A real coal chip suitable for microfluidic experiments

Abstract

The present application relates to a kind of real coal chip suitable for microfluidic experiment, it includes coal quality matrix, first resin encapsulation layer and second resin encapsulation layer, first resin is coated in the outer periphery and bottom surface of coal quality matrix, second resin encapsulation layer covers the top surface of coal quality matrix and seals microfluidic channel structure in chip interior, first resin encapsulation layer and second resin encapsulation layer are transparent;Microfluidic channel structure formed by laser etching is embedded in the inside of coal quality matrix, and microfluidic channel structure includes pore network, injection port communicated with pore network and flow outlet communicated with pore network, the injection port and flow outlet extend to chip edge;The surface of the microfluidic channel structure retains the original physical and chemical properties of coal quality, can truly reflect the interaction process of coal and gas.The present application solves the problem that existing microfluidic chip uses glass or silicon-based material, cannot truly reflect the physical and chemical action of coal and gas.

Description

Technical Field

[0001] This invention relates to the fields of microfluidics and coal gas technology, specifically to a real coal chip suitable for microfluidic experiments. Background Technology

[0002] Microfluidic chips, also known as laboratory-on-a-chip, are technological platforms that enable precise manipulation of fluids in a micro- and nanoscale space. They have the ability to miniaturize the basic functions of biological and chemical laboratories onto chips measuring just a few square centimeters. Currently, microfluidic chips are mainly fabricated using photolithography on materials such as glass, silicon wafers, or polymers, and are widely used in fields such as biomedicine and chemical analysis.

[0003] In mining engineering fields such as coal and gas outburst mechanism research and coalbed methane extraction, understanding the adsorption, desorption, and transport mechanisms of methane gas in coal pores is crucial. However, existing microfluidic chips mainly use glass or silicon-based materials, which have significantly different physicochemical properties from coal, completely ignoring the actual interfacial interactions and adsorption characteristics between coal and gases such as methane. Because coal is a porous medium with extremely complex composition and structure, its surface contains abundant functional groups, exhibiting specific adsorption capabilities for gases that glass or silicon-based chips cannot simulate. Therefore, microfluidic chips made with traditional materials cannot accurately characterize the actual interaction process between coal and methane under microfluidic conditions, leading to discrepancies between experimental data and actual conditions.

[0004] Although researchers have attempted to apply microfluidic technology to the coal industry, such as microfluidic devices for observing coal microbial gasification or microfluidic devices for separating fly ash particles, these solutions have not solved the problem of using real coal matrix as the main material of the chip. Developing a microfluidic chip based on real coal material that retains the original surface properties of coal while forming a regular and controllable microchannel structure is of great significance for revealing the gas migration mechanism and guiding safe production in coal mines. Summary of the Invention: The purpose of this invention is to provide a real coal chip suitable for microfluidic experiments. This real coal chip solves the problem that existing microfluidic chips, which use glass or silicon-based materials, cannot truly reflect the physicochemical interactions between coal and gases such as methane.

[0005] The technical solution adopted by this invention to solve its technical problem is as follows: This real coal chip suitable for microfluidic experiments includes a coal substrate, a first resin encapsulation layer, and a second resin encapsulation layer. The first resin encapsulation layer is groove-shaped and covers the outer periphery and bottom surface of the coal substrate. The second resin encapsulation layer covers the top surface of the coal substrate and seals the microfluidic channel structure inside the chip. Both the first and second resin encapsulation layers are transparent. The coal substrate contains a microfluidic channel structure formed by laser etching. The microfluidic channel structure includes a pore network, an injection port communicating with the pore network, and an outlet communicating with the pore network. The injection port and outlet extend to the edge of the chip. The surface of the microfluidic channel structure retains the original physicochemical properties of the coal and can truly reflect the interaction process between coal and gas.

[0006] The above-mentioned method for preparing real coal chips suitable for microfluidic experiments includes the following steps: a) Coal sample pretreatment: The raw coal is cut and processed into cylindrical thin slices to obtain the coal matrix; b) First encapsulation: The cylindrical sheet is encapsulated by casting resin glue. Casting is stopped when the resin glue reaches the upper surface of the coal sample to obtain a resin-coal composite. The resin glue is then allowed to solidify. c) Surface polishing: Polishing and grinding the solidified resin-coal composite to make the upper surface of the coal matrix smooth. d) Microchannel etching: Using laser etching technology, a microfluidic channel structure is formed on a flat surface of a coal matrix according to a preset pore network model. The channel structure includes a pore network, an inlet, and an outlet. e) Temporary sealing: High-transparency ultra-thin double-sided tape is used to cover and seal the etched pore network, injection port, and outlet. f) Second encapsulation: Resin glue is used again for casting, with the casting height exceeding the top surface of the coal matrix by 2-3 mm. After the resin glue has completely solidified, a real coal chip suitable for microfluidic technology is obtained.

[0007] In the above scheme, the diameter of the cylindrical sheet is 20-30mm and the height is 4-6mm; this size is compatible with the standard microfluidic experimental platform, while ensuring that the coal sample has sufficient mechanical strength and representativeness.

[0008] In the above scheme, the resin adhesive is a transparent epoxy resin or a UV-curable adhesive. The transparent material facilitates subsequent optical observation and testing.

[0009] In step d) of the above scheme, the depth and width of laser etching are controlled according to the preset pore network model, and the etching residue is removed by a high-pressure air gun after etching is completed.

[0010] In step e) of the above scheme, the thickness of the high-transparency ultra-thin double-sided adhesive is 0.05-0.2mm, and its light transmittance is greater than 90%. The function of this sealing layer is to prevent the resin from being poured into the etched microchannels and causing blockage during subsequent resin pouring, while the high light transmittance facilitates observation and alignment.

[0011] In step f) of the above scheme, the height of the second pour exceeds the top surface of the coal matrix by 2.5 mm.

[0012] In the above scheme, the diameter of the cylindrical sheet is 25mm and the height is 5mm.

[0013] Beneficial effects: 1. This invention is the first to propose using real coal material as the main matrix of microfluidic chip, which retains the functional group structure and adsorption characteristics of coal surface, and can truly reflect the physicochemical reaction process between coal and gases such as methane, overcoming the material limitations of traditional glass or silicon-based chips.

[0014] 2. This invention employs a two-stage resin encapsulation process, which not only ensures the mechanical strength and sealing of the chip, but also prevents resin from entering the microchannel through an intermediate temporary sealing layer, ensuring the integrity and unobstructed flow of the microchannel structure.

[0015] 3. This invention uses laser etching technology to process a preset pore network model on the coal surface, thereby achieving accurate simulation and controllable design of the coal pore structure.

[0016] 4. The transparent packaging of the chip in this invention facilitates real-time observation and recording using equipment such as microscopes and CCDs, providing an effective platform for studying the microscopic mechanism of coal-gas interaction.

[0017] 5. This invention uses real coal material for the chip body, retains the physicochemical properties of coal and gas, and forms a controllable microchannel structure through laser etching, thereby realizing the true characterization of coal-gas interaction.

[0018] 6. The real coal chip and its preparation method provided by this invention have industrial applicability and can be promoted and applied in fields such as mining engineering, coalbed methane development, and gas disaster prevention and control. It can be used to simulate and study the adsorption, desorption, and transport laws of gas in coal pores under different pressure and temperature conditions. It can also be used to evaluate the influence of different treatment agents on the gas adsorption performance of coal. It has important scientific research value and engineering application prospects. Attached image description: Figure 1 This is a cross-sectional view of the structure of the present invention.

[0019] Figure 2This is a schematic diagram of the actual coal chip manufacturing process of the present invention. In the diagram, a) is coal sample cutting, b) is first packaging, c) is surface polishing, d) is laser etching, e) is temporary sealing, and f) is second packaging and drilling. The injection hole is the injection channel and the extraction hole is the extraction channel.

[0020] In the diagram: 1. Coal sheet, 2. First resin encapsulation layer, 3. Second resin encapsulation layer, 4. Injection channel, 5. Extraction channel, 6. Transparent sealing layer. Detailed implementation method: The present invention will be further described below with reference to the accompanying drawings: Combination Figure 1 , Figure 2 The real coal chip suitable for microfluidic experiments comprises a coal substrate (i.e., coal sheet 1), a first resin encapsulation layer 2, and a second resin encapsulation layer 3. The first resin encapsulation layer 2 is groove-shaped and covers the outer periphery and bottom surface of the coal substrate. The second resin encapsulation layer 3 covers the top surface of the coal substrate and seals the microfluidic channel structure inside the chip. Both the first resin encapsulation layer 2 and the second resin encapsulation layer 3 are transparent resin adhesives, which are transparent epoxy resins or UV-curable adhesives. The coal substrate has a diameter of 20-30 mm and a height of 4-6 mm. The coal substrate contains a microfluidic channel structure formed by laser etching. The microfluidic channel structure includes a pore network, an injection port communicating with the pore network, and an outlet communicating with the pore network. The injection port and outlet extend to the edge of the chip. The surface of the microfluidic channel structure retains the original physicochemical properties of the coal, which can realistically reflect the interaction process between coal and gas. This invention is the first to realize the construction of a microfluidic chip using real coal material, which preserves the original surface characteristics of coal and can truly reflect the interaction between coal and gas, providing an effective platform for studying the microscopic migration mechanism of gas.

[0021] See Figure 2 The above-mentioned method for preparing real coal chips suitable for microfluidic experiments includes the following steps: a) Coal sample pretreatment: The raw coal is cut and processed into cylindrical thin slices with a diameter of 20-30 mm and a height of 4-6 mm to obtain a coal matrix, which is adapted to a standard microfluidic experimental platform, while ensuring that the coal sample has sufficient mechanical strength and representativeness.

[0022] b) First encapsulation: The cylindrical sheet is encapsulated by casting resin glue. Casting is stopped when the resin glue reaches the upper surface of the coal sample to obtain a resin-coal composite. The resin glue is then allowed to solidify. The resin glue is a transparent epoxy resin or a UV-curable glue. Transparent materials facilitate subsequent optical observation and testing.

[0023] c) Surface polishing: Polishing and grinding the solidified resin-coal composite to make the surface of the coal matrix smooth.

[0024] d) Microchannel etching: Using laser etching technology, a microfluidic channel structure is formed on the flat surface of the coal matrix according to a preset pore network model. The channel structure includes a pore network, an inlet, and an outlet. The depth and width of the laser etching are controlled according to the preset pore network model. After etching, the etching residue is removed by a high-pressure air gun.

[0025] e) Temporary sealing: High-transparency ultra-thin double-sided tape is used to cover and seal the etched pore network, injection port and outlet. The thickness of the high-transparency ultra-thin double-sided tape (i.e. transparent sealing layer 6) is 0.05-0.2mm, and its light transmittance is greater than 90%. This prevents the resin from being poured into the etched microchannels during subsequent resin pouring and causing blockage. At the same time, it is also easy to observe and align.

[0026] f) Second encapsulation: Resin glue is used again for casting, with the casting height exceeding the top surface of the coal matrix by 2-3 mm. After the resin glue has completely solidified, a real coal chip suitable for microfluidic technology is obtained.

[0027] Example 1 The specific steps of this method for preparing a real coal chip suitable for microfluidic experiments are as follows: (1) Coal sample collection and pretreatment: Fresh, blocky coal samples from the target coal seam were selected and cored using a coring drill to extract cylinders with a diameter of 25 mm. These cylinders were then cut into thin cylindrical slices with a height of 5 mm using a cutting machine. The surfaces of the coal slices were cleaned with a rubber bulb to remove any loose coal dust.

[0028] (2) First encapsulation (bottom encapsulation): The dried coal cylindrical sheet was placed in a polytetrafluoroethylene mold with dimensions of 60 mm in length, 40 mm in width, and 10 mm in height. Transparent epoxy resin was used for casting, and casting was stopped immediately when the liquid level slowly rose to the top surface of the coal sample. The mold was then placed in a vacuum drying oven and vacuumed for 10 minutes to remove air bubbles. It was then allowed to stand at room temperature for 12 hours until the resin had completely solidified.

[0029] (3) Surface polishing: The solidified resin-coal composite was removed from the mold and polished using a metallographic polishing machine. Grinding was performed sequentially using 400-grit, 800-grit, 1500-grit, and 2000-grit sandpaper, followed by polishing with 0.5μm alumina polishing powder to achieve a mirror-like surface finish for subsequent laser etching. After polishing, ultrasonic cleaning for 5 minutes was performed to remove any residual polishing particles.

[0030] (4) Laser etching of microchannels: A femtosecond laser etching system was used to perform etching according to the designed pore network model. The pore network model was designed with reference to the pore structure characteristics of typical coal samples, with channel widths and depths ranging from 20 to 1000 μm. The etched structure includes a central pore network region and injection and outflow channels (i.e., injection channel 4 and extraction channel 5) connecting to both ends of the pore network. After etching, high-pressure nitrogen was used to purge the etching residue.

[0031] (5) Temporary sealing: High-transparency ultra-thin double-sided adhesive with a thickness of 0.1mm and a light transmittance of 95% is used. The adhesive is cut to the appropriate size according to the chip dimensions and carefully applied to the etched coal sample surface, completely covering the pore network, injection port, and outlet area. During application, care is taken to remove air bubbles to ensure a tight seal.

[0032] (6) Secondary encapsulation (top encapsulation): The coal sample with the temporary sealing film was placed back into the mold, and epoxy resin of the same proportion was prepared again for casting, with the casting height exceeding the top surface of the coal sample by 2.5 mm. Vacuum degassing was then performed again, and the mixture was allowed to stand at room temperature for 24 hours until the resin was completely solidified.

[0033] (7) Post-processing and inspection: The fully solidified chip is removed from the mold, its edges are trimmed, and it is inspected for air bubbles and cracks. Holes are then drilled at the corresponding injection and outlet locations to create a channel below, and a standard microfluidic interface is installed. The integrity of the channel structure is observed under a microscope, and an airtightness test is performed to confirm the chip's qualification.

[0034] The performance of the real coal chip prepared in Example 1 was tested and compared with that of a traditional glass microfluidic chip.

[0035] Dyed methane gas (containing tracer) was injected into the injection port of a real coal chip, and the gas transport process in the pore network was observed using a high-speed microscope. The results showed that the gas transport in the coal matrix channels exhibited a significant adsorption-desorption hysteresis effect, with some gas remaining on the coal surface, which is consistent with the gas transport characteristics of actual coal seams.

[0036] Comparative Example 1 This comparative example uses a conventional glass microfluidic chip fabrication method, namely, etching a similarly designed porous network structure on a glass substrate using photolithography, and then bonding and encapsulating it with a cover plate. Methane adsorption and transport experiments were conducted under the same experimental conditions as in Example 2. The results showed that no methane adsorption was detected on the glass chip surface, and the gas transport exhibited simple Poisson's flow, which is significantly different from the gas behavior of real coal seams.

[0037] Comparative Example 2 This comparative example attempts to prepare coal chips using a one-step encapsulation method, i.e., directly etching channels on the surface of the coal sample and immediately encapsulating them with resin, omitting the temporary sealing step. The results show that resin seeps into the etched channels during encapsulation, causing complete blockage and rendering the chips unusable for microfluidic experiments.

[0038] In summary, the real coal chip and its preparation method provided by this invention, through ingenious two-stage encapsulation process and temporary sealing design, successfully realize the construction of a microfluidic chip based on real coal material, preserving the intrinsic properties of coal, and providing an effective microscopic experimental platform for studying the interaction between coal and gas.

Claims

1. A real coal chip suitable for microfluidic experiments, characterized in that: This real coal chip, suitable for microfluidic experiments, includes a coal substrate, a first resin encapsulation layer, and a second resin encapsulation layer. The first resin encapsulation layer is groove-shaped and covers the outer periphery and bottom surface of the coal substrate. The second resin encapsulation layer covers the top surface of the coal substrate and seals the microfluidic channel structure inside the chip. Both the first and second resin encapsulation layers are transparent. The coal substrate contains a microfluidic channel structure formed by laser etching. The microfluidic channel structure includes a pore network, an injection port communicating with the pore network, and an outlet communicating with the pore network. The injection port and outlet extend to the edge of the chip. The surface of the microfluidic channel structure retains the original physicochemical properties of coal, which can truly reflect the interaction process between coal and gas.

2. The real coal chip suitable for microfluidic experiments as described in claim 1, characterized in that: The method for preparing a real coal chip suitable for microfluidic experiments includes the following steps: a) Coal sample pretreatment: The raw coal is cut and processed into cylindrical thin slices to obtain the coal matrix; b) First encapsulation: The cylindrical sheet is encapsulated by casting resin glue. Casting is stopped when the resin glue reaches the upper surface of the coal sample to obtain a resin-coal composite. The resin glue is then allowed to solidify. c) Surface polishing: Polishing and grinding the solidified resin-coal composite to make the upper surface of the coal matrix smooth. d) Microchannel etching: Using laser etching technology, a microfluidic channel structure is formed on a flat surface of a coal matrix according to a preset pore network model. The channel structure includes a pore network, an inlet, and an outlet. e) Temporary sealing: High-transparency ultra-thin double-sided tape is used to cover and seal the etched pore network, injection port, and outlet. f) Second encapsulation: Resin glue is used again for casting, with the casting height exceeding the top surface of the coal matrix by 2-3 mm. After the resin glue has completely solidified, a real coal chip suitable for microfluidic technology is obtained.

3. The real coal chip suitable for microfluidic experiments according to claim 2, characterized in that: The cylindrical sheet has a diameter of 20-30 mm and a height of 4-6 mm.

4. The real coal chip suitable for microfluidic experiments according to claim 3, characterized in that: The resin adhesive is a transparent epoxy resin or a UV-curable adhesive.

5. The real coal chip suitable for microfluidic experiments according to claim 4, characterized in that: In step d), the depth and width of laser etching are controlled according to a preset pore network model, and after etching is completed, a high-pressure air gun is used to remove etching residue.

6. The real coal chip suitable for microfluidic experiments according to claim 5, characterized in that: In step e), the thickness of the high-transparency ultra-thin double-sided adhesive is 0.05-0.2mm, and its light transmittance is greater than 90%.

7. The real coal chip suitable for microfluidic experiments according to claim 6, characterized in that: In step f), the height of the second pour exceeds the top surface of the coal matrix by 2.5 mm.

8. The real coal chip suitable for microfluidic experiments according to claim 7, characterized in that: The cylindrical sheet has a diameter of 25 mm and a height of 5 mm.

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