KR20210128971A - Thermally healable and reshapable conductive hydrogel composite - Google Patents

Abstract

Provided is a new electroconductive hydrogel composite material which can be used as an artificial skin candidate that satisfies all four requirements, such as flexibility, electroconductivity, healing properties, and biocompatibility, required for artificial skin. The electroconductive hydrogel composite material according to an aspect of the present disclosure comprises: a hydrogen-bondable hydrogel including water and a cross-linkable polymer which is cross-linked by hydrogen bonding; and an electroconductive material dispersed in the hydrogen-bondable hydrogel.

Description

Thermally healable and reshapable conductive hydrogel composite

The present disclosure relates to artificial skin or electronic skin. The present disclosure also relates to conductive hydrogels.

The skin of the living body has the ability to sense external stimuli, the ability to heal wounds repeatedly, and the flexibility to adapt to the movement of the muscles. Research for obtaining artificial skin that mimics such biological skin is being conducted in various aspects.

As a condition required for artificial skin, the following four characteristics can be considered. First, in terms of mechanical properties, "flexibility" is required to adapt to motion. Flexibility can be measured by Young's modulus. Second, in terms of functionality, "electrical conductivity" required to transmit an electrical signal generated by an external stimulus is required. Third, “healing properties” are required. Healing properties mean that multiple damage-healing cycles can be repeated. Fourth, in terms of biological properties, "biocompatibility" is required. Biocompatibility means that the material of the artificial skin is bio-friendly.

One example of a conventional artificial skin includes a flexible substrate and an electronic device (eg, capacitor or transistor) embedded thereon [“Nature Mater. (2010), 9, 859, Stanford]”; "Nature Mater. (2010), 9, 821, Berkeley"; and "Nature Nanotech. (2011), 6, 788, Stanford"]. However, in this case, the requirements in terms of mechanical properties and functionality are satisfied, but the requirements in terms of healing properties and biological properties are not satisfied.

Another example of conventional artificial skin is a hydrogel or synthetic polymer with healing properties ["Science (2002), 295, 1698, UCLA &USC"; "PNAS (2012), 109, 4383, UCSD"; and "Nature Comm (2011), 2, 1, Osaka"]. However, in this case, the requirements in terms of healing properties and biological properties are satisfied, but the requirements in terms of mechanical properties and functionality are not satisfied.

Another example of conventional artificial skin is a material capable of restoring electrical properties by self-healing a damaged area ["Nature Nanotech (2012), Online, Stanford"; and "Adv. Mater. (2012), 24, 2578"]. However, in this case, the requirements in terms of mechanical properties, functionality and healing properties are satisfied, but the requirements in terms of biological properties are not satisfied.

Another example of conventional artificial skin is that obtained by embedding various sensors directly into living skin ["PNAS (2011), Harvard"; and "Science (2011), 333, 830, UIUC"]. However, in this case, the requirements in terms of mechanical properties and functionality are satisfied, but the requirements in terms of healing properties and biological properties are not satisfied.

As such, conventional artificial skin candidates satisfy only one or two of the four requirements for artificial skin.

In the present disclosure, a new artificial skin candidate that can be used as a candidate for artificial skin that satisfies all four requirements required for artificial skin, namely, "flexibility", "electrical conductivity", "healing property" and "biocompatibility" An electrically conductive hydrogel composite material is provided.

An embodiment of the electrically conductive hydrogel composite material according to an aspect of the present disclosure is,

Hydrogen-bonding hydrogel comprising water and a cross-linkable polymer cross-linked by hydrogen bonding; and

and an electrically conductive material dispersed in the hydrogen-bonding hydrogel.

An embodiment of the method for manufacturing an electrically conductive hydrogel composite material according to another aspect of the present disclosure includes cooling a heated dispersion comprising a crosslinkable polymer crosslinked by hydrogen bonding, water, and an electrically conductive material.

An embodiment of the method for manufacturing an electrically conductive hydrogel composite material according to another aspect of the present disclosure is,

Hydrogen-bonding hydrogel comprising water and a cross-linkable polymer cross-linked by hydrogen bonding; and an electrically conductive polymer dispersed in the hydrogen-bonding hydrogel; as a method for producing an electrically conductive hydrogel composite material comprising:

crosslinkable polymers crosslinked by hydrogen bonding; water; a monomer for forming an electrically conductive polymer; and cooling the heated reaction mixture comprising; and an oxidizing agent.

Embodiments of the electrically conductive hydrogel composite material provided in the present disclosure meet the four requirements required for artificial skin, namely, "flexibility", "electric conductivity", "healing properties" and "biocompatibility". all can be satisfied.

1 is a scanning electron microscope of the lyophilized (a) agarose hydrogel of Comparative Example 1, (b) the electrically conductive hydrogel composite material of Example 2, and (c) the electrically conductive hydrogel composite material of Example 1 It's a photo.
2 is (a) a scanning electron microscope photograph and (b) EDX nitrogen mapping photograph of the electrically conductive hydrogel composite material of Example 2.
3 is a photograph obtained from (a) a scanning electron micrograph and (b) EDX nitrogen mapping (N mapping from an energy dispersive X-ray analysis) for the electrically conductive hydrogel composite material of Example 1.
4 is a graph showing the electrical conductivity of the electrically conductive hydrogel composite materials of Examples 1 to 8 and the agarose hydrogels of Comparative Examples 1 and 2;
5 is a photograph showing the experimental process performed to confirm the thermal healing properties (thermal healing property) of the electrically conductive hydrogel composite material of Example 1.
6 is a graph showing the Young's modulus of elasticity of the electrically conductive hydrogel composite material of Examples 1 to 4 and the agarose hydrogel of Comparative Example 1.
7 is a graph showing the breaking stress measured through a uniaxial tensile test for the electrically conductive hydrogel composite material of Examples 1 to 4 and the agarose hydrogel of Comparative Example 1. FIG.
8 is a photograph showing an experimental process for confirming the electrical conductivity after stretching for the electrically conductive hydrogel composite material of Example 1.
9 shows the results of patterning the electroconductive hydrogel composite material of Example 1 by a screen printing method.
Figure 10 shows the result of producing a figure in the form of a freestanding (freestanding) form by the molding method of the electroconductive hydrogel composite material of Example 1.
11, using the electrically conductive hydrogel composite material of Example 1, shows the result of manufacturing a fiber by a wet spinning method.

Hereinafter, an embodiment of the electrically conductive hydrogel composite material according to an aspect of the present disclosure will be described in more detail. An embodiment of the electrically conductive hydrogel composite material according to an aspect of the present disclosure includes a hydrogen-bonding hydrogel comprising a cross-linkable polymer cross-linked by hydrogen bonding and water; and an electrically conductive material dispersed in the hydrogen-bonding hydrogel.

Generally, hydrogels are formed from a mixture of water and a crosslinkable polymer. When the crosslinkable polymer in the mixture of water and the crosslinkable polymer forms a crosslinked network, the mixture of water and the crosslinkable polymer is gelled to form a hydrogel. The hydrogel used in the present disclosure is a hydrogel (referred to simply as a 'hydrogen bond-based hydrogel') formed from a crosslinkable polymer crosslinked by hydrogen bonding.

Crosslinking by hydrogen bonding is reversible. When the hydrogen-bonding hydrogel is heated, the hydrogen bonds between the polymers are broken, thereby dissolving the cross-linked network, thereby forming a liquid (eg, colloid, sol, or aqueous solution) having flowability. Upon cooling of this flowable liquid, hydrogen bonds between the polymers are re-formed, thereby restoring the cross-linked network, thereby forming a non-flowable hydrogel.

Due to the reversibility of crosslinking by hydrogen bonding, the hydrogel composite material of the present disclosure may have “healing properties”. That is, the hydrogel composite material of the present disclosure is thermally healable. Specifically, when the hydrogel composite material of the present disclosure with defects is heated, the cross-linked network of the hydrogel composite material of the present disclosure is dismantled, so the hydrogel composite material of the present disclosure has fluidity. Due to this fluidity, the defects of the hydrogel composite material of the present disclosure are filled. Then, when the hydrogel composite material of the present disclosure is cooled again, it recovers to a defect-free hydrogel composite material.

The crosslinkable polymer crosslinked by hydrogen bonding may be, for example, agarose.

A hydrogen-bonding hydrogel formed from a cross-linkable polymer cross-linked by such hydrogen bonding may have “flexibility” similar to that of living skin. In addition, the hydrogen-bonding hydrogel formed from a cross-linkable polymer cross-linked by such hydrogen bonding is a bio-based material or a non-toxic material, and thus has “biocompatibility”.

In the hydrogen-bonding hydrogel, the content of water may be, for example, about 0.5 parts by weight to about 5.0 parts by weight based on 100 parts by weight of the cross-linkable polymer crosslinked by hydrogen bonding. If the content of water in the hydrogen-bonding hydrogel is too high, the viscosity of the hydrogen-bonding hydrogel solution becomes too low, so that the hydrogen-bonding density of the hydrogen-bonding hydrogel is low, and accordingly, the hydrogen-bonding hydrogel may not be formed. have. If the content of water in the hydrogen-bonding hydrogel is too low, the viscosity of the hydrogen-bonding hydrogel solution becomes too high, and the hydrogen-bonding density of the hydrogen-bonding hydrogel is high, and accordingly, the hydrogen-bonding hydrogel may not dissolve. .

The electrically conductive material is dispersed in the hydrogen-bonding hydrogel. The electrically conductive material forms an electrically conductive network within the hydrogen-bonding hydrogel. Accordingly, the hydrogel composite material of the present disclosure has “electrical conductivity”.

The electrically conductive material may be, for example, a metal particle, a conductive carbon material, a conductive polymer, or a combination thereof.

The metal particles may be, for example, Au, Ag, Pt, Ti, Fe, or a combination thereof. These metal particles are harmless to the human body.

The conductive carbon material may be, for example, carbon black, carbon nanotubes, graphene, or a combination thereof.

The conductive polymer is, for example, polypyrroles, poly(3,4-ethylenedioxythiophenes), poly(styrene sulfonates), PEDOT : PSS (poly(3,4-ethylenedioxythiophenes) poly(styrenesulfonates)), polyanilines, or a combination thereof.

For example, the electrically conductive material may exist in the form of particles in the hydrogen-bonding hydrogel. The electrically conductive material may have, for example, an average particle size of about 100 nm to about 1 μm.

The amount of the electrically conductive material dispersed in the hydrogen-bonding hydrogel may be, for example, from about 10 parts by weight to about 300 parts by weight based on 100 parts by weight of the cross-linkable polymer crosslinked by hydrogen bonding. If the amount of the electrically conductive material is too small, the hydrogel may not be conductive. If the amount of the electrically conductive material is too large, the hydrogel may lose its gel properties.

Due to the electrically conductive material dispersed in the hydrogen bonding hydrogel, the hydrogel composite material of the present disclosure has electrical conductivity. The electrical conductivity of the hydrogel composite material of the present disclosure, for example, when measured by a four-point probe method under standard conditions (20 ℃, 1 atm), about 1.0 × 10 ^-6 S / cm to about 0.2 S / cm can be

In another embodiment of the electrically conductive hydrogel composite, the water in the hydrogen bonding hydrogel may further include an electrolyte. When the water in the hydrogen-bonding hydrogel further contains an electrolyte, the electrolyte causes a synergistic action with the electrically conductive material dispersed in the hydrogen-bonding hydrogel (i.e., electron / hole current by the conductive polymer and The ionic current caused by the electrolyte is combined to cause a synergistic action), and the electrical conductivity of the hydrogel composite material can be further improved.

Embodiments of the electroconductive hydrogel composite material in which the water in the hydrogen-bonding hydrogel further contains an electrolyte, in the embodiments of the electroconductive hydrogel composite material in which the water in the hydrogen-bonding hydrogel does not contain an electrolyte In comparison, it may have a higher electrical conductivity by about 0.22 S/cm to about 0.69 S/cm.

The electrolyte may be, for example, NaCl, KCl, Na ₂ HPO ₄ , KH ₂ PO ₄ , Na ₂ SO ₄ , Li ₂ SO ₄ , MgSO ₄ , a Buffer (eg, PBS or Tris-HCl), or a combination thereof. The content of the electrolyte may be, for example, about 0.1 parts by weight to about 5.0 parts by weight based on 100 parts by weight of water in the hydrogen-bonding hydrogel. As a specific example, the water in the hydrogen-bonding hydrogel may be PBS (phosphate-buffered saline). PBS can be, for example, a mixture of _{NaCl, KCl, Na 2} HPO ₄ , KH ₂ PO _{4 and water.} The PBS may be, for example, 10x PBS or 1x PBS. The composition of 1 liter of 10x PBS may be, for example, 80 g of NaCl, 2 g of KCl, 14.4 g of Na ₂ HPO ₄ , 2.4 g of KH ₂ PO ₄ and the balance of water. The composition of 1 liter of 1x PBS may be, for example, 8 g of NaCl, 0.2 g of KCl, 1.44 g of Na ₂ HPO ₄ , 0.24 g of KH ₂ PO ₄ and the balance of water.

In another embodiment of the electrically conductive hydrogel composite material, the electrically conductive material is polypyrrole, and the content of polypyrrole is about 300 parts by weight or less, based on 100 parts by weight of a crosslinkable polymer crosslinked by hydrogen bonding. When the content of polypyrrole is higher than this, the number of repeated thermal healing of the electrically conductive hydrogel composite material is sharply reduced. When the content of polypyrrole is about 10 parts by weight or less based on 100 parts by weight of the crosslinkable polymer crosslinked by hydrogen bonding, even after repeating the thermal healing of the electrically conductive hydrogel composite material at least about 10 times, the electrically conductive hydrogel The gel composite can be cooled to form a gel again. However, when the content of polypyrrole is greater than about 50 parts by weight based on 100 parts by weight of the crosslinkable polymer crosslinked by hydrogen bonding, after repeating the thermal healing of the electrically conductive hydrogel composite material at most 4 times, The electrically conductive hydrogel composite no longer forms a gel when cooled. This is presumed to be because, when the content of polypyrrole exceeds a certain level, the hydrogen bonding site of the crosslinkable polymer crosslinked by hydrogen bonding is blocked by polypyrrole.

An embodiment of the method for manufacturing an electrically conductive hydrogel composite material according to another aspect of the present disclosure includes cooling a heated dispersion comprising a crosslinkable polymer crosslinked by hydrogen bonding, water, and an electrically conductive material.

The water may further include an electrolyte.

The heating temperature of the dispersion may be, for example, about 110 °C to about 150 °C. If the heating temperature of the dispersion is too low, the hydrogel may not melt into a liquid state. If the heating temperature of the dispersion is too high, the water may boil without the hydrogel being dissolved.

The cooling temperature of the dispersion may be, for example, about 25° C. or less. The cooling temperature of the dispersion may be higher or lower than this, as long as the hydrogel does not melt.

An embodiment of the method for manufacturing an electrically conductive hydrogel composite material according to another aspect of the present disclosure is,

Hydrogen-bonding hydrogel comprising water and a cross-linkable polymer cross-linked by hydrogen bonding; and an electrically conductive polymer dispersed in the hydrogen-bonding hydrogel; as a method for producing an electrically conductive hydrogel composite material comprising:

crosslinkable polymers crosslinked by hydrogen bonding; water; a monomer for forming an electrically conductive polymer; and cooling the heated reaction mixture comprising; and an oxidizing agent.

The water may further include an electrolyte.

The monomer for forming an electrically conductive polymer is, for example, a monomer for forming polypyrroles, a monomer for forming poly(3,4-ethylenedioxythiophenes), and poly(styrenesulfonate). ) (poly(styrene sulfonates)) forming monomer, PEDOT:PSS (poly(3,4-ethylenedioxythiophenes) poly(styrenesulfonates)) forming monomer, or polyaniline (polyanilines) forming monomer. The monomer for forming the electrically conductive polymer may be, for example, pyrrole, 3,4-ethylenedioxythiophene, styrenesulfonate, aniline, derivatives thereof, or a combination thereof.

The oxidizing agent serves to induce the mixture of the crosslinkable polymer crosslinked by hydrogen bonding and water and the monomer for forming the electrically conductive polymer to be well mixed. A mixture of a crosslinkable polymer crosslinked by hydrogen bonding and water and a monomer for forming an electrically conductive polymer do not mix well. On the other hand, the oxidizing agent is well mixed with a mixture of water and a crosslinkable polymer that is crosslinked by hydrogen bonding. In addition, the oxidizing agent has affinity with the monomer for forming an electrically conductive polymer. Therefore, in the presence of the oxidizing agent, the monomer for forming the electrically conductive polymer can be uniformly dispersed in the reaction mixture. Accordingly, even after the reaction mixture is cooled to form a gel, the monomer for forming an electrically conductive polymer can still be evenly dispersed in the reaction mixture gel.

As the oxidizing agent, for example, FeCl ₃ , CuCl ₂ , K ₂ S ₂ O ₈ , or a combination thereof may be used.

The amount of the oxidizing agent in the reaction mixture may be, for example, about 50 parts by weight to about 1500 parts by weight based on 100 parts by weight of the crosslinkable polymer crosslinked by hydrogen bonding. If the amount of the oxidizing agent is too small, the conductive polymer may not be sufficiently formed. If the amount of the oxidizing agent is too large, the excess oxidizing agent is reduced at a high temperature, which may interfere with the reversible gellation of the hydrogel.

The heating temperature of the reaction mixture may be, for example, about 20 °C to about 40 °C. If the heating temperature of the reaction mixture is too low, there is no particular problem, but the conductive polymer formation rate may be too slow. If the heating temperature of the reaction mixture is too high, the reaction mixture (oxidizing agent) itself may be reduced and may not participate in the reaction for generating a conductive polymer.

The cooling temperature of the reaction mixture may be, for example, about 20 °C to about 25 °C. If the cooling temperature of the reaction mixture is too low, gelation of the hydrogel is too fast, and it may be difficult to evenly disperse the conductive polymer in the hydrogel. If the cooling temperature of the reaction mixture is too high, gelation of the hydrogel may not proceed.

When the reaction mixture is cooled, the reaction mixture gel is formed as the crosslinkable polymer crosslinked by hydrogen bonding forms a crosslinking network. The monomer for forming an electrically conductive polymer dispersed in the reaction mixture gel is gradually polymerized to form an electrically conductive polymer. Accordingly, over time, the electrical conductivity of the reaction mixture gel gradually increases. After a certain period of time, the reaction mixture gel is converted into an electrically conductive hydrogel composite having the desired electrical conductivity. The time it takes for the polymerization of the monomer for forming an electrically conductive polymer dispersed in the reaction mixture gel to be completed may be, for example, about 30 minutes to about 2 weeks.

<Example>

Example 1 --- Polypyrrole 0.45 M, deionized water

0.1 g of agarose and 1.52 g of _{FeCl 3} were dissolved in 5 g of deionized water at 50° C. contained in a 20 ml beaker. To this, 0.3 g of a pyrrole monomer was added and stirred to obtain a reaction mixture. Then, the reaction mixture at 50 °C in the beaker was cooled to 25 °C to form a reaction mixture gel. Then, the reaction mixture gel was left at 25° C. for 30 minutes, so that the pyrrole monomer was polymerized to form polypyrrole, thereby preparing the electrically conductive hydrogel composite material of Example 1. By inverting the beaker, it was confirmed that the prepared electroconductive hydrogel composite material did not fall from the bottom of the beaker.

Example 2 --- Polypyrrole 0.15 M, deionized water

0.1 g of agarose and 0.51 g of _{FeCl 3} were dissolved in 5 g of deionized water at 50° C. contained in a 20 ml beaker. To this, 0.1 g of a pyrrole monomer was added and stirred to obtain a reaction mixture. Then, the reaction mixture at 50 °C in the beaker was cooled to 25 °C to form a reaction mixture gel. Then, the reaction mixture gel was left at 25° C. for 120 minutes to allow the pyrrole monomer to polymerize to form polypyrrole, thereby preparing an electrically conductive hydrogel composite material of Example 2. By inverting the beaker, it was confirmed that the prepared electroconductive hydrogel composite material did not fall from the bottom of the beaker.

Example 3 --- polypyrrole 0.074 M, deionized water

In 5 g of deionized water at 50 °C contained in a 20 ml beaker, 0.1 g of agarose and 0.25 g of _{FeCl 3 were dissolved.} To this, 0.05 g of a pyrrole monomer was added and stirred to obtain a reaction mixture. Then, the reaction mixture at 50 °C in the beaker was cooled to 25 °C to form a reaction mixture gel. Then, the reaction mixture gel was left at 25° C. for 300 minutes to allow the pyrrole monomer to polymerize to form polypyrrole, thereby preparing an electrically conductive hydrogel composite material of Example 3. By inverting the beaker, it was confirmed that the prepared electroconductive hydrogel composite material did not fall from the bottom of the beaker.

Example 4 --- Polypyrrole 0.01, deionized water

0.1 g of agarose and 0.10 g of _{FeCl 3} were dissolved in 5 g of deionized water at 50° C. contained in a 20 ml beaker. To this, 0.02 g of a pyrrole monomer was added and stirred to obtain a reaction mixture. Then, the reaction mixture at 50 °C in the beaker was cooled to 25 °C to form a reaction mixture gel. Then, the reaction mixture gel was left at 25° C. for 140 minutes to allow the pyrrole monomer to polymerize to form polypyrrole, thereby preparing an electrically conductive hydrogel composite material of Example 4. By inverting the beaker, it was confirmed that the prepared electroconductive hydrogel composite material did not fall from the bottom of the beaker.

Comparative Example 1 --- Polypyrrole 0.00 M, deionized water

Agarose solution was obtained by dissolving 0.1 g of agarose in 5 g of deionized water at 50° C. contained in a beaker with a capacity of 20 ml. Then, the 50 ℃ agarose aqueous solution in the beaker was cooled to 25 ℃, to form the agarose hydrogel of Comparative Example 1. By inverting the beaker, it was confirmed that the non-conductive agarose hydrogel did not fall from the bottom of the beaker.

Example 5 --- Polypyrrole 0.45 M, 10x PBS

First, 10x PBS was prepared. The composition of 1 liter of 10x PBS was 80 g NaCl, 2 g KCl, 14.4 g Na ₂ HPO ₄ , 2.4 g KH ₂ PO ₄ and the balance deionized water. The pH of 10x PBS was 7.4. In 5 g of 10x PBS at 50 °C contained in a 20 ml beaker, 0.1 g of agarose and 1.52 g of _{FeCl 3 were dissolved.} To this, 0.3 g of a pyrrole monomer was added and stirred to obtain a reaction mixture. Then, the reaction mixture at 50 °C in the beaker was cooled to 25 °C to form a reaction mixture gel. Then, the reaction mixture gel was left at 25° C. for 30 minutes to allow the pyrrole monomer to polymerize to form polypyrrole, thereby preparing an electrically conductive hydrogel composite material of Example 5. By inverting the beaker, it was confirmed that the prepared electroconductive hydrogel composite material did not fall from the bottom of the beaker.

Example 6 --- Polypyrrole 0.15 M, 10x PBS

0.1 g of agarose and 0.51 g of _{FeCl 3} were dissolved in 5 g of 10x PBS at 50° C. contained in a 20 ml beaker. To this, 0.1 g of a pyrrole monomer was added and stirred to obtain a reaction mixture. Then, the reaction mixture at 50 °C in the beaker was cooled to 25 °C to form a reaction mixture gel. Then, the reaction mixture gel was left at 25° C. for 120 minutes to allow the pyrrole monomer to polymerize to form polypyrrole, thereby preparing an electrically conductive hydrogel composite material of Example 6. By inverting the beaker, it was confirmed that the prepared electroconductive hydrogel composite material did not fall from the bottom of the beaker.

Example 7 --- Polypyrrole 0.074 M, 10x PBS

In 5 g of 10x PBS at 50 °C contained in a 20 ml beaker, 0.1 g of agarose and 0.25 g of _{FeCl 3 were dissolved.} To this, 0.05 g of a pyrrole monomer was added and stirred to obtain a reaction mixture. Then, the reaction mixture at 50 °C in the beaker was cooled to 25 °C to form a reaction mixture gel. Then, the reaction mixture gel was left at 25° C. for 300 minutes to allow the pyrrole monomer to polymerize to form polypyrrole, thereby preparing an electrically conductive hydrogel composite material of Example 7. By inverting the beaker, it was confirmed that the prepared electroconductive hydrogel composite material did not fall from the bottom of the beaker.

Example 8 --- Polypyrrole 0.03 M, 10x PBS

In 5 g of 10x PBS at 50 °C contained in a 20 ml beaker, 0.1 g of agarose and 0.10 g of _{FeCl 3 were dissolved.} To this, 0.02 g of a pyrrole monomer was added and stirred to obtain a reaction mixture. Then, the reaction mixture at 50 °C in the beaker was cooled to 25 °C to form a reaction mixture gel. Then, the reaction mixture gel was left at 25° C. for 140 minutes to allow the pyrrole monomer to polymerize to form polypyrrole, thereby preparing an electrically conductive hydrogel composite material of Example 8. By inverting the beaker, it was confirmed that the prepared electroconductive hydrogel composite material did not fall from the bottom of the beaker.

Comparative Example 2 --- Polypyrrole 0.00 M, 10x PBS

Agarose solution was obtained by dissolving 0.1 g of agarose in 5 g of 10x PBS at 50° C. contained in a 20 ml beaker. Then, the 50 ℃ agarose aqueous solution in the beaker was cooled to 25 ℃, to form the agarose hydrogel of Comparative Example 2. By inverting the beaker, it was confirmed that the non-conductive agarose hydrogel did not fall from the bottom of the beaker.

<Evaluation result>

morphology

The agarose hydrogel of Comparative Example 1 (polypyrrole content 0), the electrically conductive hydrogel composite material of Example 2 (polypyrrole content 0.15 M) and the electrically conductive hydrogel composite material of Example 1 (polypyrrole content 0.45 M) were prepared under vacuum. Freeze-dried. Scanning electron microscope analysis was performed on these lyophilized samples.

1 is a scanning electron microscope of the lyophilized (a) agarose hydrogel of Comparative Example 1, (b) the electrically conductive hydrogel composite material of Example 2, and (c) the electrically conductive hydrogel composite material of Example 1 It's a photo. Figure 1 (a) shows only the agarose polymer structure. 1 (b) and (c), polypyrrole particles are shown together with the agarose polymer structure. 2 is (a) a scanning electron microscope photograph and (b) EDX nitrogen mapping photograph of the electrically conductive hydrogel composite material of Example 2. The white dots in (b) of FIG. 2 indicate the position of the nitrogen atom of polypyrrole. It can be seen from (b) of FIG. 2 that polypyrrole is well dispersed. 3 is a photograph obtained from (a) scanning electron micrograph and (b) EDX nitrogen mapping (N mapping from an energy dispersive X-ray analysis) for the electroconductive hydrogel composite material of Example 1. The white dots in (b) of FIG. 3 indicate the position of the nitrogen atom of polypyrrole. It can be seen from (b) of FIG. 3 that polypyrrole is well dispersed.

As can be seen from FIGS. 1 to 3, as the content of polypyrrole increased, the shape of the agarose polymer nanostructure changed from a soft ear shape to a hard pine cone shape. In addition, as the content of polypyrrole increased, the distribution of polypyrrole in the electrically conductive hydrogel composite material became wider.

electrical conductivity

For the electrically conductive hydrogel composite materials of Examples 1 to 8 and the agarose hydrogels of Comparative Examples 1 and 2, using a four-point probe method, under standard conditions (25 ° C., 1 atm), electrical conductivity was measured. . 4 is a graph showing the electrical conductivity of the electrically conductive hydrogel composite materials of Examples 1 to 8 and the agarose hydrogels of Comparative Examples 1 and 2; As shown in FIG. 4 , as the content of polypyrrole in the hydrogel increased, many pathways for electrical conduction were formed inside the hydrogel, and the electrical conductivity of the hydrogel was increased up to 0.2 S/cm. When the electrolyte was added to the water in the hydrogel, not only the electron conduction effect by polypyrrole but also the ion transfer effect by the electrolyte occurred, and the electric conductivity of the hydrogel was further improved. As shown in FIG. 4 , the electrical conductivity of the hydrogel using 10x PBS containing the electrolyte was further increased by 0.2 to 0.7 S/cm, compared to the electrical conductivity of the hydrogel using deionized water.

healing properties

5 is a photograph showing the experimental process performed to confirm the thermal healing properties (thermal healing property) of the electrically conductive hydrogel composite material of Example 1. By heating the cleaved hydrogel composite material to 120 ℃, the cleaved hydrogel composite material was changed to a sol state. The split hydrogel composite material changed to a sol state and adhered while flowing. Then, the hydrogel composite material changed to a sol state was cooled to 25 °C, and gelled again. As confirmed by the lighting of the LED, the re-gelled high-hydrogel composite material continued to maintain electrical conductivity. This shows that when the electrically conductive hydrogel composite material of the present disclosure is damaged, it can be healed by heat.

Change in healing recovery limit according to polypyrrole content

For the electroconductive hydrogel composite materials of Examples 9 to 11 prepared in the same manner as in Example 1 except for the polypyrrole content, the 120 ° C heating and 25 ° C cooling processes were repeated 10 times. The results are summarized in Table 1.

number of repetitions Example 11
Polypyrrole content:
0.015M Example 10
Polypyrrole content:
0.045M Example 9
Polypyrrole content:
0.075M 1 time gelled again. gelled again. gelled again. Episode 2 gelled again. gelled again. gelled again. 3rd time gelled again. gelled again. gelled again. 4 times gelled again. gelled again. It did not gel again. 5 times gelled again. It did not gel again. It did not gel again. 6 episodes gelled again. It did not gel again. It did not gel again. Episode 7 gelled again. It did not gel again. It did not gel again. Episode 8 gelled again. It did not gel again. It did not gel again. Episode 9 gelled again. It did not gel again. It did not gel again. 10 episodes gelled again. It did not gel again. It did not gel again.

As shown in Table 1, when the content of polypyrrole is increased to a certain level or more, the number of thermal healing of the electrically conductive hydrogel composite material can be rapidly limited. For example, when the polypyrrole content is 15 mM, the electroconductive hydrogel composite material does not gel again until the 120 ° C heating and 25 ° C cooling process is repeated 10 times. However, when the polypyrrole content was 45 mM, after repeating the 120 ℃ heating and 25 ℃ cooling process 4 times, the electroconductive hydrogel composite material did not gel again occurred.

flexibility

For the electrically conductive hydrogel composite materials of Examples 1 to 4 and the agarose hydrogel of Comparative Example 1, Young's modulus of elasticity was measured through a uniaxial tensile test. The results are shown in FIG. 6 . 6 is a graph showing the Young's modulus of the electrically conductive hydrogel composite material of Examples 1 to 4 and the agarose hydrogel of Comparative Example 1. As the content of polypyrrole increased, the Young's modulus increased from 27 kPa to 46 kPa. Human skin has a Young's modulus of about 400 kPa to about 800 kPa. Therefore, it can be seen that the electrically conductive hydrogel composite materials of Examples 1 to 4 can have a flexibility similar to that of human skin.

breakage strain

For the electrically conductive hydrogel composite material of Examples 1 to 4 and the agarose hydrogel of Comparative Example 1, the breaking stress was measured through a uniaxial tensile test. The results are shown in FIG. 7 . As shown in FIG. 7 , if the polypyrrole content is too high, the electrically conductive hydrogel composite material may be broken even by a very low tensile rate.

Electrical conductivity after stretching

8 is a photograph showing an experimental process for confirming the electrical conductivity after stretching for the electrically conductive hydrogel composite material of Example 1. That is, the hydrogel composite material was applied to the finger joint, and the electrical resistance of the stretched hydrogel composite material was measured while bending the finger joint. Since agarose is a biocompatible material, the electrically conductive hydrogel composite material of Example 1 is harmless to the skin and can be applied to the skin. As shown in FIG. 8 , electricity was passed even when the knuckles were bent. Compared to the electrical resistance (41 kohm) of the unstretched hydrogel composite in the state of stretching the finger joint, the electrical resistance (282 kohm) of the stretched hydrogel composite in the bent state of the finger joint increased by about 6.5 times. . Although this is the case, the electrically conductive hydrogel composite material of Example 1 still exhibited electrical conductivity even after stretching.

machinability

The electrically conductive hydrogel composite material of the present disclosure changes into a sol state when heated and has fluidity, and loses fluidity as it gels again when cooled. Therefore, the electrically conductive hydrogel composite material of the present disclosure can be molded by various methods. 9 shows the results of patterning the electroconductive hydrogel composite material of Example 1 by a screen printing method. Figure 10 shows the result of producing a figure in the form of a freestanding (freestanding) form by the molding method of the electrically conductive hydrogel composite material of Example 1. 11, using the electrically conductive hydrogel composite material of Example 1, shows the result of manufacturing a fiber by a wet spinning method.

Claims (11)

Hydrogen-bonding hydrogel comprising water and a cross-linkable polymer cross-linked by hydrogen bonding; and an electrically conductive material dispersed in the hydrogen-bonding hydrogel; as an electrically conductive hydrogel composite material comprising:
The electrically conductive hydrogel composite material is a thermally healable skin,
The electrically conductive material is polypyrrole, and the content of the polypyrrole is 10 parts by weight to 50 parts by weight or less, based on 100 parts by weight of the crosslinkable polymer crosslinked by hydrogen bonding.
Electrically conductive hydrogel composites. The electrically conductive hydrogel composite material according to claim 1, wherein the crosslinkable polymer crosslinked by hydrogen bonding is agarose. According to claim 1, wherein in the hydrogen-bonding hydrogel, the content of water, based on 100 parts by weight of the cross-linkable polymer crosslinked by hydrogen bonding, electrical conductivity, characterized in that 0.5 parts by weight to 5.0 parts by weight hydrogel composites. The electrically conductive hydrogel composite material according to claim 1, wherein the water in the hydrogen-bonding hydrogel further comprises an electrolyte. 5. The method of claim 4, wherein the electrolyte is NaCl, KCl, Na ₂ HPO ₄ , KH ₂ PO ₄ , Na ₂ SO ₄ , Li ₂ SO ₄ , MgSO ₄ , PBS buffer, Tris-HCl buffer, or a combination thereof. Electrically conductive hydrogel composite material, characterized in that. The electrically conductive hydrogel composite material according to claim 4, wherein the content of the electrolyte is 0.1 parts by weight to 5.0 parts by weight, based on 100 parts by weight of water in the hydrogen-bonding hydrogel. The electrically conductive hydrogel composite material according to claim 4, wherein the water in the hydrogen-bonding hydrogel is phosphate-buffered saline (PBS). An electrically conductive hydrogel composite material manufacturing method comprising the step of cooling a heated dispersion comprising a crosslinkable polymer crosslinked by hydrogen bonding, water and an electrically conductive material,
The electrically conductive hydrogel composite material is a thermally healable skin,
The electrically conductive material is polypyrrole, and the content of the polypyrrole is 10 parts by weight to 50 parts by weight or less, based on 100 parts by weight of the crosslinkable polymer crosslinked by hydrogen bonding.
Method for manufacturing an electrically conductive hydrogel composite material. Hydrogen-bonding hydrogel comprising water and a cross-linkable polymer cross-linked by hydrogen bonding; and an electrically conductive polymer dispersed in the hydrogen-bonding hydrogel; as a method for producing an electrically conductive hydrogel composite material comprising:
crosslinkable polymers crosslinked by hydrogen bonding; water; a monomer for forming an electrically conductive polymer; and cooling the heated reaction mixture comprising; and
An electrically conductive hydrogel composite material manufacturing method comprising:
The electrically conductive hydrogel composite material is a thermally healable skin,
The electrically conductive material is polypyrrole, and the content of the polypyrrole is 10 parts by weight to 50 parts by weight or less, based on 100 parts by weight of the crosslinkable polymer crosslinked by hydrogen bonding.
Method for manufacturing an electrically conductive hydrogel composite material. The method according to claim 9, wherein the oxidizing agent is FeCl ₃ , CuCl ₂ , K ₂ S ₂ O ₈ , or a combination thereof. 10. The method of claim 9, wherein the amount of the oxidizing agent in the reaction mixture, based on 100 parts by weight of the crosslinkable polymer crosslinked by hydrogen bonding, an electrically conductive hydrogel composite material preparation, characterized in that 50 parts by weight to 1500 parts by weight Way.

Images