CN110387056B

CN110387056B - Friction generator based on vegetable protein and preparation method thereof

Info

Publication number: CN110387056B
Application number: CN201910575038.4A
Authority: CN
Inventors: 平建峰; 姜成美
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2019-06-28
Filing date: 2019-06-28
Publication date: 2020-09-18
Anticipated expiration: 2039-06-28
Also published as: CN110387056A

Abstract

The invention discloses a friction generator based on vegetable protein and a preparation method thereof. The triboelectric generator comprises a triboelectric negative layer and a protein film, wherein the protein film and the triboelectric negative layer are stacked in a face-to-face mode, and the respective back surfaces are adhered or plated with electrodes, or only the protein film back surface or the electronegative layer back surface is provided with a grounded electrode; dissolving protein powder in water or ethanol water solution, adding plasticizer, and performing heat treatment to denature protein to obtain more extended structure required by film formation; finally evaporating the solvent and drying to obtain the protein film with uniform texture, good transparency and good flexibility. The invention creatively utilizes plant protein as a triboelectric material and a friction nano generator as a biodegradable mulching film, creates a space electric field promoting system for agriculture and is further used for the growth of crops.

Description

Friction generator based on vegetable protein and preparation method thereof

Technical Field

The invention relates to a friction nano-generator, in particular to a friction nano-generator based on vegetable protein and a preparation method thereof.

Background

With the rapid development of flexible and portable electronic products, a triboelectric nanogenerator capable of efficiently converting various forms of mechanical energy into electrical energy will be used as a mainstream of energy supply in the world in the future. Most research work on triboelectric nanogenerators to date has been focused on structural design or material innovation.

Materials widely used in tribo-nanogenerators at present include polyamide (nylon) -11 and polyethylene terephthalate (PET), and the like. It is worth noting that these materials are not completely degradable and are prone to release hazardous chemicals, which will certainly place a great burden on the environment as electronic products will become electronic waste with the rapid upgrade. Accordingly, there is increasing interest in flexible devices made from biodegradable and non-toxic materials.

In recent years, friction generators made of various biomaterials such as starch, chitosan, silk nanofibers, gelatin and bacterial nanocellulose are widely applied to the fields of implantable devices, medical care, environmental monitoring and the like. However, the cumbersome processing steps will make it difficult to put it into practical use. So far, the application of vegetable protein in the triboelectric nano-generator is still a blank, and the triboelectric property and mechanism thereof are still to be explored.

Disclosure of Invention

In order to solve the problems existing in the background technology and fill the blank, the invention aims to introduce plant protein into the field of triboelectric generators as a new triboelectric material and innovatively apply the triboelectric generator based on the plant protein as a biodegradable mulching film to a space electric field growth promotion system. The friction nano generator can be used for collecting mechanical energy in the environment and can be used as a biodegradable mulching film for a space electric field growth promotion system.

The technical scheme of the invention is as follows:

a vegetable protein-based triboelectric generator:

the triboelectric generator comprises a triboelectric negative layer and a plant protein film, wherein the plant protein film is used as a friction electron-donating layer, the plant protein film and the triboelectric negative layer are stacked face to face, and electrodes are adhered or plated on the respective back surfaces, or only the protein film back surface or the triboelectric negative layer back surface is provided with a grounded electrode.

The invention firstly proposes the application of the plant protein film in friction power generation, and also firstly proposes the application of the friction power generator with the plant protein film in the growth of the biological tissues.

The protein film is prepared by adopting the following method: dissolving protein powder which is difficult to dissolve in water (the protein is uniformly dispersed by adjusting the pH value to be far away from the isoelectric point when the protein powder is dissolved in the water) or ethanol water solution, then adding a plasticizer (the interaction between protein molecules can be reduced, so that the tensile property of the membrane is improved, the flexibility is enhanced, and the protein is difficult to crack), and performing heat treatment at a temperature higher than the glass transition temperature to denature the protein to obtain a more extended structure required by membrane formation, wherein the network structure strength of the protein membrane is enhanced by forming hydrogen bonds, ionic bonds, covalent bonds and hydrophobic effects in the process of protein chains, wherein the network structure strength of the protein membrane is enhanced by promoting the oxidation of sulfydryl into disulfide bonds; finally evaporating the solvent and drying to obtain the protein film with uniform texture, good transparency and good flexibility.

The triboelectric negative layer is made of polytetrafluoroethylene (Teflon), Polydimethylsiloxane (PDMS), polyvinyl chloride (PVC), polyimide (Kapton), silicone rubber (Ecoflex), polylactic acid (PLA) and the like, and can be used as a triboelectric negative layer material of the friction generator.

Secondly, a preparation method of the friction generator based on the vegetable protein comprises the following steps:

firstly, preparing a friction electron-donating layer-protein film: dissolving protein powder which is difficult to dissolve in water (the protein is uniformly dispersed by adjusting the pH value to be far away from the isoelectric point when the protein powder is dissolved in the water) or ethanol water solution, then adding a plasticizer (the interaction between protein molecules can be reduced, so that the tensile property of the membrane is improved, the flexibility is enhanced, and the protein is difficult to crack), and performing heat treatment at a temperature higher than the glass transition temperature to denature the protein to obtain a more extended structure required by membrane formation, wherein the network structure strength of the protein membrane is enhanced by forming hydrogen bonds, ionic bonds, covalent bonds and hydrophobic effects in the process of protein chains, wherein the network structure strength of the protein membrane is enhanced by promoting the oxidation of sulfydryl into disulfide bonds; finally evaporating the solvent and drying to obtain a protein film with uniform texture, good transparency and good flexibility; the protein film and the triboelectric negative layer are stacked face-to-face, with the respective back surfaces being either adhered or plated with electrodes or only the protein film back surface or the triboelectric negative layer back surface being provided with a grounded electrode.

The protein powder is rice protein, peanut protein isolate, soybean protein isolate, wheat gluten, and zein powder.

The plasticizer is polyhydric alcohol (glycerol, propylene glycol, ethylene glycol, sorbitol, polyethylene glycol, etc.).

The step 1) is specifically as follows: dispersing protein in an aqueous solution or an ethanol aqueous solution with the concentration of 70-90% (the mass fraction of the protein is 1-10%, w/w) to prepare a protein solution; then adding plasticizer (such as glycerol) with a mass of 10-60% (w/w) of protein into the protein solution, heating in water bath at 60-95 deg.C for denaturation, stirring for 30-60min, degassing under vacuum for 10 min, pouring into a mold, and drying by evaporation at 30-70 deg.C in an oven.

The protein is rice protein, peanut protein isolate, soybean protein isolate and wheat gluten, and is characterized in that the protein and glycerol are mixed in a deionized water solution, after magnetic stirring, the pH value of a protein precursor solution is adjusted by using a 1M sodium hydroxide solution, and the pH value of the protein solution is adjusted to 12; the protein solution was then heated and stirred at 65 ℃ for 30 minutes and degassed under vacuum for 10 minutes to remove air bubbles.

The protein is zein, and specifically the zein and glycerol are dissolved in an ethanol water solution with the mass concentration of 70%, the protein solution is directly heated and stirred for 30 minutes at 65 ℃, and then the protein solution is degassed for 10 minutes in vacuum.

The friction generator is used for the growth application of crops and has a promoting effect on the growth of the crops. The triboelectric generator is placed on the soil, the protein film is arranged on one side contacting the soil, and force is applied to the triboelectric generator to enable the triboelectric negative layer and the protein film to approach, separate or slide relatively, namely mechanical energy is applied, so that an electric field for promoting growth is generated for crops.

As shown in fig. 4, the friction generator of the present invention can have four operation modes, a vertical contact-separation mode, a horizontal sliding mode, a single electrode mode, and an independent layer mode.

Vertical contact-separation mode: in this configuration, the protein films are stacked face-to-face with the triboelectric negative layer, with their respective back surfaces adhered or plated with electrodes. The triboelectric negative layer and the protein film are in contact with each other, and surface charges with opposite signs are formed on two contact surfaces. When the two surfaces are separated by an external force, a small air gap is formed between the two surfaces, and an induced potential difference is formed between the two electrodes. When the two electrodes are connected together by the load, electrons flow from one electrode to the other electrode through the load, and a reverse potential difference is formed to balance the electrostatic field. When the air gap between the triboelectric negative layer and the protein film is closed, the potential difference formed by the triboelectric charges disappears and the electrons can flow back. The electric field which changes along with time is continuously circulated, and the electric field which changes along with time drives electrons to flow back and forth on the electrode on the back of the protein film and the electrode on the back of the triboelectric negative layer, so that alternating current is generated.

Horizontal sliding mode: this mode is the same as the initial structure of the vertical contact-separation mode, in which the protein films are stacked face-to-face with the triboelectric negative layer, their respective back surfaces are adhered or plated with electrodes, and the two electrodes are connected to each other by an external circuit. When the protein film is in contact with the triboelectric negative layer, relative slip between the two materials occurs along a horizontal direction parallel to the surfaces, which can also generate triboelectric charges on both surfaces. Thus, polarization is formed in the horizontal direction, and electrons can be driven to flow between the electrode on the back surface of the protein film and the electrode on the back surface of the triboelectric negative layer so as to balance the electrostatic field generated by triboelectric charges. An ac output can be generated by periodic sliding separation and closure. This is the basic principle of sliding type friction nano-generators, and this sliding can exist in many forms, including planar sliding, cylindrical sliding, and disc sliding, etc.

Single electrode working mode: the protein film and the triboelectric negative layer are combined together, and an electrode is arranged on the back surface of the protein film or the back surface of the triboelectric negative layer and is grounded, so that the triboelectric generator is formed. When the upper triboelectric negative layer approaches or leaves the lower protein film, or the upper triboelectric negative layer moves frictionally against the lower protein film, the local electric field distribution will change, so that an electronic exchange will take place between the lower electrode and ground to balance the potential change on the electrode.

Independent layer mode: two unconnected symmetrical electrodes are adhered or plated on the back of the protein film, the size and the distance between the electrodes can be controlled properly, and the two electrodes are connected through an external circuit. When the triboelectric negative layer reciprocates between the two electrodes on the surface of the protein film, the change of the potential difference can be generated between the two electrodes, and then electrons are driven to flow back and forth between the two electrodes through an external circuit load so as to balance the change of the potential difference.

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

firstly, on the material, the plant protein biological material is never introduced into the field of friction generators, and the plant protein has strong electron donating capability due to a plurality of amino-hydroxyl groups and other groups on the surface, so that the plant protein is a natural candidate material of the friction nanometer generator;

secondly, compared with other biological materials, the plant protein film has simple preparation process, wide source and low price, and is often discarded as waste;

finally, the prepared friction nano generator based on the plant protein is applied to an agricultural space electric field growth promotion system as a mulching film for the first time, and bean seedlings are taken as test objects, so that a good technical effect result is obtained, and the friction nano generator has a great application prospect.

The invention creatively utilizes the vegetable protein as the triboelectric material, applies various vegetable proteins to triboelectric behavior, including rice protein, peanut protein isolate, soybean protein isolate, wheat gluten and zein, innovatively utilizes the friction nano generator as the biodegradable mulching film, creates a space electric field promotion system for agriculture, and obtains considerable and remarkable technical achievements.

Drawings

FIG. 1 is a diagram showing arrangement positions of rice protein A, peanut protein B, soybean protein C, wheat gluten D and zein in a triboelectric series of a common material according to the direction of an output current signal in an embodiment of the present invention;

FIG. 2 is a graph of the output performance of a friction nanogenerator based on five proteins according to an embodiment of the invention, wherein A is the output voltage and B is the output current;

FIG. 3 is a graph of the fatigue test result of the friction nano-generator based on rice protein in the embodiment of the invention, which still has good reliability after 40000 times of continuous operation;

fig. 4 is a schematic diagram of four modes of operation of the present invention.

Detailed Description

The invention is further illustrated by the following figures and examples.

The following embodiments of the invention are specifically realized:

1) firstly, preparing a protein membrane: dispersing protein in water solution or ethanol water solution with concentration of 70% -90% (1-10%, w/w) to prepare protein solution; then adding plasticizer (such as glycerol) with a mass of 10-60% (w/w) of protein into the protein solution, heating in water bath at 60-95 deg.C for denaturation, stirring for 30-60min, degassing under vacuum for 10 min, pouring into a mold, and drying by evaporation at 30-70 deg.C in an oven.

In one embodiment, the dried protein film is finally peeled off, and the protein film is placed under constant temperature and humidity conditions, so that the protein film can be balanced in moisture under certain temperature and humidity conditions for subsequent electrical testing.

2) Triboelectric negative layer: the triboelectric negative layer is made of polytetrafluoroethylene (Teflon), Polydimethylsiloxane (PDMS), polyvinyl chloride (PVC), polyimide (Kapton), silicone rubber (Ecoflex), polylactic acid (PLA) and the like, and can be used as a triboelectric negative layer material of the friction generator.

The invention firstly tests the electron-donating ability by forming a triboelectric pair by the protein film and common test materials (nylon-11, woven wool, woven silk, aluminum, paper, acetate fiber, PET, PDMS and PTFE), and the specific operation method is as follows: the testing material is arranged above the protein film, the protein film is arranged below the testing material, the electrode is arranged at the bottom of the protein film, the electrode is grounded, when the testing material is in contact with and separated from the protein film, a current signal generated by a multimeter is used for testing, the direction of current is judged according to the positive and negative of the current signal, so that the flowing direction of electrons is obtained, the charge polarity of the testing material and the surface of the protein film is further judged, and the strength of the testing material and the protein film for supplying the electrons is deduced.

Referring to fig. 1, five vegetable protein films (rice protein, peanut protein isolate, soybean protein isolate, wheat gluten, zein) are respectively compared with the triboelectric sequence of a common test material to determine the positions of the five vegetable proteins in the triboelectric sequence. As can be seen from the figure, the protein film has strong electron-donating ability and is arranged at the front position of the triboelectric sequence of common materials.

Examples of the embodiments

Example 1

1) First, a protein film was prepared by dispersing rice protein, peanut protein isolate, soybean protein isolate, and wheat gluten in distilled water (5%, w/w) to prepare a film forming solution, and in addition, zein was dispersed in an ethanol aqueous solution (5%, w/w) having a concentration of 70%. Then, glycerol was added to the five protein solutions in an amount of 30% (w/w) by mass of the proteins.

2) In this example, the following specific examples of rice protein, peanut protein isolate, soybean protein isolate, and wheat gluten are: 5g of vegetable protein was mixed with 1.5g of glycerol in 100mL of deionized water, and after magnetic stirring for 10 minutes, the pH of the protein precursor solution was then adjusted. Adjusting the pH value of the protein solution to 12 by using 1M sodium hydroxide solution; the protein solution was then heated and stirred at 65 ℃ for 30 minutes and degassed under vacuum for 10 minutes to remove air bubbles.

In this example, specifically for zein, the following is that 5g zein and 1.5g glycerol are dissolved in 100mL 70% ethanol aqueous solution, the protein solution is heated and stirred at 65 ℃ for 30 minutes, and then the degassing process is carried out under vacuum for 10 minutes.

3) The final film-forming solution was finally poured into round teflon moulds (diameter 3cm) and dried in an oven at 60 ℃. The dried film was then peeled off and placed in a constant temperature and humidity incubator at 25 ℃ and 40% relative humidity for 24 hours, and then tested as a tribo electron donor layer.

The triboelectric negative layer a Polydimethylsiloxane (PDMS) film was used in this experiment. The PDMS film is prepared by uniformly mixing an elastic agent and a curing agent in a mass ratio of 10:1, vacuum degassing, and curing at 65-95 deg.C for 20-60min in an oven.

The protein film and the PDMS film are combined to form a triboelectric pair, an aluminum foil is placed at the bottom of the PDMS film to serve as an electrode, the protein film and the PDMS film are in contact separation, electrons flow in an external circuit, an electrometer and an oscilloscope are used for electrical testing, as shown in figure 2, the five protein films have output voltages and currents with different sizes, the output signal size sequence is consistent with the electron supply capacity, and the previous conclusion is further verified: the electron donating ability is rice protein, peanut protein isolate, soybean protein isolate, wheat gluten and zein respectively from large to small.

Example 2

Taking rice protein as an example, 5g of rice protein was mixed with 1.5g of glycerol in 100mL of deionized water, and after magnetically stirring for 10 minutes, the pH of the protein solution was adjusted to 12 using 1M sodium hydroxide solution. The protein solution was then heated and stirred at 65 ℃ for 30 minutes and degassed under vacuum for 10 minutes to remove air bubbles. The final film-forming solution was finally poured into round teflon moulds (diameter 3cm) and dried in an oven at 60 ℃. The dried film was finally peeled off and placed in a constant temperature and humidity incubator at 25 ℃ and 40% relative humidity for 24 hours for testing as a triboelectric donor layer.

Preparation of the triboelectric negative layer: the polylactic acid film was cut into a circular shape having a diameter of 3 cm.

Preparing a friction nano generator: the rice protein film and the polylactic acid film are combined into a triboelectric pair, an aluminum foil is placed on one side of the polylactic acid film to be used as an electrode to form a friction nano generator, and a voltage signal of the friction nano generator is measured by an oscilloscope. As shown in fig. 3, the signal remains stable over forty thousand cycles.

Example 3

After dissolving 5g zein with 1.5g glycerol in 100mL 70% strength ethanol aqueous solution, the protein solution was directly heated and stirred at 65 ℃ for 30 minutes, and then degassed under vacuum for 10 minutes. The final film-forming solution was finally poured into round teflon moulds (diameter 3cm) and dried in an oven at 60 ℃. The dried film was finally peeled off and placed in a constant temperature and humidity incubator at 25 ℃ and 40% relative humidity for 24 hours to test as a triboelectric donor layer.

Preparation of the triboelectric negative layer: the polylactic acid film was cut into a circular shape having a diameter of 3cm, and then poly (3, 4-ethylenedioxythiophene) -polystyrenesulfonic acid (PEDOT: PSS) was hung on one side of the polylactic acid film at 1000rpm as an electrode.

Combining the protein film and the polylactic acid film into a mulching film, and coating a conductive PEDOT: the PSS has a polylactic acid film on the upper part and an protein film on the side contacting with soil, and applies a certain force to the friction generator to simulate mechanical energy in the environment. Bean seedlings are taken as test objects, beans are soaked for 4 hours and then are placed into a constant-temperature constant-humidity incubator with the temperature of 25 ℃ and the relative humidity of 40% for culturing for three days, and after sprouting, the bean seedlings with the same length are selected and divided into two groups, namely a test group and a control group. The test group is placed in an electric field generated by a friction generator (the test group is placed for 4 hours every day), and the growth condition of the soybean seedlings is characterized by measuring the elongation and weight gain rate of the soybean seedlings after 48 hours.

TABLE 1

Table 1 bean seedlings are the subject of the present invention, and a friction nano-generator based on vegetable proteins is used as a mulch film to collect mechanical energy in the environment to generate an electric field for use in a growth promotion system. As can be seen from the above table 1, the electric field generated by the friction generator has an obvious promotion effect on the growth of bean seedlings, which indicates that the friction nano generator based on plant protein can be applied to an agricultural space electric field growth promotion system as a mulching film.

Claims

1. A vegetable protein based triboelectric generator, characterized in that: the triboelectric generator comprises a triboelectric negative layer and an egg white film, wherein the egg white film and the triboelectric negative layer are stacked face to face, and the respective back surfaces are adhered or plated with electrodes, or only the back surface of the egg white film or the back surface of the triboelectric negative layer is provided with a grounded electrode;

firstly, preparing a friction electron-donating layer-protein film: dissolving protein powder in water or ethanol water solution, adding plasticizer, and performing heat treatment to denature protein to obtain more extended structure required by film formation; finally evaporating the solvent and drying to obtain a protein film with uniform texture, good transparency and good flexibility; stacking the protein film and the triboelectric negative layer face to face, adhering or plating an electrode on the respective back surfaces or arranging a grounded electrode on only the protein film back surface or the electronegative layer back surface;

the protein membrane is prepared from rice protein, peanut protein isolate, soybean protein isolate, wheat gluten and zein;

when the protein is rice protein, peanut protein isolate, soybean protein isolate and wheat gluten, the protein and glycerol are mixed in a deionized water solution, after magnetic stirring, the pH value of a protein precursor solution is adjusted by using a 1M sodium hydroxide solution, and the pH value of the protein solution is adjusted to 12; the protein solution was then heated and stirred at 65 ℃ for 30 minutes, and degassed under vacuum for 10 minutes to remove air bubbles;

when the protein is zein, the zein and glycerol are dissolved in an ethanol water solution with the mass concentration of 70%, the protein solution is directly heated and stirred for 30 minutes at 65 ℃, and then the protein solution is degassed for 10 minutes in vacuum;

the friction generator collects mechanical energy in the environment, is applied to a space electric field growth promotion system as a biodegradable mulching film, and is used for growth of crops.

2. A vegetable protein based triboelectric generator according to claim 1, characterized in that: the triboelectric negative layer adopts polytetrafluoroethylene Teflon, polydimethylsiloxane PDMS, polyvinyl chloride PVC, polyimide Kapton, silicone rubber Ecoflex and polylactic acid PLA.

3. A preparation method of a friction generator based on vegetable protein is characterized in that: firstly, preparing a friction electron-donating layer-protein film: dissolving protein powder in water or ethanol water solution, adding plasticizer, and performing heat treatment to denature protein to obtain more extended structure required by film formation; finally evaporating the solvent and drying to obtain a protein film with uniform texture, good transparency and good flexibility; stacking the protein film and the triboelectric negative layer face to face, adhering or plating an electrode on the respective back surfaces or arranging a grounded electrode on only the protein film back surface or the electronegative layer back surface;

the protein powder is rice protein, peanut protein isolate, soybean protein isolate, wheat gluten and zein powder;

the protein is rice protein, peanut protein isolate, soybean protein isolate and wheat gluten, and is characterized in that the protein and glycerol are mixed in a deionized water solution, after magnetic stirring, the pH value of a protein precursor solution is adjusted by using a 1M sodium hydroxide solution, and the pH value of the protein solution is adjusted to 12; the protein solution was then heated and stirred at 65 ℃ for 30 minutes, and degassed under vacuum for 10 minutes to remove air bubbles;

4. The method of claim 3, wherein the friction generator is prepared from a plant protein, and the method comprises the following steps: the plasticizer is polyalcohol.

5. The method of claim 3, wherein the friction generator is prepared from a plant protein, and the method comprises the following steps: the triboelectric negative layer adopts polytetrafluoroethylene Teflon, polydimethylsiloxane PDMS, polyvinyl chloride PVC, polyimide Kapton, silicone rubber Ecoflex and polylactic acid PLA.

6. The method of claim 3, wherein the friction generator is prepared from a plant protein, and the method comprises the following steps: the protein powder specifically comprises: dispersing protein in an aqueous solution or an ethanol aqueous solution with the concentration of 70-90% to prepare a protein solution, wherein the mass fraction of the protein in the protein solution is 1-10%; then adding plasticizer with the mass of 10-60% of protein into the protein solution, heating and denaturing in water bath at 60-95 ℃, stirring for 30-60min, degassing for 10 min under vacuum, pouring into a mold, putting into an oven, and evaporating and drying at 30-70 ℃.