CN110642222A - 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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- CN110642222A CN110642222A CN201910931954.7A CN201910931954A CN110642222A CN 110642222 A CN110642222 A CN 110642222A CN 201910931954 A CN201910931954 A CN 201910931954A CN 110642222 A CN110642222 A CN 110642222A
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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-solidified state, and demolding to obtain a short columnar array; s3, under the action of an external magnetic field, the short columnar array grows along the length direction, and the solidification is carried out 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 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.
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 a gecko-like dry adhesive (Sethi S, Ge L, Ci L, et al, Gecko-embedded carbon nanotube-based self-cleaning compositions [ 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 accessed microwells and on cured surfaces via a hierachical perfluor other stages [ 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 hole structure of the hydrophobic template, heating to form a semi-solidified state, and demolding to obtain a short columnar array;
s3, under the action of an external magnetic field, the short columnar array grows along the length direction, and the solidification is carried out 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 cells or a plurality of square cells; the maximum width of each circular unit or each square unit is 50-100 micrometers.
Preferably, when the hydrophobic template is prepared in step S1, the hydrophobic treatment is performed with perfluorooctyltrichlorosilane.
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, the surface of the permanent magnet close to the stub array is further provided with a glass sheet for limiting the growth of the stub tip.
The invention provides a high-length-diameter-ratio micron column array, which is obtained by the preparation method, wherein the top end of the micron column array is in a smooth or 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 diagram of a process for fabricating a PDM/CIP initial semi-cured stub structure according to some embodiments of the present disclosure;
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 hole structure of the hydrophobic template, heating to form a semi-solidified state, and demolding to obtain a short columnar array;
s3, under the action of an external magnetic field, the short columnar array grows along the length direction, and the solidification is carried out 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 including a plurality of circular units, each circular unit having a diameter of 100 micrometers and a pitch of 200 micrometers, the entire array having a square shape of 1 cm, and the shaded portions being light-transmissive regions.
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-82050 manufactured by 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 commonly used thick glue, 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 for 1-5min at 60-70 ℃, then 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 unit is 50-100 micrometers, and the width of each square unit is 50-100 micrometers. 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 5-15 s; and then continuing hot plate baking: 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 250 ℃ for 5-30min at 150-. 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 perfluorooctyl trichlorosilane (trichloro (1H,1H,2H, 2H-perfluorooctyl) silane), the structural silicon wafer is generally subjected to silanization treatment, and the contact angle after the treatment is specifically 103 degrees. For example, a proper amount of trichloro (1H, 2H-perfluorooctyl) silane is pumped by a micro syringe, and is uniformly mixed with alcohol in a volume ratio of 1:100 in a culture dish, the obtained porous template is placed in the mixed solution for soaking, sealed and kept stand, and kept at room temperature for 24 hours, so that the hydrophobic template with the micropore array structure is obtained.
In the aspect of preparing materials, the invention selects a compound of carbonyl iron powder and PDMS. Wherein the carbonyl iron powder (CI)P) is of the formula Fe (CO)5The 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 fabricating a PDM/CIP initial semi-cured stub structure in an embodiment of the present invention, in FIG. 2, 1 is SU-8 photoresist, 2 is PDMS/CIP solution, 3 is a silicon wafer, and 4 is a super-hydrophobic treatment solution, i.e., a solution in which trichloro (1H,1H,2H, 2H-perfluorooctyl) silane and alcohol are mixed in a volume ratio of 1: 100. 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 the PDMS/CIP solution on an SU-8 micron pore array, standing and flatly paving; 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, 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. The embodiment of the invention utilizes high-temperature glue to fix the soaked sample on a heating table, and the sample is heated at a certain temperature to form a semi-solidified 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 20mm and the thickness of 3mm of neodymium iron boron, 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 microns according to the required fiber length), at this time, the magnetic field can elongate the semi-cured PDMS/CIP columnar structure in the length direction until the glass sheet restricts the growth of the top end thereof, 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 micron 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 appearance of the finally formed columnar structure are determined by external limitation, the fiber array with the needed length-diameter ratio can be obtained by adjusting the height of the top limitation distance from the fiber structure, and the appearance of the fiber head can be changed by adjusting the appearance of the top 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 specific embodiment of the invention, a, placing a semi-cured sample on a TEC cooler heating table, and moving a universal testing machine pressure head adsorbing a permanent magnet and a glass sheet to an ideal height position at room temperature; b. the short column is kept at 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 arranged as smooth glass sheets, the glass sheets a2-d2 are horizontally arranged as rough glass sheets with sawtooth surfaces, and the glass sheets a3-d3 are obliquely arranged as smooth glass sheets, and the three glass sheets 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 is mainly applied to gecko-like adhesion. The micropillar array may comprise a plurality of cylindrical fibers, or a plurality of cuboid fibers; wherein the diameter of each fiber is 50-100 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 the 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; tackifiers were purchased from ALLresist, SU8 from MICROCHEM corporation.
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) sequentially cleaning acetone, isopropanol and deionized water on a silicon substrate, 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-82050 (SU-8 glue for short), standing for 1 hour, sucking the glue solution by a suction pipe, slowly dripping the glue solution 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/min2The acceleration 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 a multiple exposure cycle for 3 times, the single time lasts for 6s, the hot plate baking is continued, the baking is carried out for 1min30s at 65 ℃, then the baking is carried out for 5min at 95 ℃, the structural pattern is initially seen, then the hot plate is closed, and the cooling is carried out to the normal temperature;
(7) developing for about 6min by using an SU-8 special developing solution, gradually displaying a graph, then cleaning for 20s by using isopropanol, drying by using 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,1H,2H, 2H-perfluorooctyl) silane by using a micro-injector, uniformly mixing the trichloro (1H,1H,2H, 2H-perfluorooctyl) silane and alcohol in a culture dish according to the volume ratio of 1:100, placing the obtained SU-8 porous template into a solution for soaking, sealing and standing, and keeping the solution at room temperature for 24 hours to obtain a hydrophobic template after super-hydrophobic treatment;
(9) dow Corning Sylgard 184PDMS was chosen as the matrix, Germany BASF SM carbonyl iron powder (CIP, particle size 2.5 microns) as the magnetic particles, Dow Corning 184A, B (curing agent) component and iron powder were mixed at 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 (4cm x 0.5cm) on a sample table of a universal material testing machine by using high-temperature glue, fixing a permanent magnet (3cm x 0.5cm neodymium iron boron) on a vertical pressure head of the universal material testing machine in an adsorbing manner, 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 to be horizontal, lengthening a semi-cured 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 semi-cured PDMS/CIP columnar structure, keeping the semi-cured PDMS/CIP columnar structure for 5 minutes at room temperature, adjusting the TEC cooler to 100 ℃, heating for 40 minutes for complete curing, taking down a fiber sample, and obtaining a cylindrical fiber.
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 the step (1), the fiber shape is set to be square, the fiber diameter is set to be 100 micrometers, the fiber interval 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 and level top end and the diameter of 100 micrometers and the interval of 200 micrometers is obtained.
Example 4:
based on example 1, in step (12), a TEC cooler sample stage (4cm × 0.5cm) was fixed to the sample stage of a universal material testing machine by using a high temperature adhesive, a permanent magnet (3cm × 0.5cm neodymium iron boron) was fixed to a vertical indenter of the universal material testing machine by adsorption, a serrated surface-roughened glass sheet was fixed to the surface of the permanent magnet by using a high temperature adhesive, the distance between the indenter and the fiber structure was adjusted (which can be adjusted in the range of one hundred micrometers depending on the desired fiber length), and the position is ensured to be horizontal, at the moment, the magnetic field can elongate the semi-cured PDMS/CIP columnar structure in the length direction until the growth of the top end of the glass sheet is limited, the glass sheet is kept for 5 minutes at room temperature, and then adjusting the TEC cooler to 100 ℃, heating for 40 minutes and completely curing, and taking down the fiber sample to obtain the cylindrical fiber array with the fiber head sawtooth morphology, wherein the diameter of the cylindrical fiber array is 100 micrometers, and the distance between the cylindrical fiber array and the fiber head sawtooth morphology is 200 micrometers.
Example 5:
based on example 1, in step (12), a TEC cooler sample stage (4cm × 0.5cm) was fixed to the sample stage of a universal material testing machine by using a high temperature adhesive, a permanent magnet (3cm × 0.5cm neodymium iron boron) was fixed to a vertical indenter of the universal material testing machine by adsorption, a smooth surface glass sheet was fixed to the surface of the permanent magnet by using a high temperature adhesive, the distance between the indenter and the fiber structure was adjusted (which can be adjusted in the range of hundred micrometers depending on the desired fiber length), and the position of the pressure head is inclined, at the moment, the magnetic field can elongate the semi-cured PDMS/CIP columnar structure in the length direction until the growth of the top end of the glass sheet is limited, the temperature is kept for 5 minutes at room temperature, and then adjusting the TEC cooler to 100 ℃, heating for 40 minutes and completely curing, and taking down the fiber sample to obtain a cylindrical fiber array with smooth fiber heads with the diameter of 100 micrometers and the spacing of 200 micrometers and with the height growing in a gradient manner.
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 (10)
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;
s2, infiltrating the composite solution into the hole structure of the hydrophobic template, heating to form a semi-solidified state, and demolding to obtain a short columnar array;
s3, under the action of an external magnetic field, the short columnar array grows along the length direction, and the solidification is carried out to obtain the micron columnar array with high length-diameter ratio.
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 unit or each square unit is 50-100 micrometers.
4. The method according to claim 2, wherein the hydrophobic template is prepared in step S1 by performing a hydrophobic treatment using perfluorooctyltrichlorosilane.
5. The preparation method according to claim 1, wherein when the composite solution is prepared in step S1, the mass ratio of the PDMS to the carbonyl iron powder is (10-15): 5.
6. the method according to claim 1, wherein the heating temperature in step S2 is 70 to 90 ℃, and the heating time is 30 to 60 seconds.
7. The method according to claim 1, wherein 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.
8. The method as claimed in claim 7, wherein in step S3, the surface of the permanent magnet close to the stub array is further provided with a glass plate for limiting the growth of the stub tip.
9. A high-aspect-ratio micropillar array obtained by the preparation method of any one of claims 1 to 8, wherein the top end of the micropillar array has a smooth or sawtooth shape; the height of the micropillar array is uniform or grows in a gradient.
10. Use of the micropillar array obtained by the preparation method according to any one of claims 1 to 8 in an adhesive.
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