Soft mold preparation method for non-deployable curved surface conformal imprinting

Abstract

The invention belongs to the technical field of composite soft mold manufacturing and nanoimprint, and particularly relates to a soft mold preparation method for non-deployable curved surface conformal imprint. Firstly, the female die is manufactured, then the needed composite soft die (a supporting layer and a structural layer) is manufactured through the two-stage copying technology, the method is simple and easy to operate, the copied soft die is not spliced and can be in perfect conformal contact with an imprinting base material, the soft die can be repeatedly used, and cost is saved.

Description

Technical Field

[0001] The present application belongs to the technical field of composite soft mold manufacturing and nanoimprinting, and specifically relates to a method for preparing a soft mold for conformal imprinting of a non-developable surface. Background Art

[0002] As an advanced manufacturing technology, surface conformal embossing can solve the limitations of traditional manufacturing methods on curved substrates, such as the shortcomings of traditional etching processes such as photolithography, electron beam, ion beam, and printing processes such as screen printing, soft printing, and nanoimprinting in curved electronic manufacturing. This technology uses physical contact to accurately conformally emboss molds with micro-nano structures onto the surface of the material to be processed, thereby achieving rapid and large-area replication of micro-nanoscale patterns. It not only has the characteristics of high precision and high efficiency, but also can greatly reduce production costs, providing strong support for the mass production of micro-nano devices. It has demonstrated its unique advantages in many fields such as semiconductor manufacturing, optoelectronic devices, biomedicine, and microfluidic chips.

[0003] However, the core of curved surface conformal imprinting technology lies in the manufacture of conformal molds. As the "blueprint" in the imprinting process, the quality and precision of the mold directly determine the accuracy and stability of the imprinted pattern. Although traditional hard molds (such as silicon molds, metal molds, etc.) have high rigidity and durability, their manufacturing difficulty and cost are significantly increased when facing complex curved surfaces, large areas or high precision requirements. In addition, hard molds are prone to stress concentration during the imprinting process, resulting in mold damage or distortion of the imprinted pattern. In contrast, soft molds (such as polydimethylsiloxane (PDMS) molds, polyurethane molds, etc.) are gradually favored in nanoimprinting technology because of their good flexibility, plasticity and low cost characteristics, as well as their ability to easily adapt to various non-flat substrates, reduce stress concentration during the imprinting process, and improve the uniformity and stability of the imprinted pattern. However, a major challenge facing the current three-dimensional curved surface nanoimprinting and micro-nano patterning technology is how to manufacture large-size (especially non-spliced) three-dimensional non-developable curved surface conformal imprinting micro-nano soft molds. Existing micro-nano manufacturing technologies such as electron beam lithography, focused ion beam manufacturing and interference lithography are not only costly and time-consuming to manufacture large-scale non-jointed micro-nano molds, but also have limited patterning area. In particular, it is difficult for existing technologies to achieve the manufacture of non-jointed micro-scale soft molds for conformal imprinting of three-dimensional non-developable surfaces, which has become a key technical bottleneck hindering the widespread industrial application of three-dimensional non-developable surface conformal nanoimprinting and micro-nano patterning technology.

[0004] In summary, it is difficult to manufacture high-precision curved surface imprinting molds with existing technologies, especially for large-scale non-spliced ​​micro-nano soft molds that are urgently needed for conformal imprinting of large-scale non-expandable curved surfaces, which seriously restricts the widespread engineering application of conformal imprinting of non-expandable curved surfaces. Therefore, it is urgent to develop new technologies and processes for the preparation of large-scale non-spliced ​​micro-nano soft molds for conformal imprinting of non-expandable curved surfaces, so as to achieve efficient and low-cost manufacturing of large-scale non-spliced ​​complex curved surface micro-nano soft molds.

[0005] The information in this background technology section is only intended to enhance the understanding of the overall background of the application and should not be construed as an admission or any form of suggestion that the information constitutes the prior art already known to a person of ordinary skill in the art. Summary of the invention

[0006] In order to solve the above problems, the purpose of this application is to provide a method for preparing a non-spliced ​​micro-nano soft mold for conformal embossing of non-developable surfaces, so as to solve the technical difficulties in manufacturing three-dimensional non-developable surface conformal embossing soft molds.

[0007] In some embodiments of the present application, a method for preparing a soft mold for conformal imprinting of a non-developable surface is provided, comprising the following steps:

[0008] Step 1: Substrate Pretreatment

[0009] Clean and dry the printed substrate to ensure that there are no impurities on the surface of the substrate;

[0010] Step 2: Print the Master Template

[0011] According to the characteristic graphic structure required by the imprinting mold, a micro-nano characteristic graphic structure is printed on a non-developable curved surface substrate as a master template;

[0012] Step 3: Make the intermediate soft mold

[0013] First, a liquid intermediate material is poured onto a master mold and solidified, and then the solidified flexible intermediate mold is removed from the non-developable curved surface substrate, and then the sacrificial structure of the master mold is removed to obtain an intermediate soft mold; optionally, in order to facilitate the subsequent demolding of the imprinted soft mold, the surface of the intermediate soft mold can be treated with anti-adhesion, and a layer of low surface energy material can be sprayed or deposited on its surface;

[0014] Step 4: Copy the embossing soft mold

[0015] First, the replication material is poured onto the intermediate soft mold prepared in step 3 and cured, and then the cured flexible imprinting mold is removed from the substrate to obtain an imprinting soft mold with the same structure as the printed master template.

[0016] Step 5: Mold post-processing

[0017] The inner and outer surfaces of the embossed soft mold produced in step 4 are turned over, and the surface of the embossed soft mold is treated with anti-adhesion to prevent demolding difficulties during the three-dimensional curved surface conformal embossing process; optionally, a backing support layer is attached to the outer surface of the embossed soft mold.

[0018] In some embodiments of the present application, the printing process in step 2 is five-axis linkage electric field driven melt jet micro-nano 3D printing.

[0019] In some embodiments of the present application, the material for printing the characteristic graphic structure in step 2 includes thermoplastic materials such as polycaprolactone (PCL), polylactic acid (PLA), polyvinyl alcohol (PVA), and water-soluble PEG / PEO composite materials.

[0020] In some embodiments of the present application, the liquid intermediate material used in step 3 includes polydimethylsiloxane (PDMS), fluoropolymer, silicone rubber, UV resin and corresponding materials doped with conductive particles (silver, copper, etc.).

[0021] In some embodiments of the present application, the intermediate soft mold curing method in step 3 includes UV curing, heating curing, etc.

[0022] In some embodiments of the present application, in step 3, the method for removing the sacrificial structure of the master mold includes solvent dissolution, heating and melting, ultrasonic cleaning, etc.

[0023] In some embodiments of the present application, in step 4, the replication material includes polydimethylsiloxane (PDMS), fluoropolymer, silicone rubber, UV resin and corresponding materials doped with conductive particles (silver, copper, etc.).

[0024] In some embodiments of the present application, in step 4, the imprint soft mold curing method includes UV curing, heating curing, etc.

[0025] In some embodiments of the present application, the backing support layer in step 5 can be made of polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), conductive PET, etc.

[0026] In other embodiments of the present application, a large-sized non-spliced ​​complex curved micro-nano soft mold is also provided, which is prepared by the above-mentioned preparation method.

[0027] In some further embodiments of the present application, a method for preparing a non-developable curved surface micro-conformal circuit is also provided, which is prepared using the above-mentioned large-size non-spliced ​​complex curved surface micro-nano soft mold.

[0028] In some embodiments of the present application, the above-mentioned soft mold is used to cover a curved substrate, an embossing glue is set in the middle, and a circuit pattern is conformally embossed and etched to obtain a groove structure consistent with the circuit geometry on the curved substrate. Then, a seed layer is filled in the groove, and the groove is filled with a highly conductive metal using an electroplating process. Subsequently, the heterogeneous metal in the groove is melt-strengthened, and after the metal is cooled, an interlocking structure is formed with the roughened microstructure in the groove. The sample is post-processed to obtain a conformal circuit.

[0029] In some embodiments of the present application, applying embossing glue on the surface of the curved substrate and embossing a circuit pattern comprises the following steps:

[0030] (1) coating a layer of embossing adhesive on the surface of the substrate;

[0031] (2) aligning the manufactured imprint soft mold with the curved substrate and applying pressure to achieve conformal contact between the soft mold and the curved substrate;

[0032] (3) Replicate the soft mold structure on the imprint glue and reduce the thickness of the residual layer by applying air pressure and electric field force;

[0033] (4) releasing the embossing force, maintaining the shape for a period of time, and then curing the embossing glue;

[0034] (5) After the embossing adhesive is completely cured, the soft mold is separated from the embossed pattern by peel-off demolding, thereby achieving efficient and high-precision preforming of three-dimensional graphics.

[0035] In some embodiments of the present application, the etching specifically includes the following steps:

[0036] (1) Removing the embossing residual layer;

[0037] (2) using the photoresist of the replicated pattern as a mask, and using wet etching to etch a circuit pattern groove in the curved substrate;

[0038] (3) removing the photoresist;

[0039] (4) Roughening the grooves of the curved substrate to form irregular micro-nano structures in the grooves; and determining whether to further modify the grooves to achieve super-hydrophilicity according to needs.

[0040] In some embodiments of the present application, filling the groove with a seed layer comprises the following steps:

[0041] (1) Using nano conductive ink material as printing material, filling the nano conductive material ink into the nano groove;

[0042] (2) The nano-conductive ink filled in the nano-grooves is sintered and made conductive to complete the manufacture of the nano-seed layer.

[0043] In some embodiments of the present application, the electroplating process includes the following steps:

[0044] The conductive metal is continuously electroplated and deposited on the seed layer of the groove of the curved substrate to completely fill the nanogrooves of the curved substrate with the metal material.

[0045] In some embodiments of the present application, melting and strengthening the heterogeneous metal in the groove includes the following steps:

[0046] (1) Fixing the electroplated workpiece at a preset position;

[0047] (2) Using a laser, the electroplated conductive metal and the seed layer are heated and melted according to the planned circuit pattern printing path. The molten metal is completely filled into the micro-nano structure of the roughened groove. After the metal cools, an interlocking structure is formed between the metal and the roughened nanogroove heterogeneous interface. The interlocking structure is used to achieve strong adhesion between the metal pattern and the substrate.

[0048] In some embodiments of the present application, the post-processing comprises the following steps:

[0049] The excess metal material outside the nanogrooves of the curved substrate and the part of the metal filling the nanogrooves of the curved substrate that protrudes above the surface of the substrate are removed to complete the manufacture of the curved conformal circuit on the curved substrate.

[0050] Compared with the prior art, this application has at least the following advantages:

[0051] (1) The present application can realize high-precision manufacturing of arbitrary sub-microscale two-dimensional pattern molds.

[0052] (2) It can realize the rapid and low-cost manufacturing of non-spliced ​​non-developable surfaces and complex three-dimensional micro-nano molds with multiple curvatures, and has the outstanding characteristics of low manufacturing cost and high efficiency.

[0053] (3) The mold manufactured in this application has high shape retention and good conformality.

[0054] (4) This method has high scalability and flexibility and is suitable for mass production.

[0055] (5) The present application can combine five-axis linkage electric field driven melt jet micro-nano 3D printing and two-stage replication technology to realize the manufacture of high-precision, high-efficiency and high-reliability three-dimensional non-developable surface conformal embossing soft molds, especially having the unique advantage of being able to realize the rapid and low-cost manufacturing of non-spliced ​​three-dimensional non-developable surfaces and complex three-dimensional micro-nano molds with multiple curvatures.

[0056] The present application provides a new solution for the manufacture of non-spliced ​​three-dimensional non-developable curved surface micro-nano molds required in the field of curved surface conformal nanoimprinting, especially for the manufacture of structures such as drones, missiles, radar antenna covers, aircraft hatches, etc. with special functions. It provides a new solution with broad industrial application prospects, and has the unique advantages of high precision, no splicing, low cost and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0058] Figure 1 The present invention provides a method for preparing a soft mold for conformal imprinting of a non-developable surface in some embodiments of the present application.

[0059] Figure 2 It is a schematic diagram of the principle of five-axis linkage electric field driven melt jet micro-nano 3D printing in some embodiments of the present application.

[0060] Figure 3 It is a schematic flow chart of a method for preparing a soft mold for conformal imprinting of a non-developable surface in some embodiments of the present application. DETAILED DESCRIPTION

[0061] In order to enable those skilled in the art to better understand the technical solution of the present disclosure, the present disclosure is described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0062] All terms (including technical terms or scientific terms) used in the present disclosure have the same meanings as those understood by ordinary technicians in the field to which the present disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries, such as general dictionaries, should be interpreted as having meanings consistent with their meanings in the context of the relevant technology, and should not be interpreted in an idealized or extremely formal sense, unless explicitly defined herein.

[0063] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0064] The following is combined with Figure 1-3 To illustrate the detailed technical solution of this application.

[0065] In some embodiments of the present application, the present application realizes a method for manufacturing a splicing-free three-dimensional curved surface conformal imprinting soft mold as follows: first, a five-axis linkage electric field-driven melt-jet micro-nano 3D printing is used to manufacture a master mold, so as to realize efficient and low-cost manufacturing of a large-size conformal master template for replicating composite soft molds, and the molding accuracy can reach up to sub-micro scale; then, the required composite soft mold (support layer and structural layer) is manufactured through a two-stage replication technology. The method is simple and easy to operate, the replica soft mold has no splicing, can be in perfect conformal contact with the imprinting substrate, and the soft mold can be reused, saving costs.

[0066] In some embodiments of the present application, the five-axis linkage electric field driven melt jet micro-nano 3D printing device is as follows Figure 2 As shown, an annular heater is arranged on the periphery of the barrel, and the printing material in the barrel is heated and melted into liquid, which is ejected from the nozzle under the action of gas pressure. A needle heater is arranged at the nozzle, and a high-voltage DC power supply is connected to the nozzle, and an electric field is formed between the nozzle and the receiving substrate, inducing charges to gather at the nozzle and repel each other. The strong electric field force causes the liquid at the nozzle to form a Taylor cone. When the sum of the electric field force and the gas back pressure is greater than the sum of the surface tension and the viscosity force, droplets are ejected from the tip of the Taylor cone to print the target pattern on the curved substrate.

[0067] In some embodiments of the present application, a five-axis linkage electric field driven melt jet micro-nano 3D printing device may adopt the device as described in CN202210327898.8 or CN201811018667.9.

[0068] In some embodiments of the present application, a five-axis linkage electric field driven melt jet micro-nano 3D printer is used to print polycaprolactone (PCL) on a spherical curved substrate as a master template, and the manufactured graphic structure is a wire grid structure, and then a secondary mold is used to replicate the imprinted working soft mold. Figure 1 As shown, the specific preparation steps include:

[0069] (1) Substrate pretreatment

[0070] Spherical ceramics are used as the substrate for manufacturing the master template. The substrate is cleaned and dried before printing to ensure that there are no impurities on the surface of the substrate.

[0071] (2) Printing the master template

[0072] Polycaprolactone (PCL) is used as the printing material. According to the micro-nano mold graphic structure to be manufactured, a five-axis linkage electric field driven melt jet micro-nano 3D printer is used to manufacture the master mold structure on the ceramic substrate. The printing principle is as follows Figure 2 shown.

[0073] The microstructure size of the master template is: line width 200nm, period 10μm, height 150nm wire grid structure, such as Figure 1 As shown in a.

[0074] (3) Making the intermediate soft mold

[0075] First, pour liquid PDMS onto the master mold and cure it at 100°C for 30 minutes. Then, remove the cured flexible PDMS intermediate mold from the substrate by a peel-off demolding method. Finally, soak the intermediate mold in dimethylformamide (DMF) for 30 minutes to completely remove the sacrificial structure of the master mold remaining during the demolding process. Then, place the intermediate mold in alcohol and perform ultrasonic treatment for 10 minutes. Then, place the intermediate mold in deionized water and perform ultrasonic treatment for 10 minutes. Finally, blow dry with nitrogen to obtain an intermediate soft mold (the inner surface is a wire grid groove structure with a line width of 200nm, a period of 10μm, and a depth of 150nm). In order to facilitate the smooth demolding of the subsequent imprinted soft mold, the surface of the intermediate mold can be treated with anti-adhesion, and a layer of low surface energy material, such as spray or deposit on its surface. Figure 1 As shown in b.

[0076] (4) Replica embossing soft mold

[0077] First, the replication material (fluoropolymer) is poured onto the intermediate mold prepared in step 3 and cured at 100°C for 1 hour. Then, the cured flexible imprint mold is removed from the substrate by a peel-off demoulding method to obtain an imprint soft mold with the same structure as the printed master template. The outer surface of the replicated structure is a wire grid protrusion structure with a line width of 200nm, a period of 10μm, and a height of 150nm, as shown in FIG. Figure 1 As shown in c.

[0078] (5) Mold post-processing

[0079] The inner and outer surfaces of the imprinted soft mold made in step 4 are flipped over. After flipping, the outer surface is a smooth spherical surface, and the inner surface is a wire grid protrusion structure with a line width of 200nm, a period of 10μm, and a height of 150nm. To prevent the difficulty of demolding during the conformal imprinting of three-dimensional curved surfaces, the surface of the imprinted soft mold is treated with anti-adhesion. First, the imprinted soft mold is cleaned, ultrasonically treated with acetone for 10 minutes; ultrasonically cleaned with deionized water for 10 minutes; ultrasonically treated with isopropanol for 10 minutes; ultrasonically treated with isooctane for 10 minutes; with isooctane as the solvent, a 2% concentration of heptadecafluorodecyltrichlorosilane solution (FDTS) is prepared and allowed to stand for 20 minutes; then, the master template is placed in it and soaked for 20 minutes; then, it is cleaned with isooctane, acetone, and isopropanol under ultrasonic conditions for 10 minutes each; finally, it is blown dry with nitrogen.

[0080] In addition, a layer of PET is attached to the outer surface of the embossing soft mold as a backing support layer, such as Figure 1 As shown in d.

[0081] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a soft mold for conformal imprinting of a non-developable surface, characterized in that: The following steps are involved: Step 1: Substrate Pretreatment Clean and dry the printed substrate to ensure that there are no impurities on the surface of the substrate; Step 2: Print the Master Template According to the characteristic graphic structure required by the imprinting mold, a micro-nano characteristic graphic structure is printed on a non-developable curved surface substrate as a master template; Step 3: Make the intermediate soft mold First, a liquid intermediate material is poured onto a master mold and solidified, and then the solidified flexible intermediate mold is removed from the non-developable curved surface substrate, and then the sacrificial structure of the master mold is removed to obtain an intermediate soft mold; optionally, in order to facilitate the subsequent demolding of the imprinted soft mold, the surface of the intermediate soft mold can be subjected to an anti-adhesion treatment, preferably by spraying or depositing a layer of low surface energy material on its surface; Step 4: Copy the embossing soft mold First, the replication material is poured onto the intermediate soft mold prepared in step 3 and cured, and then the cured flexible imprinting mold is removed from the substrate to obtain an imprinting soft mold with the same structure as the printed master template. Step 5: Mold post-processing The inner and outer surfaces of the embossed soft mold produced in step 4 are turned over, and the surface of the embossed soft mold is treated with anti-adhesion to prevent demolding difficulties during the three-dimensional curved surface conformal embossing process; optionally, a backing support layer is attached to the outer surface of the embossed soft mold.

2. A method for preparing a soft mold for conformal imprinting of a non-developable surface according to claim 1, characterized in that: The printing process in step 2 is five-axis linkage electric field driven melt jet micro-nano 3D printing.

3. The method for preparing a soft mold for conformal imprinting of a non-developable surface according to claim 1, characterized in that: The material for printing the characteristic graphic structure in step 2 includes: one or more of polycaprolactone (PCL), polylactic acid (PLA), polyvinyl alcohol (PVA), and a water-soluble PEG / PEO composite material.

4. The method for preparing a soft mold for conformal imprinting of a non-developable surface according to claim 1, characterized in that: The liquid intermediate material used in step 3 includes one or more of polydimethylsiloxane, fluoropolymer, silicone rubber, UV resin and corresponding materials doped with conductive particles.

5. The method for preparing a soft mold for conformal imprinting of a non-developable surface according to claim 1, characterized in that: The intermediate soft mold curing method in step 3 includes UV curing and / or heating curing.

6. The method for preparing a soft mold for conformal imprinting of a non-developable surface according to claim 1, characterized in that: In the step 3, the method for removing the sacrificial structure of the master mold includes solvent dissolution, heating melting or ultrasonic cleaning.

7. The method for preparing a soft mold for conformal imprinting of a non-developable surface according to claim 1, characterized in that: In step 4, the replication material includes one or more of polydimethylsiloxane (PDMS), fluoropolymer, silicone rubber, UV resin and corresponding materials doped with conductive particles.

8. The method for preparing a soft mold for conformal imprinting of a non-developable surface according to claim 1, characterized in that: In the step 4, the curing method of the imprinted soft mold includes UV curing or heating curing; preferably, the backing support layer in the step 5 can be one or more of polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), and conductive PET.

9. A large-size non-jointed complex curved micro-nano soft mold, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 9.

10. A method for preparing a non-developable surface fine conformal circuit, characterized in that: It is prepared using the large-sized non-spliced ​​complex curved surface micro-nano soft mold described in claim 9.

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