificial synaptic transistor pressure sensor based on a suspended structure

[0087] In an air environment, place the above-prepared flexible gate / polyelectrolyte dielectric layer / dielectric passivation layer / organic semiconductor layer assembly with the surface facing the suspended structure of the flexible substrate / source-drain electrode on the support layer and fix it. By controlling the height of the support layer, a tiny air gap of about 160 μm can be formed between the source-drain electrode 2 and the organic semiconductor layer 5. After preparation, an organic artificial synaptic transistor pressure sensor based on a suspended structure is obtained.

[0088] As shown Figure 1 in the figure is the organic artificial synaptic transistor pressure sensor based on the suspension structure prepared above. The composition of the pressure sensor includes a substrate 1 at the bottom, source and drain electrodes 2 deposited on its surface, support layers 3 at the left and right ends, and a suspension structure at the top. The suspension structure is composed of a flexible gate 8, a polyelectrolyte dielectric layer 7, a dielectric passivation layer 6, and an organic semiconductor layer 5 stacked in sequence from top to bottom; an air gap 4 is formed between the organic semiconductor layer 5 of the suspension structure, the support layers 3 at the left and right ends, the substrate 1, and the source and drain electrodes 2 deposited on its surface.

[0089] 2. Conduct sensing performance tests on the above organic artificial synaptic transistor pressure sensor

[0090] Use an Agilent 4155C semiconductor parameter analyzer to test the transfer characteristic curves of the organic artificial synaptic transistor pressure sensor under different pressures (as Figure 2 shown), where the source-drain voltage V D is -2V. It can be seen from Figure 2 that the initial current I0 of the pressure sensor is very small, only about 10 -9 A magnitude. Once the threshold pressure is reached, the device will operate at a low voltage of -2V. Figure 3 It provides the relative change of the output current of the organic artificial synaptic transistor pressure sensor and the applied pressure. It can be seen that the sensitivity of the organic artificial synaptic transistor pressure sensor provided by the present invention to pressure response can be divided into two linear intervals: in the pressure range of 0 to 42.0 kPa, the pressure-induced rapid increase in the contact area between the organic semiconductor layer and the source and drain electrodes causes the source-drain current I D of the device to increase rapidly, and the corresponding sensitivity of the sensor is as high as 315.6 kPa -1 ; in the pressure range of 42.0 to 70.1 kPa, the growth of the contact area between the organic semiconductor layer and the source and drain electrodes tends to saturate, the current increase slows down, and the sensitivity drops to 134.7 kPa -1 . It should be noted that the sensitivities in both intervals are maintained above 100 kPa-1, demonstrating the high-sensitivity and wide-range detection ability of the organic artificial synaptic transistor pressure sensor proposed by the present invention to pressure response.

[0091] Due to the organic artificial synaptic transistor pressure sensor prepared in this embodiment, a suspension structure based on a flexible gate / polyelectrolyte dielectric layer / dielectric passivation layer / organic semiconductor layer is innovatively designed. When pressure is applied to the pressure sensor, the capacitance remains basically unchanged. The high sensitivity of this type of pressure sensor is mainly attributed to the fact that the suspension structure enables the sensor to achieve a very low I D without applying force; while when an external force is applied, as the interface fits closely, a higher I DIn addition, the selection and optimization of the flexible electrode and the substrate can further improve the pressure sensitivity of the organic artificial synaptic transistor pressure sensor.

[0092] The organic artificial synaptic transistor pressure sensor prepared in this embodiment is connected in series with a 1 TΩ resistor, and a digital oscilloscope DS1102CA is connected in parallel with the resistor to test the dynamic response of the organic artificial synaptic transistor pressure sensor. The test results are as Figure 4 shown. From Figure 4 it can be seen that after applying (on state) and removing (off state) periodic pressure, the current in the circuit changes, and the digital oscilloscope records the voltage change across the resistor. The response time of this sensor device (the rise time and fall time are approximately 8 ms and 4 ms respectively) is within 10 ms, showing a fast response ability to pressure and can better meet the actual application requirements of tactile / pressure sensors.

[0093] 3. Perform synaptic characteristic tests on the above organic artificial synaptic transistor pressure sensor

[0094] Perform pressure synaptic behavior tests on the organic artificial synaptic transistor pressure sensor prepared in this embodiment. Its paired-pulse facilitation behavior characteristics are as Figure 5 shown. The excitatory postsynaptic current is triggered by two consecutive 2.26 N pressure pulses (pulse width is 200 ms, pulse interval is 200 ms). From Figure 5 it can be seen that the excitatory postsynaptic current A2 induced by the second pressure pulse is 0.707 nA, and the excitatory postsynaptic current A1 of the first pressure pulse is 0.497 nA. It can be seen that the ratio of A2 / A1 is 1.42, showing a significant enhancement trend.

[0095] Further study the influence of the pressure pulse amplitude on the excitatory postsynaptic current of the organic artificial synaptic transistor pressure sensor. As Figure 6 shown, under fixed pulse parameters, the excitatory postsynaptic current triggered by a 2.3 N pressure pulse has an increase of about 50% (A5 / A1 = 150%) in the amplitude of the fifth stimulus response compared to the first stimulus response amplitude (A1). When the pressure pulse is further increased to 2.6 N, A5 / A1 = 167%, indicating that as the amplitude of the mechanical external force stimulus increases, the response of the organic artificial synaptic transistor pressure sensor to mechanical tactile stimuli also increases. In addition, the pressure pulse number-dependent behavior of the organic artificial synaptic transistor pressure sensor is also tested. The test results are as Figure 7 shown. It can be seen that as the number of pulses increases, the excitatory postsynaptic current gradually shows a transition from short-term plasticity to long-term plasticity.

[0096] Therefore, the organic artificial synaptic transistor pressure sensor based on the suspension structure proposed by the present invention successfully simulates the characteristic behaviors and memory characteristics of biological synapses, providing a new perspective for the application exploration of organic artificial synaptic pressure sensors.

[0097] Examples 2 to 16

[0098] The different parts of the preparation processes of the organic artificial synaptic transistor pressure sensors in Examples 2 to 16 and Example 1 are shown in Table 1, and the parts not described are the same as those in Example 1.

[0099] Table 1

[0100]

[0101] Similarly, the organic artificial synaptic transistor pressure sensors prepared in Examples 2 to 16 were subjected to sensing performance tests and synaptic characteristic analyses, and the test conditions were the same as those in Example 1. Finally, the performance test results of the obtained organic artificial synaptic transistor pressure sensors were similar to those of the pressure sensor in Example 1.

[0102] Example 17

[0103] 1. Since the organic artificial synaptic transistor pressure sensors based on the suspension structure described in Examples 1 to 16 have the characteristics of low power consumption, high sensitivity, fast response, and the function of simulating biological synapses, they can be further designed and integrated into a low-power organic artificial synaptic transistor pressure sensor array (4×4 model) for braille recognition applications. The structure of the organic artificial synaptic transistor pressure sensor array is as Figure 8 shown, and its specific preparation method is as follows:

[0104] (1) Prepare source and drain electrodes by vacuum evaporation coating technology

[0105] By the method of vacuum evaporation coating, on a 125-μm flexible PEN substrate, a 50-nm-thick gold is prepared as the source and drain electrodes using a mask template with an interdigital pattern having an aspect ratio of 150:1, and 4 columns of 16 uniform channels are deposited side by side, where 16 source electrodes are connected in parallel and the drain electrodes are independent. The vacuum degree of thermal evaporation is about 2×10 -4 Pa, and the evaporation rate is about to obtain a substrate / source-drain electrode array assembly.

[0106] (2) Prepare a support layer

[0107] In an air environment, PI tape is attached to the left and right edges of the flexible PEN substrate of the above flexible substrate / source-drain electrode assembly as the support layer, and the height of the support layer is controlled to be about 160 μm by controlling the number of layers of the PI tape.

[0108] (3) Preparation of a laminated structure of a polyelectrolyte dielectric layer and a dielectric passivation layer

[0109] First, a polyelectrolyte dielectric layer is prepared by a solution spin-coating method and a low-temperature annealing process:

[0110] Step 1: In a fume hood, weigh PAA and PEG with a mass ratio of 6:4 and dissolve them in 4 mL of methanol solvent, controlling the concentration of PAA to be 30 mg / mL. Then, place the solution on a magnetic stirring table and stir at room temperature to form a clear and transparent PAA:PEG solution;

[0111] Step 2: Spin-coat the PAA:PEG solution prepared in Step 1 on the PEN-ITO flexible gate. The speed of the spin coater is 500 rpm and the time is 60 s. Spin-coat twice. After spin-coating, transfer them to a heating table at 80 °C and anneal thermally for 2 h to form a polyelectrolyte dielectric layer, thereby obtaining a flexible gate / polyelectrolyte dielectric layer assembly.

[0112] Secondly, a dielectric passivation layer is prepared by a solution spin-coating method and an ultraviolet curing process

[0113] Step 1: In a fume hood, weigh DPHA and photoinitiator Irgacure 184 with a mass ratio of 10:1 and dissolve them in 4 mL of methanol solvent, controlling the concentration of DPHA in the total solution to be 2 wt.%. Then, place the solution on a magnetic stirring table and stir at room temperature to form a clear and transparent DPHA solution;

[0114] Step 2: Spin-coat the DPHA solution prepared in Step 1 on the PAA:PEG polyelectrolyte dielectric layer. The speed of the spin coater is 3000 rpm and the time is 60 s. Spin-coat once. After spin-coating, transfer them to an ultraviolet curing box and cure for 10 min to form a dielectric passivation layer, thereby obtaining a flexible gate / polyelectrolyte dielectric layer / dielectric passivation layer assembly.

[0115] (4) Preparation of an organic semiconductor layer by a solution spin-coating method and a low-temperature annealing process in an air environment

[0116] Step 1: Weigh 10 mg of PIDT-BT, add 2 mL of chlorobenzene as a solvent, and mix them. Then, place the mixture on a magnetic stirring table and stir at room temperature for 12 h to form a dark and clear solution;

[0117] Step 2: Spin-coat the PIDT-BT chlorobenzene solution from Step 1 on the surface of the dielectric passivation layer sample in a nitrogen environment, controlling the speed to be 2000 rpm and the time to be 60 s. After spin-coating, place the sample on a heating table at 80 °C and anneal thermally for 20 min to obtain a flexible gate / polyelectrolyte dielectric layer / dielectric passivation layer / organic semiconductor layer assembly.

[0118] (5) The upper and lower parts are pressed together to form an organic artificial synaptic transistor pressure sensor array based on a suspended structure.

[0119] In an air environment, the above-prepared component of the flexible gate / polyelectrolyte dielectric layer / dielectric passivation layer / organic semiconductor layer with the surface facing the suspended structure of the flexible substrate / source-drain electrode array is placed on the support layer and fixed. By controlling the height of the support layer, a tiny air gap of about 160 μm is formed between the source-drain electrode and the organic semiconductor layer. After preparation, the organic artificial synaptic transistor pressure sensor array is obtained.

[0120] 2. Conduct a Braille recognition application test on the above organic artificial synaptic transistor pressure sensor array.

[0121] The organic artificial synaptic transistor pressure sensor array prepared in this embodiment is combined with the convolutional neural network (CNN) algorithm for tactile perception and recognition of Braille characters. After training, the system tested a single Braille character, as Figure 9 shown. It can be seen that as the number of training times increases, the recognition accuracy of the organic artificial synaptic transistor pressure sensor array prepared in this embodiment for Braille characters gradually increases, and the recognition accuracy can finally stabilize at about 98%.

[0122] In summary, the present invention proposes an organic artificial synaptic transistor pressure sensor and its array, preparation method and application based on a novel suspended structure. The organic artificial synaptic transistor pressure sensor of the present invention has the capabilities of operating at low voltage (as low as -2V), high sensitivity (up to 315.6 kPa -1 ), a wide pressure detection range (0 - 70.1 kPa), and fast response ability (response time < 10 ms), and can simulate characteristic biological synaptic functions such as excitatory postsynaptic current, paired-pulse facilitation, and the transition from short-term memory to long-term memory. These pressure synaptic behaviors are crucial for processing complex signals. In addition, the organic artificial synaptic transistor pressure sensor based on the suspended structure is also easy to design and be integrated into a flexible large-area pressure synaptic array. By combining it with the convolutional neural network algorithm, it can not only provide accurate and reliable Braille character recognition ability, but also provide new possibilities for potential applications of intelligent wearable devices, electronic skin, sensor-storage-computation intelligent terminals, and human-computer interaction technologies.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered by the scope of the claims of the present invention.

Claims

1. An organic artificial synaptic transistor pressure sensor based on a suspension structure, characterized in that, The pressure sensor includes a substrate, source-drain electrodes deposited on the surface of the substrate, support layers fixed on the surface of the substrate and distributed on both sides of the source-drain electrodes, and a suspended structure fixed on the support layers; the suspended structure includes an organic semiconductor layer, a dielectric passivation layer, a polyelectrolyte dielectric layer, and a flexible gate stacked in sequence from bottom to top. Among them, an air gap is formed between the organic semiconductor layer of the suspended structure, the substrate, the support layers on both sides of the substrate surface, and the source-drain electrodes.

2. The organic artificial synaptic transistor pressure sensor according to claim 1, wherein The material of the dielectric passivation layer is any one or several of pentaerythritol penta / hexacrylate photocurable crosslinked polymers and their derivatives, polymethyl methacrylate and its derivatives, polystyrene or its derivatives, amorphous fluororesins or their derivatives, and metal oxide dielectrics.

3. The organic artificial synaptic transistor pressure sensor according to claims 1 to 2, characterized in that, The material of the dielectric passivation layer is pentaerythritol penta / hexacrylate photocurable crosslinked polymer and its derivatives, and its preparation process is as follows: First, mix pentaerythritol penta / hexacrylate monomers and a photoinitiator and dissolve them in a solvent, and stir evenly to obtain a precursor solution of the dielectric passivation layer material. The mass fraction of the pentaerythritol penta / hexacrylate monomer in the precursor solution is 0.5 - 10 wt.%, and the mass fraction of the photoinitiator is 0.01 - 1 wt.%; among them, the solvent is any one or several of methanol, ethanol, or isopropanol. Then, process the precursor solution into a film by solution spin coating. The rotation speed of spin coating is 500 - 4000 rpm, and the spin coating time is 30 - 120 s. Finally, after spin coating, perform ultraviolet crosslinking curing. The light curing time is 2 - 30 min, and the light curing environment is a room temperature atmosphere environment. After the light curing treatment, the dielectric passivation layer is prepared and formed.

4. The organic artificial synaptic transistor pressure sensor according to claim 1, characterized in that The material of the support layer is at least one of polyimide, polydimethylsiloxane, ethylene-vinyl acetate, thermoplastic polyurethane, or rubber; the height of the air gap is 10 - 800 μm.

5. The organic artificial synaptic transistor pressure sensor according to claim 1, wherein The material of the substrate is any one or several of polyethylene terephthalate, polyimide, polyethylene naphthalate, polydimethylsiloxane, polycarbonate, polyvinyl alcohol, glass, silicon wafer, or sapphire. The source-drain electrode is an electrode pair formed by a source electrode and a drain electrode; the electrode pair is in an interdigital electrode structure; the material of the electrode pair is any one or several of gold, silver, aluminum, copper, chromium, platinum, titanium, nickel, indium tin oxide, fluorine-doped tin oxide, zinc aluminum oxide, carbon nanotubes, graphene, conductive polymer materials, or conductive polymers. The material of the organic semiconductor layer is any one or several of organic small molecule semiconductor materials, conjugated polymer semiconductor materials, or semiconductor composite materials of organic small molecules and conjugated polymers.

6. The organic artificial synaptic transistor pressure sensor according to claim 1, wherein The material of the polyelectrolyte dielectric layer is at least one of polyacrylic acid electrolytes, polyacrylamide electrolytes, polyethylene glycol and its derivatives, polyvinyl alcohol and its derivatives, dielectric materials formed by blending polyacrylic acid electrolytes and polymethyl methacrylate, polyelectrolyte composite dielectric materials formed by blending polyacrylic acid electrolytes and polyethylene glycol, or polyelectrolyte composite dielectric materials formed by blending polyacrylic acid electrolytes and polyvinyl alcohol. The flexible gate material is at least one of flexible polyethylene terephthalate containing a metal electrode thin film, flexible polyethylene naphthalate containing a metal electrode thin film, flexible polyethylene terephthalate containing an indium tin oxide thin film, flexible polyethylene naphthalate containing an indium tin oxide thin film, aluminum foil, silver nanowires, carbon nanotubes, graphene, and a conductive polymer; wherein, the conductive polymer is a high molecular material having a conjugated main electron system on the main chain and reaching a conductive state through doping; the material of the metal electrode thin film is any one of gold, silver, or aluminum.

7. An organic artificial synaptic transistor pressure sensor array, characterized in that, The pressure sensor array includes a plurality of organic artificial synaptic transistor pressure sensors described in any one of claims 1 to 6 arranged in an array; the pressure sensor array contains at least 4 groups of source-drain electrodes.

8. The preparation method of the organic artificial synaptic transistor pressure sensor based on the suspension structure according to any one of claims 1 to 6, characterized in that, The preparation method includes: (1) Obtain a flexible substrate and fabricate source-drain electrodes on the flexible substrate; (2) On the left and right edges of the flexible substrate, fabricate support layers respectively; (3) Obtain a flexible gate and fabricate a laminated structure of a polyelectrolyte dielectric layer and a dielectric passivation layer on the flexible gate; (4) On the dielectric passivation layer, fabricate an organic semiconductor layer; (5) Orient the suspended structure composed of the flexible gate, the polyelectrolyte dielectric layer, the dielectric passivation layer, and the organic semiconductor layer towards the flexible substrate with source-drain electrodes deposited on the surface, and fix it on the two support layers to form an air gap between the organic semiconductor layer, the support layer, the source-drain electrodes, and the flexible substrate, thus fabricating the organic artificial synaptic transistor pressure sensor based on the suspended structure.

9. The preparation method according to claim 8, characterized in that, In step (1), a vacuum evaporation coating technique is used to deposit interdigital source-drain electrodes on the flexible substrate through a patterned mask. In step (2), a material for support is attached to the left and right edges of the flexible substrate to form the support layer; the height of the air gap is controlled by controlling the height of the support layer. In step (3), the polyelectrolyte dielectric layer is fabricated on the flexible gate by a solution spin-coating method combined with a low-temperature annealing treatment; the dielectric passivation layer is fabricated on the polyelectrolyte dielectric layer by a solution spin-coating method combined with a photocuring crosslinking process. In step (4), the organic semiconductor layer is fabricated on the dielectric passivation layer by a solution spin-coating method.

10. Application of the organic artificial synaptic transistor pressure sensor described in any one of claims 1 to 6 or the organic artificial synaptic transistor pressure sensor array described in claim 7 in neuromorphic technologies such as biological synaptic behavior simulation, intelligent touch recognition of Braille characters, etc., and in fields such as tactile imaging, electrical equipment monitoring, integrated sensing and computing intelligent terminals, and human-computer interaction.

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