KR20230155108A - Microfluid chip using Epoxy casting and Manufacturing Method thereof - Google Patents

Abstract

The present invention relates to a microfluidic chip using epoxy casting and a method for manufacturing the same. More specifically, the present invention relates to a microfluidic chip that can be applied to microfluidic systems that require high chemical resistance and durability by preventing sample absorption and deformation by pressure. This relates to a microfluidic chip using epoxy casting and its manufacturing method.
The method of manufacturing a microfluidic chip using epoxy casting of the present invention includes a master mold manufacturing step (S100); and a microfluidic channel layer of manufacturing an epoxy microfluidic channel layer by applying and curing an epoxy resin composition on the produced master mold. A forming step (S200); and a substrate coating step (S300) of applying an epoxy resin composition to the substrate to manufacture a substrate with an epoxy coating film formed thereon; and a bonding step of bonding the microfluidic channel layer to the substrate with an epoxy coating film formed on it (S400). Includes.

Description

Microfluid chip using Epoxy casting and Manufacturing Method thereof}

The present invention relates to a microfluidic chip using epoxy casting and a method for manufacturing the same. More specifically, the present invention relates to a microfluidic chip that can be applied to microfluidic systems that require high chemical resistance and durability by preventing sample absorption and deformation by pressure. This relates to a microfluidic chip using epoxy casting and its manufacturing method.

Microfluidics has been applied to areas such as environmental and medical problems and has provided solutions for the past several decades. Especially in relation to COVID-19, the importance of microfluidics in the diagnostic field is growing, and many studies are being conducted. As such, outstanding research results in the field of microfluidics have been applied to various fields, leading to many attempts to manufacture microfluidic devices. In particular, appropriate selection of microfluidic device materials makes experiments in various environments possible, and attempts have been made to manufacture microfluidic devices using various materials.

In general, polydimethylsiloxane (PDMS) has been mainly used to manufacture microfluidic devices. PDMS is a relatively inexpensive material and has excellent transparency, and microfluidic devices made from this material use a soft lithography method, so the process is simple and easy, making it suitable for use in experiments. In particular, the material's flexibility and air permeability are the main advantages of PDMS. But interestingly, there are times when the main advantage also acts as a disadvantage. For example, the flexibility of PDMS can cause it to deform at high pressures, and its air permeability can lead to absorption inside the device.

To overcome these shortcomings, alternative materials to PDMS have been studied. To prevent deformation and air permeability, there is a method of creating a channel by etching the glass itself. This method has the advantage of superior transparency and stability against heat and chemical reactions over PDMS. Another material is low-temperature co-fired ceramic, which has excellent high-temperature stability, mechanical strength, and chemical resistance, and has good manufacturing reproducibility. Additionally, much research has been done on how to manufacture microfluidic devices using plastic. In particular, manufacturing using hot embossing has the advantage of excellent reproducibility and being suitable for mass production as it is manufactured using equipment. However, despite the advantages of the materials mentioned above, they have the disadvantage of being difficult to manufacture in the laboratory because they require equipment and molds for production.

Therefore, in order to overcome the shortcomings of PDMS, the present inventor would like to propose a plastic microfluidic chip (PMFC) that uses simple materials, has excellent durability, and is simple to manufacture so that it can be manufactured in a laboratory unit. First, the present inventor fabricated a PMFC based on a PDMS channel, measured the dimensions of the channel of the fabricated PMFC, and confirmed the reliability of the fabrication process by comparing it with a PDMS channel of the same size. Second, the deformation of the channel was confirmed by measuring the flow rate of the channel according to the flow rate using particles. The deformation of the channel can be confirmed by the linearity of the change in flow rate according to the flow rate. Third, the air permeability of PMFC was confirmed through the diffusion of fluorescence over time between PDMS and PMFC using fluorescent particles, proving that PMFC hardly absorbs anything. Lastly, unlike PDMS, which absorbs water by compartmentalizing fluorescent particles inside the microdevice, it was demonstrated that PMFC has almost no air permeability, making it possible to conduct long-term experiments.

Domestic Published Patent No. 10-2021-0060350 Domestic Published Patent No. 10-2022-0002071 Domestic Registered Patent No. 10-1399511

The purpose of the present invention to solve the above problems is to provide a microfluidic chip using epoxy casting and its It provides a manufacturing method.

The method of manufacturing a microfluidic chip using epoxy casting of the present invention to solve the above problem includes a master mold manufacturing step (S100); and applying and curing an epoxy resin composition on the produced master mold to form an epoxy microfluidic channel layer. A microfluidic channel layer forming step (S200); and a substrate coating step (S300) of manufacturing a substrate with an epoxy coating film by applying an epoxy resin composition to the substrate; and bonding the microfluidic channel layer to a substrate with an epoxy coating film formed on it. It includes a joining step (S400).

The epoxy resin composition of the microfluidic channel layer forming step (S200) and the substrate pretreatment step (S300) is characterized by mixing 20 to 40 parts by weight of a curing agent with respect to 100 parts by weight of the epoxy resin.

The bonding step (S400) is characterized by heat treatment bonding at 55 to 65°C for 1 to 5 minutes.

The microfluidic chip using epoxy casting of the present invention is characterized in that it is manufactured through the method of manufacturing a microfluidic chip using epoxy casting described above.

As described above, the microfluidic chip using epoxy casting according to the present invention and its manufacturing method are designed to prevent deformation due to absorption and pressure of the sample due to the high air permeability of polydimethylsiloxane (PDMS), which is used to manufacture conventional microfluidic devices. To overcome this limitation, microfluidic chips are manufactured using epoxy, which has low air permeability and excellent physical properties, thereby preventing sample absorption and deformation due to pressure, making it possible to create a microfluidic system that requires high chemical resistance and durability. It has effects that can be applied to application fields.

1 is a flowchart of a method for manufacturing a microfluidic chip using epoxy casting according to the present invention.
In Figure 2, (a) is a process flow chart, (b) is a photograph of a manufactured microfluidic chip sample, and (c to e) are various examples of microfluidic chips.
Figure 3 (a) is a cross-sectional photograph of the manufactured PDMS channel and PMFC channel, and (b, c) is a graph comparing the actual sizes.
Figure 4 (a) is a schematic diagram of channel deformation observed in conventional PDMS, (b) is a particle movement speed according to the exposure time and flow rate of PDMS and PMFC, (c) is a trajectory photo according to the flow speed, and (d) is a picture of the trajectory according to the flow speed. A graph showing the change in particle speed according to flow speed.
Figure 5 (a) is a schematic diagram showing the adsorption characteristics of PDMS and PMFC for fluorescent particles, and (b) is the adsorption result of a material expressing red fluorescent protein (RFP) according to time (0.5 to 8 hr). (c) is a graph showing the intensity of the fluorescent material.
Figure 6 (a,b) is a schematic diagram showing the suitability of PDMS and PMFC for long-term experiments, (c) is a photograph showing the movement of particles over time, (d) is a graph showing the Z-axis movement distance over time, ( e) is a graph showing particle speed over time.

Specific features and advantages of the present invention will be described in detail below with reference to the accompanying drawings. Prior to this, if it is determined that a detailed description of the functions and configuration related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

The present invention relates to a microfluidic chip using epoxy casting and a method for manufacturing the same. More specifically, the present invention relates to a microfluidic chip that can be applied to microfluidic systems that require high chemical resistance and durability by preventing sample absorption and deformation by pressure. This relates to a microfluidic chip using epoxy casting and its manufacturing method.

Figure 1 shows a flow chart of a method for manufacturing a microfluidic chip using the epoxy casting of the present invention according to the present invention.

The method of manufacturing a microfluidic chip using epoxy casting of the present invention includes a master mold manufacturing step (S100) and forming a microfluidic channel layer by applying and curing an epoxy resin composition on the produced master mold to manufacture an epoxy microfluidic channel layer. It includes a step (S200), a substrate coating step (S300) of manufacturing a substrate with an epoxy coating film by applying an epoxy resin composition to the substrate, and a bonding step (S400) of bonding the microfluidic channel layer to the substrate with the epoxy coating film formed. .

In the master mold production step (S100), a PDMS master mold for microfluidic chip production using epoxy is produced. To fabricate a PDMS master mold, the engraved PDMS microfluidic chip is coated with trichloro(3,3,3-trifluoropropyl)silane (hereinafter referred to as silane). Afterwards, the master mold is produced by applying the PDMS solution to the silane-coated PDMS fluid chip and curing it.

In the microfluidic channel layer forming step (S200), an epoxy microfluidic channel layer is manufactured by applying and curing an epoxy resin composition on the manufactured master mold.

The epoxy resin composition uses an epoxy resin as a base resin, and a curing agent for curing the epoxy resin is mixed. After mixing the epoxy resin and the curing agent, bubbles are removed through a degassing process in a vacuum chamber.

The epoxy resin composition is a mixture of 20 to 40 parts by weight of a curing agent based on 100 parts by weight of the epoxy resin, and preferably, 30 parts by weight of a curing agent is mixed with 100 parts by weight of the epoxy resin.

The curing agent is not limited as long as it is for curing the epoxy resin, which is the base resin, but preferably includes at least one of primary amines, secondary amines, and acid anhydrides with which the ring-opening portion of the epoxy group can react.

The prepared epoxy resin composition is applied on the prepared master mold and cured at room temperature of 15 to 25°C for 12 to 36 hours to form an epoxy microfluidic channel layer.

In the substrate coating step (S300), an epoxy resin composition is applied to a substrate to manufacture a substrate with an epoxy coating film. The epoxy resin composition is applied, spin-coated at 1000 to 3000 rpm for 15 to 45 seconds, and then cured.

The epoxy resin composition for forming the epoxy coating film may be the same as the epoxy resin composition mentioned in the microfluidic channel layer forming step (S200) described above.

In the bonding step (S400), the microfluidic channel layer is bonded to a substrate on which an epoxy coating film is formed, and heat treatment bonding is performed at 55 to 65° C. for 1 to 5 minutes.

Hereinafter, a microfluidic chip using epoxy casting according to the present invention will be described.

The microfluidic chip using epoxy casting of the present invention is manufactured through the method of manufacturing a microfluidic chip using epoxy casting described above, and detailed description thereof will be omitted.

The manufactured microfluidic chip was By manufacturing microfluidic chips using epoxy, which has low air permeability and excellent physical properties, it is possible to prevent sample absorption and deformation due to pressure, making it applicable to applications in microfluidic systems that require high chemical resistance and durability. there is.

Hereinafter, the present invention will be described in detail below with reference to a preferred embodiment. However, the following examples are intended to specifically illustrate the present invention and are not limited thereto.

EXPERIMENTAL

Materials and reagents

The PMFC used in the experiment was manufactured using epoxy resin (EpoxAcast 690, Smooth-on, Macungie, PA, USA). PDMS (Sylgard 184, K1Solution, Gyeonggi-do, Korea) was used to fabricate a microfluidic device for comparison with PMFC.

Table 1 below shows the physical properties of PDMS and epoxy resin.

Yellow-green fluorescent polystyrene particles (Latex beads, Sigma-Aldrich, Seoul, Korea) with a diameter of 1 um were diluted 1:1000 in distilled water (DW) and used to visualize the flow rate and observe the flow inside the compartmentalized chamber. . Rhodamine B (Sigma-Aldrich, Seoul, Korea) was used diluted to 10 uM in DW to check air permeability by staining the channel. Fluorocarbon oil (Fluorinert FC-40, Sigma-Aldrich, Seoul, Korea) was used to compartmentalize the microchamber and prevent evaporation inside the chamber.

Fabrication of master mold

The microfluidic device was fabricated using standard photolithography. To create a double layer, negative photoresist (SU-8 2025, MicroChem, Newton, MA, USA) was spin-coated on a silicon wafer (Unisill, Seoul, South Korea) as the first layer (25 um), followed by soft baking. After exposure to UV light using a photomask (Microtech, Gyeonggi-do, Korea) and mask aligner (MDA-60MS, MidasSystem, Daejeon, Korea), the second layer (100 um) was spin coated and soft baked. . After exposing the wafer to UV light with a second mask and mask aligner, a double-layer master mold is produced by dipping the wafer in developer (SU-8 developer, Kayaku Advanced Materials, Westborough, MA, USA) to remove unexposed photoresist. do.

The 30 um and 60 um high channels used in the experiment were also produced using standard photolithography according to the manufacturer's manual. Subsequently, the surface of the master mold was silanized using trichloro(3,3,3-trifluoropropyl)silane (Sigma-Aldrich, Seoul, Korea).

For the PDMS device, sylgard 184 was mixed at a ratio of 10 A: 1 B, degassed in a vacuum chamber, poured into a master mold, and cured at 60°C for 4 hours. Immediately afterwards, the PDMS device and the glass substrate are bonded by oxygen plasma treatment at ₅₀ sccm and 50 W for 4-7 seconds (Cute-MP, Femto science, Gyeonggi-do, Korea). After integration, it was coated with 0.01% pluronic surfactant (F-127, Sigma-Aldrich, Seoul, Korea) to minimize nonspecific binding between molecules and microchannels. To prevent contamination, the microfluidic device was used only once per experiment.

Plastic chip design and fabrication plastic

The process of manufacturing PMFC was carried out as shown in Figure 2a. First, to fabricate a PMFC master mold, the surface of the PDMS device was treated with silane, and the PDMS solution was poured on it and cured. At this time, the two materials are the same material, but their surfaces are coated with silane, so they can be easily separated. Second, to produce PMFC and epoxy-coated glass, epoxy resin is mixed at a weight ratio of 10 A (epoxy):3 B (epoxy hardener) and then degassed in a vacuum chamber. Pour epoxy resin into the separated PDMS device and cure under room conditions for 24 hours. Epoxy resin was poured onto the slide glass, spin-coated at 2000 rpm for 30 seconds, and then cured as in PMFC production. Finally, a whole plastic device was manufactured by heat-treating the completed plastic device and epoxy-coated glass at 60°C for 3 minutes on a hot plate (Figure 2b). For the same reasons as PDMS, pluronic surfactant was flushed under the same conditions, and PMFC was also used only once per experiment to prevent contamination. As shown in Figure 2a, it can be manufactured as a single chip, but it can also be manufactured on a wafer scale, and channels of various shapes such as membranes can also be copied (Figures 2c to 2e).

Experimental setup and data analysis

A digital fluorescence microscope (F1-CIS, Nanoscope Systems, Daejeon, Korea) equipped with a CCD camera and lens was used to obtain bright field images and images of green fluorescent protein (GFP) and red fluorescent protein (RFP). A syringe pump (NE-1000, New Era Pump Systems, Inc., NY, USA) was used to control the flow rate in the channel. imageJ (NIH, Bethesda, MD, USA) was used to measure the specifications of the microchannel, the fluorescence intensity of the fluorescent sample, and the moving distance of the particles. Origin 9.0 (OriginLab, Northampton, NC, USA) was used for data analysis, including graphs.

RESULTS AND DISCUSSIONS

fabrication error

Figure 3a shows a cross section of a PDMS channel and a PMFC manufactured based on it. Although the cross section of PMFC looks a little rougher than that of PDMS, the difference is only due to the fact that PDMS can be cut with a blade, whereas PMFC can be cut with a cutting tool such as a band saw, and the transparency is the same. It can be seen with the naked eye that the sizes of the channels are similar, and the sizes of the cross sections of PDMS and PMFC are compared in Figures 3b and 3c. Channels of two heights were compared using a master mold made of 30 um and 60 um layers, and channel widths were measured for 25, 50, 100, 200, 400, and 800 um. As a result of measuring the cross-sectional size, it can be confirmed that the change in channel size that occurs while fabricating PMFC is minimal.

Channel deformation depending on pressure

It is well known that microfluidic channels made of PDMS are deformed when subjected to pressure. As shown in Figure 4a, when the pressure is low, the channel is hardly deformed, but when a relatively high pressure is applied, the channel is deformed. . Deformation of the channel results in a change in flow rate, which is sufficient to affect the results of experiments requiring high pressure. In particular, in the case of inertia microfluidics, the fluid is pushed with considerable pressure, so the deformation of the channel is severe and there are cases where the channel even bursts.

However, in the case of epoxy, this disadvantage can be overcome because the elasticity is very low compared to PDMS. Accordingly, PMFC compared the speeds of the two channels according to flow rate to prove that there was no deformation. If a solution containing fluorescent particles is pushed into a channel at a constant flow rate using a pump and the flow is photographed using a microscope, the distance the particles moved during the exposure time can be known. The flow rate was calculated by dividing the distance of the particles by the exposure time, and the reliability of the measurement was confirmed by the fact that the flow rate at the same flow rate was the same and that when the flow rate was doubled, the flow rate also doubled (Figure 4b). Figure 4c is a photograph measuring the movement of particles in two channels using the aforementioned method, and it was confirmed that the trajectory of the particles becomes longer as the flow rate increases. After measuring the length of all particles visible in the photo, only the trajectories corresponding to the top 30% of the lengths were used for velocity measurement under the assumption of a fully developed flow. The speed measurement results can be seen in Figure 4d. In the case of PMFC, the speed increases almost linearly as the flow rate increases, while in the case of PDMS, it can be seen that it increases linearly to a certain extent and then deviates from the trend. Even at low flow rates, the speed of PDMS is seen to be lower than that of PMFC to a certain extent. It can be seen that there was a change in the channel.

fluorescence adsorption

Because PDMS has air permeability properties, the liquid inside the channel is absorbed and appears to evaporate, and small molecules are also absorbed in this process. Accordingly, PDMS was judged to be an unsuitable material for long-term experiments, and therefore, a fluorescence adsorption test was conducted for 8 hours to prove this. Looking at the flow chart of the experiment in Figure 5a, when a solution mixed with rhodamine B (RB) is flowed through the channel, in the case of PDMS, RB is adsorbed, and over time, fluorescence spreads along the edge of the channel and the fluorescent intensity becomes stronger. .

On the other hand, in the case of epoxy, since there is no air permeability, RB is not adsorbed to PMFC and therefore fluorescence does not appear in the channel over time. The experiment was conducted over a total of 8 hours, and to confirm the adsorption of fluorescence, cross-sections of the channel were cut over time and RFP was photographed under a microscope. As a result of cutting cross sections every 0.5, 2, 4, and 8 hr, it can be seen that the fluorescence of PDMS diffuses over time, but the fluorescence of PMFC does not diffuse over time (Figure 5b). Figure 5c shows quantitative results based on diffusion. As a result of measuring the fluorescence intensity along the y-axis based on the centerline of the channel, as seen in the cross-sectional photograph, it can be seen that the fluorescent intensity gradually increases with diffusion in PDMS, while there is no change in PMFC.

Particle compartmentalization

In the previous experiment, it was confirmed that PDMS is not suitable for long-term experiments. Therefore, to prove that PMFC is more suitable for long-term experiments than PDMS, an experiment was conducted to check evaporation of the channel over 24 hours as follows. To check evaporation inside the channel, an aqueous solution of latex beads showing GFP diluted in DW was used. The progress of the experiment is shown in Figure 6a. If the aqueous solution is added first, the microchamber is not properly filled, so the inside of the microchamber is first filled using the amphiphilic property of isopropyl alcohol. And when filling the aqueous solution, flush it with the aqueous solution for sufficient time so that the solution inside the channel is replaced. Afterwards, fluorocarbon oil is injected using a syringe to trap the aqueous solution in the chamber. Since the density of fluorocarbon oil is higher than DW, the aqueous solution can be confined in the chamber. If a compartmentalized chamber is created and placed under RT conditions, over time, the water in the PDMS chamber evaporates due to air permeability and the particles adhere to the wall, whereas in the case of PMFC, evaporation does not occur, so the particles continue to undergo Brownian motion. (Figure 6b). The movement of particles over time can be seen in Figure 6c, and the experiment was conducted for a total of 24 hours. In the case of PDMS, Brownian motion is observed until the 6th hour, and from the 7th hour, the water in the channel completely evaporates and the movement stops. PMFC showed particle movement until 24 hours. In Figures 6D and 6E, the movement of the particles is graphed along the z-axis and in the plane. First, z-axis movement was measured with the bottom of the chamber as 0 according to the z-axis focusing of the microscope. Likewise, as shown in the photo, in the case of PMFC, the position continues to change as it moves along the z-axis, while PDMS stops moving after 7 hours (Figure 6d). For planar motion, even if the speed of the particle is calculated by measuring the distance it moves for 5 seconds after recording the particle's movement on video, the particle can be seen moving little by little over time, as shown in the photo in Figure 6e. It can be seen that PDMS stops moving after 7 hours, similar to z-axis movement, while PMFC continues to move.

Conclusion

In this study, the present inventor presented a PMFC that can overcome the shortcomings of PDMS and is easily manufactured through experiments on velocity changes according to flow rate using a simple syringe pump and long-term experiments using fluorescence. Through previous experiments, it was confirmed that PMFC is an ideal material than PDMS for experiments that require resistance to channel deformation due to pressure and chemical resistance such as fluorescence, as well as experiments in situations that require isolation from the external environment. PMFC, which is manufactured using a PDMS device as a master mold, has a very small error in the manufactured results (<0.3% @height) and can be easily manufactured with materials available in the laboratory without the need for casting using metals to manufacture plastic chips. Additionally, through appropriate design of the device, the present inventor confirmed that PDMS deformation occurs when the flow rate exceeds a certain flow rate (>5 mL/hr), confirming the PMFC's resistance to pressure. Moreover, the biggest advantage of PMFC is that long-term experiments are possible. Through fluorescence adsorption experiments, the present inventor confirmed that PMFC has excellent chemical resistance even in a short period of time through diffusion of fluorescence even in relatively short-term experiments (<8 hr). Furthermore, this was confirmed by successfully performing an evaporation experiment in a chamber using fluorescent particles that lasted 24 hours. Therefore, the present inventor believes that PMFC will be applied not only to simple experiments in microfluidics, but also to fields that require durability to withstand high pressure and chemical resistance.

As described above, the present invention has been described with a focus on preferred embodiments with reference to the accompanying drawings, but within the scope of those skilled in the art in the technical field to which the present invention pertains without departing from the technical spirit and scope described in the claims of the present invention. The present invention can be implemented with various modifications or modifications. Accordingly, the scope of the present invention should be construed by the appended claims to include examples of many such modifications.

Claims (4)

Master mold production step (S100); and
A microfluidic channel layer forming step (S200) of manufacturing an epoxy microfluidic channel layer by applying and curing an epoxy resin composition on the manufactured master mold; and
A substrate coating step (S300) of manufacturing a substrate with an epoxy coating film by applying an epoxy resin composition to the substrate;
Characterized by comprising a bonding step (S400) of bonding the microfluidic channel layer to a substrate on which an epoxy coating film is formed.
Method for manufacturing microfluidic chips using epoxy casting.
According to claim 1,
The epoxy resin composition of the microfluidic channel layer forming step (S200) and the substrate pretreatment step (S300) is characterized in that 20 to 40 parts by weight of a curing agent is mixed with 100 parts by weight of the epoxy resin.
Method for manufacturing microfluidic chips using epoxy casting.
According to claim 1,
The joining step (S400) is
Characterized by heat treatment bonding at 55 to 65°C for 1 to 5 minutes.
Method for manufacturing microfluidic chips using epoxy casting.
A microfluidic chip using epoxy casting manufactured by the method for manufacturing a microfluidic chip using epoxy casting according to any one of claims 1 to 3.