Flexible array type stretchable electronic skin and preparation method thereof

Abstract

The invention discloses a flexible array type stretchable electronic skin and a preparation method thereof, is used for collecting surface electromyogram signals of a human body, and relates to the technical field of flexible electronics and bioelectricity detection. The stretchable electronic skin comprises a supporting layer, a substrate layer, an electromyographic signal transmission layer and a hydrogel interface layer, the supporting layer is made of a single-sided viscous material with certain physical rigidity and provides necessary structural rigidity; the substrate layer and the supporting layer are bonded and fixed; the electromyographic signal transmission layer is adhered to the surface of the substrate layer, and the electromyographic signal transmission layer is made of a flexible PCB (Printed Circuit Board) material; the hydrogel interface layer is arranged on the surface of an electrode contact of the electromyographic signal transmission layer and serves as a conducting medium between the electronic skin and the human epidermis. The electronic skin provided by the invention has good myographic signal to noise ratio, reusability, fitting performance and tensile property.

Description

Technical Field

[0001] This invention belongs to the fields of flexible electronics technology and bioelectric detection technology, specifically relating to a flexible array-type stretchable electronic skin and its preparation method. Background Technology

[0002] Stroke, brain injury, brain tumors, or neurodegenerative diseases such as Alzheimer's disease (AD) can damage language-related areas, leading to impaired speech. With advancements in medical technology, if the facial and jaw muscles of patients with these speech disorders are intact and healthy, a non-verbal pathway can be provided. This allows patients to recognize and process silent speech through facial electromyography (EMG) signals combined with a silent speech interface, synthesizing speech from EMG signals in real time for normal communication. Electronic skin, as an EMG signal acquisition device, plays a crucial role in these medical applications. It primarily conducts and collects the physiological electrical signals—the weak potential changes generated by muscles during movement—using metal electrodes.

[0003] Existing surface electromyography (EMG) signal acquisition systems often suffer from poor adhesion and low repeatability. For example, the "fully flexible array-type EMG electrode patch" disclosed in invention patent application CN118542676A and the "swallowing monitoring system based on EMG and pressure sensing" disclosed in invention patent CN116942099B both use silver sheet / silver chloride electrodes or screen-printed conductive silver paste to prepare electrodes in the EMG signal acquisition and transmission modules. Because the outer layer of the electrodes in these devices is directly composed of a conductive material with unstable physical adhesion, the conductive material is easily peeled off during cleaning, making it impossible to clean and reuse after one use, which greatly increases the cost. Furthermore, although the "epidermal hydrogel hybrid electronic system for electromyography monitoring" disclosed in invention patent CN117338306B achieves rapid disassembly of the hydrogel interface layer through ultraviolet irradiation and has a certain degree of reusability, the integrated structural design limits the adhesion of the electronic skin. During skin movement, deformation can easily cause delamination between the electrode and the skin interface, and the electrode acquisition signal is directly affected by external interference, making it impossible to achieve long-term high-fidelity sEMG signal acquisition. Summary of the Invention

[0004] To address at least one of the problems existing in the prior art, this invention utilizes flexible PCB materials to develop a high-fidelity, reusable, flexible array-type stretchable electronic skin. This invention will provide superior industrial surface electromyography signal acquisition technology support for future medical silent speech conversion applications and other applications based on electromyography signals.

[0005] To achieve the objective of this invention, a flexible array-type stretchable electronic skin is provided, comprising a support layer, a base layer, an electromyography signal transmission layer, and a hydrogel interface layer.

[0006] The support layer is constructed of a single-sided adhesive material with a certain physical rigidity, providing the necessary structural rigidity;

[0007] The base layer and the support layer are bonded and fixed together;

[0008] The electromyographic signal transmission layer is adhered to the surface of the substrate layer, and the electromyographic signal transmission layer is made of flexible PCB material;

[0009] A hydrogel interface layer is disposed on the electrode contact surface of the electromyography signal transmission layer, serving as a conductive medium between the electronic skin and the human epidermis.

[0010] A further preferred embodiment of the present invention is that the thickness of the support layer is 1 mm.

[0011] A further preferred embodiment of the present invention is that the thickness of the substrate layer is 2 mm.

[0012] A further preferred embodiment of the present invention is that the single-sided adhesive material can be a medical dressing or flexible silicone, or other single-sided adhesive materials with long-term biocompatibility.

[0013] A further preferred embodiment of the present invention is that the substrate layer is prepared from one of polydimethylsiloxane or polyurethane film, providing surface adhesion.

[0014] A further preferred embodiment of the present invention is that the hydrogel interface layer is made of a polyampholyte hydrogel raw material.

[0015] A further preferred embodiment of the present invention is that the electromyography signal transmission layer includes electrode contacts, wires, and an outer protective film. The wires are used for the conduction of surface electromyography signals. The outer protective film wraps around the wires. The wires are arranged in a tree-like or V-shaped pattern. Each branch wire has an electrode contact at one end, and the other ends converge to form an FPC interface. Preferably, the wires are made of copper.

[0016] A further preferred embodiment of the present invention is that the copper conductor has a wire width of 1 mm, with each pair of conductors arranged independently side by side, and the electrode contacts connected to them are also separated from each other. The independence of the conductors and the separation of the electrode contacts allow for strain decoupling between the electrodes of different channels and the ribbon cable, providing structural stretchability for the non-stretchable flexible PCB material.

[0017] A further preferred embodiment of the present invention is as follows: the electromyography (EMG) signal transmission layer comprises electrode contacts, copper wires, and polyimide. The copper wires are used for the conduction of surface EMG signals. The copper wires are encapsulated by the polyimide substrate, which protects the copper wires from interference. The electrode contacts comprise conductive material sheets, one side of which is coated with a non-conductive material. Preferably, the electrode contacts comprise copper foil sheets, one side of which is coated with polyimide.

[0018] A further preferred embodiment of the present invention is that: in the electromyography signal transmission layer, the distance between any adjacent electrode contacts is 10mm to 20mm; the electrode contacts are circular with a diameter of 3mm to 5mm.

[0019] A further preferred embodiment of the present invention is that the flexible array-type stretchable electronic skin adopts a V-shaped design.

[0020] A further preferred embodiment of the present invention is that the polyampholyte hydrogel used in the hydrogel interface layer is obtained by polymerization of sodium 4-styrene sulfonate, acryloyloxyethyltrimethylammonium chloride and α-ketoglutaric acid, or by polymerization of sodium 4-styrene sulfonate, N,N,N-trimethyl-3-(2-methylallylamino)-1-propanium chloride and α-ketoglutaric acid.

[0021] This invention also provides a method for preparing a flexible array-type stretchable electronic skin, comprising the following steps:

[0022] 1) Cut a single-sided adhesive material with a certain physical rigidity into the required shape, such as a U-shape, to make a support layer;

[0023] 2) Prepare a silicone film from polydimethylsiloxane or polyurethane film to form a base layer, and attach the support layer under the base layer;

[0024] 3) Flexible PCB materials are prepared by using polyimide as the base film and top film, and copper wires as the intermediate conductive material;

[0025] 4) Electrode contacts are obtained on the flexible PCB material using laser penetration and copper electroplating processes to form the electromyographic signal transmission layer, and the electromyographic signal transmission layer is laminated and embedded with the substrate layer;

[0026] 5) Coat the electrode contact surface in the electromyography signal transmission layer with a polyampholyte hydrogel raw material, and use ultraviolet light to initiate polymerization to form a hydrogel cover, thereby obtaining the flexible array-type stretchable electronic skin.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1) The electromyography signal transmission layer of the present invention uses a flexible PCB material, which has high stability, simple preparation process, and is easy to arrange. It can also be reused after the hydrogel interface layer is washed after the surface electromyography signal is collected.

[0029] 2) The tree-shaped or V-shaped arrangement of the electromyography signal transmission layer of the present invention can avoid motion artifacts caused by complex curved skin and electrode contacts during muscle movement through better fit, making the collected surface electromyography signals more stable and having a better signal-to-noise ratio.

[0030] 3) The electrode contacts of the electromyography signal transmission layer of the present invention are located in pairs of independent lines, which avoids the problem of low fidelity caused by multiple electrode contacts collecting electromyography signals from a single muscle group when the overall electrode lines are laid out. Attached Figure Description

[0031] Figure 1 This is a three-dimensional structural schematic diagram of a flexible array-type stretchable electronic skin applied to the face, provided as an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of a planar structure of a flexible array-type stretchable electronic skin electromyography signal transmission layer applied to the face, provided as an embodiment of the present invention.

[0033] Figure 3 This is a flowchart illustrating the fabrication process of a flexible array-type stretchable electronic skin for the face, provided as an embodiment of the present invention.

[0034] Figure 4 This is a schematic diagram of a planar structure of a flexible array-type stretchable electronic skin support layer and a base layer for the face, provided in an embodiment of the present invention.

[0035] Figure 5 This is a diagram of electrode contact points for a flexible array-type stretchable electronic skin electromyography signal transmission layer on the face, provided as an embodiment of the present invention.

[0036] Figure 6 This is a schematic diagram of facial muscle groups acting on a flexible array of stretchable electronic skin provided in an embodiment of the present invention.

[0037] Figure 7 This is a visual representation of the signal acquisition results of a flexible array of stretchable electronic skin on the face, provided by an embodiment of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0039] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", "vertical", "side", "cut", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0040] In the description of this invention, unless otherwise explicitly defined, terms such as arrangement, installation, and connection should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0041] In the description of this invention, the flexible array-type stretchable electronic skin acting on the facial muscles is only one of many embodiments and does not limit the scope of the invention to other muscle groups. Any changes, modifications, substitutions, combinations or simplifications made based on the spirit and principle of the technical solution of this invention shall be equivalent substitutions. As long as they meet the purpose of this invention and do not deviate from the technical principle of the flexible array-type stretchable electronic skin of this invention, they shall fall within the protection scope of this invention.

[0042] Please refer to Figure 1 , Figure 1 This is a three-dimensional structural diagram of a flexible array-type stretchable electronic skin for the face, provided by an embodiment of the present invention. The flexible array-type stretchable electronic skin provided by this embodiment of the present invention comprises, from top to bottom: a double-layered structure 11 of a support layer and a base layer, an electromyographic signal transmission layer 12, and a hydrogel interface layer 13. The double-layered structure 11 of the support layer and the base layer includes a support layer and a base layer. The support layer is constructed of a single-sided adhesive material with a certain physical rigidity, providing necessary structural rigidity. The base layer is bonded and fixed to the support layer; the electromyographic signal transmission layer is adhered to the surface of the base layer and is made of flexible PCB material; the hydrogel interface layer is disposed on the surface of the electrode contacts of the electromyographic signal transmission layer.

[0043] In one embodiment of the invention, the single-sided adhesive material is a medical dressing or flexible silicone; in other embodiments, other single-sided adhesive materials with long-term biocompatibility may also be used; the base layer is prepared from either polydimethylsiloxane or polyurethane film to provide surface adhesion.

[0044] In one embodiment of the present invention, the double-layered structure 11 of the support layer and the base layer is designed in a U-shape, which can maintain the necessary rigidity when the electronic skin is deployed and can prevent the extension performance of the electronic skin from being affected by cutting it into a closed loop. The electromyography signal transmission layer 12 is made of flexible PCB material, using copper wire / copper foil as an excellent conductive substrate and polyimide film as an external protective film, changing the traditional perception that surface electromyography signal acquisition devices are consumables and cannot be reused, and realizing the reusable function of the electronic skin. The hydrogel interface layer 13 is made of polyamplitude electrolyte hydrogel. Polyamplitude electrolyte hydrogel has good charge transfer performance and biocompatibility, which allows the hydrogel interface layer 13 to be safely attached to the human epidermis 14 and stably collect surface electromyography signals.

[0045] In one embodiment of the present invention, the thickness of the support layer is 1 mm and the thickness of the base layer is 2 mm.

[0046] Please refer to Figure 2 , Figure 2 This is a schematic diagram of a planar structure of an electromyography (EMG) signal transmission layer for a flexible, array-type, stretchable electronic skin applied to the face, provided by an embodiment of the present invention. The EMG signal transmission layer 12 includes electrode contacts 21, copper wires 22, and an FPC interface 23. The electrode contacts 21 include a conductive material sheet, one side of which is coated with a non-conductive material. Preferably, both sides of the copper wires 22 are wrapped with a polyimide substrate, which protects the copper wires from interference. The electrode contacts 21 include a circular piece made of copper foil, one side of which is coated with polyimide (in other embodiments, the copper foil can be replaced with any other conductive material, and the polyimide can be replaced with a non-conductive material with flexibility, toughness, and a certain structural strength). The side of the electrode contact 21 without polyimide can directly contact the human epidermis 14. Based on the characteristics of facial muscle groups, the electromyography (EMG) signal transmission layer 12 adopts a tree-like structure. Unlike traditional dense arrangements, the tree-like arrangement improves the stretchability of the electronic skin, allowing it to adhere well to the human skin surface during muscle movement-induced stretching, thus reducing signal interference caused by artifacts. The FPC interface 23 is constructed by connecting multiple electrode contacts 21 (the number of electrode contacts is determined by the size of the target muscle group, the sampling spatial resolution, and the hardware design; in one embodiment of the invention, 18 electrode contacts are provided, and in other embodiments, other numbers of electrode contacts can be provided as needed) via copper wires, and is responsible for collecting surface EMG signals.

[0047] In one embodiment of the present invention, please refer to Figure 3 , Figure 3The flowchart for the fabrication of a flexible array-type stretchable electronic skin for the face provided in this embodiment includes the following steps:

[0048] Step 1: For a better fit to the human face structure, please refer to... Figure 4 Cut the flexible tape 41 into a U-shape. The width of the flexible tape 41 is 5mm. The length of the left and right straight lines in the U-shape is 6.0cm. The length of the bottom straight line is 4.5cm (1.8*2cm+0.9cm). The angle between the left and right sides of the U-shape and the horizontal is 45±0.5° to obtain the support layer.

[0049] Step 2: Ultrasonically mix polydimethylsiloxane and curing agent at a total molar ratio of 10:1 to obtain a silicone solution;

[0050] Step 3: Ultrasonically mix silicone gel A agent and B agent (A agent is liquid silicone and B agent is curing agent) in a total molar ratio of 1:1 to obtain an adhesive layer solution;

[0051] Step 4: Using the silicone solution as a stretchable substrate, a doctor blade coating tester is used to coat the silicone solution obtained in Step 2 onto a flat plate (any flat plate material that is insoluble in silicone solution can be used, with low surface roughness, high surface flatness, and high levelness to ensure that the thickness of the silicone solution is consistent throughout after coating; in one embodiment of the present invention, an acrylic plate can be used as the flat plate). The distance between the doctor blade and the flat plate is 0.3 mm, and the coating speed is 2 mm / s to obtain a thin layer of silicone solution on the flat plate.

[0052] Step 5: Incubate the silicone solution thin layer obtained in Step 4 in a 60℃ constant temperature oven for 30 minutes. After curing, cool to room temperature to obtain a cured silicone thin layer attached to the plate.

[0053] Step 6: Fix the cured silicone thin layer obtained in step 5 onto the plate and coat it with the viscous solution obtained in step 3 on a doctor blade coating tester. The distance between the doctor blade and the plate is 0.4 mm and the coating speed is 2 mm / s. A 0.1 mm viscous solution thin layer is obtained on top of the cured silicone thin layer.

[0054] Step 7: The thin film of the adhesive layer solution obtained in Step 6 is kept at 65℃ in a constant temperature oven for 2 hours. After curing, it is cooled to room temperature to obtain a silicone laminate structure with an adhesive layer attached, and then peeled off from the plate.

[0055] Step 8: Place the laminated structure of silicone with an adhesive layer obtained in Step 7 on the laser engraving processing center platform, and use a laser light source to penetrate and process through holes to obtain the base layer 42.

[0056] Step 9: Using polyimide as the base film and top film on both sides of the electromyography signal transmission layer, and copper wire 22 as the intermediate conductive material, a flexible PCB material is prepared. Preferably, the copper wire adopts... Figure 2 The tree-shaped layout shown has a wire width of 1mm.

[0057] Step 10: Use laser penetration method to... Figure 5 The electrode contact points shown are formed in the base film with through holes corresponding to the facial muscle groups. The distance between adjacent electrode contact points is 10mm-20mm. The electrode contacts are circular with a diameter of 3mm-5mm.

[0058] Step 11: Fill the through hole described in Step 10 with copper foil using copper electroplating process, and use laser engraving to obtain the electrode contacts in the electromyography signal transmission layer;

[0059] Step 12: Cut the flexible PCB material from Step 10 to the required size according to the outer contour of the copper conductors / copper foil to obtain the electromyography signal transmission layer. The distance between the outer contour and the copper conductors / copper foil within the contour is 0.4mm. Figure 2 The FPC interface aggregation point is based on Figure 2 Cut to the dimensions shown;

[0060] Step 13: Polymerize the materials described in material combination 1 or material combination 2 to obtain a polyampholyte hydrogel raw material.

[0061] Material combination 1: 4-Styrenesulfonate sodium salt, acryloyloxyethyltrimethylammonium chloride, α-ketoglutaric acid, in a ratio of 1:3:3;

[0062] Material combination 2: Sodium 4-styrenesulfonate, N,N,N-trimethyl-3-(2-methylallylamino)-1-propanediamine chloride, α-ketoglutaric acid, in a ratio of 1:3:3;

[0063] It is understood that in other embodiments, other existing material combinations and proportions can also be used to prepare polyampholyte hydrogels.

[0064] Step 14: Coat the electrode contact surface of the electromyography signal transmission layer with the polyampholyte hydrogel raw material obtained in step 13, place it under ultraviolet light to initiate a polymerization reaction for 30 minutes, thereby obtaining a hydrogel interface layer on the laminated structure.

[0065] Step 15: With the electrode side of the electromyography signal transmission layer containing the hydrogel interface layer facing upward, press and adhere it to the adhesive layer in the base layer obtained in step 8; attach the flexible tape 41 to the base layer obtained in step 8 on the side opposite to the electromyography signal transmission layer to obtain a flexible array-type stretchable electronic skin.

[0066] The support layer prepared in this embodiment of the invention provides structural rigidity for the electronic skin; the base layer tightly adheres to the electronic skin and the human epidermis; the electromyography (EMG) signal transmission layer enables surface EMG signal acquisition via electrode contacts, signal aggregation and transmission via the FPC interface of this layer, and reusability of the electronic skin is achieved through the protection of the polyimide film; the hydrogel interface layer facilitates circuit flow between the electrode contacts and the human epidermis; furthermore, the wire layout of the EMG signal transmission layer can adopt a tree-like arrangement with two parallel lines, and the individual electrode lines are independent of each other, which improves the adhesion performance compared to a model where the electrode lines are fixed as a whole. The electronic skin provided in this embodiment of the invention possesses good EMG signal-to-noise ratio, reusability, adhesion performance, and tensile properties.

[0067] Please refer to Figure 6 and Figure 7 In one embodiment of the present invention, taking the facial action site as an example, the electrode contacts of the flexible array-type stretchable electronic skin are attached to... Figure 6 The facial muscles include the orbicularis oris, depressor anguli oris, zygomaticus major, and zygomaticus minor. The FPC interface can connect to a sensor chip that amplifies electrophysiological signals from living tissue, directly converting the acquired weak electrode signals into a digital data stream. This digital data stream can be programmed and processed on a PC to ultimately present different data images. Figure 7 The data shown is an image representation of the digital data stream converted from electromyographic signals after normalization. This data can be used as a training / validation dataset for electromyographic signals in studies such as silent electromyographic speech synthesis.

[0068] Once the surface electromyography (EMG) signal data acquisition is complete, the physiological signal amplification sensor chip can be removed. The electronic skin can be slowly peeled off from the FPC interface along the direction of the electrode contacts. The hydrogel interface layer attached to the electrode contacts can be placed in clean water for washing. The support layer and base layer can be peeled off from the FPC interface on the back of the electronic skin. After the water has completely evaporated, it can be completely recycled without affecting the subsequent equipment layout and surface EMG signal acquisition, thus achieving the function of reuse.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. The implementation schemes in the above embodiments can also be further combined or replaced. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A flexible array-type stretchable electronic skin, characterized in that, It includes a support layer, a basal layer, an electromyography signal transmission layer, and a hydrogel interface layer; The support layer is constructed of a single-sided adhesive material with a certain physical rigidity, providing the necessary structural rigidity; The base layer and the support layer are bonded and fixed together; The electromyographic signal transmission layer is adhered to the surface of the substrate layer, and the electromyographic signal transmission layer is made of flexible PCB material; A hydrogel interface layer is disposed on the electrode contact surface of the electromyography signal transmission layer.

2. The flexible array-type stretchable electronic skin according to claim 1, characterized in that, The substrate layer provides surface adhesion and is prepared from either polydimethylsiloxane or a polyurethane film.

3. The flexible array-type stretchable electronic skin according to claim 1, characterized in that, The hydrogel interface layer is prepared from a polyampholyte hydrogel.

4. The flexible array-type stretchable electronic skin according to claim 1, characterized in that, The single-sided adhesive material is a medical dressing or flexible silicone.

5. The flexible array-type stretchable electronic skin according to claim 1, characterized in that, The electromyography signal transmission layer includes electrode contacts, wires, and an outer protective film. The wires are used for the conduction of surface electromyography signals. The outer protective film wraps around the wires. The wires are arranged in a tree-like or V-shaped pattern. One end of each branch wire is provided with the electrode contact, and the other end converges to form an FPC interface.

6. The flexible array-type stretchable electronic skin according to claim 5, characterized in that, Branch conductors are arranged in a tree-like or V-shaped pattern, with each pair of conductors running independently side by side, and the electrode contacts connected to them are also separate from each other.

7. A flexible array-type stretchable electronic skin according to claim 5, characterized in that, The distance between any two adjacent electrode contacts is 10mm to 20mm.

8. The flexible array-type stretchable electronic skin according to claim 5, characterized in that, The electrode contacts are circular with a diameter of 3mm to 5mm.

9. A flexible array-type stretchable electronic skin according to any one of claims 1-8, characterized in that, The electrode contacts consist of a conductive material sheet, one side of which is coated with a non-conductive material.

10. A method for preparing a flexible array-type stretchable electronic skin, characterized in that, The method for fabricating the flexible array-type stretchable electronic skin according to any one of claims 1-9 includes the following steps: A single-sided adhesive material with a certain physical rigidity is cut into the required shape to make a support layer; Prepare a base layer, and then attach the support layer to the base layer; Preparation of flexible PCB materials; Electrode contacts are obtained on the flexible PCB material using laser penetration and copper electroplating processes to form an electromyography (EMG) signal transmission layer, which is then laminated and embedded with the substrate layer. The amphoteric electrolyte hydrogel raw material is coated onto the surface of the electrode contacts in the electromyography signal transmission layer, and polymerization is initiated by ultraviolet light to form a hydrogel cover, thus obtaining the flexible array-type stretchable electronic skin.

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