A flexible dry electrode against electromagnetic and motion artifact interference and a preparation method thereof

Abstract

The application discloses a flexible dry electrode with electromagnetic and motion artifact interference resistance and a preparation method thereof. The electrode comprises an electrode sensing layer, the upper surface of the electrode sensing layer is covered with an insulation layer, and the upper surface of the insulation layer is covered with a shielding layer. A composite conductive material CMPVA is prepared from modified polyvinyl alcohol MPVA and conductive nanomaterial. The electrode sensor layer is obtained by spin coating CMPVA on a glass substrate and drying at room temperature. The insulation layer is obtained by spin coating MPVA on the electrode sensor layer and drying at room temperature. The shielding layer is obtained by spin coating the composite conductive material CMPVA on the insulation layer and drying at room temperature. The shape of the electrode is etched by laser, and the electrode is peeled off from the substrate. The technical problems of low flexibility, large electrode area, unstable contact between the electrode and the skin, low signal-to-noise ratio of collected signals and the like of the prior art electrode are solved.

Description

Technical Field

[0001] This invention belongs to the field of medical device technology, and in particular relates to a flexible dry electrode that is resistant to electromagnetic interference and motion artifacts and its preparation method. Background Technology

[0002] Bioelectrical signals recorded from the human body surface (e.g., electrocardiogram, electroencephalogram, electromyography, and electrooculogram) play a crucial role in the diagnosis of human diseases and health monitoring. Long-term recording of bioelectrical signals can provide rich and accurate physiological information, which is beneficial for health monitoring and disease diagnosis. Wet electrodes are typically used for recording bioelectrical signals. Wet electrodes require the use of conductive adhesive, but over time, the conductive adhesive dehydrates, leading to increased contact resistance between the electrode and the skin, thus causing distortion of the recorded bioelectrical signals. Therefore, wet electrodes are not suitable for long-term bioelectrical signal recording. Dry electrodes, on the other hand, do not require conductive adhesive and can be used for long-term recording of bioelectrical signals. Bioelectrical signals have low frequencies (ECG, EEG, and electrooculogram frequency range: 0-100 Hz; EMG frequency range: 20-8000 Hz) and low amplitudes (5 μV-5 mV), making them susceptible to interference from external electromagnetic signals. Furthermore, during human movement, the relative movement between the dry electrode and the skin makes the recorded bioelectrical signals susceptible to motion artifacts. Therefore, current dry electrodes generally suffer from low signal quality.

[0003] A search revealed Chinese patent CN107411735A, which discloses a flexible dry electrode for bioelectrical signals and its preparation method. The electrode includes a flexible dry electrode body and an electrical connector. The flexible dry electrode body is made of a flexible conductive composite material, with a substrate of conductive rubber or conductive silicone, and fillers of one or more of carbon-based or metal-based conductive fillers. However, this patent suffers from problems such as large size, inconvenience in use, low electrode conductivity, and poor quality of recorded bioelectrical signals.

[0004] A search revealed Chinese patent CN103271736A, which discloses a flexible capacitive electrocardiogram (ECG) dry electrode and its processing method. The electrode comprises a sensor layer, an insulating layer, a first shielding layer, and a second shielding layer. However, this patent has the following drawbacks: low flexibility and a large electrode area, resulting in unstable contact between the electrode and the skin and consequently a low signal-to-noise ratio. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a flexible dry electrode that is resistant to electromagnetic and motion artifact interference and its preparation method, so as to solve the technical problems of low flexibility, large electrode area, and unstable contact between the electrode and the skin, which leads to low signal-to-noise ratio of the acquired signal.

[0006] The technical solution of this invention is:

[0007] A flexible dry electrode resistant to electromagnetic interference and motion artifacts, the flexible dry electrode comprising an electrode sensing layer, an insulating layer covering the upper surface of the electrode sensing layer, and a shielding layer covering the upper surface of the insulating layer.

[0008] The thickness of the electrode sensing layer, insulating layer, and shielding layer is 0.1-10 μm.

[0009] The shielding layer is prepared using a conductive composite material made of modified polyvinyl alcohol and conductive nanomaterials.

[0010] Conductive nanomaterials include conductive polymers, MXene, carbon nanotubes, graphene, silver nanowires, or gold nanowires.

[0011] A method for fabricating a flexible dry electrode resistant to electromagnetic interference and motion artifacts, the method comprising:

[0012] Step 1: Prepare composite conductive material CMPVA by combining modified polyvinyl alcohol (MPVA) with conductive nanomaterials;

[0013] Step 2: Using glass as a substrate, spin-coat CMPVA onto the glass substrate and dry it at room temperature to obtain the electrode sensor layer;

[0014] Step 3: Spin-coat MPVA onto the electrode sensor layer and dry at room temperature to obtain an insulating layer;

[0015] Step 4: Spin-coat the insulating layer with composite conductive material CMPVA and dry at room temperature to obtain the shielding layer;

[0016] Step 5: Use a laser to etch the shape of the electrode and peel it off from the substrate.

[0017] The preparation method of modified polyvinyl alcohol (MPVA) includes: dissolving 2g of polyvinyl alcohol in a mixture of 40ml of deionized water, hydrochloric acid, and dimethyl sulfoxide; the volume ratio of deionized water to dimethyl sulfoxide is 1:3, and the hydrochloric acid is 0.01 M; stirring at 70℃ for 1h, adding 0.32g of nonanal, and reacting at 50℃ for 1h to obtain nonyl-PAV; reacting 0.1g of nonyl-PAV with 0.05g of α-cyclodextrin to obtain modified polyvinyl alcohol (MPVA).

[0018] The method for preparing the composite conductive material is as follows: 1g of MPVA is dissolved in 20ml of deionized water and then mixed with the conductive material to obtain the composite conductive material.

[0019] The conductive material is 10 mg of carbon nanotubes.

[0020] The conductivity and electromagnetic shielding properties of composite conductive materials can be adjusted by adding conductive materials of different mass fractions to MPVA.

[0021] The beneficial effects of this invention are:

[0022] The flexible dry electrode of this invention incorporates a shielding layer, which reduces interference from external electromagnetic noise and improves the quality of the recorded signal.

[0023] The flexible dry electrode shielding layer and sensing layer of this invention are prepared using a composite conductive material composed of modified polyvinyl alcohol and conductive nanomaterials. Conductive nanomaterial fillers are added to the modified polyvinyl alcohol, and the conductivity of the composite material can be adjusted by controlling the content of the conductive nanomaterial fillers and the doping method of the fillers in the modified polyvinyl alcohol. Therefore, the composite material can be used as the shielding layer and sensing layer of the electrode.

[0024] In this invention, the insulating layer is made of modified polyvinyl alcohol, which is a polymer with good insulation and biocompatibility and is easy to process.

[0025] The structure described above in this invention includes a shielding layer and a self-adhesive sensing layer, which improves the signal-to-noise ratio of electrode-recorded bioelectrical signals in terms of both electromagnetic interference resistance and motion artifacts resistance, thus solving the problem of low signal-to-noise ratio caused by the susceptibility of dry electrode-recorded bioelectrical signals to electromagnetic interference and motion artifacts.

[0026] The main material of the three-layer structure of the present invention is modified polyvinyl alcohol. Modified polyvinyl alcohol has amphiphilic properties, can absorb and expel water vapor, which helps to keep the skin dry and is suitable for long-term wearable use.

[0027] The sensing layer of this invention has self-adhesive properties, which can maintain stable contact with the skin even during movement, thus helping to reduce interference from motion artifacts.

[0028] The flexible bioelectric dry electrode of the present invention, which is resistant to electromagnetic and motion artifact interference, can be stably attached to the skin without the need for external force, and is suitable for long-term recording of bioelectric signals.

[0029] This technology solves the technical problems of low flexibility, large electrode area, and unstable contact between the electrode and the skin, which lead to low signal-to-noise ratio of the acquired signal. Attached Figure Description

[0030] Figure 1 This is a schematic cross-sectional view of the electrode structure of the present invention;

[0031] Figure 2 This is a schematic diagram of the electrode structure of the present invention;

[0032] Figure 3This is a flowchart of the electrode fabrication process according to a preferred embodiment of the present invention;

[0033] Figure 4 This is a flowchart of the electrode fabrication process according to a preferred embodiment of the present invention;

[0034] The markings in the diagram represent: 1 for the electrode sensing layer, 2 for the insulating layer, and 3 for the shielding layer. Detailed Implementation

[0035] Reference Figure 1-2 The diagram shows a preferred embodiment of a flexible bioelectric dry electrode that is resistant to electromagnetic interference and motion artifacts. The diagram includes: an electrode sensing layer 1, an insulating layer 2, and a shielding layer 3.

[0036] In practical implementation, the electrodes in the electrode structure can be of any shape as needed; the electrode size is not limited and can be adjusted according to the actual situation. When the electrode is applied to bioelectrical signal recording, one side of the electrode sensing layer 1 is fixed to an appropriate position on the skin; the above-mentioned electrode structure has flexibility and self-adhesive properties, fits tightly to the skin, and stably records bioelectrical signals, allowing for long-term recording of bioelectrical signals.

[0037] A further provision in this embodiment is that the shielding layer is prepared using a conductive composite material composed of modified polyvinyl alcohol and conductive nanomaterials. The conductive nanomaterials can be any one of conductive polymers, MXene, carbon nanotubes, graphene, silver nanowires, or gold nanowires. To improve the flexibility of the electrode, the electrode sensing layer 1, insulating layer 2, and shielding layer 3 should not be too thick; the thickness of each layer should be controlled within the range of 0.1-10 μm for optimal electrode flexibility.

[0038] In one specific embodiment, reference is made to Figure 3 The diagram shows a fabrication process for a flexible bioelectrical dry electrode that is resistant to electromagnetic interference and motion artifacts. The specific steps are as follows:

[0039] Step 1: Complete the modification of polyvinyl alcohol (PVA) and prepare a composite conductive material (CMPVA) by combining the modified polyvinyl alcohol (MPVA) with conductive materials.

[0040] Modification of polyvinyl alcohol (PVA): Specifically, 2g of PVA was dissolved in a mixture of 40ml deionized water, hydrochloric acid, and dimethyl sulfoxide (volume ratio of deionized water to dimethyl sulfoxide is 1:3, hydrochloric acid is 0.01 M). The mixture was stirred at 70℃ for 1h, then 0.32g of nonanal was added, and the reaction was carried out at 50℃ for 1h to obtain nonyl-containing PVA (Nonyl-PAV). 0.1g of Nonyl-PAV and 0.05g of α-cyclodextrin were reacted to obtain modified PVA (MPVA). MPVA possesses amphiphilic properties (hydrophilic-hydrophobic), and when prepared into a film, it is both breathable and adhesive. The hydrophilicity of the film allows it to absorb water, while its hydrophobicity allows water to evaporate from its surface. The stratum corneum is the outermost layer of the epidermis, composed of keratinocytes and lipids. The hydrophobic nonyl groups can anchor the lipid bilayer membrane of keratinocytes, enabling the MPVA film to adhere to the skin.

[0041] 1g of MPVA was dissolved in 20ml of deionized water and then mixed with a conductive material (carbon nanotubes, 10mg) to obtain a composite conductive material (CMPVA). The conductivity and electromagnetic shielding properties of the composite material were adjusted by adding different mass fractions of conductive material to MPVA.

[0042] Step 2: Using glass as a substrate, spin-coat CMPVA onto the glass substrate. Control the thickness by adjusting the spin speed and time, and dry at room temperature to obtain the sensor layer. (Refer to...) Figure 3 As shown in (a).

[0043] Step 3: Spin-coat MPVA solution onto the sensor layer, controlling the thickness by adjusting the spin speed and time, and dry at room temperature to obtain the insulation layer pattern. (Refer to...) Figure 3 As shown in (b).

[0044] Step 4: Spin-coat the insulating layer with a composite conductive material, controlling the thickness by adjusting the spin speed and time, and dry at room temperature to obtain the shielding layer. (Refer to...) Figure 3 As shown in (c).

[0045] Step 5: Use a laser to etch the shape of the electrode, then peel the electrode off from the substrate, referring to... Figure 3 As shown in (d).

[0046] In another embodiment, reference is made to Figure 4 As shown, a flexible bioelectrical dry electrode resistant to electromagnetic interference and motion artifacts is prepared, which can be carried out according to the following steps:

[0047] Step 1: Complete the modification of polyvinyl alcohol (PVA) and the preparation of composite materials (CMPVA) of modified polyvinyl alcohol (MPVA) and conductive materials.

[0048] 2g of polyvinyl alcohol was dissolved in a mixture of 40ml deionized water, hydrochloric acid, and dimethyl sulfoxide (volume ratio of deionized water to dimethyl sulfoxide: 1:3, hydrochloric acid: 0.01 M). The mixture was stirred at 70℃ for 1h, and then 0.32g of nonanal was added. The reaction was carried out at 50℃ for 1h to obtain nonyl-containing polyvinyl alcohol (Nonyl-PAV). 0.1g of Nonyl-PAV and 0.05g of α-cyclodextrin were reacted to obtain modified polyvinyl alcohol (modified-PVA, MPVA). 1g of MPVA was dissolved in 20ml of deionized water and then mixed with 10mg of MXene to obtain a composite conductive material (CMPVA).

[0049] The conductivity and electromagnetic shielding properties of the composite material were further adjusted by adding conductive materials of different mass fractions to the MPVA.

[0050] Step 2: Pour composite conductive material (CMPVA) into the silicone mold and dry at room temperature to form a sensing layer. The thickness is controlled by adjusting the amount of CMPVA injected into the mold, referring to... Figure 4 As shown in (a).

[0051] Step 3: Pour modified polyvinyl alcohol (MPVA) into the mold and allow it to dry at room temperature to form an insulating layer. The thickness is controlled by adjusting the amount of MPVA injected into the mold. Figure 4 As shown in (b).

[0052] Step 4: Pour composite conductive material (CMPVA) into the mold and allow it to dry at room temperature to form shielding layer 3. The thickness is controlled by adjusting the amount of CMPVA injected into the mold. Figure 4 As shown in (c).

[0053] Step 5: Remove the electrode from the mold, referring to... Figure 4 As shown in (d).

[0054] The above embodiments of the present invention modify polyvinyl alcohol and prepare flexible dry electrodes resistant to electromagnetic interference and motion artifacts using spin coating, etching, or casting processes. The electrodes of the above embodiments of the present invention have a shielding layer and self-adhesion, improving the signal-to-noise ratio of the electrode for recording bioelectrical signals in terms of both electromagnetic interference and motion artifact resistance. Furthermore, the electrodes of the above embodiments of the present invention are flexible dry electrodes, capable of long-term stable recording of bioelectrical signals.

Claims

1. A flexible dry electrode resistant to electromagnetic interference and motion artifacts, characterized in that: The flexible dry electrode includes an electrode sensing layer (1), an insulating layer (2) covering the upper surface of the electrode sensing layer (1), and a shielding layer (3) covering the upper surface of the insulating layer (2).

2. The flexible dry electrode resistant to electromagnetic and motion artifact interference according to claim 1, characterized in that: The thickness of the electrode sensing layer (1), insulating layer (2) and shielding layer (3) is 0.1-10 μm.

3. The flexible dry electrode resistant to electromagnetic and motion artifact interference according to claim 1, characterized in that: The shielding layer (3) is prepared using a conductive composite material made of modified polyvinyl alcohol and conductive nanomaterials.

4. The flexible dry electrode resistant to electromagnetic interference and motion artifacts according to claim 3, characterized in that: Conductive nanomaterials include conductive polymers, MXene, carbon nanotubes, graphene, silver nanowires, or gold nanowires.

5. The method for preparing a flexible dry electrode resistant to electromagnetic interference and motion artifacts as described in claim 1, characterized in that: The method includes: Step 1: Prepare composite conductive material CMPVA by combining modified polyvinyl alcohol (MPVA) with conductive nanomaterials; Step 2: Using glass as a substrate, spin-coat CMPVA onto the glass substrate and dry it at room temperature to obtain the electrode sensor layer; Step 3: Spin-coat MPVA onto the electrode sensor layer and dry at room temperature to obtain an insulating layer; Step 4: Spin-coat the insulating layer with composite conductive material CMPVA and dry at room temperature to obtain the shielding layer; Step 5: Use a laser to etch the shape of the electrode and peel it off from the substrate.

6. The method for preparing a flexible dry electrode resistant to electromagnetic and motion artifact interference according to claim 5, characterized in that: The preparation method of modified polyvinyl alcohol (MPVA) includes: dissolving 2g of polyvinyl alcohol in a mixture of 40ml of deionized water, hydrochloric acid, and dimethyl sulfoxide; the volume ratio of deionized water to dimethyl sulfoxide is 1:3, and the hydrochloric acid is 0.01 M; stirring at 70℃ for 1h, adding 0.32g of nonanal, and reacting at 50℃ for 1h to obtain nonyl-PAV; reacting 0.1g of nonyl-PAV with 0.05g of α-cyclodextrin to obtain modified polyvinyl alcohol (MPVA).

7. The method for preparing a flexible dry electrode resistant to electromagnetic interference and motion artifacts according to claim 6, characterized in that: The method for preparing the composite conductive material is as follows: 1g of MPVA is dissolved in 20ml of deionized water and then mixed with the conductive material to obtain the composite conductive material.

8. The method for preparing a flexible dry electrode resistant to electromagnetic interference and motion artifacts according to claim 6, characterized in that: The conductive material is 10 mg of carbon nanotubes.

9. The method for preparing a flexible dry electrode resistant to electromagnetic and motion artifact interference according to claim 7, characterized in that: The conductivity and electromagnetic shielding properties of composite conductive materials can be adjusted by adding conductive materials of different mass fractions to MPVA.

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