Method for manufacturing a multi-layered metal mold and multi-layered metal mold

Abstract

The application provides a preparation method of a multilayer structure metal mold and the multilayer structure metal mold. The preparation method comprises the following steps: preparing at least two single-layer structure metal molds; the heights of the micro-channel mold cores in the same single-layer structure metal mold are the same; the heights of the micro-channel mold cores in different single-layer structure metal molds are different; and the demolding angles of the micro-channel mold cores on each single-layer structure metal mold are all positive demolding angles; each prepared single-layer structure metal mold is sequentially hot-pressed with a polymer plate to make the micro-channel mold cores on each single-layer structure metal mold be hot-pressed on the first side of the polymer plate, so that a multilayer structure polymer plate is formed; and the multilayer structure polymer plate is used as a substrate to prepare a multilayer structure metal mold with positive demolding angle micro-channel mold cores. The preparation process is simple and easy to implement, and is beneficial to the batch production of multilayer structure micro-fluidic chips.

Description

Technical Field

[0001] This invention belongs to the field of metal mold manufacturing technology for microfluidic chip manufacturing, specifically relating to a method for preparing a multi-layer metal mold and the multi-layer metal mold itself. Background Technology

[0002] Microfluidic chips are carriers that utilize micron-level channels (i.e., microchannels) to process trace amounts of liquid. With the continuous development and maturation of microfluidic technology, market demand is gradually increasing, and they have been widely applied in fields such as biomedicine, environmental monitoring, and food safety. The application scenarios are also constantly expanding, leading to a growing demand for microfluidic chips with dual-layer or multi-layer structures. Specifically, the aforementioned multi-layer structure refers to the presence of microchannels of varying depths within the same microfluidic chip. For example, stepped emulsification chips typically have a multi-layer structure, combining microchannels and steps. The discrete phase fluid requires a certain pressure to break through the microchannels, forming microdroplets at the steps. In single-cell droplet chips, one layer is a droplet generation channel, and the other is a droplet spreading and amplification channel. The droplet spreading channel is deeper than the generation channel to prevent the generated droplets from being squeezed in the spreading area.

[0003] The fabrication of polymer microfluidic chips involves injecting molten plastic into a metal mold, followed by cooling and solidification into a microfluidic chip of a specific shape. For injection molding of densely packed, complex microfluidic chips with dual or multi-layer structures, all layers of the metal mold must have positive draft angles. Otherwise, the molded chip and the metal mold will be difficult to demold, or severe pull-out may occur, affecting liquid flow or bonding strength. Traditional methods for fabricating metal molds, such as MESE (Mechanical, Electro-Enhanced Separation) processes and machining, are difficult to implement to ensure that all dual or multi-layer microchannels have positive draft angles.

[0004] Therefore, how to manufacture a metal mold with positive demolding angles for all multi-layered microchannels, which is beneficial for injection molding and demolding to prepare complex multi-layered polymer microfluidic chips, is a technical problem that urgently needs to be solved 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 metal mold and a multi-layer metal mold, which can prepare a metal mold with microchannels of different depths and positive demolding angles to meet the preparation requirements of dual-layer or multi-layer microfluidic chips and realize the mass production of dual-layer or multi-layer microfluidic chips.

[0006] To address the above problems, this invention provides a method for preparing a multi-layered metal mold, comprising the following steps:

[0007] Prepare at least two single-layer structure metal templates, wherein the height of each microchannel mold core in the same single-layer structure metal template is the same, and the height of the microchannel mold core in different single-layer structure metal templates is different, and the demolding angle of the microchannel mold core on each single-layer structure metal template is a positive demolding angle.

[0008] Each of the prepared single-layer structure metal templates is hot-pressed onto the polymer sheet, so that each microchannel core on each of the single-layer structure metal templates is hot-pressed onto the first side of the polymer sheet, forming a multi-layer structure polymer sheet.

[0009] A multi-layered metal mold with a microchannel core having a positive demolding angle was prepared using the multi-layered polymer sheet as a substrate.

[0010] In some embodiments, the polymer sheet is made of 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 the alignment marks are used to align the two before each of the single-layer structure metal templates is heat-pressed onto the polymer sheet.

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

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

[0015] Photoresist is spin-coated onto a glass substrate, and a mask is placed to expose, bake, and develop the photoresist to obtain a film structure with a positive release angle.

[0016] A conductive layer is formed on the adhesive film structure by magnetron sputtering;

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

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

[0019] In some embodiments, the preparation of a multilayer metal mold with microchannels having a positive release angle using the multilayer polymer sheet as a substrate specifically includes:

[0020] Preparation of conductive layer: A metallic conductive layer is deposited on the multilayer polymer substrate by magnetron sputtering;

[0021] Electroforming process: Electroforming is performed on the deposited conductive metal layer using a pulse electroforming process. The electroformed metal layer is then peeled off from the multilayer polymer sheet to obtain the multilayer metal mold with a positive demolding angle microchannel.

[0022] In some embodiments, the conductive metal layer is either nickel or chromium.

[0023] The present invention also provides a multi-layer metal mold, which is prepared by the above-described method for preparing a multi-layer metal mold.

[0024] This invention provides a method for preparing a multi-layered metal mold and the multi-layered metal mold itself. First, based on the number of layers in the multi-layered metal mold, a number of single-layered metal molds with microfluidic cores of the same height are prepared. Then, each single-layered metal mold is sequentially hot-pressed onto the side of a polymer sheet to form a multi-layered polymer sheet. Finally, using this multi-layered polymer sheet as a substrate, a multi-layered metal mold with microfluidic channels having a positive demolding angle is obtained. The preparation process is relatively simple and easy to implement, and the prepared multi-layered metal mold is easy to demold during injection molding, which is beneficial for the mass production of multi-layered microfluidic chips. Attached Figure Description

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

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

[0027] Figure 3 This is a schematic diagram of the process state of the preparation method of the multi-layer structure metal mold according to an embodiment of the present invention. Detailed Implementation

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

[0029] Step 1: Prepare at least two single-layer metal templates. The height of each microchannel core within the same single-layer metal template is the same. The height of the microchannel cores in different single-layer metal templates is different, and the demolding angle of the microchannel cores on each single-layer metal template is a positive demolding angle. Specifically, each single-layer metal template is prepared using the following method:

[0030] Photoresist is spin-coated onto a glass substrate, and a mask is placed to expose, bake, and develop the photoresist to obtain a film structure with a positive release angle.

[0031] A conductive layer is formed on the adhesive film structure by magnetron sputtering;

[0032] The film structure is then electroformed using a pulse electroforming process, and after being peeled off from the glass substrate, the single-layer metal mold is obtained.

[0033] Step 2: The prepared single-layer structure metal templates are hot-pressed onto the polymer sheet one by one, so that the microchannel cores on each single-layer structure metal template are hot-pressed onto the first side of the polymer sheet, forming a multi-layer structure polymer sheet. It can be understood that after hot-pressing the single-layer structure metal templates with microchannel cores of different heights onto 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 with shallow and deep sides arranged side by side on the first side, or multi-layer structures with shallow and deep sides nested inside and outside.

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

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

[0036] In this technical solution, firstly, a number of single-layer metal molds with microchannel cores of the same height are prepared according to the number of layers in the multi-layer metal mold. Then, each single-layer metal mold is sequentially hot-pressed onto the side of a polymer sheet to form a multi-layer polymer sheet. Finally, using the multi-layer polymer sheet as a substrate, a multi-layer metal mold with microchannels having a positive demolding angle is obtained. The preparation process is relatively simple and easy to implement. The prepared multi-layer metal mold is easy to demold during injection molding, which is beneficial for the mass production of multi-layer microfluidic chips.

[0037] In some embodiments, the polymer sheet is made of a thermoplastic polymer sheet. Specifically, the thermoplastic polymer is any one of PMMA (polymethyl methacrylate), PC (polycarbonate), COC and COP (cyclic olefin copolymers), PS (polystyrene), and PP (polypropylene). In this technical solution, using a thermoplastic polymer sheet allows for the replication of flow channel cores of varying heights through thermoplastic deformation, which is easy to implement and offers high replication accuracy. It is worth emphasizing that the aforementioned materials are common thermoplastic polymers with low manufacturing costs. It is understood that thermoplastic polymer molecular chains are not chemically bonded, therefore, they can soften and change shape after heating to a certain temperature, and then harden again upon cooling. During the hot-pressing process, microstructures can be replicated without deformation of the sheet.

[0038] In a preferred embodiment, after hot stamping is completed, the polymer sheet is cooled. Specifically, for example, a water cooling structure is provided around the polymer sheet to achieve rapid and efficient cooling of the polymer sheet, thereby ensuring that the polymer after hot melting can be cooled and solidified quickly. This can further improve the replication accuracy of the flow channel mold 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 polymer plates. Before each of the single-layer structure metal templates is hot-pressed onto the polymer plate, the alignment marks are used to align their positions. For example, the alignment marks can be cross-shaped alignment marks formed on the edges of the single-layer structure metal templates and polymer plates. During hot pressing, the alignment marks on the metal templates and the alignment marks on the polymer plates are aligned to ensure that each layer of microchannel structure is in a predetermined position. It is understood that the specific position of the alignment marks should be determined according to the design position of the microchannel core on the finally prepared multi-layer structure metal template.

[0040] In some embodiments, the photoresist is an AZ positive photoresist, and using a positive photoresist is beneficial for forming a positive release angle in a single-layer microchannel.

[0041] In some embodiments, the preparation of a multilayer metal mold with microchannels having a positive release angle using the multilayer polymer sheet as a substrate specifically includes:

[0042] Preparation of conductive layer: A metallic conductive layer is deposited on the multilayer polymer substrate by magnetron sputtering;

[0043] Electroforming process: Electroforming is performed on the deposited conductive metal layer using a pulse electroforming process. The electroformed metal layer is then peeled off from the multilayer polymer sheet to obtain the multilayer metal mold with microchannels having a positive release angle. The conductive metal layer is either nickel or chromium, and its thickness is 10nm-1000nm. It should be noted that nickel and chromium targets are commonly used metal targets in magnetron sputtering, are inexpensive, and sputtering to a thickness of 100nm-1000nm ensures a uniform conductive layer while also providing conductivity during subsequent electroforming. Furthermore, the metal mold used for subsequent electroforming is made of nickel, and the conductive layer needs to have good adhesion to the nickel metal; nickel and chromium are generally chosen. Nickel molds are used because the electroforming process for nickel is mature, the mold has high strength and hardness, and is inexpensive.

[0044] The technical solution of this invention combines micromachining processes such as photolithography, hot stamping, and electroforming with injection molding for the first time. By controlling the exposure energy during the photolithography process, a metal mold with a single-layer flow channel having a positive release angle can be fabricated. By controlling the temperature, pressure, time, and other parameters of hot stamping, as well as controlling the alignment of the positioning marks, a metal mold with multiple microchannels having a positive release angle can be fabricated. The metal mold with multiple microchannels having a positive release angle prepared by this invention is easier to demold during injection molding, realizing the mass production of multi-layer microfluidic chips.

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

[0046] The preparation method of the present invention is further illustrated below with reference to several specific embodiments:

[0047] Example 1

[0048] A method for preparing a metal mold with both microchannels having positive demolding angles includes the following steps:

[0049] (1) Fabrication of two single-layer positive release angle metal molds: AZ positive photoresist (i.e., AZ photoresist) is spin-coated onto a glass substrate. After exposure and development of the photoresist using a mask, the film structures with positive release angles are obtained, namely, structure A and structure B. Structure A (for the first single-layer positive release angle metal mold) has a spin coating speed of 2000 rpm and an exposure dose of 400 mJ / cm. 2 The development time was 60 seconds, the microchannel depth was 50 μm, and the demolding angle was approximately 10°; for adhesive structure B (for the second single-layer positive demolding angle metal mold), the coating speed was 3000 rpm, and the exposure dose was 200 mJ / cm². 2 The development time is 40 seconds, the microchannel depth is 30 μm, and the demolding angle is approximately 10°.

[0050] A nickel conductive metal layer with a thickness of 100 nm was formed on the above-mentioned adhesive film structure by magnetron sputtering.

[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. After the electroformed metal mold is peeled off from the glass substrate, two single-layer metal molds with positive demolding angles are obtained: metal mold A (the first single-layer metal mold with a positive demolding angle) and metal mold B (the second single-layer metal mold with a positive demolding angle), with a demolding angle of about 10°.

[0052] (2) Hot pressing process: The metal mold A structure is copied onto the PC board by hot pressing. The hot pressing parameters are: upper and lower hot pressing temperature 150℃, pressure 10000N, time 10min. After the above hot pressing parameters are executed, the water cooling equipment is turned on, and the temperature of the upper and lower hot plates is reduced to 80℃, while the pressure and temperature remain unchanged.

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

[0054] (3) Preparation of conductive layer: A nickel conductive layer with a thickness of 100 nm was formed on the polymer substrate with replicated double microstructure by magnetron sputtering.

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

[0056] Example 2

[0057] A method for preparing a metal mold with multiple microchannels all having positive demolding angles includes the following steps:

[0058] (1) Fabrication of a single-layer positive release angle metal mold: AZ photoresist is spin-coated onto a glass substrate. After exposure and development of the photoresist using a mask, the film structures with positive release angles are obtained, namely resist structure C, resist structure D, and resist structure E. For resist structure C, the spin coating speed is 1000 rpm, and the exposure dose is 1000 mJ / cm. 2 The development time was 150s, the microchannel depth was 100μm, and the demolding angle was approximately 20°; the adhesive structure was D, the spin coating speed was 2000rpm, and the exposure dose was 450mJ / cm. 2The development time was 60s, the microchannel depth was 50μm, and the demolding angle was about 20°; the adhesive structure was E, the uniform coating speed was 3000rpm, the exposure dose was 230mJ / cm2, the development time was 45s, the microchannel depth was 30μm, and the demolding angle was about 20°.

[0059] A nickel conductive metal layer with a thickness of 100 nm was formed on the above-mentioned adhesive film structure by magnetron sputtering.

[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. After the electroformed metal mold is peeled off from the glass substrate, single-layer metal molds C, D, and E with a positive demolding angle of approximately 20° are obtained.

[0061] (2) Hot pressing process: The metal mold C structure is copied onto the PMMA sheet by hot pressing. The hot pressing parameters are: upper and lower hot pressing temperature 110℃, pressure 5000N, time 10min. After the above hot pressing parameters are executed, the water cooling equipment is turned on and the temperature of the upper and lower hot plates is reduced to 80℃, while the pressure and temperature remain unchanged.

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

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

[0064] (3) Preparation of conductive layer: A nickel conductive layer with a thickness of 100 nm was formed on the polymer substrate with replicated multilayer microstructure by magnetron sputtering.

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

[0066] It will be readily understood by those skilled in the art that the aforementioned advantageous methods can be freely combined and superimposed without conflict.

[0067] The above are merely 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 should be included within the protection scope of the present invention. The above are merely preferred embodiments of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A method for preparing a multi-layered metal mold, characterized in that, Includes the following steps: Prepare at least two single-layer structure metal templates, wherein the height of each microchannel mold core in the same single-layer structure metal template is the same, and the height of the microchannel mold core in different single-layer structure metal templates is different, and the demolding angle of the microchannel mold core on each single-layer structure metal template is a positive demolding angle. Each of the prepared single-layer structure metal templates is hot-pressed onto the polymer sheet, so that each microchannel core on each of the single-layer structure metal templates is hot-pressed onto the first side of the polymer sheet, forming a multi-layer structure polymer sheet. A multi-layered metal mold with a microchannel core having a positive demolding angle was prepared using the multi-layered polymer sheet as a substrate.

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 polymer sheets. Before each of the single-layer structure metal templates is heat-pressed onto the polymer sheet, the alignment marks are used to align the two.

5. The method for preparing a multi-layered metal mold according to claim 1, characterized in that, After the hot stamping is completed, 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 using the following method: Photoresist is spin-coated onto a glass substrate, and a mask is placed to expose, bake, and develop the photoresist to obtain a film structure with a positive release angle. A conductive layer is formed on the adhesive film structure by magnetron sputtering; The film structure is then electroformed using a pulse electroforming process, and after being peeled off from the glass substrate, the single-layer metal mold is obtained.

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

8. The method for preparing a multi-layered metal mold according to claim 1, characterized in that, The preparation of a multi-layered metal mold with microchannels having a positive release angle using the aforementioned multi-layered polymer sheet as a substrate specifically includes: Preparation of conductive layer: A metallic conductive layer is deposited on the multilayer polymer substrate by magnetron sputtering; Electroforming process: Electroforming is performed on the deposited conductive metal layer using a pulse electroforming process. The electroformed metal layer is then peeled off from the multilayer polymer sheet to obtain the multilayer metal mold with a positive demolding angle microchannel.

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

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

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