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

Abstract

The application relates to a bionic paper-cut-shaped skin electrode for dynamic electrocardiogram monitoring of a human body and a preparation method, which is a three-electrode single-lead multilayer combined structure and comprises a top polydimethylsiloxane film layer, an adhesive layer, a copper metal functional layer, a copper metal interconnecting line and a bottom polyimide insulating layer arranged in sequence; the copper metal functional layer is composed of four groups of sub-units which are connected in series through four-edge arc flexible hinges in sequence, and a deformable closed loop is formed in the inside; each group of sub-units is composed of an N*N rigid dot array and a stretchable flexible hinge connected between adjacent dots, and the stretchable flexible hinge adopts a hexagon pattern hinge form similar to a snake abdomen; the copper metal interconnecting line is in a snake shape; the top polydimethylsiloxane film layer is tightly attached to one side of the adhesive layer and is fixedly connected, the copper metal functional layer is tightly attached to the other side of the adhesive layer and is fixedly connected, the copper metal interconnecting line is adhered and fixedly connected to the bonding pad of the copper metal functional layer, is tightly attached to the adhesive layer and is fixedly connected, and the bottom polyimide insulating layer is tightly attached to the other side of the copper metal interconnecting line and is fixedly connected. The application achieves good use effect.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, and in particular relates to a biomimetic paper-cut-shaped epidermal electrode for dynamic electrocardiogram monitoring of the human body and its manufacturing method. Background Technology

[0002] As a portable human-machine coupling device, epidermal electrodes possess excellent mechanical flexibility and adaptability to various shapes, making them suitable for monitoring human bioelectrical signals such as electrocardiograms (ECG) and electromyography (EMG). However, they require high levels of human-machine coordination and fit. Conformal adaptation between the epidermal electrode and the skin is crucial for achieving long-term stable monitoring of dynamic ECGs. Currently, mechanical failure at the epidermal electrode-skin interface is a major technical challenge limiting conformal adaptation. To achieve conformal adaptation, the epidermal electrode needs to possess three key characteristics: large tensile deformation capacity, an elastic modulus compatible with the skin, and certain adhesive properties. Therefore, current research by domestic and international scholars primarily focuses on optimizing electrode stiffness, strain range, and adhesion strength using composite material control and physical model-driven geometric structure strategies. This review mainly summarizes the methods for electrode material control and geometric structure design.

[0003] Over the past few decades, various organic conductive and semiconductor materials have been developed and applied to skin electrodes, such as hydrogels and nanocomposites. Ren et al. from the National University of Singapore developed a skin electrode with high conductivity (545 S / cm) and low elastic modulus (5 MPa) 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 forces on dry and wet skin reached 0.41 N / cm and 0.56 N / cm, respectively, demonstrating 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, as shown in [example image]. Figure 1 As shown in (b), the adhesion strength with pigskin reached 5.2 kPa. Majidi et al. at Carnegie Mellon University sprayed a layer of silver nanoparticles and an indium gallium alloy mixture onto a PDMS substrate, as shown in [example image]. Figure 1 As shown in (c), the device exhibits a failure strain as high as 118%, making it suitable for highly flexible and soft skin surfaces. Miyashita et al. from the Tokyo Institute of Technology integrated gold nanoparticles onto the surface of a polystyrene-butadiene copolymer film using a printing method, such as... Figure 1 As shown in (d), a neural electrode with mechanical properties similar to biological tissue was prepared, with an elastic modulus of only 45 MPa.

[0004] However, epidermal electrodes made from such materials suffer from poor electrical properties and are easily affected by environmental factors, such as water evaporation from the hydrogel. Therefore, the design of epidermal electrodes based on metallic materials has become an alternative approach.

[0005] Metallic materials are inherently hard, possessing low strain and high elastic modulus, making them unsuitable for direct use in the human body. Therefore, scholars both domestically and internationally have developed metallic electrodes with excellent mechanical properties based on serpentine structures. For example, Professor Yu Xingge of City University of Hong Kong proposed a biomimetic spiderweb-like electrode, such as... Figure 1 As shown in (e), not only was the effective working area of ​​the electrode increased to 51.34%, but a 30% biaxial stretch of the electrode was also 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%, demonstrating 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 interconnection manner, which combines large area coverage, high filling rate, excellent tensile strength and flexibility. Throughout the entire beating and contraction cycle of the heart, the electrode array remains attached to the surface of the heart.

[0006] However, while these deformable structures possess macroscopic tensile properties, they cannot simultaneously achieve good microscopic compliance and a large active surface area. For example, fractal structures, such as... Figure 2 As shown in (a), when the ratio of linewidth w to thickness t is greater than 1, the stretched metal electrode will undergo out-of-plane buckling, resulting in a microscopic gap at the electrode-skin interface, such as... Figure 2 As shown in (b), poor conformal attachment is observed. Furthermore, when the linewidth w to thickness t ratio is less than 1, a lower active surface area is created, resulting in higher contact impedance. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes a biomimetic paper-cut-shaped epidermal electrode for dynamic electrocardiogram monitoring of the human body and its manufacturing method.

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

[0009] A biomimetic paper-cut-shaped epidermal electrode for dynamic electrocardiogram monitoring is disclosed. The electrode comprises a three-electrode, single-lead, multi-layer structure, including a top polydimethylsiloxane thin film layer, an adhesion layer, a copper functional layer, copper interconnects, and a bottom polyimide insulating layer, arranged sequentially. The copper functional layer features a biomimetic paper-cut structure, consisting of four sub-units connected in series via four-sided circular arc flexible hinges, forming a deformable closed loop internally. Each sub-unit comprises an N×N rigid dot array connected to adjacent... The structure comprises a retractable flexible hinge between dots, wherein the retractable flexible hinge adopts a hexagonal pattern resembling a snake's belly; the copper metal interconnect is serpentine; the top polydimethylsiloxane film layer is tightly attached and fixedly connected to one side of the adhesive layer, the copper metal functional layer is tightly attached and fixedly connected to the other side of the adhesive layer, the copper metal interconnect is fixedly connected to the pads of the copper metal functional layer by adhesive bonding, and is also tightly attached and fixedly connected to the adhesive layer; the bottom polyimide insulating layer is tightly attached and fixedly connected to the other side of the copper metal interconnect.

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

[0011] Furthermore, the ratio of the single-sided wall thickness of the stretchable flexible hinge to the thickness of the copper metal functional layer is 1.

[0012] The second objective of this invention is achieved through the following technical solution:

[0013] A method for preparing a biomimetic paper-cut-shaped epidermal electrode for human dynamic electrocardiogram monitoring includes the following steps:

[0014] Step 1: Use femtosecond laser integrated processing to fabricate copper metal interconnects and a bottom polyimide insulating layer;

[0015] Step 2: Fabricate the copper functional layer using femtosecond laser processing;

[0016] Step 3: Prepare the top polydimethylsiloxane thin film layer;

[0017] Step 4: Prepare an adhesion layer below the top polydimethylsiloxane film layer;

[0018] Step 5: Adhere the copper interconnects made in Step 1 onto the adhesive layer prepared in Step 4;

[0019] Step 6: Adhere the copper metal functional layer prepared in Step 2 onto the adhesion layer prepared in Step 4;

[0020] Step 7: Solder the pads of the copper metal functional layer electrode and the copper metal interconnect to fix them in place; then use a carbon dioxide laser to process the biomimetic paper-cut skin electrode according to the outline drawing of the adhesion layer, and remove excess material.

[0021] Moreover, step 1 includes:

[0022] 1.1 First, place an appropriate amount of polyvinyl alcohol and deionized water in a beaker and stir thoroughly to prepare a polyvinyl alcohol solution;

[0023] 1.2 Then clean the glass substrate with alcohol and fix it on the spin coating equipment;

[0024] 1.3 Next, the polyvinyl alcohol solution is spin-coated onto the cleaned glass substrate at a speed of 800 r / min and dried at high temperature to form an adhesive;

[0025] 1.4 Then, the 0.01mm thick PI copper-clad foil is laid flat on the treated glass substrate;

[0026] 1.5 Finally, according to the drawing of the copper interconnect, the copper interconnect is processed by femtosecond laser and excess material is removed.

[0027] Furthermore, step 2 includes:

[0028] 2.1 First, place an appropriate amount of polyvinyl alcohol and deionized water in a beaker and stir 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 onto the cleaned glass substrate at a speed of 800 r / min and dried at high temperature to form an adhesive;

[0031] 2.4 Then, the 0.01mm thick copper foil is laid flat on the treated glass substrate;

[0032] 2.5 Finally, according to the drawings of the biomimetic paper-cutting structure, the copper metal functional layer is processed by femtosecond laser and excess material is removed.

[0033] Furthermore, step 3 includes:

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

[0035] 3.2 Then, the glass beaker containing the mixed solution is placed in a vacuum apparatus for degassing.

[0036] 3.3 Next, spin-coat the treated mixed solution onto the glass substrate that has been cleaned with alcohol at a speed of 600 r / min, and place it in an oven to bake at a high temperature of 120°C for 10 min to cure and form a top polydimethylsiloxane film layer.

[0037] Furthermore, step 4 includes:

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

[0039] 4.2 Then, the glass beaker containing the mixed solution is placed in a vacuum device for degassing.

[0040] 4.3 Next, spin-coat the treated mixed solution onto the glass substrate treated in step 3 at a speed of 600 r / min, and place it in an oven to bake at a high temperature of 120°C for 10 min to cure and form an adhesion layer on the underside of the top polydimethylsiloxane film layer.

[0041] Furthermore, step 5 includes:

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

[0043] 5.2 Then, apply 3M water-soluble tape to the surface of the copper interconnect in a flat manner to transfer the copper interconnect on the glass substrate to the tape surface;

[0044] 5.3 Next, apply the tape containing copper interconnects to the glass substrate treated in step 4 in a flat manner;

[0045] 5.3 Finally, immerse it in water to dissolve and remove the 3M water-soluble tape, allowing the copper interconnects to adhere to the adhesive layer.

[0046] Moreover, step 6 includes

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

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

[0049] 6.3 Next, apply the tape containing the copper metal functional layer to the glass substrate treated in step 5 in a flat manner, and align the positions of the electrode and interconnect pads.

[0050] 6.4 Finally, immerse it in water to dissolve and remove the 3M water-soluble tape, allowing the copper metal functional layer to adhere to the adhesive layer.

[0051] The advantages and positive effects of this invention are as follows:

[0052] 1. The biomimetic paper-cutting shaped epidermal electrode of the present invention adopts a biomimetic paper-cutting design. Under the condition of stretching rate less than 30%, on the one hand, the electrode deformation is mainly reversible elastic deformation of the hinge part without obvious buckling phenomenon, and the rigid point has almost no strain, which has good microscopic compliance; on the other hand, the mechanical properties of the electrode such as stretching range, stretching stiffness, and bending stiffness are adapted to the skin.

[0053] 2. The active surface area of ​​the biomimetic paper-cutting-shaped skin electrode of the present invention is as high as 32.66%, which is 10.83% higher than that of the active surface area of ​​the fractal structure under the same linewidth w to thickness t ratio.

[0054] 3. The present invention has a scientific and reasonable structural design, low cost, and can reasonably realize dynamic electrocardiogram monitoring of the human body, achieving good usage results. Attached Figure Description

[0055] Figure 1 In the image: 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 for detecting physiological electrical signals in the human body; 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 surface of the brain; 1e is a schematic diagram of a biomimetic 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 In the middle: 2a is a schematic diagram of the fractal structure electrode (top) and the locally magnified (bottom) structure; 2b is a SEM image of the electrode that undergoes out-of-plane buckling;

[0057] Figure 3 3a is a schematic diagram of a biomimetic paper-cutting structure, with the upper left image showing an armadillo and the lower left image showing a snake; 3b is a schematic diagram of the structure of copper metal interconnects.

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

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

[0060] Figure 6 In the middle: 6a is the strain distribution cloud map of the paper-cut flexible hinge under 15% tension; 6b is the stress-strain curve of the paper-cut flexible hinge under uniaxial tension; 6c is the SEM image of the undeformed paper-cut flexible hinge magnified 50 times; 6d is the SEM image of the broken paper-cut flexible hinge magnified 50 times.

[0061] Figure 7 In the middle: 7a is the stress distribution cloud map of the bionic paper-cutting structure electrode when it is subjected to 30% tension; 7b is the stress distribution cloud map of the bionic paper-cutting structure electrode when it is subjected to 130° bending; 7c is the stress-strain curve of the bionic paper-cutting structure electrode when it is subjected to tension.

[0062] Figure 8 In the middle: 8a (Ⅰ) is a schematic diagram of the adhesive film pull-out test, (Ⅱ) is a photograph of the adhesive film pull-out test; 8b is a pull-out test curve of the adhesive film under dry and wet conditions; in 8c, the left image is the image of the electrode without deformation, the middle image is the image of the electrode under compression, and the right image is the image of the electrode under torsion.

[0063] Figure 9 A schematic diagram of the process for monitoring human dynamic electrocardiogram using epidermal electrodes;

[0064] Figure 10 In the middle: 10a is the human electrocardiogram measured by the bionic paper-cut-shaped skin electrode during cycling; 10b is the human electrocardiogram measured by the bionic paper-cut-shaped skin electrode after cycling stops; 10c is the human electrocardiogram measured by the fractal structure skin electrode during cycling; 10d is the human electrocardiogram measured by the fractal structure skin electrode after cycling stops.

[0065] Figure 11 This is a schematic diagram of the overall structure of the biomimetic paper-cut-shaped skin electrode. Detailed Implementation

[0066] The structure of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that these embodiments are descriptive and not limiting.

[0067] Please see the section on a biomimetic paper-cut-shaped epidermal electrode for dynamic electrocardiogram monitoring in humans. Figures 3-11The invention features a multi-layered structure comprising a top polydimethylsiloxane film layer, an adhesive layer, a copper metal functional layer, copper metal interconnects, and a bottom polyimide insulating layer, arranged sequentially. 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. The copper metal functional layer has a biomimetic paper-cutting structure, which is composed of a combination of snakeskin and wren shell biomimetic patterns. Figure 3 As shown in (a), the copper metal interconnect structure has 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 adhesive layer, the copper metal functional layer is tightly attached to and fixedly connected to the other side of the adhesive layer, the copper metal interconnect is fixedly connected to the pads of the copper metal functional layer in an adhesive manner, and is also tightly attached to and fixedly connected to the adhesive layer, and the bottom polyimide insulating layer is tightly attached to and fixedly connected to the other side of the copper metal interconnect.

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

[0069] The conformal fit between flexible devices and skin is typically related to the total energy of the system, which includes the bending energy, tensile energy, adhesive energy, and strain energy of the device and skin. This total energy is generally related to the stiffness, tensile range, and adhesive strength of the flexible device. Therefore, this invention achieves conformal adhesion to the skin by adjusting the stiffness, strain range, and adhesive strength of the epidermal electrodes.

[0070] Copper foil, due to its high electrical properties, high chemical stability, antibacterial properties, and low cost, has become one of the best materials for epidermal electrode functional layers. However, copper foil is inherently soft and almost non-stretchable, making it unable to conformally adhere to the flexible skin with its non-zero Gaussian curvature. Therefore, this invention, by drawing inspiration from snake skin and wren shell structures, hollows out a 0.01 mm thick copper foil to prepare a biomimetic paper-cutting structure copper metal functional layer. This layer not only achieves good conformal adhesion to the skin but also boasts an active surface area of ​​up to 32.66%.

[0071] Considering the softness of the skin, based on the structure of the Diarmuid's carapace, a 0.01mm × 11mm × 11mm copper foil was designed into a 6×6 rigid dot array structure (with a spacing of 2mm), such as... Figure 5 As shown in (a). Secondly, considering the strain range of the skin, a flexible paper-cut hinge based on the hexagonal pattern of the snake's belly was designed to connect the array of dots, such as... Figure 5 As shown in (b), with stretching and compression, the "V"s at both ends of the hexagon open and close in a rotational manner. Furthermore, considering the effect of the linewidth to thickness ratio on buckling, the linewidth w (in the paper-cut flexible hinge structure) is... Figure 4 The code indicates that the ratio of the "line width w" (i.e., the wall thickness on one side of the hinge) to the thickness (i.e., the thickness of the copper functional layer) is designed to be 1. However, the copper functional layer, composed of a paper-cut flexible hinge and an array of dots, such as... Figure 5 As shown in (c), it cannot match the elastic modulus of the skin (5kPa–140MPa) nor meet the skin's 30% tensile deformation. To reduce the electrode's tensile stiffness and increase its elongation, inspired by the "V"-shaped deformation of hexagonal patterns, [the electrode is designed to...]. Figure 5 (c) The paper-cut flexible hinges in ①-④ are replaced with circular arc flexible hinges. The resulting biomimetic paper-cut structure electrodes are as follows: Figure 5 As shown in (d). Figure 5 (e) and Figure 5 (f) respectively demonstrates the deformation principle of the biomimetic paper-cutting structure electrode when subjected to tension and compression.

[0072] To evaluate the conformal fit between the biomimetic paper-cut structure electrode and skin, the mechanical properties of the paper-cut structure electrode were analyzed using finite element analysis and experiments. First, a uniaxial tensile finite element simulation of the paper-cut flexible hinge was performed to study the magnitude and distribution of its strain. The results are as follows: Figure 6 As shown in (a), simulation results show that under 15% uniaxial tension, the strain of the paper-cut flexible hinge is concentrated in the V-shaped part of the structure, with a maximum true strain value of only 0.365. Next, a tensile fracture test was conducted on the paper-cut flexible hinge, and the results are as follows... Figure 6As shown in (b). The results show that its maximum tensile strength can reach 26.35%. Furthermore, experimental evaluations of the microscopic compliance of the paper-cut flexible hinge were conducted. Throughout the tensile fracture process, Figure 6 (d) indicates that the flexible hinge only has a tear near the rigid connection point, compared to the undeformed ( Figure 6 (c)) The remaining parts do not show obvious out-of-plane buckling deformation and have excellent micro-compliance.

[0073] Figure 7 (a) and Figure 7 (b) Finite element simulations of the tensile and bending deformations of the biomimetic paper-cutting structure electrode, respectively. The simulations show that when the electrode's elongation does not exceed 30% ( Figure 7 (a) The stress is mainly concentrated in the circular arc flexible hinge, and the maximum Mises stress is much smaller than the yield strength of copper, 155.35 MPa. When the electrode is subjected to a 130° bending deformation ( Figure 7 (b) The stress is also concentrated in the circular 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 biomimetic paper-cut structure electrode exhibits a highly nonlinear behavior, such as... Figure 7 As shown in (c), when the elongation rate is less than 30%, the electrode tensile stiffness is only 3.8 × 10⁻³ N / mm, exhibiting excellent flexibility. In this stage, the electrode mainly undergoes rotational deformation due to the low-stiffness circular arc flexible hinge, while the high-stiffness paper-cutting flexible hinge remains undeformed. When the elongation rate exceeds 30%, the rotational deformation of the circular arc flexible hinge reaches its limit, and the paper-cutting flexible hinge gradually undergoes tensile deformation. Furthermore, the tensile stiffness of the electrode rapidly increases until the elongation rate reaches 53.82%, at which point fracture begins.

[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-cutting structure electrode can be adapted to the skin.

[0075] A 0.01mm thick copper functional layer is difficult to adhere tightly to the skin through physical interaction alone; external force is required to ensure that the copper functional layer can match the local surface morphology of the skin. Furthermore, considering the influence of sweat on adhesion, this invention adds a sweat-resistant adhesion layer to the copper functional layer.

[0076] Polydimethylsiloxane (PDMS) possesses excellent chemical stability, thermal stability, and biocompatibility, making it commonly used in biological dressings. However, during the curing process, the addition of a certain amount of polyethylene glycol to the PDMS base agent and curing agent solution weakens the catalytic effect of platinum, causing the PDMS to form a semi-crosslinked network, resulting in excellent flexibility, wet adhesion, and tensile strength. Therefore, this invention selects PDMS base agent, curing agent, and polyethylene glycol to prepare the adhesive layer.

[0077] To evaluate the adhesion strength of the adhesive layer under dry / wet skin conditions, a mixture of polydimethylsiloxane curing agent and polyethylene glycol in a 2:8 ratio was poured into the polydimethylsiloxane base and cured. The cured adhesive film (0.3mm × 30mm × 30mm) was then tested for adhesion strength to human arm skin using a pull-out test method, as described below. Figure 8 (a)(Ⅰ)~(Ⅱ), the test curves are as follows Figure 8 As shown in (b), the adhesion strength of the adhesive film under dry and wet skin conditions reached 8.64 kPa and 5.08 kPa, respectively, ensuring that the copper metal functional layer adhered tightly to the skin surface. Furthermore, when one side of the adhesive film was integrated with the biomimetic paper-cutting structure electrode, it was necessary to isolate the adhesion on the other side. Therefore, a 0.1 mm thick non-adhesive film, namely a fully cross-linked polydimethylsiloxane film, was added to this side of the adhesive layer.

[0078] Finally, the biomimetic paper-cut structure electrodes, adhesive layer, and polydimethylsiloxane film were integrated together to evaluate the adaptability of the electrode patch to the skin surface. Under conditions of skin stretching and torsional deformation, the electrode patch maintained a tight adhesion to the skin, such as... Figure 8 As shown in (c).

[0079] Method for preparing biomimetic paper-cut-shaped skin electrodes:

[0080] Step 1: First, place an appropriate amount of polyvinyl alcohol and deionized water in a beaker and stir thoroughly to prepare a polyvinyl alcohol solution. Then, clean the glass substrate with alcohol and fix it on a spin coater. Next, spin coat the polyvinyl alcohol solution onto the cleaned glass substrate at a speed of 800 rpm and dry it at high temperature to form an adhesive. Then, attach a 0.01 mm thick PI copper-clad foil to the treated glass substrate in a flat manner. Finally, according to the copper interconnect pattern, use a femtosecond laser to integrally fabricate the copper interconnect and the underlying polyimide insulating layer, and remove excess material.

[0081] Step 2: First, place an appropriate amount of polyvinyl alcohol and deionized water in a beaker and stir thoroughly to prepare a polyvinyl alcohol solution. Then, clean the glass substrate with alcohol and fix it on a spin coater. Next, spin coat the polyvinyl alcohol solution onto the cleaned glass substrate at a speed of 800 rpm and dry it at high temperature to form an adhesive. Then, attach a 0.01 mm thick copper foil to the treated glass substrate in a flat manner. Finally, according to the biomimetic paper-cutting structure drawing, use a femtosecond laser to process the copper metal biomimetic paper-cutting 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 thoroughly to prepare a mixed solution. Then, place the glass beaker containing the mixed solution into a vacuum device for degassing. Next, spin-coat the treated mixed solution onto a glass substrate that has been cleaned with alcohol at a speed of 600 rpm, and place it in an oven to bake at 120°C for 10 minutes to cure 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 thoroughly to prepare a mixed solution. Then, place the glass beaker containing the mixed solution into a vacuum device for degassing. Next, spin-coat the treated mixed solution onto the glass substrate treated in Step 3 at a speed of 600 rpm, and place it in an oven to bake at a high temperature of 120°C for 10 minutes to cure and form an adhesion film on the surface of the polydimethylsiloxane film.

[0084] Step 5: First, immerse the copper interconnects processed in Step 1, which are adhered to the glass substrate, in water to dissolve the polyvinyl alcohol adhesive. Then, apply 3M water-soluble tape in a flat manner to the surface of the copper interconnects to transfer the copper interconnects from the glass substrate to the tape surface. Next, apply the tape containing the copper interconnects in a flat manner to the glass substrate treated in Step 4. Finally, immerse it in water to remove the 3M water-soluble tape by dissolving it.

[0085] Step 6: First, immerse the copper biomimetic paper-cut structure electrode, processed in Step 2 and adhered to the glass substrate, in water to dissolve the polyvinyl alcohol adhesive. Then, apply 3M water-soluble tape in a flat manner to the surface of the copper biomimetic paper-cut structure electrode to transfer the electrode from the glass substrate to the tape surface. Next, apply the tape containing the copper biomimetic paper-cut structure electrode in a flat manner to the glass substrate treated in Step 5, aligning the electrode and interconnect pads. Finally, immerse it in water to dissolve and remove the 3M water-soluble tape.

[0086] Step 7: First, solder the electrodes and interconnect pads together to secure them. Then, use a CO2 laser to fabricate a biomimetic paper-cut-shaped outer electrode according to the outline drawing of the adhesion layer, and remove excess material.

[0087] Application Examples:

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

[0089] To evaluate the monitoring quality of dynamic electrocardiogram (ECG) during human cycling, this invention attaches biomimetic paper-cut-shaped and fractal-structured skin electrodes of the same linewidth to the left chest of the human body. The collected ECG data is then transmitted to a PC via an ADS1292 development board, enabling the recording and analysis of dynamic ECG data. Figure 9 As shown. One of the challenges in monitoring dynamic electrocardiograms is motion artifacts caused by slippage, poor consistency, and mechanical mismatch between the device and the skin interface, resulting in a decrease in the signal-to-noise ratio. Figure 10 (a) This image shows the ECG measurement results of the bionic paper-cut-shaped epidermal electrode during cycling, with a signal-to-noise ratio of 23.1176 dB, compared to 26.6881 dB when stationary. Figure 10 (b)), a decrease of 3.5705 dB. The fractal electrode used for device comparison, and the ECG results measured during cycling are as follows: Figure 10 As shown in (c), the signal-to-noise ratio is 19.6418 dB, compared to 22.3579 dB when the person was stationary. Figure 10 (d)), decreased by 2.7161 dB. With the increase of motion artifacts, compared with the fractal structure electrode, the biomimetic paper-cut skin electrode showed obvious R, S, and T waves, and had strong resolution.

[0090] Although embodiments and drawings of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations 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 biomimetic paper-cut-shaped epidermal electrode for dynamic electrocardiogram monitoring in humans, characterized in that: The biomimetic paper-cutting shaped surface electrode is a three-electrode single-conductor multi-layer composite structure, including a top polydimethylsiloxane thin film layer, an adhesion layer, a copper metal functional layer, copper metal interconnects, and a bottom polyimide insulating layer arranged sequentially. The copper metal functional layer has a biomimetic paper-cutting structure, which is composed of four groups of sub-units connected in series by four-sided circular arc flexible hinges, forming a deformable closed loop inside. Each group of sub-units consists of an N×N rigid dot array and a retractable flexible hinge connecting adjacent dots. The retractable flexible hinge adopts a hexagonal pattern hinge form similar to the belly of a snake. The copper metal interconnects are serpentine. The top polydimethylsiloxane thin film layer is tightly attached and fixedly connected to one side of the adhesion layer, and the copper metal functional layer is tightly attached and fixedly connected to the other side of the adhesion layer. The copper metal interconnects are fixedly connected to the pads of the copper metal functional layer by adhesive bonding, and are also tightly attached and fixedly connected to the adhesion layer. The bottom polyimide insulating layer is tightly attached and fixedly connected to the other side of the copper metal interconnects.

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

3. The biomimetic paper-cut-shaped epidermal electrode for human dynamic electrocardiogram monitoring according to claim 1, characterized in that: The ratio of the single-sided wall thickness of the stretchable flexible hinge to the thickness of the copper metal functional layer is 1.

4. A method for preparing a biomimetic paper-cut-shaped epidermal electrode for human dynamic electrocardiogram monitoring as described in any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Use femtosecond laser integrated processing to fabricate copper metal interconnects and a bottom polyimide insulating layer; Step 2: Fabricate the copper functional layer using femtosecond laser processing; Step 3: Prepare the top polydimethylsiloxane thin film layer; Step 4: Prepare an adhesion layer below the top polydimethylsiloxane film layer; Step 5: Adhere the copper interconnects made in Step 1 onto the adhesive layer prepared in Step 4; Step 6: Adhere the copper metal functional layer prepared in Step 2 onto the adhesion layer prepared in Step 4; Step 7: Solder the pads of the copper metal functional layer electrode and the copper metal interconnects to fix them in place; then use a carbon dioxide laser to process the biomimetic paper-cut skin electrode according to the outline drawing of the adhesion layer, and remove excess material.

5. The method for preparing the biomimetic paper-cut-shaped epidermal electrode for human 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 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 onto the cleaned glass substrate at a speed of 800 r / min and dried at high temperature to form an adhesive; 1.4 Then, the 0.01mm thick PI copper-clad foil is laid flat on the treated glass substrate; 1.5 Finally, according to the drawing of the copper metal interconnect, the copper metal interconnect and the bottom polyimide insulation layer are processed by femtosecond laser, and the excess material is removed.

6. The method for preparing the biomimetic paper-cut-shaped epidermal electrode for human dynamic electrocardiogram monitoring according to claim 5, characterized in that, Step 2 includes: 2.1 First, place an appropriate amount of polyvinyl alcohol and deionized water in a beaker and stir 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 onto the cleaned glass substrate at a speed of 800 r / min and dried at high temperature to form an adhesive; 2.4 Then, the 0.01mm thick copper foil is laid flat on the treated glass substrate; 2.5 Finally, according to the drawings of the biomimetic paper-cutting structure, the copper metal functional layer is processed by femtosecond laser and excess material is removed.

7. The method for preparing the biomimetic paper-cut-shaped epidermal electrode for human dynamic electrocardiogram monitoring according to claim 6, characterized in that, Step 3 includes: 3.1 First, place the polydimethylsiloxane main agent and curing agent in a beaker at a ratio of 10:1 and stir thoroughly to prepare a mixed solution; 3.2 Then, the glass beaker containing the mixed solution is placed in a vacuum apparatus for degassing. 3.3 Next, spin-coat the treated mixed solution onto the alcohol-cleaned glass substrate at a speed of 600 r / min, and place it in an oven to bake at a high temperature of 120°C for 10 min to cure and form a top polydimethylsiloxane film layer.

8. The method for preparing the biomimetic paper-cut-shaped epidermal electrode for human dynamic electrocardiogram monitoring according to claim 7, characterized in that, Step 4 includes: 4.1 First, place the polydimethylsiloxane curing agent and polyethylene glycol in a beaker containing the main agent at a ratio of 2:8, and stir thoroughly to prepare a mixed solution; 4.2 Then, the glass beaker containing the mixed solution is placed in a vacuum device for degassing. 4.3 Next, spin-coat the treated mixed solution onto the glass substrate treated in step 3 at a speed of 600 r / min, and place it in an oven to bake at a high temperature of 120°C for 10 min to cure and form an adhesion layer on the underside of the top polydimethylsiloxane film layer.

9. The method for preparing the biomimetic paper-cut-shaped epidermal electrode for human dynamic electrocardiogram monitoring according to claim 8, characterized in that, Step 5 includes: 5.1 First, immerse the copper metal interconnects processed in step 1 and adhered to the glass substrate in water to dissolve the polyvinyl alcohol adhesive; 5.2 Then, apply 3M water-soluble tape to the surface of the copper interconnect in a flat manner to transfer the copper interconnect on the glass substrate to the tape surface; 5.3 Next, apply the tape containing copper interconnects to the glass substrate treated in step 4 in a flat manner; 5.3 Finally, immerse it in water to dissolve and remove the 3M water-soluble tape, allowing the copper interconnects to adhere to the adhesive layer.

10. The method for preparing the biomimetic paper-cut-shaped epidermal electrode for human dynamic electrocardiogram monitoring according to claim 9, characterized in that, Step 6 includes: 6.

1. Immerse the copper metal functional layer processed in step 2 and adhered to the glass substrate in water to dissolve the polyvinyl alcohol adhesive. 6.2 Then, apply 3M water-soluble tape to the surface of the copper functional layer in a flat manner to transfer the copper functional layer on the glass substrate to the surface of the tape. 6.3 Next, apply the tape containing the copper metal functional layer to the glass substrate treated in step 5 in a flat manner, and align the positions of the electrode and interconnect pads. 6.4 Finally, immerse it in water to dissolve and remove the 3M water-soluble tape, allowing the copper metal functional layer to adhere to the adhesive layer.

Images