Polytype quantum dot microarray based on DNA origami self-assembly and preparation method thereof

Abstract

The invention discloses a multi-type quantum dot microarray based on DNA origami self-assembly and a preparation method thereof, and relates to the technical field of nanometers.The preparation method comprises the steps that firstly, a specific microarray pattern designed in advance is etched on a substrate through a nanosphere etching technology and hydrophilized, then DNA origami is connected to the hydrophilic microarray substrate, and the multi-type quantum dot microarray is obtained; and finally, combining the quantum dots with different sizes and types after single-stranded DNA functionalization on the DNA origami, and realizing high-precision self-assembly positioning of the quantum dots by utilizing DNA base complementary pairing, so as to obtain the multi-type quantum dot microarray. The method has the advantages of being programmable, high in resolution, relatively low in cost and the like, nanoscale positioning of the quantum dots can be achieved, the method is suitable for the directions of the quantum information technology, nanometer photoelectric device manufacturing, biological sensing and the like, and a certain application basis is provided for industrial large-scale preparation of quantum devices.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterials, and particularly relates to a multi-type quantum dot microarray based on DNA origami self-assembly and a preparation method thereof. BACKGROUND

[0002] DNA origami technology is a high-precision and low-cost self-assembly technology. By designing complementary base sequences, using the self-recognition ability of bases, folding the relatively planar DNA molecular structure in the traditional sense into a relatively three-dimensional patterned structure according to the base complementarity principle, various patterns can be formed in the microscopic space, and various material modifications and connections can be realized on the surface or inside of the three-dimensional structure, such as multi-type quantum dots after DNA functionalization, and then the nanoscale addressing of DNA modified quantum dots is realized. In recent years, the combination of DNA origami technology and micro-nano processing technology has shown unique potential in the field of nanoscience. The precise molecular addressing ability of DNA origami technology and the physical template manufactured by micro-nano processing technology can complement each other to realize the cooperative construction of functional DNA microarrays. Broadly speaking, micro-nano processing technology includes micro-machining technology, micro-electrical machining technology and nano-machining technology, and here mainly refers to photolithography and nanosphere etching technology. Traditional photolithography technology can realize nanoscale precision and accuracy pattern size positioning on the substrate through the cooperation of mask and ultraviolet light source, and therefore has important breakthroughs in precise positioning and functional integration with DNA origami microarrays. For example, in 2023, the Tim Liedl team of Munich University installed three-dimensional DNA origami on a nanometer patterned substrate after photolithography, and combined gold nanoparticles on the DNA origami to form stable gold particle, dimer and trimer arrays. The optical response of this multi-particle array can be adjusted by the polarization of incident light and scattered light. This method has the potential to expand to various optical applications that rely on complex surface patterns, such as waveguides and optical circuits assembled by colloidal particles. In addition, in 2025, the Oleg Gang team of Columbia University selectively grew three-dimensional DNA origami frames on a gold microarray after photolithography, and for the first time realized the autonomous construction of three-dimensional nanoelectronic devices.

[0003] Compared with lithography technology, nanosphere lithography is a scalable micro-nano processing technology for preparing uniform substrates with low cost, which belongs to a kind of self-assembly technology. It uses single or multi-layer nanospheres (such as polystyrene microspheres (PS spheres), SiO2 microspheres) as a mask, and then leaves a dense and ordered micro-nano array of pits / holes / protrusions on the substrate through a series of physical and chemical reactions, providing physical support for uniform DNA microarray, and the substrate can be modified on the surface to further enrich the surface function. In 2021, Rishabh M. Shetty et al. realized the high-yield and ordered site placement of PS sphere nanolithography and DNA origami microarray. Therefore, using nanosphere lithography to prepare uniform microarray substrates and connecting DNA origami to form DNA origami microarray, and then accurately anchoring DNA functionalized quantum dots can realize low-cost, high-precision, and high-uniformity quantum dot microarray, and broaden the variety and functional diversity of quantum dot microarray preparation.

[0004] Connecting DNA origami with various types and sizes of quantum dots functionalized by DNA on the microarray substrate after nanosphere lithography can manufacture multi-type quantum dot microarrays. Through precise and controllable spatial arrangement and high integration design, it breaks the limitations of traditional quantum dot dispersed applications, makes up for the high cost and low technical complexity advantages that traditional lithography technology does not have, and is expected to improve the signal sensitivity and multi-site synchronous detection efficiency of large-scale integrated devices of optoelectronic devices and biological sensors.

[0005] Quantum dots can emit light with high color purity and good stability at a specific wavelength under light excitation, and the emission range can be expanded to full spectrum by adjusting the size. In addition, due to the rich size diversity, it has expanded many functional applications. For example, spherical quantum dots can be used in display technology, biological imaging, and optoelectronic device field due to their good monodispersity and high luminescence purity; anisotropic quantum rods have applications in polarized light sources, photodetectors, and holographic displays due to their significant tunable luminescence polarization characteristics; core-shell quantum dots have the advantages of few surface defects, high fluorescence quantum yield (>90%), resistance to photobleaching, and strong environmental stability, which can be applied to single-photon source quantum communication, environmental monitoring, and fluorescence enhancement technology. In order to further strengthen the functional application of quantum dots, the concept of "quantum dot microarray" has been proposed, which is to arrange a large number of quantum dots according to a certain rule to form an ordered organization. This large-scale order is conducive to the manifestation of the collective effect of quantum dots, such as super-high-resolution display and quantum dot parallel computing. Currently, there are three methods to prepare quantum dot microarrays: chemical synthesis, epitaxial growth, and self-assembly technology. Chemical synthesis has low cost but lacks accuracy; epitaxial growth has the advantages of high integration and few surface defects, but is high in cost, low in yield, and time-consuming. SUMMARY

[0006] The present application aims at the problems of the prior art, such as the lack of site precision control in the preparation of quantum dot microarray, high cost of quantum dot microarray preparation, and the diversity and type compatibility of quantum dots in the quantum dot microarray, and proposes a multi-type quantum dot microarray based on DNA origami self-assembly and a preparation method thereof.

[0007] The purpose of the present application is achieved by the following technical solutions:

[0008] A multi-type quantum dot microarray based on DNA origami self-assembly, comprising: a microarray substrate and an arrayed arrangement of DNA origami-quantum dot units.

[0009] The surface of the microarray substrate has a plurality of hydrophilic arranged points, and the DNA origami with hydroxyl groups is connected to the points to form a DNA origami microarray, and the quantum dot capture chain is led out from the surface of the DNA origami.

[0010] The quantum dots are modified by a plurality of mercapto single-stranded DNAs to form a plurality of quantum dots with different types of capture chains, and are connected to the DNA origami according to the base complementary pairing principle.

[0011] Further, the microarray substrate is subjected to periodic patterning treatment by nanosphere etching technology, with a period of 100-1000 nm and a period number of 100-10000 orders of magnitude, arranged in one of a hexagonal array, a rectangular array, a triangular array or a rhombic array.

[0012] Further, the microarray substrate is a semiconductor or an oxide.

[0013] Further, the DNA origami is folded by a long DNA single strand and a plurality of short DNA single strands in a proper Mg 2+ Concentration environment through the base complementary pairing principle; its shape is one of quadrilateral, triangle, hexagon, octagon or circle; the size of the DNA origami is between 50-300 nm.

[0014] Further, the quantum dots are single quantum dots and / or DNA self-assembled quantum dot multimers.

[0015] Further, the shape of the quantum dots is one of spherical, rod-shaped, core-shell, tetrahedral, cubic, disc-shaped structure, which together with the DNA origami forms a DNA origami-quantum dot unit.

[0016] A preparation method of a multi-type quantum dot microarray based on DNA origami self-assembly, comprising the following steps:

[0017] S1. mixing long DNA main chain, short DNA staple chain and various quantum dot capture chains in a molar ratio, heating and keeping in a polymerase chain nucleic acid amplifier for a period of time and annealing, and then purifying to obtain a DNA origami structure;

[0018] S2. adding various thiolated single-stranded DNA matching and complementary to the various quantum dot capture chains in step S1 as captured chains into a quantum dot solution containing a certain concentration of sodium chloride to modify the quantum dots, ultrasonicating and adding 1-butanol, centrifuging to remove supernatant and then performing electroelution, so that various quantum dots are filled with corresponding various captured chains on the surface;

[0019] S3. using a semiconductor or oxide substrate, cleaning the surface by using oxygen plasma treatment to generate hydroxyl groups, then dropping nanoballs to form a uniform hexagonal close-packed structure and hydrophobize the surface of the substrate, removing the nanoball mask layer by water bath ultrasonicating, blowing dry with nitrogen and heating the substrate to obtain hydrophilic circular microarray sites;

[0020] S4. dropping a certain concentration of DNA origami solution on the etched hydrophilic microarray sites, incubating for 1 hour, and then washing with buffer multiple times to obtain a DNA origami microarray;

[0021] S5. dropping a proper amount of various quantum dots functionalized with DNA on the surface of the DNA origami microarray in sequence, adding buffer, incubating for 4 hours in a constant temperature and humidity environment, then washing with deionized water and drying, so that arrayed DNA origami-quantum dot composite structure units are formed on the surface of the substrate, and a multiple quantum dot microarray is obtained.

[0022] Further, in the S1, the long DNA main chain, the short DNA staple chain and the various quantum dot capture chains are mixed in a molar ratio of 1:15-25:15-25.

[0023] Further, in the S3, when the surface of the substrate is hydrophobically treated, hexamethyldisilazane liquid (HMDS) is used to treat the surface to add a hydrophobic trimethylsilyl group (TMS) on the surface of the substrate.

[0024] The present application has the following beneficial effects:

[0025] (1) The present application can realize nanoscale precision quantum dot microarray site control, improve controllability, and enhance the directionality and intensity of quantum dot luminescence;

[0026] (2) The arrayed pattern is manufactured by nanoball etching, which has the advantages of relatively low cost and high uniformity of the array, and has certain commercialization potential;

[0027] (3) According to the principle of DNA origami technology and DNA modified quantum dots, the quantum dot capture chain on the DNA origami and the DNA primer of the modified quantum dot can be customized to make them base complementary, so as to improve the size diversity and type compatibility of the quantum dots in the quantum dot array, and to realize the anchoring of multiple quantum dots, thereby enriching the functional application of the quantum dots. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 A schematic diagram of a "DNA origami-quantum dot" composite structure unit provided for an embodiment of the present application is shown in the figure.

[0029] Figure 2 A flowchart of a process for realizing a DNA origami microarray by using polystyrene nanoballs to etch a substrate and performing surface modification engineering is shown in the figure.

[0030] Figure 3 A step flowchart of a method for preparing a multi-type quantum dot microarray based on DNA origami self-assembly is shown in the figure. DETAILED DESCRIPTION

[0031] The technical solutions of the present application will be described below in conjunction with embodiments, and obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0032] Embodiment 1

[0033] A multi-type quantum dot microarray based on DNA origami self-assembly is provided, and the overall structure includes two parts: a microarray substrate and an arrayed arrangement of DNA origami-quantum dot units, wherein the array substrate is a semiconductor or an oxide.

[0034] The microarray substrate is subjected to periodic patterning treatment by nanoball etching technology, with a period of 100-1000 nm, a period number of 100-10000 orders of magnitude, and arranged in one of a hexagonal array, a rectangular array, a triangular array, and a rhombic array.

[0035] The DNA origami is formed by folding a long DNA single strand (such as a M13mp18 bacteriophage DNA single strand, referred to as a main chain) and a plurality of short DNA single strands (referred to as staple chains) through base complementary pairing principles in a proper Mg 2+ The concentration environment; its shape is any one of a quadrilateral, a triangle, a hexagon, an octagon, or a circle; and the size of the DNA origami is in the range of 50-300 nm.

[0036] Quantum dots are one of the following shapes: spherical, rod, core-shell, tetrahedron, cube or disc structure, which together with DNA origami form a DNA origami-quantum dot unit.

[0037] Referring to Figure 3 , a preparation method of a multi-type quantum dot microarray based on DNA origami self-assembly is provided, comprising the following steps:

[0038] Step one: design DNA origami to ensure a reasonable spatial configuration, and extend a type of DNA single strand on its surface for capturing one or more quantum dots, referred to as a capture chain;

[0039] Step two: modify various sizes and types of quantum dots with another type of single-stranded DNA (referred to as a captured chain) that is complementary to the bases of the multiple capture chains, so that the surfaces of various sizes and types of quantum dots are filled with a large number of captured chains that are complementary to the bases of the multiple capture chains extended by the DNA origami. Each size and type of quantum dot corresponds to a unique capture chain and captured chain, so that it can be successfully captured by the DNA origami point by point;

[0040] Step three: the substrate surface is patterned by nanosphere etching technology, oxygen plasma cleaning and hydrophilic surface engineering processes to form a hydrophilic array of point sites;

[0041] Step four: Mg 2+ as a bridge connecting DNA origami with hydroxyl groups and hydrophilic microarrays, combines the DNA origami and the hydrophilic surface of the microarray, and guides the formation of a DNA origami array;

[0042] Step five: various quantum dots functionalized by the captured chain are limited on the surface of the corresponding DNA origami by the principle of base complementary pairing, and each DNA origami and multiple quantum dots of different sizes and types together form a unit, and a large number of ordered DNA origami-quantum dot macroscopically form a microarray, which contains DNA origami and quantum dots of various sizes and types.

[0043] More specifically, the preparation method is as follows:

[0044] S1. Mix the long sequence DNA backbone (such as M13mp18 bacteriophage DNA single strand) with the short sequence DNA single strand (staple chain) and multiple quantum dot capture chains at a molar ratio of 1:15-25:15-25, heat to 80-94℃ in a polymerase chain nucleic acid amplifier, maintain for 5-10 minutes, then anneal from 75℃ to 25-30℃, after the program ends, purify it by agarose gel electrophoresis or ultrafiltration, and the buffer is 0.5×TAE-Mg 2+ ;

[0045] S2. Various quantum dots (such as CuInGaS / ZnS, CdSe / ZnS) are modified with various thiolated single-stranded DNA (such as T12, CT-10, etc.) that are complementary to the corresponding capture strand, ligand exchange is performed to cover the surface of the quantum dots with the capture strand. The modification method of various quantum dots and the corresponding capture strand is similar. First, a certain capture strand and corresponding quantum dots are added to a certain concentration of NaCl solution, ultrasonic treatment is performed until an emulsion is formed, then a certain amount of 1-butanol is added, and the quantum dot DNA is fully contacted by shaking for a few seconds. Centrifugation is performed to separate the liquid phase, the supernatant is removed, then a certain amount of 0.5xTBE is added to resuspend the precipitated solid solution, and the method of agarose gel electrophoresis is used for electric elution to remove the excess capture strand, thereby obtaining the pure DNA functionalized quantum dots;

[0046] S3. An oxide substrate (such as SiO2) is used, first the surface is cleaned by oxygen plasma to remove surface impurities and generate a large number of hydroxyl groups, then a certain amount of nanoballs (such as polystyrene microspheres) with a diameter of 500 nm are dropped to uniformly deposit and cover the surface of the substrate, forming a hexagonal close-packed single / multilayer nanoball, the part of the nanoball bottom that intersects with the substrate surface will retain the hydrophilic hydroxyl group. Then the substrate is placed in a vacuum dryer and HMDS solution is added, sealed and reacted for a certain time, HMDS will evaporate and diffuse onto the substrate to react with the hydroxyl group to form a TMS layer with hydrophobicity, while the circular part covered by the nanoball bottom in contact with the substrate will not be affected. Then water bath ultrasonic cleaning is performed to remove the nanoball mask layer, and the surface is dried with nitrogen, and heated at 120°C to stabilize the TMS hydrophobic layer, thereby forming a regular nanoball mask shielding part of the hydrophilic substrate and the surrounding hydrophobic edge region;

[0047] S4. The DNA origami solution is dropped on the etched circular microarray, incubated in a humid container for one hour, so that the DNA origami is adsorbed on the hydrophilic site, then a buffer solution mixed with 0.07% Tween-20, Tris-HCl, MgCl2 is used for multiple washing to remove the excess DNA origami that is non-specifically bound in the hydrophobic region and competes for the same site in the hydrophilic region;

[0048] S5. A certain amount of DNA modified quantum dot solution is sequentially added to the surface of the DNA origami microarray, and a certain amount of Tris-HCl buffer solution containing Mg 2+ is added, incubated at a constant temperature and humidity for 4 hours, so that the capture strand and the complementary base in the captured strand are fully matched and connected, then the surface of the substrate is gently washed with deionized water for 3 times, and dried with nitrogen, finally forming an ordered microarray composed of "DNA origami-quantum dot" composite structure units.

[0049] Example 2

[0050] AsFigure 1 As shown, Figure 1 The basic structure of the quantum dot microarray prepared by the present application is shown. In this embodiment, square DNA origami with a side length of about 90x90nm is used, and a capture chain is introduced on the surface to fix quantum dots. The three types of quantum dots captured are CdSe spherical quantum dots, CdSe / CdS quantum rods, and AgInS2 / ZnS core-shell quantum dots.

[0051] The preparation method of the quantum dot microarray of this embodiment includes the following steps:

[0052] S1. Mix the M13mp18 bacteriophage DNA backbone with the custom-made staple chain, three types of quantum dot capture chains at a molar ratio of 1:20:20:20:20, heat to 94℃ in a polymerase chain nucleic acid amplifier for 10 minutes, then anneal from 93℃ to 25℃, and after the program ends, purify it by agarose gel electrophoresis or ultrafiltration method, and the buffer is 0.5xTAE-Mg 2+ ;

[0053] S2. Simultaneously modify the CdSe spherical quantum dots, CdSe / CdS quantum rods and AgInS2 / ZnS core-shell quantum dots with thiolated single-stranded DNA T12, CT-10 and C16 respectively, and perform surface ligand exchange to cover the surface with capture chains. The modification of the three types of quantum dots is carried out by the following steps respectively. Take the modification of CdSe spherical quantum dots with T12 as an example: first, add a certain amount of T12 capture chain and CdSe spherical quantum dots to 0.1mol / L NaCl solution, ultrasonic until emulsion is formed, then add appropriate amount of 1-butanol, shake for a few seconds to make the quantum dot DNA fully contact. Centrifugation makes the liquid phase stratified, remove the supernatant, then add appropriate amount of 0.5xTBE to resuspend the precipitated solid solution, and use agarose gel electrophoresis method for electric elution to remove excess capture chains. The modification of CT-10 and C16 repeats the above steps, and thus three types of purified DNA functionalized quantum dots are obtained;

[0054] S3. Figure 2The process of using PS ball to etch the substrate and connect DNA origami is shown. Using SiO2 substrate, the surface is first cleaned by oxygen plasma to remove surface impurities and generate a large number of hydroxyl groups, then an appropriate amount of PS ball with a diameter of 300 nm is dropped to uniformly deposit on the surface of the substrate to form a single / multi-layer structure with a hexagonal close-packed structure, and the part of the PS ball bottom intersecting with the substrate surface will retain the hydrophilic hydroxyl group. Then the substrate is placed in a vacuum dryer and HMDS solution is added, sealed and reacted for a certain time, and HMDS will evaporate and diffuse onto the substrate to react with the hydroxyl group to form a hydrophobic TMS layer, while the circular part covered by the nanoball bottom contacting with the substrate will not be affected. Then water bath ultrasonic is carried out, the nanoball mask layer is cleaned, the surface is dried with nitrogen, and 120°C heating is carried out to stabilize the TMS hydrophobic layer, so as to form a regular nanoball mask shielding part of the hydrophilic substrate and the surrounding hydrophobic edge area;

[0055] S4. The DNA origami solution is dropped on the etched circular microarray, incubated in a humid container for 1 hour, so that the DNA origami is adsorbed on the hydrophilic site, and then the buffer solution mixed with 0.07% Tween-20, Tris-HCl and MgCl2 is repeatedly washed for 5 times to remove the excess DNA origami which is non-specifically combined in the hydrophobic area and competes for the same site in the hydrophilic area;

[0056] S5. The three kinds of DNA modified quantum dot solutions in S2 are sequentially added to the surface of the DNA origami microarray, and an appropriate amount of Tris-HCl buffer solution containing Mg 2+ is added, and incubated under constant temperature and humidity for 4 hours, so that the capture chain is fully matched and connected with the base in the captured chain, then the substrate surface is washed and rinsed with deionized water for 3 times, and dried with nitrogen, finally forming an ordered array of "DNA origami-quantum dot" composite structure units.

[0057] The above embodiment is only one of the embodiments of the present application, the DNA origami applied includes but is not limited to any one of quadrilateral, triangle, octagon or circle, and the modified quantum dot shape includes but is not limited to one of spherical, rod, core-shell, tetrahedron, cube or disc structure, as long as the modification made on the main design of the present application has no substantial meaning, and the technical problems solved are still consistent with the present application, which should be included in the protection scope of the present application.

Claims

1. A DNA origami based self-assembled polytypic quantum dot microarray, characterized in that, The microarray comprises a microarray substrate and arrayed DNA origami-quantum dot units. The microarray substrate surface has a plurality of hydrophilic arranged dot sites, and the dot sites are connected with DNA origami with hydroxyl groups to form a DNA origami microarray, and the DNA origami surface leads out quantum dot capture chains. The quantum dots are modified by a plurality of thiolated single-stranded DNAs to form a plurality of quantum dots with different types of captured chains, and are connected to the DNA origami according to the base complementary pairing principle. 2.The DNA origami self-assembly based multi-type quantum dot microarray of claim 1, wherein, The microarray substrate is subjected to periodic patterning treatment by nanosphere etching technology, with a period of 100-1000 nm, a period number of 100-10000 orders of magnitude, and arranged in one of a hexagonal array, a rectangular array, a triangular array or a rhombic array. 3.The DNA origami self-assembly based multi-type quantum dot microarray of claim 2, wherein, The microarray substrate is a semiconductor or an oxide. 4.The DNA origami self-assembly based multi-type quantum dot microarray of claim 1, wherein, The DNA origami is folded by a long DNA single strand and a plurality of short DNA single strands in a Mg 2+ environment according to the principle of base complementary pairing; the shape is one of quadrilateral, triangle, hexagon, octagon or circle; the size of the DNA origami is between 50-300 nm. 5.The DNA origami self-assembly based multi-type quantum dot microarray of claim 1, wherein, The quantum dots are single quantum dots and / or DNA self-assembled quantum dot multimers. 6.The DNA origami self-assembly based multi-type quantum dot microarray of claim 5, wherein, The quantum dots are in one of a spherical shape, a rod shape, a core-shell shape, a tetrahedron, a cube, and a disc structure, which together with the DNA origami form the DNA origami-quantum dot unit.

7. A method for preparing a multi-type quantum dot microarray based on DNA origami self-assembly, characterized in that, The method comprises the following steps: S1. Mixing long DNA main chains, short DNA staple chains and a plurality of quantum dot capture chains in a certain molar ratio, heating and maintaining in a polymerase chain nucleic acid amplifier for a period of time and annealing, and then purifying to obtain a DNA origami structure; S2. Adding a plurality of thiolated single-stranded DNAs matching the plurality of quantum dot capture chains in S1 as captured chains to a quantum dot solution containing a certain concentration of sodium chloride to modify the quantum dots, ultrasonicating and adding 1-butanol, centrifuging to remove supernatant and then performing electroelution to make the surfaces of various quantum dots be filled with corresponding various captured chains; S3. Using a semiconductor or oxide substrate, cleaning the surface by oxygen plasma treatment and generating hydroxyl groups, then dropping nanospheres to form a uniform hexagonal close-packed structure and hydrophobizing the substrate surface, removing the nanosphere mask layer by water bath ultrasonication, blowing dry with nitrogen and heating the substrate to obtain hydrophilic circular microarray sites; S4. Dropping a certain concentration of DNA origami solution on the etched hydrophilic microarray sites, incubating for 1 hour, and then washing with buffer multiple times to obtain a DNA origami microarray; S5. Dropping a suitable amount of DNA functionalized quantum dots on the DNA origami microarray surface in sequence, adding buffer, incubating at constant temperature and humidity for 4 hours, then washing with deionized water and drying to form arrayed DNA origami-quantum dot composite structure units on the substrate surface; and obtaining a multi-type quantum dot microarray.

8. The method for preparing a polymorphic quantum dot microarray based on DNA origami self-assembly according to claim 7, characterized in that, In S1, the long DNA main chains, short DNA staple chains and various quantum dot capture chains are mixed in a molar ratio of 1:15-25:15-25.

9. The method according to claim 7, wherein the method is characterized by, In S3, when the substrate surface is subjected to hydrophobic treatment, hexamethyldisilazane liquid is used to treat the surface to add a hydrophobic trimethylsilyl group to the substrate surface.

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