CN110809338B - Preparation method and product of shape-adaptive quick-response soft heater - Google Patents

Preparation method and product of shape-adaptive quick-response soft heater Download PDF

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CN110809338B
CN110809338B CN201910950261.2A CN201910950261A CN110809338B CN 110809338 B CN110809338 B CN 110809338B CN 201910950261 A CN201910950261 A CN 201910950261A CN 110809338 B CN110809338 B CN 110809338B
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layer
polyvinyl alcohol
soft heater
conductive
sacrificial layer
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CN110809338A (en
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吴豪
姜珊
胡一佳
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
    • H05B3/34—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater flexible, e.g. heating nets or webs
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/02—Details
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
    • H05K3/12—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using thick film techniques, e.g. printing techniques to apply the conductive material or similar techniques for applying conductive paste or ink patterns
    • H05K3/1216—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using thick film techniques, e.g. printing techniques to apply the conductive material or similar techniques for applying conductive paste or ink patterns by screen printing or stencil printing
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
    • H05K3/12—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using thick film techniques, e.g. printing techniques to apply the conductive material or similar techniques for applying conductive paste or ink patterns
    • H05K3/1283—After-treatment of the printed patterns, e.g. sintering or curing methods

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  • Manufacturing & Machinery (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Surface Heating Bodies (AREA)

Abstract

The invention belongs to the field of flexible electronic devices, and particularly discloses a preparation method and a product of a shape-adaptive fast-response soft heater. The method comprises the following steps: (1) spin-coating a polyvinyl alcohol aqueous solution on a hard substrate, and heating to solidify the polyvinyl alcohol aqueous solution to form a sacrificial layer; (2) processing the conductive material into a conductive layer by utilizing screen printing; (3) spin-coating a flexible high polymer on the sacrificial layer, and heating to solidify the flexible high polymer; (4) dissolving the sacrificial layer to strip the hard substrate; (6) and adhering copper foil and an insulating layer on the primary body of the soft heater. The product is prepared by the method. The soft heater has the advantages of high response speed, small required driving voltage, large shape, good shape adaptability and capability of reliably grabbing and heating objects with complex shapes; meanwhile, the soft heater has good thermal stability at high temperature, and the performance of the soft heater can be adjusted by simply controlling the direct-current voltage of the power supply.

Description

Preparation method and product of shape-adaptive quick-response soft heater
Technical Field
The invention belongs to the field of flexible electronic devices, and particularly relates to a preparation method and a product of a shape-adaptive fast-response soft heater.
Background
The flexible actuator can convert external stimuli such as heat, light and the like to realize self mechanical deformation, and has great application prospect in the fields of artificial muscles, bionic robots and the like. Among various types of actuators, an electric actuator is relatively simple in structure and easy to control. Among them, electroactive polymer actuators have been widely studied due to their light weight, large deformation, flexibility and low cost. However, most electroactive polymer actuators require a high driving voltage or an electrolyte environment, and thus their applications in various fields are severely limited.
Unlike electroactive polymer actuators, electrothermal actuators based on differences in thermal expansion of materials can achieve large deformations at low drive voltages, while the structure of the electrolyte-free device enables flexible and complex movements in different environments. Many electrothermal actuators based on metal nanowire graphene have excellent performance and have achieved some applications, but they still cannot meet the requirements of high-performance actuators of low actuation voltage, low cost and large deformation due to the relatively high resistance of carbon nanomaterials and the complicated manufacturing process. More importantly, these actuators can only perform simple deformations such as bending and twisting, etc., and therefore their function is rather limited. Meanwhile, flexible and stretchable heaters are highly required for wearable electronic products (e.g., thermal therapy), and thus, there have been many researchers working on developing flexible heaters. However, these heaters cannot perform large deformation and heat a three-dimensionally curved object, and thus are difficult to be practically used.
In view of the above, there is a need in the advanced hyperthermia, food processing and processing industries to develop a flexible actuating heater with low driving voltage, short response time, large deformation, low cost and multiple functions.
Disclosure of Invention
In view of the above defects or improvement needs of the prior art, the present invention provides a method for manufacturing a shape-adaptive fast response soft heater and a product thereof, wherein the characteristics and process characteristics of the soft heater are combined, and a sacrificial layer process and a printing process are correspondingly combined, such that a conductive layer with a rough surface formed by printing can be better adhered to a flexible high polymer material, and is not easy to fall off. Meanwhile, the invention is based on the difference of thermal expansion of materials, has no complex electrolytic structure, has excellent conductivity of the functional layer, can realize large deformation only by a small amount of energy, has good thermal stability at high temperature, and can adjust the performance of the soft heater by simply controlling the direct current voltage of a power supply. Therefore, the utility model is especially suitable for the industries of high-grade heat treatment, food processing and the like.
To achieve the above object, according to one aspect of the present invention, there is provided a method for manufacturing a shape-adaptive fast response soft heater, comprising the steps of:
s1, preparing a sacrificial layer solidified by polyvinyl alcohol aqueous solution on the hard substrate;
s2, printing a pasty conductive material with a specified shape on the surface of the sacrificial layer prepared in the step S1, and then heating to cure the pasty conductive material with the specified shape, so that a conductive functional layer with a specified shape is prepared;
s3 spin-coating a flexible high polymer material on the surfaces of the sacrificial layer and the conductive function layer to uniformly coat the conductive function layer, then heating the flexible high polymer material to solidify the flexible high polymer material so as to obtain a flexible substrate coating the conductive function layer, wherein the hard substrate, the sacrificial layer, the conductive function layer and the flexible substrate form a soft heater matrix;
s4, cutting the soft heater matrix according to the shape of the conductive function layer, then putting the cut soft heater matrix into deionized water and heating to completely dissolve the sacrificial layer so as to peel off the hard substrate, thereby obtaining a soft heater primary body formed by the conductive function layer and the flexible substrate;
s5, connecting the two ends of the conductive function layer and the copper foil which form the primary body of the soft heater to an external power supply through silver paste, and carrying out insulation treatment on one side of the conductive function layer far away from the flexible substrate, thereby preparing the soft heater with the self-adaptive shape.
Further, in step S1, the polyvinyl alcohol aqueous solution is prepared from polyvinyl alcohol powder and a dispersing agent, wherein the mass fraction of the polyvinyl alcohol is 8% to 12%, the mass fraction of the dispersing agent is 0.5% to 2%, and the dispersing agent is sodium dodecyl benzene sulfonate or sodium dodecyl sulfate; further, the preparation method of the polyvinyl alcohol aqueous solution comprises the following steps: adding polyvinyl alcohol powder and a dispersing agent into deionized water, and stirring for 4-6 h at the temperature of 60-80 ℃.
Further, step S1 specifically includes the following steps:
s11, sequentially cleaning the hard substrate by using acetone, isopropanol and deionized water, and then blowing the hard substrate by using nitrogen;
s12, spin-coating the polyvinyl alcohol aqueous solution on the upper surface of the hard substrate processed in the step S11, and heating the polyvinyl alcohol aqueous solution to solidify into a film so as to form the sacrificial layer, wherein the spin-coating speed of the polyvinyl alcohol aqueous solution is 300-1000 rpm, the spin-coating time is 2-5 min, the heating temperature is 60-120 ℃, and the solidification time is 15-30 min, so that the sacrificial layer with a smooth surface and close adhesion to the hard substrate is obtained.
Further, in step S2, printing a paste-like conductive material with a specified shape on the surface of the sacrificial layer prepared in step S1 specifically includes the following steps: and uniformly coating the pasty conductive material on the screen printing plate and covering the hollow patterns on the screen printing plate, and scraping the surface of the screen printing plate, so that the pasty conductive material coated on the screen printing plate is printed on the sacrificial layer after penetrating through the hollow patterns on the screen printing plate.
Further, in step S2, the paste-like conductive material has a viscosity of 10Pa · S to 100Pa · S and a curing temperature of less than 160 ℃.
Further, the thickness of the conductive function layer is 20-50 μm, and further the thickness of the conductive function layer is 30-40 μm; further, the thickness of the conductive functional layer is 35 μm.
Further, in step S5, a polyimide tape is attached to a side of the conductive functional layer away from the flexible substrate to obtain an insulating layer for insulating the conductive functional layer; further, the thickness of the insulating layer is 40-80 μm; further, the thickness of the insulating layer is 60-70 μm; further, the thickness of the insulating layer is 65 μm.
Further, the flexible high polymer material is polydimethylsiloxane, copolyester or platinum-catalyzed silicone rubber.
According to another aspect of the present invention, there is provided a shape-adaptive fast response soft heater manufactured by the above manufacturing method.
Further, the conductive function layer is in a U shape or an array formed by connecting a plurality of U shapes.
Generally, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:
1) the invention combines the sacrificial layer process and the printing process, so that the conductive layer with a rough surface formed by printing can be better adhered to the flexible high polymer material and is not easy to fall off. Meanwhile, the invention is based on the difference of thermal expansion of materials, has no complex electrolytic structure, has excellent conductivity of the functional layer, can realize large deformation only by a small amount of energy, has good thermal stability at high temperature, and can adjust the performance of the soft heater by simply controlling the direct current voltage of a power supply.
2) The soft heater based on the thermal expansion difference of the materials does not have a complex electrolytic structure, the conductivity of the functional layer is excellent, and large deformation can be realized only by a small amount of energy, so that the driving voltage can be limited to a very low range (below 2V).
3) According to the preparation method, the preparation process parameters and the thickness of each layer are accurately controlled, so that the prepared soft heater is high in response speed, good in conductivity of the functional layer and low in resistance, can generate high heat under the same voltage, is high in speed, and the deformation curvature of the soft heater can quickly reach 1.31cm within 6s-1。
4) Under the condition of large deformation, the soft heater obtained by the preparation method has excellent electrical conductivity and stretchability as the conductive material of the functional layer and the two supporting layers have obvious thermal expansion difference during heating, so that the soft heater has a deformation angle of more than 860 degrees and a 4.0cm-1(2V drive voltage).
5) The soft heater obtained by the preparation method can realize grabbing and heating of objects with complex curved surfaces, and through tests, the excellent flexibility of the soft heater ensures the adaptability to objects with different shapes, so that more flexible and various functions can be realized. The heater also functions as a stable heat source at 200 ℃ on start-up, when its energy efficiency is 7.44%.
6) The invention can adjust the performance of the soft heater by simply controlling the direct current voltage of the power supply. The functional layer can rapidly convert more electrical energy to thermal energy when voltage or power is increased, thereby allowing the soft heater to heat up to a higher temperature, and a higher applied voltage will result in a greater curvature and also a shorter deformation response time.
7) The heater prepared by the method has good thermal stability under high-temperature conditions, different layers have the same polymer matrix, and the problem of delamination in the deformation process can be effectively prevented. Meanwhile, during bending, deformation and temperature increase do not significantly affect the resistance of the heater. The soft heater is thus able to provide a controlled and stable temperature.
8) The invention has simple and easy operation process, low production cost, easy batch processing and repeated use.
9) The materials adopted in the preparation method of the invention, such as polydimethylsiloxane, polyvinyl alcohol and the like, are nontoxic and harmless, thereby not only avoiding the pollution to the environment, but also ensuring the safety of production personnel and users.
Drawings
Fig. 1 (a) - (i) are flow charts of a method for manufacturing a shape-adaptive fast response soft heater according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of the U-shaped conductive layer involved in a shape adaptive fast response soft heater prepared in example 1 of the present invention;
fig. 3 is a schematic diagram of the shape of the parallelogram conductive layer involved in a shape-adaptive fast response soft heater prepared in example 1 of the present invention.
The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein: 1-hard substrate, 2-sacrificial layer, 3-conductive material layer, 4-conductive layer, 5-flexible substrate, 6-soft heater matrix, 7-copper foil and 8-insulating layer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The soft heater provided by the invention is divided into three layers, including a flexible substrate, a conductive layer and an insulating layer, which can be divided into the conductive layer and a deformation layer according to functions. The conductive layer is a mixture of a conductive substance and a flexible material, has excellent conductivity and stretchability, and functions to achieve a high heating temperature and large deformation when a low direct current is applied. The deformation layer comprises a flexible substrate and an insulating layer, and has large difference of thermal expansion coefficients, good flexibility and good insulation property in a wide temperature range so as to ensure stable operation of the functional layer. All three materials are flexible materials with large deformation, so that the soft heater can grasp and heat an object with a complex three-dimensional surface and can be in close contact for effective heating. The invention is a soft heater that can achieve gripping and heating of objects having complex three-dimensional surfaces. Moreover, the soft heater prepared by the invention is light and thin, the whole thickness can reach below 235 microns, and the soft heater can be widely applied to industries of high-grade heat treatment, food processing and the like in consideration of easy manufacture and controllable deformation and heating capacity.
Referring to (a) to (i) of fig. 1, the present invention provides a method for manufacturing a shape-adaptive fast response soft heater, comprising the steps of:
(1) as shown in fig. 1 (a), the hard substrate 1 is washed with acetone, isopropyl alcohol, and deionized water in this order, and then blown dry with nitrogen. Preferably, the hard substrate 1 is a monocrystalline silicon wafer, a polycrystalline silicon wafer, an epitaxial wafer, a quartz wafer or a glass wafer, and the surface is flat and smooth.
(2) As shown in fig. 1 (b), a sacrificial layer 2 cured from an aqueous solution of polyvinyl alcohol is prepared on a hard substrate 1. Specifically, an aqueous polyvinyl alcohol solution is first prepared, then the aqueous polyvinyl alcohol solution is spin-coated on the hard substrate 1, and then heated to cure the aqueous polyvinyl alcohol solution on the hard substrate 1 into a film, and the cured film forms the sacrificial layer 2. More specifically, a polyvinyl alcohol aqueous solution is spin-coated on the upper surface of a hard substrate 1 and is heated to be cured into a film, so as to form the sacrificial layer 2, wherein the spin-coating speed of the polyvinyl alcohol aqueous solution is 300-1000 rpm, the spin-coating time is 2-5 min, the heating temperature is 60-120 ℃, and the curing time is 15-30 min, so that the sacrificial layer 2 with a smooth surface and close adhesion to the hard substrate 1 is obtained.
The polyvinyl alcohol aqueous solution is prepared from polyvinyl alcohol powder and a dispersing agent, wherein the mass fraction of the polyvinyl alcohol is 8-12%, the mass fraction of the dispersing agent is 0.5-2%, and the dispersing agent is sodium dodecyl benzene sulfonate or sodium dodecyl sulfate; further, the preparation method of the polyvinyl alcohol aqueous solution comprises the following steps: adding polyvinyl alcohol powder and a dispersing agent into deionized water, stirring for 4-6 h at the temperature of 60-80 ℃, and standing the solution at room temperature for later use after the polyvinyl alcohol is completely dissolved. The thickness of the polyvinyl alcohol sacrificial layer 2 is 10-50 μm, and further, the thickness of the polyvinyl alcohol sacrificial layer 2 is 20-40 μm; the resulting polyvinyl alcohol sacrificial layer 2 had a thickness of 30 μm.
(3) As shown in fig. 1 (c), a paste-like conductive material of a prescribed shape is printed on the surface of the sacrificial layer 2, and then heated to cure the paste-like conductive material of a prescribed shape, thereby preparing a conductive functional layer 3 of a prescribed shape. Specifically, the hard substrate 1 was fixed on a stage of a screen printing machine, with the surface coated with the sacrificial layer 2 facing upward, and a screen plate made of polyester was mounted thereon, and the mesh number of the screen plate was 200 mesh, 300 mesh or 420 mesh. A conductive material in paste form is uniformly coated on the screen, covered with a pattern, and the surface of the screen is doctor-coated with a doctor blade so that the conductive material is printed on the sacrificial layer 2 through the screen as shown in (c) of fig. 1, to form a patterned conductive layer 4, which is then cured by heating as shown in (d) of fig. 1. Preferably, the object stage of the screen printing machine is controlled by a two-dimensional moving platform, the position of the object stage is adjusted in the horizontal plane, the object stage fixes the hard substrate in a vacuum adsorption mode, the vertical height of the mounting frame of the screen printing plate is adjustable, and the distance between the screen printing plate and the hard substrate is 5-10 mm. This spacing ensures that the printed material does not rebound onto the screen, while ensuring pattern integrity and definition.
In order to obtain a heater with more excellent flexibility and a wide heating range, the viscosity of the pasty conductive material is between 10Pa & s and 100Pa & s; further, the viscosity of the paste-like conductive material is 30 to 80 pas, and further, the viscosity of the paste-like conductive material is 70 pas. The conductivity of the paste-like conductive material is greater than 1 x 105And (5) S/m. Preferably, the curing temperature is 160 ℃ to ensure that the sacrificial polyvinyl alcohol layer is not damaged during heating. The thickness of the conductive functional layer 3 is 20-50 μm, and further the thickness of the conductive functional layer 3 is 30-40 μm; further, the thickness of the conductive functional layer 3 is 35 μm. Because the soft heater is greatly deformed, the conductive material of the functional layer has excellent conductivity and stretchability, and meanwhile, the two supporting layers have obvious thermal expansion difference when being heated, so that the soft heater has a deformation angle larger than 860 degrees and a 4.0cm-1(2V drive voltage).
Further, in the present invention, the thickness and shape of the conductive functional layer 3 are specifically set to obtain excellent conductivity and stretchability to accommodate the characteristic that the soft heater deforms greatly. The conductive functional layer 3 may be a single U-shaped structure, or may be a plurality of U-shaped structures arranged in an array, which may be adaptively adjusted according to the shape of the soft heater.
(4) As shown in (e) of fig. 1, spin-coating a flexible high polymer material on the surfaces of the sacrificial layer 2 and the conductive functional layer 3 to uniformly coat the conductive functional layer 3, and then heating and curing the flexible high polymer material to obtain the flexible substrate 5 coating the conductive functional layer 3, where the hard substrate 1, the sacrificial layer 2, the conductive functional layer 3, and the flexible substrate 5 together form a soft heater matrix, as shown in (f) of fig. 1. The flexible high polymer material is polydimethylsiloxane, copolyester or platinum catalytic silicone rubber. The thickness of the flexible substrate 5 is 100-150 μm; preferably, the thickness of the flexible substrate 5 is 140 μm. The spin coating speed, the spin coating time, the curing temperature and the curing time of the flexible high polymer material need to be adjusted according to the type of the material.
(5) As shown in fig. 1 (g), the soft heater base body is cut according to the shape of the conductive functional layer 3, and then the cut soft heater base body is put into deionized water and heated, so that the sacrificial layer 2 is completely dissolved to peel off the hard substrate 1, thereby obtaining a soft heater primary body jointly composed of the conductive functional layer 3 and the flexible substrate 5. Specifically, after cutting off an excess of the flexible substrate, the cut soft heater base body is put into deionized water and heated so that the polyvinyl alcohol sacrificial layer 2 is completely dissolved, thereby releasing the heater base body from the hard substrate 1, as shown in fig. 1 (g). Preferably, the heating temperature for dissolving the sacrificial layer 2 is 60 ℃ to 90 ℃, and the dissolving time is 6h to 10 h.
(6) As shown in (h) and (i) of fig. 1, both ends of the conductive functional layer 3 constituting the primary body of the soft heater and the copper foil are connected to an external power source through a silver paste, and the side of the conductive functional layer 3 away from the flexible substrate 5 is subjected to an insulation treatment, thereby preparing a shape-adaptive soft heater. Adhering a polyimide tape to one side of the conductive functional layer 3, which is far away from the flexible substrate 5, so as to obtain an insulating layer 8 for insulating the conductive functional layer 3; further, the thickness of the insulating layer 8 is 40 to 80 μm; further, the thickness of the insulating layer 8 is 60 μm to 70 μm; further, the thickness of the insulating layer 8 is 65 μm.
According to another aspect of the present invention, there is also provided a shape-adaptive fast response soft heater manufactured according to the manufacturing method as described above. The soft heater is of a multilayer film structure and comprises an insulating layer 8, a conductive layer 4 and a flexible substrate 5 which are sequentially connected, wherein the conductive layer 4 is coated by the insulating layer 8 and the flexible substrate 5, so that the large deformation of the conductive layer 4 under low driving voltage is realized by utilizing the larger thermal expansion difference of the insulating layer 8 and the flexible substrate 5; further, both ends of the conductive layer 4 and the copper foil are connected to an external power source through silver paste. Further, the conductive functional layer 3 is a U-shaped or a plurality of U-shaped connected arrays.
The preparation process of the invention mainly adopts an improved silk-screen printing process. This process is used to prepare a soft robot patterned conductive layer 4. In order to improve the printing quality, the improved method adopted by the invention is to coat the paste-shaped conductive material on the screen in advance so as to completely cover the pattern. The material is so viscous that it does not penetrate down through the screen but remains on the screen. At the moment, a scraper is adopted to scrape the screen printing plate, and the conductive material is uniformly coated on the substrate below the screen printing plate under the action of external pressure.
The preparation method provided by the invention uses a sacrificial layer process. The conductive material is not directly printed on the flexible substrate 5, but is printed on the sacrificial layer 2, and then the flexible polymer is spin-coated on the conductive material, and is heated and cured to form the flexible substrate 5. Therefore, the conducting layer 4 is completely coated by the flexible high polymer in a liquid state, the surface of the conducting layer 4 formed by silk-screen printing is rough, and the flexible high polymer and the conducting layer have strong adhesion force when being cured, so that the flexible high polymer is not easy to fall off.
In the present invention, the expansion coefficient of the material for producing the flexible substrate 5 is different from that of the material for producing the insulating layer.
The following will be made for more clear explanation of the preparation process and the design of the key process parameters thereof in conjunction with some specific examples.
As a premise of each example, it is first necessary to prepare an aqueous polyvinyl alcohol solution, and three ways are provided here. The first scheme is as follows: adding polyvinyl alcohol powder and a dispersing agent into deionized water, wherein the mass fraction of the polyvinyl alcohol powder is 8%, the mass fraction of the dispersing agent is 0.5%, heating and stirring are carried out at the heating temperature of 60 ℃, and the stirring time is 6 hours; after the polyvinyl alcohol is completely dissolved, the solution is kept stand at room temperature for later use. Scheme II: adding polyvinyl alcohol powder and a dispersing agent into deionized water, wherein the mass fraction of the polyvinyl alcohol powder is 10%, the mass fraction of the dispersing agent is 2%, heating and stirring are carried out at the heating temperature of 70 ℃, and the stirring time is 5.5 hours; after the polyvinyl alcohol is completely dissolved, the solution is kept stand at room temperature for later use.
Example 1
a. And the hard substrate 1 is a 4-inch monocrystalline silicon wafer, the polished surface of the hard substrate is cleaned by sequentially adopting acetone, isopropanol and deionized water and is dried by using nitrogen, and then the 10% concentration polyvinyl alcohol aqueous solution prepared by the second scheme is spin-coated on the hard substrate. And then, heating the silicon wafer on a hot plate at the temperature of 80 ℃ for 15 minutes to evaporate water by heating, and curing the polyvinyl alcohol to form a film to finish the preparation of the sacrificial layer 2.
b. The rigid substrate 1 was placed on the stage of a manual screen printing machine with the screen parallel to the rigid substrate 2 and held at a 5 mm spacing. The screen is patterned as shown in fig. 2, i.e. U-shaped, after which the hard substrate 1 is heated to cure the conductive material 3, forming a patterned conductive layer 4. The conductive layer 4 has a thickness of 35 microns.
c. Polydimethylsiloxane is spin-coated on the sacrificial layer 2 as a flexible substrate 5 of the shape-adaptive fast response soft heater at a spin-coating speed of 500 rpm for 3 minutes to coat the patterned conductive functional layer 4, and then the substrate is heated to be cured. The curing temperature was 80 ℃ and the curing time was 1 hour. The flexible substrate 5 has a thickness of 140 μm under this condition.
d. And (3) putting the sample into deionized water, heating at 90 ℃ for 7 hours, and stripping the soft heater matrix from the hard substrate 1 after the polyvinyl alcohol sacrificial layer 2 is completely dissolved.
e. And adhering a copper foil 7 and a polyimide adhesive tape 8 to the primary soft heater body obtained after stripping, wherein the thickness of the polyimide adhesive tape 8 is 60 microns.
To this end, a U-shaped form adaptive fast response soft heater is prepared as shown in fig. 2.
The overall thickness of the soft heater obtained in this example is the sum of the thicknesses of the three layers, i.e., 235 microns.
Example 2
a. The selection of the hard substrate 1 and the preparation of the sacrificial layer 2 are the same as in example 1.
b. The rigid substrate 1 was placed on the stage of a manual screen printing machine with the screen parallel to the rigid substrate 2 and held at a spacing of 8 mm. The screen takes the pattern shown in fig. 3, i.e. a parallelogram, after which the hard substrate 1 is heated to cure the conductive material 3, forming a patterned conductive layer 4. The conductive layer 4 has a thickness of 25 micrometers.
c. Polydimethylsiloxane was spin-coated on the sacrificial layer 2 as the flexible substrate 5 of this shape-adaptive fast response soft heater at a spin speed of 800 rpm for 3 minutes to coat the patterned conductive layer 4, followed by heating to cure it. The curing temperature was 80 ℃ and the curing time was 1 hour. The flexible substrate 5 has a thickness of 135 micrometers under this condition.
d. And (3) putting the sample into deionized water, heating at 80 ℃ for 8 hours until the polyvinyl alcohol sacrificial layer 2 is completely dissolved, and stripping the soft heater matrix 6 from the hard substrate 1.
e. And adhering a copper foil 7 and a polyimide tape 8 on the stripped soft heater substrate 6, wherein the thickness of the polyimide tape 8 is 60 microns.
So far, the preparation of the quick response soft heater with the self-adaptive shape of the parallelogram is completed. The parallelogram design can cause asymmetric deformation compared to a U-shaped heater, and the heater not only curls but also rotates when actuated, thus it has a larger footprint
The overall thickness of the soft robot obtained in this example is the sum of the thicknesses of the three layers, i.e. 220 μm, as shown in fig. 3.
Example 3
a. The selection of the hard substrate 1 and the preparation of the sacrificial layer 2 are the same as in example 1.
b. The rigid substrate 1 was placed on the stage of a manual screen printing machine with the screen parallel to the rigid substrate 2 and held at a spacing of 8 mm. The screen takes the pattern shown in fig. 3, i.e. a parallelogram, after which the hard substrate 1 is heated to cure the conductive material 3, forming a patterned conductive layer 4. The conductive layer 4 has a thickness of 25 micrometers.
c. Polydimethylsiloxane was spin-coated on the sacrificial layer 2 as the flexible substrate 5 of this shape-adaptive fast response soft heater at a spin-coating speed of 650 rpm for 3 minutes to coat the patterned conductive layer 4, followed by heating to cure it. The curing temperature was 80 ℃ and the curing time was 1 hour. The flexible substrate 5 has a thickness of 125 μm under this condition.
d. And (3) putting the sample into deionized water, heating at 80 ℃ for 8 hours until the polyvinyl alcohol sacrificial layer 2 is completely dissolved, and stripping the soft heater matrix 6 from the hard substrate 1.
e. And adhering a copper foil 7 and a polyimide adhesive tape 8 to the primary soft heater body obtained after stripping, wherein the thickness of the polyimide adhesive tape 8 is 60 microns.
Thus, the preparation of the fast response soft heater with the shape self-adaptive to the parallelogram with the other thickness is completed. The difference in thickness is achieved by varying the amount of conductive material during screen printing and the angle to the horizontal during doctor blade.
The overall thickness of the soft robot obtained in this example is the sum of the thicknesses of the three layers, i.e. 210 microns.
Example 4
a. The selection of the hard substrate 1 and the preparation of the sacrificial layer 2 are the same as in example 1.
b. The rigid substrate 1 was placed on the stage of a manual screen printing machine with the screen parallel to the rigid substrate 2 and held at a spacing of 8 mm. The screen is patterned into four finger patterns using four U-shaped patterns as shown in fig. 2, and then the hard substrate 1 is heated to cure the conductive material 3 to form a patterned conductive layer 4. The conductive layer 4 has a thickness of 15 microns.
c. Polydimethylsiloxane was spin-coated on the sacrificial layer 2 as the flexible substrate 5 of this shape-adaptive fast response soft heater at a spin speed of 750 rpm for 2 minutes to coat the patterned conductive layer 4, followed by heating to cure it. The curing temperature was 80 ℃ and the curing time was 1 hour. The flexible substrate 5 has a thickness of 135 micrometers under this condition.
d. And (3) putting the sample into deionized water, heating at 80 ℃ for 8 hours until the polyvinyl alcohol sacrificial layer 2 is completely dissolved, and stripping the soft heater matrix 6 from the hard substrate 1.
e. And adhering a copper foil 7 and a polyimide adhesive tape 8 to the primary soft heater body obtained after stripping, wherein the thickness of the polyimide adhesive tape 8 is 60 microns.
To this end, a four-finger shaped, shape adaptive, fast response soft heater is prepared. Compared with the common U-shaped soft heater, the four-finger heater has larger coverage area and more flexible gripping form, and can grip objects with complex profiles.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (9)

1. A method for preparing a shape-adaptive fast response soft heater is characterized by comprising the following steps:
s1, preparing a sacrificial layer (2) which is formed by solidifying a polyvinyl alcohol aqueous solution on a hard substrate (1);
s2, printing a paste-shaped conductive material with a specified shape on the surface of the sacrificial layer (2) prepared in the step S1, and then heating to cure the paste-shaped conductive material with the specified shape, thereby preparing a shaped conductive functional layer (3), wherein the viscosity of the paste-shaped conductive material is 10 Pa-100 Pa-S, and the conductivity of the paste-shaped conductive material is more than 1 x 10 Pa-S5S/m；
S3, coating flexible high polymer materials on the surfaces of the sacrificial layer (2) and the conductive functional layer (3) in a spinning mode to enable the surfaces to be uniformly coated with the conductive functional layer (3), then heating the flexible high polymer materials to enable the flexible high polymer materials to be solidified, and thus obtaining a flexible substrate (5) coated with the conductive functional layer (3), wherein the hard substrate (1), the sacrificial layer (2), the conductive functional layer (3) and the flexible substrate (5) jointly form a soft heater matrix;
s4, cutting the soft heater matrix according to the shape of the conductive functional layer (3), then putting the cut soft heater matrix into deionized water and heating to completely dissolve the sacrificial layer (2) so as to peel off the hard substrate (1), thereby obtaining a soft heater primary body formed by the conductive functional layer (3) and the flexible substrate (5);
s5, connecting two ends of a conductive function layer (3) forming the primary body of the soft heater and a copper foil to an external power supply through silver paste, and adhering a polyimide adhesive tape to one side, far away from a flexible substrate (5), of the conductive function layer (3) to obtain an insulating layer (8) for insulating the conductive function layer (3), wherein the flexible substrate (5) and the insulating layer (8) have thermal expansion difference, and therefore the soft heater with the self-adaptive shape is prepared.
2. The preparation method according to claim 1, wherein in step S1, the aqueous solution of polyvinyl alcohol is prepared from polyvinyl alcohol powder and a dispersant, wherein the mass fraction of the polyvinyl alcohol is 8% to 12%, the mass fraction of the dispersant is 0.5% to 2%, and the dispersant is sodium dodecylbenzene sulfonate or sodium dodecyl sulfate; further, the preparation method of the polyvinyl alcohol aqueous solution comprises the following steps: adding polyvinyl alcohol powder and a dispersing agent into deionized water, and stirring for 4-6 h at the temperature of 60-80 ℃.
3. The method according to claim 1, wherein step S1 specifically comprises the steps of:
s11, sequentially cleaning the hard substrate (1) by using acetone, isopropanol and deionized water, and then blowing the hard substrate (1) dry by using nitrogen;
s12, spin-coating the upper surface of the hard substrate (1) treated in the step S11 with a polyvinyl alcohol aqueous solution, and heating the polyvinyl alcohol aqueous solution to solidify into a film so as to form the sacrificial layer (2), wherein the spin-coating speed of the polyvinyl alcohol aqueous solution is 300rad/min to 1000rad/min, the spin-coating time is 2min to 5min, the heating temperature is 60 ℃ to 120 ℃, and the solidification time is 15min to 30min, so that the sacrificial layer (2) with a smooth surface and close adhesion with the hard substrate (1) is obtained.
4. The method of claim 1, wherein the step of printing a paste-like conductive material of a designated shape on the surface of the sacrificial layer (2) prepared in the step S1 in the step S2 comprises the steps of: and uniformly coating the pasty conductive material on the screen printing plate and covering the hollow patterns on the screen printing plate, and scraping the surface of the screen printing plate, so that the pasty conductive material coated on the screen printing plate is printed on the sacrificial layer (2) after penetrating through the hollow patterns on the screen printing plate.
5. The method according to claim 1, wherein the thickness of the conductive functional layer (3) is 20 μm to 50 μm.
6. The production method according to claim 1, wherein in step S5, the insulating layer (8) has a thickness of 40 to 80 μm.
7. The method of any one of claims 1-6, wherein the flexible polymeric material is polydimethylsiloxane, copolyester, or platinum-catalyzed silicone rubber.
8. A shape-adaptive fast response soft heater prepared by the preparation method of any one of claims 1 to 7.
9. A soft heater according to claim 8, wherein the electrically conductive functional layer (3) is U-shaped or an array of multiple U-shaped connections.
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