Long-acting moisturizing strain-insensitive flexible conductive hydrogel and preparation method thereof
By introducing materials such as lithium bromide aqueous solution and polyacrylamide into the hydrogel to form a humidity-adaptive three-dimensional network, combined with conductive additives, the problem of resistance change during stretching of water-based flexible conductive materials is solved, achieving long-lasting moisture retention and strain-insensitive flexible conductive properties, which are suitable for flexible electronic products.
Patent Information
- Application Number
- CN202511144075.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-15
- Publication Date
- 2025-10-31
AI Technical Summary
Traditional water-based flexible conductive materials suffer from a decline in mechanical and electrical properties due to moisture evaporation in the external environment, and their resistance changes significantly during stretching, failing to meet the conductive connection and signal transmission requirements of flexible electronic products.
A humidity-adaptive three-dimensional network structure was formed using lithium bromide aqueous solution, polyacrylamide, and methacryloyloxypropyltrimethoxysilane. Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) and multi-walled carbon nanotubes were combined as conductive additives to form a strain-insensitive conductive network through covalent bonds and dynamic ionic interactions.
It achieves long-lasting moisture retention, maintains mechanical and electrical properties, avoids performance degradation caused by moisture evaporation, and maintains stable resistance during stretching, making it suitable for conductive connections and signal transmission in flexible electronic products.
Smart Images
Figure CN120865574A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of hydrogel technology, and more specifically to a long-lasting moisturizing strain-insensitive flexible conductive hydrogel and its preparation method. Background Technology
[0002] With the rapid development of flexible consumer electronics and medical electronic devices (such as foldable phones and wearable medical testing devices), traditional metallic conductive media are limited in their ability to handle electrical connections and signal transmission requiring stretchability. Therefore, there is an urgent need to develop stretchable flexible conductive materials. Hydrogel-based flexible conductive materials have been widely researched and applied in recent years due to their excellent mechanical properties, plasticity, and high ionic conductivity.
[0003] However, water-based materials have inherent drawbacks in practical applications. When exposed to external environments, their mechanical and electrical properties inevitably decline or even fail due to water evaporation. Furthermore, three-dimensional networks constructed through polymer crosslinking exhibit increased resistance during stretching due to the increased spacing between conductive additives caused by network extension. This phenomenon is commonly used in strain sensors, but when used for conductive connections and signal transmission in flexible circuits, the primary requirement is to avoid significant resistance changes with stretching. Summary of the Invention
[0004] The purpose of this invention is to provide a long-lasting moisturizing strain-insensitive flexible conductive hydrogel and its preparation method, providing a method for preparing a flexible conductive hydrogel with long-lasting moisturizing effect and strain insensitivity.
[0005] The objective of this invention is achieved through the following technical solution:
[0006] A long-lasting moisturizing strain-insensitive flexible conductive hydrogel includes a hydrogel matrix and conductive additives. The hydrogel matrix uses lithium bromide aqueous solution as solvent, polyacrylamide as hydrogel matrix, and methacryloyloxypropyltrimethoxysilane as crosslinking agent to form a collapsible three-dimensional network structure with humidity adaptive properties through covalent bond / dynamic ion interaction and hydration.
[0007] The conductive additives are poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) and multi-walled carbon nanotubes that can form a strain-resistant permeable conductive network; thus, a long-lasting, strain-insensitive, flexible conductive hydrogel with good moisturizing properties is prepared.
[0008] A method for preparing a long-lasting, strain-insensitive, flexible conductive hydrogel, comprising the following steps:
[0009] Step S1: Lithium bromide aqueous solution and acrylamide monomer are stirred and mixed. The conductive additive is added to the obtained solution and stirred and mixed. The mixture is then ultrasonically dispersed in an ice bath to obtain the precursor solution.
[0010] Step S2: Add crosslinking agent and pH adjuster to the precursor solution in sequence and stir;
[0011] Step S3: Prepare a long-lasting, strain-insensitive, flexible, conductive hydrogel by using a heating initiation system and a photoinitiation system;
[0012] The heating initiation system is as follows: crosslinking agent and pH adjuster are added to the precursor liquid in sequence and stirred. Then, over-initiator and accelerator are added in sequence. The prepared solution is injected into a mold and heated at 65°C for 1 hour to obtain a long-lasting moisturizing strain-insensitive flexible conductive hydrogel.
[0013] The photoinitiator system is prepared as follows: crosslinking agent and pH adjuster are added sequentially to the precursor solution and stirred. Then, an ethanol saturated solution of photoinitiator (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (i819) is added. The prepared solution is injected into a mold and polymerization is completed under ultraviolet light irradiation to obtain a long-lasting moisturizing strain-insensitive flexible conductive hydrogel.
[0014] The lithium bromide aqueous solution contains 55 wt.% lithium bromide, and the solvent in which the lithium bromide aqueous solution and acrylamide monomer are mixed contains 2 mol / L acrylamide.
[0015] The conductive additives are poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) and multi-walled carbon nanotubes, which can form a strain-resistant permeation conductive network. The contents of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) and multi-walled carbon nanotubes are 1.5% (w / v) and 2 mg / mL, respectively.
[0016] The crosslinking agent is a solution of methacryloyloxypropyltrimethoxysilane, and the pH adjuster is an aqueous solution of sodium hydroxide. The amount of methacryloyloxypropyltrimethoxysilane solution used in each 1 ml of precursor solution is 4 μL, 10% (w / w); and the amount of sodium hydroxide aqueous solution used is 15 μL, 10% (w / v).
[0017] The initiator is an aqueous solution of ammonium persulfate, and the accelerator is an aqueous solution of sodium metabisulfite; 8 μL of ammonium persulfate aqueous solution, 10% (w / v); 0-4 μL of sodium metabisulfite aqueous solution, 10% (w / v);
[0018] The initiator includes any one or a combination of two or more of ammonium persulfate, potassium persulfate, or sodium persulfate;
[0019] The amount of ethanol-saturated solution of photoinitiator (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (i819) in each 1 ml of precursor solution is 10 μL, and curing is completed by irradiation under 365 nm ultraviolet light for 30 minutes.
[0020] The beneficial effects of this invention are as follows:
[0021] By leveraging the synergistic effect of hydrogel matrix and conductive additives, a long-lasting, strain-insensitive flexible conductive hydrogel was developed. This hydrogel can maintain its mechanical and electrical properties for an extended period, overcoming the long-term performance issues caused by water evaporation when used as a conductive connection in flexible electronic devices. Attached Figure Description
[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific implementation methods.
[0023] Figure 1 This is a schematic diagram of the stress-strain curve of the long-lasting moisturizing strain-insensitive flexible conductive hydrogel of the present invention.
[0024] Figure 2 This is a schematic diagram of the IV characteristic curve of the long-lasting moisturizing strain-insensitive flexible conductive hydrogel of the present invention.
[0025] Figure 3 This is a schematic diagram showing the mass change over time of the long-lasting moisturizing strain-insensitive flexible conductive hydrogel of the present invention.
[0026] Figure 4 This is a schematic diagram of the strain coefficient of the strain-insensitive flexible conductive hydrogel with long-lasting moisturizing properties according to the present invention. Detailed Implementation
[0027] The present invention will now be described in further detail with reference to the accompanying drawings.
[0028] like Figures 1 to 4 As shown below, the formulation and function of a long-lasting moisturizing strain-insensitive flexible conductive hydrogel are described in detail.
[0029] A long-lasting moisturizing strain-insensitive flexible conductive hydrogel includes a hydrogel matrix and conductive additives. The hydrogel matrix uses lithium bromide aqueous solution as solvent, polyacrylamide as hydrogel matrix, and methacryloyloxypropyltrimethoxysilane as crosslinking agent to form a collapsible three-dimensional network structure with humidity adaptive properties through covalent bond / dynamic ion interaction and hydration.
[0030] The conductive additives are poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) and multi-walled carbon nanotubes that can form a strain-resistant permeable conductive network; thus, a long-lasting, strain-insensitive, flexible conductive hydrogel with good moisturizing properties is prepared.
[0031] When a 55 wt.% lithium bromide solution is used as a hydrogel solvent, its hydration reduces the rate of water evaporation while spontaneously exchanging moisture and maintaining humidity balance through the difference in humidity between its own content and the external environment. After copolymerization of methacryloyloxypropyltrimethoxysilane and acrylamide monomer, their hydrolysis products form a rigid network and dynamic ionic bonds through covalent condensation. Simultaneously, the polar carbonyl groups of acrylamide form ion-dipole interactions with lithium ions. This combination of a rigid network and a dual dynamic network effectively dissipates strain energy, achieving the stretchability of the hydrogel. Furthermore, the strong hydration of lithium bromide during polymerization causes water molecule aggregation, leading to the collapse of the polymer network. This collapsed structure ensures that the conductive additives do not separate due to network extension during the stretching of the conductive hydrogel, thus preventing a decrease in conductivity. In addition, lithium ions provide ionic conductivity pathways, further enhancing the conductivity of the conductive hydrogel. In summary, the synergistic effect between materials achieves a flexible conductive hydrogel with long-lasting moisturizing properties and strain insensitivity.
[0032] like Figures 1 to 4 As shown below, the steps and functions of a method for preparing a long-lasting moisturizing strain-insensitive flexible conductive hydrogel will be described in detail.
[0033] Example 1:
[0034] A method for preparing a long-lasting, strain-insensitive, flexible conductive hydrogel, comprising the following steps:
[0035] Step S1: Lithium bromide aqueous solution and acrylamide monomer are stirred and mixed. The conductive additive is added to the obtained solution and stirred and mixed. The mixture is then ultrasonically dispersed in an ice bath to obtain the precursor solution.
[0036] Step S2: After adding crosslinking agent and pH adjuster to the precursor solution and stirring, add initiator and accelerator in sequence;
[0037] Step S3: The prepared solution is injected into a mold and heated to obtain a long-lasting, strain-insensitive, flexible, conductive hydrogel with good moisturizing properties.
[0038] A 55 wt.% lithium bromide aqueous solution was mixed with acrylamide monomer to obtain a solution with an acrylamide monomer content of 2 mol / L.
[0039] The conductive additive poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) and multi-walled carbon nanotubes were sequentially added to the solution prepared above, with contents of 1.5% (w / v) and 2 mg / mL, respectively, to prepare the precursor solution.
[0040] In each 1 mL of precursor solution, the volumes of methacryloxypropyltrimethoxysilane and 10% (w / w) sodium hydroxide aqueous solution are 4 μL and 15 μL, respectively. After vortexing (1500 rpm) for 1 minute, ensure that methacryloxypropyltrimethoxysilane is fully hydrolyzed and deprotonated in an alkaline environment.
[0041] 8 μL of 10% (w / v) ammonium persulfate aqueous solution and 4 μL of sodium metabisulfite aqueous solution were added sequentially to the solution prepared above. After vortexing (1500 rpm) for 5 s, the solution was injected into a mold and placed in a heating box and heated at 65°C for 1 hour to obtain an ultra-long-lasting moisturizing strain-insensitive flexible conductive hydrogel.
[0042] The concentration range of sodium metabisulfite aqueous solution is adjusted within 0-4 μ and 10% (w / v). The concentration and amount of sodium metabisulfite aqueous solution determine the curing speed of the ultra-long-lasting moisturizing strain-insensitive flexible conductive hydrogel.
[0043] Furthermore, the initiator includes any one or a combination of two or more of ammonium persulfate, potassium persulfate, and sodium persulfate.
[0044] Example 2:
[0045] A method for preparing a long-lasting, strain-insensitive, flexible conductive hydrogel, comprising the following steps:
[0046] Step S1: Lithium bromide aqueous solution and acrylamide monomer are stirred and mixed. The conductive additive is added to the obtained solution and stirred and mixed. The mixture is then ultrasonically dispersed in an ice bath to obtain the precursor solution.
[0047] Step S2: After adding crosslinking agent and pH adjuster to the precursor solution and stirring, add an ethanol saturated solution containing photoinitiator (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (i819);
[0048] Step S3: The prepared solution is injected into a mold and polymerized under ultraviolet light to obtain a long-lasting, strain-insensitive, flexible, conductive hydrogel with good moisturizing properties.
[0049] A 55 wt.% lithium bromide aqueous solution was mixed with acrylamide monomer to obtain a solution with an acrylamide monomer content of 2 mol / L.
[0050] The conductive additive poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) and multi-walled carbon nanotubes were sequentially added to the solution prepared above, with contents of 1.5% (w / v) and 2 mg / mL, respectively, to prepare the precursor solution.
[0051] In each 1 mL of precursor solution, the volumes of methacryloxypropyltrimethoxysilane and 10% (w / w) sodium hydroxide aqueous solution are 4 μL and 15 μL, respectively. After vortexing (1500 rpm) for 1 minute, ensure that methacryloxypropyltrimethoxysilane is fully hydrolyzed and deprotonated in an alkaline environment.
[0052] A 10 μL saturated ethanol solution containing photoinitiator (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (i819) was prepared. After vortex stirring (1500 rpm) for 10 s, the prepared solution was injected into a mold and cured by irradiation under 365 nm ultraviolet light for 30 minutes to obtain a long-lasting moisturizing strain-insensitive flexible conductive hydrogel.
[0053] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be considered as excluding other embodiments. It can be used in various other combinations, modifications, and substitutions, and is within the scope of the concept described herein. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.
Claims
1. A long-lasting, strain-insensitive, flexible conductive hydrogel, comprising a hydrogel matrix and conductive additives, characterized in that: The hydrogel matrix is a collapsible three-dimensional network structure with humidity adaptive properties, formed by covalent bond / dynamic ion interaction and hydration, using lithium bromide aqueous solution as solvent, polyacrylamide as hydrogel matrix, and methacryloyloxypropyltrimethoxysilane as crosslinking agent. The conductive additives are poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) and multi-walled carbon nanotubes that can form a strain-resistant permeable conductive network; thus, a long-lasting, strain-insensitive, flexible conductive hydrogel with good moisturizing properties is prepared.
2. A method for preparing a long-lasting, strain-insensitive, flexible conductive hydrogel, characterized in that: The method includes the following steps: Step S1: Lithium bromide aqueous solution and acrylamide monomer are stirred and mixed. The conductive additive is added to the obtained solution and stirred and mixed. The mixture is then ultrasonically dispersed in an ice bath to obtain the precursor solution. Step S2: Add crosslinking agent and pH adjuster to the precursor solution in sequence and stir; Step S3: Prepare a long-lasting, strain-insensitive, flexible conductive hydrogel by using a heating initiation system and a photoinitiation system.
3. The method for preparing a long-lasting moisturizing strain-insensitive flexible conductive hydrogel according to claim 2, characterized in that: The heating initiation system is as follows: crosslinking agent and pH adjuster are added sequentially to the precursor solution and stirred, then over-initiator and accelerator are added sequentially. The prepared solution is injected into a mold and heated at 65°C for 1 hour to obtain a long-lasting moisturizing strain-insensitive flexible conductive hydrogel.
4. The method for preparing a long-lasting moisturizing strain-insensitive flexible conductive hydrogel according to claim 2, characterized in that: The photoinitiator system is prepared as follows: a crosslinking agent and a pH adjuster are added sequentially to the precursor solution and stirred. Then, an ethanol-saturated solution of photoinitiator (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (i819) is added. The prepared solution is injected into a mold and polymerization is completed under ultraviolet light irradiation to obtain a long-lasting moisturizing strain-insensitive flexible conductive hydrogel.
5. The method for preparing a long-lasting moisturizing strain-insensitive flexible conductive hydrogel according to claim 2, characterized in that: The lithium bromide aqueous solution contains 55 wt.% lithium bromide, and the solvent in which the lithium bromide aqueous solution and acrylamide monomer are mixed contains 2 mol / L acrylamide.
6. The method for preparing a long-lasting moisturizing strain-insensitive flexible conductive hydrogel according to claim 2, characterized in that: The conductive additives are poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) and multi-walled carbon nanotubes, which can form a strain-resistant permeable conductive network. The contents of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) and multi-walled carbon nanotubes are 1.5% (w / v) and 2 mg / mL, respectively.
7. A method for preparing a long-lasting, strain-insensitive, flexible conductive hydrogel according to claim 3 or 4, characterized in that: The crosslinking agent is a solution of methacryloyloxypropyltrimethoxysilane, and the pH adjuster is an aqueous solution of sodium hydroxide. The amount of methacryloyloxypropyltrimethoxysilane solution used in each 1 ml of precursor solution is 4 μL, 10% (w / w); and the amount of sodium hydroxide aqueous solution used is 15 μL, 10% (w / v).
8. The method for preparing a long-lasting moisturizing strain-insensitive flexible conductive hydrogel according to claim 3, characterized in that: The initiator is an aqueous solution of ammonium persulfate, and the accelerator is an aqueous solution of sodium metabisulfite; 8 μL of ammonium persulfate aqueous solution, 10% (w / v); 0-4 μL of sodium metabisulfite aqueous solution, 10% (w / v).
9. The method for preparing a long-lasting moisturizing strain-insensitive flexible conductive hydrogel according to claim 3, characterized in that: The initiator includes any one or a combination of two or more of ammonium persulfate, potassium persulfate, or sodium persulfate.
10. The method for preparing a long-lasting moisturizing strain-insensitive flexible conductive hydrogel according to claim 4, characterized in that: The amount of ethanol-saturated solution of photoinitiator (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (i819) in each 1 ml of precursor solution is 10 μL, and curing is completed by irradiation under 365 nm ultraviolet light for 30 minutes.