Manufacturing process of micro-fluidic chip with various microstructures

Abstract

The invention discloses a manufacturing process of a micro-fluidic chip with various microstructures, and relates to the technical field of manufacturing of fluidic chips. The method comprises the following steps that S1, a substrate is provided, multi-layer photoresist spin coating treatment is sequentially carried out on the substrate, and the thicknesses of all layers of photoresist are different, so that microstructure female dies with different heights are formed; and S2, performing exposure, post-baking and developing treatment on each layer of photoresist by using a mask plate. According to the invention, integrated design and manufacturing of microstructures with different heights and different functions can be realized in one female die through multiple spin-coating and layered exposure technologies, multiple complex microstructures can be copied in a high-fidelity manner by using good forming capability and transparency of a PDMS material, and no leakage and firm packaging of a chip are ensured through a plasma bonding technology. The manufacturing process is high in universality and can be widely applied to research, development and manufacturing of multifunctional integrated micro-fluidic chips, the processing difficulty and alignment errors are reduced, and the chip yield and the functional density are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microfluidic chip manufacturing, and particularly relates to a manufacturing process of a microfluidic chip with multiple microstructures. BACKGROUND

[0002] Microfluidic chip technology realizes high-throughput, low-loss and high-sensitivity processing of chemical and biological samples by regulating liquid flow in a micron-scale space. The existing microfluidic chip has various structure types, including straight channels, branch mixers, cell capture holes, droplet generators and concentration gradient structures. These microstructures often correspond to different functional requirements and have obvious differences in size, shape and spatial distribution.

[0003] However, in the existing microfluidic chip manufacturing process, it is difficult to integrate multiple microstructures with significant differences in depth and function on a chip with high precision due to the limitation of single exposure or the structural uniformity of one-time molds. Even if multiple processes are used, there are problems such as large interlayer alignment error, complex repeated process, poor material compatibility and high cost, which restrict the industrialization and practicality of multifunctional microfluidic chips.

[0004] Therefore, a manufacturing process of a microfluidic chip with multiple microstructures is provided. SUMMARY

[0005] The present application aims to solve the problems raised in the background art and provides a manufacturing process of a microfluidic chip with multiple microstructures.

[0006] To achieve the above-mentioned purpose, the present application specifically adopts the following technical solutions: A manufacturing process of a microfluidic chip with multiple microstructures, comprising the following steps: Step S1: providing a substrate, and sequentially performing multi-layer photoresist spin coating treatment on the substrate, each layer of photoresist having a different thickness for forming microstructure master molds with different heights; Step S2: using a mask for each layer of photoresist to perform exposure, post-baking and development treatment, thereby forming an SU-8 master mold with multiple microstructure combinations including microchannels, microcolumn arrays, reaction cavities, mixing structures and the like; Step S3: using polydimethylsiloxane (PDMS) to flip the SU-8 master mold, and after curing, demolding to obtain a PDMS microstructure layer; Step S4: aligning the PDMS microstructure layer with a cover layer, and then bonding by plasma treatment to obtain an integrated microfluidic chip.

[0007] Further, the multi-layer photoresist includes at least two layers of SU-8 photoresist with different thicknesses, wherein the first layer is 510 μm thick and used for forming a high-resolution micro-pillar array, and the second layer is 20100 μm thick and used for forming a large-volume channel or reaction cavity.

[0008] Further, in step S2, each layer pattern is exposed and controlled by an independent mask to realize the structural differentiation design between different functional areas and ensure the communication or functional isolation between functional structures.

[0009] Further, in the step S3, the PDMS microstructure built in the SU-8 master mold includes the following steps: Step S31: Gradient generating structure, used for solution concentration gradient generation; Step S32: Bifurcated mixing structure, used for liquid mixing reaction; Step S33: Micro-pore array structure, used for single-cell capture or particle screening; Step S34: Droplet generator structure, used for encapsulation reaction or drug distribution.

[0010] Further, the PDMS microstructure layer and the cover layer are bonded at room temperature after oxygen plasma treatment, forming a leak-free closed microfluidic structure.

[0011] Further, the cover layer is a PDMS cover layer with inlet and outlet through-hole structure or a glass substrate with pre-prepared through-hole, and the through-hole serves as the liquid inlet and outlet of the microfluidic chip.

[0012] Further, in the step S3, the PDMS material is cured at 80°C for 1-2 hours, and a defoaming treatment is performed before curing to ensure the complete formation of the microstructure.

[0013] Further, after the SU-8 master mold is completed, the surface is treated by metal ion evaporation or fluorine release agent to enhance the release efficiency and molding quality of the PDMS replica.

[0014] The beneficial effects of the present application are as follows: Through multiple spin coating and layer-by-layer exposure technology, the integrated design and fabrication of microstructures with different heights and different functions can be realized in one master mold. By utilizing the good molding ability and transparency of PDMS material, a variety of complex microstructures can be reproduced with high fidelity. Through the plasma bonding process, the chip is ensured to be leak-free and firmly packaged. The manufacturing process is versatile and can be widely used in the research and development and manufacturing of multifunctional integrated microfluidic chips, reducing the processing difficulty and alignment error, and improving the chip yield and functional density. BRIEF DESCRIPTION OF DRAWINGS

[0015] Fig. 1is a process flow chart of the present application; Fig. 2 is a process flow chart of the PDMS microstructure constructed in the SU-8 master of the present application. DETAILED DESCRIPTION

[0016] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0017] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0018] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0019] In the description of the embodiments of the present application, it should be noted that the terms "inner", "outer", "upper", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the present application is usually placed, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, therefore, it cannot be understood as a limitation on the present application.

[0020] As shown in Figs. 1-2 A manufacturing process of a microfluidic chip with multiple microstructures, at least comprising the following steps: Step S1: providing a substrate, and sequentially performing multi-layer photoresist spin coating treatment on the substrate, each layer of photoresist having a different thickness, for forming a microstructure master with different heights; Step S2: using a mask for each layer of photoresist to perform exposure, post-baking and development treatment, to form an SU-8 master with multiple microstructure combinations including microchannels, microcolumn arrays, reaction cavities, mixing structures, etc.; In some practical applications, in step S2, each layer pattern is exposed and controlled by an independent mask to realize the structural differentiation design between different functional areas and ensure the connectivity or functional isolation between functional structures.

[0021] Step S3: SU-8 master mold is flipped using polydimethylsiloxane (PDMS) to obtain a PDMS microstructure layer after curing and demolding; In some practical applications, in step S3, the PDMS microstructure step constructed in the SU-8 master mold includes the following steps: In some practical applications, in step S3, the PDMS material is cured at 80°C for 1-2 hours, and a degassing process is performed before curing to ensure complete formation of the microstructure Step S31: Gradient generating structure, used for solution concentration gradient generation; Step S32: Bifurcated mixing structure, used for liquid mixing reaction; Step S33: Micropore array structure, used for single cell capture or particle screening; Step S34: Droplet generator structure, used for encapsulation reaction or drug distribution.

[0022] Step S4: After aligning the PDMS microstructure layer with the cover layer, the integration of the microfluidic chip is obtained by plasma treatment.

[0023] In some practical applications, the multi-layer photoresist includes at least two layers of SU-8 photoresist with different thicknesses, wherein the first layer is 510μm thick and used to form a high-resolution microcolumn array, and the second layer is 20100μm thick and used to form a large-volume channel or reaction cavity.

[0024] In some practical applications, the PDMS microstructure layer and the cover layer are bonded at room temperature after oxygen plasma treatment, forming a leak-free closed microfluidic structure; the cover layer is a PDMS cover layer with inlet and outlet through-hole structure or a glass substrate with pre-prepared through-hole, which serves as the liquid inlet and outlet of the microfluidic chip.

[0025] In some practical applications, after the SU-8 master mold is completed, the surface is treated by metal ion evaporation or fluorine release agent to enhance the demolding efficiency and molding quality of PDMS re-molding.

[0026] Example One: Master mold making: On a clean and dry silicon wafer, spin-coat the first layer of SU-8 photoresist (8 μm thick), pre-bake, expose, post-bake, and develop to form a micro-pillar array structure; then spin-coat the second layer of SU-8 (30 μm thick), mask and expose again to form a reaction chamber and branch mixer structure; if a gradient structure or droplet generator is needed, a third layer of photoresist (e.g., 50 μm thick) can be applied.

[0027] PDMS reverse molding: Mix the PDMS prepolymer and crosslinking agent at a ratio of 10:1, stir, and degas; then pour the mixture onto the surface of the SU-8 master mold and place it in a vacuum box for 30 minutes; remove the mold from the 80°C oven after curing for 90 minutes, and slowly peel off the PDMS microstructure layer.

[0028] Chip packaging: Oxygen plasma treat the PDMS microstructure layer and the PDMS cover sheet with pre-made inlet and outlet through-holes for 30 seconds, and then align and bond them; place the bonded chip at room temperature for 30 minutes to solidify the bonding interface, and the packaging of the microfluidic chip is complete.

[0029] Application example: The chip can simultaneously perform concentration gradient mixing, cell capture, droplet generation, and other multi-functional operations, and is suitable for drug screening, single-cell analysis, and micro-chemical reactions.

[0030] Example two: Master mold fabrication: On a clean and dry 4-inch silicon wafer, spin-coat the first layer of SU-8 2005 photoresist (about 5 μm thick), pre-bake, and expose through a first mask to form a high-resolution cell capture micropore array structure; spin-coat the second layer of SU-8 2025 photoresist (about 25 μm thick), and expose through a second mask to form a Y-shaped branch mixer structure and main channel structure; spin-coat the third layer of SU-8 2050 photoresist (50 μm thick), and expose through a third mask to form a droplet generator structure and large reaction chamber structure; finally, uniformly post-bake and develop to obtain a SU-8 master mold with three integrated functional structures.

[0031] PDMS reverse molding: Mix the PDMS prepolymer and crosslinking agent at a ratio of 10:1, stir, and degas for 15-30 minutes in a vacuum; pour the mixture into the SU-8 master mold to completely cover all the microstructure areas; place the poured mold in a 80°C constant temperature oven for about 1.5 hours, and then slowly peel off the PDMS layer to obtain a complete multifunctional microstructure PDMS chip layer.

[0032] Chip packaging: The PDMS microstructure layer and a piece of prefabricated through-hole glass substrate are subjected to surface activation treatment by oxygen plasma treatment, the treatment parameters are 30W and 30 seconds; alignment is performed under a microscope, and then bonding is completed at room temperature after standing for 30 minutes, so that a multifunctional microfluidic chip integrated with a capture zone, a mixing zone, a reaction zone and a droplet zone is obtained.

[0033] Chip function verification: The chip is used for multiphase flow droplet generation experiment, oil phase and water phase are respectively introduced from the two side inlets of the droplet structure, and oil-in-water droplets with a diameter of about 80-120μm can be stably generated; at the same time, cell suspension is injected into the chip inlet, and single cell capture effect is realized in the micropore array area, and the mixing zone can effectively and uniformly mix two kinds of reagents; the experimental results show that the function of each region is clear, the fluid is smooth, the microstructure replication precision is high, and the chip has good application performance and structural integration.

[0034] In summary: through multiple spin coating and layer exposure technology, integrated design and manufacture of different height and different function microstructures can be realized in one master mold, by using the good forming ability and transparency of PDMS material, a variety of complex microstructures can be replicated with high fidelity, and by using the plasma bonding process, the chip is ensured to be leak-proof and firmly packaged, the manufacturing process is universal, and can be widely applied to the research and manufacture of multifunctional integrated microfluidic chip, reduces the processing difficulty and alignment error, and improves the chip yield and functional density.

[0035] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection claimed by the present application is defined by the appended claims and their equivalents.

Claims

1. A fabrication process for a microfluidic chip with multiple microstructures, characterized in that, Includes the following steps: Step S1: Provide a substrate and perform multi-layer photoresist spin coating on the substrate in sequence. Each layer of photoresist has a different thickness to form a microstructure master mold of different heights. Step S2: Expose, bake and develop each layer of photoresist using a mask to form the SU-8 master mold, which includes a variety of microstructures such as microchannels, micropillar arrays, reaction chambers and hybrid structures. Step S3: The SU-8 master mold is made by casting polydimethylsiloxane (PDMS), and after curing, it is demolded to obtain the PDMS microstructure layer; Step S4: After aligning the PDMS microstructure layer and the capping layer, they are bonded by plasma treatment to obtain an integrated microfluidic chip.

2. The fabrication process of a microfluidic chip with multiple microstructures according to claim 1, characterized in that, The multilayer photoresist includes at least two layers of SU-8 photoresist with different thicknesses, wherein the first layer is 510 μm thick and is used to form a high-resolution micropillar array, and the second layer is 20100 μm thick and is used to form a large-volume channel or reaction chamber.

3. The fabrication process of a microfluidic chip with multiple microstructures according to claim 1, characterized in that, In step S2, the exposure of each layer pattern is controlled by an independent mask to achieve structural differentiation between different functional areas and to ensure that the functional structures remain connected or functionally isolated.

4. The fabrication process of a microfluidic chip with multiple microstructures according to claim 1, characterized in that, In step S3, the PDMS microstructure construction step in the SU-8 master mold includes the following steps: Step S31: Gradient generation structure, used to generate solution concentration gradient; Step S32: Bifurcation mixing structure, used for liquid mixing reactions; Step S33: Micropore array structure for single-cell capture or particle sieving; Step S34: Droplet generator structure for encapsulating reaction or drug dispensing.

5. The fabrication process of a microfluidic chip with multiple microstructures according to claim 1, characterized in that, The PDMS microstructure layer and the capping layer are bonded together at room temperature after oxygen plasma treatment to form a leak-free closed microfluidic structure.

6. The fabrication process of a microfluidic chip with multiple microstructures according to claim 5, characterized in that, The capping layer is a PDMS capping layer with an inlet and outlet through-hole structure or a glass substrate with pre-formed through-holes, and the through-holes serve as the liquid inlet and outlet of the microfluidic chip.

7. The fabrication process of a microfluidic chip with multiple microstructures according to claim 1, characterized in that, In step S3, the PDMS material is cured at 80°C for 1 to 2 hours. Before curing, a degassing treatment is performed to ensure the complete formation of the microstructure.

8. The fabrication process of a microfluidic chip with multiple microstructures according to claim 1, characterized in that, After the SU-8 master mold is made, its surface is treated with metal ion vapor deposition or fluorine release agent to enhance the demolding efficiency and molding quality during PDMS demolding.

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