Microfluidic device and method for observing generation and migration of microbubbles

Abstract

The invention discloses a microfluidic device and method for observing generation and migration of microbubbles. According to the chip related to the microfluidic device, generation and migration of microbubbles can be carried out in a plane, gas-phase fluid is sheared by liquid-phase fluid in a cross-shaped channel to generate continuous microbubbles with controllable and uniform sizes, and the fluid is introduced into a porous medium model after passing through a slow flow design in the chip; therefore, the migration and plugging effects of the microbubbles in different media can be observed. The integrated design can greatly reduce the interference of the external environment on the microbubbles, and prevents the microbubbles from coalescence and floating in the storage process. Compared with a common glass etching chip, the polydimethylsiloxane (PDMS) chip is lower in cost and shorter in construction period, and can be customized and replaced according to different porous media.

Description

Technical Field

[0001] This invention relates to the field of microfluidics, and more specifically to a microfluidic device and method for observing the generation and movement of microbubbles. Background Technology

[0002] Gas-liquid two-phase systems are widely used in chemical, energy, pharmaceutical, and environmental fields. The contact area and time between the gas and liquid phases are crucial parameters determining the efficiency of the reaction process. In traditional gas-liquid reactions (such as stirring and bubbling methods), the generated bubbles are generally large, resulting in a small mass transfer area and low mass transfer efficiency between the gas and liquid phases. Compared to conventional millimeter or micrometer-sized bubbles, microbubbles have a larger specific surface area, faster gas dissolution rate, and higher stability, thus attracting widespread attention to microbubble technology.

[0003] Currently, the main methods for generating microbubbles include high-speed stirring, microfluidics, jetting, and electrolysis. Among these, microfluidics can regulate the flow process of two-phase flow at the microscale, offering precision and controllability. Microbubbles prepared using microfluidics are of controllable size and uniformity. In traditional processes, to study the transport of microbubbles within confined spaces, it is necessary to generate and store the microbubbles in a distributed manner, and then introduce them into a porous dielectric chip from the injection end. During storage, not only is some experimental material wasted, but the experimental cycle is also prolonged. For some special microbubbles, improper handling or slightly longer storage time can cause microbubbles to float and coalesce, which significantly affects the experimental results.

[0004] Regarding the design and fabrication of integrated microbubble-porous media chips, CN115876651A, CN118465186A, and Kum Ma (Soft Matter 2012, 8: 10669-10675) have cleverly integrated bubble-generating devices and porous media onto a single microchip. However, they did not consider the impact of high-velocity fluid on the displacement process during microbubble generation from an experimental perspective. In traditional micro-displacement experiments, the injection fluid velocity is generally 1–20 μL / min. To generate microbubbles, a gas jet is required, meaning the gas velocity needs to be above 50 μL / min. Furthermore, the liquid utilizes fluid inertia and surface tension to shear the gas jet to form microbubbles smaller than 100 μm, requiring a liquid velocity of over 200 μL / min. Considering that under the impact of such high-velocity fluid, the fluid would rapidly form dominant channels within the porous media chip, and in some cases, even damage the chip structure. Summary of the Invention

[0005] In summary, an integrated microfluidic device for microbubble flooding systems in low-permeability reservoirs is a pressing issue. Such a device should integrate microbubble generation, transport, and sealing, generating continuous and uniformly sized microbubbles while employing ingenious channel design to slow the flow rate of the microbubble fluid, allowing the fluid to enter the porous medium at a suitable velocity. This invention demonstrates advantages and innovation in its approach and methodology, eliminating the influence of external factors and shortening the overall experimental cycle.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] This invention discloses a microfluidic device and method for observing the generation and transport of microbubbles, the specific steps of which include:

[0008] (I) The composition of a microfluidic device includes the following steps:

[0009] 1) Microfluidic devices and methods for observing the generation and movement of microbubbles, including PDMS chips, microscopic systems, and injection systems. Specifically, the microscopic system consists of a microscope, a camera, and a computer.

[0010] 2) Specifically: The injection system consists of an external phase flow injection system and an internal phase flow injection system; the external phase flow injection system consists of a syringe pump and a fluid injector; the internal phase flow injection system consists of a compressed gas cylinder, a pressure reducing valve, a gas flow controller, and a pipe reducer.

[0011] (ii) Connecting the microfluidic device, including the following steps:

[0012] 1) Firstly, the fluid injector is placed in the injection pump, and the fluid injector is connected to the external phase injection end through a polytetrafluoroethylene (PTFE) line;

[0013] 2) Furthermore, a pressure reducing valve is installed at the outlet end of the compressed gas cylinder. The pressure reducing valve and the gas flow controller are connected by a steel pipe. The steel pipe is converted into a polytetrafluoroethylene pipeline through a pipe reducer and connected to the inward injection end.

[0014] (III) The composition of the PDMS chip, characterized in that:

[0015] The PDMS chip includes an external phase injection end, an internal phase injection end, an external phase flow channel, an internal phase flow channel, a cross-shear channel, an "S"-shaped slow flow channel, a waste liquid channel, a waste liquid discharge end, an injection medium channel, a sieving zone, a sieving module, a diversion channel, a pressure reducing channel, a dominant channel, a high-permeability zone, a low-permeability zone, and an oil phase inlet / outlet end.

[0016] (iv) The design of the PDMS chip is characterized by the following steps:

[0017] 1) Firstly, a microbubble generation device is provided on the left side of the PDMS chip, including an external phase injection end, an internal phase injection end, an external phase flow channel, an internal phase flow channel, and a cross-cutting channel;

[0018] 2) Furthermore, an "S"-shaped slow-flow channel is set up, with the width of the slow-flow channel gradually increasing from 200μm to 700μm. The corresponding channel cross-sectional area increases, which can effectively slow down the fluid flow rate.

[0019] 3) Furthermore, the end of the “S”-shaped slow-flow channel is provided with a waste liquid channel, a waste liquid discharge end and an injection medium channel, wherein the width of the injection medium channel gradually increases from 700μm to 1000μm;

[0020] 4) Furthermore, screening zones are set up according to the plan, and screening modules are evenly distributed within the screening zones;

[0021] 5) Furthermore, according to the plan, there are diversion channels, pressure reducing channels and porous media modules, among which the porous media modules are equipped with dominant channels, high permeability zones, low permeability zones and oil phase inlet and outlet ends;

[0022] (v) The connection of the PDMS chip is characterized by the following steps:

[0023] 1) Firstly, in the microbubble generating device, the external phase injection end is connected to the external phase flow channel, and the internal injection end is connected to the internal phase flow channel, wherein an "S"-shaped flow stabilizing channel is provided in both the external phase flow channel and the internal phase flow channel.

[0024] 2) Furthermore, the outer phase flow channel and the inner phase flow channel are connected to the "S"-shaped slow flow channel in a cross-shaped manner;

[0025] 3) Furthermore, the waste liquid channel, waste liquid discharge end, and injection medium channel are connected to the end of the “S”-shaped slow flow channel;

[0026] 4) Furthermore, the end of the injection medium channel is connected to the screening section, the end of the screening section is connected to the diversion channel, a pressure reducing channel is connected at the edge of the diversion channel, and the porous medium chip is introduced into the end of the diversion channel.

[0027] 5) Furthermore, the porous medium is divided into a dominant channel, a high-permeability zone, and a low-permeability zone, which are interconnected. The end of the porous medium chip is connected to the oil phase inlet and outlet.

[0028] The beneficial effects of this invention are as follows:

[0029] This invention proposes a microfluidic device and method for observing the generation and migration of microbubbles. The main body of the device is a PDMS microfluidic chip. Based on microfluidic technology, the particle size of the microbubbles can be controlled, and the microbubbles are continuous and uniform in size. After the fluid passes through a designed slowing channel, the flow rate can be reduced, and then when the fluid enters the porous medium channel, its migration and blocking effect can be effectively observed. This PDMS chip integrates the evaluation of microbubble generation and migration on a single plane, reducing the consumption of experimental samples during intermediate storage and shortening the experimental cycle. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall structure of the device according to an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the PDMS chip composition according to an embodiment of the present invention;

[0032] The components include: PDMS chip 1, injection pump 2, fluid injector 3, compressed gas cylinder 4, pressure reducing valve 5, gas flow controller 6, pipe reducer 7, and microsystem 8; for PDMS chip 1, the components include: external phase injection end 1-1, internal injection end 1-2, external phase flow channel 1-3, internal phase flow channel 1-4, cross shear channel 1-5, "S" type slow flow channel 1-6, waste liquid channel 1-7, waste liquid discharge end 1-8, injection medium channel 1-9, sieving zone 1-10, sieving module 1-11, diversion channel 1-12, pressure reducing channel 1-13, dominant channel 1-14, high permeability zone 1-15, low permeability zone 1-16, and oil phase inlet / outlet end 1-17. Detailed Implementation

[0033] The invention will be further described below with reference to the accompanying drawings:

[0034] Example

[0035] An experimental method for observing the generation and transport of microbubbles using a microfluidic device includes the following steps:

[0036] 1) Combining Figure 1 Place the PDMS chip 1 under the microscope 8, turn on the microscope 8, and focus until the internal channels of the chip can be clearly observed; first, saturate the porous media model 1-14, 1-15, and 1-16 with oil through the fluid inlet / outlet 1-17. The saturating oil can be simulated oil or crude oil; after saturation, the excess oil will enter the waste liquid channel 1-7 through the injection medium channel 1-9 and exit from the waste liquid discharge end 1-8;

[0037] 2) Open the switch of compressed gas cylinder 4, and use the pressure reducing valve 5 and gas flow controller 6 to adjust the gas pressure, thereby controlling the gas flow rate inside PDMS chip 1; place the fluid injector 3 on the injection pump 2 and lock it in place, turn on the injection pump 2 and set the injection parameters, and observe the shearing state of the gas phase and liquid phase at the cross-shaped shearing channel 1-5 through the microscope 8, and adjust the liquid phase flow rate in real time. The gas phase enters the inner phase flow channel 1-4 through the inner phase injection end 1-2, and the liquid phase enters the outer phase flow channel 1-3 through the outer phase injection end 1-1. The inner phase fluid and the outer phase fluid meet at the cross intersection to form an interface. Under the action of interfacial tension and inertia, the outer phase fluid cuts off the inner phase fluid to generate microbubbles of uniform size, and the particle size of the microbubbles can be controlled by adjusting the flow rates of the inner and outer phase fluids.

[0038] 3) After the liquid phase shears the gas phase to generate microbubbles, the fluid is decelerated through the "S"-shaped slow-flow channel 1-6. If microbubbles of the target particle size are not obtained, the fluid reaches the waste liquid discharge end 1-8 through the waste liquid channel 1-7 and is discharged. To prevent the fluid from diffusing into the injection medium channel 1-9, a certain tail pressure needs to be applied to the oil phase inlet / outlet end 1-17. After obtaining microbubbles of the target particle size, the waste liquid discharge end 1-8 is closed, and the fluid enters the screening section 1-10 through the injection medium channel 1-9 after further deceleration. The screening module 1-11 can not only separate the fluid and screen the bubbles, but also... The fluid velocity is further reduced by increasing flow resistance. The sieved fluid enters the diversion channel 1-12 and is then introduced into the porous media model. During this process, the tail pressure needs to be appropriately reduced so that the fluid first reaches the oil phase inlet / outlet 1-17 through the dominant channel 1-14. Then, the fluid is gradually guided into the high-permeability zone 1-15 and the low-permeability zone 1-16 using the diffusion mechanism of microbubbles, displacing the saturated oil therein. After the fluid has cleared the dominant channel 1-14, the pressure-reducing channel 1-13 needs to be opened, and the fluid flow rate in the pressure-reducing channel 1-13 needs to be adjusted in real time to achieve a certain pressure reduction and flow control effect. Under these conditions, the migration and blocking effect of microbubbles in the high-permeability zone 1-15 and the low-permeability zone 1-16 can be clearly observed.

Claims

1. A microfluidic device for observing the generation and transport of microbubbles, characterized in that, Microfluidic devices include a microscope system, an injection system, and a PDMS chip; The microscopic system consists of a microscope, a camera, and a computer; the injection system consists of an external phase flow injection system and an internal phase flow injection system; the external phase flow injection system consists of a syringe pump and a fluid injector; the internal phase flow injection system consists of a compressed gas cylinder, a pressure reducing valve, a gas flow controller, and a pipe reducer; the PDMS chip consists of polydimethylsiloxane (PDMS) and a glass slide layer.

2. The microfluidic device for observing the generation and movement of microbubbles according to claim 1, characterized in that, Includes the following steps: 1) Firstly, the fluid injector is placed in the injection pump, and the fluid injector is connected to the external phase injection end through a polytetrafluoroethylene (PTFE) line; 2) Furthermore, a pressure reducing valve is installed at the outlet end of the compressed gas cylinder. The pressure reducing valve and the gas flow controller are connected by a steel pipe. The steel pipe is converted into a polytetrafluoroethylene pipeline through a pipe reducer and connected to the inward injection end.

3. A microfluidic method for observing the generation and transport of microbubbles, characterized in that: The PDMS chip includes an external phase injection end, an internal phase injection end, an external phase flow channel, an internal phase flow channel, a cross-shear channel, an "S"-shaped slow flow channel, a waste liquid channel, a waste liquid discharge end, an injection medium channel, a sieving zone, a sieving module, a diversion channel, a decompression channel, a dominant channel, a high-permeability zone, a low-permeability zone, and an oil phase inlet / outlet.

4. A microfluidic method for observing the generation and transport of microbubbles according to claim 3, characterized in that, Includes the following steps: 1) Firstly, a microbubble generation device is provided on the left side of the PDMS chip, including an external phase injection end, an internal phase injection end, an external phase flow channel, an internal phase flow channel, and a cross-cutting channel; 2) Furthermore, an "S"-shaped slow-flow channel is set up, with the width of the slow-flow channel gradually increasing from 200μm to 700μm. The corresponding channel cross-sectional area increases, which can effectively slow down the fluid flow rate. 3) Furthermore, the end of the "S"-shaped slow-flow channel is provided with a waste liquid channel, a waste liquid discharge end and an injection medium channel, wherein the width of the injection medium channel gradually increases from 700μm to 1000μm; 4) Furthermore, screening zones are set up according to the plan, and screening modules are evenly distributed within the screening zones; 5) Furthermore, according to the plan, there are diversion channels, pressure reducing channels and porous media modules, among which the porous media modules are equipped with dominant channels, high permeability zones, low permeability zones and oil phase inlet and outlet ends.

5. A microfluidic method for observing microbubble generation and transport according to claim 4, characterized in that, Includes the following steps: 1) Firstly, in the microbubble generating device, the external phase injection end is connected to the external phase flow channel, and the internal injection end is connected to the internal phase flow channel, wherein an "S"-shaped flow stabilizing channel is provided in both the external phase flow channel and the internal phase flow channel. 2) Furthermore, the outer phase flow channel and the inner phase flow channel are connected to the "S"-shaped slow flow channel in a cross-shaped manner; 3) Furthermore, the waste liquid channel, waste liquid discharge end, and injection medium channel are connected to the end of the "S"-shaped slow flow channel; 4) Furthermore, the end of the injection medium channel is connected to the screening section, the end of the screening section is connected to the diversion channel, a pressure reducing channel is connected at the edge of the diversion channel, and the porous medium chip is introduced into the end of the diversion channel. 5) Furthermore, the porous medium is divided into a dominant channel, a high-permeability zone, and a low-permeability zone, which are interconnected. The end of the porous medium chip is connected to the oil phase inlet and outlet.

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