A droplet manipulation method based on surface charge direct writing technology

Abstract

The present invention relates to a droplet manipulation method based on surface charge direct writing technology. In this technical solution, a needle-tip electrode is used to generate corona discharge under high voltage conditions to deposit a charge pattern on the surface of the film, and the charge pattern on the surface of the film is changed by controlling the movement of the negative needle-tip electrode, thereby generating electrostatic attraction to drive the droplets or eliminating the electrostatic attraction to release the droplets. In the manipulation method provided in the present application, a needle-tip electrode is used to generate corona discharge under high voltage conditions to deposit charges on the surface of a porous insulating film to form a pattern with distinct positive and negative charge areas. Since the deposited charge has a high resolution, the control accuracy of this method is high and the flexibility is good.

Description

Technical Field

[0001] The present invention relates to the field of droplet manipulation technology, and in particular to a droplet manipulation method based on surface charge direct writing technology. Background Art

[0002] Flexible and precise droplet manipulation technology is crucial for fields such as biological detection, chemical synthesis, energy harvesting, and industrial production, such as virus enrichment detection, precise control of chemical reactions, raindrop energy harvesting and power generation, 3D printing manufacturing, and efficient use of pesticides.

[0003] Existing droplet manipulation technologies mostly utilize microchannels, biomimetic structures, functional surfaces, and external stimuli. Microchannel technology is costly and prone to clogging, biomimetic structure technology offers limited control flexibility, functional surfaces are susceptible to contamination and failure, and exhibit poor precision. Manipulation of droplets using external stimuli such as force, light, magnetism, sound, heat, and pH requires additives, which can easily contaminate the droplets and is complex to operate.

[0004] In summary, there is room for improvement and development in droplet manipulation technology to reduce manufacturing costs and improve the flexibility and precision of droplet manipulation. Summary of the Invention

[0005] In response to the above problems, a droplet manipulation method based on surface charge direct writing technology is provided. This method has low manufacturing cost, high manipulation precision and flexibility, and can effectively solve the shortcomings of the existing methods.

[0006] The specific technical solutions are as follows:

[0007] A droplet manipulation method based on surface charge direct writing technology comprises the following steps:

[0008] S1. Installation of the device: Place a positive needle tip electrode and a negative needle tip electrode above and below the membrane, respectively. Place a conductive droplet on the upper surface of the membrane. Connect the positive needle tip electrode to a high-voltage power supply and ground the negative needle tip electrode.

[0009] S2. Droplet capture: Control the negative electrode tip electrode to approach the membrane in a direction perpendicular to the membrane to capture the conductive droplets;

[0010] S3, droplet guidance: control the movement of the negative electrode tip in a direction parallel to the membrane to guide the conductive droplet to move in a directional manner;

[0011] S4. Release of droplets: guiding the conductive droplets to move in a directional manner to the target position and releasing the conductive droplets.

[0012] In this technical solution, a needle-tip electrode is used to generate corona discharge under high-voltage conditions to deposit a charge pattern on the surface of the membrane. By controlling the movement of the negative needle-tip electrode, the charge pattern on the membrane surface is changed, thereby generating electrostatic attraction to drive the droplets or eliminating the electrostatic attraction to release the droplets.

[0013] Preferably, step S1 further includes the following steps:

[0014] S11. Pretreatment of the membrane: taking the membrane and pre-treating the membrane to obtain a smooth super-hydrophobic film.

[0015] Preferably, the pre-treatment method is: completely immerse the membrane in oil, take it out after the membrane is fully soaked, and let it stand for a period of time.

[0016] Preferably, the membrane is a porous insulating membrane with a pore size of 5-15 μm and a thickness of 50-150 μm.

[0017] Preferably, the membrane is selected from but not limited to at least one of polypropylene membrane, polytetrafluoroethylene membrane and polyvinylidene fluoride membrane.

[0018] Preferably, the membrane is placed horizontally, vertically or in a curved manner.

[0019] Preferably, the needle tip electrode is made of a conductive material.

[0020] Preferably, the method for releasing the conductive droplets is: controlling the cathode needle tip electrode to move away from the membrane in a direction perpendicular to the membrane, or turning off the high voltage power supply.

[0021] Preferably, the voltage adjustment range of the high voltage power supply is 5-20 kV.

[0022] The beneficial effects of the above scheme are:

[0023] 1) The control method provided in this application uses a needle-tip electrode to generate corona discharge under high voltage conditions, depositing charges on the surface of the porous insulating film to form a pattern with distinct positive and negative charge regions. Due to the high resolution of the deposited charges, this method has high control accuracy and good flexibility.

[0024] 2) The devices and materials used in the manipulation method provided in this application are simple and readily available, and require no external additives, which reduces the manufacturing cost of droplet manipulation, improves the flexibility of droplet manipulation, and avoids contamination of the conductive droplets;

[0025] 3) The manipulation method provided in this application can be used in conjunction with a mobile device to control the movement of the negative needle tip electrode to achieve programmable and non-contact droplet manipulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flow chart of the droplet manipulation provided in the present invention;

[0027] Figure 2 Schematic diagram of droplet manipulation in Example 1 of the present invention;

[0028] Figure 3 Schematic diagram of droplet manipulation in Example 2 of the present invention.

[0029] In the accompanying figure: 1. Positive needle tip electrode; 2. Conductive droplet; 3. Negative needle tip electrode; 4. Moving device; 5. Membrane; 6. High voltage power supply; 7. Injection pump. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0033] Example 1

[0034] like Figure 1 、 Figure 2 As shown, the droplet manipulation method based on surface charge direct writing technology provided in this embodiment includes the following steps:

[0035] S1. Membrane pretreatment: Take the membrane 5 required for the operation (the membrane 5 can be a polypropylene membrane, a polytetrafluoroethylene membrane or a polyvinylidene fluoride membrane, or other membranes that meet the requirements, with a pore size of 5-15 μm and a thickness of 50-150 μm), immerse the membrane 5 in lubricating oil (the lubricating oil can be silicone oil or other oil that meets the requirements, with a viscosity of 50 cSt), take out the membrane 5 after it is fully soaked, and let it stand for 5 minutes to obtain a smooth membrane 5, so as to make the surface of the membrane 5 smooth and reduce resistance;

[0036] S2. Installation of the device: A positive needle tip electrode 1 and a negative needle tip electrode 3 are respectively arranged above and below the membrane 5 (the needle tip electrodes are made of a conductive material, including but not limited to steel, copper and carbon fiber), and a conductive droplet 2 is placed on the upper surface of the membrane 5, wherein the positive needle tip electrode 1 is 50 mm away from the upper surface of the membrane 5 and is connected to the positive electrode of the high-voltage power supply 6, and the negative needle tip electrode 3 is 5 mm away from the lower surface of the membrane 5 and is mounted on a moving device 4 (the moving device 4 can be a degree of freedom micro-motion platform) and grounded;

[0037] S3, droplet capture: start the high-voltage power supply 6 and adjust it to 9 kV, control the negative electrode tip electrode 3 to approach the membrane 5 through the moving device 4, and use the electrostatic attraction between the circular area on the upper surface of the membrane 5 located directly above the negative electrode tip electrode 3 and the conductive droplet 2 to capture the conductive droplet 2;

[0038] S4, guiding the droplet: controlling the movement of the negative electrode needle tip electrode 3 along the membrane 5 by the moving device 4, so as to guide the conductive droplet 2 to move in a directional manner by utilizing the electrostatic attraction between the circular area on the upper surface of the membrane 5 directly above the negative electrode needle tip electrode 3 and the conductive droplet 2;

[0039] S5. Release of droplets: guide the conductive droplets to move in a directional manner to the target position, control the negative electrode tip electrode 3 to move away from the membrane 5 or turn off the high-voltage power supply 6 through the moving device 4, eliminate the electrostatic attraction between the circular area on the upper surface of the membrane 5 directly above the negative electrode tip electrode 3 and the conductive droplet 2, and make the conductive droplet 2 break away from the control of the negative electrode tip electrode 3.

[0040] Depend on Figure 2 As shown, in Example 1, the positive needle tip electrode 1 and the negative needle tip electrode 3 located on both sides of the membrane 5 generate corona discharge under the high-voltage environment provided by the high-voltage power supply 6, and a charge pattern is deposited on the surface of the membrane 5. The movement of the negative needle tip electrode 3 is controlled by the moving device 4, thereby changing the charge pattern on the surface of the membrane 5, so that the droplets are switched among the three states of capture, guidance and release; when the moving device 4 controls the negative needle tip electrode 3 to approach the membrane 5 and move along the membrane 5, the positive and negative charge areas on the surface of the membrane 5 are distinct, thereby generating electrostatic attraction to drive the conductive droplets 2; when the moving device 4 controls the negative needle tip electrode 3 to move away from the membrane 5, the positive and negative charge areas on the surface of the membrane 5 are not distinct, thereby eliminating the electrostatic attraction to release the conductive droplets 2.

[0041] Example 2

[0042] This embodiment is similar to embodiment 1 except that Figure 3 As shown, the membrane 5 is made of a hydrophobic polytetrafluoroethylene film or a polypropylene film with a diameter of 90 mm, a pore size of 8 μm, and a thickness of 150 μm, and the lubricating oil is made of a viscosity of 50 cSt and a density of 0.96 g / cm 3 The conductive droplets 2 are produced by the injection pump 7, the injection needle of the injection pump 7 is placed horizontally above the membrane 5, the positive needle tip electrode 1 and the negative needle tip electrode 3 are made of steel, with a diameter of 1.0 mm and a length of 46 mm. The moving device 4 adopts a commonly used 4-degree-of-freedom micro-motion platform, and the negative needle tip electrode 3 is installed on the clamp of the moving device 4.

[0043] When the injection pump 7 continuously generates micro-droplets, the micro-droplets do not fall due to the capillary force. At this time, the electrostatic attraction between the circular area on the upper surface of the membrane 5 located directly above the negative needle tip electrode 3 and the conductive droplet 2 adhered to the needle tube of the injection pump 7 is used to overcome the capillary force and capture the conductive droplet 2; the moving device 4 controls the negative needle tip electrode to approach the membrane 5, and by changing the horizontal distance D between the negative needle tip electrode and the needle tube outlet of the injection pump 7, the electrostatic attraction required to overcome the capillary force is adjusted. The electrostatic attraction is related to the droplet volume, so conductive droplets 2 of different sizes can be generated and captured, guided and released.

[0044] The moving device 4 controls the negative electrode needle tip electrode 3 so that the horizontal distance between the negative electrode needle tip electrode 3 and the needle tube outlet of the injection pump 7 is D1. The conductive droplet 2 with a volume of V1 adhering to the needle tube is attracted by electrostatic force, overcomes the capillary force and detaches from the needle tube, and is driven to the top of the negative electrode needle tip 3 and captured, and then guided and released.

[0045] The moving device 4 controls the negative electrode needle tip electrode 3 so that the horizontal distance between the negative electrode needle tip electrode 3 and the needle tube outlet of the injection pump 7 is D2 (D2>D1). The conductive droplet 2 with a volume of V2 (V2>V1) adhered to the needle tube is attracted by the electrostatic force, overcomes the capillary force and detaches from the needle tube, and is driven to the top of the negative electrode needle tip 3 and captured, and then guided and released.

[0046] The above description is only a preferred embodiment of the present invention and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A droplet manipulation method based on surface charge direct writing technology, characterized in that: The steps include: S1. Installation of the device: Place a positive needle tip electrode and a negative needle tip electrode above and below the membrane, respectively. Place a conductive droplet on the upper surface of the membrane. Connect the positive needle tip electrode to a high-voltage power supply and ground the negative needle tip electrode. S2. Droplet capture: Control the negative electrode tip electrode to approach the membrane in a direction perpendicular to the membrane to capture the conductive droplets; S3, droplet guidance: control the movement of the negative electrode tip in a direction parallel to the membrane to guide the conductive droplet to move in a directional manner; S4, droplet release: guiding the conductive droplet to move to the target position and release the conductive droplet; The membrane is a porous insulating membrane with a pore size of 5-15 μm and a thickness of 50-150 μm.

2. The droplet manipulation method according to claim 1, characterized in that: Step S1 also includes the following steps: S11. Pretreatment of the membrane: taking the membrane and pre-treating the membrane to obtain a smooth super-hydrophobic film.

3. The droplet manipulation method according to claim 2, characterized in that: The pretreatment method is: immerse the membrane completely in oil, take it out after the membrane is fully soaked, and let it stand for a period of time.

4. The droplet manipulation method according to claim 1, wherein: The membrane is one of a polypropylene membrane, a polytetrafluoroethylene membrane, and a polyvinylidene fluoride membrane.

5. The droplet manipulation method according to claim 1, wherein: The membrane can be placed horizontally, vertically or bent.

6. The droplet manipulation method according to claim 1, wherein: The needle tip electrode is made of conductive material.

7. The droplet manipulation method according to claim 1, wherein: The method for releasing the conductive droplets is to control the negative electrode tip electrode to move away from the membrane in a direction perpendicular to the membrane, or to turn off the high voltage power supply.

8. The droplet manipulation method according to claim 1, wherein: The voltage regulation range of the high voltage power supply is 5-20kV.

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