Multi-mode biological signal sensor and preparation method thereof

Abstract

The invention provides a multi-modal biological signal sensor and a preparation method thereof, and relates to the technical field of multi-modal biological signal sensors, the method comprises a plurality of active electrode units, the plurality of active electrode units are arranged vertically and horizontally in a matrix mode to form an active high-density electrode array, and the active high-density electrode array is connected with the multi-modal biological signal sensor. An interdigital structure electrode is arranged at the edge of the active high-density electrode array; the active electrode unit comprises an active amplification circuit and two electrodes, and the active amplification circuit comprises an amplification device, a bias device, a load device and a negative feedback capacitor; the interdigital structure electrode comprises six metal electrode structures which are mutually staggered. The technical problems of signal crosstalk and noise amplification in a high-density array are solved, precise monitoring of tiny muscle activity is achieved through space-time correlation analysis of mechanical-electrical signals, the adopted extensible matrix architecture supports flexible adjustment of the detection density according to application scenes, and the detection accuracy is improved. And the modular design also provides convenience for subsequent function expansion.

Description

Technical Field

[0001] This invention relates to the field of multimodal biosignal sensors and related technologies, and in particular to a multimodal biosignal sensor and its fabrication method. Background Technology

[0002] With the increasing application of electromyography (EMG) signal detection technology in rehabilitation medicine and human-computer interaction, traditional electrode arrays face significant challenges in terms of the accuracy of action intent recognition. Single-modal signals have weak anti-interference capabilities and insufficient information dimensions. Existing solutions mostly rely on a single EMG signal for action recognition, but EMG signals are susceptible to various interference sources: on the one hand, sweat and oil on the skin surface can cause fluctuations in the contact impedance between the electrode and the skin, leading to signal baseline drift and noise superposition; on the other hand, crosstalk from the electrical activity of adjacent muscle groups can confuse the characteristic signals of the target action. Especially in the recognition of complex and delicate movements (such as multi-joint coordinated movements of the fingers), single-modal information is difficult to distinguish the EMG patterns of similar movements, resulting in a recognition accuracy rate generally below 85%, which cannot meet the high-precision requirements of prosthetic finger control, surgical robot operation, and other scenarios. Poor flexibility and insufficient dynamic detection stability are also issues. Traditional rigid electrode arrays often use PCB substrates or metal electrode sheets, which have low conformity to the curved contours of human muscle tissue. In dynamic motion scenarios, electrodes are prone to displacement or detachment, leading to poor contact and a signal acquisition interruption rate of over 20%. Even with flexible substrates, the electrode array density and flexibility are still limited by the fabrication process, preventing adaptive fitting with muscle deformation. This is especially true in joint motion areas, where signal distortion is more severe, affecting the continuity and reliability of movement assessment during rehabilitation training. Low multi-signal integration and high system complexity are also issues. A complete representation of movement intent often requires the fusion of multi-dimensional signals such as electromyography (EMG), posture, and physiological state. Current technologies often employ a combination of discrete sensors and external acquisition modules, with EMG electrodes, inertial measurement units, and physiological sensors deployed independently. This not only increases device size and weight but also presents challenges in simultaneous multi-signal acquisition—differences in sampling frequencies and data transmission delays between different sensors reduce the effectiveness of multimodal fusion algorithms and increase user discomfort and operational complexity. Therefore, designing a multimodal biosignal sensor and its fabrication method is essential. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a multimodal biosignal sensor and its preparation method.

[0004] To achieve the above objectives, the present invention provides the following solution: This invention provides a multimodal biosignal sensor, comprising: multiple active electrode units, wherein the multiple active electrode units are arranged in a matrix to form an active high-density electrode array, the edges of the active high-density electrode array are provided with interdigitated electrodes, and temperature and pressure materials are disposed on the active high-density electrode array and the interdigitated electrodes. The active electrode unit includes an active amplifier circuit and two electrodes. The active amplifier circuit includes an amplifying device, a biasing device, a load device, and a negative feedback capacitor. The interdigitated electrode structure comprises six interlaced metal electrode structures.

[0005] Preferably, the source of the bias device is connected to the gate of the load device and one end of the negative feedback capacitor, respectively. The other end of the negative feedback capacitor is connected to the source of the load device and the drain of the amplifier device, respectively. The connection point of the negative feedback capacitor, the source of the load device, and the drain of the amplifier device is the output terminal of the bootstrap inverter circuit. The gate of the amplifier device is connected to one end of the electrode, the source of the amplifier device is grounded, and the drain of the load device, the gate of the bias device, and the drain of the bias device are all connected to an external power supply.

[0006] Preferably, the amplifying device, the load device, and the biasing device are all thin-film transistors.

[0007] Preferably, the active electrode unit is formed by integrating the electrode and the active amplifier circuit on a flexible substrate using metal oxide thin-film transistor photolithography.

[0008] Preferably, the flexible substrate is a flexible polyimide substrate, and the flexible polyimide substrate includes, from bottom to top, a thin film transistor layer, a metal layer, an insulating layer, another metal layer, an insulating layer, and an electrode layer.

[0009] Preferably, the flexible polyimide substrate includes a polyimide film layer and a buffer layer, wherein the buffer layer includes a silicon nitride film and a silicon dioxide film stacked sequentially from bottom to top.

[0010] Preferably, the thickness of the silicon nitride film is 300-400 nm, and the thickness of the silicon dioxide film is 200-300 nm.

[0011] This invention also provides a method for fabricating a multimodal biosignal sensor, applied to the aforementioned multimodal biosignal sensor, comprising the following steps: The raw materials for the fabrication of amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices, and switching devices in switching circuits are deposited to form an initial substrate; Photoresist is coated onto the initial substrate layer. After the coated photoresist is dried, the initial substrate layer is exposed in conjunction with the first mask to form the exposed initial substrate layer. After developing the exposed initial amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching device layer in the switching circuit, wet etching is performed to form the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching device in the switching circuit. The raw material for depositing an insulating layer on the lower electrode plate of a switching device in an amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching circuit is used to form an insulating layer. The gate metal molybdenum is deposited using PVD for amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices, and switching devices in the switching circuit. Then, the gate metal is patterned through photolithography and etching processes to form the desired gate structure. Using the active layer structure as a mask, an IGZO layer is deposited by CVD, and then the active layer is formed again by photolithography and etching processes; Molybdenum metal is deposited in the source and drain regions, and then photolithography and etching processes are used to form the source and drain metal electrodes, forming the lower plate of the feedback capacitor. Silicon dioxide is deposited by CVD as an insulating layer in the source / drain and gate regions. Contact holes are formed on the insulating layer using photolithography and etching processes; The precursor is annealed to form amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices, and switching devices in switching circuits. The raw materials for preparing the etching layer are chemically deposited onto the active layer to form the initial etching layer; Photoresist is coated onto the initial etched layer. After the coated photoresist is dried, the initial etched layer is exposed with the third mask to form the exposed initial etched layer. After the initial etched layer is exposed, it is developed and then dry etched to reserve gaps between the active layer of the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device and the corresponding SD drain and source, one end of the feedback capacitor, and the interconnection between the gate of the amplifier and the feedback circuit device, thus forming an etched layer. The raw materials for fabricating amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices, and the source and drain electrodes of switching devices in the switching circuit, as well as the lower electrode plate of the feedback capacitor, are magnetron sputtered onto an etched layer. This achieves interconnection between the active layer of the amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices, and the switching devices in the switching circuit and their corresponding SD drain and source electrodes, between the gate of the bias circuit device and the gate of the amplifier circuit device, between the source of the startup circuit device and the drain of the bias circuit device, between the drain of the electrostatic protection circuit device and the source of the switching device in the switching circuit, between the source of the switching device in the switching circuit and the gate of the amplifier circuit device, between the upper electrode plate of the feedback capacitor and the gate of the amplifier circuit device, and between the feedback device and the amplifier circuit device, forming an SD electrode film. Photoresist is coated onto the SD electrode film. After the coated photoresist is dried, the SD electrode film is exposed using a fourth mask to form the exposed SD electrode film. After exposure, the SD electrode film is developed and then etched to form the source and drain of the switching devices in the amplifier circuit, feedback circuit, electrostatic protection circuit, startup circuit, bias circuit, and switching circuit, as well as the lower plate of the capacitor. The raw materials for preparing the second etch protective layer are chemically deposited on the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device and switching device in the switching circuit to form an initial barrier layer; Photoresist is coated onto the initial barrier layer. After the coated photoresist is dried, the initial barrier layer is exposed using a fifth mask to form the exposed initial barrier layer. After exposure, the initial barrier layer is developed and then dry-etched to form a barrier layer. Molybdenum is vapor-deposited onto the barrier layer to form the initial molybdenum plating layer; Photoresist is coated onto the initial molybdenum plating layer. After the coated photoresist is dried, the initial molybdenum plating layer is exposed using the sixth mask to form the exposed initial molybdenum plating layer. After exposure, the initial molybdenum plating layer is developed and then etched to form the molybdenum plating layer and the upper electrode of the negative feedback capacitor. A portion of the molybdenum plating layer connects the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device and the switching device in the switching circuit to each other, and connects the upper electrode of the negative feedback capacitor to the drain of the amplifier circuit device. A portion of the molybdenum plating layer is connected to the connection point where the source of the amplifier circuit device is connected to the upper plate of the negative feedback capacitor and the drain of the feedback circuit device, serving as the output terminal. A portion of the molybdenum plating layer is connected to the source of the amplifier circuit device and then grounded; The raw materials for preparing the third etch protective layer are chemically deposited on the upper electrode plate to form the third barrier layer; Photoresist is coated on the third barrier layer. After the coated photoresist is dried, the initial barrier layer is exposed in conjunction with the seventh mask to form the exposed third etched layer. After exposure, the third etched layer is developed and then dry-etched to form the third etched protective layer. Titanium is vapor-deposited onto the barrier layer to form the initial titanium layer; Photoresist is coated onto the initial titanium plating layer. After the coated photoresist is dried, the initial titanium plating layer is exposed using the eighth mask to form the exposed initial titanium plating layer. After exposure, the initial titanium plating layer is developed and then wet-etched to form the electrode layer. The raw materials for preparing the encapsulation layer are chemically vapor deposited onto the plated titanium layer to form the initial encapsulation layer; Photoresist is coated onto the initial encapsulation layer. After the coated photoresist is dried, the initial encapsulation layer is exposed using the ninth mask to form the exposed initial encapsulation layer. After exposure, the initial encapsulation layer is developed and then dry-etched to form an encapsulation layer, resulting in an active amplifier circuit.

[0012] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: This invention provides a multimodal biosignal sensor and its fabrication method. The sensor includes multiple active electrode units arranged in a matrix to form an active high-density electrode array. The active high-density electrode array has interdigitated electrodes at its edges. Each active electrode unit includes an active amplifier circuit and two electrodes. The active amplifier circuit includes an amplifying device, a biasing device, a load device, and a negative feedback capacitor. The interdigitated electrodes include six interleaved metal electrode structures. This invention achieves multidimensional sensing of muscle mechanical properties by coating the interdigitated electrodes with a mechanically and temperature-sensitive gel material. Simultaneously, it combines the spatial resolution advantage of the high-density electrode array to construct an electromyography-mechanical co-detection system. This invention uses indium gallium zinc oxide thin-film transistor technology to achieve integrated active amplifier circuit and electrode array. An innovative multiplexing architecture allows adjacent electrodes to share the amplifier circuit, significantly reducing system power consumption while ensuring signal quality. The unique interdigital structure design not only expands the signal acquisition dimensions but also captures electromyographic signal features from multiple angles. Combined with optimized circuit integration, it effectively suppresses signal crosstalk and noise interference. Experiments show that this multimodal collaborative detection system can significantly improve the accuracy of muscle movement intention recognition, providing an effective solution to the problem of insufficient accuracy in existing single-modal detection. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the active amplifier circuit in Example 1; Figure 2 The layout of the 12×6 active electrode array of Example 2 is drawn and will be used as a mask for this experiment; Figure 3 This is a schematic diagram of the active amplifier circuit of the present invention; Figure 4 This is a layout of a single electrode and operational amplifier circuit of the present invention and will be used as a mask template for this experiment; Figure 5 This is the layout of the interdigitated structure of the present invention and will be used as a mask template for this experiment; Figure 6 This is a cross-sectional view of the entire electrode; Figure 7 This is a transfer characteristic curve of a single N-type thin-film transistor in Example 3; Figure 8 This is a gain analysis diagram of the active amplifier circuit of a single amplification unit in Example 3 under frequency response test conditions; Figure 9 This is a gain analysis diagram of the active amplifier circuit of a single amplification unit in Example 3 under transient response test conditions; Figure 10 This is a gain analysis diagram of the active amplifier circuit of a single amplification unit in Example 2 under frequency response test conditions; Figure 11 This is a gain analysis diagram of the active amplifier circuit of a single amplification unit in Example 2 under transient response test conditions; Figure 12 Example 4 illustrates the electrical properties of the gel material in this invention in response to pressure changes. Figure 13 Example 4 illustrates the electrical properties of the gel material in this invention in response to temperature changes. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] The purpose of this invention is to provide a multimodal biosignal sensor and its fabrication method. Passive electrodes and amplification circuits are integrated on a flexible substrate, shortening signal transmission distance, reducing electromagnetic interference and noise, and improving integration. Each electrode is equipped with a dedicated amplification circuit to ensure the accuracy of weak electromyographic (EMG) signal acquisition. The device employs a multi-channel flexible electrode array, capable of simultaneously acquiring EMG signals from different sites, suitable for motion monitoring and rehabilitation assessment. Combined with multiplexing technology, the signal acquisition range can be expanded without adding hardware channels, reducing costs. The unique interdigital electrode structure, staggered on the substrate, enables multimodal detection in addition to acquiring EMG signals.

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] Example 1: like Figure 1As shown, this invention provides a multimodal biosignal sensor, comprising: multiple active electrode units, which are arranged in a matrix to form an active high-density electrode array, with interdigitated electrodes at the edges of the active high-density electrode array; temperature and pressure materials are applied to the active high-density electrode array and the interdigitated electrodes; each active electrode unit is an independent unit, and the VDD, electron, and GND interfaces of each independent unit are externally connected to the corresponding interfaces of other units, achieving unified external power supply and saving the number of port pins; the multimodal material coating of the interdigitated electrodes works in conjunction with the high-gain amplification of the active electrodes, which can optimize the matching for the electrophysiological characteristics of different muscle groups, significantly improving the reliability of motion intent decoding.

[0019] The active electrode unit includes an active amplifier circuit and two electrodes. The active amplifier circuit includes an amplifying device, a biasing device, a load device, and a negative feedback capacitor. The interdigitated electrode structure comprises six interlaced metal electrode structures.

[0020] The active amplifier circuit is connected as follows: the source of the bias device is connected to the gate of the load device and one end of the negative feedback capacitor, respectively; the other end of the negative feedback capacitor is connected to the source of the load device and the drain of the amplifier device, respectively; the connection point of the negative feedback capacitor, the source of the load device, and the drain of the amplifier device is the output terminal of the bootstrap inverter circuit; the gate of the amplifier device is connected to one end of the electrode; the source of the amplifier device is grounded; and the drain of the load device, the gate of the bias device, and the drain of the bias device are all connected to an external power supply.

[0021] The amplifying device, load device, and bias device are all thin-film transistors (TFTs). These TFTs possess excellent field-effect mobility, good stability, low-temperature manufacturing capability, flexibility, and low noise. The materials selected are as follows: the bottom gate uses Mo and ITO, the active layer is IGZO, the insulating layer is silicon oxide and silicon nitride, and the SD drain-source electrode layer uses Mo and ITO.

[0022] The active electrode unit is an integral structure. This active electrode unit is formed by integrating the electrode and the active amplifier circuit on a flexible substrate using metal oxide thin-film transistor lithography. The test electrode (i.e., the aforementioned electrode) is preferably disposed on the active amplifier circuit, and the test electrode and the active amplifier circuit are preferably integrated on the same flexible substrate. Integrating the test electrode and the active amplifier circuit on the flexible substrate to form an integral structure not only improves the integration of the acquisition system but also effectively reduces electromagnetic interference during signal transmission. Simultaneously, configuring an amplifier circuit for each passive electrode further improves the signal acquisition quality. The electrode has a circular protruding structure on its surface.

[0023] The active high-density electrode array is preferably a 12×12 electrode array, employing 144 active amplifier circuits. The matrix-style horizontal and vertical arrangement allows for simultaneous acquisition of electromyographic (EMG) signals from different sites. The test electrodes are preferably semi-circular in shape, with a diameter of 2 mm and a spacing of 4 mm to 5 mm between adjacent electrodes. The impedance of the test electrodes is preferably 200 MΩ. Using circular electrodes perpendicular to the muscle fibers, increasing the electrode size within a certain range reduces the impedance between the skin and the electrode, thereby improving acquisition quality. The spacing between the test electrodes is controlled between 4 mm and 5 mm to ensure adequate MUAP spatial resolution between the electrodes, thus improving the quality of the acquired EMG signals.

[0024] In this invention, during the fabrication process of the active high-density electrode array, test electrodes are dry-etched onto the packaging layer of the active amplifier circuit.

[0025] In practical applications, the flexible substrate material is selected as PI thin film because PI thin film is an organic polymer film that is not only resistant to hydrolysis, high temperature, and corrosion, but also has good biocompatibility and beneficial insulation properties. Therefore, polyimide is chosen as the base material for the substrate. Due to the high field-effect mobility, good stability, low-temperature manufacturing, flexibility, and low noise characteristics of thin-film transistors, IGZO oxide thin-film transistors are selected as the basic device for the amplification circuit.

[0026] The flexible polyimide film substrate includes a polyimide film layer and a buffer layer stacked sequentially from bottom to top; the buffer layer includes a silicon nitride film and a silicon dioxide film stacked sequentially from bottom to top.

[0027] The thickness of the silicon nitride film is 300-400 nm, preferably 350 nm. The thickness of the silicon dioxide film is 200-300 nm, preferably 250 nm.

[0028] The flexible substrate is a flexible polyimide substrate, and the flexible polyimide substrate includes, from bottom to top, a thin film transistor layer, a metal layer, an insulating layer, another metal layer, an insulating layer, and an electrode layer.

[0029] The amplifying device, load device, and bias device are all composed of a bottom gate layer, an active layer, an ES etched layer, an SD drain-source electrode layer, an etch protection layer, a copper plating layer, and a protective layer stacked sequentially from bottom to top. The fabrication process is as follows: On the first bottom gate layer, the bottom gate structures of the amplifier transistor, bias transistor, and load transistor, as well as the lower electrode of the negative feedback capacitor, are fabricated. Before fabricating the active layer, an insulating layer is first fabricated using silicon oxide and silicon nitride, followed by the growth of the active layer IGZO. The third etching layer uses a dry etching process to ensure interconnection between the active layer and the SD drain-source layer. On the SD drain-source electrode layer, the drain-source electrodes of the amplifier transistor, bias transistor, and load transistor, as well as the upper electrode of the feedback capacitor, are fabricated. Simultaneously, the insulating layer and the etching layer serve as the dielectric layer for the capacitor, and a dry etching process is used to connect the SD and gate layers to create a resistor. On top of the SD layer, a water-oxygen isolation layer is fabricated to protect the circuit structure. Then, a copper layer is fabricated, and copper electrodes and the upper electrode of the negative feedback capacitor are fabricated. Copper wires are used to connect each active circuit to the peripheral interface. Finally, a protective layer is laid on top of the copper layer to protect and encapsulate the copper wires, and a dry etching process is used to expose the electrodes and various test interfaces for electromyography signal testing. The amplifier, load transistor, and bias transistor are preferably integrated into a single thin-film transistor.

[0030] The thin-film transistor preferably includes an insulating layer, an etched layer, a barrier layer, and an encapsulation layer stacked sequentially from bottom to top.

[0031] The thin-film transistor includes an insulating layer; the insulating layer preferably includes a silicon nitride film and a silicon oxide film stacked sequentially from bottom to top; the insulating layer can prevent the electrical performance of the active amplifier circuit from being affected.

[0032] Preferably, the insulating layer contains the lower electrode of the gate of the amplifier, load transistor, and bias transistor, the feedback capacitor, and the AC / DC integrated capacitor; the lower electrode of the gate of the amplifier, load transistor, and bias transistor, the feedback capacitor, and the AC / DC integrated capacitor preferably includes a Mo film and an ITO film stacked sequentially from bottom to top.

[0033] The thin-film transistor preferably includes an etched layer attached to the surface of the insulating layer; the etched layer preferably includes a silicon oxide film; the etched layer preferably contains an active layer for the amplifier, load transistor, and bias transistor; the active layer preferably includes an IGZO film; The thin-film transistor preferably includes a barrier layer attached to the surface of the etched layer; the barrier layer preferably includes a silicon oxide film; the source and drain of the amplifier, load transistor and bias transistor are preferably disposed in the barrier layer; the source, drain and upper plate preferably include a Mo film and an ITO film stacked sequentially from bottom to top.

[0034] In this invention, the thin-film transistor preferably includes an encapsulation layer attached to the surface of the barrier layer, and the encapsulation layer preferably includes a silicon oxide film. In this invention, the encapsulation layer preferably contains a copper electrode and the upper plate of a negative feedback capacitor. Copper has advantages such as stable chemical properties and high conductivity. In flexible electronics, it possesses the characteristic of simultaneously achieving both conductivity and flexibility, and exhibits low resistivity change during bending. The function of the copper layer is similar to that of the SD electrode layer; however, because the designed active electrode acts on the skin surface, molybdenum (Mo) is harmful to human skin and is unsuitable as the electrode material for this layer. Compared to molybdenum electrodes, copper electrodes are harmless to the human body.

[0035] This invention designs a bootstrap amplifier circuit structure based on a-IGZO, introducing a negative feedback structure to achieve higher gain. Furthermore, the low-noise characteristics of the TFT reduce noise introduction while amplifying the acquired electromyographic signals, resulting in a higher signal-to-noise ratio for the entire circuit. Example 2: like Figure 6 As shown, the present invention also provides an embodiment 2, which is similar in structure to embodiment 1. The interdigitated electrode structure consists of six groups, with a spacing of 50 micrometers between each group. Each group is composed of 28 interlaced titanium electrodes. The active high-density electrode array has 12 rows and 6 columns.

[0036] This invention provides a layout drawing of a 12×6 active electrode array as an embodiment, which will be used as a mask template for this experiment, specifically as follows: Figure 2 As shown; furthermore, the layout of the individual electrodes and operational amplifier circuits will be used as a mask template for this experiment, as shown. Figure 4 As shown, the layout of the interdigitated structure will be used as the mask template for this experiment. Figure 5 As shown.

[0037] The active amplifier circuit includes amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices, and switching devices in the switching circuit. In this embodiment, the amplifier circuit devices, feedback circuit devices, startup circuit devices, and bias circuit devices are the amplifier transistor, feedback transistor, startup transistor, and bias transistor, respectively.

[0038] The amplifier circuit device, the feedback circuit device, the bias circuit device, and the startup circuit device are all indium gallium zinc oxide thin film transistors. Thin film transistors have good field-effect mobility, stability, low-temperature manufacturing, flexibility, and low noise. The bottom gate of the thin film transistor is made of Mo and ITO, the active layer is IGZO, the insulating layer is silicon oxide and silicon nitride, and the SD drain-source electrode layer is made of Mo and ITO.

[0039] The active amplifier circuit is composed of a feedback circuit, a startup circuit, and a bias circuit connected together; the feedback amplifier circuit is composed of the feedback circuit device and the negative feedback capacitor connected together; the startup circuit is composed of the startup circuit device; the bias circuit is composed of the bias circuit device and the resistor connected together.

[0040] The connection method of the active amplifier circuit includes: the output terminal of the bias device is connected to the output terminal of the startup circuit device and the current mirror and gate of the amplifier circuit device, respectively; one end of the capacitor in the feedback circuit device is connected to the output of the amplifier circuit device and the other end is connected to the input terminal of the amplifier circuit device; the drain of the thin-film transistor in the feedback circuit device is connected to the output of the amplifier circuit device, the source is connected to the input terminal of the amplifier circuit device, and the gate and drain are connected; the input terminal of the electrostatic protection circuit is connected to the electrode, and the output terminal is connected to the input terminal of the switching circuit; the source of the switching circuit device is connected to the input terminal of the amplifier circuit; all switching circuit devices are connected to an external power supply; the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, and bias circuit device are all connected to an external power supply. The interdigitated electrode is connected to an external power supply.

[0041] Active amplifier circuit structure as follows Figure 3 As shown, its main structure consists of a five-transistor differential circuit and a common-source, common-gate circuit as the amplification section, connected to a bias circuit. A switching circuit is connected to the input of the differential circuit to allow the two electrodes to share a single amplifier circuit for selection. An electrostatic discharge (ESD) protection circuit is connected to the electrode input, and the ESD protection circuit is then connected to a capacitor. The drains of the amplification circuit, ESD protection device, bias circuit, and startup circuit are connected to a positive power supply, while the sources of these devices are connected to a negative power supply.

[0042] The active electrode unit is a single, integrated structure. It is formed by integrating the electrode and the active amplifier circuit onto a flexible substrate using photolithography with indium gallium zinc oxide thin-film transistors. The test electrode (i.e., the electrode in this invention) is preferably located above the active amplifier circuit; the test electrode and the active amplifier circuit are preferably integrated onto a single flexible substrate. Integrating the test electrode and the active amplifier circuit onto a flexible substrate improves the integration of the acquisition system, reduces electromagnetic interference received during signal transmission, and allows for the configuration of an amplifier circuit for each passive electrode to improve signal acquisition quality.

[0043] The active high-density electrode array is preferably a 12×6 electrode array. It utilizes 72 active amplifier circuits. The matrix-style horizontal and vertical arrangement allows for simultaneous acquisition of electromyographic signals from different sites. The test electrodes are preferably circular in shape, with a diameter of 2.5 mm and a spacing of 2.5 mm between adjacent electrodes. The impedance of the test electrodes is preferably 150 MΩ. Using circular electrodes perpendicular to the muscle fibers, increasing the electrode size within a certain range reduces the impedance between the skin and the electrode, thereby improving acquisition quality. The spacing between the test electrodes is controlled at 2.5 mm to ensure adequate MUAP spatial resolution between the electrodes, thus improving the quality of the acquired electromyographic signals.

[0044] The active electrode module of this invention is constructed using an indium gallium zinc oxide thin-film transistor, and is formed by integrating the test electrode and the active amplifier circuit on a flexible substrate. The electrode has a circular protruding structure on its surface.

[0045] In practical applications, the flexible substrate material is selected as a polyimide (PI) film. This is because PI film is an organic polymer film that is not only resistant to hydrolysis, high temperatures, and corrosion, but also possesses good biocompatibility and beneficial insulation properties; therefore, polyimide is chosen as the base material for the substrate. Due to the high field-effect mobility, good stability, low-temperature manufacturing, flexibility, and low noise characteristics of thin-film transistors (TFTs), IGZO TFTs are selected as the basic components of the amplifier circuit.

[0046] Specifically, the flexible polyimide film substrate includes a polyimide film layer and a buffer layer stacked sequentially from bottom to top; the buffer layer includes a silicon nitride film and a silicon dioxide film stacked sequentially from bottom to top.

[0047] Furthermore, the thickness of the silicon nitride film is 300 nm. The thickness of the silicon dioxide film is 200 nm.

[0048] In one specific implementation, the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching device in the switching circuit are all composed of a buffer layer, an active layer, a first etched layer, a gate layer, a second etched layer, a capacitor upper electrode layer, a third etched layer, and an electrode layer stacked sequentially from bottom to top. In the first layer, buffer layers for the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching device in the switching circuit are fabricated. In the second layer, IGZO thin films for the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching device in the switching circuit are fabricated. A pre-designed TFT channel layer pattern is etched into the IGZO thin film using etching technology. The purpose of the third layer, the first etched layer, is to deposit an insulating layer and form the gate dielectric layer of the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching device in the switching circuit through dry etching. The fifth layer, the source / drain layer, forms the gate of the device and the lower electrode of the feedback capacitor by depositing molybdenum metal and then etching it with wet etching. The fourth layer, the second etched layer, deposits an insulating layer through CVD and then prepares the dielectric layer required for the capacitor through dry etching. The seventh layer, the upper electrode layer of the capacitor, prepares the upper electrode required for the capacitor and the metal interconnection with the outside through magnetron sputtering. The fifth layer, the third etched layer, deposits an insulating layer through CVD and then prepares the dielectric layer between the electrode layer and the electrode layer through dry etching. The sixth layer, the electrode layer, prepares titanium metal through magnetron sputtering and then prepares circular electrodes through dry etching. Finally, a protective layer is laid on the titanium layer to protect and encapsulate the titanium electrodes, and the electrodes and various test interfaces are exposed through dry etching to facilitate electromyography signal testing.

[0049] In this invention, the thin-film transistor preferably includes a buffer layer, a low-temperature polysilicon layer, an insulating layer, a gate electrode layer, and an encapsulation layer stacked sequentially from bottom to top.

[0050] In this invention, the thin-film transistor preferably includes a buffer layer; the buffer layer preferably includes a silicon nitride film and a silicon oxide film stacked sequentially from bottom to top; the buffer layer prevents metal ions in the glass or some polluting molecular substances present on the glass surface from entering the indium gallium zinc oxide thin film.

[0051] Preferably, the insulating layer contains the gate of the amplifier circuit device, the feedback circuit device, the electrostatic protection circuit device, the startup circuit device, the bias circuit device, and the switching device in the switching circuit, as well as the lower electrode of the feedback capacitor; the gate of the amplifier circuit device, the feedback circuit device, the electrostatic protection circuit device, the startup circuit device, the bias circuit device, and the switching device in the switching circuit, as well as the lower electrode of the feedback capacitor, preferably include Mo films stacked sequentially from bottom to top.

[0052] In this invention, the thin-film transistor preferably includes an etched layer attached to the surface of the insulating layer; the etched layer preferably includes a silicon oxide film; the etched layer preferably contains an active layer of the amplification circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching device in the switching circuit; the active layer preferably includes an indium gallium zinc oxide thin film; The thin-film transistor preferably includes a barrier layer attached to the surface of the etched layer; the barrier layer preferably includes a silicon oxide film; the barrier layer preferably contains the source and drain of an amplification circuit device, a feedback circuit device, an electrostatic protection circuit device, a startup circuit device, a bias circuit device, and a switching device in a switching circuit; the source, drain, and upper plate preferably include a Mo film.

[0053] In this invention, the thin-film transistor preferably includes an encapsulation layer attached to the surface of the barrier layer, and the encapsulation layer preferably includes a silicon oxide film. In this invention, the encapsulation layer preferably contains a titanium electrode and the upper plate of a negative feedback capacitor. Titanium has advantages such as stable chemical properties and high conductivity. In flexible electronics, it possesses the characteristic of simultaneously achieving both conductivity and flexibility, and exhibits low resistivity change during bending. The function of the titanium layer is similar to that of the SD electrode layer, but because the designed active electrode acts on the skin surface exposed to air, the molybdenum element pair is chosen. Compared to molybdenum electrodes, titanium electrodes are less prone to oxidation.

[0054] This invention designs a multi-channel amplifier circuit structure based on IGZO, and designs an interdigital electrode structure to realize multimodal signal detection. The TFT has low noise characteristics, which can reduce the introduction of noise while amplifying the acquired electromyographic signals, thereby giving the entire circuit a higher signal-to-noise ratio.

[0055] Example 3 This invention also provides a method for fabricating a multimodal biosignal sensor. Taking Example 2 as an example, this invention describes the method, which includes the following steps: A molybdenum thin film is deposited by magnetron sputtering on the active layer of amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices, and switching devices in the switching circuit.

[0056] Photoresist is coated onto the molybdenum film. After the coated photoresist is dried, the initial active layer is exposed and etched using a first mask to form the source and drain layers.

[0057] Indium gallium zinc oxide thin films are deposited by chemical vapor deposition on the active layers of amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices, and switching devices in switching circuits.

[0058] Photoresist is coated onto the indium gallium zinc oxide thin film. After the coated photoresist is dried, the initial active layer is exposed and etched using a second mask.

[0059] The indium gallium zinc oxide thin film deposited by chemical vapor deposition is annealed at a certain temperature to repair lattice damage.

[0060] The active layer is subjected to gate insulating layer thin film deposition to form the gate insulating layer required for amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices and switching devices in switching circuits.

[0061] The raw materials for preparing the etching layer are chemically deposited on the gate insulating layer to form the initial etching layer.

[0062] Photoresist is coated onto the initial etched layer. After the coated photoresist is dried, it is exposed to the initial etched layer in conjunction with a third mask to form the first initial etched layer after exposure.

[0063] After developing the initial etched layer after exposure, dry etching is performed to reserve gaps between the active layer of the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device and the corresponding SD drain and source, one end of the feedback capacitor, and the interconnection between the gate of the amplifier and the resistor, thus forming the first etched layer.

[0064] Metal is deposited on the first etched layer to form the initial gate layer required for the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching device and feedback capacitor in the switching circuit.

[0065] The initial gate layer is coated with photoresist, and after the coated photoresist is dried, the initial gate layer is exposed in conjunction with a fourth mask.

[0066] After the initial gate layer is exposed, it is developed and then wet-etched to form the lower plate layer of the feedback capacitor and the gate of the transistor.

[0067] An insulating layer is deposited on the gate layer to form the dielectric layer of the feedback capacitor.

[0068] The dielectric layer of the feedback capacitor is coated with photoresist. After the photoresist is dried, it is used in conjunction with a fifth photomask to expose the initial etching layer, forming the initial second etching layer after exposure.

[0069] After developing the initial etched layer after exposure, dry etching is performed to form the source and drain traces of the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, start-up circuit device, bias circuit device and the switching device in the switching circuit, one end of the feedback capacitor, and the pre-reserved holes for interconnection, forming the second etched layer.

[0070] The dielectric layer is subjected to metal deposition to form the metal layer of the upper electrode of the feedback capacitor and the metal trace.

[0071] Photoresist is coated onto the metal layer. After the photoresist is dried, the initial etched layer is exposed using a sixth photomask to form the initial upper board layer and the initial metal trace layer of the feedback capacitor.

[0072] After developing the exposed initial upper layer and initial metal trace layer, wet etching is performed to form the upper layer and metal trace layer of the feedback capacitor.

[0073] An insulating layer is deposited on the upper plate layer and the metal trace layer to form a dielectric layer between the electrode and the electrode.

[0074] Photoresist is coated onto the dielectric layer between the electrodes. After the coated photoresist is dried, it is used in conjunction with a seventh photomask to expose the initial etched layer, forming the initial third etched layer after exposure.

[0075] After developing the initial third etched layer after exposure, dry etching is performed to reserve a hole for the interconnection between the upper plate and the electrode of the capacitor, thus forming the third etched layer.

[0076] The third etched layer is then subjected to metal deposition to form an electrode layer.

[0077] Photoresist is coated onto the electrode layer. After the coated photoresist is dried, it is used in conjunction with an eighth photomask to expose the initial etched layer, thus forming the exposed initial electrode layer.

[0078] After the initial electrode layer is exposed, it is developed and then wet-etched to form a circular electrode pattern.

[0079] In this invention, the flexible substrate sputtered by magnetron sputtering preferably comprises a PI film, a silicon oxide film, and a silicon nitride film stacked sequentially from bottom to top. The silicon oxide film and silicon nitride film can make the PI film more flat, thereby facilitating the fabrication of subsequent amplification circuits. This invention provides an embodiment of an electrode, the cross-sectional view of which is shown below. Figure 6 As shown.

[0080] PI film is an organic polymer film that is not only resistant to hydrolysis, high temperature and corrosion, but also has good biocompatibility and beneficial insulation properties.

[0081] The method for preparing the flexible substrate preferably includes the following steps: After coating the PI slurry onto the glass, it is cured, and then the resulting film is annealed to form a PI film. Silicon oxide and silicon nitride films were prepared on the PI film using chemical vapor deposition.

[0082] Preferably, the glass is cleaned and dried before coating. The present invention does not impose any special limitations on the cleaning process; any method well-known to those skilled in the art can be used to clean the glass until no dust remains.

[0083] In this invention, the annealing process conditions preferably include rapid thermal annealing, with a preferred temperature of 250 degrees Celsius and an annealing time of one hour.

[0084] After forming the active layer, the present invention coats photoresist on the initial gate layer, dries the coated photoresist, and exposes the initial gate layer in conjunction with the first mask to form the exposed initial active layer.

[0085] The design pattern is transferred onto photoresist by passing light through and blocking it using a photomask, thus creating the circuit.

[0086] After forming the initial active layer after exposure, the present invention performs development treatment on the initial active layer after exposure and then performs wet etching to form the active layer of the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, start-up circuit device, bias circuit device and switching device in the switching circuit.

[0087] After forming the active layer of amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices, and switching devices in switching circuits, it is annealed by excimer laser.

[0088] In this invention, the development process is preferably carried out for 1 minute and 15 seconds.

[0089] In this invention, the product obtained from the development process is preferably cleaned and dried before wet etching.

[0090] In this invention, when the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching device in the switching circuit comprise polysilicon stacked sequentially from bottom to top, the dry etching preferably includes SF6:O2=80:15.

[0091] After forming the active layer of the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching device in the switching circuit, the present invention performs ion implantation on the active layer of the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching device in the switching circuit to form transistors with different polarities.

[0092] The active layer is subjected to gate insulating layer thin film deposition to form the gate insulating layer required for amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices and switching devices in switching circuits.

[0093] Photoresist is coated onto the gate insulating layer. After the coated photoresist is dried, it is used in conjunction with a third mask to expose the initial etched layer, thus forming the exposed initial etched layer.

[0094] After developing the initial etched layer after exposure, dry etching is performed to reserve gaps between the active layer of the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device and the switching device in the switching circuit and the corresponding SD drain and source, and with the resistor, to form the first etched layer.

[0095] After the first etched layer is formed, metal deposition is performed to form the gate layer required for the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching device and feedback capacitor in the switching circuit.

[0096] In this invention, the material of the gate layer is molybdenum.

[0097] The gate layer is coated with photoresist, and after the coated photoresist is dried, the initial gate is exposed in conjunction with a fourth photomask.

[0098] In this invention, the ultraviolet dose of the exposure treatment is 180 candela per square centimeter, and the exposure time is 10 seconds.

[0099] After forming the exposed gate layer, the present invention performs development treatment on the exposed gate layer and then etching to form the precursor of the gate of the switching device and the feedback capacitor lower stage board in the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, start-up circuit device, bias circuit device and switching circuit.

[0100] In this invention, the development process is preferably carried out for 1 minute and 15 seconds.

[0101] In this invention, the product obtained from the development process is preferably cleaned and dried before wet etching.

[0102] In this invention, when the first metal layer is a molybdenum film, the etching solution used for etching preferably includes oxalic acid.

[0103] After the gate layer is formed, the present invention deposits a capacitor insulating layer.

[0104] After forming the capacitor insulating layer, the present invention coats photoresist on the capacitor insulating layer, dries the coated photoresist, and then exposes the initial etching layer with a fourth mask to form the second etching layer after exposure.

[0105] After forming the second etched layer after exposure, the present invention performs dry etching after developing the initial etched layer after exposure to reserve gaps between the switching devices in the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device and the corresponding SD drain and source, and between the upper plate of the capacitor and the resistor, thus forming the second etched layer.

[0106] The upper electrode of the initial feedback capacitor and the metal trace layer are formed by magnetron sputtering on the second etched layer.

[0107] Photoresist is coated onto the upper electrode and metal trace layer of the initial feedback capacitor. After the coated photoresist is dried, the initial etched layer is exposed using the sixth photomask to form the upper electrode and metal trace layer of the exposed feedback capacitor.

[0108] After developing the upper plate of the feedback capacitor and the metal trace layer, wet etching is performed.

[0109] In this invention, the solution used for wet etching is oxalic acid, and the upper electrode of the feedback capacitor and the metal trace layer are made of molybdenum.

[0110] After wet etching, the present invention preferably cleans the resulting product. The cleaning preferably includes scrubbing with a positive adhesive stripping solution; the temperature of the positive adhesive stripping solution is preferably 55°C, and the scrubbing time is preferably 5 minutes.

[0111] After forming the upper electrode and metal trace layer of the feedback capacitor, an insulating layer is deposited to form the dielectric layer of the upper electrode and metal trace layer of the feedback capacitor.

[0112] After forming the dielectric layer, the present invention coats photoresist on the dielectric layer, dries the coated photoresist, and then exposes the dielectric layer with a sixth photomask to form the exposed dielectric layer.

[0113] After the exposed dielectric layer is developed, it is dry-etched to reserve a gap for the connection between the upper plate of the feedback capacitor and the electrode.

[0114] After the dry etching, the present invention preferably cleans the resulting product. The cleaning preferably includes scrubbing with a positive adhesive stripping solution; the temperature of the positive adhesive stripping solution is preferably 55°C, and the scrubbing time is preferably 5 minutes.

[0115] After forming the dielectric layer, the present invention uses magnetron sputtering to deposit metal to form the electrode layer.

[0116] In this invention, the electrode layer is preferably made of metallic titanium.

[0117] After the electrode layer is formed, photoresist is coated onto the electrode layer. After the coated photoresist is dried, the electrode layer is exposed in conjunction with the eighth photomask to form the exposed electrode layer.

[0118] After forming the exposed electrode layer, the present invention performs wet etching after developing the exposed electrode layer.

[0119] In this invention, the solution used for wet etching is preferably a mixture of hydrofluoric acid and hydrogen peroxide, and the etching is performed at room temperature for 45 seconds.

[0120] The designed electrode shape was formed through etching.

[0121] In this invention, the electrode shape is preferably a circle or an interdigitated shape with a diameter of 5 mm.

[0122] After the electrode layer is formed, the present invention performs chemical vapor deposition on the raw materials for preparing the encapsulation layer on the electrode layer to form the initial encapsulation layer.

[0123] Photoresist is coated onto the initial encapsulation layer. After the coated photoresist is dried, the initial encapsulation layer is exposed in conjunction with the eighth template to form the exposed initial encapsulation layer. After the initial encapsulation layer is exposed, it is developed and then dry-etched to etch out test points, thus forming the encapsulation layer.

[0124] Example 4: like Figure 4 and Figure 5 As shown, taking the active electrode array and interdigitated electrode structure used in this invention as examples, the specific fabrication process is as follows: Step 1: Fabrication of the flexible substrate (1) Select a glass with a specification of 6cm×4cm and place it in a surface cleaning machine for cleaning. After ensuring that the surface is clean and free of dust, heat and dry it to prevent surface moisture from affecting the subsequent film formation process.

[0125] (2) Spin-coating PI slurry onto the cleaned glass plate, adjusting the spin coater settings to 450 rpm for 35 seconds to achieve a film thickness of 10 μm. After completion, the plate is transferred to an annealing furnace for curing. The step temperature and time settings are: 130℃ for half an hour, 160℃ for half an hour, 180℃ for one hour, 260℃ for half an hour, and 410℃ for ten minutes for annealing. After cooling to room temperature, to make the PI film layer smoother and facilitate subsequent circuit fabrication, a 350 nm thick silicon oxide (120 nm) silicon nitride (220 μm) film is grown on the PI film layer using CVD plasma chemical vapor deposition as a buffer protective layer, referred to as the PI substrate. The growth process temperature is 360℃.

[0126] The purpose of annealing PI films is: (1) PI films have good thermal stability at high temperatures, and annealing can further improve their thermal stability. (2) The annealing process can affect the molecular arrangement and crystallinity of the polyimide film, thereby adjusting its mechanical properties. This includes improving the film's strength, hardness, and wear resistance.

[0127] The purpose of annealing the thin-film transistor layer mentioned later is: (1) Annealing process realizes the recrystallization from amorphous silicon to polycrystalline silicon. (2) The annealing process can adjust the carrier concentration in the dopant, thereby obtaining better electron transport performance. (3) Annealing can activate the P-type and N-type doping of the polycrystalline silicon active layer.

[0128] The second step involves the fabrication of the bottom gate of the active amplifier circuit. (1) Place the completed PI substrate in a surface cleaning machine for cleaning. After ensuring that the surface is clean and free of dust, perform a heating and drying process.

[0129] (2) The cleaned PI substrate is placed in a magnetron sputtering instrument and the IGZO layer of the thin film transistor is grown by magnetron sputtering.

[0130] (3) After completing the magnetron sputtering process, the IGZO layer is annealed by annealing in a nitrogen atmosphere at 250 degrees Celsius for one hour to repair lattice damage. Then, photolithography and etching processes are performed to define the active layer pattern. The etching is preferably performed in an oxalic acid solution at 45 degrees Celsius for 45 seconds to ensure pattern accuracy.

[0131] (4) Deposit the gate insulating layer. The SiNx / SiO2 stacked structure is grown by PECVD process, and the total thickness is controlled at 150-250nm. The deposition parameters of the SiNx layer are: SiH4:NH3:N2=1:5:15, power 300-500W, temperature 320-350°C; the deposition parameters of the SiO2 layer are: TEOS:O2=1:8, power 200-400W, temperature 350-380°C.

[0132] (5) Gate metal layer deposition and patterning: Mo was selected, with a total thickness of approximately 300-400 nm. The Mo layer deposition rate was controlled at 0.2-0.3 nm / s by magnetron sputtering. Oxalic acid etching was performed after photolithography to ensure that the sidewall steepness was >85°.

[0133] (6) Deposit interlayer dielectric layer: SiO2 material is deposited using PECVD, with a thickness of approximately 400-600 nm. After deposition, chemical mechanical polishing (CMP) is performed to control the flatness within ±5 nm, providing a smooth surface for subsequent contact hole processes.

[0134] (7) Spin coat the photoresist at 1000 rpm for 30 seconds on the spin coater. After pre-baking, use a photolithography machine with a mask to complete the exposure.

[0135] (8) The exposed molybdenum metal is subjected to a developing process, with the developing time controlled at 45s. After cleaning in a water bath, it is dried and then placed under a microscope to observe the exposure.

[0136] (9) Dry etching is performed on the developed glass plate to form transistor gate, source and drain contact holes.

[0137] The third step involves the fabrication of the gate of the active amplifier circuit and the lower plate of the capacitor. (1) Based on the completed dielectric layer, molybdenum metal was sputtered using magnetron sputtering (PVD, CME-200E, Japan).

[0138] (2) After completing the magnetron sputtering step, the photoresist is spin-coated at 1000 rpm for 30 seconds on the spin coater. After the pre-baking process is completed, the photolithography machine is used in conjunction with the mask to complete the exposure.

[0139] (3) The exposed molybdenum metal is subjected to a developing process, with the developing time controlled at 45s. After cleaning in a water bath, it is dried and then placed under a microscope to observe the exposure.

[0140] (4) The developed glass plate is wet etched. Under normal temperature conditions, molybdenum is etched with oxalic acid to form the gate layer and the lower plate of the capacitor. The final pattern drawn realizes the interconnection between the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, start-up circuit device, bias circuit device and the switching device and the lower plate of the capacitor in the switching circuit.

[0141] (5) Place the glass plate in the annealing furnace and set the annealing conditions to room temperature - 220°C for 30 minutes, maintain 220°C for one hour. After annealing, wait for it to cool to room temperature and clean the glass plate.

[0142] Step 4: Fabrication of the capacitor dielectric layer: (1) A silicon oxide layer with a thickness of 200 nm is grown as a dielectric layer on the gate layer and the lower plate of the capacitor by chemical vapor deposition.

[0143] (2) After completing this step, spin coating photoresist is performed by setting the spin coating stage to rotate at 1000 rpm for 30 seconds. After pre-baking, exposure is completed using a photolithography machine with a mask.

[0144] (3) The exposed glass plate is subjected to a developing process, with the developing time controlled at 45s. The plate is then cleaned in a water bath, dried, and then placed under a microscope to observe the exposure.

[0145] (4) Dry etching process is performed on the developed glass plate (the input terminal, output terminal, gate, upper plate of capacitor and drain terminal of each active amplifier circuit are drilled).

[0146] (5) After the glass plate is dry-etched, place it in a water bath at 60°C and a positive adhesive stripper at 55°C and scrub for 5 minutes to complete the cleaning.

[0147] Step 5: Fabrication of the capacitor's upper electrode and the circuit metal trace layer: (1) A 70nm thick Mo film corresponding to the capacitor was grown sequentially on the glass plate after etching by sputtering process, and the input terminal, output terminal, gate and upper plate of each active amplifier circuit were interconnected.

[0148] Specifically, using a magnetron sputtering apparatus at room temperature, Mo with a film thickness of 70 nm is sputtered on top of an etch barrier layer as the upper electrode of the capacitor and the metal trace layer.

[0149] (2) After completing the magnetron sputtering step, the photoresist is spin-coated at 1000 rpm for 30 seconds on the spin coater. After the pre-baking process is completed, the photolithography machine is used in conjunction with the mask to complete the exposure.

[0150] (3) The exposed glass plate is subjected to a developing process, with the developing time controlled at 45s. The plate is then cleaned in a water bath, dried, and then placed under a microscope to observe the exposure.

[0151] (4) The developed glass plate is wet etched, and Mo is etched in a room temperature molybdenum-aluminum etchant to form the upper electrode plate and metal trace layer of the capacitor. After cleaning, it is moved to a microscope for observation.

[0152] Step 6: Electrode layer preparation (1) After the upper electrode of the capacitor and the circuit metal trace layer have been fabricated, a silicon oxide layer with a thickness of 200 nm is grown on the glass plate by chemical vapor deposition process as a dielectric layer. (2) Photoresist was spin-coated on the barrier layer at a spin coating stage with a rotation speed of 1000 rpm for 30 seconds. After pre-baking, exposure was completed using a photolithography machine with a mask.

[0153] (3) The exposed glass plate is subjected to a developing process, with the developing time controlled at 45s. The plate is then cleaned in a water bath, dried, and then placed under a microscope to observe the exposure.

[0154] (4) Dry engraving process is performed on the developed glass plate.

[0155] (5) After the glass plate is dry-etched, place it in a water bath at 60°C and a positive adhesive stripper at 55°C and scrub for 5 minutes to complete the cleaning.

[0156] Step 7: Active amplifier circuit fabrication and titanium plating layer fabrication: (1) Place the glass plate after the barrier layer has been made in the magnetron sputtering machine, adjust the process parameters to power of 0.5KW and time of one hour to deposit a titanium layer with a film thickness of 200nm.

[0157] (2) Photoresist was spin-coated on the barrier layer at a spin coating stage with a rotation speed of 1000 rpm for 30 seconds. After pre-baking, exposure was completed using a photolithography machine with a mask.

[0158] (3) The exposed glass plate is subjected to a developing process, with the developing time controlled at 45s. The plate is then cleaned in a water bath, dried, and then placed under a microscope to observe the exposure.

[0159] (4) Dry etching is performed on the developed glass plate to etch the designed electrode shape by plasma etching.

[0160] Step 8: Fabrication of the active amplifier circuit package layer: (1) A 200 nm thick silicon oxide film is grown on the glass plate after the copper electrode layer has been fabricated by chemical vapor deposition as an encapsulation protective layer.

[0161] (2) Photoresist was spin-coated on the barrier layer at a spin coating stage with a rotation speed of 1000 rpm for 30 seconds. After pre-baking, exposure was completed using a photolithography machine with a mask.

[0162] (3) The exposed glass plate is subjected to a developing process, with the developing time controlled at 45s. The plate is then cleaned in a water bath, dried, and then placed under a microscope to observe the exposure.

[0163] (4) The developed glass plate is subjected to dry etching process to etch out the amplifier circuit test points and test electrodes of each active electrode.

[0164] (5) After the glass plate is dry-etched, place it in a water bath at 60°C and a positive adhesive stripper at 55°C and scrub for 5 minutes to complete the cleaning.

[0165] The ninth step involves peeling the prepared active electrode array off the glass plate and encapsulating it by fixing it onto a flexible material. This facilitates subsequent electromyography signal acquisition and extends its lifespan, thus forming the final flexible electrode required.

[0166] This invention also provides a pressure- and temperature-sensitive gel material, the specific preparation steps of which include: First, prepare a temperature-sensitive and pressure-sensitive composite hydrogel prepolymer with an interpenetrating network structure. By mass, dissolve 10-20 parts of N-isopropylacrylamide monomer, 1-5 parts of acrylamide, and 0.1-1 parts of crosslinking agent N,N'-methylenebisacrylamide in 100 parts of deionized water and stir until completely dissolved.

[0167] Add 0.1-0.5 parts of photoinitiator 2-hydroxy-2-methylphenylacetone and stir evenly under light-protected conditions; to enhance the pressure sensitivity of the hydrogel, add an additional 0.5-2 parts of nano clay as a physical crosslinking enhancer, and add 0.1-0.3 parts of conductive filler poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate to improve the electrical signal response characteristics.

[0168] The obtained prepolymer solution was uniformly coated onto the surface of the interdigitated electrodes and electrode array using a precision spin coater or a controllable micro-drop coating system, with the coating thickness controlled to be 100-500 micrometers. The hydrogel was then controlled by surface tension to form a uniform bridging structure in the electrode gaps. Subsequently, cross-linking polymerization was carried out under nitrogen protection by ultraviolet light irradiation with a wavelength of 365 nm, a light intensity of 10-50 mW / cm², and an exposure time of 30-120 seconds. Patterned gel deposition in specific areas of the electrodes was achieved using mask technology.

[0169] After polymerization, the resulting integrated hydrogel electrode structure was immersed in deionized water for 48 hours, with the water being changed every 8 hours to remove unreacted monomers and impurities.

[0170] Finally, the cleaned sensor was dried in a vacuum environment at 25°C for 12 hours, and the porous microstructure of the hydrogel was maintained by critical point drying technology, resulting in a hydrogel-modified multimodal biosignal sensor with enhanced pressure and temperature sensitivity.

[0171] By spin-coating a nanocomposite hydrogel onto a flexible interdigital electrode, applying a voltage to the electrode, and pressing the gel with varying forces, the change in current is measured to analyze muscle signals. Figure 12 As shown in the figure. The resistance of this material as a function of temperature was measured as follows. Figure 13 As shown.

[0172] The circuit layout was designed in the early stages, and fabrication was completed using a photomask and the aforementioned nine-step process. Its transistor transfer characteristic curve is shown below. Figure 7 As shown, the inverse frequency response performance of the designed op-amp circuit was tested as follows: Figure 8 As shown, the circuit amplification is 180 times, with a gain as high as 45.1 dB, obtained through parameter extraction. The gain analysis of the active amplifier circuit with a single amplification unit in Example 3 under transient response test conditions is as follows. Figure 9 As shown. Gain analysis of the active amplifier circuit with a single amplification unit in Example 2 under frequency response test conditions. Figure 10 As shown. The gain analysis of the active amplifier circuit with a single amplification unit in Example 2 under transient response test conditions is as follows. Figure 11 As shown.

[0173] Experimental test data demonstrate that the multimodal collaborative detection system proposed in this invention exhibits significant technical advantages. Characteristic testing of the common-source amplifier circuit prepared in Example 1 revealed a gain of 31 dB. More importantly, when this amplifier circuit is integrated with the multimodal sensing electrodes, the overall system achieves a signal gain of 45.1 dB. Furthermore, due to the collaborative detection mechanism of mechanical and electrical signals, the system's accuracy in recognizing muscle movement intentions is improved. This improvement is not only reflected in signal gain but, more importantly, in the synergistic work of the mechanically sensitive material and high-density electrodes, achieving multidimensional capture of muscle activity characteristics and effectively overcoming the motion artifact interference problem commonly found in single electrical signal detection. Test results show that this integrated design not only reduces signal transmission loss but, more importantly, significantly improves the reliability of movement intention recognition through multimodal information fusion, providing a new technical solution for precise electromyography signal acquisition and application.

[0174] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0175] 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 method 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 multimodal biosignal sensor, characterized in that, include: Multiple active electrode units are arranged in a matrix to form an active high-density electrode array. The active high-density electrode array has interdigitated electrodes at its edge. Temperature and pressure materials are provided on the active high-density electrode array and the interdigitated electrodes. The active electrode unit includes an active amplifier circuit and two electrodes. The active amplifier circuit includes an amplifying device, a biasing device, a load device, and a negative feedback capacitor. The interdigitated electrode structure comprises six interlaced metal electrode structures.

2. The multimodal biosignal sensor according to claim 1, characterized in that, The source of the bias device is connected to the gate of the load device and one end of the negative feedback capacitor, respectively. The other end of the negative feedback capacitor is connected to the source of the load device and the drain of the amplifying device, respectively. The connection point of the negative feedback capacitor, the source of the load device, and the drain of the amplifying device is the output terminal of the bootstrap inverter circuit. The gate of the amplifying device is connected to one end of the electrode, the source of the amplifying device is grounded, and the drain of the load device, the gate of the bias device, and the drain of the bias device are all connected to an external power supply.

3. The multimodal biosignal sensor according to claim 2, characterized in that, The amplifying device, load device, and bias device are all thin-film transistors.

4. The multimodal biosignal sensor according to claim 3, characterized in that, The active electrode unit is formed by integrating the electrode and active amplifier circuit on a flexible substrate using thin-film transistor photolithography with metal oxide.

5. The multimodal biosignal sensor according to claim 4, characterized in that, The flexible substrate is a flexible polyimide substrate, and the flexible polyimide substrate includes, from bottom to top, a thin film transistor layer, a metal layer, an insulating layer, another metal layer, an insulating layer, and an electrode layer.

6. The multimodal biosignal sensor according to claim 5, characterized in that, The flexible polyimide substrate includes a polyimide film layer and a buffer layer, wherein the buffer layer comprises a silicon nitride film and a silicon dioxide film stacked sequentially from bottom to top.

7. The multimodal biosignal sensor according to claim 6, characterized in that, The thickness of the silicon nitride film is 300-400 nm, and the thickness of the silicon dioxide film is 200-300 nm.

8. A method for fabricating a multimodal biosignal sensor, applied to the multimodal biosignal sensor according to any one of claims 1-7, characterized in that, Includes the following steps: The raw materials for the fabrication of amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices, and switching devices in switching circuits are deposited to form an initial substrate; Photoresist is coated onto the initial substrate layer. After the coated photoresist is dried, the initial substrate layer is exposed in conjunction with the first mask to form the exposed initial substrate layer. After developing the exposed initial amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching device layer in the switching circuit, wet etching is performed to form the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching device in the switching circuit. The raw material for depositing an insulating layer on the lower electrode plate of a switching device in an amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device, and switching circuit is used to form an insulating layer. The gate metal molybdenum is deposited using PVD for amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices, and switching devices in the switching circuit. Then, the gate metal is patterned through photolithography and etching processes to form the desired gate structure. Using the active layer structure as a mask, an IGZO layer is deposited by CVD, and then the active layer is formed again by photolithography and etching processes; Molybdenum metal is deposited in the source and drain regions, and then photolithography and etching processes are used to form the source and drain metal electrodes, forming the lower plate of the feedback capacitor. Silicon dioxide is deposited by CVD as an insulating layer in the source / drain and gate regions. Contact holes are formed on the insulating layer using photolithography and etching processes; The precursor is annealed to form amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices, and switching devices in switching circuits. The raw materials for preparing the etching layer are chemically deposited onto the active layer to form the initial etching layer; Photoresist is coated onto the initial etched layer. After the coated photoresist is dried, the initial etched layer is exposed with the third mask to form the exposed initial etched layer. After the initial etched layer is exposed, it is developed and then dry etched to reserve gaps between the active layer of the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device and the corresponding SD drain and source, one end of the feedback capacitor, and the interconnection between the gate of the amplifier and the feedback circuit device, thus forming an etched layer. The raw materials for fabricating amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices, and the source and drain electrodes of switching devices in the switching circuit, as well as the lower electrode plate of the feedback capacitor, are magnetron sputtered onto an etched layer. This achieves interconnection between the active layer of the amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices, and the switching devices in the switching circuit and their corresponding SD drain and source electrodes, between the gate of the bias circuit device and the gate of the amplifier circuit device, between the source of the startup circuit device and the drain of the bias circuit device, between the drain of the electrostatic protection circuit device and the source of the switching device in the switching circuit, between the source of the switching device in the switching circuit and the gate of the amplifier circuit device, between the upper electrode plate of the feedback capacitor and the gate of the amplifier circuit device, and between the feedback device and the amplifier circuit device, forming an SD electrode film. Photoresist is coated onto the SD electrode film. After the coated photoresist is dried, the SD electrode film is exposed using a fourth mask to form the exposed SD electrode film. After exposure, the SD electrode film is developed and then etched to form the source and drain of the switching devices in the amplifier circuit, feedback circuit, electrostatic protection circuit, startup circuit, bias circuit, and switching circuit, as well as the lower plate of the capacitor. The raw materials for preparing the second etch protective layer are chemically deposited on the amplifier circuit device, feedback circuit device, electrostatic protection circuit device, startup circuit device, bias circuit device and switching device in the switching circuit to form an initial barrier layer; Photoresist is coated onto the initial barrier layer. After the coated photoresist is dried, the initial barrier layer is exposed using a fifth mask to form the exposed initial barrier layer. After exposure, the initial barrier layer is developed and then dry-etched to form a barrier layer. Molybdenum is vapor-deposited onto the barrier layer to form the initial molybdenum plating layer; Photoresist is coated onto the initial molybdenum plating layer. After the coated photoresist is dried, the initial molybdenum plating layer is exposed using the sixth mask to form the exposed initial molybdenum plating layer. After exposure, the initial molybdenum plating layer is developed and then etched to form the molybdenum plating layer and the upper electrode of the negative feedback capacitor. A portion of the molybdenum plating layer connects the amplifier circuit devices, feedback circuit devices, electrostatic protection circuit devices, startup circuit devices, bias circuit devices, and switching devices in the switching circuit to each other, and connects the upper plate of the negative feedback capacitor to the drain of the amplifier circuit devices. A portion of the molybdenum plating layer is connected to the connection point where the source of the amplifier circuit device is connected to the upper plate of the negative feedback capacitor and the drain of the feedback circuit device, serving as the output terminal. A portion of the molybdenum plating layer is connected to the source of the amplifier circuit device and then grounded; The raw materials for preparing the third etch protective layer are chemically deposited on the upper electrode plate to form the third barrier layer; Photoresist is coated on the third barrier layer. After the coated photoresist is dried, the initial barrier layer is exposed in conjunction with the seventh mask to form the exposed third etched layer. After exposure, the third etched layer is developed and then dry-etched to form the third etched protective layer. Titanium is vapor-deposited onto the barrier layer to form the initial titanium layer; Photoresist is coated onto the initial titanium plating layer. After the coated photoresist is dried, the initial titanium plating layer is exposed using the eighth mask to form the exposed initial titanium plating layer. After exposure, the initial titanium plating layer is developed and then wet-etched to form the electrode layer. The raw materials for preparing the encapsulation layer are chemically vapor deposited onto the plated titanium layer to form the initial encapsulation layer; Photoresist is coated onto the initial encapsulation layer. After the coated photoresist is dried, the initial encapsulation layer is exposed using the ninth mask to form the exposed initial encapsulation layer. After exposure, the initial encapsulation layer is developed and then dry-etched to form an encapsulation layer, resulting in an active amplifier circuit.

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