CN116144060A - Preparation method of multi-scale cellulose gel bionic electronic skin - Google Patents

Abstract

The invention relates to a preparation method of bionic electronic skin by using a multi-scale cellulose gel, which takes [ Bmim ] Cl ionic liquid as a thermal ionic liquid source and directly introduces the thermal ionic liquid into BC hydrogel, so that flexible and transparent multi-scale M-gel is prepared simply and in one step; m-gel has excellent designability, and the multi-scale structure, mechanical property, electrochemical property and the like of the M-gel can be controlled by controlling the degree of molecular; based on the outstanding performance of M-gel, inspired by a tongue structure and a feedback mechanism, the multi-perception bionic electronic skin is designed, the great application potential and significance of the multi-perception bionic electronic skin in an intelligent robot are shown, the thought is provided for the structure and performance development of other soft functional materials, and the multi-scale structure endows the M-gel with excellent mechanical performance and ion conductivity, and has high transparency and flexibility. The preparation method has the advantages of simple operation and expandability, and prepares the flexible and transparent multi-sensing electronic skin.

Description

Preparation method of multi-scale cellulose gel bionic electronic skin

Technical Field

The invention relates to a bionic electronic skin preparation method, in particular to a multi-scale cellulose gel bionic electronic skin preparation method.

Background

Because of abundant crystallization areas and hydrogen bond networks in cellulose, the cellulose is difficult to regulate and design the molecular-scale structure, which limits the performance development and application to a certain extent. The [ Bmim ] Cl ionic liquid can break the intra-molecular chain/inter-molecular chain hydrogen bond network to form a cellulose single molecular chain and construct a cellulose molecular system, which is beneficial to the spatial configuration regulation, the morphological structure design and the performance development of cellulose at molecular scale and endows the cellulose with unique performance attributes and advanced application potential. Most of the designs of cellulose materials are now focused on the nano-scale, and there are few uses of the dynamic relationship between the properties of cellulose itself and molecules at the molecular scale to construct cellulose-based materials.

Conventional electronic skin mostly uses silicon or silicon oxide as a base material, which lacks flexibility and is difficult to degrade. In order to make the flexibility and comfort of the electronic skin more similar to those of human skin, the base material often needs to be chemically synthesized into a high polymer material with flexibility and stretchability through complicated machining. However, most polymer matrices are poorly degradable and are electronic insulators, not having ionic conductivity. Thus, it is desirable to incorporate conductive materials into the polymer matrix by mixing, stacking layer by layer, 3D printing, or the like, to achieve signal capture and feedback. These are undoubtedly cumbersome and high carbon emissions processes, which may cause problems such as poor stability of the electronic skin interface, great environmental pollution in the production process, etc. Most of the current electronic skin has single sensing function, cannot simultaneously meet various requirements and has certain limitation, so that the multifunctional electronic skin needs to be prepared to meet the requirements in the actual use process.

The electronic skin is an emerging flexible wearable device, however, most of the existing electronic skin involves complicated process flow and high-energy-consumption operation steps in preparation, and the base material is a synthetic high-molecular material which mostly lacks ion conductivity and is not easy to degrade, so that the performance development and advanced application of the electronic skin are greatly limited.

The human tongue is a muscular organ, one of the most flexible and most sensitive body parts of the human body, and can simultaneously feel various gustatory stimuli (e.g., sour, sweet, bitter, spicy and astringent). Thousands of receptor cells and connective tissues exist in the tongue, and the receptor cells buried in the connective tissues have regional structures and sensing capacities and can distinguish the stimulus of the external environment and convert the stimulus into corresponding ion signals; the connective tissue is used as a flexible conductor to transmit the ion signal generated after external stimulus to the nerve center of human body, so as to form accurate behavior feedback. The M-gel prepared by the method has good flexibility, high mechanical property, high ion conductivity and excellent performance stability, has ion transmission capacity similar to tongue connective tissue, and has potential as an electronic skin flexible matrix.

Disclosure of Invention

The invention aims to provide a preparation method of a multi-scale cellulose gel bionic electronic skin, which is based on a dynamic cooperative adjustable relation between cellulose molecule in-situ self-assembly and a molecular process, prepares a multi-scale M-gel with controllable and adjustable mechanical property and ion conductivity by taking BC hydrogel and [ Bmim ] Cl ion liquid as basic materials, builds the bionic electronic skin based on the multi-scale M-gel, has multiple perceptibility and biocompatibility and has a wide application prospect.

The invention aims at realizing the following technical scheme:

a method for preparing multi-scale cellulose gel bionic electronic skin, which comprises the following preparation processes:

step one: preparation of ionic liquids

Weighing 1-methylimidazole, putting the 1-methylimidazole into an oven at 85 ℃ for 30 minutes, and mechanically stirring the dehumidified 1-methylimidazole in an oil bath at 65 ℃ for 30 minutes under the protection of an anhydrous calcium chloride condenser tube at a speed of 1000r/min in a reflux way; then 1-chlorobutane is weighed and slowly added into the stirring 1-methylimidazole drop by drop through a dropping funnel, the temperature of an oil bath pot is raised to 85 ℃, and the reflux mechanical stirring is continued for 10-13h until the reaction is complete;

slowly pouring the reacted mixed solution into a beaker filled with acetone, naturally cooling to room temperature, using seed crystal to induce crystallization, and putting into a refrigerator for cooling for 12 hours to obtain supernatant liquid with obvious layering and lower white crystal;

pouring out supernatant liquid in the beaker and putting the white crystal into a water bath kettle at 85 ℃ to be melted; purifying the obtained transparent liquid at 90 ℃ at a speed of 140r/min by a rotary evaporation method to remove unreacted raw materials and solvents in the [ Bmim ] Cl ionic liquid; after 1h, collecting colorless and transparent [ Bmim ] Cl ionic liquid until no bubbles are generated in the solution in the rotary evaporation bottle;

step two: preparation of a molecular gel

Placing the [ Bmim ] Cl ionic liquid into an oven at 85 ℃ for preheating; after 30 minutes, weighing the [ Bmim ] Cl ionic liquid with the mass 5 times that of the BC hydrogel to be treated, dripping the weighed [ Bmim ] Cl ionic liquid dropwise and uniformly onto the surface of the BC hydrogel, and standing for 30 minutes; the BC hydrogel infiltrated by the [ Bmim ] Cl ionic liquid is clamped in two clean glass plates, the two clean glass plates are placed in an oven at 80 ℃ and are subjected to heavy pressure, and the glass plates are subjected to heat treatment for 0, 5, 10, 30, 50 and 70 minutes respectively, so that M-gel with different molecular degrees is obtained and named as M-gel-0/5/10/30/50/70.

Step three: preparation of bionic electronic skin

The sensing material to be used comprises poly (3, 4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS), carbon Nanotubes (CNTs) and nano nickel powder are placed in an oven at 85 ℃ for 4 hours to fully remove water; placing a required sensing unit shape mold on the M-gel, flattening bubbles and folds on the surface, and placing the mold in a baking oven at 50 ℃ for preheating for 10 minutes; lightly brushing the dried sensing materials on the surface of the M-gel according to the shape of a sensing unit die, and transferring the sensing materials to a 50 ℃ oven; after 15 minutes, taking out M-gel loaded with sensing materials in the oven, blowing off active substances floating on the surface of the M-gel with a ear washing ball and not firmly adhered, and repeating the process of loading the sensing materials until the shape of the sensing unit on the die is completely covered by the sensing materials; and finally, taking out the mould, connecting all the sensing units by using conductive silver paint, and putting the sensing units into a 50 ℃ oven for curing and shaping, thus obtaining the flexible bionic electronic skin.

The invention has the advantages and effects that:

1. according to the invention, the [ Bmim ] Cl ionic liquid is used as a thermal ionic liquid source, and is directly introduced into the BC hydrogel, so that a flexible and transparent multi-scale M-gel is prepared simply and in one step; m-gel has excellent designability, and the multi-scale structure, mechanical property, electrochemical property and the like of the M-gel can be controlled by controlling the degree of molecular; based on the outstanding performance of M-gel, inspired by a tongue structure and a feedback mechanism, the multi-perception bionic electronic skin is designed, the great application potential and significance of the multi-perception bionic electronic skin in an intelligent robot are shown, and the thinking is provided for the structure and performance development of other soft functional materials.

2. The invention adopts biodegradable bacterial cellulose and green ionic liquid as raw materials to construct a multi-scale cellulose molecular gel. A thermal ionic liquid source ([ Bmim ] Cl) is directly introduced into a degradable bacterial cellulose hydrogel (BC hydrogel) serving as a main raw material, so as to construct a multi-scale cellulose molecular gel (M-gel). Inside the M-gel there is not only a nano-scale BC fiber skeleton, but also a dense interweaving layer formed by the molecular chains of BC fibers being opened and self-assembled. The multi-scale structure endows M-gel with excellent mechanical property and ion conductivity, and has high transparency and flexibility.

3. The invention constructs multi-perception bionic electronic skin by adopting the thought of bionic tongue, takes human tongue as a heuristic, uses M-gel material as a flexible matrix to simulate connective tissue of tongue based on the self adhesiveness of M-gel, loads different kinds of sensing materials on the M-gel material to simulate different receptor cells on tongue, and prepares the electronic skin which has simple operation, expandability, flexibility and transparency.

Drawings

FIG. 1 optical image of BC hydrogel for electronic skin converted to M-gel;

FIG. 2M-gel molecular process and self-assembly process schematic;

FIG. 3 SEM images of bacterial cellulose hydrogels with M-gel;

FIG. 4 degrees of molarization of M-gels at different molarization times (inset shows M-gel real-time SEM images at different molarization times);

FIG. 5 tensile stress-strain curves for different molecular times M-gel;

FIG. 6 is an optical image of the modulus of elasticity and work of rupture values of M-gel at 30 minutes of the molecular time and lifting a weight of 2 kg;

FIG. 7 comparison of ionic conductivities of different molecular times M-gel;

FIG. 8M-gel is a comparison of mechanical and electrical properties with other various ionic gel materials;

FIG. 9 is a schematic diagram of a multi-perception biomimetic electronic skin-sensing stimulation;

FIG. 10 is a diagram of the flexibility and fit of the multi-sensory biomimetic electronic skin to the human body;

FIG. 11 is a waveform diagram of touch vibration current signals of multi-sensing electronic skin;

FIG. 12 is a waveform of a pressure current signal of the multi-sensing electronic skin;

FIG. 13 is a waveform of a temperature current signal of multi-sensing electronic skin;

FIG. 14 is a waveform of a humidity current signal of multi-sensing electronic skin;

FIG. 15 is a waveform of a magnetic current signal in the horizontal direction of multi-sensing electronic skin;

FIG. 16 is a waveform of a magnetic current signal in the vertical direction of multi-sensing electronic skin;

FIG. 17 is a waveform of airflow current signals for multi-sensing electronic skin;

fig. 18 multiple perception electronic skin can simultaneously feed back multiple external stimuli.

Detailed Description

The present invention will be described in detail with reference to the embodiments shown in the drawings.

The invention provides a construction method for directly introducing a thermal ionic liquid source into BC hydrogel to make the BC hydrogel be in-situ molecularly into M-gel; the adjustable property of the M-gel is derived from a thermal ionic liquid source, a multi-scale structure endowed by the cooperative self-assembly of water and cellulose fibers, and adjustment mechanisms such as quantification of the degree of molecular change; m-gel is used as a matrix material to construct a flexible multi-sensing sensor, a method for simulating electronic skin and application thereof in the field.

The invention uses the structure of the tongue and a feedback mechanism as inspiration, and provides a simple multi-scale M-gel strategy which has controllable preparation structure and performance and can be designed to develop multi-perception bionic electronic skin. The cellulose fibers are molecularly in situ into macromolecular chains in one step by a method of directly introducing a source of a thermal ionic liquid into the BC hydrogel. By controlling the degree to which the gel is molecularly incorporated, the properties of the M-gel can be tailored. Based on the advantages, the prepared M-gel has excellent performance combination, the tensile strength is more than 7.84MPa, the elastic modulus can reach 10.2MPa, the weight exceeding 50000 times of the M-gel can be lifted, the ionic conductivity can reach 62.58mS/cm, the M-gel has anti-strain performance, and the M-gel still has excellent conductive stability in an open environment. Meanwhile, the multi-perception bionic electronic skin is prepared by combining multiple sensing materials by utilizing the self adhesion of M-gel. The property of the gel is regulated by controlling the degree of the gel molecules, the molecular gel with excellent property is prepared, and the property of the gel is regulated by changing the stimulation time of the thermal ionic liquid source to the BC hydrogel and changing the degree of the gel molecules. When [ Bmim ] + and Cl-in the hot ionic liquid source are introduced into the BC hydrogel, the original steady state between cellulose and H2O is broken, and diffusion-driven turing unstable behavior is generated between BC fibers, H2O and anions and cations. During the entire introduction of the hot ionic liquid source, the [ Bmim ] + and Cl-as activators interact with BC fibers, breaking the intermolecular/intramolecular hydrogen bonds of cellulose to form cellulose macromolecular chains (this process is called a molecularly process); at the same time, H2O acts as an inhibitor, inducing hydrogen bonds between cellulose molecules, reconstructing a hydrogen bond network, inhibiting the molecular process (this is a self-assembly process of BC molecular chains). It is the dynamic competition relationship between the molecular behavior (converting fiber into molecular chain) and the cellulose molecular self-assembly behavior (constructing intermolecular hydrogen bond topological network), so that M-gel has a unique multi-scale structure, the whole system is promoted to present a dynamic and adjustable behavior mode and performance characteristics, and the strong mechanical performance and performance durability of the M-gel material can be endowed.

Examples

The preparation method comprises the following specific preparation steps:

step one: preparation of ionic liquids

1mol (about 82.1 g) of 1-methylimidazole was weighed and placed in an oven at 85℃for 30 minutes, and the dehumidified 1-methylimidazole was mechanically stirred in an oil bath at 65℃under the protection of an anhydrous calcium chloride condenser at a speed of 1000r/min for 30 minutes under reflux. 1mol (about 92.57 g) of 1-chlorobutane was then weighed and added slowly dropwise via a dropping funnel to the stirring 1-methylimidazole, the oil bath was warmed to 85℃and mechanical stirring was continued under reflux for 10-13h until the reaction was complete.

Slowly pouring the reacted mixed solution into a beaker filled with 300ml of acetone, naturally cooling to room temperature, using seed crystal to induce crystallization, and cooling in a refrigerator for 12h to obtain supernatant and lower white crystal with obvious delamination.

The supernatant liquid in the beaker was decanted and the white crystals were placed in a water bath at 85 ℃ to melt. The obtained transparent liquid was purified by rotary evaporation at 90℃at a speed of 140r/min to remove unreacted starting materials and solvents from the [ Bmim ] Cl ionic liquid. After about 1h, until no bubble is generated in the solution in the rotary evaporation bottle, colorless and transparent [ Bmim ] Cl ionic liquid can be collected.

Step two: preparation of a molecular gel

The [ Bmim ] Cl ionic liquid was placed in an oven at 85 ℃ for preheating. After 30 minutes, weighing the [ Bmim ] Cl ionic liquid with the mass 5 times of that of the BC hydrogel to be treated, dripping the weighed [ Bmim ] Cl ionic liquid on the surface of the BC hydrogel dropwise and uniformly, and standing for 30 minutes. The BC hydrogel infiltrated by the [ Bmim ] Cl ionic liquid is clamped in two clean glass plates, the two clean glass plates are placed in an oven at 80 ℃ and are subjected to heavy pressure, and the glass plates are subjected to heat treatment for 0, 5, 10, 30, 50 and 70 minutes respectively, so that M-gel with different molecular degrees can be obtained, and the M-gel is named as M-gel-0/5/10/30/50/70.

Step three: preparation of bionic electronic skin

The sensing material to be used comprises poly (3, 4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS), carbon Nanotubes (CNTs) and nano nickel powder were placed in an oven at 85℃for about 4 hours to sufficiently remove water. The required sensor unit shaped mold was placed on the M-gel, the surface bubbles and wrinkles were smoothed, and placed in an oven at 50℃for 10 minutes to preheat. And (3) lightly brushing the dried sensing materials on the surface of the M-gel according to the shape of the sensing unit mould, and transferring the sensing materials into a 50 ℃ oven. After 15 minutes, the M-gel loaded with the sensing material in the oven is taken out, the active substances floating on the surface of the M-gel are blown off by the ear-washing ball, and the process of loading the sensing material is repeated until the shape of the sensing unit on the die is completely covered by the sensing material. And finally, taking out the mould, connecting all the sensing units by using conductive silver paint, and putting the mould into a 50 ℃ oven for curing and shaping to finish the preparation of the flexible bionic electronic skin.

Performance test:

selecting a universal mechanical tester to test mechanical tensile property, adhesiveness and other mechanical properties of the M-gel and the bionic electronic skin; an electrochemical workstation is selected to test the ionic conductivity of the M-gel and the sensing performance of the bionic electronic skin; and testing the light transmittance of the M-gel by using an ultraviolet-visible light spectrophotometer.

The foregoing description is only of the preferred embodiments of the invention, and all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (1)

1. A method for preparing a multi-scale cellulose gel bionic electronic skin, which is characterized by comprising the following preparation processes:

step one: preparation of ionic liquids

Weighing 1-methylimidazole, putting the 1-methylimidazole into an oven at 85 ℃ for 30 minutes, and mechanically stirring the dehumidified 1-methylimidazole in an oil bath at 65 ℃ for 30 minutes under the protection of an anhydrous calcium chloride condenser tube at a speed of 1000r/min in a reflux way; then 1-chlorobutane is weighed and slowly added into the stirring 1-methylimidazole drop by drop through a dropping funnel, the temperature of an oil bath pot is raised to 85 ℃, and the reflux mechanical stirring is continued for 10-13h until the reaction is complete;

slowly pouring the reacted mixed solution into a beaker filled with acetone, naturally cooling to room temperature, using seed crystal to induce crystallization, and putting into a refrigerator for cooling for 12 hours to obtain supernatant liquid with obvious layering and lower white crystal;

pouring out supernatant liquid in the beaker and putting the white crystal into a water bath kettle at 85 ℃ to be melted; purifying the obtained transparent liquid at 90 ℃ at a speed of 140r/min by a rotary evaporation method to remove unreacted raw materials and solvents in the [ Bmim ] Cl ionic liquid; after 1h, collecting colorless and transparent [ Bmim ] Cl ionic liquid until no bubbles are generated in the solution in the rotary evaporation bottle;

step two: preparation of a molecular gel

Placing the [ Bmim ] Cl ionic liquid into an oven at 85 ℃ for preheating; after 30 minutes, weighing the [ Bmim ] Cl ionic liquid with the mass 5 times that of the BC hydrogel to be treated, dripping the weighed [ Bmim ] Cl ionic liquid dropwise and uniformly onto the surface of the BC hydrogel, and standing for 30 minutes; clamping BC hydrogel infiltrated by [ Bmim ] Cl ionic liquid into two clean glass plates, putting the two clean glass plates into an oven at 80 ℃ and applying heavy pressure on the glass plates, and respectively performing heat treatment for 0, 5, 10, 30, 50 and 70 minutes to obtain M-gel with different molecular degrees, which is named as M-gel-0/5/10/30/50/70;

step three: preparation of bionic electronic skin

The sensing material to be used comprises poly (3, 4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS), carbon Nanotubes (CNTs) and nano nickel powder are placed in an oven at 85 ℃ for 4 hours to fully remove water; placing a required sensing unit shape mold on the M-gel, flattening bubbles and folds on the surface, and placing the mold in a baking oven at 50 ℃ for preheating for 10 minutes; lightly brushing the dried sensing materials on the surface of the M-gel according to the shape of a sensing unit die, and transferring the sensing materials to a 50 ℃ oven; after 15 minutes, taking out M-gel loaded with sensing materials in the oven, blowing off active substances floating on the surface of the M-gel with a ear washing ball and not firmly adhered, and repeating the process of loading the sensing materials until the shape of the sensing unit on the die is completely covered by the sensing materials; and finally, taking out the mould, connecting all the sensing units by using conductive silver paint, and putting the sensing units into a 50 ℃ oven for curing and shaping, thus obtaining the flexible bionic electronic skin.

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