Flexible wearable HD-sEMG sensor and preparation method thereof

Abstract

The invention provides a flexible wearable HD-sEMG sensor and a preparation method thereof, and the sensor comprises an array electrode structure which comprises a plurality of sub-array electrode structures which are distributed in different areas of the surface of the sensor, each sub-array electrode structure comprises a plurality of electrodes which are connected through a plurality of layers of stretchable special-shaped structure wires, and the rear ends of the electrodes are connected with gating bonding pads; the gel electrode structure comprises a plurality of gel electrodes, the gel electrodes are located on the electrode surface of the array electrode structure, and materials for forming the gel electrodes comprise an electromagnetic shielding material and a thickener; the gel electrode structure is used for being in contact with the skin to obtain a bio-electricity signal, and the sensor is firmly attached to the skin. The sensor can meet the requirements for chip selection of different individual physiological structure requirements and gating of different acquisition devices, is firmly attached to the skin and can recognize micro action activation signals.

Description

Technical Field

[0001] The present invention relates to the technical field of HD-sEMG sensors, and in particular to a flexible wearable HD-sEMG sensor and a preparation method thereof. Background Art

[0002] The conductors of HD-sEMG sensors currently under research include metals such as Au, Ag, and Cu, as well as carbon materials, graphene, and polymer conductive materials. The substrates used for the supporting and encapsulating conductors include polyimide (PI), Ecoflex, PDMS, Silbione, and PET film. HD-sEMG electrodes utilize Au, Ag, Cu, Ag / AgCl, carbon materials, graphene, conductive polymers, and viscous conductive materials. Sensor fabrication processes include photolithography, laser cutting, screen printing, inkjet printing, and 3D printing.

[0003] For conductors and electrodes, some metal materials offer excellent ductility, enhancing sensor flexibility. However, excessive stretching is crucial, as it can lead to breakage and high electrode contact resistance. Carbon materials and graphene can reduce interference from ambient electromagnetic wave coupling, but they lack flexibility and are often incorporated into polymers as conductive materials. Furthermore, their contact resistance is high. Polymer conductive materials have also been increasingly used as conductors and electrodes in recent years, but their adhesion to the substrate remains a key challenge, as it can easily cause breakage. All dry electrodes are susceptible to micro-displacement with the skin when deformed, resulting in significant motion artifacts that can drown out the signal in noise. Conductive pastes and bandages are commonly used to mitigate these motion artifacts. Finally, it is important to emphasize that the individual electrode points in high-density electrodes are inherently small, requiring a stronger adhesive coating to prevent displacement from the skin, placing high demands on the conductive paste.

[0004] As for the substrate, PI material has a certain flexibility when it is thin, but lacks stretchability itself. It has stretchability after being structured; Ecoflex, PDMS, and silbione are inherently super-flexible and stretchable, and are super-elastic materials, but there is a problem of strong bonding between them and the wires and electrode materials; PET film is flexible and stretchable, but has poor toughness and is easy to break.

[0005] Photolithography requires a clean room, is time-consuming, and involves complex processes, making it less suitable for mass production. This process also hinders the production of thicker HD-sEMG sensors. Thinner sensors can be adhered to their shape but cannot be reused. Laser cutting is a quick and easy way to produce sensors, suitable for cuttable materials, but packaging considerations are necessary. Screen printing is also a simple method, but it has limitations on wire width and requires certain conductive materials. Furthermore, bonding the wires to the substrate presents a challenge. Inkjet printing and 3D printing, like screen printing, only eliminate the line width restriction; other challenges remain. In comparison, inkjet printing places higher demands on the substrate, and the impact of inkjet intensity on the substrate also needs to be considered.

[0006] After searching, the Chinese invention patent with application publication number CN108553102A discloses a flexible, stretchable multi-channel convex surface muscle electrode and its preparation method. The sensor in this patent is ultra-thin and has low contact impedance. It relies on weak van der Waals forces to attach to the skin and is prone to entanglement.

[0007] A Chinese invention patent application with publication number CN113974635A discloses a wearable HD-sEMG sensor and its preparation method. In this patent, the sensor relies on high-temperature resistant sticky conductive gel electrodes to be attached to the skin, which has shortcomings in adhesion stability.

[0008] The Chinese invention patent application with publication number CN111134671A discloses a flexible multi-channel repeatable array HD-sEMG sensor and its preparation. Like the two aforementioned patents, the HD-sEMG sensor is an HD-sEMG sensor. However, the design is not very reasonable due to the differences in physiological structures between individuals, especially the use of the same-sized sensor for the neck and facial areas. Summary of the Invention

[0009] In view of the defects in the prior art, the purpose of the present invention is to provide a flexible wearable HD-sEMG sensor and a preparation method thereof.

[0010] According to one aspect of the present invention, there is provided a flexible wearable HD-sEMG sensor, comprising:

[0011] An array electrode structure, comprising a plurality of sub-array electrode structures distributed in different areas of the sensor surface, each sub-array electrode structure comprising a plurality of electrodes connected by multi-layer stretchable special-shaped structure wires, the rear ends of the electrodes being connected to selectable pads;

[0012] The gel electrode structure includes several gel electrodes, which are located on the electrode surface of the array electrode structure. The materials forming the gel electrodes include electromagnetic shielding material and viscosity. The gel electrode structure is used to contact the skin to obtain bioelectric signals and firmly attach the sensor to the skin.

[0013] Optionally, in the sub-array electrode structure, the closer the electrode is to the center of the region, the fewer layers of wire distribution therein.

[0014] Optionally, the packaging of the electrodes in the sub-array electrode structure adopts a stretchable special-shaped structure.

[0015] Optionally, the interconnection and packaging between the electrodes in the sub-array electrode structure are manufactured using a flexible circuit board process; a gap is provided between the electrode and the surrounding packaging, and the gel electrode is embedded in the gap.

[0016] Optionally, the radius of the electrode is 0.3-1.2 mm.

[0017] Optionally, the electrode is a Cu / Au electrode, and the electrode is circular.

[0018] Optionally, the solvent for forming the gel electrode is a mixture of water and glycerol, with the ratio of water to glycerol being 1:0 to 0:1.

[0019] Optionally, the viscous agent is agar, and the ratio of the viscous agent to the solvent is 1:10-1:10.

[0020] Optionally, the material forming the gel electrode includes one or more conductive materials, and the volume ratio of the conductive material to the solvent is 0:1 to 10:1.

[0021] According to another aspect of the present invention, a method for preparing the above-mentioned flexible wearable HD-sEMG sensor is provided, the method comprising:

[0022] The array electrode structure is made using FPC technology;

[0023] Provide gel electrode solution;

[0024] The gel electrode solution is dripped onto the electrodes of the array electrode structure to make gel electrodes and form a gel electrode structure.

[0025] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0026] 1. The present invention can select a suitable sensor area for testing based on individual adaptability; by connecting the back end of the electrode to a selectable pad, a selection channel is provided for a portable HD-sEMG hardware acquisition system (such as the 64-channel portable electromyography acquisition system of the OT series), thereby realizing portable system acquisition.

[0027] 2. The present invention uses single-layer to multi-layer wires with special-shaped structures to make the sensor have better stretchability;

[0028] 3. The conductive gel electrode of the present invention is added with a thickener, so that the sensor can be firmly attached to the skin by virtue of its excellent super viscosity without any adhesive aid. The sensor electrode point does not move when it is stretched to a certain extent, and can be used repeatedly.

[0029] 4. The sensor prepared by the present invention contains electromagnetic shielding materials that can effectively shield electromagnetic interference from the surrounding environment, has ultra-low contact impedance, greatly reduced noise, can identify tiny motion activation signals, can obtain good signal quality, and is comfortable to wear. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0031] Figure 1 Schematic diagram of the structure of a flexible wearable HD-sEMG sensor in one embodiment of the present invention;

[0032] Figure 2 Schematic diagram of a flexible wearable HD-sEMG sensor according to an embodiment of the present invention;

[0033] Figure 3 A schematic plan view of an array electrode structure according to an embodiment of the present invention;

[0034] Figure 4 A schematic structural diagram of an array electrode structure in one embodiment of the present invention;

[0035] Figure 5 A schematic diagram of a set of sensors applicable to different physiological structures according to an embodiment of the present invention;

[0036] Figure 6 Schematic diagram of a process for preparing a gel electrode solution according to one embodiment of the present invention;

[0037] In the figure: 1 is the array electrode structure, 2 is the gel electrode structure. DETAILED DESCRIPTION

[0038] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0039] Reference Figure 1-Figure 4 A flexible wearable HD-sEMG sensor provided by an embodiment of the present invention includes an array electrode structure and a gel electrode structure. The array electrode structure includes multiple sub-array electrode structures distributed in different areas of the sensor surface. The distribution areas of the multiple sub-array electrode structures are determined according to the physiological structures of different individuals. The sub-array electrode structures in each area can be set independently of each other. Each sub-array electrode structure includes multiple electrodes connected by multi-layer stretchable special-shaped structure wires. The rear end of the electrode is connected to an optional pad, which can realize portable system acquisition; the gel electrode structure includes multiple gel electrodes, which are located on the electrode surface of the array electrode structure. The material forming the gel electrode includes electromagnetic shielding material and viscosity; the gel electrode structure is used to contact the skin to obtain bioelectric signals and firmly attach the sensor to the skin.

[0040] The array electrode structure is the core framework of the sensor. It is highly integrated and formed by four layers of special-shaped structural wiring. It is convenient for forming large-area flexible wearable devices and is used to support the entire large-area flexible wearable device. The array electrode structure has the characteristics of multi-region distribution, flexible chip selection, and optional selection, ensuring the flexible partition layout, stretchability and excellent reusability of the wearable device, meeting the chip selection needs of different individual physiological structures, and different acquisition devices can be appropriately selected.

[0041] The gel electrode structure is located on the surface of the metal electrode of the array electrode and is used to contact the skin to obtain bioelectric signals. The gel electrode has super-sticky electromagnetic shielding and conductivity, which firmly attaches the sensor to skin with high curvature, such as the area between the mandible and the neck. This allows the sensor to undergo large deformation without relative displacement between the electrode and the skin, which would cause serious motion artifacts. This meets the needs of swallowing, speech, and other movements. In addition, the doping of electromagnetic shielding material greatly reduces the noise of the collected signal (baseline noise, short-circuit noise, and baseline drift) (lower than Ag / AgCl), and can identify small motion activation signals. Compared with relying on high-temperature resistant sticky conductive gel electrodes to be attached to the skin, the gel electrode structure in the embodiment of the present invention has stronger adhesion and more stable adhesion.

[0042] The sensor in the embodiment of the present invention is designed for the area above the shoulders, including the face, jaw, and neck. The sensors with different designs in multiple areas form a set of sensors to fully fit the neck and face areas of different individuals and are suitable for different individual physiological structures, such as Figure 5As shown, a set of sensors can be changed according to individual chip selection to meet the physiological structure needs of different individuals, and a channel with fewer channels can be used when hardware support is insufficient. An HD-sEMG sensor with flexible chip selection and selectable channels based on a flexible partition layout is designed to match the range of skin deformation during swallowing and speech activities. By adding viscosity and electromagnetic shielding materials, a more excellent super-viscous electromagnetic shielding conductive gel electrode is designed, so that the sensor undergoes large deformation without relative displacement between the electrode and the skin to cause serious motion artifacts, meeting the needs of swallowing, speech and other movements. In addition, the doping of electromagnetic shielding materials greatly reduces the acquisition signal noise (baseline noise, short-circuit noise and baseline drift) (lower than Ag / AgCl), which can identify tiny movement activation signals, thereby solving the problem of high-quality acquisition of HD-sEMG signals for big data.

[0043] The flexible wearable HD-sEMG sensor in the embodiment of the present invention can of course also be used on the arms, thighs, face and back, and has the advantages of good signal collection quality, easy and comfortable wearing, etc.

[0044] Exemplarily, each sub-array electrode structure includes four layers of electrodes, such as Figure 4 As shown, from top to bottom, it includes a top electrode, a second electrode, a third electrode and a bottom electrode. The electrodes can be Cu electrodes. The electrode layers are insulated by insulating materials such as PI. The upper surface of the sub-array electrode structure is provided with a top surface covering layer, and the lower surface is provided with a bottom covering layer.

[0045] It should be noted that in some other embodiments, the number of layers in each sub-array electrode structure can be set to other numbers. This can ensure that multiple columns of special-shaped structures can be arranged spatially, avoiding the situation where all of them are on one layer, which would affect the stretchability of the special-shaped structures. As the electrode density increases, that is, the number of electrode points increases, the number of layers can be set to other numbers, such as 6 or 8 layers.

[0046] In some embodiments, the closer the electrode is to the center of the region in the sub-array electrode structure, the fewer layers of wires are distributed in the special-shaped structure, so that the flexibility and stretchability of the region near the center are better than those of other regions. Figure 5 In the figure, the farther the sensor wiring around the lip is from the pad, the fewer layers the wires are distributed.

[0047] In some embodiments, in addition to the wire interconnections between electrodes in the sub-array electrode structure, the insulating package also adopts a stretchable special-shaped structure, such as Figure 4 The top surface covering film and the bottom surface covering film are packaged to form a serpentine structure.

[0048] In the above embodiments, the interconnections or packages between electrodes in the array electrode structure can be simple rectangular or irregularly shaped. The irregular shape can be serpentine, spiral, or any other stretchable irregular structure. The irregular structure can be one-dimensional, two-dimensional, or multi-dimensional.

[0049] In order to make the sensor fit the skin better and collect high-quality signals, for example, a serpentine structure with different width packaging is used in the array electrodes with flexible chip selection and selectable distribution in multiple regions of the sensor, such as Figure 4 shown.

[0050] In some embodiments, the interconnections and packaging between the electrodes in the sub-array electrode structure are fabricated using flexible circuit board technology, with dimensions and widths within the process range. A gap is provided between the electrodes and the surrounding packaging, into which the gel electrodes are embedded. The size of this gap can be adjusted as needed. This gap between the electrodes and the packaging in the array electrode structure allows the sensor to be securely attached to the super-sticky, electromagnetically shielding, conductive gel electrodes.

[0051] Depending on the purpose of signal acquisition, the sensor can selectively acquire signals more deeply or within a larger range. The size of the electrodes in the sub-array electrode structure is determined according to the target requirements of the signal acquisition. In some embodiments, the radius of the electrode is 0.3-1.2 mm, which can achieve high-density surface electromyography signal acquisition.

[0052] In some embodiments, the electrodes are circular Cu / Au electrodes. The circular Cu / Au electrodes in the array electrode structure prevent oxidation and facilitate subsequent bonding with the viscous gel. A certain gap exists between the circular Cu / Au electrodes and the surrounding insulating package, allowing for the insertion of a super-sticky, electromagnetically shielding, conductive gel electrode, effectively securing it to the Cu / Au electrodes.

[0053] It should be noted that in some other embodiments, electrodes of other types and shapes may be used, and the present invention is not limited thereto.

[0054] In some embodiments, the solvent used to form the gel electrode is a mixture of water and glycerol. The glycerol allows the sensor to continue functioning in harsh environments. The water-to-glycerol ratio is 1:0 to 0:1, preferably 1:1. This ratio provides good water retention, which helps extend the life of the gel electrode.

[0055] The ultra-viscous electromagnetic shielding conductive gel electrode contains materials that affect gel fluidity, such as a thickener. The ratio of the thickener to the solvent is determined by the properties of the thickener itself and the solvent system. In some embodiments, the thickener is agar, and the ratio of the thickener to the solvent is 1:10-1:10.

[0056] In an embodiment of the present invention, a thickener is added to the self-adhesive gel to increase the viscosity, so that the sensor can be firmly fixed on the skin solely by relying on its own super-sticky electromagnetic shielding conductive gel electrodes. The sensor electrode points do not move when subjected to a certain amount of stretching, and can be used repeatedly, eliminating motion artifacts.

[0057] In some embodiments, the material forming the gel electrode includes one or more conductive materials, and the volume ratio of the conductive material to the solvent is 0:1 to 10:1. At the same time, doping can appropriately improve the conductivity, especially the conductive material with electromagnetic interference, that is, the conductive material also serves as an electromagnetic shielding material, which can improve the sensor's anti-electromagnetic interference ability.

[0058] To achieve low contact impedance and anti-electromagnetic shielding effect, in some optional embodiments, a mixed conductive doping solution of PEODT:PSS (poly 3,4-ethylenedioxythiophene / polystyrene sulfonate) and MXene (ammonium persulfate) is used in the super-viscous electromagnetic shielding conductive gel electrode, and the volume ratio of the two is 0:10-10:0, and the volume ratio of the sum of the two to the total solvent is 0:1 to 20:1.

[0059] In some optional embodiments, NAGA (N-acryloylglycineamide) and AMPS (2-acrylamide-2-methylpropanesulfonic acid) are used as the gel skeleton in the super-sticky electromagnetic shielding conductive gel electrode, the ratio of NAGA to AMPS is 1:0-0:1, and the ratio with the solvent is 1:5-1:10.

[0060] An embodiment of the present invention provides a method for preparing the above-mentioned flexible wearable HD-sEMG sensor, the method comprising:

[0061] S1. Using FPC technology (Flexible Printed Circuit) to make array electrode structure;

[0062] Specifically, the method includes the following steps:

[0063] S11. Design the circuit diagram and layout of the electrode array and determine the FPC material and number of layers;

[0064] S12, importing the circuit diagram and layout into the FPC manufacturing equipment;

[0065] S13. Perform operations such as cutting, drilling, electroplating, dry film lamination, exposure, development, etching, and peeling on the FPC material to achieve the layout of the electrode array.

[0066] In the embodiment of the present invention, the electrode array is manufactured by using FPC technology. The FPC process is mature and efficient, and the finished product has excellent reusability.

[0067] S2. Providing a gel electrode solution; specifically, adding a viscosity agent, an electromagnetic shielding material, a conductive material, an initiator, etc. to a solvent in a predetermined order to form a gel electrode solution;

[0068] For example, Figure 6 Schematic diagrams of the preparation processes for three gel electrode solutions are shown. Chain 1 uses water and glycerol as solvents, vortexes, and heats in a hot water bath. Then, a thickener is added, vortexes, and heats in a hot water bath. PEODT:PSS and MXene are added, vortexes, and cooled to room temperature. NAGA and AMPS are then added, followed by vortexing and initiators APS and TEMED to promote gelation, resulting in a gel electrode solution. Chain 3 also produces a gel electrode solution by changing the order of addition: PEODT:PSS and MXene are added first, followed by NAGA and AMPS, then the thickener, and finally the initiators APS and TEMED.

[0069] Figure 6 Chain No. 2 is a partial production flow chart of the super-viscous electromagnetic shielding conductive gel of a preferred embodiment of the present invention. Chain No. 2 changes the order of adding materials to first adding the viscosity agent, then adding PEODT:PSS and MXene, then adding NAGA and AMPS, and finally adding the initiators APS and TEMED. The overall process of obtaining the gel is more robust, which can ensure to the greatest extent that the viscosity agent is truly dissolved and mixed evenly, thereby avoiding affecting the conductivity of the gel.

[0070] S3. Making gel electrodes on the electrodes of the array electrode structure. Specifically, the gel electrode solution can be dripped onto the electrodes of the array electrode structure using a needle to form a gel electrode structure.

[0071] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various modifications or variations within the scope of the claims without affecting the essence of the present invention. The above preferred features may be used in any combination as long as they do not conflict with each other.

Claims

1. A flexible wearable HD-sEMG sensor, characterized in that: include: An array electrode structure, comprising a plurality of sub-array electrode structures distributed in different areas of the sensor surface, each sub-array electrode structure comprising a plurality of electrodes connected by multi-layer stretchable special-shaped structure wires, the rear ends of the electrodes being connected to selectable pads; The gel electrode structure includes several gel electrodes, which are located on the electrode surface of the array electrode structure. The materials forming the gel electrodes include electromagnetic shielding material and viscosity. The gel electrode structure is used to contact the skin to obtain bioelectric signals and firmly attach the sensor to the skin.

2. The flexible wearable HD-sEMG sensor according to claim 1, characterized in that In the sub-array electrode structure, the closer the electrode is to the center of the region, the fewer the layers of wire distribution are.

3. The flexible wearable HD-sEMG sensor according to claim 1, characterized in that The packaging of the electrodes in the sub-array electrode structure adopts a stretchable special-shaped structure.

4. The flexible wearable HD-sEMG sensor according to claim 1, characterized in that The interconnection and packaging between the electrodes in the sub-array electrode structure are manufactured using a flexible circuit board process; a gap is provided between the electrodes and the surrounding packaging, and the gel electrode is embedded in the gap.

5. The flexible wearable HD-sEMG sensor according to claim 1, characterized in that The radius of the electrode is 0.3-1.2 mm.

6. The flexible wearable HD-sEMG sensor according to claim 1, characterized in that The electrodes are Cu / Au electrodes, and are circular.

7. The flexible wearable HD-sEMG sensor according to claim 1, characterized in that The solvent for forming the gel electrode is a mixture of water and glycerol, and the ratio of water to glycerol is 1:0 to 0:

1.

8. The flexible wearable HD-sEMG sensor according to claim 7, characterized in that The viscous agent is agar, and the ratio of the viscous agent to the solvent is 1:10-1:

10.

9. The flexible wearable HD-sEMG sensor according to claim 7, characterized in that The material forming the gel electrode includes one or more conductive materials, and the volume ratio of the conductive material to the solvent is 0:1 to 10:

1.

10. A method for preparing the flexible wearable HD-sEMG sensor according to any one of claims 1 to 9, characterized in that: include: The array electrode structure is made using FPC technology; Provide gel electrode solution; The gel electrode solution is dripped onto the electrodes of the array electrode structure to make gel electrodes and form a gel electrode structure.

Images