CN116655953A - Preparation method and application of hydrogel precursor liquid capable of being printed in 3D (three-dimensional) and high-conductivity high-elasticity hydrogel - Google Patents

Abstract

The invention belongs to the technical field of functional hydrogels, and provides a preparation method and application of a 3D printable hydrogel precursor liquid and a high-conductivity high-elasticity hydrogel. The preparation method of the hydrogel precursor liquid comprises the following steps: mixing polyvinyl alcohol solution, ethylene glycol aqueous solution, EDOT, acrylamide, initiator, N' -methylene bisacrylamide and tetramethyl ethylenediamine, and reacting to obtain the hydrogel precursor liquid capable of being printed in 3D. According to the invention, the gelation of the precursor solution is completed by introducing the water/glycol binary solvent and using a simple one-pot method, and then the hydrogel is prepared efficiently by freeze thawing cycle, and the prepared hydrogel combines the excellent properties of the conductive material and the hydrogel, so that the conductive material has stable mechanical properties and high conductivity, and the application range of the conductive material is widened.

Description

Preparation method and application of hydrogel precursor liquid capable of being printed in 3D (three-dimensional) and high-conductivity high-elasticity hydrogel

Technical Field

The invention relates to the technical field of functional hydrogels, in particular to a 3D printable hydrogel precursor liquid, a preparation method and application of a high-conductivity high-elasticity hydrogel.

Background

As artificial intelligence technology has tended to mature, flexible electronic devices have attracted extensive attention and research in artificial intelligence, electronic skin, human health monitoring, and human-computer interaction, among others. In flexible wearable electronic devices, sensors are an important component of them, which can convert external physical or environmental stimuli into detectable electrical signals. The flexible wearable sensor also has excellent flexibility, high sensitivity and quick sensing function, can be arranged on clothes, can be even directly attached to the skin surface of a human body, and can realize long-term monitoring functions on the aspects of human body movement, physiological activities and the like, such as joint bending, speaking, breathing, pulse, skin temperature and the like. The hydrogel has excellent flexibility, ion transport property and adjustable mechanical property, and has wide application prospect in the field of flexible electronics. In recent years, conductive hydrogel electronic materials designed by taking hydrogel as a matrix are rapidly developed, and the conductive hydrogel electronic materials have wide application prospects in the fields of flexible electronics such as electronic skin, flexible sensors, flexible supercapacitors and the like. Conductive hydrogels are an emerging class of hydrogels that combine hydrophilic matrices with conductive fillers, such as metal nanoparticles, conductive polymers or carbon-based materials, adding new properties to the hydrogel's nature, including flexibility, stretchability, conductive properties, etc. Among them, poly (3, 4-ethylenedioxythiophene) (PEDOT), a derivative of polythiophene, is an ideal candidate material for developing bioelectronic devices, and is attractive because of its high conductivity and good biocompatibility in the oxidized state, excellent conductivity, and excellent electrochemical stability. Therefore, the polymer hydrogel and the PEDOT material are compounded with each other, so that the mechanical property of the hydrogel can be improved, and the excellent conductivity of the hydrogel can be endowed. These properties make it one of the most potential candidates in flexible wearable electronic devices among the many new flexible materials that emerge in recent years.

However, the currently reported conductive hydrogels have the problems of poor mechanical properties, loss of conductivity due to freezing at low temperature, and the like, and the method and the performance of the prepared hydrogels are often unsatisfactory. For example, pengY et al successfully prepared a high strength freeze resistant moisture resistant hydrogel strain sensor by introducing PEDOT, PAA and glycerol into a PVA hydrogel network by in situ polymerization and two-step soaking. The obtained composite hydrogel has good conductivity (about 0.95S/m) and high mechanical strength (about 3.6 MPa). The gel still maintains flexibility and stretchability at low temperature, and has good response to multiple strains and subtle human body movements, and their studies indicate that EDOT can be uniformly dispersed in PVA solution, but the polymerization before and twice soaking results in complicated steps, and the soaking method can lead to the reduction of conductivity and mechanical properties (PengY, piM, zhangX, et al Highlength, antifreeze, andmoisturizing conductivehydrogelforhuman-motioning effect [ J)]Polymer,2020, 196:122369.). Sun et al prepared stretchable conductive hydrogels as conductive elements using physically cross-linked gelatin, chemically cross-linked PAM and PEDOT: PSS as raw materials by a double network method. The conductive element has an ultra-wide strain sensing range (0% -2850%), a short response time (200 ms) and excellent durability and repeatability (1200 cycles), and has a sensitivity of 1.58, and can effectively identify complex human body motions, and the research is that the conductive element is formed by a double network and a guide of a rigid network gelatin and a flexible network PAMThe presence of the double network gives the hydrogel very good tensile properties, but the presence of the PSS in the electrically conductive material PEDOT PSS weakens the conductive properties of PEDOT (H.Sun, Y.Zhao, C.Wang, et al ultra-stratchable, durable and conductive hydrogel with hybrid double network as high performance strain sensor and stretchable triboelectric nanogenerator [ J)]Nano Energy 2020, 76:105035-105047). Pengw et al by combining conductive ZnSO ₄ Doped into polyvinyl alcohol-polyacrylamide (PVA-PAM) double-network hydrogel, and then immersed into Ethylene Glycol (EG) and H ₂ And preparing the double-network organic hydrogel in the mixed solvent of O. The hydrogel has high conductivity (0.44S/m), excellent fatigue resistance and excellent moisture retention and excellent freezing resistance, but when the hydrogel is deformed by ionic liquid conduction, the risk of ion leakage is easily present (Peng W, han L, gao Y, et al. Flexible organohydrogel ionic skin with Ultra-Low temperature freezing resistance and Ultra-Durable moisture retention [ J)].Journal of Colloid and Interface Science,2022,608:396-404.)。

Therefore, how to efficiently prepare hydrogel materials having both stable mechanical properties and high electrical conductivity is a problem to be solved by those skilled in the art.

Disclosure of Invention

In view of the above, the invention provides a 3D printable hydrogel precursor solution, and a preparation method and application of a highly conductive and highly elastic hydrogel. The method aims at solving the technical problem that the hydrogel material with stable mechanical property and high conductivity can not be prepared efficiently in the prior art.

In order to achieve the above purpose, the invention adopts the following technical scheme:

the invention provides a preparation method of a 3D printable hydrogel precursor liquid, which comprises the following steps:

mixing polyvinyl alcohol solution, ethylene glycol aqueous solution, EDOT, acrylamide, initiator, N' -methylene bisacrylamide and tetramethyl ethylenediamine, and reacting to obtain the hydrogel precursor liquid capable of being printed in 3D.

Further, the volume ratio of the polyvinyl alcohol solution, the ethylene glycol aqueous solution and the tetramethyl ethylenediamine is 8-12 mL: 10-20 mL: 8-12 mu L;

the mass ratio of EDOT, acrylamide, initiator and N, N' -methylene bisacrylamide is 0.25-1.5 g: 4-5 g:0.9 to 3.4g: 0.001-0.01 g;

the mass volume ratio of the EDOT to the glycol aqueous solution is 0.25-1.5 g: 10-20 mL.

Further, the mass concentration of the PVA solution is 10-20%; the mass concentration of the glycol aqueous solution is 30-50%.

Further, the reaction temperature is 50-90 ℃, and the reaction time is 6-12 h.

Further, the initiator is ammonium persulfate and/or potassium persulfate.

The invention provides the 3D printable hydrogel precursor liquid prepared by the preparation method.

The invention also provides a method for preparing the high-conductivity high-elasticity hydrogel by using the 3D printable hydrogel precursor liquid, which comprises the following steps:

performing freeze thawing cycle on the hydrogel precursor liquid capable of being printed in 3D to obtain the high-conductivity high-elasticity hydrogel; the cycle times of the freeze thawing cycle are more than or equal to 3.

The invention provides the high-conductivity high-elasticity hydrogel prepared by the preparation method.

The invention also provides application of the high-conductivity high-elasticity hydrogel in an electrocardio electrode or a wearable device.

Compared with the prior art, the invention has the following beneficial effects:

(1) According to the invention, the anti-freezing double-network hydrogel is prepared through in-situ polymerization, so that the PEDOT is uniformly inserted into a PVA/PAM double-network system consisting of rigid PVA and flexible PAM, the tensile property and the conductivity of the hydrogel are improved, and the anti-freezing hydrogel material with high tensile rate and high conductivity is obtained, and can be applied to wearable equipment;

(2) According to the invention, the gelation of the precursor solution is completed by introducing a water/glycol binary solvent and using a simple one-pot method, and then the high-efficiency preparation of the hydrogel is realized by freeze thawing cycle;

(3) The 3D-printable hydrogel precursor liquid prepared by the invention has excellent fluidity, which is important for constructing a complex structure through 3D printing, and a simplified 3D-printable hydrogel sensor model is prepared on a flexible substrate, so that the hydrogel precursor liquid has the potential of detecting human body movement by application.

Drawings

FIG. 1 is a shape drawing of 3D printable hydrogel precursor fluid prepared in example 1, printed by 3D printing;

FIG. 2 is a graph showing the comparison of the conductivity of the highly conductive and highly elastic hydrogels prepared in examples 1 to 6;

FIG. 3 is a graph showing the tensile properties of the highly conductive and highly elastic hydrogels prepared in examples 1 to 6;

FIG. 4 is a stress-strain curve of the highly conductive and highly elastic hydrogel prepared in example 1, which was continuously compressed 20 times;

FIG. 5 is a DSC graph of the highly conductive and highly elastic hydrogel prepared in example 1;

FIG. 6 is a graph showing the effect of the highly conductive and highly elastic hydrogel prepared in example 1 in electrocardiographic electrodes;

FIG. 7 is a graph showing the effect of the highly conductive and highly elastic hydrogel prepared in example 1 on various motion amplitudes in a wearable sensor;

FIG. 8 is a device representation of the highly conductive and highly elastic hydrogel prepared in example 1 as an electrode for monitoring ECG signals and recorded ECG waveforms;

FIG. 9 is a graph showing the effect of the highly conductive and highly elastic hydrogel prepared in example 1 as a sensor for detecting the movement of muscles on the cheek;

FIG. 10 is a graph showing the effect of the highly conductive and highly elastic hydrogel prepared in example 1 as a sensor for detecting repeated eyebrow-tattooing movements;

FIG. 11 is a graph showing the effect of the highly conductive and highly elastic hydrogel prepared in example 1 as a sensor for detecting repeated eyebrow-tattooing movements;

FIG. 12 is a graph showing the effect of the highly conductive and highly elastic hydrogel prepared in example 1 as a sensor for detecting palmar fist making-developing movements;

FIG. 13 is a graph showing the effect of the highly conductive and highly elastic hydrogel prepared in example 1 as a sensor for detecting finger bending;

FIG. 14 is a graph showing the effect of the highly conductive and highly elastic hydrogel prepared in example 1 as a sensor for detecting arm bending;

FIG. 15 is a graph showing the effect of the highly conductive and highly elastic hydrogel prepared in example 1 as a sensor for detecting knee bending;

FIG. 16 is a graph showing the effect of the highly conductive and highly elastic hydrogel prepared in example 1 as a sensor for detecting bending of the wrist.

Detailed Description

The invention provides a preparation method of a 3D printable hydrogel precursor liquid, which comprises the following steps:

mixing polyvinyl alcohol solution, ethylene glycol aqueous solution, EDOT, acrylamide, initiator, N' -methylene bisacrylamide and tetramethyl ethylenediamine, and reacting to obtain the hydrogel precursor liquid capable of being printed in 3D.

In the present invention, polyvinyl alcohol (C ₂ H ₄ O) _n Is a water-soluble polymer material, has strong adhesiveness, good mechanical property and biocompatibility, and can form a three-dimensional network structure through self-crosslinking due to the existence of O atoms in hydroxyl (-OH) with strong polarity in a molecular chain; polyacrylamide (C) ₃ H ₅ NO) _n The linear organic high molecular polymer has a large number of amide groups on a molecular chain, can form associated hydrogen bonds with surrounding molecules, has active chemical properties, has a typical three-dimensional network structure, good adhesiveness and thickening property, no toxic or side effect and stable performance. The double-network gel can realize the complementary advantages of two materials, namely polyvinyl alcohol (PVA) and Polyacrylamide (PAM), reasonably allocate the two network proportions and combine with the solvent dosage, replace pure water solvent by using the mixed solvent of water and glycol, firmly fix water molecules in the hydrogel network by the strong hydrogen bond between water and glycol, and prevent water from being containedFreezing and volatilizing the seeds, preparing the hydrogel which overcomes stress concentration by the conductive substance in an in-situ polymerization mode, obtaining the basic performance, and realizing stable balance among various performances, thereby constructing a stable high-performance double-network hydrogel carrier transmission system. Double-crosslinked networks can provide more energy dissipation than single-network structured hydrogels.

PEDOT has the following characteristics: (1) The conductivity is high, and the doping can reach about 1000S/cm; (2) The solubility is good, and the solubility of the polythiophene is enhanced along with the increase of the substituted alkyl; (3) The chemical property is stable, and the chemical property is not easily influenced by environmental change under acidic or alkaline conditions; (4) can be used as an electrode material. The introduction of EDOT (3, 4-ethylenedioxythiophene) can enhance the mechanical properties of the hydrogel on one hand, and simultaneously, provide excellent conductivity for the hydrogel.

In the invention, the volume ratio of the polyvinyl alcohol solution, the ethylene glycol aqueous solution and the tetramethyl ethylenediamine is 8-12 mL: 10-20 mL:8 to 12. Mu.L, preferably 9 to 11mL: 14-17 mL:9 to 11. Mu.L, more preferably 10mL:15mL: 10. Mu.L;

the mass ratio of EDOT, acrylamide, initiator and N, N' -methylene bisacrylamide is 0.25-1.5 g: 4-5 g:0.9 to 3.4g:0.001 to 0.01g, preferably 0.5 to 1.25g:4.2 to 4.8g: 1.46-2.9 g:0.002 to 0.008g, more preferably 0.75 to 1.0g:4.4 to 4.6g: 1.94-2.43 g: 0.004-0.006 g;

the mass volume ratio of the EDOT to the glycol aqueous solution is 0.25-1.5 g:10 to 20mL, preferably 0.5 to 1.25g:14 to 17mL, more preferably 0.75 to 1.0g:15mL.

In the present invention, the mass concentration of the PVA solution is 10 to 20%, preferably 13 to 17%, and more preferably 14.27%; the mass concentration of the ethylene glycol aqueous solution is 30 to 50%, preferably 35 to 45%, and more preferably 40%.

In the present invention, the temperature of the reaction is 50 to 90 ℃, preferably 60 to 80 ℃, and more preferably 70 to 75 ℃; the reaction time is 6 to 12 hours, preferably 7 to 11 hours, and more preferably 8 to 10 hours.

In the present invention, the initiator is ammonium persulfate and/or potassium persulfate, preferably ammonium persulfate.

The invention provides the 3D printable hydrogel precursor liquid prepared by the preparation method.

The invention also provides a method for preparing the high-conductivity high-elasticity hydrogel by using the 3D printable hydrogel precursor liquid, which comprises the following steps:

performing freeze thawing cycle on the hydrogel precursor liquid capable of being printed in 3D to obtain the high-conductivity high-elasticity hydrogel; the cycle number of the freeze thawing cycle is not less than 3, preferably not less than 4, and further preferably not less than 5.

The invention provides the high-conductivity high-elasticity hydrogel prepared by the preparation method.

The invention also provides application of the high-conductivity high-elasticity hydrogel in an electrocardio electrode or a wearable device.

The technical solutions provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.

Example 1

PVA powder was dissolved in deionized water, magnetically stirred at 90℃for 3 hours until complete dissolution to give a polyvinyl alcohol solution having a mass concentration of 14.27%, and then the polyvinyl alcohol solution was cooled to room temperature. 10mL of a polyvinyl alcohol solution was added to 15mL of a 40% aqueous ethylene glycol solution, stirred for 10min and mixed uniformly, then 0.25g of EDOT, 4.9g of acrylamide, 0.98g of ammonium persulfate and 0.002g of N, N' -methylenebisacrylamide were further added, 10. Mu.L of tetramethyl ethylenediamine was added during the stirring and mixing process, and then reacted at 50℃for 6h to obtain a 3D printable hydrogel precursor liquid.

Fig. 1 is a shape diagram of 3D printable hydrogel precursor liquid prepared in this example, as can be obtained from fig. 1, by printing in a 3D printing manner, and the 3D printable hydrogel precursor liquid prepared in this invention has good flowability.

And (3) performing freeze thawing cycle on the 3D printable hydrogel precursor liquid for 5 times to obtain the high-conductivity high-elasticity hydrogel.

Example 2

The procedure of example 1 was the same except that EDOT was used in an amount of 0.5g and ammonium persulfate was used in an amount of 1.46g to prepare a highly conductive and highly elastic hydrogel.

Example 3

The procedure of example 1 was the same except that EDOT was used in an amount of 0.75g and ammonium persulfate was used in an amount of 1.94g to prepare a highly conductive and highly elastic hydrogel.

Example 4

The procedure of example 1 was the same except that EDOT was used in an amount of 1.0g and ammonium persulfate was used in an amount of 2.43g to prepare a highly conductive and highly elastic hydrogel.

Example 5

The procedure of example 1 was the same except that EDOT was used in an amount of 1.25g and ammonium persulfate was used in an amount of 2.90g to prepare a highly conductive and highly elastic hydrogel.

Example 6

The procedure of example 1 was the same except that EDOT was used in an amount of 1.5g and ammonium persulfate was used in an amount of 3.39g to prepare a highly conductive and highly elastic hydrogel.

FIG. 2 is a graph showing the comparison of the conductivity of the highly conductive and highly elastic hydrogels prepared in examples 1 to 6, and as shown in FIG. 2, the highly conductive and highly elastic hydrogels prepared in the present invention have high conductivity, up to 32.29S/m.

FIG. 3 is a graph showing the tensile properties of the highly conductive and highly elastic hydrogels prepared in examples 1 to 6, and it can be seen from FIG. 3 that the highly conductive and highly elastic hydrogels prepared in accordance with the present invention have excellent stretchability, up to 1050%.

Fig. 4 is a stress-strain curve chart of the highly conductive and highly elastic hydrogel prepared in example 1, which is continuously compressed 20 times, and as can be obtained from fig. 4, the highly conductive and highly elastic hydrogel prepared in the present invention has excellent stability.

FIG. 5 is a DSC graph of the highly conductive and highly elastic hydrogel prepared in example 1, as can be obtained from FIG. 5, the hydrogel prepared in the present invention can work in severe environments, and the freezing resistance can reach-42 ℃.

Fig. 6 is a graph showing the effect of the highly conductive and highly elastic hydrogel prepared in example 1 in the electrocardiograph electrode, and it can be known that the highly conductive and highly elastic hydrogel can well detect heart rate changes.

Fig. 7 is a graph showing the effect of the highly conductive and highly elastic hydrogel prepared in example 1 on the use of the wearable sensor with different motion amplitudes, and it can be known that the hydrogel has a good response, and can detect the motion of each part of the human body.

Fig. 8 is a device representation of the highly conductive and highly elastic hydrogel prepared in example 1 as an electrode monitoring ECG signal and recorded ECG waveform, wherein B is an electrocardiographic signal plot, C is a partial enlargement in the electrocardiographic test signal, and D is an electrocardiographic signal peak labeling plot. As can be seen from fig. 8, the hydrogel electrode can accurately reflect the beating of the heart when the human body is stationary. The existence of the P wave, the QRS wave group and the T wave can be clearly and continuously seen from the spectrogram, and the heartbeat waveform can be clearly and continuously output. The hydrogel used as an electrocardio sensor electrode has enough flexibility, can be attached to the skin in a seamless way and does not fall off, and can accurately reflect the beating condition of the heart of a human body.

The muscle movement caused by cheek doming is monitored by fixing both ends of the hydrogel-based sensor to the cheek of a person. When the wearable sensor is applied to the face of a volunteer, periodic bulge and relaxation of the face can be detected, with repeatable and stable signals (fig. 9). Periodic and repeatable resistance signals caused during alternating movements of normal and frowning can be collected by affixing a hydrogel-based sensor to the forehead (fig. 10 and 11). Our hydrogel sensor can not only monitor the delicate muscle movements described above, but also track bending movements produced by major joints (e.g., wrist, joint, elbow, and knee). For example, the resistance signal due to bending of the wrist (fig. 16) may be collected by fixing the hydrogel-based sensor to the palm surface to collect the resistance signal due to bending of the hand (fig. 12), and to the wrist. Furthermore, by attaching the hydrogel-based sensor to the right index finger, the resistance response caused during the bend-release cycle of the index finger from a bend angle of 30 ° to 90 ° (fig. 13) was collected. Similar elbow and knee motion bend angle detection is tracked by affixing hydrogel-based sensors to the respective joints (bending and stretching to varying degrees) (fig. 14). The reproducibility of the resistance signal at a specific joint bending angle demonstrates a good working stability of the hydrogel-based sensor. As the bending angle becomes larger, the resistance output increases, which is attributed to the increase in the deformed length of the hydrogel. The recognition of the joint movement angle is helpful for realizing the remote real-time operation of the robot movement, and the prospect of the hydrogel-based sensor in the aspects of artificial intelligence and man-machine interaction is demonstrated. Human motion status can be monitored by immobilizing the hydrogel-based on a laptop sensor as in fig. 15. These results indicate that the locomotor activity can be converted into a real-time resistance signal by the hydrogel sensor prepared according to the invention, which helps to achieve locomotor monitoring.

The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims (9)

1. A method for preparing a 3D printable hydrogel precursor fluid, comprising the steps of:

mixing polyvinyl alcohol solution, ethylene glycol aqueous solution, EDOT, acrylamide, initiator, N' -methylene bisacrylamide and tetramethyl ethylenediamine, and reacting to obtain the hydrogel precursor liquid capable of being printed in 3D.

2. The preparation method according to claim 1, wherein the volume ratio of the polyvinyl alcohol solution, the ethylene glycol aqueous solution and the tetramethyl ethylenediamine is 8-12 mL: 10-20 mL: 8-12 mu L;

the mass ratio of EDOT, acrylamide, initiator and N, N' -methylene bisacrylamide is 0.25-1.5 g: 4-5 g:0.9 to 3.4g: 0.001-0.01 g;

the mass volume ratio of the EDOT to the glycol aqueous solution is 0.25-1.5 g: 10-20 mL.

3. The method according to claim 2, wherein the mass concentration of the PVA solution is 10 to 20%; the mass concentration of the glycol aqueous solution is 30-50%.

4. A process according to claim 2 or 3, wherein the reaction is carried out at a temperature of 50 to 90 ℃ for a period of 6 to 12 hours.

5. The method according to claim 4, wherein the initiator is ammonium persulfate and/or potassium persulfate.

6. A 3D printable hydrogel precursor fluid prepared by the method of any one of claims 1 to 5.

7. A method for preparing a highly conductive and highly elastic hydrogel using the 3D printable hydrogel precursor fluid of claim 6, comprising the steps of:

performing freeze thawing cycle on the hydrogel precursor liquid capable of being printed in 3D to obtain the high-conductivity high-elasticity hydrogel; the cycle times of the freeze thawing cycle are more than or equal to 3.

8. The highly conductive and highly elastic hydrogel prepared by the preparation method of claim 7.

9. Use of the highly conductive and highly elastic hydrogel of claim 8 in an electrocardio electrode or a wearable device.