A microfluidic chip for enhanced mass transfer

Abstract

This invention relates to a microfluidic chip for enhanced mass transfer, comprising a cover plate and a microchannel formed by combining the cover plate with a grooved sheet-like substrate. Each unit channel exhibits a one-to-two, two-to-three, three-to-two, and two-to-one flow channel pattern, totaling eight separations and mergers. This invention utilizes the design of multiple separation and merger structures to simultaneously achieve near-wall liquid level switching, improving the clogging issues that easily occur when using particulate catalysts, biomacromolecules, or polymer materials in microfluidic chips. Simultaneously, it ensures consistent flow channel lengths during separation and merger, reducing residence time distribution. Because mixing is primarily enhanced through chaotic flow formed by multiple separations and mergers, the microchannel size can maintain excellent mass transfer performance even at the millimeter level, significantly reducing the difficulty of fabricating microfluidic chips for enhanced mixing compared to those at the micrometer level. This invention solves the technical challenges of easy clogging and difficult equipment fabrication in microchannel reactors, achieving the goals of improving chemical production efficiency, multi-substance mixing, and mass transfer.

Description

[Technical Field]

[0001] This invention relates to the field of microfluidic chip technology, specifically to a microfluidic chip that enhances mass transfer. [Background Technology]

[0002] Mixing and reaction equipment is one of the most commonly used devices in the chemical industry. Traditional macroscopic chemical production equipment suffers from problems such as long mixing and reaction times, low raw material utilization, high energy consumption, and low yield due to low heat and mass transfer efficiency, which seriously restricts the development of the chemical industry.

[0003] In recent years, microreactors, as miniature devices manufactured using microfabrication technology, have attracted increasing attention from researchers. Compared with traditional macroscopic chemical production equipment, the main advantage of microreactors with narrow microchannels is their large specific surface area. The increased specific surface area not only shortens the heat and mass transfer distance but also enhances mixing and reaction processes, thus playing a very important role in improving the development level of the chemical industry.

[0004] However, most current microreactors, limited by high pressure drops, can only operate at relatively low Reynolds numbers, resulting in laminar flow within the microchannels. The driving force for two-phase mass transfer can only be the concentration difference or the gas-phase partial pressure difference. In passive microreactors (i.e., without external influences, where mixing and mass transfer are enhanced solely through channel structure), enhanced two-phase mass transfer can only be achieved by reducing channel size to increase the contact area between the two phases. Therefore, high mass transfer mixing efficiency can only be achieved when the characteristic dimensions of the microchannels are small. However, this approach of enhancing mass transfer by reducing channel characteristic dimensions also causes a series of problems, such as high pressure drops and susceptibility to clogging in microchannel reactors. To solve this problem and improve the efficiency and quality of chemical production, targeted design and improvement of the channel structure and operating conditions of microreactors are necessary.

[0005] The microstructure manufacturing method of this application involves simultaneously switching near-wall liquid surfaces through the design of multiple splitting and merging structures. This reduces residence time distribution and improves the clogging problem that often occurs in microreactors when using particulate catalysts. Since mixing is enhanced primarily through chaotic flow formed by multiple splitting and merging, the microchannels can be molded to micrometer-scale while still maintaining excellent mass transfer performance. This significantly reduces the difficulty of molding microfluidic chips for enhanced mixing compared to submicrometer-scale microchannels. This application solves the technical challenges of easy clogging and difficult equipment fabrication in microchannel reactors, thereby improving the efficiency and quality of chemical production.

[0006] This application discloses a microfluidic chip for enhanced mass transfer and mixing, comprising a cover plate and a grooved sheet-like substrate combined to form microchannels at the micrometer, sub-millimeter, and millimeter scales. The chip structure has at least two inlets, and the microchannels exhibit multiple unit circulation patterns. Each unit channel presents a one-to-two, two-to-three, three-to-two, and two-to-one flow channel pattern, totaling eight separations and mergers. This invention utilizes the design of multiple separation and merger structures to simultaneously achieve near-wall liquid level switching, improving the clogging issues that easily occur when using particulate catalysts, biomacromolecules, or polymer materials in microfluidic chips. Simultaneously, it ensures consistent flow channel lengths for the separation and merger channels, reducing residence time distribution. Since mixing is primarily enhanced through chaotic flow formed by multiple separations and mergers, the microchannels can maintain excellent mass transfer performance even at the millimeter scale, significantly reducing the molding difficulty compared to micrometer-sized enhanced mixing microfluidic chips. This invention solves the technical challenges of easy clogging and difficult equipment fabrication in microchannel reactors, achieving the goal of improving chemical production efficiency, mixing of multiple substances, and quality. [Summary of the Invention]

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a microfluidic chip with enhanced mass transfer. By enhancing mixing and mass transfer through various means, high two-phase mass transfer can be achieved at large feature sizes, solving the problems of high pressure drop and easy clogging in existing microchannel reactors.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A microfluidic chip for enhanced mass transfer, characterized in that it comprises a cover plate and a microchannel formed by combining the cover plate with a grooved sheet substrate.

[0010] like Figure 1 The grooved sheet-like substrate includes a hybrid structure (1), an inlet (2), and an outlet (3);

[0011] The hybrid structure (1) consists of multiple nodes and multiple channel feature sizes, with each channel feature size consisting of multiple repeating tiny hybrid units.

[0012] The micro-mixing unit consists of 12 micro-mixing unit channels, which form structures such as one-to-two, two-to-three, three-to-two, and two-to-one micro-mixing units. The two channels formed by the main channel have equal lengths and cross-sectional areas; the three channels formed by the two main channels have equal lengths and equal fluid throughputs; and the two channels formed by the three main channels have equal lengths and cross-sectional areas. The channel characteristic dimensions are composed of multiple repeating micro-mixing units, which can be end-to-end connected structures, or arbitrary channel connections such as straight or curved channels.

[0013] Micro-hybrid units, such as Figure 4The micro-mixing unit consists of flow channels I, II; III + VII, IV + VIII, V + IX, VI + X; XI, XII; all channels have equal lengths and equal cross-sectional areas.

[0014] The dimensions of microchannels are on the micrometer, sub-millimeter, and millimeter scales.

[0015] The width of the microchannel is 0.02-10mm and the depth is 0.02-10mm.

[0016] Micro-hybrid units, such as Figure 4 The cross-sectional area of ​​the main channel at the intersection of channel I and channel II is reduced by 2 times or more; the cross-sectional area of ​​the main channel at the intersection of channel III and channel I is reduced by 1.5 times or more; channel III, channel IV + channel V, channel VI; the cross-sectional areas of the channels are equal, and the cross-sectional areas of the channels of channel IV and channel V are equal.

[0017] Micro-hybrid units, such as Figure 4 A large watershed exists at the merging point of flow channel XI and flow channel XII in a single unit.

[0018] The micro-hybrid unit exhibits flow channel patterns of one-to-two, two-to-three, three-to-two, and two-to-one integration.

[0019] Micro-hybrid units, structures not limited to Figure 4 The same principle of flow channels—dividing into two, three, three into two, and two into one—also applies to structures such as... Figure 5 The structure includes flow channel I, flow channel II, flow channel III, flow channel IV, flow channel V, flow channel VI; flow channel VII, flow channel VIII, flow channel IX, channel X, flow channel XI, and flow channel XII; all flow channels have equal lengths and equal cross-sectional areas.

[0020] The micro-mixing units in the enhanced mass transfer microfluidic chip exhibit a flow channel pattern of splitting into two, splitting into three, combining into two, and combining into one, for a total of eight splits and combinations. Multiphase mixing is enhanced through fluid collision and forced dispersion.

[0021] The micro-mixing unit divides the mixed fluid into two channels, I and II, as the fluid flows through the one-to-two channel, thus separating the fluid into two parts for mass transfer.

[0022] In the micro-mixing unit, when the mixed fluid flows through the two-to-three channel, the solid dispersion microstructure passes through four channels (III, IV, V, and VI). These channels act as a breakup mechanism, increasing the interfacial area between the two phases. The fluids in the two middle channels (IV and V) merge into one fluid, and the fluids in the two outer channels (III and VI) form a three-channel fluid configuration. This mixes the mass transfer portions that flowed through the two separate channels (I and II) of the two-to-one channel into a single unit, enhancing mass transfer.

[0023] In the micro-mixing unit, when the mixed fluid flows through the three-in-one channel, the intermediate fluid is forced to separate and pass through channels VIII and IX, and merges with the fluid in channels VII and X respectively to form the fluid in channels XI and XII. The separated parts that enhance mass transfer are then integrated for mixing and mass transfer. Channels XI and XII have a large surface area to provide for the reaction.

[0024] In the micro-mixing unit, when the mixed fluid flows through the two-in-one channel, the fluids in channels XI and XII merge into a single fluid and flow out of the micro-mixing unit.

[0025] Compared with the prior art, the positive effects of the present invention are:

[0026] (1) The microchannel reactor channel structure proposed in this invention has a characteristic size of 0.02-10mm in width and 0.02-10mm in depth compared with the traditional microchannel. The characteristic size of the microchannel can be larger, and under the same conditions, the pressure drop is lower and it is not easy to be blocked.

[0027] (2) The micro-mixing unit mainly presents a one-to-two and two-to-three flow channel mode in the flow channel section, with a total of 3 splits and 1 combination. Through the collision of fluids, forced dispersion is achieved, and some fluids are premixed. Finally, the fluids are diverted into the three channels.

[0028] (3) The micro-mixing unit mainly exhibits a three-in-two and two-in-one flow channel pattern in the merging channel section, with a total of one separation and three merging. Through near-wall liquid surface exchange, the premixed part in the middle is introduced into the two side channels to enhance the comprehensive mass transfer and reaction within the flow channel. Finally, the fluid is merged into one channel, where multiphase mixing and reaction are enhanced, improving the mass transfer effect. At the same time, the lengths of each separation and merging path are equal, and the flux is the same, ensuring the consistency of the residence time in the microreactor. [Attached Image Description]

[0029] Figure 1 Overall diagram of the microchannel reactor;

[0030] Figure 2 Detailed diagram of a series mixing unit in a microchannel reactor;

[0031] Figure 3 : Flow diagram of a microchannel reactor in series;

[0032] Figure 4 : Dimensional diagram of a microchannel reactor unit;

[0033] Figure 5 Simplified diagram of a microchannel reactor unit;

[0034] Figure 6 Comparison chart of gas-liquid mass transfer effects;

[0035] Figure 7Comparison of mass transfer effects in pressure drop test.

Detailed Implementation Methods

[0036] The following provides a specific embodiment of a microfluidic chip for enhanced mass transfer according to the present invention.

[0037] Example 1:

[0038] In a typical embodiment of this invention application, such as Figure 1 As shown, a microfluidic chip structure for enhanced mixing is presented, with a glass substrate and a fractal structure processed using a femtosecond laser. The main channel has a characteristic dimensions of 1 mm width and 1.1 mm depth (for easy comparison with a Corning reactor). Channels 1 and 2 have a minimum width of 0.7 mm and a depth of 0.8 mm. Channels 3 and 6 have an average width of 0.58 mm and a depth of 0.6 mm. The mixing unit has 5 cycles, and the main channel inlet is a T-shaped channel.

[0039] Comparative Example 1:

[0040] The gas-liquid mass transfer performance of the microchannel reactor in Example 1 was compared with that of a Corning heart-shaped mixing unit with the same liquid holdup. The results are as follows: Figure 6 As shown. Gas-liquid mass transfer tests were conducted with both channel structures set at a gas flow rate of 300 mL / min and a liquid flow rate of 50 mL / min. The smaller the size and the greater the number of bubbles generated in the channel structure, the better the gas-liquid mass transfer performance of that structure.

[0041] Comparative Example 2:

[0042] The microchannel reactor in Example 1 was compared with a Corning heart-shaped mixing unit with the same liquid holdup using a pressure drop test to assess its mass transfer performance. The gas flow rate was set to 300 mL / min, and the solution flow rates were set to 10 mL / min, 20 mL / min, 40 mL / min, 60 mL / min, and 80 mL / min, respectively. The pressure drop was measured and calculated using pressure sensors at the inlet and outlet. The results are as follows: Figure 7 As shown, at the same liquid holdup, a smaller pressure drop through the channel structure indicates that the channel structure is less prone to blockage.

[0043] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the concept of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A microfluidic chip, characterized in that, It includes a cover plate, and microchannels formed by the combination of the cover plate and a grooved sheet-like substrate; The grooved sheet-like matrix contains a hybrid structure; The hybrid structure contains multiple nodes and multiple channels, with each channel consisting of multiple repeating tiny hybrid units; The micro-mixing unit consists of 12 flow channels, which form a structure that can be divided into two, three, three into two, and two into one. When the mixed fluid flows through the one-to-two channel, the two channels that the main channel is divided into have equal lengths and equal cross-sectional areas. The fluid is divided into two channels, I and II, and the fluid is divided into two parts for mass transfer. When the mixed fluid flows through the two-to-three channels, the solid dispersed microstructure passes through four channels: III, IV, V, and VI. The fluids in the two middle channels, IV and V, merge into one fluid. The whole fluid and the fluids in the two outer channels, III and VI, form a three-channel fluid structure. The two channels, III and VII, IV and VIII, V and IX, and VI and X, have equal lengths and equal cross-sectional areas. When the mixed fluid flows through the three-in-one channel, the intermediate fluid is forced to separate and pass through channels VIII and IX, and merges with the fluid in channels VII and X respectively to form the fluid in channels XI and XII. The combined channels XI and XII have equal lengths and equal cross-sectional areas. When the mixed fluid flows through the two-in-one channel, the fluids in channels XI and XII merge into a single fluid and flow out of the tiny mixing unit.

2. A microfluidic chip as described in claim 1, characterized in that, The dimensions of microchannels are on the micrometer, sub-millimeter, and millimeter scales.

3. A microfluidic chip as described in claim 1, characterized in that, The width of the microchannel is 0.02-10mm and the depth is 0.02-10mm.

4. A microfluidic chip as described in claim 1, characterized in that, The micro-mixing unit has flow channel I and flow channel II with a cross-sectional area reduced by 2 times or more compared to the main flow channel; flow channel III has a cross-sectional area reduced by 1.5 times or more compared to flow channel I.

5. A microfluidic chip as described in claim 4, characterized in that, The micro-mixing unit has a large flow domain at the junction of flow channel XI and flow channel XII in a single unit.

6. A microfluidic chip as described in claim 1, characterized in that, The micro-mixing unit consists of flow channels I, II, III, IV, V, and VI; flow channels VII, VIII, IX, X, XI, and XII; all flow channels have equal lengths and equal cross-sectional areas.

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