Bionic paper-cut-shaped epidermal electrode for dynamic electrocardiogram monitoring of human body and manufacturing method of bionic paper-cut-shaped epidermal electrode

Abstract

The invention relates to a bionic paper-cut-shaped epidermal electrode for dynamic electrocardiogram monitoring of a human body and a preparation method, the whole bionic paper-cut-shaped epidermal electrode is of a three-electrode single-lead multi-layer combined structure, and the bionic paper-cut-shaped epidermal electrode comprises a top polydimethylsiloxane thin film layer, an adhesion layer, a copper metal functional layer, a copper metal interconnection line and a bottom polyimide insulating layer which are arranged in sequence; the copper metal functional layer is formed by sequentially connecting four groups of subunits in series through four-side arc flexible hinges, and a deformable closed ring is formed in the copper metal functional layer; each group of subunits is composed of an N * N rigid dot array and telescopic flexible hinges connected between adjacent dots, and the telescopic flexible hinges adopt a snake belly imitating hexagonal pattern hinge form; the copper metal interconnection line is snake-shaped; the top polydimethylsiloxane thin film layer is tightly attached to and fixedly connected with one side of the adhesion layer, the copper metal functional layer is tightly attached to and fixedly connected with the other side of the adhesion layer, and the copper metal interconnection line is fixedly connected with a bonding pad of the copper metal functional layer in an adhesive mode and is tightly attached to and fixedly connected with the adhesion layer at the same time. And the bottom polyimide insulating layer is tightly attached and fixedly connected with the other side of the copper metal interconnection wire. According to the invention, a good use effect is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of sensors, and in particular relates to a bionic paper-cutting-shaped epidermal electrode for human body dynamic electrocardiogram monitoring and a manufacturing method thereof. Background Art

[0002] As a portable human-machine coupling device, epidermal electrodes have good mechanical flexibility and special-shaped adaptability. They can be used to monitor human bioelectric signals such as electrocardiogram and electromyography, but they have high requirements for human-machine coordination and wearability. The conformal adaptation of epidermal electrodes to the skin is the key to achieving long-term and stable monitoring of human dynamic electrocardiogram. At present, the mechanical failure problem of the interface between epidermal electrodes and skin is a technical difficulty that limits the realization of conformal adaptation. In order to achieve conformality, the epidermal electrodes must have a large tensile deformation ability, an elastic modulus that is compatible with the skin, and a certain adhesion performance. To this end, domestic and foreign scholars currently mainly optimize the stiffness, strain range, adhesion strength, etc. of electrodes based on composite material regulation and physical model-driven geometric structure strategies. This paper mainly reviews the material regulation and geometric structure design methods of electrodes.

[0003] In the past few decades, various organic conductive materials and semiconductor materials have been developed and applied to epidermal electrodes, such as hydrogels, nanocomposites, etc. Ren et al. from the National University of Singapore developed an epidermal electrode with high conductivity (545S / cm) and low elastic modulus (5Mpa) based on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), waterborne polyurethane (WPU) and d-sorbitol organic materials. Figure 1 As shown in (a), the maximum adhesion force on dry and wet skin reached 0.41N / cm and 0.56N / cm, showing excellent adhesion performance. Academician Zhang Liqun of Beijing University of Chemical Technology prepared a hybrid network hydrogel electrode through dynamic supramolecular crosslinking between single-walled carbon nanotubes, polyvinyl alcohol and polydopamine, such as Figure 1 As shown in (b), the bonding strength with pig skin reached 5.2KPa. Majidi et al. from Carnegie Mellon University sprayed a layer of silver nanoparticles and indium gallium alloy mixture on the PDMS substrate. Figure 1 As shown in (c), the failure strain of the device is as high as 118%, which can be applied to highly curved soft skin surfaces. Miyashita et al. from Tokyo Institute of Technology integrated gold nanoparticles onto the surface of polystyrene butadiene copolymer film by printing. Figure 1 As shown in (d), a neural electrode with mechanical properties similar to those of biological tissue was prepared, with an elastic modulus of only 45 MPa.

[0004] However, the epidermal electrodes made of such materials have poor electrical properties and are easily affected by the environment, such as the evaporation of water in the hydrogel. Therefore, the design of epidermal electrodes based on metal materials has become an alternative method.

[0005] Metal materials are inherently hard and have mechanical properties of low strain and high elastic modulus, so they cannot be directly used on the human body. Therefore, scholars at home and abroad have prepared metal electrodes with excellent mechanical properties based on the serpentine structure. For example, Professor Yu Xinge of the City University of Hong Kong proposed a bionic spider web electrode, such as Figure 1 As shown in (e), not only the effective working area of ​​the electrode is increased to 51.34%, but also 30% biaxial stretching of the electrode is achieved. Yeo et al. from Georgia Institute of Technology designed a fractal structure electrode for human sleep monitoring, such as Figure 1 As shown in (f), its mechanical tensile deformation reaches 30%, and it shows excellent performance in 1000 tensile fatigue tests. Similarly, Rogers et al. from Northwestern University designed a conformal epidermal electrode for the treatment of heart disease, such as Figure 1 As shown in (g), eight fractal structure electrodes are integrated on the surface of the heart in a serpentine interconnected manner, combining large area coverage, high filling rate, excellent stretchability and flexibility. During the entire beating and contraction cycle of the heart, the electrode array always remains attached to the surface of the heart.

[0006] However, although these deformable structures have macroscopic stretchability, they cannot combine good microscopic compliance with large active surfaces. For example, fractal structures, such as Figure 2 As shown in (a), when the ratio of line width w to thickness t is greater than 1, the stretched metal electrode will undergo out-of-plane buckling, resulting in a microscopic gap between the electrode and the skin interface, such as Figure 2 (b) shows poor conformal adhesion. When the ratio of line width w to thickness t is less than 1, it will result in a lower active surface and thus higher contact impedance. Summary of the invention

[0007] In view of the above technical problems, the present invention provides a bionic paper-cut shape epidermal electrode for human body dynamic electrocardiogram monitoring and a manufacturing method thereof.

[0008] One of the above-mentioned purposes of the present invention is achieved by the following technical solution:

[0009] A bionic paper-cut epidermal electrode for human body dynamic electrocardiogram monitoring, the bionic paper-cut epidermal electrode as a whole is a three-electrode single-lead multilayer combination structure, including a top polydimethylsiloxane film layer, an adhesion layer, a copper metal functional layer, a copper metal interconnection line and a bottom polyimide insulation layer arranged in sequence; the structure of the copper metal functional layer is a bionic paper-cut structure, the bionic paper-cut structure is composed of four groups of sub-units connected in series through four-sided arc flexible hinges, forming a deformable closed loop inside; each group of sub-units is composed of an N×N rigid dot array and a The copper metal interconnection line is formed by a retractable flexible hinge between the dots, wherein the retractable flexible hinge adopts a hexagonal hinge pattern imitating the belly of a snake; the copper metal interconnection line is in a snake shape; the top polydimethylsiloxane film layer is tightly attached to and fixedly connected with one side of the adhesion layer, the copper metal functional layer is tightly attached to and fixedly connected with the other side of the adhesion layer, the copper metal interconnection line is fixedly connected to the pad of the copper metal functional layer in an adhesive form, and is tightly attached to and fixedly connected with the adhesion layer at the same time, and the bottom polyimide insulating layer is tightly attached to and fixedly connected with the other side of the copper metal interconnection line.

[0010] Moreover, the top polydimethylsiloxane film layer is formed by mixing a polydimethylsiloxane main agent and a curing agent solution and curing at high temperature; the adhesive layer is formed by mixing a polydimethylsiloxane main agent, a curing agent and a polyethylene glycol solution and curing at high temperature.

[0011] Moreover, the ratio of the single-side wall thickness of the retractable flexible hinge to the thickness of the copper metal functional layer is 1.

[0012] The second object of the present invention is achieved by the following technical solution:

[0013] A method for preparing a bionic paper-cut epidermal electrode for human body dynamic electrocardiogram monitoring comprises the following steps:

[0014] Step 1: Using femtosecond laser integrated processing to make copper metal interconnects and bottom polyimide insulation layers;

[0015] Step 2: Using femtosecond laser processing to produce a copper metal functional layer;

[0016] Step 3: preparing a top polydimethylsiloxane film layer;

[0017] Step 4, preparing an adhesive layer below the top polydimethylsiloxane film layer;

[0018] Step 5: Adhere the copper metal interconnection line made in step 1 to the adhesion layer prepared in step 4;

[0019] Step 6: Adhere the copper metal functional layer prepared in step 2 to the adhesive layer prepared in step 4;

[0020] Step 7: Use solder to weld and fix the copper metal functional layer electrode and the pads of the copper metal interconnection line; then use a carbon dioxide laser device to process the bionic paper-cut shape epidermal electrode according to the outline drawing of the adhesion layer, and remove excess material.

[0021] Furthermore, step 1 includes:

[0022] 1.6. First, place an appropriate amount of polyvinyl alcohol and deionized water in a beaker and stir them thoroughly to prepare a polyvinyl alcohol solution;

[0023] 1.7. Then clean the glass substrate with alcohol and fix it on the spin coating equipment;

[0024] 1.8. Next, the polyvinyl alcohol solution is spin-coated on the cleaned glass substrate at a rotation speed of 800 r / min, and dried at a high temperature to form an adhesive;

[0025] 1.9. Then attach a 0.01 mm thick PI copper foil to the treated glass substrate in a flat manner;

[0026] 1.10. Finally, according to the copper metal interconnection line drawing, a femtosecond laser is used to process the copper metal interconnection line and remove excess material.

[0027] Furthermore, step 2 includes:

[0028] 2.1 First, place an appropriate amount of polyvinyl alcohol and deionized water in a beaker and stir them thoroughly to prepare a polyvinyl alcohol solution;

[0029] 2.2 Then clean the glass substrate with alcohol and fix it on the spin coating equipment;

[0030] 2.3 Next, the polyvinyl alcohol solution is spin-coated on the cleaned glass substrate at a speed of 800 r / min, and dried at a high temperature to form an adhesive;

[0031] 2.4. Then, a 0.01 mm thick copper foil is attached to the treated glass substrate in a flat manner;

[0032] 2.5. Finally, according to the drawings of the bionic paper-cut structure, a femtosecond laser is used to process the copper metal functional layer and remove excess material.

[0033] Furthermore, step 3 includes:

[0034] 3.1 First, place the polydimethylsiloxane main agent and the curing agent in a beaker at a ratio of 10:1 and stir them thoroughly to prepare a mixed solution;

[0035] 3.2 Then put the glass beaker containing the mixed solution into a vacuum device for degassing;

[0036] 3.3 Next, the treated mixed solution was spin-coated on the alcohol-cleaned glass substrate at a speed of 600 r / min, and then placed in an oven and baked at a high temperature of 120° C. for 10 min to solidify and form a top polydimethylsiloxane film layer;

[0037] Furthermore, step 4 includes:

[0038] 4.1 First, place polydimethylsiloxane curing agent and polyethylene glycol in a ratio of 2:8 in a beaker containing the main agent and stir them thoroughly to prepare a mixed solution;

[0039] 4.2 Then put the glass beaker containing the mixed solution into a vacuum device for degassing;

[0040] 4.3 Next, the treated mixed solution is spin-coated on the glass substrate treated in step 3 at a speed of 600 r / min, and is placed in an oven and baked at a high temperature of 120° C. for 10 min to solidify the lower surface of the top polydimethylsiloxane film layer to form an adhesion layer.

[0041] Furthermore, step 5 includes:

[0042] 5.1. First, immerse the copper metal interconnection wire adhered to the glass substrate processed in step 1 into water to dissolve the polyvinyl alcohol adhesive;

[0043] 5.2. Then, a 3M water-soluble tape is applied flatly to the surface of the copper metal interconnection line to transfer the copper metal interconnection line on the glass substrate to the tape surface;

[0044] 5.3. Next, the tape containing the copper metal interconnection line is attached to the glass substrate processed in step 4 in a flat manner;

[0045] 5.3. Finally, immerse it in water to remove the 3M water-soluble tape by dissolving it, so that the copper metal interconnection line adheres to the adhesive layer.

[0046] Furthermore, step 6 includes

[0047] 6.1. Immerse the copper metal functional layer adhered to the glass substrate processed in step 2 into water to dissolve the polyvinyl alcohol adhesive;

[0048] 6.2. Then, a 3M water-soluble tape is attached to the surface of the copper metal functional layer in a flat manner to transfer the copper metal functional layer on the glass substrate to the tape surface;

[0049] 6.3. Next, the tape containing the copper metal functional layer is attached to the glass substrate processed in step 5 in a flat manner, and the pad positions of the electrodes and interconnects are aligned;

[0050] 6.4. Finally, immerse it in water to remove the 3M water-soluble tape by dissolving it, so that the copper metal functional layer adheres to the adhesive layer.

[0051] The present invention has the following advantages and positive effects:

[0052] 1. The bionic paper-cut shaped epidermal electrode of the present invention adopts a bionic paper-cut shaped design. When the stretching rate is less than 30%, on the one hand, the electrode deformation is mainly reversible elastic deformation at the hinge part without obvious buckling phenomenon, and the rigid dots are almost strain-free, with good micro-compliance; on the other hand, the mechanical properties of the electrode, such as the stretching range, stretching stiffness, and bending stiffness, are adapted to the skin.

[0053] 2. The active surface of the bionic paper-cut epidermal electrode of the present invention is as high as 32.66%, which is 10.83% higher than the active surface of the fractal structure under the same ratio of line width w to thickness t.

[0054] 3. The structural design of the present invention is scientific and reasonable, with low cost, and can reasonably realize dynamic electrocardiogram monitoring of the human body, achieving good use effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Middle: 1a is a schematic diagram of an epidermal electrode attached to the skin surface; 1b is a hydrogel electrode attached to the skin surface, used to detect human physiological electrical signals; 1c is an image of an epidermal electrode attached to the surface of a brain model; 1d is a microscopic image of an epidermal electrode attached to the brain surface; 1e is a schematic diagram of a bionic spider web structure electrode; 1f is a schematic diagram of a fractal structure electrode; 1g is an image of a fractal structure electrode attached to the surface of the heart;

[0056] Figure 2 Middle: 2a is a schematic diagram of the fractal structure electrode (top) and the locally enlarged (bottom) structure; 2b is a SEM image of the electrode with out-of-plane buckling;

[0057] Figure 3 3a is a schematic diagram of the bionic paper-cut structure, the upper left picture is a deer, and the lower left picture is a snake; 3b is a schematic diagram of the structure of the copper metal interconnection line;

[0058] Figure 4 4a is a schematic diagram of the epidermal electrode structure; 4b is the structure and size of the top polydimethylsiloxane film layer and the adhesion layer; 4c is the structure and size of the copper metal functional layer; 4d is the structure and size of the copper metal interconnect layer; 4e is a partial enlarged view of the copper metal functional layer;

[0059] Figure 5Middle: 5a is a schematic diagram of a 6×6 rigid dot array structure; 5b is a schematic diagram of the structure and deformation principle of the paper-cut flexible hinge; 5c is a schematic diagram of the copper metal functional layer composed of the paper-cut flexible hinge and the array dots; 5d is a schematic diagram of the bionic paper-cut structure electrode; 5e is the deformation of the bionic paper-cut structure electrode in the xy plane and z axis direction caused by skin contraction; 5f is the deformation of the bionic paper-cut structure electrode in the xy plane and z axis direction caused by skin expansion;

[0060] Figure 6 Middle: 6a is a strain distribution cloud diagram of the paper-cut flexible hinge when it is stretched by 15%; 6b is a stress-strain curve diagram of the paper-cut flexible hinge when it is stretched uniaxially; 6c is a 50-fold magnified SEM image of the undeformed paper-cut flexible hinge; 6d is a 50-fold magnified SEM image of the broken paper-cut flexible hinge;

[0061] Figure 7 Middle: 7a is a stress distribution cloud diagram of the bionic paper-cut structure electrode when it is stretched by 30%; 7b is a stress distribution cloud diagram of the bionic paper-cut structure electrode when it is bent by 130°; 7c is a stress-strain curve diagram of the bionic paper-cut structure electrode when it is stretched;

[0062] Figure 8 Middle: 8a (Ⅰ) is a schematic diagram of the adhesion film pull-out test, (Ⅱ) is a photo of the adhesion film pull-out test; 8b is a graph of the pull-out test of the adhesion film under dry and wet conditions; 8c is an image of an electrode without deformation on the left, an image of an electrode under compression on the middle, and an image of an electrode under twist on the right;

[0063] Fig. 9 A schematic diagram of the process of using epidermal electrodes to monitor human dynamic electrocardiogram;

[0064] Fig.10 Middle: 10a is the human electrocardiogram measured by the bionic paper-cut shape epidermal electrode in the cycling state; 10b is the human electrocardiogram measured by the bionic paper-cut shape epidermal electrode after the cycling stops; 10c is the human electrocardiogram measured by the fractal structure epidermal electrode in the cycling state; 10d is the human electrocardiogram measured by the fractal structure epidermal electrode after the cycling stops;

[0065] Fig.11 Schematic diagram of the overall structure of the bionic paper-cut shaped epidermal electrode. DETAILED DESCRIPTION

[0066] The structure of the present invention is further described below with reference to the accompanying drawings and by way of examples. It should be noted that the present examples are descriptive rather than restrictive.

[0067] A bionic paper-cut epidermal electrode for human dynamic electrocardiogram monitoring, see Figure 3-Figure 11The invention point is: a multi-layer composite structure is adopted, including a top polydimethylsiloxane film layer, an adhesion layer, a copper metal functional layer, a copper metal interconnection line and a bottom polyimide insulating layer arranged in sequence; the top polydimethylsiloxane film layer is formed by mixing a polydimethylsiloxane main agent and a curing agent solution and curing at high temperature, the adhesion layer is formed by mixing a polydimethylsiloxane main agent, a curing agent and a polyethylene glycol solution and curing at high temperature, the structure of the copper metal functional layer is a bionic paper-cut structure, and the bionic paper-cut structure is composed of a combination of a snake skin bionic pattern and a decapod shell bionic pattern, such as Figure 3 As shown in (a), the copper metal interconnection line structure is a serpentine pattern, such as Figure 3 (b); the top polydimethylsiloxane film layer is tightly attached to and fixedly connected to one side of the adhesion layer, the copper metal functional layer is tightly attached to and fixedly connected to the other side of the adhesion layer, the copper metal interconnection line is fixedly connected to the pad of the copper metal functional layer in an adhesive form, and is tightly attached to and fixedly connected to the adhesion layer, and the bottom polyimide insulating layer is tightly attached to and fixedly connected to the other side of the copper metal interconnection line.

[0068] The bionic paper-cut epidermal electrode is a three-electrode single-lead structure. Figure 4 As shown in (a), the thickness of the top polydimethylsiloxane film layer is 0.1 mm, the outer diameter is φ77 mm, and the detailed dimensions are as follows: Figure 4 (b) The thickness of the adhesive layer is 0.01 mm, the outer diameter is φ77 mm, and the detailed dimensions are as follows Figure 4 The copper metal functional layer has a thickness of 0.01 mm, an outer contour length of 17 mm, and a maximum outer contour width of 15.14 mm. The detailed dimensions are as follows: Figure 4 (c) and Figure 4 The copper metal interconnect layer has a thickness of 0.01 mm, a length of 14.5 mm, and a line width of 0.1 mm. The detailed dimensions are as follows: Figure 4 (d) as shown.

[0069] The conformal adaptation of a flexible device to the skin is usually related to the total energy of the system, which includes the bending energy, stretching energy, adhesion energy and strain energy of the device and the skin. The total energy of the system is usually related to the mechanical indicators of the stiffness, stretching range and adhesion strength of the flexible device. To this end, the present invention achieves conformal attachment to the skin by regulating the stiffness, strain range and adhesion strength of the epidermal electrode.

[0070] Copper foil has become one of the best materials for epidermal electrode functional layers due to its high electrical properties, high chemical stability, antibacterial properties and low cost. However, copper foil is inherently soft and almost inextensible, and cannot form a conformal attachment to flexible skin with non-zero Gaussian curvature. To this end, the present invention hollowed out a 0.01 mm thick copper foil by drawing on the structure of snake skin and the carapace of the decapod, and prepared a bionic paper-cut structure copper metal functional layer, which can not only form a good conformal attachment to the skin, but also has an active surface of up to 32.66%.

[0071] Considering the softness of the skin, a 0.01mm×11mm×11mm copper foil was designed into a 6×6 rigid dot array structure (with a spacing of 2mm) based on the structure of the Deinonychus carapace. Figure 5 (a) As shown. Secondly, considering the strain range of the skin, a paper-cut flexible hinge for connecting the array dots was designed based on the structure of the hexagonal pattern on the snake's abdomen, as shown in Figure 5 As shown in (b), with the extension and compression, the "V" at both ends of the hexagon opens and closes in a rotating manner. In addition, considering the influence of the line width to thickness ratio on buckling, the line width w of the paper-cut flexible hinge structure (in Figure 4 e, the ratio of “line width w” (i.e., the wall thickness of one side of the hinge) to thickness (i.e., the thickness of the copper metal functional layer) is designed to be 1. However, the copper metal functional layer composed of the paper-cut flexible hinge and the array dots, such as Figure 5 As shown in (c), it cannot adapt to the elastic modulus of the skin (5kPa–140MPa) and cannot meet the 30% tensile deformation of the skin. In order to reduce the tensile stiffness of the electrode and increase the elongation rate of the electrode, inspired by the “V” shape deformation of the hexagonal pattern, Figure 5 The paper-cut flexible hinges ①-④ in (c) are changed to arc flexible hinges. The bionic paper-cut structure electrode is as follows: Figure 5 (d) as shown. Figure 5 (e) and Figure 5 (f) Demonstrates the deformation principles of the bionic kirigami structure electrode when subjected to stretching and compression.

[0072] In order to evaluate the conformal adaptation of the bionic paper-kirigami structure electrode to the skin, the mechanical properties of the paper-kirigami structure electrode were analyzed by finite element analysis and experiments. First, the uniaxial tensile finite element simulation of the paper-kirigami flexible hinge was carried out to study the magnitude and distribution of its strain. The results are shown in Figure 2. Figure 6 (a) The simulation results show that under the condition of 15% uniaxial tension, the strain of the paper-cut flexible hinge is concentrated in the V-shaped part of the structure, and its maximum true strain value is only 0.365. Next, the paper-cut flexible hinge was subjected to a tensile fracture experimental test. The results are shown in Figure 6(b). The results show that its maximum elongation can reach 26.35%. In addition, the micro-compliance of the kirigami flexible hinge was experimentally evaluated. During the entire tensile fracture process, Figure 6 (d) shows that the flexible hinge is only torn near the rigid point connection, compared with the undeformed ( Figure 6 (c)), the rest of the parts have no obvious out-of-plane buckling deformation and have excellent micro-compliance.

[0073] Figure 7 (a) and Figure 7 (b) The finite element simulation of the stretching and bending deformation of the bionic paper-cut structure electrode. The simulation shows that when the stretching rate of the electrode does not exceed 30% ( Figure 7 (a)), the stress is mainly concentrated in the arc flexible hinge, and the maximum Mises stress is much smaller than the yield strength of copper, 155.35Mpa. When the electrode is subjected to 130° bending deformation ( Figure 7 (b)), the stress is also concentrated on the arc flexible hinge, and the maximum Mises stress is also less than the yield strength of copper. Due to the different structures of the two flexible hinges, the tensile fracture test curve of the bionic paper-cut structure electrode is highly nonlinear, such as Figure 7 (c) When the stretching rate is less than 30%, the electrode tensile stiffness is only 3.8×10-3N / mm, which has excellent softness. At this stage, the electrode is mainly deformed by the rotation of the arc flexible hinge with lower stiffness, and the paper-cut flexible hinge with higher stiffness does not deform. When the stretching rate exceeds 30%, the rotation deformation of the arc flexible hinge reaches the limit, the paper-cut flexible hinge gradually undergoes tensile deformation, and the tensile stiffness of the electrode increases rapidly until the stretching rate reaches 53.82%, and it begins to break.

[0074] Based on the above simulation and experimental tests, the results show that the stretching range, stretching stiffness and bending stiffness of the bionic paper-kirigami structure electrode can adapt to the skin.

[0075] The 0.01 mm thick copper metal functional layer is difficult to form a tight adhesion with the skin by physical interaction alone, and an external force is required to ensure that the copper metal functional layer can match the local surface morphology of the skin. In addition, considering the effect of skin sweat on adhesion, the present invention adds a sweat-resistant adhesion layer on the basis of the copper metal functional layer.

[0076] On the one hand, polydimethylsiloxane has excellent chemical stability, thermal stability and biocompatibility, and is often used in biological dressings. On the other hand, during the curing process, when a certain amount of polyethylene glycol is added to the polydimethylsiloxane main agent and curing agent solution, the catalytic effect of platinum will be weakened, so that the polydimethylsiloxane forms a semi-crosslinked network, showing excellent softness, wet adhesion and stretchability. Therefore, the present invention selects polydimethylsiloxane main agent, curing agent and polyethylene glycol materials to prepare the adhesion layer.

[0077] To evaluate the adhesion strength of the adhesive layer under dry / wet skin conditions. In the experiment, polydimethylsiloxane curing agent and polyethylene glycol were mixed in a ratio of 2:8 and poured into the polydimethylsiloxane main agent and cured. The cured adhesive film (0.3mm×30mm×30mm) was pulled to test the adhesion strength with the human arm skin. The test method is as follows: Figure 8 (a)(Ⅰ)~(Ⅱ), test curve is as follows Figure 8 (b) As shown. The results show that the adhesion strength of the adhesive film under dry and wet skin conditions can reach 8.64KPa and 5.08KPa respectively, which can ensure that the copper metal functional layer is tightly attached to the skin surface. In addition, when one side of the adhesive film is integrated with the bionic paper-cut structure electrode, the adhesion of the other side needs to be isolated. For this purpose, a non-adhesive film with a thickness of 0.1mm is added to the side of the adhesive layer, namely a fully cross-linked polydimethylsiloxane film.

[0078] Finally, the bionic paper-cut structure electrode, adhesive layer, and polydimethylsiloxane film were integrated together to evaluate the adaptability of the surface electrode patch to the skin surface. Under the conditions of skin stretching and torsion deformation, the electrode patch can maintain close adhesion to the skin, such as Figure 8 (c) as shown.

[0079] Preparation method of bionic paper-cut epidermal electrodes:

[0080] Step 1: First, place an appropriate amount of polyvinyl alcohol and deionized water in a beaker and stir them thoroughly to prepare a polyvinyl alcohol solution. Then use alcohol to clean the glass substrate and fix it on the spin coating equipment. Next, spin coat the polyvinyl alcohol solution on the cleaned glass substrate at a speed of 800r / min, and dry it at high temperature to form an adhesive. Secondly, attach a 0.01mm thick PI copper foil to the treated glass substrate in a flat manner. Finally, according to the drawings of the copper metal interconnects, a femtosecond laser is used to integrally process the copper metal interconnects and the bottom polyimide insulation layer, and remove excess materials.

[0081] Step 2: First, place an appropriate amount of polyvinyl alcohol and deionized water in a beaker and stir them thoroughly to prepare a polyvinyl alcohol solution. Then use alcohol to clean the glass substrate and fix it on the spin coating equipment. Next, spin coat the polyvinyl alcohol solution on the cleaned glass substrate at a speed of 800r / min, and dry it at high temperature to form an adhesive. Secondly, attach a 0.01mm thick copper foil to the treated glass substrate in a flat manner. Finally, according to the drawings of the bionic paper-cut structure, a femtosecond laser is used to process the copper metal bionic paper-cut structure electrode (i.e., the copper metal functional layer) and remove excess material.

[0082] Step 3: First, place the polydimethylsiloxane main agent and curing agent in a beaker at a ratio of 10:1 and stir them thoroughly to prepare a mixed solution. Then put the glass beaker containing the mixed solution into a vacuum device for degassing. Next, spin-coat the treated mixed solution on a glass substrate cleaned with alcohol at a speed of 600r / min, and place it in an oven and bake it at a high temperature of 120°C for 10 minutes to solidify and form a polydimethylsiloxane film.

[0083] Step 4: First, place the polydimethylsiloxane curing agent and polyethylene glycol in a beaker containing the main agent at a ratio of 2:8, and stir them thoroughly to prepare a mixed solution. Then put the glass beaker containing the mixed solution into a vacuum device for degassing. Next, spin-coat the treated mixed solution on the glass substrate treated in step 3 at a speed of 600r / min, and place it in an oven and bake it at a high temperature of 120°C for 10 minutes to solidify the polydimethylsiloxane film surface to form an adhesive film.

[0084] Step 5: First, immerse the copper metal interconnection wires processed in step 1 and attached to the glass substrate in water to dissolve the polyvinyl alcohol adhesive. Then, a 3M water-soluble tape is applied to the surface of the copper metal interconnection wires in a flat manner to transfer the copper metal interconnection wires on the glass substrate to the surface of the tape. Next, the tape containing the copper metal interconnection wires is applied to the glass substrate processed in step 4 in a flat manner. Finally, it is immersed in water to remove the 3M water-soluble tape by dissolving.

[0085] Step 6: First, immerse the copper metal bionic paper-cut structure electrode adhered to the glass substrate processed in step 2 into water to dissolve the polyvinyl alcohol adhesive. Then, attach the 3M water-soluble tape to the surface of the copper metal bionic paper-cut structure electrode in a flat manner to transfer the copper metal bionic paper-cut structure electrode on the glass substrate to the surface of the tape. Next, attach the tape containing the copper metal bionic paper-cut structure electrode in a flat manner on the glass substrate processed in step 5 and align the pad positions of the electrode and the interconnection line. Finally, immerse it in water and remove the 3M water-soluble tape by dissolving.

[0086] Step 7: First, solder the pads of the electrodes and interconnects to fix them. Then, a carbon dioxide laser device is used to process the bionic paper-cut epidermal electrodes according to the outline drawing of the adhesion layer and remove excess materials.

[0087] Application examples:

[0088] Evaluation of the quality of human dynamic electrocardiogram monitoring

[0089] In order to evaluate the monitoring quality of dynamic ECG in human cycling, the present invention respectively attaches bionic paper-cut epidermal electrodes and fractal structure epidermal electrodes with the same line width to the left chest of the human body, and sends the collected ECG data to the PC through the ADS1292 development board to realize the recording and analysis of dynamic ECG data. Fig. 9 One of the challenges of dynamic ECG monitoring is the motion artifact caused by slippage, poor consistency and mechanical mismatch between the device and the skin interface, which results in a decrease in the signal-to-noise ratio. Fig.10 (a) shows the ECG measurement results of the bionic paper-cut epidermal electrode in cycling state, with a signal-to-noise ratio of 23.1176db, compared with the signal-to-noise ratio of 26.6881( Fig.10 (b)), decreased by 3.5705db. The fractal structure electrode used for device comparison, the ECG results measured in the cycling state are as follows Fig.10 As shown in (c), the signal-to-noise ratio is 19.6418db, compared with the signal-to-noise ratio of 22.3579db when the movement stops ( Fig.10 (d)), decreased by 2.7161db. With the increase of motion artifacts, compared with the fractal structure electrode, the bionic paper-cut epidermal electrode showed obvious R, S, and T waves, with stronger resolution.

[0090] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A bionic paper-cut epidermal electrode for human body dynamic electrocardiogram monitoring, characterized in that: The bionic paper-cut epidermal electrode is a three-electrode single-lead multi-layer composite structure as a whole, including a top polydimethylsiloxane film layer, an adhesion layer, a copper metal functional layer, a copper metal interconnection line and a bottom polyimide insulating layer arranged in sequence; the structure of the copper metal functional layer is a bionic paper-cut structure, and the bionic paper-cut structure is composed of four groups of sub-units connected in series in sequence through four-sided arc flexible hinges, forming a deformable closed loop inside; each group of sub-units is composed of an N×N rigid dot array and a retractable flexible hinge connected between adjacent dots, and the retractable flexible hinge adopts a hexagonal pattern hinge form imitating the belly of a snake; the copper metal interconnection line is serpentine; the top polydimethylsiloxane film layer is tightly attached to and fixedly connected to one side of the adhesion layer, the copper metal functional layer is tightly attached to and fixedly connected to the other side of the adhesion layer, the copper metal interconnection line is fixedly connected to the pad of the copper metal functional layer in an adhesive form, and is tightly attached to and fixedly connected to the adhesion layer at the same time, and the bottom polyimide insulating layer is tightly attached to and fixedly connected to the other side of the copper metal interconnection line.

2. The bionic paper-cutting shaped epidermal electrode for human body dynamic electrocardiogram monitoring according to claim 1, characterized in that: The top polydimethylsiloxane film layer is formed by mixing a polydimethylsiloxane main agent and a curing agent solution and curing at high temperature; the adhesive layer is formed by mixing a polydimethylsiloxane main agent, a curing agent and a polyethylene glycol solution and curing at high temperature.

3. The bionic paper-cutting shaped epidermal electrode for human body dynamic electrocardiogram monitoring according to claim 1, characterized in that: The ratio of the single-side wall thickness of the retractable flexible hinge to the thickness of the copper metal functional layer is 1.

4. A method for preparing a bionic paper-cut shaped epidermal electrode for human body dynamic electrocardiogram monitoring according to any one of claims 1 to 3, characterized in that: The steps include: Step 1: Using femtosecond laser integrated processing to make copper metal interconnects and bottom polyimide insulation layers; Step 2: Using femtosecond laser processing to produce a copper metal functional layer; Step 3: preparing a top polydimethylsiloxane film layer; Step 4, preparing an adhesive layer below the top polydimethylsiloxane film layer; Step 5: Adhere the copper metal interconnection line made in step 1 to the adhesion layer prepared in step 4; Step 6: Adhere the copper metal functional layer prepared in step 2 to the adhesive layer prepared in step 4; Step 7: Use solder to weld and fix the pads of the copper metal functional layer electrode and the copper metal interconnection wire; then use a carbon dioxide laser device to process the bionic paper-cut shape epidermal electrode according to the outline drawing of the adhesion layer, and remove excess material.

5. The method for preparing the bionic paper-cutting shaped epidermal electrode for human body dynamic electrocardiogram monitoring according to claim 4, characterized in that: Step 1 includes: 1.

1. First, place an appropriate amount of polyvinyl alcohol and deionized water in a beaker and stir them thoroughly to prepare a polyvinyl alcohol solution; 1.

2. Then clean the glass substrate with alcohol and fix it on the spin coating equipment; 1.

3. Next, the polyvinyl alcohol solution is spin-coated on the cleaned glass substrate at a speed of 800 r / min, and dried at a high temperature to form an adhesive; 1.

4. Then attach a 0.01 mm thick PI copper foil to the treated glass substrate in a flat manner; 1.

5. Finally, according to the copper metal interconnection line drawing, the copper metal interconnection line and the bottom polyimide insulation layer are processed by femtosecond laser, and the excess material is removed.

6. The method for preparing the bionic paper-cutting shaped epidermal electrode for human body dynamic electrocardiogram monitoring according to claim 4, characterized in that: Step 2 includes: 2.1 First, place an appropriate amount of polyvinyl alcohol and deionized water in a beaker and stir them thoroughly to prepare a polyvinyl alcohol solution; 2.2 Then clean the glass substrate with alcohol and fix it on the spin coating equipment; 2.3 Next, the polyvinyl alcohol solution is spin-coated on the cleaned glass substrate at a speed of 800 r / min, and dried at a high temperature to form an adhesive; 2.

4. Then, a 0.01 mm thick copper foil is attached to the treated glass substrate in a flat manner; 2.

5. Finally, according to the drawings of the bionic paper-cut structure, a femtosecond laser is used to process the copper metal functional layer and remove excess material.

7. The method for preparing the bionic paper-cutting shaped epidermal electrode for human body dynamic electrocardiogram monitoring according to claim 4, characterized in that: Step 3 includes: 3.1 First, place the polydimethylsiloxane main agent and the curing agent in a beaker at a ratio of 10:1 and stir them thoroughly to prepare a mixed solution; 3.2 Then put the glass beaker containing the mixed solution into a vacuum device for degassing; 3.3 Next, the treated mixed solution was spin-coated on the alcohol-cleaned glass substrate at a rotation speed of 600 r / min, and was placed in an oven and baked at a high temperature of 120° C. for 10 min to solidify and form a top polydimethylsiloxane film layer.

8. The method for preparing the bionic paper-cutting shaped epidermal electrode for human body dynamic electrocardiogram monitoring according to claim 4, characterized in that: Step 4 includes: 4.1 First, place polydimethylsiloxane curing agent and polyethylene glycol in a ratio of 2:8 in a beaker containing the main agent and stir them thoroughly to prepare a mixed solution; 4.2 Then put the glass beaker containing the mixed solution into a vacuum device for degassing; 4.3 Next, the treated mixed solution is spin-coated on the glass substrate treated in step 3 at a speed of 600 r / min, and is placed in an oven and baked at a high temperature of 120° C. for 10 min to solidify the lower surface of the top polydimethylsiloxane film layer to form an adhesion layer.

9. The method for preparing the bionic paper-cutting shaped epidermal electrode for human body dynamic electrocardiogram monitoring according to claim 4, characterized in that: Step 5 includes: 5.

1. First, immerse the copper metal interconnection wire adhered to the glass substrate processed in step 1 into water to dissolve the polyvinyl alcohol adhesive; 5.

2. Then, a 3M water-soluble tape is applied flatly to the surface of the copper metal interconnection line to transfer the copper metal interconnection line on the glass substrate to the tape surface; 5.

3. Next, the tape containing the copper metal interconnection line is attached to the glass substrate processed in step 4 in a flat manner; 5.

3. Finally, immerse it in water to remove the 3M water-soluble tape by dissolving it, so that the copper metal interconnection line adheres to the adhesive layer.

10. The method for preparing the bionic paper-cutting shaped epidermal electrode for human body dynamic electrocardiogram monitoring according to claim 4, characterized in that: Step 6 includes 6.

1. Immerse the copper metal functional layer adhered to the glass substrate processed in step 2 into water to dissolve the polyvinyl alcohol adhesive; 6.

2. Then, a 3M water-soluble tape is attached to the surface of the copper metal functional layer in a flat manner to transfer the copper metal functional layer on the glass substrate to the tape surface; 6.

3. Next, the tape containing the copper metal functional layer is attached to the glass substrate processed in step 5 in a flat manner, and the pad positions of the electrodes and interconnects are aligned; 6.

4. Finally, immerse it in water to remove the 3M water-soluble tape by dissolving it, so that the copper metal functional layer adheres to the adhesive layer.

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