CN107308996B - Method for maintaining negative pressure state of micro-fluidic chip for long time - Google Patents

Abstract

The invention provides a method for maintaining the negative pressure state of a microfluidic chip for a long time. A layer of transparent tape is pasted on the surface of the microfluidic chip, and then a layer of polymer film is deposited on the surface of the microfluidic chip pasted with the transparent adhesive tape. The microfluidic chip obtains the negative pressure driving force by means of vacuuming. The present invention utilizes the properties of the polymer film to be dense, low permeability to gas molecules, colorless and transparent, and non-fluorescent to realize long-term storage of the negative pressure driving capability of the microfluidic chip, so that the negative pressure drives the microfluidic The control chip can be widely used, and it is more conducive to the use of negative pressure-driven sample injection for microfluidic chips that do not require an external power source, and can be used in remote areas and on-site timely detection. During chip injection, the deposited polymer film can still continue to protect the surrounding of the chip in a sealed state, preventing gas molecules from entering the chip from around the chip, and the injection effect is better, preventing the evaporation of reagents.

Description

A method for maintaining the negative pressure state of a microfluidic chip for a long time

technical field

The invention belongs to a detection method in the fields of life science, clinical diagnosis, chemical analysis and the like, and relates to a method for maintaining the negative pressure state of a microfluidic chip for a long time.

Background technique

Microfluidic chip technology has been widely used in biology, chemistry, medicine and many other fields. Compared with traditional laboratory detection and analysis methods, microfluidic chip technology has many advantages such as less sample required, simple operation, high throughput, high accuracy, and low pollution without opening the cover. It is the future development of detection technology. a major direction.

In practical applications of microfluidic chips, most of them require an external power source to provide power to drive the flow of samples in the chip. The external power source is usually bulky and complex in structure, which increases the cost of development and use, and is not easy to carry. brought a lot of inconvenience. A negative pressure-driven sample injection chip without an external power source is proposed, which solves this problem very well. This negative pressure-driven microfluidic chip is made of polydimethylsiloxane (PDMS). Taking advantage of the porosity of PDMS material to store gas, the chip is vacuumed in advance so that the internal pressure of the chip is lower than the external atmospheric pressure. . In this way, when the sample reagent is added to the inlet of the chip, the sample solution can be sucked into the chip due to the pressure difference between the inside and outside of the chip, without the need for an external power source. However, this kind of chip also has some shortcomings in the use process: first, the chip needs to be used immediately after each vacuuming, which brings inconvenience to remote areas and on-site real-time detection; second, the chip is in the air during use. The gas molecules will also be re-injected into the chip from around the chip, which affects the sampling effect of the chip.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for maintaining the negative pressure state of the microfluidic chip for a long time, deposit a layer of polymer film on the surface of the microfluidic chip, and utilize the denseness of the polymer film and the low permeability to gas molecules. , colorless, transparent, and non-fluorescent properties, realize the long-term storage of the negative pressure driving ability of the microfluidic chip, so that the negative pressure driving microfluidic chip can be widely used; during the chip injection, the deposited polymer The organic film can still continue to protect the periphery of the chip in a sealed state, preventing gas molecules from entering the chip from the periphery of the chip.

The invention provides a method for maintaining the negative pressure state of a microfluidic chip for a long time. First, a layer of transparent tape is pasted on the surface of the microfluidic chip, and then a layer of polymer is deposited on the surface of the microfluidic chip pasted with the transparent tape. When depositing thin films, the microfluidic chip needs to be raised at the periphery to keep most of the lower surface area of the chip, especially the central area floating. The polymer film is dense, has low permeability to gas molecules, is colorless and transparent, and has no fluorescence properties.

The material of the microfluidic chip is polydimethylsiloxane (PDMS).

The microfluidic chip obtains the negative pressure driving force by means of vacuuming.

The material of the polymer film deposited on the surface of the microfluidic chip is Parylene C.

The thickness of the microfluidic chip is adjustable, preferably 3–7 mm.

The thickness of the Parylene C film deposited on the surface of the microfluidic chip is adjustable, preferably 10–15 μm.

Polymer thin films are deposited on the surface of the microfluidic chip using vacuum vapor deposition.

The evacuation of the microfluidic chip is completed simultaneously with the deposition of the polymer film.

Before the vacuum vapor deposition of the Parylene C film, the upper surface of the microfluidic chip needs to be pasted with a layer of transparent tape.

For vacuum vapor deposition equipment, the pressure of the deposition chamber is adjustable, and the pressure remains fixed during the deposition process.

The thickness of the transparent tape should not be less than 0.05mm, that is, ≥0.05mm.

The advantages of the present invention: (1) The negative pressure power of the microfluidic chip can be maintained for a long time, and the time can be up to 30 days or longer, which is more conducive to the use of negative pressure to drive the sample injection of the microfluidic chip without an external power source. (2) The polymer film does not need to be removed when the chip is injected. The film can keep the chip around the chip in a sealed state during the chip injection process, and the injection effect is better. Evaporation; (3) The polymer film is colorless and transparent, has no fluorescence, and will not affect the result detection of the biochemical reaction in the chip.

Description of drawings

Figure 1 is a flow chart of the method of the present invention.

2 is a schematic diagram of Example 2, wherein 1 is a microfluidic chip, 2 is an adhesive tape on the upper surface, 3 is a deposited Parylene C film, 4 is an injection port, and 5 is a position where the nut is padded.

FIG. 3 is a graph of the results of Example 2. FIG.

FIG. 4 is a graph of the results of Example 3. FIG.

5 is a schematic diagram of Example 4, wherein 10 is a negative pressure driven pump module, which is composed of an adhesive tape 2 on the upper surface, a deposited Parylene C film 3, a negative pressure driven PDMS module 5, and an adhesive tape 6 on the lower surface; 7 is a microfluidic control Chip, 8 is the sample inlet, 9 is the sample outlet, and 11 is the negative pressure drive pump module with the tape on the lower surface removed.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

Embodiment 1 method implementation process

Referring to FIG. 1 , an implementation flow of a method for maintaining a negative pressure state of a microfluidic chip for a long time. The implementation object is a microfluidic chip. The specific method used is to paste a layer of transparent tape on the surface of the fabricated microfluidic chip, and then deposit a layer of polymer film on the surface of the microfluidic chip with the transparent tape.

Referring to Figure 2, the left side of the figure is a cross-sectional schematic diagram. A layer of transparent tape 2 is pasted on the top surface of the microfluidic chip 1, and a layer of Parylene C film 3 is deposited on the surface of the microfluidic chip with the transparent tape 2. The right side of the figure is The schematic diagram of the top surface of the chip, in which the injection ports 4 are arranged on both sides, and the nut 5 is arranged in the middle of the two sides as a support pad to support the microfluidic chip 1, and the standard size of the nut 5 can be M6 to M10.

The material of the microfluidic chip is a gas-permeable polymer material, preferably PDMS. The size of the chip can be adjusted as needed. The thickness of the chip can be adjusted as required, preferably 3-7mm.

Before depositing the polymer film on the microfluidic chip, a layer of transparent tape should be attached to the upper surface to prevent the upper surface of the microfluidic chip from being blurred, blocking the sample inlet and outlet, and sealing the chip caused by the polymer film directly deposited on the upper surface of the chip during the production process. Insufficient strictness and so on. The thickness of the scotch tape is not less than 0.05mm, in order to prevent the scotch tape from being deformed and unable to recover during vacuuming.

The deposited polymer film material is dense, has low permeability to gas molecules, is colorless and transparent, and has no fluorescence properties, preferably Parylene C. The thickness of the polymer film can be adjusted as required, preferably 10–15 μm.

The process of thin film deposition requires the ability to maintain a vacuum state, and a vacuum vapor deposition method is preferred.

The equipment of vacuum vapor deposition requires that the pressure of the deposition chamber can be adjusted, and the pressure remains stable during the deposition process. The pressure may be 10-40 mTorr, preferably 20 mTorr. When the microfluidic chip is placed in the vacuum vapor deposition system, the bottom surface needs to be suspended to ensure that the Parylene C film can be uniformly deposited.

Embodiment 2 The method for maintaining long-term negative pressure of self-priming and liquid-dispersing digital polymerase chain reaction (digital PCR) chip

Referring to Fig. 2, a method for maintaining the negative pressure state of the microfluidic chip for a long time is used in a self-priming and liquid-dispersing digital PCR chip. It consists of a microfluidic chip 1, an adhesive tape 2 on the upper surface of the chip, and a Parylene C film 3 deposited on the chip surface.

Microfluidic chip 1 uses PDMS as the material, and uses multi-layer soft lithography technology to use photoresist on the surface of the silicon wafer to make a mold with microchannels and microreaction chambers. First, spin a layer of 0.5mm thick PDMS on the mold. layer, the ratio of PDMS is monomer:curing agent=5:1. After curing at 85°C for 2 min, spin-coat an anti-evaporation layer and bake at 85°C for 1 min. After that, a layer of PDMS with a thickness of 5 mm is cast on the anti-evaporation layer, and the ratio of PDMS is monomer: curing agent=10:1, and it is cured by baking at 85° C. for 40 minutes. The whole PDMS was peeled off from the mold, and the injection port 4 was punched out with a 1mm diameter hole punch. The cover glass was treated with plasma and sealed with PDMS, and then placed on a hot plate at 85°C for 4 hours to complete the chip processing.

A scotch tape 2 with a thickness of 0.07 mm was pasted on the upper surface of the fabricated microfluidic chip 1, and a scraper was used to remove air bubbles between the scotch tape and the upper surface of the chip. Trim the tape around the chip when it is attached.

The Parylene C film 3 deposited on the chip surface is deposited using a vacuum vapor deposition system. Spray the release agent in the deposition chamber of the vacuum vapor deposition system and spread it evenly. Each chip is padded at position 5 with two nuts to keep the bottom surface floating so that the Parylene C film can be deposited on the bottom surface of the chip. Weigh 16.66g of Parylene C raw material, put it into a tin foil roll, and insert it into the raw material bin. 16.66g of Parylene C raw material can obtain 10μm thick film. First open the cold trap, then open the vacuum pump to evacuate the entire deposition system until the deposition chamber pressure reaches below 10mTorr, that is, <10mTorr. Turn on the heating knobs of the pyrolysis chamber and the evaporation chamber. When the temperature of the pyrolysis chamber rises to 690°C and the temperature of the evaporation chamber reaches 135°C, the deposition of the Parylene C film begins. At this time, the pressure in the deposition chamber was 20Pa, and was kept at 20Pa during the deposition process.

When all the raw materials in the raw material warehouse are evaporated and cracked, the pressure in the deposition chamber gradually decreases, and the temperature in the cracking chamber, evaporation chamber, and deposition chamber begins to drop. When the temperature of the cracking chamber drops below 350 °C, the system is closed and the deposition is to be performed. The pressure in the chamber reaches atmospheric pressure, and the chip is taken out. At this point, a uniform, dense and transparent Parylene C film with a thickness of 10 μm has been deposited on the surface of the chip.

The chips deposited with Parylene C coating were stored at room temperature for 30 days under atmospheric pressure. Use a syringe needle to pierce the injection port 4, add human 18S ribosomal RNA plasmid and the matching PCR reaction reagent, then add the oil phase liquid that is incompatible with the reaction reagent, close the injection port 4, and perform a digital PCR reaction in the chip , and the results are shown in Figure 3.

Example 3 Study on the negative pressure retention time of the microfluidic chip by the thickness of the Parylene C film

In this example, the device of Example 2 is used for sample injection, and 8.33g, 16.66g and 24.99g of raw materials are respectively used to deposit Parylene C films to obtain 5μm, 10μm and 15μm thick Parylene C films.

On the first day, the second day, ..., the thirtieth day, take microfluidic chips coated with different thicknesses of Parylene C film, use a syringe needle to pierce the injection port 4, add calcein fluorescent dye, and then The oil phase liquid was added to seal, and the injection time was counted.

The microfluidic chip fabricated using the sample injection device of Example 2, without the Parylene C film deposited, was unable to complete the complete injection of the fluorescent dye after being vacuumed and placed for 18 hours.

The microfluidic chip deposited with the Parylene C film can remain fully injected for 30 days. See Figure 4 for the results.

Embodiment 4 A kind of method of maintaining negative pressure driving pump power for a long time

A method for maintaining the power of a pump driven by negative pressure for a long time is used for sample injection analysis of common microfluidic chips. It consists of a negative pressure driven pump module 10 and a microfluidic chip 7 . The negative pressure driving pump module 10 is composed of the tape 2 on the upper surface, the deposited Parylene C film 3, the negative pressure driving PDMS module 5, and the tape 6 on the lower surface; the microfluidic chip 7 includes a sample inlet 8 and a sample outlet 9; 11 is the negative pressure drive pump module with the tape on the lower surface removed.

The negative pressure driving pump module 10 uses PDMS as the material, and is proportioned according to the ratio of monomer: curing agent=10:1. Using a clean silicon wafer as the bottom surface, a PDMS module with a height of 5 mm was poured, and it was baked at 85°C for 1 h until it was completely cured. Cut into a rectangular parallelepiped with the same width as chip 7 and a length of about 20mm. The negative pressure drive PDMS module 5 is obtained.

A transparent tape 2 with a thickness of 0.07 mm is pasted on the upper surface of the fabricated negative pressure drive PDMS module 5 , and a transparent tape 6 with a thickness of 0.07 mm is pasted on the lower surface. Use a spatula to dislodge air bubbles between the scotch tape and the top surface of the chip.

Using the vacuum vapor deposition method in Example 2, a Parylene C film 3 was deposited on the surface of the chip.

The reagent to be detected is added to the sample inlet 8, and the tape 6 on the lower surface of the negative pressure driving pump module 10 is peeled off to expose the bottom surface of the PDMS, and the negative pressure driving module 11 with the tape on the lower surface removed is obtained. Paste the side of the negative pressure drive pump module 11 with the tape on the lower surface that is exposed on the bottom surface of the PDMS on the sample outlet 9 . The negative pressure power provided by the negative pressure driving pump module can suck the reagent to be detected in the sample inlet 8 into the chip, and finally flow to the sample outlet 9 to complete the detection. See Figure 5 for the results.

Claims (4)

1. A method for maintaining a negative pressure state of a microfluidic chip for a long time is characterized in that a layer of transparent adhesive tape (2) is pasted on the upper surface of the microfluidic chip (1), then a layer of polymer film (3) is deposited on the surface of the microfluidic chip pasted with the transparent adhesive tape (2), during deposition, the microfluidic chip (1) needs to be raised on the periphery, most of the central area of the lower surface of the chip is kept suspended, and the microfluidic chip (1) obtains a negative pressure driving force in a vacuumizing mode; the polymer film (3) is deposited on the surface of the microfluidic chip (1) by using a vacuum vapor deposition method; vacuumizing the microfluidic chip (1) and depositing the polymer film (3) are completed simultaneously; before the polymer film (3) is deposited in a vacuum vapor phase manner on the microfluidic chip (1), a layer of transparent adhesive tape (2) needs to be adhered to the upper surface of the microfluidic chip, and the thickness of the transparent adhesive tape (2) is more than or equal to 0.05 mm.

2. The method for maintaining the negative pressure state of the microfluidic chip for a long time according to claim 1, wherein the material of the microfluidic chip (1) is polydimethylsiloxane with the thickness of 3-7 mm.

3. The method for maintaining the negative pressure state of the microfluidic chip for a long time as claimed in claim 1, wherein the polymer film (3) is made of poly-p-xylylene monochloride and has a surface deposition thickness of 10-15 μm.

4. The method for maintaining the negative pressure state of the microfluidic chip for a long time according to claim 1, wherein the pressure of the deposition chamber during the vacuum vapor deposition is kept constant during the deposition process.

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