Degradable flexible piezoelectric sensor and preparation method thereof

Abstract

The invention relates to the technical field of sensing, in particular to a degradable flexible piezoelectric sensor and a preparation method thereof.The degradable flexible piezoelectric sensor comprises a first flexible electrode, a first biological bonding layer, a cellulose piezoelectric film, a second biological bonding layer and a second flexible electrode which are sequentially stacked; the first part is connected with the first biological bonding layer, and the second part is connected with a lead; the third part is connected with the second biological bonding layer, and the fourth part is connected with a lead; and the second part and the fourth part are arranged in a staggered manner. The biological bonding layer is mainly used for improving interface bonding between the cellulose piezoelectric film and the flexible electrode, the problem of a weak bonding interface caused by the fact that the outer surface of a raw material of the cellulose piezoelectric film is too smooth is effectively solved through the flexible electrode oxygen plasma treatment technology, and therefore excessive consumption of charges at the interface is avoided, and the service life of the cellulose piezoelectric film is prolonged. The migration and export of charges are accelerated, and finally the sensitivity and linearity of the sensor are improved.

Description

Technical Field

[0001] The present invention relates to the field of sensing technology, and in particular to a degradable flexible piezoelectric sensor and a preparation method thereof. Background Art

[0002] With the advancement of science and technology and social development, frequent human activities have generated a large amount of waste organisms, and their random discharge has seriously damaged the ecological environment, while also exacerbating the already sharp contradiction between limited resources and human needs. At present, most waste organisms are disposed of by landfill, incineration, natural decay and other means.

[0003] Flexible piezoelectric sensors are a type of tactile sensor that is extremely valuable in artificial intelligence systems such as wearable electronic devices, intelligent robots, human / machine interaction (iHMI), and human health measurement. Flexible piezoelectric sensors have the advantages of high natural frequency, high sensitivity, high signal-to-noise ratio, and good stability. Since the basic working principle of flexible piezoelectric sensors is the piezoelectric effect, they also have the characteristic of self-power supply, that is, they can convert the ubiquitous mechanical energy in daily life into electrical energy. This characteristic of flexible piezoelectric sensors can not only maintain their own operation, but also the excess electrical energy can be stored and utilized, that is, it can be used as a micro-power source, overcoming the major obstacle of additional power supply for wearable devices.

[0004] The piezoelectric effect of flexible piezoelectric sensors comes from the core material - flexible piezoelectric materials. Synthetic polyvinylidene fluoride (PVDF) (including derivatives PVDF-TrFE and PVDF-HFP) is currently the best flexible piezoelectric material. However, PVDF has obvious inherent defects, such as non-degradability and complex manufacturing process.

[0005] Therefore, how to ensure the performance of flexible piezoelectric sensors while reducing the difficulty of manufacturing and achieving biodegradability is a current research direction. Summary of the invention

[0006] (I) Purpose of the invention

[0007] The object of the present invention is to provide a degradable flexible piezoelectric sensor and a preparation method thereof which can achieve degradability while ensuring the performance of the flexible piezoelectric sensor and reducing the difficulty of manufacturing.

[0008] (II) Technical solution

[0009] In order to solve the above problems, the present invention provides a degradable flexible piezoelectric sensor, comprising:

[0010] a first flexible electrode, a first bioadhesive layer, a cellulose piezoelectric film, a second bioadhesive layer, and a second flexible electrode;

[0011] The first flexible electrode, the first bioadhesive layer, the cellulose piezoelectric film, the second bioadhesive layer and the second flexible electrode are stacked in sequence;

[0012] The sizes of the first flexible electrode and the second flexible electrode are larger than the sizes of the first bioadhesive layer, the cellulose piezoelectric film, and the second bioadhesive layer;

[0013] The first flexible electrode comprises a first conductive surface, wherein the first conductive surface comprises a first portion and a second portion;

[0014] The first portion is connected to the first bioadhesive layer, and the second portion is connected to a lead;

[0015] The second flexible electrode comprises a second conductive surface, and the second conductive surface comprises a third portion and a fourth portion;

[0016] The third portion is connected to the second bioadhesive layer, and the fourth portion is connected to the lead;

[0017] The second part and the fourth part are arranged in a staggered manner;

[0018] The raw materials of the first bioadhesive layer and the second bioadhesive layer are plants.

[0019] In another aspect of the present invention, preferably,

[0020] A method for preparing a degradable flexible piezoelectric sensor, the method being used to prepare the degradable flexible piezoelectric sensor as described above;

[0021] The preparation method comprises the following steps:

[0022] Step S1: cleaning, first cutting and hot pressing the raw material of the cellulose piezoelectric film to obtain the cellulose piezoelectric film;

[0023] Step S2: performing oxygen plasma treatment on the first conductive surface of the first flexible electrode and the second conductive surface of the second flexible electrode;

[0024] Step S3: performing a second cutting on the raw material of the first bioadhesive layer and placing the raw material on the first conductive surface, and performing a first heat treatment to obtain a first structure;

[0025] Performing a second cutting on the raw material of the second bioadhesive layer, and then arranging it on the second conductive surface, and performing a first heat treatment to obtain a second structure;

[0026] Step S4: stacking the first structure, the cellulose piezoelectric film and the second structure in sequence, performing a second heat treatment, connecting them with leads and then packaging them to obtain a degradable flexible piezoelectric sensor.

[0027] In another aspect of the present invention, preferably,

[0028] The raw material of the cellulose piezoelectric film in step S1 includes fruit peel;

[0029] The raw material of the bio-adhesive layer in step S3 includes the inner peel of melon.

[0030] In another aspect of the present invention, preferably,

[0031] The fruit includes at least one of grapes, green grapes, loquats and persimmons;

[0032] The melons include at least one of cucumber, wax gourd and Hami melon.

[0033] In another aspect of the present invention, preferably,

[0034] The cleaning in step S1 includes:

[0035] Use an ultrasonic cleaner to clean in water three times, each cleaning lasting 3-8 minutes;

[0036] The samples were cleaned in anhydrous ethanol three times using an ultrasonic cleaner, with each cleaning lasting 3-8 minutes.

[0037] In another aspect of the present invention, preferably,

[0038] The hot pressing pressure in step S1 is 1000-10000 Pa, the hot pressing temperature is 60-120° C., and the hot pressing time is 0.5-2 h.

[0039] In another aspect of the present invention, preferably,

[0040] The first cutting in step S1 includes cutting to a preset size, wherein the preset size includes a regular quadrilateral of 0.5-1 cm×0.5-1 cm or a circle of 0.5-1 cm in diameter;

[0041] The second cutting in step S3 includes cutting to a preset thickness, and the preset thickness includes 5-10 μm.

[0042] In another aspect of the present invention, preferably,

[0043] The flexible electrode includes one of a tin oxide flexible conductive film, a copper foil and an aluminum foil.

[0044] In another aspect of the present invention, preferably,

[0045] The temperature of the first heat treatment in the step S3 is 30-60° C., and the time of the first heat treatment is 1-12 hours.

[0046] In another aspect of the present invention, preferably,

[0047] The temperature of the second heat treatment in the step S4 is 30-60° C., and the time of the second heat treatment is 1-12 hours.

[0048] (III) Beneficial effects

[0049] The above technical solution of the present invention has the following beneficial technical effects:

[0050] The sensor of the present invention adopts a five-layer stacking structure, namely, it is composed of flexible electrode / bioadhesive layer / cellulose piezoelectric film / bioadhesive layer / flexible electrode. Among them, the cellulose piezoelectric film is the core functional material, which bears the piezoelectric effect; the bioadhesive layer mainly plays a role in improving the interface bonding between the cellulose piezoelectric film and the flexible electrode, and together with the flexible electrode oxygen plasma treatment technology, it effectively solves the problem of weak bonding interface caused by the overly smooth outer surface of the raw material of the cellulose piezoelectric film, thereby avoiding excessive consumption of charge at the interface, accelerating the migration and extraction of charge, and ultimately improving the sensitivity and linearity of the sensor.

[0051] The sensor of the present invention uses degradable waste exocarp as the raw material of the flexible piezoelectric material and is obtained by hot pressing technology. In a semi-enclosed environment of pressurization and heating, the exocarp undergoes structural adjustments that cannot be completed under normal conditions, which are mainly reflected in the more orderly arrangement of the cellulose layers inside the exocarp, the more orderly accumulation of the slender crystal fibers in the cellulose layers, and the increase in the number of asymmetric dipoles (hydroxyl groups (-OH), thereby greatly stimulating the piezoelectric effect of the cellulose piezoelectric film, and ultimately further improving the sensitivity, stability and linearity of the sensor.

[0052] The sensor of the present invention has the characteristics of being biodegradable, highly sensitive, highly flexible and self-powered. It can capture mechanical energy that can be found everywhere in daily life, convert it into electrical energy, and can be used as a micro-power source. The preparation process of the present invention uses conventional equipment, has a simple preparation process, and uses low-cost raw materials, which is suitable for large-scale production applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention;

[0054] Figure 2 is a macroscopic image of the cellulose piezoelectric film in Example 1 of the present invention;

[0055] Figure 3 is an XRD graph of the cellulose piezoelectric film in Example 1 of the present invention;

[0056] Figure 4 is a cross-sectional SEM morphology image of the cellulose piezoelectric film in Example 1 of the present invention;

[0057] Figure 5 is an output voltage-force curve diagram of the sensor in Example 1 of the present invention;

[0058] Figure 6 is an output voltage-time curve diagram when the sensor senses finger bending in Example 1 of the present invention;

[0059] Figure 7 is a voltage-time curve diagram of the sensor in Example 1 of the present invention charging a lithium-ion battery under repeated force;

[0060] Figure 8 This is the output voltage-force curve of the sensor of comparative example 1. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0062] The accompanying drawings show schematic diagrams of layer structures according to embodiments of the present invention. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clarity. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0063] Obviously, the described embodiments are only some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] In the description of the present invention, it should be noted that the terms “first” and “second” are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0065] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0066] The present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, the same elements are represented by similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0067] Example

[0068] A degradable flexible piezoelectric sensor. Figure 1 FIG. 1 shows a schematic diagram of the overall structure of an embodiment of the present invention. Figure 1 As shown, including:

[0069] A first flexible electrode 1, a first bioadhesive layer 2, a cellulose piezoelectric film 3, a second bioadhesive layer 4, and a second flexible electrode 5;

[0070] The first flexible electrode 1, the first bioadhesive layer 2, the cellulose piezoelectric film 3, the second bioadhesive layer 4 and the second flexible electrode 5 are stacked in sequence;

[0071] The sizes of the first flexible electrode 1 and the second flexible electrode 5 are larger than the sizes of the first bioadhesive layer 2, the cellulose piezoelectric film 3, and the second bioadhesive layer 4; when arranged, the first flexible electrode 1 may be aligned with the first bioadhesive layer 2 at one end and not aligned at the other end, or both ends may not be aligned, and the second flexible electrode 5 is arranged in the same manner as the first flexible electrode 1;

[0072] The first flexible electrode 1 comprises a first conductive surface 1-1, and the first conductive surface 1-1 comprises a first part 1-2 and a second part 1-3; the first part 1-2 is connected to the first bioadhesive layer 2, and the second part 1-3 is connected to a lead;

[0073] The second flexible electrode 5 includes a second conductive surface 5-1, and the second conductive surface includes a third part 5-2 and a fourth part 5-3; the third part 5-2 is connected to the second bioadhesive layer 4, and the fourth part 5-3 is connected to the lead wire;

[0074] The second part 1-3 and the fourth part 5-3 are arranged in a staggered manner;

[0075] The raw materials of the first bioadhesive layer 2 and the second bioadhesive layer 4 are plants.

[0076] The design that the first conductive surface 1-1 is divided into the first part 1-2 and the second part 1-3, and the second conductive surface 5-1 is divided into the third part 5-2 and the fourth part 5-3, makes the connection between the electrode and the bioadhesive layer and the lead wire more reasonable and orderly. The first part 1-2 and the third part 5-2 are closely connected to the bioadhesive layer, ensuring that when the piezoelectric film produces a piezoelectric effect, the charge can be efficiently conducted to the electrode; and the second part 1-3 and the fourth part 5-3 are used to connect the lead wires to smoothly export the electrical signal generated by the sensor for subsequent signal processing and analysis. The second part 1-3 and the fourth part 5-3 are staggered, which can effectively reduce the electromagnetic interference phenomenon that may be caused by the overly concentrated layout of the electrode lead wires, and improve the signal quality and stability of the sensor.

[0077] A method for preparing a degradable flexible piezoelectric sensor, the method being used to prepare the degradable flexible piezoelectric sensor as described above;

[0078] The preparation method comprises the following steps:

[0079] Step S1: cleaning, first cutting and hot pressing the raw material of the cellulose piezoelectric film to obtain the cellulose piezoelectric film;

[0080] The specific content of the raw materials of the cellulose piezoelectric film is not limited here. The raw materials of the cellulose piezoelectric film are plants. In the present embodiment, the raw materials of the cellulose piezoelectric film include fruit peels. The fruit peels are peeled off from the fruits, and then the residual pulp on the surface of the fruit peels is removed. The fruit peels are then cleaned and cut for the first time. After cutting to a preset size, the fruit peels are placed between clamps with smooth inner surfaces. The fruit peels are then placed together with the clamps in a drying oven for hot pressing to obtain a cellulose piezoelectric film.

[0081] In this embodiment, the fruit includes at least one of grapes, green grapes, loquats and persimmons;

[0082] Cleaning includes: first use an ultrasonic cleaner to clean in water three times, each time for 3-8 minutes; then use an ultrasonic cleaner to clean in anhydrous ethanol three times, each time for 3-8 minutes. After cleaning, the fruit skin presents a natural luster. The ultrasonic cleaner uses the vibration of high-frequency sound waves to generate a large number of tiny bubbles in the water. When these bubbles burst, they will produce strong shock waves, effectively removing dirt, impurities and residues on the surface of the fruit. Anhydrous ethanol has better disinfection and decontamination capabilities, which can further improve the cleaning effect.

[0083] The pressure of hot pressing is 1000-10000Pa, the temperature of hot pressing is 60-120℃, and the time of hot pressing is 0.5-2h. During hot pressing, the fruit peel is in a semi-enclosed environment of pressure and temperature, and structural adjustments that cannot be completed under normal conditions occur. The main manifestations are that the cellulose layers inside the outer peel are arranged more orderly, the elongated crystal fibers in the cellulose layers are stacked more orderly, and the number of asymmetric dipoles (hydroxyl groups (-OH)) is increased, which can greatly stimulate the piezoelectric effect of the cellulose piezoelectric film, and ultimately further improve the sensitivity, stability and linearity of the sensor.

[0084] The preset sizes include a regular quadrilateral of 0.5 to 1 cm × 0.5 to 1 cm or a circle of 0.5 to 1 cm in diameter; it can be applied to more scenarios and meet the requirements for sensor size.

[0085] Step S2: treating the first conductive surface of the first flexible electrode and the second conductive surface of the second flexible electrode with oxygen plasma; oxygen plasma can activate and modify the surface of the first conductive surface and the second conductive surface, increase their surface energy and roughness, so that the subsequent bioadhesive layer can be more firmly attached to the electrode surface, ensuring the integrity and stability of the sensor structure, and reducing the risk of performance failure due to delamination during use. In this embodiment, the flexible electrode includes one of tin oxide flexible conductive film, copper foil and aluminum foil;

[0086] Step S3: performing a second cutting on the raw material of the first bioadhesive layer and placing the raw material on the first conductive surface, and performing a first heat treatment to obtain a first structure;

[0087] Performing a second cutting on the raw material of the second bioadhesive layer, and then arranging it on the second conductive surface, and performing a first heat treatment to obtain a second structure;

[0088] The raw materials of the first bio-adhesive layer and the second bio-adhesive layer are plants, including the endocarp of melons, wherein the endocarp of melons specifically refers to the innermost layer of the melon peel, and the melons include at least one of cucumbers, wax gourds and Hami melons.

[0089] The second cutting includes cutting to a preset thickness, wherein the preset thickness includes 5 to 10 μm. The second cutting also includes cutting to the preset size, which is the same size as the shape and size of the cellulose piezoelectric film; the temperature of the first heat treatment is 30 to 60° C., and the time of the first heat treatment is 1 to 12 hours.

[0090] The inner peel of melons serves as a biological adhesive layer, which mainly improves the interface bonding between the cellulose piezoelectric membrane and the flexible electrode. Together with the flexible electrode oxygen plasma treatment technology, it effectively solves the problem of weak bonding interface caused by the overly smooth outer surface of the cellulose piezoelectric membrane raw material, thereby avoiding excessive consumption of charge at the interface, accelerating the migration and extraction of charges, and ultimately improving the sensitivity and linearity of the sensor.

[0091] Step S4: stacking the first structure, the cellulose piezoelectric film and the second structure in sequence, performing a second heat treatment, connecting them with leads and then packaging them to obtain a degradable flexible piezoelectric sensor.

[0092] The temperature of the second heat treatment in step S4 is 30-60°C, and the time of the second heat treatment is 1-12 hours. During assembly, the first bioadhesive layer of the first structure is placed upward; then the cellulose piezoelectric film is superimposed on the first bioadhesive layer, and the second bioadhesive layer of the first structure is placed downward, and staggered to cover the surface of the cellulose piezoelectric film, thereby obtaining a five-layer laminated structure consisting of a flexible electrode / bioadhesive layer / cellulose piezoelectric film / bioadhesive layer / flexible electrode; then the five-layer laminated structure is placed in a drying oven for a second heat treatment; finally, the five-layer laminated structure is taken out, and the parts of the flexible electrode larger than the bioadhesive layer are connected to the leads respectively, and the four sides of the five-layer laminated structure are packaged and fixed to obtain a degradable flexible piezoelectric sensor.

[0093] The first flexible electrode 1 and the second flexible electrode 5 of this embodiment are key parts for charge collection and transmission. Their conductive surfaces are closely connected to the corresponding bioadhesive layers, respectively, to ensure that the electrical signal can be efficiently transmitted between the piezoelectric film and the lead. When the sensor is subjected to external forces, such as mechanical deformations such as pressure, stretching or bending, the cellulose piezoelectric film 3 in the middle will produce charge polarization due to the piezoelectric effect, thereby forming a potential difference between the two electrodes, and then generating an electrical signal. The bioadhesive layer mainly plays a role in improving the interface bonding between the cellulose piezoelectric film and the flexible electrode. Together with the flexible electrode oxygen plasma treatment technology, it effectively solves the problem of weak bonding interface caused by the overly smooth outer surface of the raw material of the cellulose piezoelectric film, thereby avoiding excessive consumption of charge at the interface, accelerating the migration and extraction of charge, and ultimately improving the sensitivity and linearity of the sensor.

[0094] Example 1

[0095] The skin of the grapes was peeled off, and then the residual pulp on the inner surface of the skin was removed; the skin of the fruit was cleaned in water three times with an ultrasonic cleaner, each time for 5 minutes; the skin of the fruit was cleaned in anhydrous ethanol three times with an ultrasonic cleaner, each time for 5 minutes, and cut into a 1cm×1cm regular quadrilateral; the fruit was placed between clamps with smooth inner surfaces; the skin of the fruit and the clamps were then placed in a drying oven, under a pressure of 1000Pa and a temperature of 60°C for 2 hours; the skin of the fruit was finally taken out of the clamps to obtain a cellulose piezoelectric film. Figure 2 The macroscopic photograph of the cellulose piezoelectric film in Example 1 of the present invention is shown. Figure 2 As shown, the cellulose piezoelectric film of this embodiment has a high flatness.

[0096] Figure 3 The XRD curve of the cellulose piezoelectric film in Example 1 of the present invention is shown in FIG. Figure 3As shown, the diffraction peaks of the cellulose piezoelectric film of this embodiment at 2θ angles of about 16° and 22° correspond to the (101) and (002) crystal planes of cellulose, respectively, indicating that the grape peel contains orderly arranged cellulose.

[0097] Figure 4 The cross-sectional SEM morphology of the cellulose piezoelectric film in Example 1 of the present invention is shown in FIG. Figure 4 As shown, the cellulose layers inside the cellulose piezoelectric film of this embodiment are arranged in a very orderly manner and the layer thickness is less than 100 nm.

[0098] The first structure and the second structure were prepared according to the following steps: the conductive surface of ITO-PEN was treated with oxygen plasma; the endocarp of cucumber was sliced ​​into thin slices to obtain endocarp slices, which had the same size as the cellulose piezoelectric film and a thickness of 5 μm; the endocarp slices were then superimposed on the conductive surface of ITO-PEN, and finally kept warm at 30°C for 12 hours to obtain the first structure and the second structure.

[0099] The first bioadhesive layer of the first structure is placed upward; the cellulose piezoelectric film is then superimposed on the first bioadhesive layer, and the second bioadhesive layer of the second structure is placed downward and staggered on the surface of the cellulose piezoelectric film, thereby obtaining a five-layer structure consisting of ITO-PEN / bioadhesive layer / cellulose piezoelectric film / bioadhesive layer / ITO-PEN; the five-layer structure is then placed in a drying oven and kept warm at 30°C for 12 hours; finally, the five-layer structure is taken out, leads are connected to the part of the flexible electrode that is larger than the bioadhesive layer, and the four sides are encapsulated and fixed to obtain a degradable flexible piezoelectric sensor.

[0100] Figure 5 The output voltage-force curve of the sensor in Example 1 of the present invention is shown in FIG. Figure 5 As shown, the sensor of this embodiment realizes self-power supply, and its output voltage is proportional to the applied force and has high linearity. The corresponding linearity R 2 and sensitivity are 0.99 and 0.34V / N respectively.

[0101] Figure 6 FIG. 4 shows the output voltage-time curve of the sensor when sensing the bending of the finger in Example 1 of the present invention. Figure 6 As shown, the sensor of this embodiment is able to sense the subtle and regular changes caused by the bending of the finger, which also shows that the sensor has excellent flexibility.

[0102] Figure 7 FIG. 4 shows a voltage-time curve of the sensor in Example 1 of the present invention charging a lithium-ion battery under repeated force, as shown in FIG. Figure 6 As shown, the sensor of this embodiment can be used as a micro power source.

[0103] Example 2

[0104] The outer skin of the loquat is peeled off, and then the residual pulp on the inner surface of the outer skin of the fruit is removed; the outer skin of the fruit is cleaned in water three times using an ultrasonic cleaner, each cleaning time is 3 minutes; the outer skin of the fruit is cleaned in anhydrous ethanol three times using an ultrasonic cleaner, each cleaning time is 8 minutes, and it is cut into a regular quadrilateral of 0.5 cm×0.5 cm; it is placed between clamps with smooth inner surfaces; then the outer skin of the fruit and the clamps are placed in a drying oven together with a pressure of 10000Pa and a temperature of 120°C for 0.5 hours; finally, the outer skin of the fruit is taken out from the clamps to obtain a cellulose piezoelectric film.

[0105] The first structure and the second structure are prepared according to the following steps: the conductive surface of the copper foil is treated with oxygen plasma; the inner peel of the Hami melon is cut into thin slices to obtain inner peel slices, which have the same size as the cellulose piezoelectric film and are 10 μm thick; the inner peel slices are then superimposed on the conductive surface of the copper foil, and finally the first structure and the second structure are obtained by heat preservation at 60°C for 1 hour.

[0106] The first bioadhesive layer of the first structure is placed upward; the cellulose piezoelectric film is then superimposed on the first bioadhesive layer, and the second bioadhesive layer of the second structure is placed downward and staggered on the surface of the cellulose piezoelectric film, thereby obtaining a five-layer structure consisting of copper foil / bioadhesive layer / cellulose piezoelectric film / bioadhesive layer / copper foil; the five-layer structure is then placed in a drying oven and kept warm at 60°C for 1 hour; finally, the five-layer structure is taken out, leads are connected to the part of the flexible electrode that is larger than the bioadhesive layer, and the four sides are encapsulated and fixed to obtain a degradable flexible piezoelectric sensor.

[0107] Example 3

[0108] The outer skin of the persimmon was peeled off, and then the residual pulp on the inner surface of the outer skin of the fruit was removed; the outer skin of the fruit was cleaned in water three times using an ultrasonic cleaner, each cleaning time was 8 minutes; the outer skin of the fruit was cleaned in anhydrous ethanol three times using an ultrasonic cleaner, each cleaning time was 3 minutes, and it was cut into a circle with a diameter of 1 cm; it was placed between clamps with smooth inner surfaces; then the outer skin of the fruit and the clamps were placed in a drying oven together with a pressure of 5000Pa and a temperature of 80°C for 1 hour; finally, the outer skin of the fruit was taken out from the clamps to obtain a cellulose piezoelectric film.

[0109] The first structure and the second structure are prepared according to the following steps: the conductive surface of the aluminum foil is treated with oxygen plasma; the inner peel of the wax gourd is cut into thin slices to obtain inner peel slices, which have the same size as the cellulose piezoelectric film and are 8 μm thick; the inner peel slices are then superimposed on the conductive surface of the aluminum foil, and finally the first structure and the second structure are obtained by heat preservation at 50°C for 6 hours.

[0110] The first bioadhesive layer of the first structure is placed upward; the cellulose piezoelectric film is then superimposed on the first bioadhesive layer, and the second bioadhesive layer of the second structure is placed downward and staggered to cover the surface of the cellulose piezoelectric film, thereby obtaining a five-layer structure consisting of aluminum foil / bioadhesive layer / cellulose piezoelectric film / bioadhesive layer / aluminum foil; the five-layer structure is then placed in a drying oven and kept warm at 50°C for 7 hours; finally, the five-layer structure is taken out, the leads are connected to the part of the flexible electrode that is larger than the bioadhesive layer, and the package is fixed all around to obtain a degradable flexible piezoelectric sensor.

[0111] Comparative Example 1

[0112] The rest is the same as Example 1, except that: the flexible piezoelectric sensor has no bioadhesive layer, and is only a three-layer stacked structure consisting of ITO-PEN / cellulose piezoelectric film / ITO-PEN, and the cellulose piezoelectric film is not subjected to heat pressing treatment, and the conductive surface of ITO-PEN is not subjected to oxygen plasma treatment. The specific preparation method is as follows:

[0113] Preparation of cellulose piezoelectric film; peeling the outer peel from the grape; then removing the residual pulp on the inner surface of the outer peel; then washing the outer peel with an ethanol-water solution with a weight ratio of 1:1, and cutting it into a 1cm×1cm regular quadrilateral; finally keeping it at 60°C for 2h to obtain a cellulose piezoelectric film;

[0114] Assembly of the sensor: Place the conductive surface of ITO-PEN upwards; then superimpose the cellulose piezoelectric film on the conductive surface of ITO-PEN, and place the conductive surface of another ITO-PEN downwards and staggeredly cover the surface of the cellulose piezoelectric film, thereby obtaining a three-layer stacked structure consisting of ITO-PEN / cellulose piezoelectric film / ITO-PEN; then place the three-layer stacked structure in a drying oven and keep it warm at 30°C for 12 hours; finally take out the three-layer stacked structure, connect the uncovered parts of the two electrodes with leads, and package and fix them all around to obtain a degradable flexible piezoelectric sensor.

[0115] Figure 8 is the output voltage-force curve of the sensor in comparative example 1 of the present invention, from which it can be known that the linearity R of the sensor 2 The sensitivity and linearity of the sensor in Example 1 are higher than those in Comparative Example 1.

[0116] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

[0117] In the above description, the technical details of patterning and etching of each layer are not described in detail. However, those skilled in the art should understand that various means in the prior art can be used to form layers, regions, etc. of desired shapes. In addition, in order to form the same structure, those skilled in the art can also design methods that are not completely the same as the methods described above.

[0118] The present invention has been described above with reference to the embodiments of the present invention. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents. Without departing from the scope of the present invention, a person skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

[0119] Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.

[0120] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A degradable flexible piezoelectric sensor, characterized in that: include: A first flexible electrode (1), a first bioadhesive layer (2), a cellulose piezoelectric film (3), a second bioadhesive layer (4) and a second flexible electrode (5); The first flexible electrode (1), the first bioadhesive layer (2), the cellulose piezoelectric film (3), the second bioadhesive layer (4) and the second flexible electrode (5) are stacked in sequence; The sizes of the first flexible electrode (1) and the second flexible electrode (5) are larger than the sizes of the first bioadhesive layer (2), the cellulose piezoelectric film (3) and the second bioadhesive layer (4); The first flexible electrode (1) comprises a first conductive surface (1-1), and the first conductive surface (1-1) comprises a first part (1-2) and a second part (1-3); The first part (1-2) is connected to the first bioadhesive layer (2), and the second part (1-3) is connected to the lead; The second flexible electrode (5) comprises a second conductive surface (5-1), and the second conductive surface comprises a third part (5-2) and a fourth part (5-3); The third part (5-2) is connected to the second bioadhesive layer (4), and the fourth part (5-3) is connected to the lead; The second part (1-3) and the fourth part (5-3) are arranged in a staggered manner; The raw materials of the first bioadhesive layer (2) and the second bioadhesive layer (4) are plants.

2. A method for preparing a degradable flexible piezoelectric sensor, characterized in that: The degradable flexible piezoelectric sensor is the degradable flexible piezoelectric sensor according to claim 1; the preparation method comprises the following steps: Step S1: cleaning, first cutting and hot pressing the raw material of the cellulose piezoelectric film to obtain the cellulose piezoelectric film; Step S2: performing oxygen plasma treatment on the first conductive surface of the first flexible electrode and the second conductive surface of the second flexible electrode; Step S3: After performing a second cutting on the raw material of the first bioadhesive layer, the raw material is placed on the first conductive surface and subjected to a first heat treatment to obtain a first structure; Performing a second cutting on the raw material of the second bioadhesive layer, and then arranging it on the second conductive surface, and performing a first heat treatment to obtain a second structure; Step S4: stacking the first structure, the cellulose piezoelectric film and the second structure in sequence, performing a second heat treatment, connecting them with leads and then packaging them to obtain a degradable flexible piezoelectric sensor.

3. The preparation method according to claim 2, characterized in that: The raw material of the cellulose piezoelectric film in step S1 includes fruit peel; The raw material of the bio-adhesive layer in step S3 includes the inner peel of melon.

4. The preparation method according to claim 3, characterized in that: The fruit includes at least one of grapes, green grapes, loquats and persimmons; The melons include at least one of cucumber, wax gourd and Hami melon.

5. The preparation method according to claim 2, characterized in that: The cleaning in step S1 includes: Use an ultrasonic cleaner to clean in water three times, each cleaning lasting 3-8 minutes; The samples were cleaned in anhydrous ethanol three times using an ultrasonic cleaner, with each cleaning lasting 3-8 minutes.

6. The preparation method according to claim 2, characterized in that: The hot pressing pressure in step S1 is 1000-10000 Pa, the hot pressing temperature is 60-120° C., and the hot pressing time is 0.5-2 h.

7. The preparation method according to claim 2, characterized in that: The first cutting in step S1 includes cutting to a preset size, wherein the preset size includes a regular quadrilateral of 0.5-1 cm×0.5-1 cm or a circle of 0.5-1 cm in diameter; The second cutting in step S3 includes cutting to a preset thickness, and the preset thickness includes 5-10 μm.

8. The preparation method according to claim 2, characterized in that: The flexible electrode includes one of a tin oxide flexible conductive film, a copper foil and an aluminum foil.

9. The preparation method according to claim 2, characterized in that: The temperature of the first heat treatment in the step S3 is 30-60° C., and the time of the first heat treatment is 1-12 hours.

10. The preparation method according to claim 2, characterized in that: The temperature of the second heat treatment in the step S4 is 30-60° C., and the time of the second heat treatment is 1-12 hours.

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