CN110642222B - High-length-diameter-ratio micron column array, and preparation method and application thereof - Google Patents
High-length-diameter-ratio micron column array, and preparation method and application thereof Download PDFInfo
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- CN110642222B CN110642222B CN201910931954.7A CN201910931954A CN110642222B CN 110642222 B CN110642222 B CN 110642222B CN 201910931954 A CN201910931954 A CN 201910931954A CN 110642222 B CN110642222 B CN 110642222B
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Abstract
The invention provides a high-length-diameter ratio micron column array, a preparation method and application thereof, wherein the preparation method comprises the following steps: s1, providing a hydrophobic template with a micropore array structure; mixing carbonyl iron powder and PDMS to obtain a composite solution; s2, infiltrating the composite solution into the hole structure of the hydrophobic template, heating to form a semi-cured state, and demolding to obtain a short columnar array; and S3, under the action of an external magnetic field, growing the short columnar array along the length direction, and curing to obtain the micron columnar array with high length-diameter ratio. The invention can prepare the gecko claw-like fiber array by a simple, universal and cheap technology, can combine the advantages of a bottom-up method and a top-down method, can conveniently obtain a high-length-diameter ratio micron column array, and is favorable for application in gecko-like adhesion.
Description
Technical Field
The invention relates to the technical field of micro-nano processing, in particular to a high-length-diameter-ratio micrometer column array, and a preparation method and application thereof.
Background
Geckos can adhere to or walk on almost any surface, whether wet or dry, smooth or rough, hard or soft; this outstanding adhesion and friction is mainly attributed to the complex multi-scale multi-layered fiber structure of the gecko foot. The hierarchical structure from macro to micro-nano scale enables gecko toes to be very soft under pressure and to make good contact with contact surfaces, and contact surfaces large enough to produce surprising adhesion. Also, gecko adhesion is unique in that it is self-cleaning during repeated use. Therefore, many researchers have designed a large number of biomimetic adhesive structures with geckos as inspiration, and hopefully develop dry adhesives like geckos.
At present, much research work on gecko-like adhesion focuses mainly on the processing of its hierarchical structure. For example, sunny et al, nano letters, propose vertical growth of carbon nanotubes on a silicon substrate to obtain gecko-like dry adhesives (Sethi S, ge L, ci L, et al, gecko-embedded carbon nanotube-based self-cleaning adhesives [ J ]. Nano letters,2008,8 (3): 822-825.). Wherein, the carbon nano tube array structure also has self-cleaning capability. The above-mentioned preparation method from bottom to top is simple in process and low in cost, but the array structure is difficult to be refined, and the structural stability is not good. Later, there were top-down processing methods that could compensate for the array structure deficiencies of the bottom-up method. For example, hyunchul et al, in the literature published by Small, obtained micron-scale columnar arrays by the method of PDMS template transfer (Park H, cho H, kim J, et al, multiscale transfer printing in-accessed microwells and on-cured surfaces via a biological hyperfluoropolyether stage [ J ]. Small,2014,10 (1): 52-59.).
However, the conventional template transfer method is limited to the preparation of a fiber structure having a relatively small major axis, and it is difficult to realize a fiber structure array having a high aspect ratio such as gecko claw, and fiber breakage may occur.
Disclosure of Invention
In view of this, the present application provides a micro-pillar array with a high aspect ratio, a preparation method and an application thereof.
The invention provides a preparation method of a high-length-diameter ratio micron column array, which comprises the following steps:
s1, providing a hydrophobic template with a micropore array structure;
mixing carbonyl iron powder and PDMS to obtain a composite solution;
s2, infiltrating the composite solution into the pore structure of the hydrophobic template, heating to form a semi-cured state, and demolding to obtain a short columnar array;
and S3, under the action of an external magnetic field, growing the short columnar array along the length direction, and curing to obtain the micron columnar array with high length-diameter ratio.
Preferably, in the step S1, the hydrophobic template is prepared according to the following steps:
A. coating the photoresist on the surface of a hydrophilic substrate, and baking to obtain a substrate coated with the photoresist;
B. combining a micron-sized dot matrix structure mask plate, and carrying out ultraviolet exposure on the substrate after glue coating to form a structure pattern corresponding to the mask on the surface of the substrate;
C. sequentially developing, cleaning and baking the exposed substrate surface to obtain a porous template with a micron pore array structure;
D. and carrying out hydrophobic treatment on the porous template to obtain the hydrophobic template with a micron pore array structure.
Preferably, when the hydrophobic template is prepared in step S1, the micron-sized lattice structure mask includes a plurality of circular units or a plurality of square units; the maximum width of each circular or square cell is 50 to 100 micrometers.
Preferably, when the hydrophobic template is prepared in step S1, perfluorooctyltrichlorosilane is used for hydrophobic treatment.
Preferably, when the composite solution is prepared in step S1, the mass ratio of the PDMS to the carbonyl iron powder is (10-15): 5.
preferably, in the step S2, the heating temperature is 70 to 90 ℃, and the heating time is 30 to 60 seconds.
Preferably, in step S3, the external magnetic field is implemented by: and permanent magnets are arranged at certain distance in the length direction of the short columnar array.
Preferably, in step S3, a glass sheet is further disposed on the surface of the permanent magnet close to the short columnar array for limiting the growth of the columnar top end.
The invention provides a micrometer column array with high length-diameter ratio, which is obtained by the preparation method, wherein the top end of the micrometer column array is smooth or in a sawtooth shape; the height of the micropillar array is uniform or grows in a gradient.
The invention provides application of the micropillar array obtained by the preparation method in the adhesive.
Compared with the prior art, the method firstly provides a hydrophobic template with a micropore array structure, and adopts a composite solution of Carbonyl Iron Powder (CIP) and PDMS to obtain a short column array structure in a semi-solidified state in advance through transfer printing; then under the action of an external magnetic field, the PDMS/CIP columnar structure grows along the length direction, and the micron-sized fiber structure with high length-diameter ratio is obtained after solidification. The invention can prepare the gecko claw-like fiber array by a simple, universal and cheap technology, can combine the advantages of the bottom-up and top-down methods, can conveniently obtain a high-length-diameter-ratio micron column array, and is beneficial to application in gecko-like adhesion.
Drawings
FIG. 1 is a schematic diagram of a reticle having an array of apertures according to some embodiments of the present invention;
FIG. 2 is a schematic illustration of a process for forming a PDM/CIP initial pre-cured stub structure according to some embodiments of the present invention;
FIG. 3 is a schematic illustration of a process for preparing an array of magnetically induced long micropillars in some embodiments of the present invention;
FIG. 4 is a SEM photograph (500 μm) of a stub array obtained after semi-curing and demolding in example 1 of the present invention;
FIG. 5 is a SEM photograph (400 μm) of a stub array obtained after semi-curing and demolding in example 1 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a preparation method of a high-length-diameter ratio micron column array, which comprises the following steps:
s1, providing a hydrophobic template with a micropore array structure;
mixing carbonyl iron powder and PDMS to obtain a composite solution;
s2, infiltrating the composite solution into the pore structure of the hydrophobic template, heating to form a semi-cured state, and demolding to obtain a short columnar array;
and S3, under the action of an external magnetic field, growing the short columnar array along the length direction, and curing to obtain the micron columnar array with high length-diameter ratio.
The method can prepare the micron column array with high length-diameter ratio, and the structure of the micron column array is relatively stable. Meanwhile, the invention has simple processing and lower cost.
In the embodiment of the invention, the hydrophobic template with the micron pore array structure is obtained by etching processing. Specifically, the hydrophobic template is prepared according to the following steps:
A. coating the photoresist on the surface of a hydrophilic substrate, and baking to obtain a substrate coated with the photoresist;
B. combining a micron-sized dot matrix structure mask plate, and carrying out ultraviolet exposure on the substrate after glue coating to form a structure pattern corresponding to the mask on the surface of the substrate;
C. sequentially developing, cleaning and baking the exposed substrate surface to obtain a porous template with a micron pore array structure;
D. and carrying out hydrophobic treatment on the porous template to obtain the hydrophobic template with a micron pore array structure.
In the process of preparing the template, the embodiment of the invention designs according to the diameter and the distance of the fibers in the micron-sized fiber array to be prepared, then conventionally prepares the mask with the micron-sized lattice structure, and carries out ultraviolet lithography for later use. Fig. 1 is a schematic diagram of a mask having an aperture array structure according to some embodiments of the present invention, the mask includes a plurality of circular units, each circular unit has a diameter of 100 microns and a pitch of 200 microns, the entire array is a1 cm square, and the shaded portion is a light-transmitting region.
In addition, in the embodiment of the present invention, it is preferable to clean a hydrophilic substrate such as a silicon substrate. For example, a commercially available silicon substrate is washed with acetone, isopropyl alcohol, and water (deionized water is commonly used in laboratories) in sequence; then, water molecules on the surface of the silicon substrate are removed through baking, and the silicon substrate can be naturally cooled to normal temperature.
In addition, after the substrate is cleaned and before the substrate is coated with the adhesive, the embodiment of the invention also coats the adhesion promoter on the surface of the substrate, so as to enhance the adhesion between the subsequent photoresist and the substrate. Wherein the adhesion promoter may be a commercially available product whose composition comprises an organosilicon compound (e.g., ALLRESIST, model AR300-80, germany, for enhancing adhesion between a photoresist and a silicon substrate); the coating can be carried out by a spin coating mode, and then the coating is baked and naturally cooled to the normal temperature.
The embodiment of the invention adopts commercially available photoresist, usually thick photoresist, such as photoresist SU-8 2050 of MICROCHEM company; and coating the photoresist on the surface of the substrate by using a spin coater, spreading the photoresist to 1/2 of the diameter of the substrate, and baking to obtain the substrate coated with the photoresist. Wherein, because the depth of structure can reach hundreds of microns, so need thick glue, SU8 is a thick glue of using always, has low absorption characteristic to the ultraviolet ray, and the exposure uniformity is better on the photoresist thickness, and the figure edge is nearly perpendicular, and the aspect ratio can reach 50:1, is a photoresist preferably used in the present application. And determining the glue thickness according to the depth of the required initial columnar structure, and then setting the rotating speed of the spin coater according to the glue thickness. The baking specifically comprises the following steps: placing the substrate coated with the glue solution on a hot plate, baking at 60-70 ℃ for 1-5min, baking at 90-100 ℃, closing the hot plate after 5-15min, and cooling to normal temperature; the specific parameters depend on the thickness of the glue.
After the glue is coated, the pre-designed and manufactured micron-sized lattice structure mask is combined, and an ultraviolet photoetching machine is adopted to carry out ultraviolet exposure in the embodiment of the invention. The micron-scale lattice structure mask comprises a plurality of circular units or a plurality of square units; the diameter of each circular cell is 50-100 microns, and the width of each square cell is 50-100 microns. Specifically, the exposure mode of the ultraviolet lithography machine can be selected from multiple exposure circulation for 3 times, and the single time lasts for 5-15s; and then continuing hot plate baking: firstly baking at 60-70 ℃ for 1-5min, and then baking at 90-100 ℃ for 5-15min, wherein the structural pattern is already seen. Then, the hot plate is closed and the substrate is cooled to normal temperature to obtain an exposed substrate; the specific parameters depend on the thickness of the glue.
The embodiment of the invention sequentially carries out developing, cleaning and baking on the surface of the exposed substrate to obtain the porous template with the micron pore array structure. The specific process comprises the following steps: developing for a certain time by using a developing solution corresponding to the photoresist, gradually developing the pattern, cleaning by using isopropanol, drying by using nitrogen, and transferring to a hot plate for baking. The baking segment is as follows: baking at 150-250 deg.C for 5-30min, baking at 90-100 deg.C for 5-15min, and baking at 60-70 deg.C for 1-5min. Then, the embodiment of the invention is cooled to normal temperature, and finally the hole array structure on the substrate is obtained and transferred for standby; the specific parameters depend on the thickness of the glue.
After the porous template is obtained, the embodiment of the invention carries out hydrophobic treatment on the porous template; the hydrophobic substance used in the treatment is preferably perfluorooctyltrichlorosilane (trichloro (1H, 2H-perfluorooctyl) silane), the structured silicon wafer is generally subjected to silanization treatment, and the contact angle after the treatment is specifically 103 degrees. For example, an appropriate amount of trichloro (1h, 2h-perfluorooctyl) silane is drawn by a micro syringe, mixed with alcohol in a dish at a volume ratio of 1.
In the aspect of preparing materials, the invention selects a compound of carbonyl iron powder and PDMS. Wherein the Carbonyl Iron Powder (CIP) has a chemical formula of Fe (CO) 5 The magnetic material is a good soft magnetic material and has high magnetization intensity; according to the embodiment of the invention, carbonyl iron powder with the particle size of 2.5 microns can be used as the magnetic particles. PDMS is polydimethylsiloxane, which is a straight-chain silicone oil for short in English. PDMS is used as a polymer matrix, is nontoxic and has excellent rheological property; when the mixed solution of carbonyl iron powder and PDMS is semi-cured, the magnetic rheological elastomer is a magnetorheological elastomer, has the fluidity of colloid and the magnetism of a solid magnetic material, and is convenient for subsequent operation.
Fig. 2 is a schematic diagram of a process for manufacturing a PDM/CIP initial semi-cured short column structure in an embodiment of the present invention, where in fig. 2, 1 is SU-8 photoresist, 2 is a PDMs/CIP solution, 3 is a silicon wafer, and 4 is a super-hydrophobic treatment solution, that is, a solution in which trichloro (1h, 2h-perfluorooctyl) silane and alcohol are mixed in a volume ratio of 1. In fig. 2, a. Carbonyl iron powder and PDMS are thoroughly mixed to obtain a PDMS/CIP solution; b. obtaining an SU-8 photoresist structure on a silicon wafer by utilizing a photoetching technology, soaking the structure in a super-hydrophobic treatment solution, and sealing and standing for 24H; c. pouring PDMS/CIP solution on SU-8 micron hole array, standing and spreading; and d, semi-curing and demolding PDMS/CIP to obtain the short micron column array.
According to the embodiment of the invention, carbonyl iron powder and PDMS are mixed to prepare the composite solution, and the mass ratio of the PDMS to the carbonyl iron powder can be (10-15): 5. in the examples of the present invention, dow Corning Sylgard 184PDMS was generally selected as the matrix, germany BASF SM carbonyl iron powder (CIP, particle size 2.5 μm) as the magnetic particles; specifically, the components of Dow Corning 184A and B (curing agent) and carbonyl iron powder are mixed in a ratio of 10:1:5, stirring uniformly, further dispersing the iron particles preferably by ultrasound for 10 minutes, and then evacuating the vacuum chamber for 30 minutes.
In the embodiment of the invention, the prepared composite solution is poured on the treated hydrophobic template, is kept stand and laid flat, and bubbles can be pumped in a vacuum cavity for 20 minutes, so that the solution is fully infiltrated into the pore structure of the template. According to the embodiment of the invention, a high-temperature adhesive is used for fixing the soaked sample on a heating table, and a certain temperature is set for heating to form a semi-solidification state; the heating temperature is preferably 70-90 ℃, and the heating time can be 30-60 seconds. After cooling, the short columnar structure array can be demoulded by slightly uncovering to obtain the semi-solidified short columnar structure array. Because the long diameter of the array structure is smaller, the demolding process is very easy, and the structure is not easy to damage.
According to the embodiment of the invention, a permanent magnet can be fixedly adsorbed at a certain distance in the length direction of the short columnar array to provide an external magnetic field; and fixing a glass sheet on the surface of the permanent magnet close to the short column array by using high-temperature glue. Specifically, the selected permanent magnet is a circular magnet with the diameter of neodymium iron boron being 20mm and the thickness being 3mm, the maximum magnetic field intensity is 300mT, the effect of adjusting the magnetic field to be 100-200mT is better by controlling the air gap between the magnet and the structure along with the distance attenuation.
In the embodiment of the invention, the distance between the permanent magnet and the fiber structure is adjusted (which can be adjusted in the range of hundreds of micrometers according to the required fiber length), and at this time, the magnetic field can elongate the semi-cured PDMS/CIP columnar structure in the length direction until the top growth of the glass sheet is limited, the semi-cured PDMS/CIP columnar structure is kept at room temperature for 5 minutes, and then the semi-cured PDMS/CIP columnar structure is heated to be completely cured, so that the cured micrometer column array is obtained.
The invention realizes the preparation of the high-length-diameter-ratio micrometer column array by utilizing a magnetic induction mode and combining a micro-nano processing technology. If direct magnetron growth is performed without obtaining a short columnar array in advance, the obtained array is difficult to be uniform in size and shape. The micron column array obtained by the invention has accurate shape and size and higher length-diameter ratio, and is also called a (micron) fiber array. The iron powder is doped, so that the rigidity is improved, the falling and the collapse are not easy to occur even if the length-diameter ratio is large, and the structure is stable.
Moreover, the PDMS/CIP short-column structure can move upwards to the top limit along the direction of the magnetic field by utilizing the induction action of an external magnetic field. The length and the top end appearance of the finally formed columnar structure are determined by external limitation, the height of the top end limitation distance from the fiber structure is adjusted to obtain a fiber array with a required length-diameter ratio, and the appearance of the fiber head can be changed by adjusting the appearance of the top end limitation glass sheet, which is also a difficult problem in the traditional processing mode. Compared with the traditional processing mode of which the structure is mainly determined by the template, the method adopting the external limitation is easier to operate, and the formed structure has wide range.
Fig. 3 is a schematic diagram of a process for preparing a magnetically induced long micro-pillar array according to an embodiment of the present invention, in fig. 3, 1 is a permanent magnet, 2 is a glass plate, 3 is a semi-cured PDMS/CIP short pillar, and 4 is a TEC cooler heating stage. In the embodiment of the invention, a semi-cured sample is placed on a TEC cooler heating table, and a pressure head of a universal testing machine adsorbing a permanent magnet and a glass sheet is moved to an ideal height position at room temperature; b. keeping the position until the short column is gradually deformed under the action of a magnetic field; c. the semi-solidified short column finally grows to the position of the glass sheet from the top under the action of a magnetic field; d. the glass sheet was peeled off to obtain the final long cylindrical sample. In fig. 3, the glass sheets a1-d1 are horizontally placed as smooth glass sheets, the glass sheets a2-d2 are horizontally placed as rough glass sheets with saw-tooth surfaces, and the glass sheets a3-d3 are obliquely placed as smooth glass sheets, which correspond to different top end structures.
The invention provides a high-length-diameter-ratio micron column array, which is obtained by the preparation method and mainly applied to gecko-like adhesion. The micropillar array may comprise a plurality of cylindrical fibers, or a plurality of cuboid fibers; wherein each fiber has a diameter of 50 to 100 microns. In some embodiments of the invention, the tips of the micropillar array are smooth or jagged. In some embodiments of the invention, the micropillar array is uniform in height or grows in a gradient.
In addition, the invention also provides application of the micropillar array obtained by the preparation method in an adhesive.
For further understanding of the present application, the high aspect ratio micropillar arrays provided herein, methods of making, and uses thereof are specifically described below with reference to the examples. It should be understood, however, that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention, which is defined by the following examples.
The raw materials in the following examples are all commercial products, wherein, the film plate materials are common molten glass and chromium; the silicon substrate is a single-polished silicon wafer with four-inch P-type 100 crystal orientation and the thickness of 525+ -20 microns; the tackifier was obtained from ALLresist and SU8 was obtained from MICROCHEM.
Example 1:
(1) Designing and manufacturing a dot matrix structure mask shown in figure 1, wherein the shape of fibers is set to be circular, the diameter of the fibers is set to be 100 micrometers, the distance between the fibers is set to be 200 micrometers, and the fiber array forms a square area with the side length of 1 centimeter;
(2) Cleaning a silicon substrate by acetone, isopropanol and deionized water in sequence, drying by using a nitrogen gun, setting a hot plate to be 180 ℃, baking the silicon substrate for 30 minutes to remove surface water molecules, and naturally cooling to normal temperature;
(3) Firstly, setting the rotating speed of a spin coater to 4000r/min for 30s, spin-coating a tackifier AR300-80, then baking at 180 ℃ for 2min, and naturally cooling to normal temperature;
(4) Selecting photoresist SU-8 2050 (referred to as SU-8 photoresist for short), standing for 1 hour, sucking the photoresist liquid by a suction pipe, slowly dripping the photoresist liquid on the surface of the silicon wafer tackified in the step (3), and spreading the silicon wafer to 1/2 of the diameter of the silicon wafer; the spin coater is set to a low speed of 600r/min for 15s, a high speed of 2500r/min for 50s, and then at 500r/min 2 The acceleration of the spin coating is reduced to 0, and the thickness of the spin-coated glue is about 50 microns;
(5) Baking the substrate coated with SU-8 glue with the thickness of 50 microns on a hot plate at 65 ℃ for 2min, then baking at 95 ℃ for 5min, and naturally cooling;
(6) The exposure mode of the ultraviolet lithography machine adopts multiexposure circulation for 3 times, the single time lasts for 6s, the hot plate baking is continued, the baking is carried out for 1min and 30s at 65 ℃, then the baking is carried out for 5min at 95 ℃, the structural graph is initially seen, the hot plate is closed, and the cooling is carried out to the normal temperature;
(7) Developing for about 6min by using SU-8 special developing solution, gradually displaying a graph, then cleaning for 20s by using isopropanol, drying by blowing with nitrogen, moving to a hot plate, baking for 5min at 150 ℃, baking for 5min at 95 ℃, baking for 1min at 65 ℃, cooling to normal temperature, finally obtaining an SU-8 hole array structure on a silicon substrate, and transferring for later use;
(8) Extracting a proper amount of trichloro (1H, 2H-perfluorooctyl) silane by a micro-injector, uniformly mixing the trichloro (1H, 2H-perfluorooctyl) silane with alcohol in a culture dish according to a volume ratio of 1;
(9) Dow Corning Sylgard 184PDMS was selected as the matrix, germany BASF SM type carbonyl iron powder (CIP, particle size 2.5 microns) was selected as the magnetic particles, dow Corning 184A, B (curing agent) components and iron powder were mixed in a ratio of 10:1:5, adding the mixture into a beaker in sequence, uniformly stirring, further performing iron particle dispersion treatment on the sample by using a Jie' e ultrasonic cleaning machine for 10 minutes, and then performing air suction and bubbling in a vacuum cavity for 30 minutes;
(10) Pouring the prepared composite solution onto the hydrophobic template treated in the step (8), standing and flatly paving, and exhausting bubbles in a vacuum cavity for 20 minutes to enable the solution to be fully soaked into a pore structure;
(11) Fixing the soaked sample on a heating table of a TEC cooler by using a high-temperature adhesive tape, setting the temperature of the TEC cooler to be 80 ℃, heating for 60 seconds to obtain a semi-cured PDMS/CIP compound, cooling, slightly uncovering, and demolding to obtain a short columnar structure, wherein the specific appearance of the short columnar structure is shown in FIGS. 4 and 5;
(12) Fixing a TEC cooler sample table (4 cm x 0.5 cm) on a sample table of a universal material testing machine by using high-temperature glue, adsorbing and fixing a permanent magnet (3 cm x 0.5cm neodymium iron boron) on a vertical pressure head of the universal material testing machine, fixing a smooth glass sheet on the surface of the permanent magnet by using the high-temperature glue, adjusting the distance between the pressure head and a fiber structure (the distance can be adjusted within a hundred-micron range according to the required fiber length), ensuring the position level, lengthening a PDMS/CIP columnar structure in the length direction by using a magnetic field until the glass sheet limits the growth of the top end of the PDMS/CIP columnar structure, keeping the temperature for 5 minutes at room temperature, adjusting the TEC cooler to 100 ℃, heating for 40 minutes, completely curing, taking down a fiber sample, and obtaining a cylindrical fiber array with the diameter of 100 microns and the distance of 200 microns and smooth and level top ends.
Example 2:
based on example 1, a dot matrix structure mask is designed and manufactured in step (1), the fiber shape is set to be circular, the fiber diameter is set to be 50 micrometers, the fiber interval is set to be 100 micrometers, the fiber array forms a square area with the side length of 1 centimeter, and a top smooth and flush cylindrical fiber array with the diameter of 50 micrometers and the interval of 100 micrometers is obtained. For a fiber 50 micron in diameter, adjusting the indenter and fiber structure distance to 300 microns, an aspect ratio of 6:1, in a fiber array.
Example 3:
based on example 1, a dot matrix structure mask is designed and manufactured in step (1), the shape of the fibers is set to be square, the diameter of the fibers is set to be 100 micrometers, the distance between the fibers is set to be 200 micrometers, the fiber array forms a square area with the side length of 1 centimeter, and a cuboid fiber array with the smooth top and the flat top and the diameter of 100 micrometers and the distance of 200 micrometers is obtained.
Example 4:
based on example 1, in step (12), a TEC cooler sample stage (4 cm × 0.5 cm) is fixed to the sample stage of the universal material testing machine by using a high temperature adhesive, a permanent magnet (3 cm × 0.5cm neodymium iron boron) is fixed to a vertical pressure head of the universal material testing machine by adsorption, a serrated surface rough glass sheet is fixed to the surface of the permanent magnet by using the high temperature adhesive, the distance between the pressure head and the fiber structure is adjusted (the distance can be adjusted in a range of hundreds of micrometers according to the required fiber length), and the position level is ensured, at this time, the magnetic field can semi-solidify the PDMS/CIP columnar structure in the length direction until the glass sheet restricts the growth of the top end of the glass sheet, the TEC is kept for 5 minutes at room temperature, then the cooler is adjusted to 100 ℃ and heated for 40 minutes to be completely solidified, and the fiber sample is taken down, so that a cylindrical fiber array with a fiber head sawtooth morphology of 100 micrometers in diameter and 200 micrometers in spacing is obtained.
Example 5:
based on example 1, in step (12), a TEC cooler sample stage (4 cm × 0.5 cm) is fixed to the sample stage of the universal material testing machine by using a high temperature adhesive, a permanent magnet (3 cm × 0.5cm neodymium iron boron) is fixed to a vertical pressure head of the universal material testing machine by adsorption, a smooth surface glass sheet is fixed to the surface of the permanent magnet by using the high temperature adhesive, the distance between the pressure head and the fiber structure is adjusted (which can be adjusted within a hundred micrometers according to the required fiber length), the position of the pressure head is tilted, at this time, the magnetic field can semi-cure the PDMS/CIP columnar structure in the length direction until the glass sheet restricts the growth of the top end of the glass sheet, the TEC is kept for 5 minutes at room temperature, then the cooler is adjusted to 100 ℃ and heated for 40 minutes to be completely cured, and the fiber sample is taken down, so that a cylindrical fiber array with a smooth fiber head diameter of 100 micrometers and a distance of 200 micrometers and a gradient growth height is obtained.
From the above examples, it can be seen that the invention can prepare gecko claw-like fiber arrays by a simple, versatile, and inexpensive technique, which can combine the advantages of the bottom-up and top-down methods, and can conveniently obtain high aspect ratio micropillar arrays, facilitating application in gecko-like adhesion.
The above description is only a preferred embodiment of the present invention, and it should be noted that various modifications to these embodiments can be implemented by those skilled in the art without departing from the technical principle of the present invention, and these modifications should be construed as the scope of the present invention.
Claims (7)
1. A preparation method of a high-length-diameter-ratio micropillar array comprises the following steps:
s1, providing a hydrophobic template with a micropore array structure;
mixing carbonyl iron powder and PDMS to obtain a composite solution; the mass ratio of the PDMS to the carbonyl iron powder is (10-15): 5;
s2, infiltrating the composite solution into the pore structure of the hydrophobic template, heating to form a semi-cured state, and demolding to obtain a short columnar array; the heating temperature is 70-90 ℃, and the heating time is 30-60 seconds;
s3, under the action of an external magnetic field, enabling the short columnar array to grow along the length direction, and solidifying to obtain a micrometer columnar array with a high length-diameter ratio; the external magnetic field is realized in the following mode: and a permanent magnet is arranged at a certain distance in the length direction of the short columnar array, and the magnetic field intensity is adjusted to be 100-200mT.
2. The method according to claim 1, wherein in step S1, the hydrophobic template is prepared by:
A. coating the photoresist on the surface of a hydrophilic substrate, and baking to obtain a substrate coated with the photoresist;
B. combining a micron-sized dot matrix structure mask plate, and carrying out ultraviolet exposure on the substrate after glue coating to form a structure pattern corresponding to the mask on the surface of the substrate;
C. sequentially developing, cleaning and baking the exposed substrate surface to obtain a porous template with a micron pore array structure;
D. and carrying out hydrophobic treatment on the porous template to obtain the hydrophobic template with a micron pore array structure.
3. The method according to claim 2, wherein when the hydrophobic template is prepared in step S1, the micron-sized lattice structure mask comprises a plurality of circular cells or a plurality of square cells; the maximum width of each circular or square cell is 50-100 microns.
4. The method according to claim 2, wherein the hydrophobic template is prepared in step S1 by hydrophobic treatment with perfluorooctyltrichlorosilane.
5. The method according to claim 1, wherein in step S3, a glass plate is further disposed on the surface of the permanent magnet near the short columnar array for limiting the growth of the columnar tips.
6. A high aspect ratio micropillar array obtained by the method of any one of claims 1 to 5, the tip of the micropillar array having a smooth or jagged morphology; the height of the micropillar array is uniform or grows in a gradient.
7. Use of the micropillar array obtained by the method according to any one of claims 1 to 5 in adhesives.
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| CN112202366B (en) * | 2020-10-29 | 2021-10-08 | 吉林大学 | Low-frequency ultralow-wind-speed flexible wind power converter and preparation method thereof |
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| CN115010976A (en) * | 2022-06-07 | 2022-09-06 | 泰州市创新电子有限公司 | Super-hydrophobic bionic nano coating for display support frame and preparation method thereof |
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