CN114957770A

CN114957770A - Anisotropic porous material with adjustable pore diameter gradient and preparation method and application thereof

Info

Publication number: CN114957770A
Application number: CN202210670678.5A
Authority: CN
Inventors: 张硕; 宗子盛; 吴志刚
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2022-06-14
Filing date: 2022-06-14
Publication date: 2022-08-30
Anticipated expiration: 2042-06-14
Also published as: CN114957770B

Abstract

The invention discloses an anisotropic porous material with adjustable aperture gradient and a preparation method and application thereof, belonging to the related field of porous materials, and the method comprises the following steps: (S1) mixing the gallium-based liquid metal having the oxide film formed on the surface thereof into the silicone rubber material prepolymer to form uniformly dispersed micro droplets; (S2) adding ammonium bicarbonate powder, mixing uniformly, adding a silicon rubber material cross-linking agent, and mixing uniformly; (S3) standing at room temperature until ammonium bicarbonate and gallium-based liquid metal are deposited; (S4) heating at high temperature to make ammonium bicarbonate decompose by heating, and the silicon rubber material prepolymer and the silicon rubber material cross-linking agent are cross-linked and cured to form the anisotropic porous material with pore size gradient. The method can prepare the anisotropic porous material with the adjustable pore diameter gradient and the pore diameter range of 0.08-3.2 mm, and the porous material can be used for preparing flexible pressure capacitance and resistance sensors with various structures and an imitative nose line-like soft hand grip, and has great application value in the fields of soft robots and the like.

Description

Anisotropic porous material with adjustable pore diameter gradient and preparation method and application thereof

Technical Field

The invention belongs to the technical field of porous materials, and particularly relates to an anisotropic porous material with adjustable pore diameter gradient, and a preparation method and application thereof.

Background

In recent years, software robots have been rapidly developed, and in order to realize efficient interaction with external environments, intelligent body materials with sensing functions are urgently needed for software robots. The porous material is expected to be used as an interface or a structure to bear various intelligent functions because of the advantages of strong physical and chemical stability, high inherent porosity, light weight, designable structural function and the like.

The silicone rubber material has the advantages of strong adsorption capacity, good thermal stability, stable chemical properties, etc., and is the earliest and most widely used material in the development process of soft robots, such as Polydimethylsiloxane (PDMS). However, the current porous silicone rubber materials are generally prepared by a template method using salt or sugar as a template: adding salt or sugar particles serving as a pore-forming agent into an uncrosslinked silicone rubber material, heating the silicone rubber to perform hydrosilylation reaction for curing, and dissolving the pore-forming agent by water or other solvents to prepare the porous silicone rubber sponge. The porous silicone rubber sponge thus produced has pore distribution limited by the template, random distribution of pores of different diameters caused by the phenomena of template agglomeration, template size and distribution nonuniformity, etc., and has small pore size variation range and no obvious overall anisotropy (Benjamin R.Thompson, Tommy S.Horozov et al. high efficiency structures and pore Materials from Soft structures [ J ] Journal of Materials Chemistry A,2019,7,8030 and 8049), which severely limits its application in the field of soft body robots, such as human-machine interface, compliance mechanism, etc.

In addition, there are also processes for preparing porous silicone rubber materials by gas bubbling through the formation of gases by physicochemical reactions, e.g. by the reaction of carbonAmmonium hydrogen acid (NH4HCO3) as a gas blowing agent is added to an uncrosslinked silicone rubber material, and a porous silicone rubber material (Benjamin C, Mac Murray et al. porous elastic Foams for Simple fabrics of Complex Soft Robots [ J ] is prepared by a method of generating gas by heating while the silicone rubber is cross-linked and cured by a hydrosilylation reaction]Advanced Materials,2015,27, 6334-. Because most of the silicon rubber materials used for manufacturing the soft robot use organic platinum as a crosslinking catalyst, and the electronegative strong amino group (-NH) in the ammonium bicarbonate ₃ ) Can inhibit the catalytic activity of the organic platinum catalyst (Senng Hee Jeong, Shuo Zhang et al PDMS-Based Elastomer tube Soft, Stretchable, and Sticky for Epidermal Electronics [ J)]Advanced Materials,2016,28, 5830-.

Disclosure of Invention

In view of the above defects or improvement needs of the prior art, the present invention provides an anisotropic porous material with adjustable pore size gradient, and a preparation method and application thereof, thereby solving the technical problem that the prior art lacks a reliable preparation method for obtaining a porous silicone rubber material with adjustable pore size gradient.

In order to achieve the above object, according to one aspect of the present invention, the following technical solutions are provided:

a preparation method of an anisotropic porous material with adjustable aperture gradient comprises the following steps:

(S1) mixing the gallium-based liquid metal with the surface formed with the oxide film into the silicon rubber material prepolymer to form uniformly dispersed micro droplets to obtain a first mixture;

(S2) adding ammonium bicarbonate powder into the first mixture, uniformly mixing, then adding a silicon rubber material cross-linking agent, and uniformly mixing to obtain a second mixture;

(S3) allowing the second mixture to stand at room temperature until ammonium bicarbonate and the gallium-based liquid metal are deposited in the second mixture;

(S4) heating the mixture obtained in the step (S3) at high temperature to decompose ammonium bicarbonate by heating, and crosslinking and curing the prepolymer of the silicon rubber material and the crosslinking agent of the silicon rubber material to form the anisotropic porous material with the pore size gradient.

Preferably, in the second mixture, the mass percentage content of each reactant is: 45-57 percent of ammonium bicarbonate, 3.9-5 percent of gallium-based liquid metal and 39.1-50 percent of silicon rubber material, wherein the content of the silicon rubber material is the sum of the content of the silicon rubber material in the prepolymer of the silicon rubber material and the content of the silicon rubber material in the cross-linking agent of the silicon rubber material.

Preferably, the silicone rubber material prepolymer is a vinyl-containing terminated dimethyl siloxane prepolymer; the silicon rubber material cross-linking agent is a dimethyl siloxane cross-linking agent containing dimethyl chain units and methyl hydrogen chain units.

Preferably, in the step (S1), the diameter of the micro droplets is 5 to 15 μm; in the step (S2), the particle size of the ammonium bicarbonate powder is 0.2 to 3 μm.

Preferably, in the step (S4), the high-temperature heating method is: and heating the mixture in a high-temperature environment of 120 +/-10 ℃ for 2-3 hours.

Preferably, the gallium-based liquid metal comprises a gallium indium tin ternary alloy, a gallium indium alloy or gallium.

According to another aspect of the invention, the following technical scheme is also provided:

the anisotropic porous material prepared by the preparation method of the anisotropic porous material with adjustable pore size gradient is obtained.

a flexible pressure capacitance type sensor based on an anisotropic porous material with adjustable aperture gradient comprises an upper electrode first substrate, an upper electrode second substrate, the anisotropic porous material, a lower electrode first substrate, a lower electrode and a lower electrode second substrate which are sequentially stacked from top to bottom.

a flexible pressure capacitance type sensor based on an anisotropic porous material with adjustable aperture gradient comprises an upper electrode substrate, an upper electrode, the anisotropic porous material, a lower electrode and a lower electrode substrate which are sequentially stacked from top to bottom.

an elephant trunk line-driving soft body robot based on an anisotropic porous material with adjustable pore diameter gradient comprises a plurality of sections of elephant trunk bodies which are sequentially bonded together, and pull ropes which sequentially penetrate through the plurality of sections of elephant trunk bodies;

the trunk of.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

1. the invention provides a preparation method of an anisotropic porous material with adjustable pore size gradient, which comprises the steps of mixing gallium-based liquid metal with an oxide film formed on the surface into a silicon rubber material prepolymer to form uniformly dispersed micro liquid drops, mixing ammonium bicarbonate powder, adding a silicon rubber material cross-linking agent, forming gradient distribution after the ammonium bicarbonate and the liquid metal are deposited, heating at high temperature, decomposing the ammonium bicarbonate by heating, and cross-linking and curing the silicon rubber material in the mixture to form the anisotropic porous material with the pore size gradient, wherein pores in the anisotropic porous material are mutually connected, have the pore size gradient in the longitudinal direction, and the pore size range is 0.08-3.2 mm. In this method, the cause of the generation of the pore diameter gradient includes: (1) ammonium bicarbonate powder and liquid metal droplets distributed in a gradient manner in a mixture system; (2) from bottom to top, the bubbles are gradually reduced under the pressure of the liquid, and the volume of the bubbles is increased; (3) after the bubbles are generated, the bubbles move upwards due to buoyancy and are combined with bubbles above to form larger bubbles; in addition, the ammonium bicarbonate serving as a gas foaming agent is completely decomposed at high temperature to generate gas without residual impurities, and meanwhile, the amino group in the ammonium bicarbonate inhibits the crosslinking and curing of the silicon rubber material to prolong the curing time, so that the liquid state of the mixture is ensured, and sufficient window time is provided for the generation, movement and collection of bubbles in the silicon rubber; an electronic competition mechanism among gallium (from gallium-based liquid metal), nitrogen (from ammonium bicarbonate) and platinum (from a silicon rubber material) brought by the liquid metal is introduced, the electronic competition mechanism can regulate and control the release rate and the curing rate of bubbles of a mixture system, so that the pore gradient of the generated porous material is regulated and controlled, and a regulating and controlling means is provided for the pore-forming process of the mixture system; the method has the advantages of simple operation, high success rate and low cost, and the used materials are common and easily available, such as ammonium bicarbonate, silicon rubber materials and gallium-based liquid metal.

2. The preparation method of the anisotropic porous material with adjustable pore size gradient, provided by the invention, regulates the proportion of reactants of ammonium bicarbonate, gallium-based liquid metal and polydimethylsiloxane, regulates and controls the parameters of the generated porous material such as pore size, gradient and distribution by combining the regulation of heating time and temperature, and further, also plays a role in regulating and controlling the rigidity gradient of the porous material; in the mass percentage content range of the reactant provided by the invention, the increase of the content of the ammonium bicarbonate is beneficial to generating the porous material with larger pore size gradient.

3. According to the preparation method of the anisotropic porous material with the adjustable pore size gradient, provided by the invention, the diameter of the gallium-based liquid metal micro liquid drop is 5-15 micrometers, and the particle size of the ammonium bicarbonate powder is 0.2-3 micrometers, so that the ammonium bicarbonate powder is fully contacted with the liquid metal liquid drop, reactants are fully reacted, and the pore size gradient of the formed anisotropic porous material is more controllable and uniform.

4. The anisotropic porous material obtained by the preparation method can be used for preparing flexible pressure capacitive sensors and pseudo-elephant-nose line-driven soft robots with various structures, and the flexible pressure capacitive sensors and the pseudo-elephant-nose line-driven soft robots have excellent performance due to controllable pore size gradient distribution of the anisotropic porous material, and have great application value in the fields of soft robots and the like.

Drawings

FIG. 1 is a cross-sectional scan of a micro CT of an anisotropic porous material made in example 1 of the present invention;

FIG. 2 is a three-dimensional reconstructed model of a micro CT of an anisotropic porous material prepared in example 1 of the present invention;

FIG. 3 is a photograph of a cross-section of an anisotropic porous material obtained in example 1 of the present invention;

FIG. 4 is a photograph of a cross-section of an anisotropic porous material obtained in example 2 of the present invention;

FIG. 5(a) is a stereomicroscope picture of an anisotropic porous material coated with a liquid metal;

fig. 5(b) is a stereomicroscope picture of an anisotropic porous material coated with a 10% aqueous solution of polyvinyl alcohol;

FIG. 6 is a schematic structural diagram of a flexible pressure capacitive sensor based on an anisotropic porous material with adjustable pore size gradient according to embodiment 3 of the present invention;

FIG. 7 is a schematic structural diagram of a flexible piezoresistive sensor based on an anisotropic porous material with adjustable pore size gradients according to embodiment 4 of the present invention;

FIG. 8 is a schematic structural diagram of an elephant trunk line-flooding soft robot based on an anisotropic porous material with adjustable pore size gradients, according to embodiment 5 of the present invention;

FIG. 9(a) is an assembly of an elephant trunk-driving soft-body robot based on an anisotropic porous material with adjustable pore size gradient according to example 5 of the present invention;

FIG. 9(b) is another assembly of the pseudo trunk line-driving soft robot based on the anisotropic porous material with adjustable pore size gradient according to embodiment 5 of the present invention;

fig. 9(c) is a third assembly form of the pseudo-elephant trunk line-driving soft-body robot based on the anisotropic porous material with adjustable pore size gradient according to embodiment 5 of the present invention.

The same reference numbers will be used throughout the drawings to refer to the same elements or structures, wherein:

110. an upper electrode; 111. an upper electrode first substrate; 112. an upper electrode material; 113. an upper electrode second substrate; 120. an anisotropic porous material; 130. a lower electrode; 131. a lower electrode first substrate; 132. a lower electrode material; 133. a lower electrode second substrate; 100. a first trunk imitation trunk; 200. a first adhesive material; 300. a second trunk like a trunk; 400. a second adhesive material; 500. a third trunk imitating elephant nose; 600. a third adhesive material; 700. a fourth trunk imitating elephant trunk; 800. and pulling a rope.

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 respective embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention provides a preparation method of an anisotropic porous material with adjustable aperture gradient, which comprises the steps of adding ammonium bicarbonate serving as a gas foaming agent and a gallium-based liquid metal oxide into an uncrosslinked silicone rubber material PDMS, regulating and controlling the catalytic activity of a platinum catalyst in the silicone rubber hydrosilylation reaction through an electronic competition mechanism among gallium, nitrogen and platinum, heating the gas foaming agent to decompose and generate gas in the heating process, forming anisotropic pores which are mutually connected, heating to promote the hydrosilylation reaction of the silicone rubber material to crosslink the silicone rubber material, and curing the mutually connected anisotropic pores.

The preparation method of the anisotropic porous material with adjustable pore size gradient provided by the invention comprises the following steps:

preferably, the oxide film is formed in the following manner: exposing gallium-based liquid metal in air to rotate at a high speed until the liquid metal is flattened to form a thin oxide film; the thickness of the oxide film is 1-2nm, the thickness of the flattened gallium-based liquid metal is related to the amount of the gallium-based liquid metal used and the caliber of a container used by high-speed rotation at the time, and no fixed value is available. The oxide film is naturally in the air, and the high-speed rotation can increase the area of the oxide film and enable the liquid drops to be flat.

The gallium-based liquid metal includes gallium indium tin ternary alloy, gallium indium alloy or gallium. The gallium-based liquid metal has excellent thermal conductivity, and thus the thermal conductivity of the entire mixture can be improved to accelerate the solidification of the mixture.

specifically, a mixture formed by ammonium bicarbonate powder, gallium-based liquid metal droplets, a silicone rubber material prepolymer and a silicone rubber material cross-linking agent needs to be mixed for multiple times to ensure that the ammonium bicarbonate powder and the liquid metal droplets are in full contact; the particle size of the ammonium bicarbonate powder is preferably 0.2-3 microns, and the diameter of the micro-droplets is preferably 5-15 microns. It should be noted that, the volume and mass of the micro-droplets formed by mixing the gallium-based liquid metal into the PDMS prepolymer of the silicone rubber material are larger than those of the added ammonium bicarbonate powder, and during the mixing process, the liquid metal droplets will coat the contacted ammonium bicarbonate powder.

In the second mixture, the mass percent of each reactant is as follows: 45-57 percent of ammonium bicarbonate, 3.9-5 percent of gallium-based liquid metal and 39.1-50 percent of silicon rubber material, wherein the content of the silicon rubber material is the sum of the content of the silicon rubber material in the prepolymer of the silicon rubber material and the content of the silicon rubber material in the cross-linking agent of the silicon rubber material.

Within the mass percentage content range, the increase of the content of the ammonium bicarbonate is beneficial to generating the porous material with larger pore size gradient. If the content of ammonium bicarbonate exceeds the above range, the inhibition effect on the cross-linking and curing of the silicone rubber material is too strong, the curing speed of the silicone rubber material is too slow, and finally, a porous material with low porosity is generated.

specifically, the mixture is allowed to stand for about 12 hours, and according to the characteristics of the polymer, the effect of depositing (gradient distribution) ammonium bicarbonate and liquid metal in the mixture is achieved, and if the deposition occurs, the gradient distribution is meant.

During the standing process, the liquid metal droplets and the ammonium bicarbonate can partially settle, and the liquid metal and the ammonium bicarbonate are distributed in a gradient manner in the longitudinal direction, so that the ammonium bicarbonate at the bottom of the mixture is more easily decomposed to generate more bubbles during subsequent heating.

Specifically, the high-temperature heating method comprises the following steps: and heating the mixture in a high-temperature environment of 120 +/-10 ℃ for 2-3 hours. In the heating process of the mixture, ammonium bicarbonate is heated and decomposed, gas generated at the bottom of the mixture is influenced by the pressure of the mixture to form smaller bubbles, the bubbles move upwards under the influence of buoyancy and are converged with gas above to form larger bubbles, meanwhile, the bubbles at the top of the mixture are influenced by the pressure of the mixture to be smaller, the bubbles which are mutually connected and are anisotropic in the longitudinal direction are formed inside the mixture, the prepolymer of the silicon rubber material and the crosslinking agent PDMS of the silicon rubber material in the mixture are continuously crosslinked and cured along with the continuous heating process, and finally, channels formed by the mutually connected bubbles are cured.

In the above steps, the silicone rubber material is a material system capable of being cross-linked and cured under the action of a platinum complex catalyst, preferably, the silicone rubber material prepolymer is a vinyl-terminated polydimethylsiloxane prepolymer, and the silicone rubber material cross-linking agent is a polydimethylsiloxane cross-linking agent containing dimethyl chain units and methyl hydrogen chain units. The final anisotropic porous material with pore size gradient is Polydimethylsiloxane (PDMS) sizing material which is obtained by taking vinyl-containing terminated polydimethylsiloxane as a prepolymer, taking polydimethylsiloxane containing dimethyl chain units and methyl hydrogen chain units as a cross-linking agent and taking a platinum complex as a cross-linking catalyst.

The crosslinking and curing reaction of PDMS is a hydrosilylation reaction which is generated by catalyzing polymer monomers by a platinum catalyst, the electronegativity of amino groups in ammonium bicarbonate is strong, the catalytic activity of the platinum catalyst is inhibited, and the electronic competition mechanism among gallium, nitrogen and platinum can regulate and control the release rate and the curing rate of bubbles in a mixture system, thereby regulating and controlling the pore gradient of the generated porous material.

The anisotropic porous material obtained by the method has anisotropy, the pore diameter gradient can be adjusted, and the pore diameter variation range is 0.08-3.2 mm. Causes of the pore size gradient include: 1. ammonium bicarbonate powder and liquid metal droplets distributed in a gradient manner in a mixture system; 2. from bottom to top, the bubbles are gradually reduced under the pressure of the liquid, and the volume of the bubbles is increased; 3. after the bubbles are generated, the bubbles have the tendency of moving upwards due to buoyancy and combining with the bubbles above to form larger bubbles.

The anisotropic porous material obtained by the method can be used for manufacturing flexible piezoresistance type sensors and anisotropic imitative elephant nose line drive soft handgrips with integrated structures and sensing. The soft hand grip can identify and classify the shape, the rigidity and the surface appearance of the object.

The anisotropic porous material with adjustable pore size gradient, the preparation method and the application thereof provided by the present invention are further described in detail with reference to the following examples and the accompanying drawings.

Example 1

The embodiment provides a preparation method of an anisotropic porous material with adjustable aperture gradient, which comprises the following steps:

s1, exposing 0.5g gallium-based liquid metal in the air to rotate at high speed until the liquid metal is flattened to form a thin oxide film;

s2, adding 10g of PDMS prepolymer into a container filled with a liquid metal oxide film, and rotating at a high speed to form uniformly dispersed micro droplets in the PDMS prepolymer;

s3, adding 5g of ammonium bicarbonate powder into the mixture, and carrying out high-speed rotation mixing to uniformly disperse the ammonium bicarbonate powder in the mixture;

s4, adding 1g of PDMS crosslinking agent into the mixture, and uniformly mixing the mixture by high-speed rotation;

s5, pouring the mixture into a glass container, and standing at room temperature for 12 hours;

s6, placing the glass container filled with the mixture into an oven, and heating for 2 hours at 120 ℃;

s7, taking the cured porous PDMS out of the glass container, and standing at room temperature for half an hour until the residual water vapor and ammonia inside are completely volatilized, and obtaining the corresponding material as shown in fig. 1, fig. 2 and fig. 3. It can be seen from the figure that the diameters of the holes are arranged from 0.08mm to 3.2mm in a gradient increasing trend from the bottom to the top of the material, the rigidity difference between the top and the bottom of the material is large due to the holes arranged in the porous material in a gradient manner, when external applied pressure is small, the low rigidity area at the top of the porous material can be obviously deformed, the low rigidity area is compressed to the limit along with the increase of the applied pressure, and the high rigidity area begins to deform, so that the porous material not only realizes sensitive sensing of low stress in the compression process, but also realizes a wider stress detection range.

Example 2

s3, adding 7.5g of ammonium bicarbonate powder into the mixture, and carrying out high-speed rotary mixing to uniformly disperse the ammonium bicarbonate powder in the mixture;

s7, taking the cured porous PDMS out of the glass container, and standing at room temperature for half an hour until the residual water vapor and ammonia inside are completely volatilized, wherein the obtained corresponding material is shown in FIG. 4. As can be seen from the figure, compared with the porous material described in embodiment 1, the porous material described in this embodiment has smaller pore diameter, more dense pore distribution, and larger overall rigidity value, and is suitable for application scenarios with larger measurement width.

In addition to the methods for preparing porous materials with adjustable pore size gradients described in examples 1 and 2, the pore size gradient can be adjusted by adjusting the addition amount of liquid metal (0.1g to 2g) and the addition amount of ammonium bicarbonate (2.5g to 10 g). With the increase of the content of the liquid metal, the pore diameter gradient is increased, the diameter of the pores is also increased as a whole, when the addition amount of the liquid metal is 0.1g, the pore diameter gradient in the porous material is not obvious, and the pore diameter of the top area is smaller; when the addition amount of the liquid metal is 2g, the pore size gradient inside the porous material is very obvious, and the pore size in the top area is larger. With the increase of the addition amount of ammonium bicarbonate, the number of pores in the porous material is increased, the pore diameter is increased, the volume of the prepared porous material is increased, and the rigidity is reduced. The porous material with ideal pore diameter gradient and distribution can be obtained by adjusting the addition amounts of the liquid metal and the ammonium bicarbonate.

Example 3

The embodiment provides a preparation method of a flexible pressure capacitance type sensor based on an anisotropic porous material with adjustable pore size gradient.

Fig. 6 is a schematic diagram of a flexible pressure capacitance sensor based on porous material. The sensor mainly includes seven parts, which are an upper electrode first substrate 111, an upper electrode material 112, an upper electrode second substrate 113, an anisotropic porous material 120, a lower electrode first substrate 131, a lower electrode material 132, and a lower electrode second substrate 133, respectively. The materials of the upper electrode first substrate 110, the upper electrode second substrate 113, the lower electrode first substrate 131 and the lower electrode second substrate 133 are flexible PET films, the materials of the upper electrode material 112 and the lower electrode material 132 are conductive fabrics which can be purchased conveniently, and the anisotropic porous material 120 is the same as the porous material prepared in example 1.

The preparation method of the flexible pressure sensor based on the anisotropic porous material with adjustable pore size gradient, which is described in the embodiment, comprises the following specific steps:

firstly, a flexible PET film is selected as a first substrate 111 of an upper electrode, a thin layer of adhesive glue (Silpoxy) is coated on the flexible PET film, a piece of conductive fabric is used as an upper electrode material 112 and is placed on the PET film coated with the adhesive glue, a thin layer of adhesive glue is coated on one surface, far away from the first substrate 111 of the upper electrode, of the conductive fabric, a flexible PET film is used as a second substrate 113 of the upper electrode and is placed on the surface, coated with the adhesive glue, of the conductive fabric to form an upper electrode 110, and the upper electrode is placed in an oven to be heated for 10min at 75 ℃ until the adhesive glue is solidified.

The PET film may be replaced by a cross-linked cured (A, B liquid to 10: 1) Polydimethylsiloxane (PDMS) film, and the adhesive glue may be replaced by a more readily available 401 glue or (A, B liquid to 10: 1) Polydimethylsiloxane (PDMS) precursor liquid.

The anisotropic porous material prepared in example 1 was taken as an auxiliary material for the production, the porous material was put into a plasma cleaning machine for treatment for 10min, and then the porous material was quickly placed in a container containing gallium-based liquid metal, the liquid metal was uniformly coated on the surface and all pores of the porous material by repeatedly pressing the porous material using negative pressure, and the excess liquid metal was squeezed out to obtain the anisotropic porous material 120.

It should be noted that the surface of the anisotropic porous material may be coated with not only the gallium-based liquid metal but also 10% -30% of aqueous solution of polyvinyl alcohol (PVA) or aqueous solution of polyvinyl alcohol-tannic acid (PVA-TA) to enhance the overall stiffness of the porous material, and the interface of the anisotropic porous material coated with the above two liquids is shown in fig. 5(a) and fig. 5 (b).

Coating a thin layer of adhesive glue on the surface of the upper electrode second substrate 113 far away from the upper electrode material 112, placing the anisotropic porous material 120 on the upper electrode second substrate 113, and placing the upper electrode second substrate in an oven to heat at 75 ℃ for 10min until the adhesive glue is cured.

The lower electrode first substrate 131, the lower electrode material 132 and the lower electrode second substrate 133 are sequentially disposed to constitute the lower electrode 130 according to the above-described method, and the upper electrode 110, the anisotropic porous material 120 and the lower electrode 130 are constituted to constitute the flexible pressure sensor.

It should be noted that, as shown in fig. 6, the sensor described in this embodiment is a flexible pressure capacitance type sensor with adjustable detection range.

The capacitance value of the capacitance sensor is mainly determined by the dielectric constant of the dielectric layer and the distance between the two electrodes, when the flexible pressure sensor is not compressed in the embodiment, the dielectric layer is made of PDMS doped with liquid metal and air, and the dielectric constant is small because the porous material has the characteristic of high pore volume rate; when the sensor is compressed, the distance between two polar plates is reduced, air in the porous material is extruded out, the dielectric constant of the dielectric layer is greatly increased, and finally the sensor generates great capacitance change, so that the porous material is very suitable for being used as the dielectric material of the flexible pressure sensor.

Example 4

The embodiment provides a preparation method of a flexible piezoresistance sensor based on an anisotropic porous material with adjustable pore size gradient.

Fig. 7 is a schematic structural diagram of a flexible piezoresistive sensor based on a porous material. The sensor mainly includes five parts, which are an upper electrode first substrate 111, an upper electrode material 112, an anisotropic porous material 120, a lower electrode material 132, and a lower electrode first substrate 131. The material of the upper electrode first substrate 111 and the lower electrode first substrate 131 is a flexible PET film, the material of the upper electrode material 112 and the lower electrode material 132 is a copper foil, and the anisotropic porous material 120 is the same as the porous material prepared in example 1.

firstly, a flexible PET film is selected as a first substrate 111 of an upper electrode, a thin layer of adhesive glue (Silpoxy) is coated on the flexible PET film, a piece of copper foil is used as an upper electrode material 112 and is placed on the PET film coated with the adhesive glue to form an upper electrode 110, and the upper electrode is placed in an oven to be heated for 10min at 75 ℃ until the adhesive glue is solidified.

It should be noted that the surface of the anisotropic porous material may be coated with not only the gallium-based liquid metal but also 10% -30% of a polyvinyl alcohol (PVA) aqueous solution or a polyvinyl alcohol-tannic acid (PVA-TA) aqueous solution to enhance the overall stiffness of the porous material.

Coating a thin layer of adhesive glue and conductive silver paste as a conductive material on the surface of the upper electrode material 112 far away from the first substrate 111 of the upper electrode, placing the anisotropic porous material 120 on the surface of the upper electrode material 112, and heating in an oven at 75 ℃ for 10min until the adhesive glue and the conductive silver paste are cured.

The lower electrode material 132 and the lower electrode first substrate 131 are sequentially disposed to constitute the lower electrode 130 in the above-described manner, and the upper electrode 110, the anisotropic porous material 120 and the lower electrode 130 are constituted as the flexible pressure sensor.

It should be noted that, as shown in fig. 6, the sensor described in this embodiment is a flexible piezoresistive sensor with adjustable detection range.

In this embodiment, the gallium-based liquid metal is coated on the inner wall of the porous material to enhance the conductivity of the material, the gallium-based liquid metal has excellent conductivity and is liquid, and has good stretchability and rapid recovery performance.

Example 5

The embodiment provides a preparation method of an elephant trunk line-driving soft robot based on an anisotropic porous material with adjustable pore size gradient.

Fig. 7 is a schematic structural diagram of the pseudo-elephant nose line software-expelling robot based on anisotropic porous material. The trunk simulation soft line-drive soft robot mainly comprises four trunk simulation noses (namely a first trunk simulation nose 100, a second trunk simulation nose 300, a third trunk simulation nose 500 and a fourth trunk simulation nose 700) based on porous materials, bonding materials (namely a first bonding material 200, a second bonding material 400 and a third bonding material 600) and a pull rope 800. Wherein, the pull rope 800 adopts organic cotton absorbent cotton thread, and the bonding materials (the first bonding material 200, the second bonding material 400 and the third bonding material 600) adopt modified materials based on PDMS: s3PDMS (Seung heel Jeong, Shuo Zhuang et al. PDMS-Based Elastomer tube Soft, Stretchable, and Sticky for epiermal Electronics [ J ]. Advanced Materials,2016,28, 5830-.

Specifically, a first trunk 100 of an imitation elephant trunk based on anisotropic porous material is mainly composed of three parts: an upper electrode 110 composed of an upper electrode first substrate 111, an upper electrode material 112, an upper electrode second substrate 113, an anisotropic porous material 120, and a lower electrode 130 composed of a lower electrode first substrate 131, a lower electrode material 132, and a lower electrode second substrate 133. The materials of the upper electrode first substrate 111, the upper electrode second substrate 113, the lower electrode first substrate 131 and the lower electrode second substrate 133 are flexible PET films, the materials of the upper electrode material 112 and the lower electrode material 132 are conductive fabrics which can be purchased conveniently, and the porous material of the anisotropic porous material 120 is the same as the porous material prepared in example 1.

The preparation method of the elephant trunk line-drive software-like robot based on the anisotropic porous material with adjustable pore size gradient, which is disclosed by the embodiment, comprises the following specific steps of:

firstly, a flexible PET film is selected as a first substrate 111 of an upper electrode, a thin layer of adhesive glue (Silpoxy) is coated on the flexible PET film, a piece of conductive fabric is placed on the PET film coated with the adhesive glue, a thin layer of adhesive glue is coated on one surface, away from the first substrate 111 of the upper electrode, of the conductive fabric, a flexible PET film is placed on one surface, coated with the adhesive glue, of the conductive fabric as a second substrate 113 of the upper electrode, and the flexible PET film is placed in an oven and heated for 10min at 75 ℃ until the adhesive glue is cured.

It should be noted that the PET film can be replaced by a cross-linked cured (A, B liquid to liquid ratio of 10: 1) Polydimethylsiloxane (PDMS) film, and the adhesive glue can also be replaced by a more readily available 401 glue or (A, B liquid to liquid ratio of 10: 1) Polydimethylsiloxane (PDMS) precursor liquid.

Coating a thin layer of adhesive glue on the surface of the upper electrode second substrate 113 far away from the upper electrode material 112, placing the dielectric layer 120 based on the anisotropic porous material on the upper electrode second substrate 113, and heating in an oven at 75 ℃ for 10min until the adhesive glue is cured.

The first lower electrode substrate 131, the lower electrode material 132 and the second lower electrode substrate 133 are sequentially placed according to the above method to form a section of the first trunk 100 based on the anisotropic porous material.

According to the method, the second trunk imitation elephant nose 300, the third trunk imitation elephant nose 500 and the fourth trunk imitation elephant nose 700 are sequentially prepared.

Taking S3PDMS with proper size as a first adhesive material 200, placing a first trunk 100 and a second trunk 300 of the pseudo-elephant nose on two sides of the first adhesive material 200, assembling the second trunk 300 and a third trunk 500 of the pseudo-elephant nose with a second adhesive material 400, and assembling the third trunk 500 and a fourth trunk 700 of the pseudo-elephant nose with a third adhesive material 600 according to the method. The four segments of trunk of the pseudo trunk are penetrated by pull ropes 800, and the pull ropes are fixed at one side to form the pseudo trunk line driving soft robot.

It should be noted that the four anisotropic porous materials may be placed in three ways as shown in fig. 9(a), fig. 9(b), and fig. 9(c), but not limited to these three ways, the circles in the figures represent holes, and the pore diameters of the trunk of each pseudoelephant are distributed in a gradient manner according to the respective directions.

The robot is composed of a plurality of porous materials in different directions, deformation in any direction is carried out by utilizing the gradient structure of the porous materials, a common line driving robot needs a complex structural design, the deformation form and direction of the robot are difficult to change in the using process, and the robot is complex to operate.

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

1. A preparation method of an anisotropic porous material with adjustable aperture gradient is characterized by comprising the following steps:

2. The method according to claim 1, wherein the second mixture comprises the following reactants in percentage by mass: 45 to 57 percent of ammonium bicarbonate, 3.9 to 5 percent of gallium-based liquid metal and 39.1 to 50 percent of silicon rubber material, wherein the content of the silicon rubber material is the sum of the contents of the silicon rubber material in the silicon rubber material prepolymer and the silicon rubber material cross-linking agent.

3. The method for preparing the anisotropic porous material with adjustable pore size gradient according to claim 2, wherein the silicone rubber prepolymer is a vinyl-containing terminated dimethyl siloxane prepolymer; the silicon rubber material cross-linking agent is a dimethyl siloxane cross-linking agent containing dimethyl chain units and methyl hydrogen chain units.

4. The method for preparing the anisotropic porous material with adjustable pore size gradient according to claim 3, wherein in the step (S2), in the step (S1), the diameter of the micro-droplets is 5-15 μm; the particle size of the ammonium bicarbonate powder is 0.2-3 microns.

5. The method for preparing an anisotropic porous material with adjustable pore size gradient according to claim 1, wherein in the step (S4), the high temperature heating method comprises: and heating the mixture in a high-temperature environment of 120 +/-10 ℃ for 2-3 hours.

6. The method according to claim 1, wherein the gallium-based liquid metal comprises gallium indium tin ternary alloy, gallium indium alloy or gallium.

7. The anisotropic porous material prepared by the method for preparing an anisotropic porous material with adjustable pore size gradient according to any one of claims 1 to 6.

8. A flexible pressure capacitance type sensor based on an anisotropic porous material with adjustable pore size gradient is characterized by comprising an upper electrode first substrate, an upper electrode second substrate, the anisotropic porous material, a lower electrode first substrate, a lower electrode and a lower electrode second substrate which are sequentially stacked from top to bottom.

9. A flexible pressure capacitive sensor based on an anisotropic porous material with adjustable pore size gradient, comprising an upper electrode substrate, an upper electrode, the anisotropic porous material according to claim 7, a lower electrode and a lower electrode substrate which are sequentially stacked from top to bottom.

10. An elephant trunk line-driving soft robot based on an anisotropic porous material with adjustable pore diameter gradient is characterized by comprising a plurality of sections of elephant trunk bodies which are sequentially bonded together and pull ropes which sequentially penetrate through the plurality of sections of elephant trunk bodies;

the trunk of.