Liquid droplet sorting microfluidic chip based on liquid metal electrode and preparation method thereof

By employing a special arrangement of liquid metal electrodes, combined with a microfluidic chip design incorporating PDMS and glass layers, the problems of droplet trajectory and deformation in droplet sorters were solved, achieving high-efficiency droplet sorting under low driving voltage.

CN116764701BActive Publication Date: 2026-06-19SOUTHEAST UNIV
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
SOUTHEAST UNIV
Filing Date
2023-05-12
Publication Date
2026-06-19

AI Technical Summary

Technical Problem

In existing droplet sorters, the trajectory and deformation of droplets in the electric field have not been adequately addressed, and the driving voltage is relatively high, making it difficult to achieve efficient droplet sorting.

Method used

Using liquid metal electrodes as 3D electrode materials, and through a microfluidic chip design combining a PDMS layer and a glass layer with specially arranged liquid metal electrodes, the driving voltage is reduced and droplet deformation is minimized.

Benefits of technology

This method achieves a uniform dielectric force distribution in droplets under low driving voltage, reduces droplet deformation, and improves the efficiency and accuracy of droplet sorting.

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Abstract

This invention discloses a droplet sorting microfluidic chip based on liquid metal electrodes and its fabrication method, belonging to the field of microfluidic chip technology. It solves the technical problems of high driving voltage and large droplet deformation in droplet sorting. The key technical solution is that droplets enter the sorting channel under the acceleration of the spacer oil. When a sufficient voltage is applied to the liquid metal electrode, the droplets in the sorting channel are deflected to the collection channel; when an insufficient voltage is applied or no voltage is applied, the droplets in the sorting channel enter the waste liquid channel. Thus, droplet sorting is achieved through different driving voltages. This invention uses liquid metal as the three-dimensional electrode material, solving the problems of aligning the channel with the electrode in planar electrodes and the high-temperature operation required in three-dimensional electrodes. Simultaneously, the specially arranged liquid metal electrodes achieve droplet sorting with lower driving voltage and smaller droplet deformation, improving chip performance and reducing sorting costs.
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Description

Technical Field

[0001] This application relates to the field of microfluidic chip technology, and in particular to a droplet sorting microfluidic chip based on liquid metal electrodes and its fabrication method. Background Technology

[0002] Droplet microfluidics is the science and technology of generating and manipulating discrete droplets through immiscible multiphase flow within microchannels. Due to its significant advantages, droplet microfluidics has important value in a wide range of fields. Droplet manipulation techniques are the fundamental tools of droplet microfluidics, mainly including droplet sorting, merging, splitting, mixing, and trapping. These techniques have facilitated the application of droplet microfluidics in biology, chemistry, and materials science.

[0003] Sorting and classification are fundamental techniques in droplet microfluidics, widely used in biotechnology, drug screening, and molecular diagnostics. To date, the fastest droplet sorting is achieved by driving droplets with an electric field, based on the principle of dielectrophoresis. However, few studies in existing droplet sorters have focused on the trajectory and deformation of droplets in an electric field. Summary of the Invention

[0004] This application provides a droplet sorting microfluidic chip based on liquid metal electrodes and its fabrication method. The technical objective is to reduce the driving voltage for droplet sorting and reduce the deformation of the sorted droplets.

[0005] The above-mentioned technical objective of this application is achieved through the following technical solution:

[0006] A droplet sorting microfluidic chip based on a liquid metal electrode comprises, from top to bottom, a PDMS layer and a glass layer. The PDMS layer is bonded to the glass layer by a plasma cleaning process. The PDMS layer is equipped with a droplet re-injection module, a sorting channel module, and a sorting electrode module. The droplet re-injection module includes a spacer oil inlet, a spacer oil channel, a re-injection droplet inlet, a re-injection droplet channel, a micropillar array one, and a micropillar array two. The sorting channel module includes a sorting channel, a collection channel, a collection outlet, a waste liquid channel, and a waste liquid outlet. The sorting electrode module includes an active electrode channel, a ground electrode first channel, a ground electrode second channel, and a ground electrode third channel. One end of the active electrode channel is connected to the active electrode inlet, and the other end is connected to the active electrode outlet. One end of the ground electrode first channel is connected to the ground electrode first inlet, and the other end is connected to the ground electrode first outlet. One end of the ground electrode second channel is connected to the ground electrode second inlet, and the other end is connected to the ground electrode second outlet. The ground electrode third channel includes two interconnected channels, one channel is connected to the ground electrode third outlet, and the other channel is connected to the ground electrode third inlet.

[0007] The spacer oil inlet, micro-column array one and spacer oil flow channel are connected in sequence, and the re-injection droplet inlet, micro-column array two and re-injection droplet flow channel are connected in sequence. The spacer oil flow channel and the re-injection droplet flow channel are both connected to the sorting flow channel.

[0008] The sorting channel is connected to both the collection channel and the waste liquid channel. The collection channel is connected to the collection outlet, and the waste liquid channel is connected to the waste liquid outlet.

[0009] The ground electrode first flow channel, the active electrode flow channel, and the ground electrode second flow channel are located on one side of the sorting flow channel, and the ground electrode third flow channel is located on the other side of the sorting flow channel; the ground electrode first flow channel and the ground electrode second flow channel are symmetrical about the active electrode flow channel; one flow channel of the ground electrode third flow channel is symmetrical about the sorting flow channel with the ground electrode first flow channel, and the other flow channel is symmetrical about the sorting flow channel with the ground electrode second flow channel;

[0010] Liquid metal is injected into the active electrode channel, the first ground electrode channel, the second ground electrode channel, and the third ground electrode channel.

[0011] A method for fabricating a droplet sorting microfluidic chip based on liquid metal electrodes, the method being used to manufacture the microfluidic chip described in this application, includes: simultaneously fabricating active electrode channels, ground electrode one channel, ground electrode two channel, and ground electrode three channel, as well as collection channel, waste liquid channel, sorting channel, spacer oil channel, and re-injection droplet channel on a PDMS layer by photolithography in a single step; then performing molding and bonding on a glass layer; finally injecting liquid metal into the fabricated active electrode channels, ground electrode one channel, ground electrode two channel, and ground electrode three channel, and inserting a metal connector to obtain the droplet sorting microfluidic chip based on liquid metal electrodes.

[0012] The beneficial effects of this application are as follows:

[0013] (1) This application uses liquid metal as the three-dimensional electrode material, which solves the problem that current planar electrodes (such as ITO electrodes and gold electrodes) require alignment of the flow channel with the electrode and the problem that three-dimensional electrodes (such as silver paste electrodes and low melting point alloy electrodes) require high-temperature operation. Liquid metal remains liquid at room temperature and does not require high-temperature treatment; three-dimensional electrodes also do not require alignment of the electrode with the flow channel.

[0014] (2) This application uses liquid metal electrodes with a special arrangement. Under this special arrangement, the dielectric force on the droplets is more uniform, and the droplet sorting can be achieved with very low driving voltage and very small droplet deformation. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of this application;

[0016] Figure 2 This is an exploded view of the overall structure of this application;

[0017] Figure 3 This is a schematic diagram of the PDMS layer structure in this application;

[0018] Figure 4 This is a partial enlarged view of the sorting channel module in this application;

[0019] Figure 5 This is a schematic diagram of the fabrication method of the liquid metal electrode in this application and a physical chip image;

[0020] Figure 6 The simulation results of the droplet sorting microfluidic chip of this application are shown in the figure.

[0021] Figure 7 The figure shows the experimental results of the droplet sorting microfluidic chip of this application when the oil flow rate is 100 μL / h and the subsequent droplet flow rate is 20 μL / h.

[0022] Figure 8 The figure shows the experimental results of the droplet sorting microfluidic chip of this application when the oil flow rate is 500 μL / h and the subsequent droplet flow rate is 20 μL / h.

[0023] Figure 9 The figure shows the experimental results of the droplet sorting microfluidic chip of this application when the oil flow rate is 1000 μL / h and the subsequent droplet flow rate is 20 μL / h.

[0024] In the diagram: 1-PDMS layer, 2-glass layer, 3-ground electrode inlet 1, 4-ground electrode outlet 1, 5-ground electrode flow channel 1, 6-active electrode inlet, 7-active electrode outlet, 8-active electrode flow channel, 9-ground electrode inlet 2, 10-ground electrode outlet 2, 11-ground electrode flow channel 2, 12-collection outlet, 13-collection flow channel, 14-waste liquid flow channel, 15-waste liquid outlet, 16-ground electrode outlet 3, 17-ground electrode flow channel 3, 18-ground electrode inlet 3, 19-sorting flow channel, 20-spacer oil flow channel, 21-reinjection droplet flow channel, 22-reinjection droplet inlet, 23-spacer oil inlet, 24-microcolumn array 1, 25-microcolumn array 2. Detailed Implementation

[0025] The technical solution of this application will be described in detail below with reference to the accompanying drawings.

[0026] The droplet sorting microfluidic chip based on liquid metal electrodes described in this application, such as... Figure 1 and Figure 2As shown, from top to bottom, it includes a PDMS layer 1 and a glass layer 2. The PDMS layer 1 is bonded to the glass layer 2 by a plasma cleaning machine, and various flow channel structures are located on the PDMS layer 1.

[0027] like Figure 3 As shown, the PDMS layer includes a droplet re-injection module, a sorting channel module, and a sorting electrode module. The droplet re-injection module is used for droplet injection, droplet velocity control, and droplet spacing adjustment. The sorting channel module has two or more outlets for droplet sorting and classification. The sorting electrode module contains specially arranged liquid metal electrodes for controlling droplet movement within the sorting channel. The liquid metal electrodes are formed by injecting liquid metal into the electrode channel. The droplet metal is a metal that is liquid at room temperature, such as gallium-indium alloy and gallium-indium-tin alloy.

[0028] The droplet re-injection module includes a spacer oil inlet 23, a spacer oil channel 20, a re-injection droplet inlet 22, a re-injection droplet channel 21, a micropillar array one 24, and a micropillar array two 25. The spacer oil inlet 23, the micropillar array one 24, and the spacer oil channel 20 are connected in sequence, and the re-injection droplet inlet 22, the micropillar array two 25, and the re-injection droplet channel 21 are connected in sequence.

[0029] Droplets enter the re-injection droplet channel 21 through the re-injection droplet inlet 22; the re-injection droplet channel 21 includes a second micropillar array 25 to block impurities from entering the sorting channel 19; the spacer oil enters the spacer oil channel 20 through the spacer oil inlet 23; the spacer oil channel 20 includes a first micropillar array 24 to block impurities from entering the sorting channel 19.

[0030] The sorting channel module includes a sorting channel 19, a collection channel 13, a collection outlet 12, a waste liquid channel 14, and a waste liquid outlet 15. The sorting channel 19 is connected to both the re-injection droplet channel 21 and the spacer oil channel 20. Droplets and spacer oil enter the sorting channel 19 through the re-injection droplet channel 21 and the spacer oil channel 20, respectively.

[0031] The sorting channel 19 is connected to both the collection channel 13 and the waste liquid channel 14. By controlling the sorting electrode module, the droplets can enter either the collection outlet 12 or the waste liquid outlet 15.

[0032] The sorting electrode module includes an active electrode channel 8, a ground electrode first channel 5, a ground electrode second channel 11, and a ground electrode third channel 17. One end of the active electrode channel 8 is connected to an active electrode inlet 6, and the other end is connected to an active electrode outlet 7. One end of the ground electrode first channel 5 is connected to a ground electrode first inlet 3, and the other end is connected to a ground electrode first outlet 4. One end of the ground electrode second channel 11 is connected to a ground electrode second inlet 9, and the other end is connected to a ground electrode second outlet 10. The ground electrode third channel 17 includes two interconnected channels, one channel is connected to a ground electrode third outlet 16, and the other channel is connected to a ground electrode third inlet 18.

[0033] Ground electrode channel 5, active electrode channel 8, and ground electrode channel 11 are located on one side of sorting channel 19, and ground electrode channel 17 is located on the other side of sorting channel 19; ground electrode channel 5 and ground electrode channel 11 are symmetrical about active electrode channel 8; one channel of ground electrode channel 17 is symmetrical about ground electrode channel 5 about sorting channel 19, and the other channel is symmetrical about ground electrode channel 11 about sorting channel 19.

[0034] The active electrode channel 8 is rectangular in shape near the sorting channel 19; the ground electrode channel 5, ground electrode channel 11, and ground electrode channel 17 are all triangular in shape near the sorting channel 19.

[0035] like Figure 4 As shown, the height of the sorting channel 19 is 1 times the diameter of the sorted droplet, and the width is 2 times the diameter of the sorted droplet.

[0036] The height of the grounding electrode first channel 5, the grounding electrode second channel 11, and the grounding electrode third channel 17 is 1 times the diameter of the sorted droplet, and the width is 2 times the diameter of the sorted droplet.

[0037] The shortest distance between the active electrode channel 8, the ground electrode channel 1 5, the ground electrode channel 2 11, and the ground electrode channel 3 17 and the sorting channel 19 is 1 times the diameter of the sorted droplet.

[0038] The shortest distance between the ground electrode first flow channel 5 and the ground electrode second flow channel 11 and the active electrode flow channel 8 is 0.25 to 1 times the diameter of the sorted droplet; the total length of the flow channel parallel to the sorting flow channel 19 on the active electrode flow channel 8 is 4 to 8 times the diameter of the sorted droplet.

[0039] The fabrication method of the droplet sorting microfluidic chip based on liquid metal electrodes described in this application is as follows: Figure 5As shown, firstly, active electrode channels 8, ground electrode channel 5, ground electrode channel 11, and ground electrode channel 17, as well as collection channel 13, waste liquid channel 14, sorting channel 19, spacer oil channel 20, and re-injection droplet channel 21 are simultaneously fabricated on PDMS layer 1 using a single photolithography process. Then, molding and bonding are performed on glass layer 2. Finally, liquid metal is injected into the fabricated active electrode channels 8, ground electrode channel 5, ground electrode channel 11, and ground electrode channel 17, and metal connectors are inserted to obtain a droplet sorting microfluidic chip based on liquid metal electrodes. The final fabricated chip is shown below. Figure 5 As shown in (f).

[0040] Figure 6 The simulation results of the sorting channel 19 obtained using COMSOL Multiphysics 5.5 show that a large dielectric force is distributed near the active electrode and passes through the droplet streamline, resulting in uniform force on the droplet, which is beneficial for reducing the driving voltage. The droplet deforms under the influence of the dielectric force and at the bifurcation point. In this embodiment, the electrode arrangement distributes the dielectric force before the connection between the sorting channel 19 and the collection channel 13 and waste liquid channel 14, preventing the superposition of droplet deformation under the influence of the dielectric force and at the bifurcation point, thus reducing the maximum droplet deformation.

[0041] Figure 7 The figure shows the experimental results of the droplet sorting microfluidic chip in this embodiment when the oil flow rate is 100 μL / h and the subsequent droplet flow rate is 20 μL / h. It can be seen that only an 80V driving voltage is required for the droplets to be completely deflected into the collection channel 13, thus achieving droplet sorting.

[0042] Figure 8 The figure shows the experimental results of the droplet sorting microfluidic chip in this embodiment when the oil flow rate is 500 μL / h and the injected droplet flow rate is 20 μL / h. It can be seen that only a 130V driving voltage is required for the droplets to be completely deflected into the collection channel 13, thus achieving droplet sorting.

[0043] Figure 9 The figure shows the experimental results of the droplet sorting microfluidic chip in this embodiment when the oil flow rate is 1000 μL / h and the injected droplet flow rate is 20 μL / h. It can be seen that only a 160V driving voltage is required for the droplets to be completely deflected into the collection channel 13, thus achieving droplet sorting.

[0044] In the above embodiments, the specific operation process is as follows:

[0045] Droplets enter the re-injection droplet channel 21 through the re-injection droplet inlet 22, while the spacer oil enters the spacer oil channel 20 through the spacer oil inlet 23. The spacer oil accelerates the droplets into the sorting channel 19. By applying alternating current to the liquid metal in the active electrode channel 8, the liquid metal in the grounding electrode channel 5, the grounding electrode channel 11, and the grounding electrode channel 17 is grounded, causing the droplets in the sorting channel 19 to be subjected to dielectric force and deflected to the collection channel 13, finally flowing out from the collection outlet 12. When no voltage is applied to the liquid metal electrode or the driving voltage is insufficient, the droplets cannot be deflected to the collection channel 13 and enter the waste liquid channel 14, finally flowing out from the waste liquid outlet 15.

[0046] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the specific embodiments described above. The specific embodiments and descriptions in the specification are merely for further illustrating the principles of the invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the claims and their equivalents.

Claims

1. A droplet sorting microfluidic chip based on a liquid metal electrode, comprising, from top to bottom, a PDMS layer (1) and a glass layer (2), wherein the PDMS layer (1) is bonded to the glass layer (2) by a plasma cleaning process, characterized in that, The PDMS layer (1) is provided with a droplet re-injection module, a sorting channel module, and a sorting electrode module; the droplet re-injection module includes a spacer oil inlet (23), a spacer oil channel (20), a re-injection droplet inlet (22), a re-injection droplet channel (21), a micropillar array one (24), and a micropillar array two (25); the sorting channel module includes a sorting channel (19), a collection channel (13), a collection outlet (12), a waste liquid channel (14), and a waste liquid outlet (15); the sorting electrode module includes an active electrode channel (8), a ground electrode one channel (5), and a ground electrode two channel (8). 11) and the ground electrode three-channel (17), the active electrode channel (8) is connected to the active electrode inlet (6) at one end and the active electrode outlet (7) at the other end, the ground electrode one-channel (5) is connected to the ground electrode one-inlet (3) at one end and the ground electrode one-outlet (4) at the other end, the ground electrode two-channel (11) is connected to the ground electrode two-inlet (9) at one end and the ground electrode two-outlet (10) at the other end; the ground electrode three-channel (17) includes two interconnected channels, one channel is connected to the ground electrode three-outlet (16) and the other channel is connected to the ground electrode three-inlet (18); The spacer oil inlet (23), micro-column array one (24) and spacer oil channel (20) are connected in sequence, and the re-injection droplet inlet (22), micro-column array two (25) and re-injection droplet channel (21) are connected in sequence. The spacer oil channel (20) and the re-injection droplet channel (21) are both connected to the sorting channel (19). The sorting channel (19) is connected to the collection channel (13) and the waste liquid channel (14). The collection channel (13) is connected to the collection outlet (12), and the waste liquid channel (14) is connected to the waste liquid outlet (15). The ground electrode channel 1 (5), the active electrode channel (8), and the ground electrode channel 2 (11) are located on one side of the sorting channel (19), and the ground electrode channel 3 (17) is located on the other side of the sorting channel (19); the ground electrode channel 1 (5) and the ground electrode channel 2 (11) are symmetrical about the active electrode channel (8); one channel of the ground electrode channel 3 (17) is symmetrical about the ground electrode channel 1 (5) about the sorting channel (19), and the other channel is symmetrical about the ground electrode channel 2 (11) about the sorting channel (19); this electrode arrangement distributes the dielectric force before the connection between the sorting channel (19) and the collection channel (13) and the waste liquid channel (14); Liquid metal is injected into the active electrode flow channel (8), the ground electrode first flow channel (5), the ground electrode second flow channel (11) and the ground electrode third flow channel (17); The height of the ground electrode first channel (5), the ground electrode second channel (11) and the ground electrode third channel (17) is 1 times the diameter of the sorted droplet, and the width is 2 times the diameter of the sorted droplet. The shortest distance between the active electrode channel (8), the ground electrode first channel (5), the ground electrode second channel (11), and the ground electrode third channel (17) and the sorting channel (19) is 1 times the diameter of the sorted droplet; The shortest distance between the ground electrode first flow channel (5) and the ground electrode second flow channel (11) and the active electrode flow channel (8) is 0.25 to 1 times the diameter of the sorted droplet; The total length of the active electrode flow channel (8) parallel to the sorting flow channel (19) is 4 to 8 times the diameter of the sorted droplets.

2. The microfluidic chip as described in claim 1, characterized in that, The height of the sorting channel (19) is 1 times the diameter of the sorted droplet, and the width is 2 times the diameter of the sorted droplet.

3. The microfluidic chip as described in claim 1, characterized in that, The active electrode channel (8) is rectangular in shape near the sorting channel (19), and the ground electrode channel (5), ground electrode channel (11) and ground electrode channel (17) are triangular in shape near the sorting channel (19).

4. The microfluidic chip as described in claim 1, characterized in that, The liquid metal is a metal that is liquid at room temperature, including gallium-indium alloy and gallium-indium-tin alloy.

5. The microfluidic chip as described in claim 1, characterized in that, The active electrode channel (8) is located before the connection between the sorting channel (19) and the collection channel (13) and the waste liquid channel (14).

6. A method for fabricating a droplet sorting microfluidic chip based on a liquid metal electrode, the method being used to manufacture the microfluidic chip according to any one of claims 1-5, characterized in that, include: By photolithography, active electrode channels (8), ground electrode channel 1 (5), ground electrode channel 2 (11) and ground electrode channel 3 (17), as well as collection channel (13), waste liquid channel (14), sorting channel (19), spacer oil channel (20) and re-injection droplet channel (21) for introducing liquid metal are simultaneously fabricated on the PDMS layer (1). Then, molding and bonding are performed on the glass layer (2). Finally, liquid metal is injected into the fabricated active electrode channels (8), ground electrode channel 1 (5), ground electrode channel 2 (11) and ground electrode channel 3 (17), and metal connectors are inserted to obtain a droplet sorting microfluidic chip based on liquid metal electrodes.