Micro-droplet driving chip and preparation method thereof

Abstract

The invention relates to a micro-droplet driving chip and a preparation method thereof, belongs to the technical field of digital microfluidics, and solves the problem that a chip manufactured by adopting a PCB (Printed Circuit Board) technology in the prior art has defects in the aspect of droplet driving. The method comprises the following steps: preparing a plurality of electrodes which are tightly arranged on a PCB substrate to form an electrode layer, and enabling each electrode to respectively cover a corresponding guide hole in the PCB substrate; filling the guide holes with a filling material, and filling gaps between the electrodes with an insulating material; the surface of the electrode layer is polished, so that the surface of the electrode layer is flat and smooth; and sequentially preparing a dielectric layer and a hydrophobic layer on the surface of the polished electrode layer to obtain the lower electrode plate of the micro-droplet driving chip. According to the micro-droplet driving chip, the moving resistance of the droplet on the chip can be greatly reduced, and the droplet can be driven more easily when the control electrode is converted.

Description

Technical Field

[0001] The present invention relates to the technical field of digital microfluidics, and in particular to a micro-droplet driving chip and a preparation method thereof. Background Art

[0002] Lab on a Chip (LOC) refers to connecting multiple units or modules with different functions on a microscale, and collaboratively completing a series of complex biochemical analysis tasks such as sample preparation, biological and chemical reactions, separation and detection. The key to the lab on a chip is digital microfluidics, that is, the technology for generating and controlling discrete droplets in microdevices. Among them, the electrowetting effect on the medium (Electrowetting-On-Dielectric, EWOD) is the basis of digital microfluidics, which refers to the use of electrostatic force to change the hydrophilicity of liquids to solids, which is specifically manifested as the change in the contact angle of droplets on the solid surface. If the contact angle changes asymmetrically, a gradient of surface tension will appear at the contact line on both sides of the droplets, causing the droplets to migrate and move.

[0003] The micro-droplet drive chip is the core component of digital microfluidics technology. In the prior art, the substrate of the micro-droplet drive chip is mostly made of ITO (indium tin oxide) conductive glass. However, when completing experiments with a certain degree of complexity (such as the generation, transportation, mixing, splitting, etc. of droplets), a large number of electrode arrays are required to support it, and the electrode lead problem is a major bottleneck in the preparation of large-scale arrayed electrodes on glass substrates. Another chip substrate prepared based on thin-film transistor (TFT) technology can solve the lead problem of the electrode array, but its price is relatively high and is not suitable for commercialization.

[0004] In addition to the above methods, the chip substrate can also be prepared using a printed circuit board (PCB) process. The PCB process has the advantages of low price, simple preparation, and large-scale use. The mature through-hole manufacturing process and the supporting grid array packaging technology in the PCB process easily solve the lead problem of large-scale array electrodes, but this technology has certain defects in droplet driving. Specifically, since the PCB board is prepared by printing, the chip manufacturing accuracy made by PCB technology is low, and its surface cannot achieve the same smoothness as a glass plane, and the rough surface will bring difficulties to droplet driving. On the one hand, the droplets will be subject to a large friction force from the rough surface during the movement. When the driving force driven by the voltage cannot exceed the friction force, the droplets will be unable to move; on the other hand, if the driving force is increased by increasing the driving voltage, there will be a risk of breakdown, and since most of the liquids involved in the experiment of the on-chip laboratory chip are high-concentration salt solutions, the risk of breakdown is further increased. At the same time, the guide hole 3 on the PCB board that penetrates the electrode 2 and the gap between the electrodes (such as Figure 1) will produce a huge resistance to the movement of droplets, seriously hindering the movement of droplets, so it is necessary to solve the resistance problem from the root. Summary of the invention

[0005] In view of the above analysis, the embodiments of the present invention aim to provide a method for preparing a micro-droplet driving chip and a preparation method thereof, so as to solve the problem that the chips made by PCB technology in the prior art have defects in droplet driving.

[0006] On the one hand, an embodiment of the present invention provides a method for preparing a micro-droplet driving chip, the method comprising:

[0007] A plurality of closely arranged electrodes are prepared on the PCB substrate to form an electrode layer, and each electrode covers a corresponding guide hole on the PCB substrate;

[0008] Fill the guide holes with a filling material, and fill the gaps between the electrodes with an insulating material;

[0009] Polishing the surface of the electrode layer to make the surface of the electrode layer flat and smooth;

[0010] A dielectric layer and a hydrophobic layer are sequentially prepared on the surface of the polished electrode layer to obtain a lower electrode plate of the micro-droplet driving chip.

[0011] Based on the further improvement of the above method, the polishing treatment of the surface of the electrode layer comprises the following steps:

[0012] Preparing a buffer layer with a first preset thickness on the surface of the electrode layer;

[0013] The buffer layer is polished until the electrode layer is exposed and polished away by a second preset thickness.

[0014] Based on the further improvement of the above method, a buffer layer with a preset thickness is prepared on the surface of the electrode layer, including:

[0015] After the electrode layer is coated with a preset thickness of modified epoxy resin glue, the coated modified epoxy resin glue is subjected to high temperature curing treatment to form a buffer layer.

[0016] Based on a further improvement of the above method, under the action of the polishing liquid, the buffer layer is polished by a polishing machine until the electrode layer is exposed and polished away to a second preset thickness.

[0017] Based on the further improvement of the above method, a plurality of closely arranged electrodes are prepared on a PCB substrate to form an electrode layer, comprising the following steps:

[0018] Depositing a metal layer on the PCB substrate;

[0019] Prepare a mask plate, and form a graphic area on the mask plate, wherein the graphic area includes a plurality of closely arranged graphic units, and the shape of the graphic units is the same as the shape of the electrode;

[0020] The metal layer is photoetched using the mask to achieve patterning of the electrode layer, thereby forming a plurality of closely arranged electrodes.

[0021] Based on the further improvement of the above method, the edges on both sides of the electrode in the moving direction of the micro-droplet are both set to be concave-convex shapes.

[0022] Based on a further improvement of the above method, the concave-convex shape includes a sawtooth shape or a corrugated shape.

[0023] Based on a further improvement of the above method, the filling material includes a resin material, and the insulating material includes a solder resist.

[0024] Based on the further improvement of the above method, the method further includes:

[0025] A second hydrophobic layer is prepared on an ITO conductive glass substrate to obtain an upper electrode plate of a micro-droplet driving chip;

[0026] The upper electrode plate and the lower electrode plate are assembled together to obtain a micro-droplet driving chip.

[0027] On the other hand, an embodiment of the present invention provides a micro-droplet driving chip, wherein the micro-droplet driving chip is prepared by the method as described above.

[0028] The micro-droplet driving chip includes an upper electrode plate and a lower electrode plate.

[0029] The lower plate comprises:

[0030] The PCB substrate is provided with a guide hole, and a filling material is provided in the guide hole;

[0031] An electrode layer is prepared on the PCB substrate, wherein the electrode layer comprises a plurality of closely arranged electrodes, each electrode covers a corresponding guide hole on the PCB substrate, and the gaps between the electrodes are filled with insulating material;

[0032] a dielectric layer, coated on the polished electrode layer; and

[0033] The hydrophobic layer is coated on the dielectric layer.

[0034] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0035] 1. In the present invention, when preparing the electrode layer, the electrode covers the guide hole on the PCB substrate, and the guide hole and the gap between the electrodes are filled by filling, respectively, to achieve rough flattening of the surface of the electrode layer, and then further achieve fine flattening of the surface of the electrode layer by polishing, and then sequentially coat the dielectric layer and the hydrophobic layer, thereby finally obtaining a lower electrode plate of a micro-droplet driving chip with a smooth and flat surface, which greatly reduces the resistance of the droplets moving on the chip.

[0036] 2. In the present invention, when polishing the electrode layer, a buffer layer is first prepared on the surface of the electrode layer to increase the thickness, and then the polishing process is started from the surface of the buffer layer, thereby achieving the polishing process of the electrode layer surface with a thickness of micrometer level (less than 1mm).

[0037] 3. In the present invention, the shape of the electrode is improved, and the edges on both sides of the electrode in the direction of movement of the micro-droplet are set to be concave and convex shapes, which can ensure that the droplet is in contact with two adjacent independent electrodes at the same time on its moving path, so that it is easier to drive the droplet when switching the control electrode.

[0038] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0040] Figure 1 It is a schematic diagram of the structure of a micro-droplet driving chip made by PCB technology in the prior art;

[0041] Figure 2 Flow chart of a method for preparing a micro-droplet driving chip according to an embodiment of the present invention;

[0042] Figure 3 This is a diagram of the decomposition steps of preparing the lower electrode plate according to an embodiment of the present invention;

[0043] Figure 4 Schematic diagram of the relative positions of the electrode layer and the guide hole prepared in step 1 of an embodiment of the present invention;

[0044] Figure 5 This is a top view of the prepared lower electrode plate according to an embodiment of the present invention.

[0045] Reference numerals:

[0046] 1. PCB substrate; 2. Electrode; 3. Guide hole; 4. Filling material; 5. Insulation material;

[0047] 6. Dielectric layer; 7. Hydrophobic layer. DETAILED DESCRIPTION

[0048] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0049] A specific embodiment of the present invention provides a method for preparing a micro-droplet driving chip, such as Figure 2 The method comprises:

[0050] Step 1, preparing a plurality of closely arranged electrodes 2 on a PCB substrate 1 to form an electrode layer, and making each electrode 2 cover a corresponding guide hole 3 on the PCB substrate 1;

[0051] Step 2, filling the guide hole 3 with a filling material 4, and filling the gap between the electrodes 2 with an insulating material 5;

[0052] Step 3, polishing the surface of the electrode layer to make the surface of the electrode layer flat and smooth;

[0053] Step 4: on the surface of the polished electrode layer, a dielectric layer 6 and a hydrophobic layer 7 are sequentially prepared to obtain the lower electrode plate of the micro-droplet driving chip.

[0054] During implementation, the PCB substrate 1 is used as the chip substrate, and the electrode layer is first made on the PCB substrate 1, and then the guide hole 3 of the PCB substrate 1 is filled with the filling material 4, and the gap between the electrodes 2 is filled with the insulating material 5 to achieve rough flattening of the surface of the electrode layer. Among them, the guide hole 3 of the PCB substrate 1 is filled with the filling material 4 to achieve the flattening of the surface of the PCB substrate 1, so that the electrode layer can better fit the surface of the PCB substrate 1, which is conducive to the flattening of the surface of the electrode layer. After the rough flattening of the electrode layer is achieved, fine flattening is achieved by polishing, and then the dielectric layer 6 and the hydrophobic layer 7 are coated in sequence, so as to achieve the purpose of using the PCB substrate instead of the glass substrate.

[0055] Compared with the prior art, in the present invention, when preparing the electrode layer, the electrode 2 covers the guide hole 3 on the PCB substrate 1, and the guide hole 3 and the gap between the electrode 2 are filled respectively by filling, thereby achieving rough flattening of the surface of the electrode layer, and then further achieving fine flattening of the surface of the electrode layer by polishing, and then coating the dielectric layer 6 and the hydrophobic layer 7 in sequence, thereby finally obtaining a lower electrode plate of a micro-droplet driving chip with a smooth and flat surface, which greatly reduces the resistance of the droplets moving on the chip.

[0056] In step 1, both side edges of the electrode 2 in the moving direction of the micro-droplet are set to be concave-convex shapes.

[0057] In the present invention, the shape of the electrode 2 is improved, and the edges on both sides of the electrode 2 in the direction of movement of the micro-droplet are set to be concave and convex shapes, which can ensure that the droplet is in contact with two adjacent independent electrodes 2 at the same time on its moving path, so that it is easier to drive the droplet when switching the control electrode 2.

[0058] Specifically, the concavo-convex shape includes a sawtooth shape or a corrugated shape. Figure 4 and Figure 5 FIG. 2 shows an electrode 2 whose edges on both sides in the moving direction of the micro-droplet are corrugated.

[0059] During the operation of the micro-droplet driving chip, the contact angle of the droplet is regulated by adjusting the voltage of the electrode 2, thereby controlling the movement or splitting of the droplet. Figure 4 and 5 The electrode 2 with a concave-convex edge as shown in the figure can make the droplet contact with both independent electrodes 2, and can make the droplet easier to drive when switching the control electrode 2 (if it only contacts a single electrode 2, the droplet cannot be driven). Compared with the electrode 2 with a triangular or other regular shape, the electrode 2 with a concave-convex shape such as a sawtooth or corrugated edge has an interactive part between two adjacent electrodes 2 in the moving direction of the micro-droplet, and the space utilization rate is high. Each protruding part can have an effect on the droplet, and the multi-point force is more efficient than the single-point force, and the driving effect is more obvious.

[0060] More specifically, in step 1, a plurality of closely arranged electrodes 2 are prepared on a PCB substrate 1 to form an electrode layer, comprising the following steps:

[0061] Step 11, depositing a metal layer on the PCB substrate 1; specifically, a magnetron sputtering (PVD) technology can be used to sputter and deposit the metal target material on the PCB board;

[0062] Step 12, preparing a mask plate, forming a graphic area on the mask plate, wherein the graphic area includes a plurality of closely arranged graphic units, and the shape of the graphic unit is the same as the shape of the electrode 2;

[0063] Step 13, using the mask to perform photolithography on the metal layer to achieve patterning of the electrode layer, forming a plurality of electrodes 2 that are closely arranged.

[0064] The shape of the graphic unit is that both side edges in the moving direction of the micro-droplet are concave-convex.

[0065] In step 2, the filling material 4 includes a resin material, such as epoxy resin.

[0066] In the embodiment of the present invention, a resin material is used to fill the guide hole 3 on the PCB substrate 1. During implementation, the resin plugging process uses resin to plug the guide hole 3 (blind hole) and then presses it, which can not only avoid the problem of low fullness caused by material shrinkage and air blowing in the hole caused by green oil (solder resist) plugging, but also balance the contradiction between the thickness control of the pressed dielectric layer 6 and the design of insufficient filling of the inner blind hole.

[0067] In step 2, the insulating material 5 includes a solder resist.

[0068] The solder resist can be used for insulation and to prevent solder from adhering to some copper wires that do not need to be soldered. Specifically, the solder resist can be a liquid photo-imaging solder resist.

[0069] In addition, if solder resist is selected to fill the gaps between the electrodes 2, then in step 1, when a plurality of closely arranged electrodes 2 are prepared on the PCB substrate 1 to form an electrode layer, the gaps between the electrodes 2 are set to 0.23 mm to 0.25 mm.

[0070] Considering the limitation of the printing process, the solder resist can enter only when the gap between the electrodes 2 is greater than or equal to 0.23 mm, so the gap between the electrodes 2 is set to 0.23 mm to 0.25 mm.

[0071] In a specific implementation, compared with the existing design, the gap between the electrodes 2 is enlarged, and the gap between the electrodes 2 can be increased by reducing the size of the electrodes 2.

[0072] In addition, it should be noted that in the PCB process, the solder mask manufacturing process is very rough. When the existing PCB process is used to prepare a micro-droplet driving chip, a solder mask is usually prepared on the surface of the electrode 2. However, the surface roughness of the solder mask is relatively large, and the resistance to the movement of the droplet is very large, requiring a higher voltage for driving. However, excessively high voltage is likely to cause adverse phenomena such as breakdown, affecting the use effect of the device. Therefore, in the embodiment of the present invention, the solder mask on the surface of the electrode layer is cancelled, and only the gap between the electrodes 2 is filled with solder mask.

[0073] After the electrode layer is roughly planarized in step 2, its surface is still relatively rough and cannot achieve the same smoothness as a glass surface. The rough surface will bring difficulties to droplet driving. Therefore, in the embodiment of the present invention, the smoothness of the electrode layer surface is improved through a polishing process.

[0074] Preferably, step 3, polishing the surface of the electrode layer, comprises the following steps:

[0075] Step 31, preparing a buffer layer with a first preset thickness on the surface of the electrode layer; and

[0076] Step 32, polishing the buffer layer until the electrode layer is exposed and polished away by a second preset thickness.

[0077] In the PCB process, the thickness of the metal conductive layer such as the electrode layer is very small, generally 2-4 ounces (1 ounce = 45um). Therefore, due to the thickness limit of the metal layer, it is impossible to directly use a polishing machine to automatically polish the metal layer in the prior art.

[0078] In an embodiment of the present invention, when polishing the electrode layer, a buffer layer is first prepared on the surface of the electrode layer to increase the thickness, and then polishing is performed starting from the surface of the buffer layer, thereby achieving polishing of the surface of the electrode layer with a thickness of micrometer level (less than 1 mm).

[0079] Specifically, a buffer layer of a preset thickness is prepared on the surface of the electrode layer, including: coating the electrode layer with a preset thickness of modified epoxy resin glue, and then subjecting the coated modified epoxy resin glue to high temperature curing treatment to form the buffer layer.

[0080] The modified epoxy resin glue mentioned above refers to an epoxy resin glue with modified hardness. The shear strength of the modified epoxy resin glue is 25-35kg / mm 2 ;Tensile strength 42kg / mm 2 ;Compressive strength 90kg / mm 2 .

[0081] Specifically, the modified epoxy resin adhesive can be coated on the surface of the electrode layer by scraping. When the coated modified epoxy resin adhesive is subjected to high temperature curing treatment, the treatment temperature is set to 110° C. to 120° C., and the treatment time is set to 60 min to 90 min.

[0082] Specifically, the first preset thickness is 10 mm to 12 mm, that is, the thickness of the buffer layer is 10 mm to 12 mm.

[0083] In addition, in step 3, the buffer layer is completely polished away, and only a very small thickness of the electrode layer needs to be polished away to achieve the required smoothness. In practice, the electrode layer is generally polished to a thickness of 50 μm to 100 um. That is, the second preset thickness is 50 μm to 100 um.

[0084] Preferably, under the action of the polishing liquid, the buffer layer is polished by a polishing machine until the electrode layer is exposed and polished away by a second preset thickness.

[0085] Considering that droplet driving has high requirements for surface flatness and smoothness, and mechanical polishing has the problem of poor surface uniformity, the present invention polishes the buffer layer through a polishing machine under the action of polishing liquid, combining the mechanical polishing method with the chemical method to improve the polishing uniformity.

[0086] Specifically, the polishing liquid is a metallographic polishing liquid, and the polishing machine uses a 5000-5500 mesh fine sandpaper for polishing.

[0087] In addition, in the embodiment of the present invention, the polishing thickness is controlled by the polishing time. Specifically, under the action of the metallographic polishing liquid, a fine sandpaper of 5000-5500 mesh is selected to polish the surface of the electrode layer for 10s to 20s.

[0088] In a specific embodiment, before the polishing process, the roughness of the surface of the electrode layer is Ra=3.287; after the polishing process is performed using the above method of the present invention, the roughness of the surface of the electrode layer is Ra=2.036.

[0089] Specifically, in step 4, the material of the dielectric layer 6 is SU-8 (silicon oxide, silicon nitride), and the material of the hydrophobic layer 7 is Teflon.

[0090] The dielectric layer 6 prevents leakage of electricity when the droplet contacts the electrode 2 ; the hydrophobic layer 7 adjusts the contact angle between the droplet and the interface so that the droplet can be driven more easily.

[0091] It should be noted that the dielectric layer 6 and the hydrophobic layer 7 are both thin films that can fit tightly onto the surface of the electrode layer. Therefore, the flatness and smoothness of the surface of the lower electrode plate of the micro-droplet driving chip prepared by the method of the embodiment of the present invention is determined by the surface of the electrode layer.

[0092] The surface roughness of the lower electrode plate prepared by the method of the embodiment of the present invention and the height difference between the filled gap and the surface of the electrode 2 were tested, and it was found that the micro-droplet driving chip using the lower electrode plate met the requirements of being an on-chip laboratory chip in terms of droplet driving.

[0093] In one embodiment, the method further comprises:

[0094] Step 5, preparing a second hydrophobic layer 7 on the ITO conductive glass substrate to obtain an upper electrode plate of the micro-droplet driving chip;

[0095] Step 6, assemble the upper electrode plate and the lower electrode plate together to obtain a micro-droplet driving chip.

[0096] In this embodiment, since the upper electrode plate of the micro-droplet driving chip does not need to prepare a large number of electrodes 2, it can be directly obtained by coating a hydrophobic layer 7 on an ITO conductive glass substrate, and the prepared upper electrode plate and the lower electrode plate are placed opposite each other and assembled together to obtain the micro-droplet driving chip.

[0097] On the other hand, a specific embodiment of the present invention provides a micro-droplet driving chip. The micro-droplet driving chip includes an upper electrode plate and a lower electrode plate. The lower electrode plate includes: a PCB substrate 1, provided with a guide hole 3, and a filling material 4 is provided in the guide hole 3; an electrode layer, prepared on the PCB substrate 1, the electrode layer includes a plurality of closely arranged electrodes 2, each electrode 2 covers the corresponding guide hole 3 on the PCB substrate 1, and the gaps between the electrodes 2 are filled with insulating material, preferably solder resist; a dielectric layer 6, coated on the polished electrode layer; and a hydrophobic layer 7, coated on the dielectric layer 6.

[0098] like Figure 3 As shown in the figure, the lower electrode plate of the micro-droplet driving chip is prepared by the following method: a plurality of closely arranged electrodes 2 are prepared on a PCB substrate 1 to form an electrode layer, and each electrode 2 covers a corresponding guide hole 3 on the PCB substrate 1; the guide holes 3 are filled with a filling material 4, and the gaps between the electrodes 2 are filled with an insulating material, preferably a solder resist; the surface of the electrode layer is polished to make the surface of the electrode layer flat and smooth; a dielectric layer 6 and a hydrophobic layer 7 are sequentially prepared on the surface of the polished electrode layer to obtain the lower electrode plate of the micro-droplet driving chip.

[0099] Preferably, the gap between the electrodes 2 is set to 0.23 mm to 0.25 mm.

[0100] Preferably, both side edges of the electrode 2 in the moving direction of the micro-droplet are configured to be concave-convex shapes.

[0101] The upper electrode plate of the micro-droplet driving chip is prepared by the following method: a second hydrophobic layer 7 is prepared on an ITO conductive glass substrate to obtain the upper electrode plate of the micro-droplet driving chip.

[0102] The micro-droplet driving chip of the embodiment of the present invention is prepared based on the PCB process and uses the PCB substrate 1 as the chip substrate. It can obtain a lower electrode plate of the micro-droplet driving chip with a smooth and flat surface, which greatly reduces the resistance of the droplets moving on the chip. It has low cost and simple processing process, which is conducive to mass production and provides convenience for high-throughput microfluidic control.

[0103] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a micro-droplet driving chip, characterized in that: The method comprises: A plurality of closely arranged electrodes are prepared on the PCB substrate to form an electrode layer, and each electrode covers a corresponding guide hole on the PCB substrate; Fill the guide holes with a filling material, and fill the gaps between the electrodes with an insulating material; Polishing the surface of the electrode layer to make the surface of the electrode layer flat and smooth; A dielectric layer and a hydrophobic layer are sequentially prepared on the surface of the polished electrode layer to obtain a lower electrode plate of the micro-droplet driving chip.

2. The method according to claim 1, characterized in that The polishing process for the surface of the electrode layer comprises the following steps: Preparing a buffer layer with a first preset thickness on the surface of the electrode layer; The buffer layer is polished until the electrode layer is exposed and polished away by a second preset thickness.

3. The method according to claim 2, characterized in that A buffer layer of a preset thickness is prepared on the surface of the electrode layer, comprising: After the electrode layer is coated with a preset thickness of modified epoxy resin glue, the coated modified epoxy resin glue is subjected to high temperature curing treatment to form a buffer layer.

4. The method according to claim 2 or 3, characterized in that: Under the action of the polishing liquid, the buffer layer is polished by a polishing machine until the electrode layer is exposed and polished away by a second preset thickness.

5. The method according to any one of claims 1 to 3, characterized in that: A plurality of closely arranged electrodes are prepared on a PCB substrate to form an electrode layer, comprising the following steps: Depositing a metal layer on the PCB substrate; Prepare a mask plate, and form a graphic area on the mask plate, wherein the graphic area includes a plurality of closely arranged graphic units, and the shape of the graphic units is the same as the shape of the electrode; The metal layer is photoetched using the mask to achieve patterning of the electrode layer, thereby forming a plurality of closely arranged electrodes.

6. The method according to any one of claims 1 to 3, characterized in that The edges of both sides of the electrode in the moving direction of the micro-droplet are both arranged in a concave-convex shape.

7. The method according to claim 6, characterized in that The concavo-convex shape includes a sawtooth shape or a corrugated shape.

8. The method according to any one of claims 1 to 3, characterized in that The filling material includes a resin material, and the insulating material includes a solder resist.

9. The method according to any one of claims 1 to 3, characterized in that: The method further comprises: A second hydrophobic layer is prepared on an ITO conductive glass substrate to obtain an upper electrode plate of a micro-droplet driving chip; The upper electrode plate and the lower electrode plate are assembled together to obtain a micro-droplet driving chip.

10. A micro-droplet driving chip, characterized in that: The micro-droplet driving chip is prepared by the method described in any one of claims 1 to 9. The micro-droplet driving chip includes an upper electrode plate and a lower electrode plate. The lower plate comprises: The PCB substrate is provided with a guide hole, and a filling material is provided in the guide hole; An electrode layer is prepared on the PCB substrate, wherein the electrode layer comprises a plurality of closely arranged electrodes, each electrode covers a corresponding guide hole on the PCB substrate, and the gaps between the electrodes are filled with insulating material; a dielectric layer, coated on the polished electrode layer; and The hydrophobic layer is coated on the dielectric layer.

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