A method for preparing a hydrogel sensing material with both self-powered and self-healing properties

Abstract

This invention proposes a method for preparing a hydrogel sensing material with both self-powered and self-healing properties. The key to this method is the electrostatic mixing of thermoelectrically active poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) and polyethyleneimine-crosslinked cellulose nanocrystals to prepare a CNC-PEDOT:PSS composite. This composite is then further compounded with a polyvinyl alcohol / borax system to obtain a self-powered and self-healing CNC-PEDOT:PSS / PVA hydrogel. The hydrogel sensing material prepared by this method combines excellent properties such as tensile strength, plasticity, self-healing, and self-powered operation, showing broad application prospects in self-powered wearable electronic devices and personal health monitoring.

Description

Technical Field

[0001] This invention relates to a method for preparing hydrogels, and particularly to a method for preparing self-powered and self-healing hydrogel sensing materials, belonging to the field of polymer materials. Background Technology

[0002] Over the past decade, flexible strain sensors have attracted significant attention from researchers in wearable electronics and electronic skin fields due to their ability to convert invisible external stimuli into recordable electrical signals through different sensing modes. Thanks to their excellent biocompatibility, stretchability, and flexibility, self-healing hydrogel-based flexible sensing materials have been widely applied in medical and health monitoring, soft robotics, human-computer interaction, and electronic skin.

[0003] Currently, most hydrogel-based flexible sensing materials use various polymers with poor mechanical properties as a substrate, making them unable to sense temperature and requiring an external power source for signal sensing in practical applications. Cong Huang et al.'s article, "Ultra-stretchable and self-healable hydrogel driven by sorbitol for flexible strain sensors with anti-freezing and self-adhesive," published in the *European Polymer Journal* (2022, 111240), introduces the preparation of a multifunctional PCS hydrogel and its application in flexible wearable devices for motion monitoring and voice recognition. However, this hydrogel cannot sense human body temperature and requires an external power source during use, hindering its development in fields such as electronic skin and flexible wearable devices.

[0004] Therefore, this invention uses polyvinyl alcohol / borax as the basic framework of the hydrogel. A CNC-PEDOT:PSS composite is prepared by electrostatically mixing thermoelectrically active poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) and polyethyleneimine-crosslinked cellulose nanocrystals. This composite is then further compounded with the polyvinyl alcohol / borax system. The prepared CNC-PEDOT:PSS / PVA conductive hydrogel exhibits excellent tensile strength, plasticity, self-healing properties, and self-powering characteristics. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing hydrogel sensing materials that have both self-powered and self-healing properties. This method is simple to operate, green, environmentally friendly, safe, and convenient for industrial production.

[0006] This invention uses polyvinyl alcohol / borax as the basic framework of the hydrogel. By combining cellulose nanocrystals (CNC) with the conductive polymer poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) and then doping them into the polyvinyl alcohol / borax system, a hydrogel sensing material with self-powered and self-healing properties is prepared.

[0007] A method for preparing a hydrogel sensing material with both self-powered and self-healing properties, the specific steps of which are as follows:

[0008] 1) Add an appropriate amount of γ-glycidoxypropyltrimethoxysilane (GPTMS) to a certain mass fraction of CNC suspension, stir at room temperature for a period of time to obtain a mixture;

[0009] 2) Add a suitable concentration of polyethyleneimine solution to the mixture obtained in step 1), stir at room temperature for a period of time to obtain CNC-PEI mixture;

[0010] 3) Add a few drops of acetic acid to the CNC-PEI mixture obtained in step 2) until it is adjusted to a weakly acidic state;

[0011] 4) Add an appropriate amount of PEDOT:PSS solution to the CNC-PEI mixture obtained in step 3), stir at room temperature for a suitable time until uniformly dispersed, and obtain the CNC-PEDOT:PSS complex.

[0012] 5) Take an appropriate amount of the CNC-PEDOT:PSS complex obtained in step 4), centrifuge until its supernatant is neutral, add deionized water to an appropriate amount, and stir at room temperature for an appropriate time until it is uniformly dispersed.

[0013] 6) Add an appropriate amount of polyvinyl alcohol to the product obtained in step 5), place it in a water bath, heat and stir at low speed for a period of time to obtain CNC-PEDOT:PSS / PVA mixture.

[0014] 7) Slowly add an appropriate concentration of borax aqueous solution to the CNC-PEDOT:PSS / PVA mixture obtained in step 6), and let it stand at room temperature for a period of time to obtain CNC-PEDOT:PSS / PVA hydrogel.

[0015] In step 1), the appropriate amount of GPTMS is 0.10–0.40 g; the CNC suspension has a certain mass fraction of 2.00 wt%; and the time period is 2–3 h.

[0016] The appropriate concentration of the polyethyleneimine solution in step 2) is 20.00%, the amount is 0.5-2g, and the time period is 3-4h.

[0017] The appropriate amount of PEDOT:PSS solution in step 4) is 3.33–13.32 g; the appropriate time is 48–72 h.

[0018] In step 5), the appropriate amount of CNC-PEDOT:PSS complex is 1 / 8 to 1 / 2; deionized water is added to an appropriate amount of 30.00 to 150.00 mL; and the appropriate time is 5 min.

[0019] The appropriate amount in step 6) is 4.5 to 22.5g, the temperature of the water bath is 90 to 95℃, and the time period is 3 to 5 hours.

[0020] The appropriate concentration of the borax aqueous solution in step 7) is 0.10–0.15 g / mL; and the standing time is 24–48 h.

[0021] The morphology of the CNC-PEDOT:PSS / PVA hydrogel obtained in this invention was observed using field emission scanning electron microscopy (FE-SEM); its self-powered capability was tested using a digital multimeter; it was cut into two parts using a blade and then placed together to test its self-healing ability; the results are as follows:

[0022] (1) Field emission scanning electron microscopy (FE-SEM) tests showed that the CNC-PEDOT:PSS / PVA hydrogel has a microporous structure inside. (See Appendix) Figure 1 .

[0023] (2) Digital multimeter testing showed that CNC-PEDOT:PSS / PVA hydrogel has good self-powered performance. (See Appendix) Figure 2 .

[0024] (3) CNC-PEDOT: PSS / PVA hydrogel has excellent self-healing properties, see Appendix Figure 3 .

[0025] The hydrogel sensing material prepared by this invention has excellent self-healing and self-powering capabilities, and has broad application prospects in electronic skin.

[0026] The beneficial effects of this invention are:

[0027] This invention utilizes in-situ polymerization of conductive polymer PEDOT:PSS to reinforce a polyvinyl alcohol / borax hydrogel system on a CNC machine to prepare a CNC-PEDOT:PSS / PVA hydrogel with self-powered and self-healing properties. The preparation process is green and pollution-free, and the resulting product is non-toxic and harmless, with good biocompatibility and mechanical properties. Attached Figure Description

[0028] Figure 1Field emission scanning electron microscopy (FE-SEM) image of the CNC-PEDOT:PSS / PVA hydrogel prepared in Example 1.

[0029] Figure 2 The graph shows the self-powered capability test of the CNC-PEDOT:PSS / PVA hydrogel prepared in Example 1 at a temperature difference of 55K.

[0030] Figure 3 The image shows the self-healing ability test results of the CNC-PEDOT:PSS / PVA hydrogel prepared in Example 1.

[0031] Specific experimental cases

[0032] The present invention will be further illustrated below with specific examples. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0033] Example 1

[0034] 0.20 g of γ-glycidoxypropyltrimethoxysilane (GPTMS) was added to a 2.00 wt% CNC suspension and stirred at room temperature for 2 h. Then, 1.00 g of 20.00% PEI aqueous solution was added dropwise and stirring was continued for 3 h. A few drops of acetic acid were added to adjust the pH to weakly acidic. 6.66 g of PEDOT:PSS solution was added and stirred at room temperature for 48 h to obtain the CNC-PEDOT:PSS complex. One-quarter of the above CNC-PEDOT:PSS complex was taken and deionized water was added to 30.00 mL and stirred for 5 min to disperse it evenly. Then, 4.50 g of PVA was added and stirred slowly at 90 °C for 3 h. The mixture was poured into a rectangular mold and placed in an ultrasonic cleaner at 0 °C. 0.15 g / mL of borax aqueous solution was slowly added dropwise. The mixture was allowed to stand at room temperature for 48 h to obtain the CNC-PEDOT:PSS / PVA hydrogel.

[0035] Example 2

[0036] 0.10 g of γ-glycidoxypropyltrimethoxysilane (GPTMS) was added to a 2.00 wt% CNC suspension and stirred at room temperature for 3 h. Then, 0.50 g of 20.00% PEI aqueous solution was added dropwise and stirring was continued for 4 h. A few drops of acetic acid were added to adjust the pH to weakly acidic. 3.33 g of PEDOT:PSS solution was added and stirred at room temperature for 60 h to obtain the CNC-PEDOT:PSS complex. Half of the above CNC-PEDOT:PSS complex was taken and deionized water was added to 37.50 mL. The mixture was stirred for 5 min to disperse it evenly. Then, 5.63 g of PVA was added and stirred slowly at 92 °C for 4 h. The mixture was poured into a rectangular mold and the mold was placed in an ultrasonic cleaner at 1 °C. 0.10 g / mL of borax aqueous solution was slowly added dropwise. The mixture was allowed to stand at room temperature for 24 h to obtain the CNC-PEDOT:PSS / PVA hydrogel.

[0037] Example 3

[0038] 0.40 g of γ-glycidoxypropyltrimethoxysilane (GPTMS) was added to a 2.00 wt% CNC suspension and stirred at room temperature for 2 h. Then, 2.00 g of 20.00% PEI aqueous solution was added dropwise and stirring was continued for 3 h. A few drops of acetic acid were added to adjust the pH to weakly acidic. 13.32 g of PEDOT:PSS solution was added and stirred at room temperature for 72 h to obtain the CNC-PEDOT:PSS complex. 1 / 8 of the above CNC-PEDOT:PSS complex was taken and deionized water was added to 75.00 mL. The mixture was stirred for 5 min to disperse it evenly. Then, 11.25 g of PVA was added and stirred slowly at 93 °C for 5 h. The mixture was poured into a rectangular mold and placed in an ultrasonic cleaner at 2 °C. 0.12 g / mL of borax aqueous solution was slowly added dropwise. The mixture was allowed to stand at room temperature for 36 h to obtain the CNC-PEDOT:PSS / PVA hydrogel.

[0039] Example 4

[0040] 0.20 g of γ-glycidoxypropyltrimethoxysilane (GPTMS) was added to a 2.00 wt% CNC suspension and stirred at room temperature for 3 h. Then, 1.00 g of 20.00% PEI aqueous solution was added dropwise and stirring was continued for 4 h. A few drops of acetic acid were added to adjust the pH to weakly acidic. 6.66 g of PEDOT:PSS solution was added and stirred at room temperature for 72 h to obtain the CNC-PEDOT:PSS complex. One-quarter of the above CNC-PEDOT:PSS complex was taken and deionized water was added to 50.00 mL and stirred for 5 min to disperse it evenly. Then, 7.50 g of PVA was added and stirred slowly at 95 °C for 4 h. The mixture was poured into a rectangular mold and the mold was placed in an ultrasonic cleaner at 3 °C. 0.13 g / mL of borax aqueous solution was slowly added dropwise. The mixture was allowed to stand at room temperature for 30 h to obtain the CNC-PEDOT:PSS / PVA hydrogel.

[0041] Example 5

[0042] 0.10 g of γ-glycidoxypropyltrimethoxysilane (GPTMS) was added to a 2.00 wt% CNC suspension and stirred at room temperature for 2 h. Then, 0.50 g of 20.00% PEI aqueous solution was added dropwise and stirring was continued for 3 h. A few drops of acetic acid were added to adjust the pH to weakly acidic. 6.66 g of PEDOT:PSS solution was added and stirred at room temperature for 48 h to obtain the CNC-PEDOT:PSS complex. Half of the above CNC-PEDOT:PSS complex was taken and deionized water was added to 150.00 mL. The mixture was stirred for 5 min to disperse it evenly. Then, 22.50 g of PVA was added and stirred slowly at 90 °C for 4 h. The mixture was poured into a rectangular mold and placed in an ultrasonic cleaner at 4 °C. 0.14 g / mL of borax aqueous solution was slowly added dropwise. The mixture was allowed to stand at room temperature for 36 h to obtain the CNC-PEDOT:PSS / PVA hydrogel.

Claims

1. A method for preparing a hydrogel sensing material with both self-powered and self-healing properties, characterized in that, Includes the following steps: 1) Add an appropriate amount of γ-glycidoxypropyltrimethoxysilane (GPTMS) to a certain mass fraction of CNC suspension, stir at room temperature for a period of time to obtain a mixture; the appropriate amount of GPTMS in step 1) is 0.10-0.40 g; the certain mass fraction of CNC suspension is 2.00 wt%; the time is 2-3 h; 2) Add a certain amount of polyethyleneimine solution of appropriate concentration to the mixture obtained in step 1), stir at room temperature for a period of time to obtain CNC-PEI mixture; the appropriate concentration of the polyethyleneimine solution in step 2) is 20.00%, the certain amount is 0.5-2g, and the time is 3-4h; 3) Add a few drops of acetic acid to the CNC-PEI mixture obtained in step 2) until it is adjusted to a weakly acidic state; 4) Add an appropriate amount of PEDOT:PSS solution to the CNC-PEI mixture obtained in step 3), stir at room temperature for a suitable time until uniformly dispersed to obtain the CNC-PEDOT:PSS complex; the appropriate amount of PEDOT:PSS solution in step 4) is 3.33-13.32 g; the suitable time is 48-72 h; 5) Take an appropriate amount of the CNC-PEDOT:PSS complex obtained in step 4), centrifuge until the supernatant is neutral, add deionized water to an appropriate volume, and stir at room temperature for a suitable time until uniformly dispersed; the appropriate amount of CNC-PEDOT:PSS complex in step 5) is 1 / 8 to 1 / 2; the appropriate amount of deionized water added is 30.00 to 150.00 mL; the suitable time is 5 min; 6) Add an appropriate amount of polyvinyl alcohol to the product obtained in step 5), place it in a water bath, heat and stir at low speed for a period of time to obtain CNC-PEDOT:PSS / PVA mixture; the appropriate amount in step 6) is 4.5-22.5g, the temperature of the water bath is 90-95℃, and the time is 3-5h; 7) Slowly add an appropriate concentration of borax aqueous solution to the CNC-PEDOT:PSS / PVA mixture obtained in step 6), and let it stand at room temperature for a period of time to obtain CNC-PEDOT:PSS / PVA hydrogel; the appropriate concentration of the borax aqueous solution in step 7) is 0.10-0.15 g / mL; the standing time is 24-48 h.

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