Liquid drop control system and liquid drop control method based on electric heating micro-fluidic chip

Abstract

The invention discloses a liquid drop control system based on an electric heating micro-fluidic chip. The liquid drop control system comprises the electric heating micro-fluidic chip, an annular cooling unit and a microprocessor, the electric heating micro-fluidic chip comprises an operation pool formed in a substrate, at least one heating electrode is arranged in the substrate at the bottom of the operation pool, and an annular cooling unit is arranged on the periphery of the operation pool; the operation pool is used for containing lipid liquid and water-containing liquid drops dropwise added into the lipid liquid, and the microprocessor is used for controlling the temperature of the annular cooling unit and the temperature of the heating electrode to achieve thermal field control over the water-containing liquid drops. The invention further discloses a liquid drop control method thereof, through a non-contact thermal field control mode, the pollution risk caused by liquid drop contact is avoided, rapid and flexible multifunctional control over water-containing liquid drops can be achieved, and the defect that a traditional control mode is single in function is overcome.

Description

Technical Field

[0001] This invention belongs to the fields of micro-nano manipulation technology and synthetic biology, specifically a non-contact droplet manipulation system and method based on an electrothermal microfluidic chip. Background Technology

[0002] Droplet synthetic biology is an emerging interdisciplinary field that combines elements of microfluidics, synthetic biology, and chemical engineering. This technology utilizes tiny droplets as microreactors to achieve the synthesis and screening of biomolecules. This approach holds broad promise for applications in drug development, genetic engineering, and biosensoring. The phospholipid bilayer is a fundamental component of biological membranes, playing a crucial role in cell structure and function. Research on droplets with phospholipid bilayers is not only essential for understanding cell biology but also a core technology in droplet synthetic biology, providing a foundation for drug delivery, the design of biosensors, and the construction of artificial cells. Currently, in the assembly of aqueous droplets in lipid-oil solutions, phospholipid molecules typically adsorb onto the oil-water surface, forming a monolayer of phospholipid molecules on both the aqueous and oil phases. When two aqueous droplets come into contact, the monolayers fuse to form a phospholipid bilayer interface. This droplet assembly method is the mainstream synthetic approach. However, current manipulation methods are limited to assembling droplets using contact-based micro-tweezers or by preparing specific geometries and utilizing gravity. It is difficult to achieve droplet clusters with different patterns, dimensions, and functions. Non-contact methods, such as those using light, electric, acoustic, or magnetic fields, require specialized equipment and complex manipulation. These operational limitations severely restrict the development of droplet synthetic biology. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a droplet manipulation system and method based on an electrothermal microfluidic chip. This non-contact operation method utilizes the principle of thermal field, namely the temperature difference generated by an asymmetric heat source, to produce thermal convection and thermocapillary force in the fluid environment, thereby achieving droplet manipulation.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] A droplet manipulation system based on an electrothermal microfluidic chip includes an electrothermal microfluidic chip, an annular cooling unit, and a microprocessor. The electrothermal microfluidic chip includes an operating cell formed in a substrate, at least one heating electrode arranged in the substrate at the bottom of the operating cell, and the annular cooling unit disposed around the operating cell. The operating cell is used to contain a lipid liquid and water-containing droplets added to the lipid liquid. The microprocessor is used to control the temperature of the annular cooling unit and the heating electrode to achieve thermal field manipulation of the water-containing droplets.

[0006] Optionally, it also includes a microscope camera, which is positioned above the operating pool and signal-connected to the microprocessor.

[0007] Optionally, the substrate is integrally formed by 3D printing.

[0008] Optionally, the substrate at the bottom of the operating pool is provided with microchannels, and the heating electrode is formed by filling the microchannels with conductive material.

[0009] Optionally, a plurality of heating electrodes are arranged at intervals in the substrate at the bottom of the operating pool, and the microprocessor controls the heating state of the plurality of heating electrodes individually.

[0010] A droplet manipulation method, employing the aforementioned droplet manipulation system based on an electrothermal microfluidic chip, includes the following steps:

[0011] S1. Place the lipid solution into the operating tank;

[0012] S2 drips the aqueous solution into the lipid solution;

[0013] S3 sets the temperature of the annular cooling unit and constructs a thermal field by controlling the heating state of the heating electrodes to manipulate water-containing droplets.

[0014] Optionally, the volume of the aqueous droplet is 0.1 μL to 2 μL.

[0015] The lipid solution mentioned here refers to a homogeneous liquid formed by dissolving hydrophobic lipid molecules in a nonpolar organic solvent.

[0016] The aqueous droplets mentioned here can be pure water, or aqueous solutions containing functional substances, hydrogels, or droplets formed by functional substances dispersed in water.

[0017] Optionally, the aqueous droplet contains a biological sample, including at least one of cells, bacteria, proteins, DNA, exosomes, aptamers, and a corresponding hydrogel droplet.

[0018] Optionally, the manipulation of the water-containing droplets includes controlling the movement, assembly, and release of the water-containing droplets.

[0019] Optionally, the lipid solution is an oil phase solution, including at least one of hexadecane and silicone oil.

[0020] Optionally, when multiple aqueous droplets are present in the lipid solution, the movement, aggregation, assembly, or relative motion between the multiple aqueous droplets can be controlled by controlling the heating state of the heating electrode.

[0021] Optionally, when multiple heating electrodes are arranged at intervals, the movement of water-containing droplets along a specific path can be achieved by sequentially controlling the multiple heating electrodes, including but not limited to linear movement, zigzag movement, curved movement, or rotation.

[0022] Optionally, when the aqueous droplet contains biological samples, it can enable the synthesis and screening of biomolecules, including but not limited to polymerase chain reaction, translation and transcription of genetic material.

[0023] The beneficial effects of the present invention are:

[0024] 1. Through non-contact thermal field manipulation, water-containing droplets can be rapidly manipulated and multiple functions can be achieved, such as assembly, movement and release. This overcomes the single-function limitations of traditional manipulation methods, allows for the formation of more complex droplet combinations or motion states, and avoids the risk of contamination from contact with droplets. It has wide applications in synthetic biology.

[0025] 2. The electro-heated microfluidic chip droplet manipulation system does not require complex and precise processing methods and can be manufactured using existing commercial 3D printing techniques. The heating electrodes are fabricated using liquid metal filling, allowing for free placement of the electrodes and control over different numbers of droplets. It offers advantages such as portability, low cost, and high controllability.

[0026] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0027] Figure 1 This is a side view of the droplet manipulation system based on an electrothermal microfluidic chip in Example 1.

[0028] Figure 2 This is a top view of the electroheated microfluidic chip of Example 1, showing the position of the heating electrodes.

[0029] Figure 3 This is a graph showing the temperature change of the heating electrode under different currents in Example 1;

[0030] Figure 4 This is a schematic diagram of the assembly of multiple droplets in the droplet manipulation method of Example 1;

[0031] Figure 5 This is a top view of the electroheated microfluidic chip in Example 2, showing the position of the heating electrodes.

[0032] Figure 6 This is a schematic diagram of droplet maze movement in the droplet manipulation method of Example 2;

[0033] Figure 7 This is a top view of the electroheated microfluidic chip in Example 3, showing the position of the heating electrodes.

[0034] Figure 8 This is a schematic diagram of droplet rotation in the droplet manipulation method of Example 3. Detailed Implementation

[0035] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. The accompanying drawings are merely illustrative to facilitate a better understanding of the invention, and their specific proportions can be adjusted according to design requirements.

[0036] Example 1

[0037] Please refer to Figure 1 and Figure 2 This embodiment of the droplet manipulation system based on an electrothermal microfluidic chip includes an electrothermal microfluidic chip 1, a ring-shaped cooling unit 2, a microprocessor 3, and a microscope camera 4. The electrothermal microfluidic chip 1 includes an operating pool 12 formed in a substrate 11, with a heating electrode 13 disposed in the substrate 11 at the bottom of the operating pool 12. The substrate 11 of the electrothermal microfluidic chip 1 is made of materials such as polytetrafluoroethylene (PTFE) or polylactic acid (PLA), and is formed into the desired shape by 3D printing, for example, forming a substrate and sidewalls on the substrate, which together form the operating pool 12. For example, a microchannel is integrally formed within the substrate at the bottom of the operating pool 12. The desired heating electrode 13 is flexibly formed by filling the microchannel with a conductive material, which can be liquid metal or a polymer conductive material, etc. Alternatively, the substrate can be microfabricated to create a metal electrode. When current flows through the heating electrode 13, heat is generated due to the resistance of the material, and electrical energy is directly converted into thermal energy, thereby achieving temperature control through electrothermal heating. An annular cooling unit 2 is located around the operating pool 12, and can be, for example, a water-cooling device. The operating pool 12 is used to contain lipid liquid A and water-containing droplets B added to lipid liquid A. A microscope camera 4 is located above the operating pool 12 and is signal-connected to the microprocessor 3 for observing real-time images within the operating pool 12. The microprocessor 3 is connected to the annular cooling unit 2 and the heating electrode 13, and controls the thermal field of the water-containing droplets by controlling the temperature of the annular cooling unit 2 and the heating electrode 13.

[0038] The annular cooling unit 2 is used to keep the lipid liquid A at a stable low temperature. The heating electrode 13 realizes the local heating of the lipid liquid A, which generates a higher temperature locally. As a result, due to the temperature difference generated by the asymmetric heat source, thermal convection and thermal capillary force are generated in the environment of the lipid liquid A, forming a non-contact "thermal tweezers" that drive the water-containing droplet B to move.

[0039] In this embodiment, the 3D-printed substrate has dimensions of 16.5*16.5*4mm, and the resulting operating pool 12 has dimensions of 8*8*3mm. The annular cooling unit 2 is assembled on the outer sidewall of the operating pool 12 and supported on the substrate. The heating electrode 13 is embedded in the substrate at the bottom center of the operating pool 12, with dimensions of 0.4*0.3*0.15mm. This part of the structure is the narrowest, and the cross-sectional area of ​​the other liquid metal-filled channels is 1*1mm. The heating electrode 13 is made of liquid metal gallium indium (GaIn) alloy, and its temperature changes with the current as follows: Figure 3 As shown, a lipid solution A (20 mg / ml) of hexadecane and silicone oil (v / v 4:1) was added to the operating cell 12. A PBS buffer solution containing rhodamine fluorescent dye was used as the aqueous droplet B. Eight 0.5 μL drops of aqueous droplet B were added to the sample cell 12 using a pipette. The power to the heating electrode 13 was turned on, and under the control of the microprocessor 3, the annular cooling unit 2 was activated and the temperature was set to 20°C. Here, the assembly of the eight aqueous droplets B was performed under conditions of 1.9A and a maximum heating temperature of 37°C. The movement of the aqueous droplets B and the formation of the phospholipid bilayer could be recorded in real time by the microscope camera 4. Figure 4 As shown, after 36 seconds, eight aqueous droplets B assembled into a petal shape, and after 252 seconds, a phospholipid bilayer formed between the droplets. The formation rate is fast, the assembly is convenient, and the controllability is strong.

[0040] Example 2

[0041] The droplet manipulation system based on an electrothermal microfluidic chip in Example 2 is largely the same as that in Example 1, except that the bottom of its operating pool 12 is provided with multiple baffles 14, which form a maze-like passageway. Multiple spaced heating electrodes, such as heating electrodes 13a, 13b, 13c, and 13d, are disposed in the bottom substrate of the passageway. Figure 5 As shown. Each heating electrode 13a, 13b, 13c, and 13d is independently controlled by the microprocessor 3. The remaining settings are as described in Example 1.

[0042] This embodiment provides a flexible method for manipulating liquids through a complex maze. A lipid solution A (20 mg / ml) of hexadecane and silicone oil (v / v 4:1) is added to the operating cell 12. A PBS buffer solution containing rhodamine fluorescent dye is used as an aqueous droplet B. One 0.5 μL droplet of aqueous droplet B is added to the sample cell 12 using a pipette. Under the control of the microprocessor 3, the annular cooling unit 2 is turned on and the temperature is set to 20°C. Under the control of the microprocessor 3, the power supplies to heating electrodes 13a, 13b, 13c, and 13d are sequentially turned on (operation mode: the previous heating electrode is turned off before the next heating electrode is turned on). Here, a 1.9A power supply with a maximum heating temperature of 37°C is used to guide the droplet along a designated route, ultimately allowing it to move to the maze exit. Figure 6 As shown, it enables precise control over the movement of droplets along complex paths.

[0043] Example 3

[0044] The droplet manipulation system based on an electrothermal microfluidic chip in Example 3 is largely the same as that in Example 1, except that a plurality of spaced heating electrodes are disposed in the bottom substrate of its operating cell 12, for example, heating electrodes 13e, 13f, 13g and 13h. Figure 7 As shown. Each heating electrode is independently controlled by the microprocessor 3. The remaining settings are the same as in Example 1.

[0045] A lipid solution A (20 mg / ml) of hexadecane and silicone oil (v / v 4:1) was added to operation cell 12. A PBS buffer solution containing rhodamine fluorescent dye was used as aqueous droplet B. 0.5 μL of aqueous droplet B1 and 0.9 μL of aqueous droplet B2 were pipetted into operation cell 12 and assembled together. A metal wire 5 (diameter: 0.1 mm) was used to anchor the combined droplet between the four electrodes, with the anchoring point located at the center of aqueous droplet B2. Under the control of microprocessor 3, the annular cooling unit 2 was turned on and the temperature was set to 20°C. Under the control of microprocessor 3, the power supplies to heating electrodes 13e, 13f, 13g, and 13h were sequentially turned on (the previous heating electrode was turned off before the next one was turned on), which enabled the rotation of aqueous droplet B1. Figure 8 As shown, it enables precise control over the complex motion patterns of droplets.

[0046] The above embodiments are only used to further illustrate the droplet manipulation system and droplet manipulation method based on an electrothermal microfluidic chip of the present invention. However, the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A droplet manipulation system based on an electrothermal microfluidic chip, characterized in that: The device includes an electrothermal microfluidic chip, a ring-shaped cooling unit, and a microprocessor. The electrothermal microfluidic chip includes an operating cell formed in a substrate, at least one heating electrode arranged in the substrate at the bottom of the operating cell, and a ring-shaped cooling unit disposed around the operating cell. The operating cell is used to contain lipid liquid and water-containing droplets added to the lipid liquid. The microprocessor is used to control the temperature of the ring-shaped cooling unit and the heating electrode to achieve thermal field manipulation of the water-containing droplets.

2. The droplet manipulation system based on an electrothermal microfluidic chip according to claim 1, characterized in that: It also includes a microscope camera, which is located above the operating pool and is signal-connected to the microprocessor.

3. The droplet manipulation system based on an electrothermal microfluidic chip according to claim 1, characterized in that: The substrate is formed in one piece by 3D printing.

4. The droplet manipulation system based on an electrothermal microfluidic chip according to claim 1, characterized in that: The substrate at the bottom of the operating pool is provided with microchannels, and the heating electrode is formed by filling the microchannels with conductive material.

5. The droplet manipulation system based on an electrothermal microfluidic chip according to claim 1, characterized in that: Multiple heating electrodes are arranged at intervals in the substrate at the bottom of the operating pool, and the microprocessor controls the heating state of the multiple heating electrodes individually.

6. A method for manipulating droplets, characterized in that: The droplet manipulation method employs the droplet manipulation system based on an electrothermal microfluidic chip as described in any one of claims 1 to 5, and includes the following steps: S1. Place the lipid solution into the operating tank; S2 drips the aqueous solution into the lipid solution; S3 sets the temperature of the annular cooling unit and constructs a thermal field by controlling the heating state of the heating electrodes to manipulate water-containing droplets.

7. The droplet manipulation method according to claim 1, characterized in that: The volume of the aqueous droplet is 0.1 μL to 2 μL.

8. The droplet manipulation method according to claim 1, characterized in that: The aqueous droplet contains a biological sample, including at least one of cells, bacteria, proteins, DNA, exosomes, and aptamers.

9. The droplet manipulation method according to claim 1, characterized in that: The manipulation of water-containing droplets includes controlling the movement, assembly, and release of the water-containing droplets.

10. The droplet manipulation method according to claim 1, characterized in that: The lipid solution is an oil phase solution, including at least one of hexadecane and silicone oil.

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