CN108452855B - Method for processing micro-fluidic chip - Google Patents
Method for processing micro-fluidic chip Download PDFInfo
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- CN108452855B CN108452855B CN201810335107.XA CN201810335107A CN108452855B CN 108452855 B CN108452855 B CN 108452855B CN 201810335107 A CN201810335107 A CN 201810335107A CN 108452855 B CN108452855 B CN 108452855B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
- B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
- B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
- B01L3/502—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures
- B01L3/5027—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip
- B01L3/502707—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip characterised by the manufacture of the container or its components
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Abstract
The invention provides a method for processing a microfluidic chip, which comprises the steps of preparing a high-precision substrate die by using a precision photoetching process, and forming the substrate die by using a deep etching process. And covering the metal layer on the substrate mould, and processing the high-precision metal mould by using a precision electroforming process. And then, obtaining the micro-channel chip with the same concave-convex property as the photoresist mould by using an integrated precise injection molding technology. The method combines the micro-processing technology based on photoetching, etching and electroforming with the injection molding technology used in industry for the first time, and uses the precise mold to process the micro-fluidic chips of the thermoplastic materials with different flow channel heights, thereby realizing the batch processing of the micro-fluidic chips with high yield and low cost.
Description
Technical Field
The invention relates to the field of microfluidic chips, in particular to a method for processing a microfluidic chip.
Background
The micro-fluidic chip becomes an important direction and front edge of the development of the current analytical instrument, and the development of the micro-fluidic chip technology needs advanced micro-manufacturing technology as a rear shield. The microfluidic chip based on silicon and glass has high material cost and complex high-precision processing technology, and is difficult to realize the requirement of batch production. The material cost of the microfluidic chip based on the polymer material is low, and the material is widely used in chip processing in the field of the current microfluidic technology.
Currently, Polydimethylsiloxane (PDMS) based microfluidic chips have been extensively studied. Researchers utilize a soft lithography process to process a PDMS microfluidic chip with a micron order. First, researchers have used thick photoresists (e.g., SU-8 thick resist) and conventional photolithography techniques to fabricate high aspect ratio molds with micron precision on the surface of silicon-based substrates. Then, a mixed solution of PDMS precursor and its crosslinking agent is poured on the surface of the mold. And heating, curing and separating the die to prepare the elastic PDMS microfluidic structure chip with a complementary structure. The PDMS microfluidic structure chip and the glass substrate are subjected to a reversible bonding step to finally form a packaged microfluidic chip.
Although the PDMS microfluidic chip material has low development cost and simple laboratory processing technology, the disadvantages include:
(1) PDMS is a thermoelastic polymer material, and the material is not suitable for industrial injection molding and packaging processes. The manually processed PDMS microfluidic chip has poor reliability;
(2) the batch processing cost of the PDMS microfluidic chip is high.
The characteristic size of the microfluidic chip is between dozens of micrometers and hundreds of micrometers, and the surface roughness is in the nanometer level. In the conventional hot die pressing and injection molding process, a metal mold is firstly prepared, and then the microfluidic chips based on the thermoplastic material are processed in batches. The size precision of the metal mold processed by the common mechanical processing and electric spark process is in the order of hundreds of microns, the surface roughness is in the order of submicron, and the strict requirements of the microfluidic application on the uniformity and the precision cannot be met. The conventional optical disk manufacturing technology comprises a precision mold manufacturing process and a precision injection molding process, and the size precision and the surface roughness of the mold are both in the nanometer level. But the size of the precision mould manufacturing process of the optical disc mould is in the order of hundreds of nanometers and is far smaller than the size requirement of the microfluidic chip. The existing chip preparation process has a distance from batch generation, and the wide application of the microfluidic chip in the field of clinical examination is limited.
Disclosure of Invention
In order to solve the above problems, the present invention provides a method for processing a microfluidic chip having a height dimension of 2 to 200 μm, the method comprising the steps of: step 1: transferring the design pattern of the microfluidic chip drawn on the mask to a mold substrate in a graphical mode by utilizing a photoetching process; step 2: etching the part of the substrate which is not protected by the photoresist by using a deep etching process to form a substrate mold; and step 3: covering a metal layer on the substrate mould, and processing a metal mould by using a precision electroforming process; and step 4: and performing injection molding on the metal mold by using an integrated injection molding technology to obtain the microfluidic chip.
In one embodiment, a substrate of silicon, quartz or glass is used as the mold base when the microfluidic chip has a height dimension of between 2 and 50 microns.
In one embodiment, when the height dimension of the microfluidic chip is greater than 50 micrometers, a substrate made of silicon, quartz or glass with a metal thin film deposited on the surface is used as the mold base.
In one embodiment, the metal thin film has a thickness of 2 to 10 micrometers.
In one embodiment, the metal thin film material is aluminum.
In one embodiment, the metal layer on the base mold is a metallic chromium layer or a nickel layer.
In one embodiment, the metal mold material is nickel.
In one embodiment, the covering of the metal layer on the base mold is achieved by evaporation or sputtering.
In the invention, firstly, a high-precision metal mold is prepared by utilizing a deep etching process, and then the micro-channel substrate is processed by utilizing an injection molding process. The basic principle is as follows: firstly, a micro-fluidic chip design pattern drawn on a mask is transferred to a mold substrate (material: silicon, quartz or glass) in a graphical mode by utilizing a precise photoetching process, so that a high-precision substrate mold is prepared. And etching the part of the substrate which is not protected by the photoresist by using a deep etching process to form a substrate mold. A metal layer (material: chromium or nickel) is coated on the die by means of vapor deposition or sputtering, and a high-precision metal die is formed by a precision electroforming process (material: nickel). The metal mold structure is complementary to the photoresist mold structure in terms of concavity and convexity. And then, obtaining the micro-channel substrate with the same concave-convex property as the photoresist mould by using an integrated precise injection molding technology. The method combines the precision of the micro-processing technology and the batch of the injection molding technology: the metal mold prepared by the micromachining process has the advantages that the angle of the inclination angle of the side wall of the microstructure is controllable, and the angle of the inclination angle of the side wall of the microstructure is usually controlled to be smaller than 90 degrees, so that the metal mold is convenient to demold; the surface flatness is in nanometer level, the light transmission can be ensured to the maximum extent, non-specific adsorption is avoided, and the height size of the microstructure is adjustable between 2 and 200 micrometers; meanwhile, the specification and the size of the high-precision metal nickel mold meet the requirements of the optical disk injection molding machine, so that the polymer micro-fluidic chip can be processed on the traditional optical disk injection molding machine in batch.
In summary, the invention discloses a method for processing microfluidic chips, which combines a micro-processing technology based on photoetching, etching and electroforming with an injection molding technology used in industry for the first time, and uses a precision mold to process the microfluidic chips of thermoplastic materials with different flow channel heights, thereby realizing the batch processing of the microfluidic chips with high yield and low cost.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a process flow diagram of a microstructure of the present invention having a height dimension of between 2 and 50 microns;
FIG. 2 is a process flow diagram of a microstructure of the present invention having a height dimension between greater than 50 and less than 200 microns;
FIG. 3 is a cross-sectional view of a glass mold microstructure machined according to the method of the present invention;
FIG. 4 is a schematic view of a microfluidic chip metal mold processed according to the method of the present invention; and
fig. 5 is a schematic view of a microfluidic chip processed according to the method of the present invention.
Detailed Description
In order to make those skilled in the art better understand the technical solutions in the present application, the present invention will be further described below with reference to the following embodiments, and it is obvious that the described embodiments are only a part of the embodiments of the present application, 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 application. The invention is further described with reference to the following figures and examples.
The first embodiment is as follows: processing flow of microstructure with small thickness
If the microstructure thickness is small, for example 2-49 microns, as shown in figure 1, photoresist can be used as a mask for the etch-back process. In a first step, a photoresist, either positive or negative, is uniformly spin coated on the front side of a substrate such as silicon, quartz and glass. And step two, after photoetching and developing processes, exposing by using a mask plate with a target pattern, and after developing, ensuring that no photoresist exists on the area to be etched. And thirdly, putting the substrate with the photoresist pattern on the surface into a deep etching cavity for deep etching (the gas atmosphere is argon and C4F8, the time is 3900 second, the gas pressure is 0.1 Pa, and the power is 20 watts). And after the deep etching is finished, putting the substrate into the degumming solution to remove the residual photoresist on the surface. And fourthly, sequentially placing the substrate into acetone, alcohol and deionized water for ultrasonic cleaning, evaporating or sputtering a layer of chromium or nickel on the surface of the mold to be used as a seed layer, and obtaining the high-precision metal mold after precision electroforming. And a fifth part, wherein the metal mold is used for batch injection molding processing of the microfluidic chip after precision electroforming, and for example, the working parameters are as follows: the drying temperature is 80 ℃, the drying time is about 3 hours, the mold temperature is 70 ℃, the residual material amount is 4 mm, the melt adhesive temperature is 260 ℃, the back pressure is 10MPa, the injection pressure is 100MPa, the mold locking force is about 3-4 tons/square inch, the injection molding speed is medium, the material returning rotating speed is 60 revolutions per minute, and the screw type standard screw diameter is 50 mm.
In this process, two key process parameters can be controlled by controlling the radio frequency power, the gas pressure and the gas flow: etch rate and sidewall slope angle. The etch rate determines the roughness of the etched surface: the larger the etching rate is, the more nonuniform the structure is, the rougher the surface is, but the etching speed is high; conversely, the smaller the etching rate, the more uniform the structure and the smoother the surface, but the slower the etching rate. Therefore, it is necessary to control rf power, gas pressure, and gas flow rate to simultaneously meet surface performance requirements and processing speed. The inclination angle of the side wall is the included angle between the plane direction of the substrate and the side wall, and the inclination angle of the side wall determines the difficulty of demoulding, generally, the smaller the inclination angle of the side wall is, the easier demoulding is, but the smaller the inclination angle of the side wall is, the uniformity of the micro-channel along the depth direction can be obviously reduced, and therefore, the radio frequency power, the air pressure and the air flow rate need to be controlled to simultaneously meet the demoulding performance and the size precision.
In the process flow, in order to control the temperature of the substrate not to be too high, the whole etching process can be divided into dozens of cycles, and each cycle comprises three processes of etching, passivating and cooling.
Example two: processing flow of microstructure with larger thickness
As shown in fig. 2, if the thickness of the microstructure is large, for example 50-200 μm, the resist protection layer is not enough to resist the destructive effect of the deep etching, and then a metal material such as aluminum can be used as a mask for the deep etching process. In a first step, a photoresist, either positive or negative, is uniformly spun onto the front side of a substrate, such as silicon, quartz or glass. The thickness of the surface deposited metal film, such as aluminum, ranges from 2 microns to 10 microns. And step two, after photoetching and developing processes, patterning the photoresist layer by using a mask with a designed pattern, and ensuring that the metal surface of the area to be etched does not have photoresist after developing. And thirdly, removing the film metal which is not protected by the photoresist through wet etching, and reserving the film metal protected by the photoresist, thereby transferring the pattern on the photoresist to the surface of the metal film. And fourthly, putting the substrate with the metal pattern on the surface into a deep etching cavity for deep etching (the gas atmosphere is argon and C4F8, the time is 9700 seconds, the gas pressure is 0.1 Pa, and the power is 20 watts). And after the deep etching is finished, putting the substrate into the degumming solution to remove the residual photoresist on the surface. And fifthly, putting the substrate into acetone, alcohol and deionized water in sequence for ultrasonic cleaning, and evaporating or sputtering a layer of chromium or nickel on the surface of the mold to be used as a seed layer. And sixthly, the metal mold is used for batch injection molding processing of the microfluidic chip after precision electroforming, for example, the working parameters are as follows: the drying temperature is 80 ℃, the drying time is about 3 hours, the mold temperature is 70 ℃, the residual material amount is 4 mm, the melt adhesive temperature is 260 ℃, the back pressure is 10MPa, the injection pressure is 100MPa, the mold locking force is about 3-4 tons/square inch, the injection molding speed is medium, the material returning rotating speed is 60 revolutions per minute, and the screw type standard screw diameter is 50 mm.
In this process, two key process parameters can be controlled by controlling the radio frequency power, the gas pressure and the gas flow: etch rate and sidewall slope angle. The etch rate determines the roughness of the etched surface: the larger the etching rate is, the more nonuniform the structure is, the rougher the surface is, but the etching speed is high; conversely, the smaller the etching rate, the more uniform the structure and the smoother the surface, but the slower the etching rate. Therefore, it is necessary to control rf power, gas pressure, and gas flow rate to simultaneously meet surface performance requirements and processing speed. The inclination angle of the side wall determines the degree of difficulty of demolding, generally, the smaller the inclination angle of the side wall is, the easier demolding is, but the smaller the inclination angle of the side wall is, the more the uniformity of the micro flow channel in the depth direction is significantly reduced, so that the radio frequency power, the air pressure and the air flow rate need to be controlled to simultaneously satisfy the demolding performance and the dimensional accuracy.
In the process flow, in order to control the temperature of the substrate not to be too high, the whole etching process can be divided into dozens of cycles, and each cycle comprises three processes of etching, passivating and cooling.
Example three: testing and characterization of molds and microfluidic chips processed
FIG. 3 is a cross-sectional view of a glass mold processed according to the above-described method. Controlling the gas atmosphere: argon and C4F8, time: 3900 seconds, air pressure: 0.1 Pa, power: 20 watts, resulting microstructure: depth was 22.1 microns and side slope angle <90 °.
FIG. 4 shows a high-precision metallic nickel mold fabricated using the base mold, sized to fit an optical disc injection molding machine, which can be assembled to a conventional optical disc injection molding machine; because the inclination angle of the side wall of the obtained metal mold is less than 90 degrees, the automatic demolding of the injection molded micro-channel substrate is facilitated.
Fig. 5 shows that the chip microstructure processed by using the metal mold of fig. 4 is clear, has a smooth surface, and is suitable for most application fields of microfluidic chips.
It is to be understood that the invention disclosed is not limited to the particular methodology, protocols, and materials described, as these may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention which will be limited only by the appended claims.
Those skilled in the art will also recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.
Claims (6)
1. A method of fabricating a microfluidic chip having a height dimension of between 2 and 200 microns, the method comprising the steps of:
step 1: transferring the design pattern of the microfluidic chip drawn on the mask to a mold substrate in a graphical mode by utilizing a photoetching process; when the height size of the microfluidic chip is between 2 and 50 micrometers, using a substrate made of silicon, quartz or glass as the mold substrate; when the height size of the microfluidic chip is larger than 50 micrometers, using a silicon, quartz or glass substrate with a surface deposited with a metal film as the mold substrate;
step 2: etching the part, which is not protected by the photoresist, on the substrate by using a deep etching process, wherein the atmosphere of deep etching gas is argon and C4F8, the whole etching process is divided into dozens of cycles, and each cycle comprises three processes of etching, passivation and cooling to form a substrate mold;
and step 3: covering a metal layer on the substrate mould, processing a metal mould by using a precision electroforming process, wherein the surface flatness of the metal mould is in a nanometer level, the specification and the size of the metal mould are matched with those of an optical disk injection molding machine, and the metal mould is assembled on a traditional optical disk injection molding machine; and the inclination angle of the side wall of the metal mold is less than 90 degrees, which is beneficial to automatic demolding of the injection molded micro-channel substrate; and
and 4, step 4: and performing injection molding on the metal mold by using an integrated optical disk injection molding technology to obtain the microfluidic chip.
2. The processing method according to claim 1, characterized in that: the thickness of the metal film is 2-10 microns.
3. The processing method according to claim 1, characterized in that: the metal film material is aluminum.
4. The processing method according to claim 1, characterized in that: and covering a metal layer which is a metal chromium layer or a metal nickel layer on the substrate mould.
5. The processing method according to claim 1, characterized in that: the metal mold material is nickel.
6. The processing method according to claim 1, characterized in that: and covering the metal layer on the substrate mould by an evaporation or sputtering mode.
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| CN110963457A (en) * | 2018-09-29 | 2020-04-07 | 中国科学院微电子研究所 | High-precision micro-channel network manufacturing method |
| CN109550526A (en) * | 2018-12-04 | 2019-04-02 | 西北农林科技大学 | A kind of micro-fluidic chip prepares mold and its preparation process and application |
| CN109395790B (en) * | 2018-12-11 | 2024-03-29 | 福州大学 | Paper-based composite three-dimensional micro/nano circuit and processing method thereof |
| CN110152748B (en) * | 2019-06-12 | 2022-03-15 | 河北工业大学 | Method for cutting micro-droplets in micro-fluidic chip |
| CN110773245A (en) * | 2019-11-01 | 2020-02-11 | 上海速创诊断产品有限公司 | Microfluidic chip and processing method thereof |
| CN111135880B (en) * | 2019-12-09 | 2021-10-15 | 中国科学院微电子研究所 | Tractor, traction system and gravity measuring method thereof |
| CN111216288A (en) * | 2020-02-28 | 2020-06-02 | 中国科学技术大学 | Micro-channel mold surface treatment method and micro-channel chip manufacturing method |
| CN112099313A (en) * | 2020-09-22 | 2020-12-18 | 苏州微赛智能科技有限公司 | Photoresist coating system and photoresist coating method |
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| TW200528925A (en) * | 2004-02-20 | 2005-09-01 | Hon Hai Prec Ind Co Ltd | A manufacturing method of a light guide plate |
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| CN1405561A (en) * | 2002-11-07 | 2003-03-26 | 上海交通大学 | Method for preparing micro-flow-control analysing chip of silastic-glass permanent binding type |
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