Hydrophobic surface treated droplet pusher and its manufacturing method

Abstract

The present invention relates to a droplet separator, and more specifically, to a droplet separator with a surface treated to be hydrophobic.

Description

Technology Field

[0001] The present invention relates to a droplet separator, and more specifically, to a droplet separator with a surface treated to be hydrophobic. Background Technology

[0002] Superhydrophobicity refers to a case where the contact angle is 150° or greater. Here, the contact angle is the angle measured from the inside of the liquid between the interfaces of a liquid and a gas or between a liquid and a solid. Superhydrophobic surfaces are utilized in various fields, but extensive research has been conducted because ejecting small droplets smaller than a microliter is not easy. This can be understood by considering the situation where microdroplets are ejected using a device such as a nozzle. When a droplet is suspended at the tip of a nozzle, pressure must be applied to eject it; however, for small droplets smaller than a microliter, the volume relative to the surface area in contact with the nozzle is small, so the force acting on the droplet is much greater due to surface tension than gravity. Therefore, to maintain and eject the droplet, pressure greater than the surface tension must be applied, making the design of equipment for controlling such microdroplets complex and difficult to manufacture.

[0003] Early research on droplet ejection was primarily conducted in the late 19th and early 20th centuries using simple tools for sucking in and releasing liquids, such as pipettes, or vibration methods utilizing piezoelectric elements. Currently, research is being conducted on microfluidic devices consisting of fine channels and chambers, as well as inkjet printing using pressure and droplet generation devices. Through these studies, microdroplets are being utilized in many fields, including bio-experiments, inkjet printing, liquid kinetics, and chemical analysis.

[0004] However, with the advancement of cutting-edge technology, micro-scale control has become important, and there is a growing trend of active research on sizes ranging from nanoliters to atholliters and smaller. Most current studies involve large-scale experiments, which have limitations due to complex methods and the use of expensive equipment. Furthermore, there is not much research regarding the generation of microliter-sized droplets, which are the most commonly used in surface wetting studies, such as contact angle measurement, liquid penetration measurement, and wetting rate measurement.

[0005] Sabrina Kartmann's *A low-cost normally closed solenoid valve for non-contact dispensing in the sub-μL range* (2013) is a study on a normally closed solenoid valve for dispensing microliter droplets ranging from 0.16 to 11.4 μL. The solenoid valve utilizes a principle where supplying current to a coil generates a magnetic field, which attracts a plunger inside the valve to open the liquid passage. When the current is cut off, the magnetic field disappears, and the plunger returns to its original position by spring force to close the liquid passage. This allows for a non-contact dispensing method and the control of the liquid volume by adjusting the amount of current. However, solenoid valves are relatively large, making them difficult to use in environments with space constraints. Furthermore, long-term use of the valve can lead to issues such as wear, corrosion, and functional degradation, requiring regular inspections and the replacement of parts.

[0006] In addition, Stefan Bammesberger's *Quantitative characterization of non-contact microdispensing technologies for the sub-microliter range* (2013) is a study that covers a droplet size range of 0.05 to 10 µL in microliters. This paper introduces various non-contact dispensing technologies, specifically focusing on positive displacement-based technology, which involves directly pushing liquid to dispense droplets. Liquid is filled into a reservoir, and a drive mechanism is used to move the liquid from the reservoir into a microchamber. The liquid inside the microchamber is pushed out through a nozzle to form droplets, which are then separated and dispensed from the tip of the nozzle. However, positive displacement-based technology, particularly piezo actuator-based technology, has limitations, such as high manufacturing costs, while micro-pump-based technology involves complex control systems.

[0007] In addition, research on technology capable of separating droplets smaller than the micro scale has been published since 2010. Prior art literature

[0008] A low-cost normally closed, solenokd valve for non-contact dispensing in the sub-μL range, Stefan Borja Bammesberger et al., Micromachines 2013, 4(1), 9-21.Quantitative characterization of non-contact microdispensing technologies for the submicroliter range, Stefan Borja Bammesberger et al., Drug Discov Today. 2013 May;18(9-10):435-46. The problem to be solved

[0009] The objective of the present invention is to provide a simple and efficient method for dispensing microliter-sized droplets using an aluminum specimen (DP; Droplet Pusher) having a hole with a superhydrophobic surface treatment.

[0010] Furthermore, unlike various existing droplet generation studies, the present invention ejects droplets using a physical method. A nozzle is passed through a hole to generate a droplet larger than the hole. Subsequently, when the nozzle is raised, the edge of the hole on the aluminum plate comes into contact with the droplet, generating a physical repulsive force to separate the droplet from the nozzle.

[0012] Furthermore, the technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which the present invention belongs from the description below. means of solving the problem

[0014] To achieve the above objective, a droplet separator according to one embodiment of the present invention comprises a specimen; and a hole having a predetermined diameter within the specimen.

[0015] The above specimen may be treated with a hydrophobic surface, and the surface of the specimen may be coated with HDFS (Heptadecafluoro-1,1,2,2-tetrahydrodecyl trichlorosilane).

[0016] The diameter of the hole may have a size ratio of 47.8 to 88.3% relative to the diameter of the droplet to be produced.

[0017] The contact angle of the above droplet separator with respect to water may be 150° or more.

[0019] In addition, a method for manufacturing a droplet separator according to one embodiment of the present invention includes a cleaning step for removing impurities from the surface of a specimen having a hole having a predetermined diameter; an acid etching step for forming a microstructure on the surface of the specimen after the cleaning step; a surface modification step for forming a nanostructure on the specimen after the acid etching step; and a surface treatment step for treating the surface of the specimen with a hydrophobic coating after the surface modification step.

[0020] The above cleaning step may involve treatment with an alkaline solution.

[0021] The diameter of the hole may have a size ratio of 47.8 to 88.3% relative to the diameter of the droplet to be generated.

[0022] The above surface treatment may be coating the surface of the specimen with HDFS (Heptadecafluoro-1,1,2,2-tetrahydrodecyl trichlorosilane). Effects of the invention

[0023] The present invention has the effect of enabling droplet generation that is easy to manufacture and inexpensive.

[0024] In addition, the present invention has the effect of consistently controlling the size and generation speed of droplets by adjusting the position and movement speed of the nozzle.

[0025] In addition, the present invention has the effect of being suitable for mass production due to its simple structure and manufacturing process.

[0026] In addition, the present invention has the effect of providing favorable conditions for utilizing droplet generation technology in industrial applications. Brief explanation of the drawing

[0027] Figure 1 shows a surface SEM image of a droplet separator according to one embodiment of the present invention. Figure 2 shows SEM images of a droplet separator before and after surface treatment according to one embodiment of the present invention. FIG. 3 illustrates the volume of separated droplets according to the hole diameter of a droplet separator according to one embodiment of the present invention. Figure 4 illustrates the relationship of the force required for droplet separation according to the hole diameter of a droplet separator according to one embodiment of the present invention. Figure 5 illustrates the relationship between a nozzle and a droplet according to one embodiment of the present invention. Figure 6 illustrates the minimum droplet volume at the volume of separated droplets according to the hole diameter of the droplet separator in Figure 3. Specific details for implementing the invention

[0028] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0030] A droplet separator according to one embodiment of the present invention is for separating a droplet (or water droplet) generated through a nozzle from the nozzle, and is intended to provide a droplet having a desired volume (or size).

[0031] A droplet separator according to one embodiment of the present invention comprises a specimen; and a hole having a diameter of a predetermined size within the specimen.

[0032] The above specimen may be a metal, and as an example, may be aluminum.

[0033] The above specimen may have a hydrophobic surface treatment, and the surface of the above specimen may be coated with one or more materials selected from the group consisting of HDFS (Heptadecafluoro-1,1,2,2-tetrahydrodecyl trichlorosilane), PTFE (Polytetrafluoroethylene), PDMS (polydimethylsiloxane), ODTS (n-octadecyltrichlorosilane), and PVDF (Polyvinylidene fluoride).

[0035] The diameter of the hole may have a size ratio of 47.8 to 88.3% relative to the diameter of the droplet to be produced.

[0036] The contact angle of the above droplet separator with respect to water may be 150° or greater, and preferably 161.5°.

[0038] In addition, a method for manufacturing a droplet separator according to one embodiment of the present invention comprises: a cleaning step (S100) for removing an oxide film and impurities from the surface of a specimen having a hole having a predetermined diameter; an acid etching step (S200) for forming a microstructure on the surface of the specimen after the cleaning; a surface modification step (S300) for forming a nanostructure on the specimen after the acid etching; and a surface treatment step (S400) for treating the surface of the specimen with a hydrophobic coating after the surface modification.

[0040] The cleaning step (S100) is for removing oxide films and impurities present on the specimen, and more specifically, the cleaning step (S100) may be performed with an alkaline solution, and the alkaline solution may be selected from the group consisting of sodium hydroxide (NaOH) solution, potassium hydroxide (KOH) solution, calcium hydroxide (Ca(OH)2) solution, copper hydroxide (Cu(OH)2) solution, ammonium hydroxide (NH4OH) solution, and iron hydroxide (Fe(OH)2) solution.

[0041] The above specimen may be a metal, and as an example, may be aluminum.

[0042] The above specimen may include a hole having a predetermined diameter, and the diameter of the hole may have a size ratio of 47.8 to 88.3% relative to the diameter of the droplet to be produced.

[0043] The acid etching step (S200) is for forming a microstructure of 1 to 20 μm on the surface of the specimen, and the acid etching may use a hydrochloric acid (HCl) solution, a hydrofluoric acid (HF) solution, a phosphoric acid (H3PO4) solution, a sulfuric acid (H2SO4) solution, a nitric acid (HNO3) solution, or an acetic acid (CH3COOH) solution.

[0044] The surface modification step (S300) is to perform physical surface modification on the specimen after the acid etching step (S200) to form a nanostructure, and more specifically, the surface modification step (S300) may be treated with an alkali solution, and the alkali solution may be selected from the group consisting of sodium hydroxide (NaOH) solution, potassium hydroxide (KOH) solution, calcium hydroxide (Ca(OH)2) solution, copper hydroxide (Cu(OH)2) solution, ammonium hydroxide (NH4OH) solution, and iron hydroxide (Fe(OH)2) solution.

[0045] The surface modification step (S300) may further include a process of drying the specimen after treatment with the alkaline solution, and more specifically, may involve immersing the specimen in a high-temperature aqueous solution after treatment with the alkaline solution and then drying it.

[0046] The surface treatment step (S400) is intended to impart hydrophobicity to the specimen after the surface modification step (S300), and may involve coating the surface of the specimen with HDFS (Heptadecafluoro-1,1,2,2-tetrahydrodecyl trichlorosilane). More specifically, the coating may be performed using a mixed solution of HDFS and an organic solvent, wherein the organic solvent may be n-hexane, xylene, toluene, or ethyl alcohol. The mixed solution may be a mixture of the HSDF and the organic solvent in a volume ratio of at least 10,000:1 (v:v).

[0048] The following describes the invention in detail through examples. Examples and the like are intended to aid in understanding the invention and do not limit the technical scope of the invention with respect to the contents described in the examples and the like; rather, the scope of the rights of the invention extends to substantially the same scope as the invention.

[0050] Preparation

[0051] As a nozzle for discharging droplets, a droplet injection needle (nozzle) made of stainless steel with an outer diameter of 780 μm, an inner diameter of 500 μm, and a length of 25 mm was prepared.

[0052] A stand with dimensions of 116 mm in width, 30 mm in length, and 17 mm in height was fabricated using a 3D printer (Makerbot, USA) so that an aluminum specimen, which is a droplet separator (DP), could be mounted at a certain height.

[0053] For the superhydrophobic surface treatment, Acetone (99.5%), NaOH (98%), HCl (36.46%), and n-Hexane (95.0%) were purchased from Samjin Chemical in South Korea, and Heptadecafluoro-1,1,2,2-tetrahydrodecyl trichlorosilane (95%) (HDFS; JSIsilicone, South Korea) was purchased.

[0054] Before the experiment, the surfaces of the beaker, bar magnet, and rod used in the experiment were all cleaned using acetone (99.5%) at room temperature.

[0056] Preparation Example. Fabrication of a Droplet Separator (DP)

[0057] To manufacture a droplet separator (DP), a disc-shaped aluminum specimen measuring 9.9 mm in width, 14.0 mm in length, and 1 mm in height was prepared by mechanically drilling holes with diameters of 0.85 mm (Preparation Example 1), 1 mm (Preparation Example 2), 1.5 mm (Preparation Example 3), 2 mm (Preparation Example 4), and 2.5 mm (Preparation Example 5), respectively.

[0059] Example. Surface treatment of a droplet separator (DP).

[0060] After preparing a 1 M (mol / L) NaOH solution by mixing 8 g of NaOH and 200 ml of water using a stirrer for at least 15 minutes, each aluminum specimen prepared in the above preparation examples (Preparation Examples 1 to 5) was immersed in the solution for 1 minute to perform surface cleaning to remove oxide films and impurities.

[0061] Afterwards, the surface of the aluminum specimen is cleaned with DI water at room temperature, and an HCl 3 M (mol / L) solution is prepared by mixing 53 ml of HCl (36.46%) and 200 ml of water, and the aluminum specimen is immersed in the solution for 10 minutes to perform acid etching.

[0062] After etching, the aluminum surface is washed with DI water and immersed in a 1 M (mol / L) NaOH solution for 10 seconds to form a surface structure and perform physical surface modification, after which the aluminum specimen is immersed in boiling DI water at 90°C or higher for 5 minutes using an induction method.

[0063] Afterwards, the aluminum specimen is dried in an oven at 50°C for at least 30 minutes.

[0064] Finally, HDFS coating is performed for hydrophobic coating treatment. Surface-treated aluminum specimens (Examples 1 to 5) were prepared by immersing them in a solution mixed with 150 mL of n-Hexane and 150 µL of HDFS (1000:1 (v:v) ratio) for 20 minutes to complete the surface treatment.

[0066] The diameters of the aluminum specimens prepared in the above-described manufacturing examples and embodiments are summarized in Table 1 below.

[0067] Hole diameter Before surface treatment After surface treatment 0.85 mm Preparation Example 1 Example 1 1 mm Preparation Example 2 Example 2 1.5 mm Preparation Example 3 Example 3 2 mm Preparation Example 4 Example 4 2.5 mm Preparation Example 5 Example 5

[0069] Analysis Example 1. Surface Observation

[0070] The surface of the surface-treated aluminum specimen (droplet separator) prepared in the above example was analyzed using a scanning electron microscope (SEM, JEOL, Japan) to obtain SEM images. Additionally, SEM images were analyzed for an aluminum specimen (Bare) that did not form holes and did not undergo surface treatment as a control, and these results are shown in Fig. 1. In Fig. 1, the control aluminum specimen is labeled "Bare," the aluminum specimen according to Example 1 is labeled "0.85 mm," the aluminum specimen according to Example 2 is labeled "1.00 mm," the aluminum specimen according to Example 3 is labeled "1.50 mm," the aluminum specimen according to Example 4 is labeled "2.00 mm," and the aluminum specimen according to Example 5 is labeled "2.50 mm."

[0071] Referring to FIG. 1, the control aluminum specimen ("Bare") has a large amount of impurities on its surface and shows an irregular shape, whereas the aluminum specimens surface-treated with microhydrophobicity in Examples 1 to 5 show a regular shape.

[0072] More specifically, when acid etching is performed in an HCl solution in the example, a microstructure of 1 to 20 μm is formed on the surface of the aluminum specimen, and a nanostructure is formed on the surface by immersing the aluminum specimen in DI water at 90°C or higher. As a result, it can be confirmed that nano-sized roughness is well formed on the microstructure through the SEM image magnified 30kx in Fig. 1 (bottom image in Fig. 1).

[0074] Meanwhile, the surface of the droplet separator (DP) in the example before and after surface treatment was observed and is shown in FIG. 2.

[0075] Referring to Figure 2, it can be seen that no specific pattern is observed in the droplet separator before surface treatment. However, in the case after surface treatment, it can be seen that a pattern of roughness at the micro / nano level is well formed.

[0077] Analysis Example 2. Water Repellency Evaluation

[0078] For the surface-treated aluminum specimens (droplet separators; Examples 1 to 5) prepared in the above examples, the contact angles at five different points were measured using a contact angle measuring instrument (Smart Drop, FemtoFAB, Korea) and the average value was derived.

[0079] In the examples, when the HDFS coating is applied, the structure of the aluminum surface does not change, but its properties change from extremely hydrophilic to extremely hydrophobic. Accordingly, the average contact angle measured at five different points for five surface-treated aluminum specimens (droplet separators; Examples 1 to 5) was confirmed to be 161.5°, while the contact angle of the control aluminum specimen ("Bare") prepared in Analysis Example 1 was confirmed to be 74.4°. Accordingly, it can be confirmed that the surface of the aluminum specimen (droplet separator) is extremely hydrophobic through the surface treatment in the examples.

[0081] Measurement Example 1. Droplet Dispensing Methods

[0082] In the preparation example, the hole of the stand fabricated using a 3D printer and the hole of the hydrophobic surface-treated aluminum specimen (droplet separator; Examples 1 to 5) manufactured in the examples were positioned to form concentric circles and fixed together. Additionally, a contact angle measuring device was fixed to the stand, and the droplet injection needle (nozzle) from the preparation example was positioned to pass through the center of the hole of the aluminum specimen. The contact angle measuring device was adjusted to create a desired droplet volume, and the droplet separator was raised upward at a speed of 1.096 cm per second to separate the droplet suspended from the nozzle.

[0083] After supplying water to the nozzle, if the aluminum specimen successfully pushes out the droplet (water drop) and detaches it from the nozzle, it is considered a success, and if the droplet is sucked into the hole of the aluminum specimen, it is considered a failure. Three cycles were measured, with 10 measurements per aluminum specimen (based on one cycle), and four sets of aluminum specimens (Examples 1 to 5) were prepared for each hole size, for a total of 600 measurements.

[0085] Experimental Example 1. Droplet size according to hole diameter of a droplet separator (DP)

[0086] Through the droplet formation method in Measurement Example 1, the size of the droplets generated and separated from the nozzle according to the hole diameter of the surface-treated aluminum specimens (droplet separators; Examples 1 to 5) manufactured in the examples was analyzed.

[0087] In the example, when the hole diameter of the surface-treated aluminum specimen is 0.85 mm (Example 1), the droplet size is 2.97 ± 0.41 µL; when the hole diameter is 1.00 mm (Example 2), the droplet size is 3.27 ± 0.32 µL; when the hole diameter is 1.50 mm (Example 3), the droplet size is 5.17 ± 0.38 µL; when the hole diameter is 2.00 mm (Example 4), the droplet size is 8.38 ± 0.25 µL; and when the hole diameter is 2.50 mm (Example 5), the droplet size is 11.9 ± 0.52 µL.

[0088] To analyze the relationship between the measured data values ​​of the critical minimum droplet size that can be separated according to the hole diameter of the droplet separator (DP), the x-axis was set as the diameter of the droplet separator hole and the y-axis as the volume of the critical minimum droplet obtained in the experiment described above. The measured droplet volume values ​​are shown in Figure 3, and the average value was displayed after a total of four measurements. When a first-order trend line was applied based on the experimental values, the average error rate was 4.33% and the maximum error rate was 7.19%, indicating that the trend line was reliable.

[0089] Thus, the required hole diameter of the droplet separator can be predicted according to the size of the droplet to be generated, and when the diameter of the first droplet that can be generated is 'a' and the hole diameter of the droplet separator is 'b', the ratio (Y) of the hole diameter of the droplet separator to the diameter of the droplet can be expressed by the following Equation 1.

[0090] [Equation 1]

[0091]

[0092] Y in Equation 1 is 47.8% in Example 1 (diameter 0.85 mm), 54.4% in Example 2 (diameter 1.00 mm), 70.0% in Example 3 (diameter 1.50 mm), 79.4% in Example 4 (diameter 2.00 mm), and 88.3% in Example 5 (diameter 2.50 mm), and it can be confirmed that as the diameter of the droplet separator hole increases, the diameter of the droplet separator hole increases relative to the diameter of the minimum droplet that can be generated.

[0094] Experimental Example 2. Calculation of Critical Force and Critical Angle

[0095] Through the droplet formation method of Measurement Example 1, the critical point volume at which a droplet (outer diameter: 780 μm) of the preparation example can be suspended from the nozzle without external force is 13.50 μl. At this time, the critical point volume is converted into force and is as shown in Equation 2 below.

[0096] [Equation 2]

[0097]

[0098] In Equation 2, the density of water was converted to 1 g / ml.

[0099] In addition, the critical angle between the nozzle and the droplet at the critical point is calculated as Equation 3 below.

[0100] [Equation 3]

[0101]

[0102] That is, if the droplet receives a downward force of 0.1324 mN or more, or if the angle between the nozzle and the droplet becomes smaller than 47.96°, the droplet will fall away from the nozzle.

[0104] Figure 4 illustrates the relationship between the force with which a droplet separator pushes a droplet according to the diameter of the droplet separator. Referring to Figure 4, the contact area between the droplet and the droplet separator is minimized through a superhydrophobic surface treatment, so the frictional force is negligibly small compared to surface tension and gravity, and the force with which the droplet separator pushes a droplet can be calculated simply by using the difference between the normal force of surface tension and gravity as shown in Equation 4 below.

[0105] [Equation 4]

[0106] Push Force [mN] =

[0108] In Equation 4, r is the radius of the nozzle's outer diameter, and the value of θ represents the angle between the droplet suspended on the nozzle and the nozzle, as shown in Fig. 5.

[0109] As a result of calculations according to Equation 4, as shown in Fig. 3, the droplet separator hole diameter was calculated to be 0.1440 mN at 0.85 mm (Example 1), 0.1395 mN at 1.00 mm (Example 2), 0.1163 mN at 1.50 mm (Example 3), 0.0815 mN at 2.00 mm (Example 4), and 0.0433 mN at 2.50 mm (Example 5). Through this, it can be confirmed that the force of the droplet separator pushing out droplets increases as the hole diameter of the droplet separator decreases. This confirms that it is advantageous for the use of DP.

[0111] Experimental Example 3. Controllable range of droplets in a droplet separator

[0112] In order to examine the range in which the droplet separator can control the droplets, the critical point volume was measured in Experimental Example 2. It was measured to be 13.5 μL based on a nozzle of 0.78 mm, which means that this is the limit point at which the droplet separator can control the droplets.

[0113] Through this, as shown in Figure 6, in the graph of the critical minimum droplet separable by hole diameter of the droplet separator, it can be confirmed that droplet control is possible through the droplet separator in the area located above the trend line graph and the area located below the point of 13.50 µl within the experimental range. On the other hand, in the area located below the trend line, droplets are sucked into the holes of the droplet separator, making droplet control impossible, and in the area located above the point of 13.5 µl, droplets naturally fall out because they are too heavy. The droplet controllable range of the droplet separator used in the experiment is as shown in Table 2 below, and the final droplet range obtained through the experiment is from 2.7 µl to 13.5 µl.

[0114] Hole diameter of DP Droplet range 0.85 mm (Example 1) 2.70μL ~ 13.50μL 1.00mm (Example 2) 2.95μL ~ 13.50μL 1.50 mm (Example 3) 4.97μL ~ 13.50μL 2.00mm (Example 4) 8.20μL ~ 13.50μL 2.50 mm (Example 5) 11.50μL ~ 13.50μL

[0115] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

Claims

Claim 1 A droplet separator comprising a specimen; and a hole having a predetermined diameter within the specimen. Claim 2 In claim 1, the above specimen is a droplet separator with a surface treated to be hydrophobic. Claim 3 A droplet separator according to paragraph 2, wherein the surface of the specimen is coated with HDFS (Heptadecafluoro-1,1,2,2-tetrahydrodecyl trichlorosilane). Claim 4 A droplet separator according to claim 1, wherein the diameter of the hole has a size ratio of 47.8 to 88.3% relative to the diameter of the droplet to be generated. Claim 5 A droplet separator according to claim 1, wherein the contact angle of the droplet separator with water is 150° or more. Claim 6 A method for manufacturing a droplet separator, comprising: a cleaning step for removing impurities from the surface of a specimen having a hole having a predetermined diameter; an acid etching step for forming a microstructure on the surface of the specimen after the cleaning; a surface modification step for forming a nanostructure on the specimen after the acid etching; and a surface treatment step for treating the surface of the specimen with a hydrophobic coating after the surface modification. Claim 7 A method for manufacturing a droplet separator according to claim 6, wherein the cleaning step is treated with an alkaline solution. Claim 8 A method for manufacturing a droplet separator according to claim 6, wherein the diameter of the hole has a size ratio of 47.8 to 88.3% relative to the diameter of the droplet to be generated. Claim 9 A method for manufacturing a droplet separator according to claim 6, wherein the surface treatment is coating the surface of the specimen with HDFS (Heptadecafluoro-1,1,2,2-tetrahydrodecyl trichlorosilane).

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