Preparation method of gel bio-patch with low-frequency filtering property and electrode

Abstract

The application discloses a preparation method of a gel biological patch with low-frequency filtering characteristics and an electrode, and comprises the following steps: adding carrageenan into distilled water, adding metal salt, heating and dissolving to obtain a carrageenan solution; adding carbon nanotubes into the carrageenan solution, stirring and dispersing, and then ultrasonic crushing to obtain a conductive carrageenan solution; pouring the conductive carrageenan solution into a silica gel mold, and solidifying to obtain the gel biological patch with low-frequency filtering characteristics. The ECG electrode pasted with the gel biological patch with low-frequency filtering characteristics can filter low-frequency signals of 1-56 Hz and reserve high-frequency signals, and the effect of adjustable filtering frequency is achieved. When the electrode is used to test an electrocardiogram, stable electrocardiogram signals can be obtained when walking, shaking and jumping.

Description

Technical Field

[0001] This invention relates to the field of flexible electronic patch technology, specifically to a method for preparing a gel biopatch with low-frequency filtering characteristics and an electrode. Background Technology

[0002] Biopatch electrodes are typically attached directly to the skin to test signals such as electrocardiograms (ECG), electromyograms (EMG), and electroencephalograms (EEGs), thereby monitoring the organism's health status and aiding in disease prevention. For example, during an ECG test, the subject needs to remain completely still and stable. Currently used medical electrodes for ECG measurement are significantly affected by even slight movement, and cannot be used during movement. This is because the low-frequency vibration signals generated by movement interfere with the test results, leading to inaccurate readings. However, some situations require measuring bioelectrical signals during movement, such as muscle signal changes in athletes during exercise or continuous ECG monitoring for heart disease patients—tests that traditional medical electrodes cannot handle. Computer filtering methods can filter out some overlapping bioelectrical signals, resulting in inaccurate results. Therefore, a physical filtering method that can shield vibration signals, using low-frequency damping vibration isolation materials to record only bioelectrical signals, is needed. Summary of the Invention

[0003] In order to overcome the problems in the prior art, the present invention aims to provide a method for preparing a gel biopatch with low-frequency filtering characteristics and an electrode. The electrocardiogram signal measured by the patch prepared by the method is stable and can play a good filtering role in various exercise tests.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing a gel biopatch with low-frequency filtering characteristics includes the following steps:

[0006] Carrageenan is added to distilled water, then a metal salt is added, and the mixture is heated to dissolve, thus obtaining a carrageenan solution.

[0007] Carbon nanotubes were added to a carrageenan solution, stirred and dispersed, and then ultrasonically broken to obtain a conductive carrageenan solution.

[0008] A conductive carrageenan solution is poured into a silicone mold and cured to obtain a gel biopatch with low-frequency filtering properties.

[0009] Furthermore, the metal salt is potassium chloride, ferric nitrate, or lithium chloride.

[0010] Furthermore, when the metal salt is potassium chloride, the amount of potassium chloride is 1‰ of the amount of carrageenan.

[0011] Furthermore, when the metal salt is ferric nitrate, the amount of ferric nitrate is 0.3‰ of the amount of carrageenan.

[0012] Furthermore, when the metal salt is lithium chloride, the amount of lithium chloride is 1‰ of the amount of carrageenan.

[0013] Furthermore, the carrageenan solution contains 0.5-6% carrageenan by mass.

[0014] Furthermore, the length of the carbon nanotubes ranges from 200 nm to 50 μm.

[0015] Furthermore, the mass of the carbon nanotubes is 1% of the mass of carrageenan.

[0016] A gel biopatch electrode with low-frequency filtering effect includes an ECG electrode with a gel biopatch with low-frequency filtering characteristics prepared by the method attached thereto.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] This invention uses carrageenan as the main gelling material and metal salt ions as a physical crosslinking agent. Controlling the mass fraction of doped carbon nanotubes increases the gel's conductivity, making its resistance similar to that of medical electrodes. All materials used are non-toxic, biocompatible, and will not cause immune rejection reactions with the skin. The gel preparation method is simple and efficient, resulting in a smooth, pore-free finished product that ensures electrode stability. Due to the unique double-helix molecular structure of carrageenan, the formed carrageenan exhibits a spring-like damping effect. Vibration sweep frequency experiments showed that the gel did not vibrate below 50Hz, but surface vibration began above 60Hz, indicating that the initial frequency for signal transmission is 50-60Hz, corresponding to the phase transition point of 56Hz obtained from shear rheology. This invention features a simple and low-cost preparation process, is safe, and uses non-toxic, harmless, and biocompatible raw materials. The gel electrode prepared by this invention has good damping effect and effectively filters low-frequency motion signals.

[0019] Furthermore, the mass fraction of κ-carrageenan in the carrageenan solution is 0.5-6%, which allows for the adjustment of different filtering frequencies.

[0020] Furthermore, due to the -OSO3 on κ-carrageenan - The groups coordinate with metal ions to form ionic bonds and crosslink. Different amounts of metal salt ions with different valence states are required to match. Therefore, in this invention, the amount of potassium chloride is 1‰ of the amount of κ-carrageenan, the amount of ferric nitrate is 0.3‰ of the amount of κ-carrageenan, and the amount of lithium chloride is 1‰ of the amount of κ-carrageenan.

[0021] Furthermore, the carbon nanotubes, with a mass of 1% of that of κ-carrageenan, can achieve resistance values ​​close to those of commercial electrodes.

[0022] The gel biopatch prepared by this invention can be directly adhered to disposable medical electrodes, which is simple and efficient. When the electrode is placed on the skin surface using traditional methods, the measured ECG signals during sitting and standing are more stable than those without a filter electrode, with a near-horizontal baseline. During dynamic measurements such as stretching, walking, swaying back and forth, swaying left and right, and small jumps, the originally chaotic signals are transformed into clear, stable signals similar to those measured at rest. Therefore, the damping gel prepared by this method has good applications in real life. For example, by attaching this gel electrode to test biosignals during movement, it can be widely and cost-effectively prepared and applied to commercial disposable medical electrodes. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] in,

[0025] Figure 1 These are photographs of the electrodes prepared in the embodiments of the present invention; wherein, 1 is an ECG electrode and 2 is a molecular double helix hydrogel;

[0026] Figure 2 This is a schematic diagram of the electrode testing method for ECG signals used in an embodiment of the present invention;

[0027] Figure 3 The figures show the vibration absorption and isolation properties of the molecular double helix gel and polydimethylsilane prepared in the embodiments of the present invention. In the figures (a)-(d), the hydrogel absorbs all the vibration after the stainless steel ball falls, so that the steel ball does not bounce. In the figures (e)-(h), the steel ball bounces when it falls on the polydimethylsilane.

[0028] Figure 4 The changes in modulus and hysteresis angle of the molecular double helix gel prepared in the embodiments of the present invention with vibration frequency are clearly distinguished at 56Hz.

[0029] Figure 5 The recovery performance of the molecular double helix gel prepared in the embodiments of the present invention at different vibration frequencies is shown in the figure. It was tested for 30s cycles three times at 1% and 100% strain, respectively. Under low frequency conditions, the storage modulus is higher than the loss modulus, and under high frequency conditions, the loss modulus is higher than the storage modulus. The change is rapid and stable.

[0030] Figure 6 The mechanical properties of the molecular double helix gel prepared in the embodiments of the present invention, wherein (a) is the cyclic tensile curve under large strain cyclic stretching, (b) is the elastic modulus of each cycle, and (c) is the hysteresis energy of each cycle.

[0031] Figure 7 The following are ECG signal diagrams obtained by electrode testing in this embodiment of the invention, wherein (a) is the ECG signal measured by commercial gel in different states; and (b) is the ECG signal measured after adding damping gel. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] This invention is not limited to the listed embodiments; these embodiments are only used to explain the invention.

[0034] Taking ECG signal testing as an example, this invention provides a method for preparing a gel biopatch with low-frequency filtering characteristics and an electrode, comprising the following steps:

[0035] Step 1: Prepare the hot carrageenan solution:

[0036] κ-carrageenan is added to distilled water, followed by the addition of a metal salt (potassium chloride, ferric nitrate, or lithium chloride). The mixture is then heated in an 80°C water bath and mechanically stirred for 10 minutes until fully dissolved, yielding a carrageenan solution. The mass fraction of κ-carrageenan in the solution is 0.5-6%, allowing for adjustment of different filtering frequencies. This is due to the -OSO3 content on κ-carrageenan. - The groups coordinate with metal ions to form ionic bonds and crosslink. Different amounts of metal salt ions with different valence states need to be used to match: for example, the amount of potassium chloride is 1‰ of the amount of κ-carrageenan, the amount of ferric nitrate is 0.3‰ of the amount of κ-carrageenan, and the amount of lithium chloride is 1‰ of the amount of κ-carrageenan.

[0037] Step 2: Disperse carbon nanotubes in carrageenan solution:

[0038] Carbon nanotubes with lengths ranging from 200 nm to 50 μm were added to a carrageenan solution, thoroughly stirred and dispersed, then ultrasonically broken up to remove air bubbles, resulting in a conductive carrageenan solution; the ultrasonic breaking time was 2 minutes. The mass of the carbon nanotubes was 1% of the mass of κ-carrageenan, achieving a resistance value close to that of commercially available electrodes.

[0039] Step 3: The gel curing and setting process:

[0040] The conductive carrageenan solution is poured into a silicone mold of the desired shape and left to stand at room temperature (25°C) for curing. Once the temperature drops to the same level as room temperature, a conductive gel with a specific shape is obtained, which is a gel biopatch with low-frequency filtering characteristics.

[0041] A gel biopatch electrode with low-frequency filtering effect includes an ECG electrode to which the aforementioned gel biopatch with low-frequency filtering properties is adhered. Specifically, the prepared conductive gel is adhered to the electrode position of a disposable medical ECG electrode (electrocardiogram electrode) and gently pressed to obtain the gel biopatch electrode with low-frequency filtering effect.

[0042] The gel biopatch electrode with low-frequency filtering effect prepared by this invention has excellent low-frequency filtering effect, and the results obtained during electrocardiogram (ECG) testing are stable. The electrode's filtering frequency is adjustable, and it can filter low-frequency signals from 1-56Hz while retaining high-frequency signals. When using this electrode to test ECGs, stable ECG signals can be obtained even while walking, swaying, jumping, etc.

[0043] Example 1

[0044] The first step is to prepare a hot carrageenan solution;

[0045] Place 2g of κ-carrageenan and 0.003g of potassium chloride in 100mL of distilled water, and stir at 800r / min for 10min in a magnetic stirrer under water bath heating at 80℃ to fully dissolve them and obtain a carrageenan solution.

[0046] The second step is to prepare a gel solution with added carbon nanotubes;

[0047] Weigh 0.02g of 20μm long carbon nanotubes and slowly pour them into a fully dissolved carrageenan solution. Stir at 800r / min for 10min until the solution is clear and there is no obvious layering. Take out the solution and place it in an ultrasonic crusher. Sonicate for 2min to disperse the carbon nanotubes evenly and remove air bubbles in the solution to obtain a conductive carrageenan solution.

[0048] The third step is to solidify the gel.

[0049] Prepare a φ20*1mm silicone mold in advance and clean it with distilled water; pour the conductive carrageenan solution into the mold, cover it with a lid, let it stand for 30 minutes, and after the gel solidifies, you will get a conductive gel with low-frequency filtering effect, and then take it out.

[0050] Step 4: Preparation of gel bioelectrodes

[0051] The conductive gel with low-frequency filtering effect is removed and attached to the purchased commercial disposable 3M patch electrode (commercial ECG electrode), and gently pressed to obtain a gel biopatch electrode with low-frequency filtering characteristics.

[0052] The biogel electrode prepared in this embodiment is as follows: Figure 1 As shown, the molecular double helix hydrogel 2 (i.e., conductive gel with low-frequency filtering effect) attached to the commercial ECG electrode 1 has a simple structure and is easy to prepare.

[0053] In this embodiment, the electrode bonding method used for testing ECG signals is as follows: Figure 2 As shown, the gel biopatch electrode with low-frequency filtering characteristics prepared in this invention is attached to a commercial ECG electrode. The commercial ECG electrode is connected to a computer via a microcontroller, which shows no difference from the traditional medical testing attachment method.

[0054] The vibration isolation performance of the molecular double helix hydrogel with filtering properties prepared in this embodiment is as follows: Figure 3 As shown in (a)-(h), a stainless steel ball with a diameter of 9.5 mm was thrown onto a 2 mm thick hydrogel surface and did not bounce. Compared to the commonly used soft material polydimethylsilane, which bounces several times, this hydrogel exhibits excellent vibration absorption and isolation effects.

[0055] The rheological properties of the molecular double helix hydrogel with filtering characteristics prepared in this embodiment under 1% strain vibration conditions are as follows: Figure 4 As shown, the modulus and hysteresis angle of the gel remain stable when the vibration frequency is below 56 Hz. Above 56 Hz, the hysteresis angle begins to decrease, indicating that vibration begins to be transmitted in the gel. Therefore, the gel prepared by this invention can exhibit filtering characteristics in the 0-56 Hz range and transmit vibration signals above 56 Hz.

[0056] In this embodiment, the rotational rheometer was used to test the modulus transformation of the hydrogel under shear vibration conditions, as follows: Figure 5 As shown, the gel was cycled for 30 seconds under 1% and 100% strain conditions, for a total of 3 cycles. At the 1% strain condition, the storage modulus was greater than the loss modulus, indicating that the gel existed in solid form. Under the 100% strain condition, the loss modulus was greater than the storage modulus, indicating that the gel transitioned to viscoelasticity. During this transition, the modulus changed rapidly and the process was stable, suggesting that the gel is suitable for biosensor applications where vibration signals frequently change.

[0057] The mechanical properties of the molecular double helix hydrogel with filtering characteristics prepared in this embodiment are as follows: Figure 6As shown in (a), (b), and (c), under maximum strain conditions, the cyclic tensile test did not result in a significant decrease in elastic modulus; instead, it showed a relatively slow increase. This demonstrates that the gel will not suffer mechanical damage after prolonged cyclic use and even exhibits some reinforcement. This proves that the gel is suitable for use in biological joints that frequently experience large strains.

[0058] The test results of the biogel electrode prepared in this embodiment are as follows: Figure 7 As shown in (a) and (b), static and dynamic tests were conducted under standing and sitting conditions, respectively. Comparing the ECG test results of commercially available ECG electrodes and those with added biogel electrodes, it can be seen that both methods produce very stable and clear results in static tests. However, the commercially available ECG electrode performs poorly during walking, stretching, and shaking, exhibiting significant noise signals. In contrast, the results obtained during movement after adding the prepared molecular double-helix gel show significant improvement, with clear signals and almost no fluctuations. This demonstrates the excellent performance of the gel in practical applications.

[0059] Example 2

[0060] 0.5 g of κ-carrageenan and potassium chloride were placed in 100 mL of distilled water and stirred at 800 rpm for 10 min in a water bath at 80 °C to ensure complete dissolution, thus obtaining a carrageenan solution. The amount of potassium chloride used was 1‰ of the molar amount of κ-carrageenan.

[0061] The second step is to prepare a gel solution with added carbon nanotubes;

[0062] Weigh 0.02g of 200nm long carbon nanotubes and slowly pour them into a fully dissolved carrageenan solution. Stir at 800r / min for 10min until the solution is clear and there is no obvious layering. Take out the solution and place it in an ultrasonic crusher. Sonicate for 2min to disperse the carbon nanotubes evenly and remove air bubbles in the solution to obtain a conductive carrageenan solution.

[0063] The third step is to solidify the gel.

[0064] Prepare a φ20*1mm silicone mold in advance and clean it with distilled water; pour the conductive carrageenan solution into the mold, cover it with a lid, let it stand for 30 minutes, and after the gel solidifies, you will get a conductive gel with low-frequency filtering effect. Take it out to get a gel biopatch with low-frequency filtering characteristics.

[0065] Example 3

[0066] Place 6g of κ-carrageenan and ferric nitrate in 100mL of distilled water, and stir at 800r / min for 10min in a water bath at 80℃ to ensure complete dissolution, thus obtaining a carrageenan solution. The amount of ferric nitrate used is 0.3‰ of the molar amount of κ-carrageenan.

[0067] The second step is to prepare a gel solution with added carbon nanotubes;

[0068] Weigh 0.02g of 50μm long carbon nanotubes and slowly pour them into a fully dissolved carrageenan solution. Stir at 800r / min for 10min until the solution is clear and there is no obvious layering. Take out the solution and place it in an ultrasonic crusher. Sonicate for 2min to disperse the carbon nanotubes evenly and remove air bubbles in the solution to obtain a conductive carrageenan solution.

[0069] The third step is to solidify the gel.

[0070] Prepare a φ20*1mm silicone mold in advance and clean it with distilled water; pour the conductive carrageenan solution into the mold, cover it with a lid, let it stand for 30 minutes, and after the gel solidifies, you will get a conductive gel with low-frequency filtering effect. Take it out to get a gel biopatch with low-frequency filtering characteristics.

[0071] Example 4

[0072] 4 g of κ-carrageenan and lithium chloride were placed in 100 mL of distilled water and stirred at 800 rpm for 10 min in a water bath at 80°C to ensure complete dissolution, thus obtaining a carrageenan solution. The amount of lithium chloride used was 1‰ of the molar amount of κ-carrageenan.

[0073] The second step is to prepare a gel solution with added carbon nanotubes;

[0074] Weigh 0.02 g of 1 μm long carbon nanotubes and slowly pour them into a fully dissolved carrageenan solution. Stir at 800 r / min for 10 min until the solution is clear and there is no obvious layering. Take out the solution and place it in an ultrasonic crusher. Sonicate for 2 min to disperse the carbon nanotubes evenly and remove air bubbles in the solution to obtain a conductive carrageenan solution.

[0075] The third step is to solidify the gel.

[0076] Prepare a φ20*1mm silicone mold in advance and clean it with distilled water; pour the conductive carrageenan solution into the mold, cover it with a lid, let it stand for 30 minutes, and after the gel solidifies, you will get a conductive gel with low-frequency filtering effect. Take it out to get a gel biopatch with low-frequency filtering characteristics.

[0077] This invention is not limited to the ECG results measured in the embodiments of this invention; it is also applicable to the testing of bioelectrical signals, electroencephalogram (EEG) signals, acoustic signals, and other signals.

Claims

1. A method for preparing a gel biopatch with low-frequency filtering characteristics, characterized in that, Includes the following steps: Carrageenan is added to distilled water, then a metal salt is added, and the mixture is heated to dissolve, thus obtaining a carrageenan solution. Carbon nanotubes were added to a carrageenan solution, stirred and dispersed, and then ultrasonically broken to obtain a conductive carrageenan solution. A conductive carrageenan solution is poured into a silicone mold and cured to obtain a gel biopatch with low-frequency filtering properties. The carrageenan solution contains 0.5-6% carrageenan by mass. The mass of carbon nanotubes is 1% of the mass of carrageenan.

2. The method for preparing a gel biopatch with low-frequency filtering characteristics according to claim 1, characterized in that, The metal salts are potassium chloride, ferric nitrate, or lithium chloride.

3. The method for preparing a gel biopatch with low-frequency filtering characteristics according to claim 2, characterized in that, When the metal salt is potassium chloride, the amount of potassium chloride is 1‰ of the amount of carrageenan.

4. The method for preparing a gel biopatch with low-frequency filtering characteristics according to claim 2, characterized in that, When the metal salt is ferric nitrate, the amount of ferric nitrate is 0.3‰ of the amount of carrageenan.

5. The method for preparing a gel biopatch with low-frequency filtering characteristics according to claim 2, characterized in that, When the metal salt is lithium chloride, the amount of lithium chloride is 1‰ of the amount of carrageenan.

6. The method for preparing a gel biopatch with low-frequency filtering characteristics according to claim 1, characterized in that, The length of carbon nanotubes ranges from 200 nm to 50 μm.

7. A gel biopatch electrode with low-frequency filtering effect, characterized in that, The ECG electrode includes an ECG electrode with a gel biopatch having low-frequency filtering characteristics prepared by any one of claims 1-6.

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