Preparation method of metal mold with multi-layer structure and metal mold with multi-layer structure

Abstract

The invention provides a preparation method of a multi-layer structure metal mold and the multi-layer structure metal mold, the preparation method comprises the steps that at least two single-layer structure metal mold plates are prepared, the heights of micro-channel mold cores in the same single-layer structure metal mold plate are the same, and the heights of the micro-channel mold cores in the same single-layer structure metal mold plate are the same; the heights of the micro-channel mold cores of the different metal templates with the single-layer structures are different, and the demolding angles of the micro-channel mold cores on the metal templates with the single-layer structures are positive demolding angles; hot stamping is carried out on all the prepared single-layer structure metal templates and a polymer plate one by one, so that all the micro-channel mold cores arranged on all the single-layer structure metal templates are hot-stamped on the first side face of the polymer plate, and a multi-layer structure polymer plate is formed; and preparing the multi-layer structure metal mold with a micro-channel mold core with a positive demolding angle by taking the multi-layer structure polymer plate as a substrate. The preparation process disclosed by the invention is relatively simple and easy to implement, and is beneficial to batch production of the multi-layer structure micro-fluidic chip.

Description

Technical Field

[0001] The invention belongs to the technical field of metal mold manufacturing for microfluidic chip manufacturing, and specifically relates to a preparation method of a multi-layer structure metal mold and the multi-layer structure metal mold. Background Art

[0002] A microfluidic chip is a carrier that uses micron-scale channels (also known as microchannels) to process trace amounts of liquid. With the continuous development and maturity of microfluidic technology, market demand is also gradually increasing. It has been widely used in biomedicine, environmental testing, food safety and other fields, and the application scenarios are constantly expanding. The demand for double-layer or multi-layer microfluidic chips is also increasing. The aforementioned multi-layer structure specifically refers to microchannels of different depths in the same microfluidic chip. For example, a step emulsification chip is usually a multi-layer structure, combining microchannels and steps. The discrete phase fluid requires a certain pressure to break through the microchannel and form microdroplets at the steps; a single-cell droplet chip, one layer is a droplet generation channel, and one layer is a droplet paving amplification channel. The droplet paving channel is deeper than the generation channel to prevent the generated droplets from being squeezed in the paving area.

[0003] The way to make polymer microfluidic chips is to inject molten plastic into a metal mold, and then cool and solidify it into a microfluidic chip of a certain shape. For the injection molding of double-layer or multi-layer microfluidic chips with dense and complex structures, it is necessary for the multi-layer or multi-layer metal molds to have positive demolding angles, otherwise the molded chip and the metal mold will be difficult to demold, or cause serious pulling, affecting the flow of liquid or affecting the bonding strength. The traditional methods for making metal molds include MESE process, mechanical processing process, etc., and these processes are difficult to achieve the production of double-layer or multi-layer microchannel metal molds with positive demolding angles.

[0004] Therefore, how to make a metal mold with positive demolding angles for multi-layer microfluidic channels, which is conducive to injection molding and demolding to prepare multi-layer polymer microfluidic chips with complex structures, is a technical problem that needs to be solved urgently in this technology. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to provide a method for preparing a multi-layer structure metal mold and a multi-layer structure metal mold, which can prepare a metal mold with microchannels with positive demolding angles of different depths to meet the preparation requirements of double-layer or multi-layer structure microfluidic chips and realize mass production of double-layer or multi-layer structure microfluidic chips.

[0006] In order to solve the above problems, the present invention provides a method for preparing a multi-layer structure metal mold, comprising the following steps:

[0007] Prepare at least two single-layer structure metal templates, wherein the heights of the microfluidic cores in the same single-layer structure metal template are the same, and the heights of the microfluidic cores in different single-layer structure metal templates are different, and the demolding angles of the microfluidic cores on each single-layer structure metal template are all positive demolding angles;

[0008] Hot-pressing the prepared single-layer structure metal templates with the polymer sheet one by one, so that the microchannel cores respectively provided on the single-layer structure metal templates are hot-pressed on the first side surface of the polymer sheet to form a multi-layer structure polymer sheet;

[0009] The multi-layer structured polymer sheet is used as a substrate to prepare a multi-layer structured metal mold having a micro-flow channel mold core with a positive demoulding angle.

[0010] In some embodiments, the polymer sheet is made of a thermoplastic polymer sheet.

[0011] In some embodiments, the thermoplastic polymer is any one of PMMA, PC, COC, COP, PS, and PP.

[0012] In some embodiments, alignment marks are formed on each of the single-layer structure metal templates and the polymer sheet, and before each of the single-layer structure metal templates is hot-stamped on the polymer sheet, the positions of the two are aligned through the alignment marks.

[0013] In some embodiments, after hot embossing, the polymer sheet is cooled.

[0014] In some embodiments, each single-layer metal template is prepared in the following manner:

[0015] Spin-coat photoresist on a glass substrate, place a mask to expose the photoresist, post-bake, and develop the photoresist to obtain a film structure with a positive release angle;

[0016] Forming a conductive layer on the film structure by magnetron sputtering;

[0017] The adhesive film structure is then electroformed by a pulse electroforming process, and the single-layer structure metal mold is obtained after being peeled off from the glass substrate.

[0018] In some embodiments, the photoresist is an AZ positive photoresist.

[0019] In some embodiments, the method of preparing a multilayer metal mold having a microchannel with a positive demolding angle by using the multilayer polymer sheet as a substrate specifically includes:

[0020] Preparation of the conductive layer: depositing a metal conductive layer on the multilayer polymer sheet by magnetron sputtering;

[0021] Electroforming process: Electroforming is performed on the deposited metal conductive layer through a pulse electroforming process, and the electroformed metal layer is peeled off from the multi-layer structure polymer sheet to obtain the multi-layer structure metal mold with a positive demolding angle micro-channel.

[0022] In some embodiments, the metal conductive layer is one of nickel and chromium.

[0023] The present invention also provides a multi-layer structure metal mold, which is prepared by adopting the preparation method of the multi-layer structure metal mold.

[0024] The present invention provides a method for preparing a multi-layer structure metal mold and a multi-layer structure metal mold. First, according to the number of layers of the multi-layer structure in the multi-layer structure metal mold, a corresponding number of single-layer structure metal molds with microfluidic cores of the same height are prepared, and then each single-layer structure metal mold is hot-embossed on the side of a polymer plate in turn to form a multi-layer structure polymer plate, and then the multi-layer structure polymer plate is used as a substrate to finally prepare a multi-layer structure metal mold with a microfluidic channel with a positive demolding angle. The preparation process is relatively simple and easy, and the prepared multi-layer structure metal mold is easier to demold during injection molding, which is conducive to the mass production of multi-layer structure microfluidic chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 1 is a schematic diagram of the steps of a method for preparing a multi-layer structure metal mold according to an embodiment of the present invention;

[0026] Figure 2 is a process step diagram of a method for preparing a multi-layer structure metal mold according to an embodiment of the present invention in a specific embodiment;

[0027] Figure 3 It is a schematic diagram of the process state of the method for preparing a multi-layer structure metal mold according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] See also Figures 1 to 3 As shown, according to an embodiment of the present invention, a method for preparing a multi-layer structure metal mold is provided, comprising the following steps:

[0029] Step 1: Prepare at least two single-layer structure metal templates, wherein the heights of the microfluidic cores in the same single-layer structure metal template are the same, and the heights of the microfluidic cores in different single-layer structure metal templates are different, and the demolding angles of the microfluidic cores on each single-layer structure metal template are all positive demolding angles. Specifically, each single-layer structure metal template is prepared and formed in the following manner:

[0030] Spin-coat photoresist on a glass substrate, place a mask to expose the photoresist, post-bake, and develop the photoresist to obtain a film structure with a positive release angle;

[0031] Forming a conductive layer on the film structure by magnetron sputtering;

[0032] Then, the film structure is electroformed by a pulse electroforming process, and the single-layer structure metal mold is obtained after being peeled off from the glass substrate;

[0033] Step 2: hot-pressing each of the prepared single-layer structure metal templates with the polymer sheet one by one, so that each microfluidic core respectively provided on each of the single-layer structure metal templates is hot-pressed on the first side of the polymer sheet to form a multi-layer structure polymer sheet. It can be understood that after hot-pressing each of the single-layer structure metal templates with microfluidic cores of different heights on the polymer sheet, a multi-layer structure is formed at the corresponding position on the first side of the polymer sheet. These multi-layer structures can be multi-layer structures arranged side by side in deep and shallow directions on the first side, or multi-layer structures arranged in a deep and shallow manner inside and outside;

[0034] Step 3: Using the multi-layer structure polymer sheet as a substrate, a multi-layer structure metal mold having a micro-channel mold core with a positive demolding angle is prepared.

[0035] It can be understood that the number of the aforementioned single-layer structure metal molds corresponds to the number of layers of the multi-layer structure metal mold. Specifically, when the multi-layer structure metal mold is a double-layer structure metal mold, two single-layer structure metal molds are prepared; when the multi-layer structure metal mold is a three-layer structure metal mold, three single-layer structure metal molds are prepared, and so on.

[0036] In the technical scheme, firstly, a corresponding number of single-layer structure metal molds with microfluidic cores of the same height are prepared according to the number of layers of the multi-layer structure in the multi-layer structure metal mold, and then each single-layer structure metal mold is hot-embossed on the side of a polymer sheet in turn to form a multi-layer structure polymer sheet, and then the multi-layer structure polymer sheet is used as a substrate to finally prepare a multi-layer structure metal mold with a microfluidic channel with a positive demolding angle. The preparation process is relatively simple and easy, and the prepared multi-layer structure metal mold is easier to demold during injection molding, which is conducive to the mass production of multi-layer structure microfluidic chips.

[0037] In some embodiments, the material of the polymer sheet is a thermoplastic polymer sheet. Specifically, the thermoplastic polymer is any one of PMMA (polymethyl methacrylate), PC (polycarbonate), COC and COP (cyclic olefin copolymer), PS (polystyrene), and PP (polypropylene). In this technical solution, the use of thermoplastic polymer sheets can utilize their thermoplastic deformation to achieve the copying of flow channel cores of different heights, which is easy to achieve and has high copying accuracy. It is worth emphasizing that the aforementioned various materials are common thermoplastic polymers with low manufacturing costs. It is understandable that there are no chemical bonds between the molecular chains of thermoplastic polymers, so they can soften and change shape after being heated to a certain temperature, and then harden again by cooling. During the hot stamping process, the microstructure can be replicated and the sheet will not deform.

[0038] In a preferred embodiment, after hot stamping is completed, the polymer sheet is cooled. For example, a water cooling structure is arranged around the polymer sheet to achieve rapid and efficient cooling of the polymer sheet, thereby ensuring that the polymer after hot melting can be quickly cooled and solidified, which can further improve the replication accuracy of the runner core and effectively prevent adverse deformation of the polymer after hot melting.

[0039] In some embodiments, alignment marks are formed on each of the single-layer structure metal templates and the polymer sheet. Before each of the single-layer structure metal templates is hot-embossed on the polymer sheet, the positions of the two are aligned through the alignment marks. The aforementioned alignment marks can be, for example, cross alignment marks formed on the edges of the aforementioned single-layer structure metal template and the polymer sheet. When hot-embossing is performed, the alignment marks on the metal template and the alignment marks on the polymer sheet are aligned to ensure that each layer of the microfluidic structure is in a predetermined position. It can be understood that the specific position of the aforementioned alignment marks should be determined according to the design position of the microfluidic core on the finally prepared multi-layer structure metal template.

[0040] In some embodiments, the photoresist is AZ positive photoresist, and the use of positive photoresist is conducive to the formation of a positive demolding angle of a single-layer microfluidic channel.

[0041] In some embodiments, the method of preparing a multilayer metal mold having a microchannel with a positive demolding angle by using the multilayer polymer sheet as a substrate specifically includes:

[0042] Preparation of the conductive layer: depositing a metal conductive layer on the multilayer polymer sheet by magnetron sputtering;

[0043] Electroforming process: Electroforming is performed on the deposited metal conductive layer through a pulse electroforming process, and the electroformed metal layer is peeled off from the multi-layer structure polymer sheet to obtain the multi-layer structure metal mold with a positive demolding angle micro-channel; the metal conductive layer is one of nickel and chromium, and the thickness of the metal conductive layer is 10nm-1000nm. It should be noted that nickel target and chromium target are commonly used metal target materials for magnetron sputtering, which are low in price, and sputtering 100nm-1000nm can not only make the conductive layer uniform, but also play a conductive role in the subsequent electroforming process. In addition, the subsequent electroforming metal mold is made of nickel, and the conductive layer needs to have a good bonding force with the metal nickel, and nickel and chromium are generally selected. The electroforming nickel mold is because the electroforming nickel process is mature, the mold strength and hardness are high, and the price is low.

[0044] The technical solution of the present invention combines the micro-machining processes of photolithography, hot embossing and electroforming with the injection molding process for the first time. By controlling the exposure energy of the photolithography process, a metal mold with a single-layer flow channel and a positive demolding angle can be prepared; by controlling the temperature, pressure, time and other parameters of hot embossing and the alignment degree of the positioning marks, a metal mold with multi-layer microfluidic channels and a positive demolding angle can be prepared. The metal mold with multi-layer microfluidic channels and a positive demolding angle prepared by the present invention is easier to demold during injection molding, thereby realizing the mass production of multi-layer structure microfluidic chips.

[0045] According to an embodiment of the present invention, a multi-layer structure metal mold is also provided, which is prepared by using the above-mentioned method for preparing the multi-layer structure metal mold.

[0046] The preparation method of the present invention is further described below in conjunction with several specific embodiments:

[0047] Example 1

[0048] A method for preparing a metal mold with double-layer microchannels having positive demoulding angles comprises the following steps:

[0049] (1) Preparation of two single-layer metal molds with positive release angles: Spin-coat AZ positive photoresist (also known as AZ positive photoresist) on a glass substrate, place a mask to expose and develop the photoresist, and obtain the film structures with positive release angles, namely, film structure A and film structure B. For film structure A (for the first single-layer metal mold with positive release angles), the film spreading speed is 2000 rpm, and the exposure dose is 400 mJ / cm 2 , development time is 60s, microchannel depth is 50μm, demolding angle is about 10°; glue structure B (for the second single-layer positive demolding angle metal mold), glue spreading speed is 3000rpm, exposure dose is 200mJ / cm 2 , the development time is 40s, the microchannel depth is 30μm, and the demolding angle is about 10°.

[0050] By magnetron sputtering, a metal conductive layer of nickel is formed on the above film structure with a thickness of 100 nm;

[0051] The film structure is then electroformed using a pulse electroforming process with a current of 5A, a frequency of 1500Hz, a positive / negative duty cycle of 5%, and an electroforming time of 10h. The electroformed metal mold is peeled off from the glass substrate to obtain two single-layer metal molds with positive demolding angles, namely, metal mold A (also known as the first single-layer metal mold with a positive demolding angle) and metal mold B (also known as the second single-layer metal mold with a positive demolding angle), with a demolding angle of about 10°.

[0052] (2) Hot stamping process: The metal mold A structure is first replicated on the PC sheet by hot stamping. The hot stamping parameters are upper and lower hot stamping temperature of 150°C, pressure of 10000N, and time of 10 min. After the above hot stamping parameters are executed, the water cooling equipment is turned on, and the upper and lower hot stage temperatures are reduced to 80°C, while the pressure and temperature remain unchanged.

[0053] Then, the second metal mold structure (i.e., metal mold B) is also copied on the PC sheet through the cross alignment marks on the PC sheet and the single-layer microstructure metal mold B, with the same parameters as above;

[0054] (3) Preparation of conductive layer: A metal conductive layer of nickel is formed on the polymer sheet with the replicated double-layer microstructure by magnetron sputtering, and the thickness of the conductive layer is 100 nm;

[0055] (4) Electroforming process: Electroforming is performed on the polymer microstructure with a deposited metal conductive layer through a pulse electroforming process, with a current of 5A, a frequency of 1500Hz, a positive / negative duty cycle of 5%, and an electroforming time of 10h; the electroformed metal mold and the polymer sheet are peeled off to obtain a metal mold with a positive demolding angle for both double-layer microfluidics, and the demolding angle is about 10°.

[0056] Example 2

[0057] A method for preparing a metal mold with multi-layer micro-channels having positive demoulding angles comprises the following steps:

[0058] (1) Fabrication of a single-layer metal mold with a positive release angle: Spin-coat an AZ photoresist on a glass substrate, place a mask to expose and develop the photoresist, and obtain film structures with a positive release angle, namely, film structure C, film structure D, and film structure E. For film structure C, the film spreading speed is 1000 rpm and the exposure dose is 1000 mJ / cm 2 , development time is 150s, microchannel depth is 100μm, demoulding angle is about 20°; glue structure D, glue spreading speed is 2000rpm, exposure dose is 450mJ / cm 2, developing time is 60s, microchannel depth is 50μm, and demolding angle is about 20°; glue structure E, glue spreading speed is 3000rpm, exposure dose is 230mJ / cm2, developing time is 45s, microchannel depth is 30μm, and demolding angle is about 20°.

[0059] By magnetron sputtering, a metal conductive layer of nickel is formed on the above film structure with a thickness of 100 nm;

[0060] The film structure is then electroformed using a pulse electroforming process with a current of 5A, a frequency of 1500Hz, a positive / negative duty cycle of 5%, and an electroforming time of 10h. The electroformed metal mold is peeled off from the glass substrate to obtain a single-layer metal mold C, a single-layer metal mold D, and a single-layer metal mold E with a positive demolding angle, and a demolding angle of about 20°.

[0061] (2) Hot embossing process: First, one of the metal mold C structures is replicated on the PMMA sheet by hot embossing. The hot embossing parameters are upper and lower hot pressing temperature of 110°C, pressure of 5000N, and time of 10 min. After the above hot pressing parameters are executed, the water cooling equipment is turned on, and the upper and lower hot stage temperatures are reduced to 80°C, while the pressure and temperature remain unchanged.

[0062] Then, the second metal mold structure is also copied on the PMMA sheet through the cross alignment marks on the PMMA sheet and the single-layer microstructure metal mold D, with the same parameters as above;

[0063] Then, the second metal mold structure is also copied on the PMMA sheet through the cross alignment marks on the PMMA sheet and the single-layer microstructure metal mold E, with the same parameters as above;

[0064] (3) Preparation of conductive layer: A metal conductive layer of nickel is formed on the polymer sheet with the replicated multi-layer microstructure by magnetron sputtering, and the thickness of the conductive layer is 100 nm;

[0065] (4) Electroforming process: Electroforming is performed on the polymer microstructure with a deposited metal conductive layer by pulse electroforming process, with a current of 5A, a frequency of 1500Hz, a positive / negative duty cycle of 5%, and an electroforming time of 10h; the electroformed metal mold is peeled off from the polymer sheet to obtain a metal mold with a positive demolding angle of about 20° for the multi-layer microfluidic channels.

[0066] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0067] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention. The above are only preferred embodiments of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present invention, and these improvements and variations should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a multi-layer metal mold, characterized in that: The steps include: Prepare at least two single-layer structure metal templates, wherein the heights of the microfluidic cores in the same single-layer structure metal template are the same, and the heights of the microfluidic cores in different single-layer structure metal templates are different, and the demolding angles of the microfluidic cores on each single-layer structure metal template are all positive demolding angles; Hot-pressing the prepared single-layer structure metal templates with the polymer sheet one by one, so that the microchannel cores respectively provided on the single-layer structure metal templates are hot-pressed on the first side surface of the polymer sheet to form a multi-layer structure polymer sheet; The multi-layer structured polymer sheet is used as a substrate to prepare a multi-layer structured metal mold having a micro-flow channel mold core with a positive demoulding angle.

2. The method for preparing a multi-layered metal mold according to claim 1, characterized in that: The polymer sheet is made of thermoplastic polymer sheet.

3. The method for preparing a multi-layered metal mold according to claim 2, characterized in that: The thermoplastic polymer is any one of PMMA, PC, COC, COP, PS and PP.

4. The method for preparing a multi-layered metal mold according to claim 1, characterized in that: Alignment marks are formed on each of the single-layer structure metal templates and the polymer sheet. Before each of the single-layer structure metal templates is hot-stamped on the polymer sheet, the alignment marks are used to achieve position alignment between the two.

5. The method for preparing a multi-layered metal mold according to claim 1, characterized in that: After hot embossing, the polymer sheet is cooled.

6. The method for preparing a multi-layered metal mold according to claim 1, characterized in that: Each single-layer metal template is prepared in the following manner: Spin-coat photoresist on a glass substrate, place a mask to expose the photoresist, post-bake, and develop the photoresist to obtain a film structure with a positive release angle; Forming a conductive layer on the film structure by magnetron sputtering; The adhesive film structure is then electroformed by a pulse electroforming process, and the single-layer structure metal mold is obtained after being peeled off from the glass substrate.

7. The method for preparing a multi-layered metal mold according to claim 6, characterized in that: The photoresist is AZ positive photoresist.

8. The method for preparing a multi-layered metal mold according to claim 1, characterized in that: The method of preparing a multi-layer structure metal mold with a micro-channel with a positive demolding angle by using the multi-layer structure polymer sheet as a substrate specifically includes: Preparation of the conductive layer: depositing a metal conductive layer on the multilayer polymer sheet by magnetron sputtering; Electroforming process: Electroforming is performed on the deposited metal conductive layer through a pulse electroforming process, and the electroformed metal layer is peeled off from the multi-layer structure polymer sheet to obtain the multi-layer structure metal mold with a positive demolding angle micro-channel.

9. The method for preparing a multi-layered metal mold according to claim 8, characterized in that: The metal conductive layer is one of nickel and chromium.

10. A multi-layer metal mold, characterized in that: The multi-layer structure metal mold is prepared by the preparation method of any one of claims 1 to 9.

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