A flexible active myoelectric electrode array structure and method of making the same

Abstract

The application discloses a preparation method of a flexible active myoelectric electrode array structure and relates to the field of flexible electronics and active electrode preparation; the structure comprises: a plurality of active electrodes; the plurality of active electrodes are arranged in a horizontal-longitudinal matrix mode; each active electrode comprises: a flexible substrate and an active flexible amplification electrode arranged on the flexible substrate; the active flexible amplification electrode comprises an electrode and a common-source amplification circuit; the electrode and the common-source amplification circuit are in one-to-one correspondence; the electrode and the common-source amplification circuit are connected; the structure realizes synchronous collection of surface myoelectric signals by multiple channels, the flexible substrate enhances the wearability of the electrode, the differential structure, that is, the common-source amplification circuit can improve the interference of common-mode signals, reduce the introduction of noise, improve the signal-to-noise ratio of myoelectric signals, and reduce signal crosstalk between different channels.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flexible electronics and active electrode preparation, in particular to a flexible active myoelectric electrode array structure and a preparation method thereof. BACKGROUND

[0002] In recent years, surface myoelectric signal research has attracted much attention. Due to the weak characteristics of surface myoelectric signals, there are great challenges in the acquisition process, such as how to reduce the channel signal crosstalk between multi-channel electrode arrays, improve the signal-to-noise ratio of the acquired signal, and the difficulty of portable wearing of the electrode, etc. Therefore, it is of great significance to prepare an active flexible electrode array for collecting surface myoelectric signals.

[0003] In the study of surface myoelectric signals, the traditional passive electrode is accompanied by an increase in the number of channels, and the increase in the number of power lines used will cause signal crosstalk problems between different channels, resulting in serious damage to the authenticity and completeness of the myoelectric signal acquisition. Therefore, by introducing an active circuit integrated with a passive electrode, by connecting a hard board-level circuit to the passive electrode, the signal crosstalk problem between different channels can be reduced to a certain extent.

[0004] In recent years, with the development of flexible thin film electronics, active circuits can be developed on ultra-thin substrates. Due to the high field effect mobility characteristics of thin film transistors (TFT), active circuits can work quickly and effectively reduce the number of wires to improve the spatial resolution of the entire device, allowing the device to have scalable design and signal preprocessing functions. This research brings new ideas for the development of active electrodes. Thin film transistors can be directly integrated into passive electrodes to form active electrodes to replace the previous hard plate active electrodes, which not only solves the signal crosstalk problem caused by the power line problem of traditional passive electrode arrays, but also solves the motion artifacts caused by the active electrode acquisition of hard plate circuits and meets the wearable nature and other advantages. However, the difficulty of wearable nature is increased, and the possibility of introducing noise in the signal acquisition process is increased, which affects the completeness of the signal acquisition. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a flexible active myoelectric electrode array structure, which can improve the signal-to-noise ratio and reduce the signal crosstalk between different channels.

[0006] To achieve the above purpose, the present application provides the following scheme:

[0007] A flexible active myoelectric electrode array structure, the structure comprising: a plurality of active electrodes; the plurality of active electrodes are arranged in a horizontal and vertical matrix; each active electrode comprises: a flexible substrate and an active flexible amplification electrode disposed on the flexible substrate;

[0008] The active flexible amplification electrode comprises electrodes and common-source amplification circuits; the electrodes and the common-source amplification circuits are in one-to-one correspondence; and the electrodes and the common-source amplification circuits are connected.

[0009] Optionally, the common-source amplification circuit comprises a first amplification tube, a second amplification tube, a first load tube, a second load tube, a bias tube and an AC-DC coupling circuit.

[0010] The source electrode of the bias tube is grounded; the gate electrode of the bias tube is connected with a bias voltage; and the drain electrode of the bias tube is connected with the source electrode of the first amplification tube and the source electrode of the second amplification tube, respectively.

[0011] The drain electrode of the first amplification tube is connected with the positive electrode of an output voltage and the source electrode of the first load tube, respectively; and the gate electrode of the first amplification tube is connected with the AC-DC coupling circuit.

[0012] The drain electrode of the second amplification tube is connected with the negative electrode of the output voltage and the source electrode of the second load tube, respectively; and the gate electrode of the second amplification tube is connected with the AC-DC coupling circuit.

[0013] The gate electrode of the first load tube, the drain electrode of the first load tube, the drain electrode of the second load tube and the gate electrode of the second load tube are connected with a first external power supply.

[0014] Optionally, the AC-DC coupling circuit comprises a first integrated capacitor, a second integrated capacitor, a first integrated resistor and a second integrated resistor.

[0015] One end of the first integrated capacitor is connected with the electrode; and the other end of the first integrated capacitor is connected with the gate electrode of the first amplification tube and one end of the first integrated resistor, respectively.

[0016] The other end of the first integrated resistor is connected with a second external power supply.

[0017] One end of the second integrated capacitor is connected with the electrode; and the other end of the second integrated capacitor is connected with the gate electrode of the second amplification tube and one end of the second integrated resistor, respectively.

[0018] The other end of the second integrated resistor is connected with the second external power supply.

[0019] Optionally, the electrode is in a cylindrical shape, and the midline distance between every two adjacent electrodes is 6 mm.

[0020] Optionally, the diameter of the electrode is 5 mm.

[0021] A preparation method of a flexible active myoelectric electrode array structure, the preparation method being used for preparing the flexible active myoelectric electrode array structure, and the preparation method comprising:

[0022] A buffer layer is formed on a substrate by a plasma chemical vapor deposition process, and the buffer layer is used as a flexible substrate;

[0023] A gate layer and a capacitor lower plate are formed at a set position on the flexible substrate by a magnetron sputtering process; the gate layer includes a load tube gate layer, an amplification tube gate layer, and a bias tube gate layer;

[0024] An insulating layer is formed above the gate layer and the capacitor lower plate by a plasma enhanced chemical vapor deposition process;

[0025] An active layer is formed on the insulating layer by a magnetron sputtering process; the active layer is composed of a metal oxide, and the position of the active layer corresponds to the position of the gate layer;

[0026] A silicon oxide layer is grown as an etching layer above the active layer by a plasma enhanced chemical vapor deposition process;

[0027] Etching is performed on the etching layer according to a set requirement by a dry etching method, to obtain an etching region;

[0028] An SD source-drain electrode layer is formed on the etching region by a magnetron sputtering process; the SD source-drain electrode layer includes a source electrode, a drain electrode, a resistor, and a capacitor;

[0029] A protective layer is grown on the SD source-drain electrode layer by a plasma enhanced chemical vapor deposition process; the protective layer is composed of silicon nitride and silicon oxide;

[0030] After etching is performed on the protective layer according to a set position by a magnetron sputtering process, a first electrode layer is grown at a position corresponding to the etching; the first electrode layer is used as a lower substrate of an electrode element; the electrode element includes a first external power supply end, a second external power supply end, a bias voltage end, a ground end, an output voltage end, and an electrode;

[0031] A copper film is grown on the first electrode layer by an evaporation process, and a second electrode layer is obtained by processing using a photolithography development process; the second electrode layer is used as an upper substrate of the electrode element;

[0032] An electrode protective layer is grown above the second electrode layer by a plasma enhanced chemical vapor deposition process, and the electrode element is etched based on silicon nitride by a dry etching process, to obtain an active electrode;

[0033] A plurality of the active electrodes are arranged in a horizontal and vertical matrix, to obtain a flexible active myoelectric electrode array structure.

[0034] Optionally, the preparation method further includes:

[0035] Spin polyimide on the glass substrate, and fix the polyimide on the glass substrate through an annealing process to obtain the substrate.

[0036] Optionally, before arranging the plurality of active electrodes in a horizontal and vertical matrix to obtain the flexible active myoelectric electrode array structure, the method comprises:

[0037] Peeling the active electrode from the glass substrate and completing the fixation.

[0038] According to the specific embodiments of the present application, the following technical effects are provided:

[0039] The application discloses a preparation method of a flexible active myoelectric electrode array structure, which comprises: a plurality of active electrodes; the plurality of active electrodes are arranged in a horizontal and vertical matrix; each active electrode comprises: a flexible substrate and an active flexible amplification electrode arranged on the flexible substrate; the active flexible amplification electrode comprises an electrode and a common-source amplification circuit; the electrode and the common-source amplification circuit are in one-to-one correspondence; the electrode and the common-source amplification circuit are connected; the method realizes synchronous acquisition of surface myoelectric signals by a plurality of channels, enhances the wearable property of the electrode by the flexible substrate, improves the interference on common-mode signals and reduces the introduction of noise and improves the signal-to-noise ratio of myoelectric signals by using the differential structure, i.e., the common-source amplification circuit, and reduces signal crosstalk between different channels. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0041] Figure 1 It is a mask pattern diagram of an 8*8 electrode array in the embodiment of the present application.

[0042] Figure 2 It is a physical display diagram of the flexible active myoelectric electrode array structure in the embodiment of the present application.

[0043] Figure 3 It is a bending display diagram of the flexible active myoelectric electrode array structure in the embodiment of the present application.

[0044] Figure 4 It is a common-source amplification electrode circuit schematic diagram in the embodiment of the present application.

[0045] Figure 5 It is a film layer schematic diagram in the embodiment of the present application.

[0046] Figure 6 It is a process flow preparation diagram in the embodiment of the present application.

[0047] Figure 7 The test schematic diagram of the transfer characteristic curve of the randomly selected part of the thin film transistor in the embodiment of the present application is shown in the figure.

[0048] Figure 8 The test schematic diagram of the inverter result of the common source amplification circuit constructed in the embodiment of the present application is shown in the figure.

[0049] Figure 9 The test schematic diagram of the transfer characteristic curve of the randomly selected part of the thin film transistor in the embodiment of the present application is shown in the figure.

[0050] Figure 10 The test schematic diagram of the inverter result of the common source amplification circuit constructed in the embodiment of the present application is shown in the figure.

[0051] Symbol explanation:

[0052] The first amplification tube-T1, the second amplification tube-T3, the first load tube-T2, the second load tube-T4, the bias tube-T5, the first integrated capacitor-C1, the second integrated capacitor-C2, the first integrated resistor-R1, the second integrated resistor-R2, the first external power supply-V D , the second external power supply-V G . DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0054] The purpose of the present application is to provide a preparation method of a flexible active myoelectric electrode array structure, aiming to improve the signal-to-noise ratio and reduce the signal crosstalk between different channels.

[0055] In order to make the above-mentioned purposes, characteristics and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0056] Embodiment 1

[0057] The flexible active myoelectric electrode array structure provided by the embodiment of the present application comprises: a plurality of active electrodes; the plurality of active electrodes are arranged in a horizontal and vertical matrix; each active electrode comprises: a flexible substrate and an active flexible amplification electrode arranged on the flexible substrate.

[0058] The active flexible amplification electrode comprises an electrode and a common source amplification circuit; the electrode and the common source amplification circuit are one-to-one corresponding; the electrode and the common source amplification circuit are connected.

[0059] Specifically, the common-source amplification circuit comprises a first amplification tube T1, a second amplification tube T3, a first load tube T2, a second load tube T4, a bias tube T5, and an AC-DC coupling circuit.

[0060] The source of the bias tube T5 is grounded; the gate of the bias tube T5 is connected with a bias voltage; and the drain of the bias tube T5 is connected with the source of the first amplification tube T1 and the source of the second amplification tube T3 respectively.

[0061] The drain of the first amplification tube T1 is connected with the positive electrode of an output voltage and the source of the first load tube T2 respectively; and the gate of the first amplification tube T1 is connected with the AC-DC coupling circuit.

[0062] The drain of the second amplification tube T3 is connected with the negative electrode of the output voltage and the source of the second load tube T4 respectively; and the gate of the second amplification tube T3 is connected with the AC-DC coupling circuit.

[0063] The gate of the first load tube T2, the drain of the first load tube T2, the drain of the second load tube T4, and the gate of the second load tube T4 are all connected with a first external power supply V D .

[0064] The AC-DC coupling circuit comprises a first integrated capacitor C1, a second integrated capacitor C2, a first integrated resistor R1, and a second integrated resistor R2.

[0065] One end of the first integrated capacitor C1 is connected with an electrode; and the other end of the first integrated capacitor C1 is connected with the gate of the first amplification tube T1 and one end of the first integrated resistor R1 respectively.

[0066] The other end of the first integrated resistor R1 is connected with a second external power supply V G .

[0067] One end of the second integrated capacitor C2 is connected with the electrode; the other end of the second integrated capacitor C2 is connected with the gate of the second amplification tube T3 and one end of the second integrated resistor R2 respectively; and the other end of the second integrated resistor R2 is connected with the second external power supply V G .

[0068] In an embodiment, the electrode is in a cylindrical shape, and the centerline distance between every two adjacent electrodes is 6 mm. The diameter of the electrode is 5 mm.

[0069] The high-density active flexible electrode array, i.e., the flexible active myoelectric electrode array structure mainly comprises a plurality of active electrodes arranged in rows and columns, wherein the active electrodes are arranged in a matrix of 8x8, and each active electrode comprises an active flexible amplification electrode; and each active flexible amplification electrode is composed of an electrode and a common-source amplification circuit.

[0070] The active electrode is an integrated structure layout, and the active electrode module is constructed based on an IGZO metal oxide thin film transistor, and the electrode and the common source amplification circuit are integrated on a flexible substrate, that is, a flexible substrate.

[0071] The electrode shape selected in the application is a cylindrical shape, the electrode diameter is 5mm, and the center line spacing between two adjacent electrodes is 6mm.

[0072] The flexible substrate material is selected to prepare a polyimide film. The aspect ratio of the array structure is 8x8, which is a 64-channel active flexible electrode.

[0073] In practical applications, the common source amplification circuit structure is a differential common source amplification circuit, which involves devices including two amplifying tubes, two load tubes, one biasing tube, two AC-DC integrated capacitors, and two AC-DC integrated resistors. The amplifying tubes, load tubes, and biasing tube are all thin film transistors, and the AC-DC integrated resistors and AC-DC integrated capacitors are connected in parallel to form an AC-DC coupling circuit. The source of the load tube is connected to the drain of the amplifying tube, which is the output end of the differential common source amplification circuit. The gate of the amplifying tube is connected to one end of the AC integrated capacitor of the coupling circuit. The sources of the two amplifying tubes in the differential circuit are connected and connected to the drain of the biasing transistor. The source of the biasing transistor is grounded, and a given input bias voltage is applied to the gate of the biasing transistor. The drain and gate of the load tube are both connected to an external power supply for power supply. The coupling circuit is connected to the other end of the AC-DC integrated capacitor and the resistor, and one end of the resistor is connected to an external power supply.

[0074] Example 2

[0075] The application provides a preparation method of a flexible active myoelectric electrode array structure, which is used for preparing the flexible active myoelectric electrode array structure in the embodiment 1. The preparation method comprises the following steps:

[0076] A layer of silicon nitride is grown on the substrate by a plasma chemical vapor deposition process to form a buffer layer, and the buffer layer is used as a flexible substrate.

[0077] A gate layer and a capacitor lower plate are generated at a set position on the flexible substrate by a magnetron sputtering process. The gate layer comprises a load tube gate layer, an amplifying tube gate layer, and a biasing tube gate layer.

[0078] An insulating layer is generated above the gate layer and the capacitor lower plate by a plasma enhanced chemical vapor deposition process.

[0079] An active layer is generated on the insulating layer by a magnetron sputtering process. The active layer is composed of metal oxide, and the position of the active layer corresponds to the position of the gate layer.

[0080] A silicon oxide layer is grown as an etching layer above the active layer by a plasma enhanced chemical vapor deposition process.

[0081] An etching region is obtained by etching the etching layer according to a set requirement by a dry etching method.

[0082] An SD source-drain electrode layer is generated on the etching region by a magnetron sputtering process; the SD source-drain electrode layer includes a source electrode, a drain electrode, a resistor, and a capacitor.

[0083] A protective layer is grown on the SD source-drain electrode layer by a plasma enhanced chemical vapor deposition process; the protective layer is composed of silicon nitride and silicon oxide.

[0084] After etching at a set position on the protective layer by a magnetron sputtering process, a first electrode layer is grown at the etched position; the first electrode layer serves as a lower substrate of an electrode element; the electrode element includes a first external power supply end, a second external power supply end, a bias voltage end, a ground end, an output voltage end, and an electrode.

[0085] A copper film is grown on the first electrode layer by an evaporation process, and a second electrode layer is obtained by processing using a photolithography development process; the second electrode layer serves as an upper substrate of the electrode element.

[0086] An electrode protective layer is grown above the second electrode layer by a plasma enhanced chemical vapor deposition process, and the electrode element is etched based on silicon nitride by a dry etching process, to obtain an active electrode. That is, the various layers prepared and grown on the flexible substrate together constitute an active flexible amplification electrode. In the active flexible amplification electrode, the part of the electrode is a common-source amplification circuit mentioned above. The load tube gate layer, the amplification tube gate layer, and the bias tube gate layer each correspond to the first amplification tube, the second amplification tube, the first load tube, the second load tube, and the bias tube included in the common-source amplification circuit.

[0087] The multiple active electrodes are arranged in a horizontal and vertical matrix to obtain a flexible active electromyography electrode array structure.

[0088] In an embodiment, the preparation method further includes:

[0089] A polyimide is spin-coated on a glass substrate, and the polyimide on the glass substrate is fixed by an annealing process to obtain a substrate.

[0090] As an optional embodiment, before the multiple active electrodes are arranged in a horizontal and vertical matrix to obtain a flexible active electromyography electrode array structure, the following steps are included:

[0091] The active electrode is peeled off from the glass substrate and fixed.

[0092] In practical applications, the prepared array structure selects a 11-layer structure stack, including a PI substrate layer isolation buffer layer, that is, a silicon nitride layer is grown on the substrate to form a buffer layer, and the buffer layer is used as a flexible substrate, a gate layer, an insulating layer, an active layer, an ES etching layer, an SD source-drain electrode layer, a protective layer, a first electrode layer, a second electrode layer, and an electrode protective layer.

[0093] The specific preparation steps include:

[0094] Step 1, preparation of a flexible substrate.

[0095] (1) Select a glass substrate as the initial substrate, and clean the glass plate.

[0096] (2) Spin-coat polyimide on the glass substrate, and fix the polyimide on the glass substrate through an annealing step.

[0097] (3) Use the cvd plasma chemical vapor deposition process to grow a silicon nitride layer on the annealed substrate to form a buffer layer, and use it as a flexible substrate.

[0098] Step 2, preparation of the SD source-drain electrode layer:

[0099] (1) First, use a magnetron sputtering pvd process instrument to prepare the gate layer and the lower plate of the capacitor on the flexible substrate.

[0100] (2) Use a plasma-enhanced chemical vapor deposition process to prepare an insulating layer on the gate layer, and use a magnetron sputtering process to prepare an active layer metal oxide IGZO on the pvd.

[0101] (3) Grow a layer of silicon oxide as an etching layer on the basis of the active layer by a plasma-enhanced chemical vapor deposition process, and complete etching by a dry etching method.

[0102] (4) Prepare the SD source-drain electrode layer by a magnetron sputtering process on the pvd.

[0103] Step 3, specific preparation of the active electrode includes:

[0104] (1) After completing the SD source-drain electrode layer, grow a layer of silicon nitride and silicon oxide using a plasma-enhanced chemical vapor deposition process to obtain a protective layer; the protective layer serves to isolate and protect the electrical performance of the active circuit from being affected.

[0105] (2) Grow a layer of Mo electrode as the first electrode layer on the protective layer using a pvd magnetron sputtering process, which can enhance the adhesion of the second layer of copper (gold) electrode to other layers, and solve the problem of Cu oxidation and diffusion when Cu contacts silicon oxide.

[0106] (3) Using evaporation process to grow a copper film on the Mo electrode layer, that is, the first electrode layer, and using photoetching process to complete the preparation of the electrode substrate to obtain the second electrode layer.

[0107] (4) Using ion enhanced chemical vapor deposition process to grow a layer of silicon nitride on the second electrode layer as a protective layer of the two-stage electrode layer, that is, the electrode protective layer, to prevent the electrode layer from being affected by the environment and its electrode performance.

[0108] (5) Adding a layer of silicon nitride on the electrode protective layer through dry etching process to etch the electrode to obtain the active electrode.

[0109] (6) Peeling the active electrode from the glass sheet and completing the preparation of the flexible active myoelectric electrode array structure.

[0110] The present application mainly adopts a differential common-source amplification circuit under the condition that the common-source amplification circuit and the electrode are integrated on a flexible substrate, designs an amplification circuit suitable for collecting surface myoelectric signals by changing the size of the device, draws a mask plate of the active electrode array through autoCAD software and optimizes the experimental process to complete the preparation, and the prepared active flexible electrode array can realize local amplification and collection of surface myoelectric signals and improve the signal-to-noise ratio.

[0111] In order to solve the problem of signal crosstalk between channels in the surface myoelectric signal collection of the multi-channel electrode, the present application proposes to integrate the passive electrode and the amplification circuit constructed by the thin film transistor, that is, the active flexible amplification electrode, on the flexible substrate to improve the integration degree of the collection system, reduce the interference of electromagnetic waves received by the signal in the transmission process, and configure an amplification circuit for each passive electrode to improve the signal collection quality. Figure 1 As shown in the drawing, 64 active electrode units are integrated on the flexible material. Figure 2 A flexible active myoelectric electrode array structure.

[0112] Through the research on the electrode, it is found that the circular electrode in the direction perpendicular to the muscle surface fiber can appropriately reduce the impedance between the skin and the electrode in the signal collection, and appropriately increasing the spacing of the electrode can reduce the crosstalk problem of the collected signals between different channels.

[0113] The flexible substrate material is selected as a PI film. The PI film is an organic polymer film, which is resistant to hydrolysis, high temperature and corrosion, and has good biocompatibility and insulation. Therefore, polyimide is selected as a base material to make a substrate. Compared with an organic thin film transistor, the IGZO thin film transistor has higher field effect mobility, low temperature manufacturing, repeated bending for flexible devices, low noise, good stability for mass production and other excellent characteristics. Therefore, the IGZO oxide thin film transistor is preferably selected as a basic device of an amplification circuit. Figure 3 A bending display diagram of the flexible active myoelectric electrode array structure.

[0114] The electrode material is copper, gold and other metals. Copper, gold and other metals have stable chemical properties, high conductivity and other advantages, and have the characteristics of simultaneously compatible conductivity and bending rate in flexible electronics. In addition, the resistivity changes little in bending. For the thin film transistor, Mo and Al are selected as the gate material, IGZO is selected as the active layer material, silicon oxide is selected as the insulating layer, and Mo, Al and Mo are selected as the sandwich structure of the SD drain-source electrode layer material. The electrode layer adopts the Mo and Cu structure. Al / Cu and SiO2 contact will cause problems such as Al / Cu contact surface oxidation and diffusion. In order to reduce the contact oxidation problem between the influences, Mo is introduced to separate Al / Cu and SiO2 in a double-layer or triple-layer structure.

[0115] The selected common-source amplification circuit structure is shown in Figure 4 The size ratio of the bias transistor, the load transistor and the amplification transistor is adjusted to design a common-source amplification circuit that can realize gain amplification of the signal and realize the whole frequency band process of the surface myoelectric signal (the frequency band range of the myoelectric signal is 20Hz-500Hz) in the frequency band range of at least 20Hz-500Hz. The source of the load transistor and the drain of the amplification transistor are connected as the output end of the common-source amplification circuit, and the gate of the amplification transistor is connected with one end of the alternating current integration capacitor of the coupling circuit. The sources of the two amplification transistors are connected and connected with the drain of the bias transistor. The source of the bias transistor is grounded, and the gate of the bias transistor is given an input bias voltage. The drain and the gate of the load transistor are connected with an external power supply for power supply. The other end of the alternating current integration capacitor of the coupling circuit is connected with a resistor, and one end of the resistor is connected with an external power supply. Figure 4 The yellow area in the figure can be an electrode or an electrode and a bracelet.

[0116] The film layer stack structure of the array structure is shown in Figure 5As shown in the PI substrate layer, the main content is completed on the glass substrate spin coating a layer of PI film for subsequent device preparation, after the completion of the application in the field of flexible electronics. The main purpose of the buffer layer is to make the PI film surface smooth, reduce the subsequent thin film transistor in the preparation process. In the gate layer to complete the amplifier and load tube transistor bottom gate structure and AC coupling capacitor AC coupling resistance of the lower plate, before the preparation of the active layer, the silicon oxide and silicon nitride are used as the insulating layer, and then the active layer IGZO is grown on the basis of the insulating layer. The purpose of the sixth etching layer is to ensure the communication between the active layer and the SD drain-source electrode layer through dry etching process. The drain-source electrode of the amplifier and the load tube is prepared in the SD drain-source electrode layer. A layer of water and oxygen isolation layer is prepared on the basis of the SD drain-source electrode layer to protect the circuit structure. An electrode layer is prepared. Since the adhesion of Cu / Au and SiO2 in contact is not firm, a layer of Mo is prepared under the Cu / Au layer to enhance the surface contact and solve the problem of Cu oxidation and diffusion in the contact of Cu and SiO2. Therefore, the upper plate of the electrode layer is prepared, and finally a protective layer is laid on the basis of the electrode layer to encapsulate the part except the test electrode, and the surface electromyogram signal of the designed electrode array is collected.

[0117] Example 3

[0118] The specific preparation process flow of the array structure used in this embodiment is shown in Figure 6 The size of the thin film transistor used is 10um wide and 50um long for the bias transistor, 10um / 50um for the load transistor, and 200um / 10um for the amplifier transistor. Since the common-source amplifier electrode circuit is a symmetrical structure, Figure 6 The structure in the preparation process is selected to show the results.

[0119] First, the preparation of the flexible substrate and the buffer protection layer.

[0120] (1) Select a glass substrate with clean surface and no dust, and spin PI slurry. In order to get a flexible substrate with a film thickness of 10um, set the working speed of the spin coater to 500RPM(30s). After the spin coating is completed, the substrate is placed in the annealing furnace for curing treatment. Adjust the annealing furnace temperature(time) respectively: 100℃(40min), 150℃(40min), 200℃(60min), 250℃(40min), 350℃(15min), and anneal, then naturally cool to room temperature. The purpose of annealing is to improve the thermal stability of the PI film prepared in a short time in high temperature environment. By changing the molecular arrangement and crystallinity of the polyimide film in high temperature environment, the strength, hardness and wear resistance of the film are improved.

[0121] (2) In order to reduce the influence of the uneven surface of the substrate in the subsequent preparation of the thin film transistor, a 200nm-thick silicon nitride buffer protection layer is grown on the basis of the PI film layer by chemical vapor deposition.

[0122] Second step, preparation of the gate structure.

[0123] (1) Place the substrate with the grown buffer layer in the surface cleaning machine to clean the surface and ensure that it is clean and free of dust, and then perform a heating and drying treatment.

[0124] (2) Use a magnetron sputtering pvd process instrument to prepare the gate layer of the cleaned substrate by magnetron sputtering process. The gate layer of the thin film transistor, the lower plate of the alternating current integrated capacitor, and the layout of the port traces of a plurality of active electrodes are grown by sputtering process, and the corresponding film thicknesses are 200nm of Al and 80nm of Mo (by using a magnetron sputtering equipment pvd, CME-200E, Japan, at room temperature).

[0125] (3) After the magnetron sputtering step, adjust the rotation conditions on the photoresist spin coating table to 1000RPM for 30s to spin coat photoresist. After the spin coating is completed, move to the pre-baking table and set the pre-baking temperature to 125℃ for 120s. After cooling, match the mask plate provided with the photoetching machine and adjust the exposure time of the photoetching machine to 8s to complete the exposure treatment.

[0126] (4) Move the exposed substrate to the yellow light area and perform the development process treatment, control the development time to be 75s, and complete the cleaning in the sink. After cleaning, use the post-baking equipment to adjust the temperature to 135℃ and post-bake for 150s. Observe the development condition under a microscope.

[0127] (5) After the exposure and development are correct, perform wet etching on the substrate, and etch Mo and Al in the order of room temperature molybdenum aluminum etching solution, and obtain the final circuit pattern drawn by the gate layer. Complete cleaning and move to the microscope for observation.

[0128] Third step, preparation of the insulating layer and the active layer.

[0129] (1) On the basis of the prepared gate layer, a 250 nm thick silicon nitride film and a 100 nm thick silicon oxide film are grown as the main material of the insulating layer by plasma chemical vapor deposition (PECVD) process (Plasma Enhanced Chemical Vapor Deposition is a technology for thin film growth. The basic principles of using PECVD to deposit silicon nitride and silicon oxide include: first, plasma generation: usually using radio frequency power or microwave power to provide energy to discharge gas into plasma. In this plasma, the electrons in the gas molecules are excited to high energy levels to form charged particles. The second is the precursor gas: introduce appropriate precursor gas containing silicon, oxygen, nitrogen elements. The third is that the precursor gas is excited by plasma and chemically reacts to form a thin film. For silicon nitride, a combination of silicon source and nitrogen source is used to produce silicon nitride deposition. For silicon oxide, a combination of silicon source and oxygen source can be used to produce silicon oxide deposition. The model of the equipment used is: Plasma Enhanced Chemical Vapor Deposition.

[0130] (2) On the basis of the insulating layer, a 40 nm thick IGZO film is grown by magnetron sputtering (PVD) process technology, and the processes of (3) and (4) in the second step are repeated.

[0131] (3) The substrate on which IGZO is grown is patterned by wet etching, and the substrate is placed in a container containing oxalic acid at room temperature for 50 s to complete the etching process, and then washed with water to obtain the final pattern of the active layer.

[0132] (4) The glass plate is placed in an annealing furnace, and the annealing conditions are set as follows: room temperature to 220°C for 30 minutes, and 220°C for one hour. After annealing, the glass plate is cleaned to remove impurities attached to the surface. The main purpose of annealing is to expose the thin film of the active layer to a high temperature environment for a short time, which can rearrange the crystal structure of the active layer material and reduce defects, thereby improving the conductivity of the transistor. (2) Annealing can increase the mobility of the transistor and reduce the threshold voltage.

[0133] Fourth step, etching layer preparation.

[0134] (1) On the basis of the completed active layer, a 120 nm thick silicon oxide film is grown as a barrier layer by chemical vapor deposition process, and the process flow of (3) and (4) in the second step of gate structure preparation is repeated.

[0135] (2) The developed glass plate is subjected to dry etching process by setting the dry etching machine time to 100 s.

[0136] (3) After dry etching, the glass plate is placed in a water bath with a temperature of 60°C and a positive photoresist stripping solution at 55°C, and scrubbed for 3 minutes to complete the cleaning.

[0137] Fifth step: SD drain-source electrode layer preparation:

[0138] (1) After etching, a thin film transistor SD drain-source electrode layer is grown on the glass plate by sputtering process, with Mo film thickness of 30 nm and Al film thickness of 200 nm and Mo film thickness of 80 nm.

[0139] (2) Repeat the process flow of (3), (4) and (5) in the second step.

[0140] Sixth step: preparation of protective layer.

[0141] (1) After the SD electrode layer has been prepared, a layer of silicon oxide with a thickness of 330 nm and a layer of silicon oxide with a thickness of 50 nm as a barrier layer are grown by chemical vapor deposition process on the glass plate, and the process flow of (3) and (4) in the second step and (2) and (3) in the fourth step is repeated, and the dry etching time is adjusted to 320 seconds, and the positive photoresist stripping solution is scrubbed for 10 minutes.

[0142] Seventh step: preparation of first electrode layer and second electrode layer.

[0143] (1) In order to enhance the adhesion of copper / gold electrode to other layers and solve the problem of Cu oxidation and diffusion caused by Cu contact with SiO2, Mo is added to solve the problem. A layer of Mo electrode with a thickness of 100 nm is sputtered by magnetron sputtering method after the barrier layer is prepared. Then the preparation is completed according to the steps (3) and (4) in the second step.

[0144] (2) Then the glass sheet with Mo electrode prepared is placed in an evaporation machine, and the evaporation process parameters are adjusted to power 75 W and time one hour to evaporate a copper layer with a thickness of 250 nm, and the process flow of (3) and (4) in the second step is repeated.

[0145] (3) After development, the glass plate is subjected to wet etching, and the designed circuit shape is etched by molybdenum aluminum etching solution.

[0146] Eighth step: preparation of encapsulation layer.

[0147] (1) After the electrode layer has been prepared, a layer of silicon nitride with a thickness of 300 nm is grown by chemical vapor deposition process on the glass plate as an encapsulation protective layer, that is, an electrode protective layer, and the process flow of (3) and (4) in the second step and (2) and (3) in the fourth step is repeated.

[0148] Ninth step: encapsulation and fixation.

[0149] The prepared active electrode is peeled off from the glass plate, and is fixed on a flexible substrate to complete packaging, so as to facilitate subsequent research and exploration on flexible wearable electrodes and the like, and finally the preparation is completed.

[0150] Example 4

[0151] The same process parameters in Example 3 are adopted, but the size ratio of the thin film transistor is changed: the size W / L of the bias transistor is 10 / 50 um, the size W / L of the load transistor is 10 / 50 um, and the size W / L of the amplification transistor is 100 / 10 um.

[0152] Through the design based on the front-end amplification circuit and the construction of the mask plate of the layout design, combined with the photoetching and developing process and the thin film transistor preparation process, the preparation is completed through the above nine steps. In order to verify the outstanding advantages in the experimental process and the circuit size, some thin film transistors in Example 3 and Example 4 are randomly selected for electrical performance test. The transfer characteristics of the device are tested as shown in Figure 7 and Figure 9 The electrical parameters of the transfer characteristic curves are extracted as shown in Tables 1 and 2. It can be seen that the thin film transistor with W / L of 200 / 10 um has higher mobility and lower threshold voltage under the corresponding process.

[0153] Table 1: Electrical parameter extraction results of the transfer characteristic curves in Example 3

[0154] Switching ratio SS V th ]]> um Slope Point 1 10 8 ]] 0.348 1.91 6.67 8.17 Point 3 10 9 ]] 0.352 1.93 6.65 8.16 Point 5 10 9 ]] 0.347 1.89 6.83 8.27 Point 8 10 9 ]] 0.345 1.9 6.67 8.17 Point 10 10 9 ]] 0.349 1.91 6.52 8.08

[0155] Table 2: Electrical parameter extraction results of the transfer characteristic curves in Example 4

[0156] Switching ratio SS V th ]]> um Slope Point 1 10 8 ]] 0.359 2.15 4.74 4.87 Point 2 10 8 ]] 0.361 2.11 4.78 4.89 Point 6 10 9 ]] 0.358 2.09 4.92 4.96 Point 7 10 8 ]] 0.351 2.18 4.58 4.79 Point 11 10 8 ]] 0.357 2.15 4.68 4.84

[0157] The inverter tests of the two size designed differential common source amplification circuits are shown in Figure 8 and Figure 10 Through analysis, it can be concluded that the amplification gain in Example 3 is about 7 times, and the gain is 17 dB. The amplification gain in Example 4 is 3.8 times, and the gain is about 12 dB.

[0158] In summary, the array designed by the present application can preliminarily amplify the weak signal by 12 dB-20 dB. By integrating the common source amplification circuit and the electrode on a flexible substrate, a feasible scheme is provided for the wearable electronic field, while the signal loss in the transmission during the collection process is reduced, and the signal-to-noise ratio quality of the electromyographic signal is improved.

[0159] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0160] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the structure and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A flexible active electromyography electrode array structure, characterized in that, The structure includes: multiple active electrodes; the multiple active electrodes are arranged in a horizontal and vertical matrix; each active electrode includes: a flexible substrate and an active flexible amplification electrode disposed on the flexible substrate; The active flexible amplification electrode includes an electrode and a common-source amplification circuit; the electrode and the common-source amplification circuit correspond one-to-one; the electrode and the common-source amplification circuit are connected. The common-source amplifier circuit includes: a first amplifying transistor, a second amplifying transistor, a first load transistor, a second load transistor, a bias transistor, and an AC / DC coupling circuit; The source of the bias transistor is grounded; the gate of the bias transistor is connected to the bias voltage; the drain of the bias transistor is connected to the source of the first amplifier transistor and the source of the second amplifier transistor, respectively. The drain of the first amplifier transistor is connected to the positive terminal of the output voltage and the source of the first load transistor, respectively; the gate of the first amplifier transistor is connected to the AC / DC coupling circuit. The drain of the second amplifier transistor is connected to the negative terminal of the output voltage and the source of the second load transistor, respectively; the gate of the second amplifier transistor is connected to the AC / DC coupling circuit. The gate, drain, drain, and gate of the first load transistor are all connected to the first external power supply. The AC / DC coupling circuit includes: a first integrated capacitor, a second integrated capacitor, a first integrated resistor, and a second integrated resistor; One end of the first integrated capacitor is connected to the electrode; the other end of the first integrated capacitor is connected to the gate of the first amplifier tube and one end of the first integrated resistor, respectively. The other end of the first integrated resistor is connected to the second external power supply; One end of the second integrated capacitor is connected to the electrode; the other end of the second integrated capacitor is connected to the gate of the second amplifier tube and one end of the second integrated resistor, respectively. The other end of the second integrated resistor is connected to the second external power supply.

2. The flexible active electromyography electrode array structure according to claim 1, characterized in that, The electrode is cylindrical in shape, and the distance between the centerlines of any two adjacent electrodes is 6 mm.

3. The flexible active electromyography electrode array structure according to claim 2, characterized in that, The diameter of the electrode is 5 mm.

4. A method for fabricating a flexible active electromyography electrode array structure, characterized in that, The preparation method is used to prepare the flexible active electromyographic electrode array structure according to any one of claims 1-3, and the preparation method includes: A silicon nitride buffer layer is grown on a substrate using plasma chemical vapor deposition, and the buffer layer is used as a flexible substrate. A gate layer and a lower electrode of a capacitor are formed at predetermined positions on the flexible substrate using a magnetron sputtering process; the gate layer includes: a load transistor gate layer, an amplifier transistor gate layer, and a bias transistor gate layer. An insulating layer is formed above the gate layer and the lower electrode of the capacitor using a plasma-enhanced chemical vapor deposition process. An active layer is formed on the insulating layer using a magnetron sputtering process; the active layer is composed of a metal oxide, and the position of the active layer corresponds to the position of the gate layer; A silicon oxide layer is grown as an etching layer above the active layer using a plasma-enhanced chemical vapor deposition process. The etching layer is etched according to the set requirements using a dry etching method to obtain the etched area; An SD source / drain electrode layer is formed on the etched area using a magnetron sputtering process; the SD source / drain electrode layer includes: a source electrode, a drain electrode, a resistor, and a capacitor; A protective layer is grown on the SD drain-source electrode layer using an ion-enhanced chemical vapor deposition process; the protective layer is composed of silicon nitride and silicon oxide. After etching the protective layer at predetermined positions using magnetron sputtering, a first electrode layer is grown at the etched locations. The first electrode layer serves as the lower substrate of the electrode element. The electrode element includes: a first external power supply terminal, a second external power supply terminal, a bias voltage terminal, a ground terminal, an output voltage terminal, and an electrode. A copper film is grown on the first electrode layer using a vapor deposition process, and then processed using a photolithography and development process to obtain the second electrode layer; the second electrode layer serves as the upper substrate of the electrode element. Above the second electrode layer, an electrode protective layer is grown using ion-enhanced chemical vapor deposition, and the electrode element is etched using a dry etching process based on silicon nitride to obtain the active electrode. Multiple active electrodes are arranged in a horizontal and vertical matrix to obtain a flexible active electromyography electrode array structure.

5. The method for fabricating the flexible active electromyography electrode array structure according to claim 4, characterized in that, The preparation method further includes: Polyimide is spin-coated onto a glass substrate, and the polyimide on the glass substrate is fixed by an annealing process to obtain the substrate.

6. The method for fabricating the flexible active electromyography electrode array structure according to claim 5, characterized in that, Before arranging multiple active electrodes in a horizontal and vertical matrix to obtain a flexible active electromyography electrode array structure, the following steps are included: The active electrode is peeled off from the glass substrate and then fixed.

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