A flexible conductive polymer and method for preparing a stretchable sensor

Abstract

This invention belongs to the field of novel conductive polymer materials, specifically relating to a flexible conductive polymer and method for preparing a stretchable sensor. The flexible conductive polymer of this invention simultaneously possesses adhesion, conductivity, stretchability, and low resistance change characteristics. It is prepared solely by blending a flexible conductive polymer material, a polyol containing two or more hydroxyl groups, and a polar organic solvent. The flexible conductive polymer material is poly(3,4-ethylenedioxythiophene):polystyrene sulfonate; the polyol containing two or more hydroxyl groups constitutes 1%-15% by weight in the flexible conductive polymer; and the polar organic solvent constitutes 4%-5% by weight in the flexible conductive polymer.

Description

Technical Field

[0001] This invention belongs to the field of novel conductive polymer materials, specifically relating to a flexible conductive polymer and method for preparing a stretchable sensor. Background Technology

[0002] Flexible electronics is a promising research area, offering new device applications for energy storage and bioelectronics, such as motion sensors, stretchable displays, and electrodes for physiological recording or muscle stimulation. In bioelectronics, conductive polymer electrodes based on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) have shown many advantages in skin recording, such as stable conductivity, inherent mechanical flexibility, and solution-processable properties. However, because PEDOT:PSS has a core-shell structure, with the insulating PSS encapsulating PEDOT, the conductivity of the original PEDOT:PPS film is only 0.2–0.35 S cm⁻¹. -1 This is insufficient for many applications requiring high conductivity. Furthermore, due to the rigid conjugated backbone of PEDOT:PSS, pure PEDOT:PSS films exhibit very limited mechanical deformation, making them unsuitable for direct application in skin-worn electronic devices. Numerous studies have been conducted to improve the properties of PEDOT:PSS. For example, conductivity can be increased through thermal annealing or by adding organic solvents or acid solutions. Another example is the introduction of plasticizers, which improves both conductivity and tensile properties of PEDOT:PSS.

[0003] Patent application CN2022106558162, entitled "A Dual-Network PEDOT Flexible Conductive Polymer and Its Preparation Method," discloses a dual-network PEDOT flexible conductive polymer. This polymer, based on PEDOT:PSS, incorporates a primary network polymer (including polyvinyl alcohol, polyethylene glycol, waterborne polyurethane, etc.) providing the main mechanical load-bearing capacity and a secondary network polymer (including polyethylene glycol diacrylate, acrylic acid, 2-hydroxyethyl acrylate, etc.) to further enhance the mechanical and electrical properties of the electrode material. The patented material has an elongation at break of 17-80% and a Young's modulus ranging from 12-140 MPa. However, this material lacks self-adhesion, resulting in high interfacial impedance when applied to wearable bioelectrodes, making it difficult to accurately capture bioelectrical signals. Furthermore, this material has shortcomings in terms of its mechanical properties matching those of skin tissue. While the inclusion of materials such as polyethylene glycol and waterborne polyurethane improves the elongation at break, the Young's modulus (12-140 MPa) differs significantly from that of skin (0.5-1.95 MPa), making it difficult to establish conformal contact. Therefore, this material presents significant challenges when used to fabricate wearable bioelectrodes.

[0004] In summary, it is necessary to develop a low-cost polymer electrode material that simultaneously possesses suitable electrical conductivity, mechanical properties, self-adhesion, and low resistance variation characteristics for the fabrication of directly wearable bioelectrodes, in order to alleviate the shortcomings of existing technologies. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a flexible conductive polymer and method for preparing a stretchable sensor, the specific technical solution of which is as follows.

[0006] A flexible conductive polymer for preparing a stretchable sensor is disclosed. The flexible conductive polymer simultaneously possesses adhesion, conductivity, stretchability, and low resistance change properties. The flexible conductive polymer is prepared by blending a flexible conductive polymer material, a polyol containing two or more hydroxyl groups, and a polar organic solvent. The flexible conductive polymer material is poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). The polyol containing two or more hydroxyl groups constitutes 1%-15% by weight in the flexible conductive polymer. The polar organic solvent constitutes 4%-5% by weight in the flexible conductive polymer.

[0007] As a preferred embodiment, the stretchable sensor may be a stretchable dry electrode.

[0008] Furthermore, the polyol sugar alcohol containing two or more hydroxyl groups includes maltitol, lactulose, raffinose, or combinations thereof.

[0009] Furthermore, the polar organic solvent includes one or more of ethylene glycol, methanol, and / or dimethyl sulfoxide.

[0010] Furthermore, the ratio of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate is 1:2.5.

[0011] Furthermore, the blending method includes one or more of mechanical stirring, vortex stirring, and / or ultrasonic vibration.

[0012] The above-mentioned flexible conductive polymer is used in the fabrication of wearable, stretchable sensors.

[0013] Furthermore, the stretchable sensor is a self-supporting film with a thickness of 30-50μm, which can be directly adhered to the skin as a wearable health monitoring sensor (it can be used after connecting an external power source).

[0014] Preferably, the wearable health monitoring sensor mainly refers to a sensor suitable for wearing on active parts such as joints. When the wearable health monitoring sensor prepared with the flexible conductive polymer of the present invention is used on active parts such as joints, it will not produce a large change in resistance with the movement of the limbs (because the flexible conductive polymer provided by the present invention has the characteristics of adhesion, conductivity, stretchability and low resistance change), thus not affecting the quality of subsequent signal acquisition.

[0015] The method for preparing the above-mentioned self-supporting thin film includes the following steps:

[0016] Step 1: Add a polyol sugar alcohol containing two or more hydroxyl groups to the poly(3,4-ethylenedioxythiophene):polystyrene sulfonate dispersion and stir until completely dissolved. The mass ratio of the two materials is poly(3,4-ethylenedioxythiophene):polystyrene sulfonate dispersion:polyol sugar alcohol is 10:1.

[0017] Step 2: Add a polar organic solvent to the solution obtained in Step 1) to obtain a polymer blend solution. The mass ratio of the three materials is 20:2:1 for poly(3,4-ethylenedioxythiophene):polystyrene sulfonate dispersion:polyol sugar alcohol:polar organic solvent.

[0018] Step 3: Drop the polymer blend solution obtained in step 2) onto the release paper substrate or glass substrate and let it stand for 6-12 hours to remove air bubbles. Then bake at 40-65℃ for 3-5 hours to obtain a self-supporting film that can be worn directly.

[0019] In some embodiments, in steps 1) and 2) above, the mass ratio of the three materials is 100:1:5 for poly(3,4-ethylenedioxythiophene):polystyrene sulfonate dispersion:polyol sugar alcohol:polar organic solvent.

[0020] Furthermore, the polyol sugar alcohol containing two or more hydroxyl groups includes maltitol, lactulose, raffinose, or combinations thereof; the polar organic solvent includes one or more of ethylene glycol, methanol, and / or dimethyl sulfoxide.

[0021] Furthermore, in steps 1) and 2), a polyol sugar alcohol containing two or more hydroxyl groups is added to the poly(3,4-ethylenedioxythiophene):polystyrene sulfonate dispersion and stirred at 800-1500 rpm for 0.5-2 hours. Then, a polar organic solvent is added and stirred at 800-1500 rpm for 10-30 minutes.

[0022] Beneficial technical effects

[0023] 1) This invention provides a flexible conductive polymer for preparing stretchable sensors. This conductive polymer must simultaneously possess adhesion, conductivity, stretchability, and low resistance change characteristics. Therefore, sensors prepared using this flexible conductive polymer are particularly suitable for use in moving parts such as joints. Because this flexible conductive polymer is soft, its Young's modulus range closely matches the range of Young's modulus of skin (0.5-1.95 MPa), and it also has good adhesion properties, allowing it to adhere to the skin. Therefore, when used as a sensor at the skin interface, it has the advantage of conformal contact, avoiding large resistance changes and improving the sensor's sensitivity and stability. Furthermore, since the sugar alcohol material used to prepare this flexible conductive polymer is maltitol, lactulose, raffinose, or a combination thereof, these sugar alcohols are all edible and absorbable materials for the human body. Therefore, the prepared flexible conductive polymer has high biocompatibility and will not cause skin irritation or discomfort even after prolonged wear.

[0024] 2) This invention also provides a wearable health monitoring sensor prepared using the aforementioned flexible conductive polymer. This sensor is essentially a self-supporting thin film, prepared from only three materials: poly(3,4-ethylenedioxythiophene): polystyrene sulfonate, a polyol containing two or more hydroxyl groups, and an organic solvent. The composition is simple, and the preparation process is straightforward. This self-supporting thin film exhibits adhesion of 0.25-0.6 N / cm when in contact with a glass interface and 0.15-0.48 N / cm when in contact with skin. It also possesses tensile strength ranging from 20% to 62% and a conductivity of 20-111 S / cm.

[0025] In summary, the flexible conductive polymer provided by this invention has a simplified composition, containing only three materials. Through a simple process, it can be further prepared into a self-supporting film that can be directly worn at joints, thus serving as a wearable health monitoring sensor. This flexible conductive polymer provides adhesion, stretchability, conductivity, and low resistance variation, and also exhibits excellent biocompatibility. In other words, a simplified formulation yields a novel material that combines multiple comprehensive properties, filling a gap in the industry compared to existing technologies that require multiple formulations to obtain materials with outstanding performance in one aspect but lacking or deficient performance in others (e.g., high conductivity, low adhesion, or high rigidity). Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0027] Figure 1 The conductivity characteristics of the polymer electrode material prepared in one embodiment of the present invention;

[0028] Figure 2 The mechanical properties of the polymer material prepared in one embodiment of the present invention;

[0029] Figure 3 This is a photograph of a self-supporting thin film prepared in one embodiment of the present invention;

[0030] Figure 4 The above is the electromyography signal test result of the self-supporting membrane prepared in one embodiment of the present invention;

[0031] Figure 5 This refers to the change in resistance of the self-supporting thin film prepared in one embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] In this document, "and / or" includes any and all combinations of one or more of the listed related items.

[0034] In this article, "multiple" means two or more, that is, it includes two, three, four, five, etc.

[0035] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0036] As used in this specification, the term "about" typically means + / - 5% of the value, more typically + / - 4%, more typically + / - 3%, more typically + / - 2%, even more typically + / - 1%, even more typically + / - 0.5% of the value.

[0037] In this specification, certain embodiments may be disclosed in a range-bound format. It should be understood that this "range-bound" description is merely for convenience and brevity and should not be construed as a rigid limitation on the disclosed range. Therefore, the description of the range should be considered as having specifically disclosed all possible subranges and independent numerical values ​​within those ranges. For example, range The description should be considered as having specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as individual numbers within this range, such as 1, 2, 3, 4, 5, and 6. The above rules apply regardless of the breadth of the range.

[0038] Example 1

[0039] Transfer 1 mL of PH1000 dispersion (i.e., PEDOT:PSS aqueous solution with a solid content of 1.3 wt%, the same below) into a glass bottle, add a magnetic stir bar and stir at room temperature at 800 rpm. Weigh 111 mg of maltitol solid and slowly add it to the PH1000 dispersion, stir for 1 hour until the solid is completely dissolved, then add ethylene glycol to the solution to obtain a polymer blend solution, and stop stirring. Transfer 120 μL of the prepared polymer blend solution dropwise onto a release paper substrate or glass substrate and let it stand for 6-12 hours to remove air bubbles, then bake at 40-65℃ for 3-5 hours to obtain a self-supporting film that can be directly used for wear.

[0040] The self-supporting film prepared in this embodiment has an electrical conductivity of 110 S / cm, an adhesion of 0.4 N / cm, and a tensile strength of 62%.

[0041] Example 2

[0042] This embodiment provides a sugar alcohol-PEDOT:PSS film treated with a water washing process.

[0043] 1 mL of PH1000 dispersion was transferred to a glass bottle, and a magnetic stir bar was added. The mixture was stirred at 800 rpm at room temperature. 111 mg of maltitol solid was weighed and slowly added to the PH1000 dispersion. The mixture was stirred for 1 hour until the solid was completely dissolved. 120 μL of the prepared mixture was transferred and evenly coated onto a glass substrate. The coating was then spin-coated at 1500 rpm for 30 seconds and 3000 rpm for 3 seconds. After spin-coating, the film was immediately placed on a 160℃ heating plate for annealing for 20 minutes. After cooling to room temperature, the m-PEDOT:PSS film was placed on a spin coater, deionized water was added, and the film was exposed to air for 30 seconds. The water was then removed by spin-drying at 1500 rpm. After drying, the water-washed sugar alcohol-PEDOT:PSS film was obtained. The conductivity of the water-washed sugar alcohol-PEDOT:PSS film was 365 S / cm; the adhesion was 0.02 N / cm; and the tensile strength was 30%.

[0044] Example 2 reduced the addition of organic reagents and added a water washing process step compared to Example 1. After water washing, the conductivity of the sugar alcohol-PEDOT:PSS film was relatively improved, but the adhesion of the material was greatly reduced, to almost none. In addition, the tensile strength of the material was also greatly reduced. Therefore, it is necessary to introduce organic reagents to improve conductivity.

[0045] The electrical conductivity properties of flexible conductive polymer materials with different maltitol contents are as follows: Figure 1 As shown, the conductivity is improved after washing with water because the polyol sugar alcohol material containing two or more hydroxyl groups provided by this invention is an insulating material. The washing process removes these groups, thereby improving the conductivity of the prepared film. However, washing away the polyol sugar alcohol also results in the loss of other properties (including adhesion and tensile strength) of the sensor. Therefore, to solve this problem, existing technologies often introduce other formulations to compensate, such as introducing waterborne polyurethane to improve tensile strength.

[0046] Mechanical properties of polymer electrode materials with different maltitol contents, such as Figure 2 As shown, the overall performance of polymer electrodes varies considerably with changes in maltitol content.

[0047] Example 3

[0048] Transfer 1 mL of PH1000 dispersion (i.e., PEDOT:PSS aqueous solution with a solid content of 1.3 wt%, the same below) into a glass bottle, add a magnetic stir bar and stir at room temperature at 800 rpm. Weigh 111 mg of lactulose solid and slowly add it to the PH1000 dispersion, stir for 1 hour until the solid is completely dissolved, then add methanol to the solution to obtain a polymer blend solution and stop stirring. Transfer 120 μL of the prepared polymer blend solution dropwise onto a release paper substrate or glass substrate and let it stand for 6-12 hours to remove air bubbles, then bake at 40-65℃ for 3-5 hours to obtain a self-supporting film that can be directly used for wear.

[0049] Example 4

[0050] Transfer 1 mL of PH1000 dispersion (i.e., PEDOT:PSS aqueous solution with a solid content of 1.3 wt%, the same below) into a glass bottle, add a magnetic stir bar and stir at room temperature at 800 rpm. Weigh 111 mg of raffinose solid and slowly add it to the PH1000 dispersion, stirring for 1 hour until the solid is completely dissolved. Then add dimethyl sulfoxide to the solution to prepare a polymer blend solution and stop stirring. Transfer 120 μL of the prepared polymer blend solution dropwise onto a release paper substrate or glass substrate and let it stand for 6-12 hours to remove air bubbles. Then bake at 40-65℃ for 3-5 hours to obtain a self-supporting film that can be directly used for wear.

[0051] Example 5

[0052] The self-supporting films prepared in Examples 1, 3 or 4 are approximately 30-50 μm thick and simultaneously possess conductivity, adhesion, stretchability and low resistance variation characteristics.

[0053] The self-supporting films prepared in Examples 1, 3, or 4, when worn directly by the human body, undergo some deformation with human movement. However, within the tensile strength range of 20%-62% of the flexible conductive polymer described in this invention, the resistance remains almost unchanged. Figure 5 . Figure 5 The vertical axis represents the ratio of the resistance after stretching to the initial resistance, where R0 is the initial resistance. As can be seen from the figure, the resistance ratio does not change significantly within a break elongation range of approximately 20-60%. This indicates that the self-supporting film of this invention does not exhibit significant resistance changes with human deformation within the break elongation range of its material itself.

[0054] Example 6

[0055] Verification of the effects of different materials

[0056] Table 1 Adhesion of self-supporting films prepared from different materials

[0057]

[0058] Table 2 Tensile properties of self-supporting films prepared from different materials

[0059] Material 1% wt 5% wt 10% wt 13% wt 15% wt Maltitol 39％ 51％ 62％ 48％ 37％ Lactulose 20％ 28％ 37％ 49％ 40％ Raffinose 27％ 29％ 35％ 40％ 43％ Xylitol 18％ 24％ 28％ 30％ 33％ Mannitol 15％ 20％ 26％ 31％ 35％ Waterborne polyurethane 45％ 57％ 69％ 60％ 48％

[0060] Table 3 Conductivity of self-supporting thin films prepared from different materials

[0061] Material 1% wt 5% wt 10% wt 13% wt 15% wt Maltitol 0.8 32 37 28 22 Lactulose 0.5 18 27 33 32 Raffinose 0.6 19 25 35 34 Xylitol 0.4 20 28 30 33 Mannitol 0.6 24 25 33 36 Waterborne polyurethane 0.7 0.5 0.1 0.08 0.07

[0062] The conductivity values ​​in Table 3 are for self-supporting films made with only PEDOT:PSS dispersion and different sugar alcohol materials / waterborne polyurethane, without the addition of organic solvents.

[0063] Table 4 Conductivity with and without organic reagents

[0064] Materials / Proportions 1％ 5％ 10％ 13％ 15％ m-PEDOT: PSS 0.8 32 37 28 22 Organic reagents 20 90 111 50 25

[0065] Table 4 shows the conductivity of the self-supporting films prepared by adding the organic solvent ethylene glycol to the maltitol column in Table 3. As can be seen from Tables 3 and 4, organic reagents can significantly improve the conductivity of the self-supporting films. Furthermore, the conductivity of the final product is not positively correlated with the amount of polyol sugar alcohol material containing two or more hydroxyl groups provided by this invention; in fact, the conductivity of the product decreases when the amount of such polyol sugar alcohol added reaches a certain value.

[0066] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A self-supporting film of flexible conductive polymer for preparing a directly wearable sensor, characterized in that, The self-supporting film is made of a flexible conductive polymer and has a thickness of 30-50 μm. It can be directly adhered to the skin as a wearable health monitoring sensor. The flexible conductive polymer is prepared by blending a flexible conductive polymer material, a polyol sugar alcohol containing two or more hydroxyl groups, and a polar organic solvent; the flexible conductive polymer material is a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate dispersion; the polyol sugar alcohol containing two or more hydroxyl groups has a weight percentage of 10% in the flexible conductive polymer; the polar organic solvent has a weight percentage of 4%-5% in the flexible conductive polymer; the polyol sugar alcohol containing two or more hydroxyl groups is maltitol; the polar organic solvent includes ethylene glycol, methanol, or dimethyl sulfoxide.

2. The flexible conductive polymer of claim 1, wherein, The ratio of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate is 1:2.

5.

3. The flexible conductive polymer of claim 1, wherein, The blending method includes one or more of mechanical stirring, vortex stirring, and / or ultrasonic vibration.

4. The flexible conductive polymer of claim 1, wherein, The blending method includes the following steps: Step 1): Add a polyol sugar alcohol containing two or more hydroxyl groups to the poly(3,4-ethylenedioxythiophene):polystyrene sulfonate dispersion and stir until completely dissolved. The mass ratio of the two materials is 10:1 for poly(3,4-ethylenedioxythiophene):polystyrene sulfonate dispersion and polyol sugar alcohol. Step 2): Add a polar organic solvent to the solution obtained in Step 1) to prepare a polymer blend solution. The mass ratio of the three materials is 20:2:1 for poly(3,4-ethylenedioxythiophene):polystyrene sulfonate dispersion:polyol sugar alcohol:polar organic solvent. Step 3): The polymer blend solution obtained in Step 2) is dropped onto the release paper substrate or glass substrate and left to stand for 6-12 hours to remove air bubbles. Then, it is baked at 40-65℃ for 3-5 hours to obtain a self-supporting film that can be worn directly.

5. The flexible conductive polymer of claim 4, wherein, In the blending process, in steps 1) and 2), a polyol sugar alcohol containing two or more hydroxyl groups is added to the poly(3,4-ethylenedioxythiophene):polystyrene sulfonate dispersion and stirred at 800-1500 rpm for 0.5-2 hours. Then, a polar organic solvent is added and stirred at 800-1500 rpm for 10-30 minutes.

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