CN114849800B

CN114849800B - Microfluidic chip, preparation method and application of zinc oxide nanorod array in patterned growth

Info

Publication number: CN114849800B
Application number: CN202210402064.9A
Authority: CN
Inventors: 李欣; 李亚冰; 赵振杰; 谢文辉
Original assignee: East China Normal University
Current assignee: East China Normal University
Priority date: 2022-04-15
Filing date: 2022-04-15
Publication date: 2023-09-29
Anticipated expiration: 2042-04-15
Also published as: CN114849800A

Abstract

The invention discloses a microfluidic chip, a preparation method and application of patterning growth of a zinc oxide nano rod array, which is characterized in that the chip utilizes a machining method to prepare a PDMS substrate, and three PDMS substrates and a glass substrate are aligned and packaged to obtain the microfluidic chip, so that the growth of the patterning zinc oxide nano rod array is realized, wherein two PDMS substrates are respectively provided with a runner array and a through hole array structure; the flow channel consists of an inlet, a micro-chamber flow channel and an outlet; the micro-cavity runner is composed of round cavity structures parallel to the substrate, the round cavity structures correspond to the through hole structures one by one, and a double-layer structure of an upper runner of a lower micro-cavity is formed and used for defining a patterned growth area. Compared with the prior art, the invention has the advantages of improving the efficiency of the synthetic material and reducing the cost of the chip, can be widely used for developing field emission devices, gas sensors and biological fluorescence detection sensors, and provides good thought design and reference for related workers.

Description

Microfluidic chip, preparation method and application of zinc oxide nanorod array in patterned growth

Technical Field

The invention relates to the technical field of manufacturing of microfluidic chips, in particular to a microfluidic chip with a three-dimensional flow channel structure, a preparation method thereof and application of the microfluidic chip in realizing patterned growth of zinc oxide nanorod arrays.

Background

In recent years, along with the development of the fields of bioanalytical detection, organ chip, chemical synthesis, food detection, environmental detection, etc., the manufacturing technology of microfluidic chips is also continuously developed. Common microfluidic chip fabrication techniques include photolithography, thermocompression, molding, soft lithography, laser ablation, machining, LIGA, and the like. Photolithography is a processing technique that uses photo-imaging and photo-sensitive glue to pattern on a substrate of a microfluidic chip, such as silicon, glass, etc.; the hot pressing method is a chip processing technology with a microstructure obtained by aligning and heating a polymer substrate and a die and applying a certain pressure; the molding method is a chip processing technique in which a mold is obtained by photoresist or the like and a polymer is cured on the mold to obtain a microstructure; the soft lithography method uses an elastic mold to replace a hard mold used in lithography to form a microstructure; the laser ablation method is a non-contact micro-machining technology; machining processes are commonly used to machine micro-structured chips of increased size on hard substrates; LIGA is commonly used to fabricate chips with relatively large aspect ratios. According to the above processing method, the processing of the three-dimensional flow channel chip can be realized.

The micro-reactor is an important component of the development of the micro-fluidic technology, has remarkable and outstanding advantages in material synthesis compared with the common synthesis technology, such as less reagent consumption, high heat and mass transfer efficiency, easy accurate control of reaction parameters and real-time on-line monitoring, safer operation, high adaptability and integration, and the like, and is rapidly developed into a new platform for nano-material synthesis in recent years. The novel microfluidic synthesis chip can effectively realize the positioning synthesis of the nano material, and opens up a new way for the development of detection devices based on the nano material.

Zinc oxide is an n-type group II-VI semiconductor compound with a direct forbidden band width of 3.37 eV, and has a large exciton binding energy (60 meV) at room temperature. Zinc oxide is a polar semiconductor material, and has two crystal faces with opposite polarities and different surface binding energies, and can obtain different morphological structures by changing synthesis conditions. The zinc oxide nano material has unique physical and chemical properties, and has wide application prospects in a plurality of research fields, such as ultraviolet lasers, solar cells, nano generators, gas sensors and the like. Zinc oxide also has good biocompatibility and biodegradability, and is widely used in the field of biological detection. In the detection field, in order to realize efficient high-throughput detection, a plurality of detection units are often required to realize rapid and stable multi-sample detection. Therefore, new requirements are put on the design and preparation of the detection carrier. The zinc oxide nano material is suitable for being used as a high-flux detection carrier due to the advantages of the processing technology. In the traditional synthesis research of zinc oxide nano materials, a hydrothermal method is commonly used for preparing a large quantity of zinc oxide nano rod arrays with higher quality, but the material prepared by the conventional method has large reagent consumption, poor instant controllability and long time consumption for optimizing synthesis conditions, and a microfluidic synthesis technology can optimize reaction conditions to obtain a material with better performance. In addition, in order to enhance the performance of the detection sensor based on the zinc oxide nanomaterial, optimizing the zinc oxide nanostructure, realizing periodic or local patterned growth, and manufacturing a large-scale diversified substrate to realize mass production of the zinc oxide nanomaterial array is important.

The preparation method of the patterned nano-structure array in the prior art comprises photoetching, nanosphere photoetching, interference photoetching, laser writing, electron beam photoetching, nano injection and the like. But these techniques typically require clean rooms and expensive equipment, low throughput. The designs developed to date with respect to patterned in situ synthetic materials involve equipment that is expensive and difficult to mass produce, resulting in its application limitations.

Disclosure of Invention

The invention aims to provide a microfluidic chip, a preparation method and application of patterning growth of a zinc oxide nanorod array, aiming at the defects in the prior art, the microfluidic chip is composed of a plurality of runner arrays and through hole arrays, the circular cavity structures of the runner arrays are in one-to-one correspondence with the through hole structures of the through hole arrays, a double-layer structure of a lower-layer micro cavity and an upper-layer runner is formed, a patterning growth area is defined, the lower part of the circular micro cavity structure on each runner corresponds to the through hole to form a three-dimensional runner structure, and a micro pump and a micro valve can be integrated at the inlet and the outlet of each runner to realize timing and quantitative injection of chemical substances; the growth solution is provided through a flow channel connected with the outside, enters a circular cavity to perform chemical reaction, realizes the positioning growth of the material, and obtains the patterned zinc oxide nano rod array. The invention provides a reaction environment for flow synthesis through the flow channel, improves the efficiency of synthesizing materials, synthesizes the zinc oxide nanorods by utilizing the microfluidic chip, has less reagent consumption and stable quality, is convenient for controllable synthesis, prepares the microfluidic chip by a mechanical processing method, can realize batch production, greatly reduces the cost of the chip, has simple manufacturing method and easy operation, can be widely used for developing field emission devices, gas sensors, bioluminescence detection sensors and the like, and provides good thought design and reference for related workers. And can be widely applied to the field of biological fluorescence detection for efficiently detecting different types of fluorescent labeled biomolecules, such as DNA, cytokines, proteins, bacteria, viruses and the like.

The purpose of the invention is realized in the following way: the microfluidic chip is characterized by comprising three layers of PDMS substrates packaged on a glass substrate; the first layer of PDMS substrate is a parallel array formed by a plurality of cylindrical through holes to form a patterned growth area; the second layer PDMS substrate is a parallel array formed by a plurality of direct current channels, two ends of each direct current channel are provided with a channel outlet/inlet (if one end is a channel inlet, the other end is a channel outlet), a plurality of circular micro-cavity structures are arranged between the two channel outlet/inlets, and each circular micro-cavity corresponds to a cylindrical through hole on the first layer PDMS substrate one by one. Injecting a growth solution into the cylindrical through hole through the direct current channel, and finishing the update of the growth solution to realize the growth of the material; the third layer PDMS substrate is provided with a plurality of fluid inlets/outlets (if one side is a fluid inlet and the other end is a fluid outlet) which are arranged corresponding to the fluid channel outlets/inlets, and the fluid inlets/outlets of the third layer PDMS substrate are communicated with the fluid channel outlets/inlets of the second layer PDMS substrate to form an upper cover of the microfluidic chip, so that a closed three-dimensional fluid channel area is formed. The growth solution is injected into the flow channel and the cylindrical through hole through the fluid inlet, the growth of the patterned zinc oxide nano rod array is realized on the glass substrate, and the patterned zinc oxide nano rod array is prepared at the cylindrical through hole.

The preparation of the microfluidic chip is characterized by comprising the following steps:

(one), manufacturing PDMS substrate

1) Fabrication of a substrate

PDMS monomer and PDMS (curing agent) are mixed according to the mass ratio of 1-50: 1, preferably 10:1, uniformly mixing, placing into a vacuum drying oven, vacuumizing for 15 minutes, removing bubbles, pouring the bubbles on a silicon wafer, and curing to obtain a PDMS substrate, wherein the PDMS material can be replaced by a PMMA, PC or PS substrate.

2) Fabrication of first and second layer substrates

Drawing and manufacturing a substrate model, wherein the substrate model comprises a straight flow channel and a cylindrical through hole structure, a PDMS layer with a relative position mark of the straight flow channel and the cylindrical through hole is manufactured by a method of printing in batches by a carving machine, a first layer of PDMS substrate and a second layer of PDMS substrate are manufactured in batches by machining, and the height of the straight flow channel on the second layer of PDMS substrate is less than or equal to 300 micrometers, and the width is less than or equal to 2 millimeters; the height of the cylindrical through hole on the first layer of PDMS substrate is less than or equal to 300 micrometers, and the diameter is less than or equal to 1 millimeter.

3) Fabrication of third layer substrate

PDMS monomer and PDMS (curing agent) are mixed according to the mass ratio of 1-50: 1, preferably 10:1, uniformly mixing, placing in a vacuum drying oven, vacuumizing for 15 minutes, removing bubbles, pouring the bubbles on a silicon wafer without a structure, curing to obtain a molded third-layer PDMS substrate, and positioning and opening a fluid inlet/outlet on the third-layer PDMS substrate by a micromachining machine tool, wherein the thickness of the third-layer PDMS substrate is smaller than or equal to 8 mm as an upper cover of the chip.

The first and second PDMS substrates forming the straight flow channel and the cylindrical through hole array are made of biocompatible polymer materials, and PMMA, PC or PS thermoplastic materials can be selected, and the thickness of the first and second PDMS substrates is less than or equal to 300 microns.

(II) production of glass substrate

1) The glass sheet was ultrasonically cleaned with acetone, isopropyl alcohol and deionized water in this order for 15 minutes, and then dried with nitrogen to obtain a clean glass sheet.

2) Dissolving zinc acetate dihydrate in ethanol, preparing a seed solution by ultrasonic treatment for 3-15 minutes, spin-coating the seed solution on a glass base plate at a speed of 1000-3000 rpm, repeating for 2-5 times, then performing heat treatment at the temperature of 250-350 ℃ for 1-3 hours, decomposing zinc acetate into zinc oxide nanocrystals, and preparing a seed layer of a zinc oxide nanomaterial rod array on a clean glass substrate, wherein the mass ratio of zinc acetate dihydrate to ethanol is 1: 360-370.

(III), packaging of chip

And bonding the three layers of PDMS base and the glass substrate, and packaging the three layers of PDMS base and the glass substrate into the microfluidic chip.

The application of the microfluidic chip in the patterned growth of the zinc oxide nano rod array is characterized in that an integrated micropump and a micro valve are arranged on a fluid inlet/outlet of the third PDMS substrate and used for the timing and quantitative injection of reactants to realize the patterned zinc oxide nano rod array, and the synthesis specifically comprises the following steps:

1) Preparation of zinc oxide growth solution

Preparing a solution of hexamethylenetetramine, polyethyleneimine, zinc nitrate hexahydrate and water, and mixing the solution with the solution according to the weight ratio of 1:2 to 2.5:4 to 4.5: mixing 570-580 by mass ratio, and regulating pH=10-12 by using strong ammonia water to prepare zinc oxide growth solution;

2) Cleaning of flow channels and through holes

Injecting deionized water into the straight flow channel through the injection pump to the fluid inlet/outlet, and cleaning the flow channel and the through hole, wherein the flow rate is 5-50 microlitres/min, and the cleaning time is 5-15 min;

3) Injection of zinc oxide growth solution

Continuously injecting zinc oxide growth solution into the straight flow channel and the cylindrical through hole by the injection pump to the fluid inlet/outlet to finish the update of the growth solution, thereby realizing the growth of the material;

4) Synthesis of zinc oxide nanorods

Continuously injecting zinc oxide growth solution into the fluid inlet/outlet through an injection pump, placing the chip on a heating table for heating and growing for 1-3 hours, and preparing the zinc oxide nano rod with the patterned array structure at the cylindrical through hole, wherein the injection time of the zinc oxide growth solution is 15-150 minutes, and the flow rate of the zinc oxide growth solution is 5-50 microlitres/minute.

Compared with the prior art, the method has the advantages of low cost, simple manufacture, good universality and high yield, is easy to realize the mass production method to realize the growth of the patterned zinc oxide nanorod array, can reduce reagent consumption based on a microchannel, realize high efficiency and controllability, can change the design of a flow channel and a cavity according to the specific experiment requirement, realize different patterned nanomaterial arrays, has the function of high-flux detection, is particularly suitable for field emission devices, gas sensors and the like, and can be widely applied to the application of high-efficiency detection of different fluorescent labeled biomolecules such as DNA, cytokines, proteins, bacteria, viruses and the like in the field of biological fluorescence detection.

Drawings

FIG. 1 is a schematic diagram of a microfluidic chip according to the present invention;

FIG. 2 is a schematic view of a third layer of substrate structure;

FIG. 3 is a schematic diagram of a second layer substrate structure;

FIG. 4 is a schematic view of a first layer of substrate structure;

FIG. 5 is an overall schematic of an anastomosis site and array between three layers of substrates;

FIG. 6 is a photograph of a microfluidic chip prepared in example 2;

FIG. 7 is a photograph of a zinc oxide nanorod array prepared in example 3;

FIG. 8 is a scanning electron micrograph of the zinc oxide nanorods prepared in example 1;

fig. 9 is a scanning electron micrograph of the zinc oxide nanorods prepared in example 2.

Detailed Description

The present invention will be described in further detail with reference to specific examples.

Example 1

Referring to fig. 1, the microfluidic chip of the present invention is formed by packaging a first layer of PDMS substrate 2, a second layer of PDMS substrate 3 and a third layer of PDMS substrate 4 sequentially disposed on a glass substrate 1, wherein the third layer of PDMS substrate 4 is provided with a plurality of fluid inlets/outlets 4-1 (if one end is a fluid inlet, the other end is a fluid outlet); the fluid inlet/outlet 4-1 is communicated with the flow channel outlet/inlet 3-3 of the second layer PDMS substrate to form an upper cover of the microfluidic chip, a closed three-dimensional flow channel area is formed, a growth solution is injected into the flow channel 3-1 of the second layer PDMS substrate 3 through a fluid inlet and finally enters the cylindrical through hole 2-1 of the first layer PDMS substrate 2, the growth of the patterned zinc oxide nano rod array is realized on the glass substrate, and the patterned zinc oxide nano rod array is prepared at the cylindrical through hole 2-1; the glass substrate 1 is spin-coated with a seed layer 5 of zinc oxide crystals.

Referring to fig. 2, the first layer PDMS substrate 2 is provided with a parallel array of a plurality of cylindrical through holes 2-1, so as to form a patterned growth area, wherein the height of the cylindrical through holes 2-1 is less than or equal to 300 micrometers, and the diameter is less than or equal to 1 millimeter.

Referring to fig. 3, the second layer PDMS substrate 3 is a parallel array formed by a plurality of straight channels 3-1, wherein the two ends of the straight channels 3-1 are provided with channel outlet/inlet 3-3, if one end is a channel inlet, the other end is a channel outlet, and a plurality of circular micro-chamber structures 3-2 are arranged on the channel between the two channel outlet/inlet 3-3. Wherein, each round micro-cavity structure 3-2 arranged in the horizontal direction of the straight flow channel 3-1 corresponds to the cylindrical through holes 2-1 on the first layer PDMS substrate 2 one by one, and the growth solution is injected into the cylindrical through holes 2-1 through the straight flow channel 3-1, and the update of the growth solution is completed, thereby realizing the growth of the material.

Referring to fig. 4, the third layer PDMS substrate 4 is provided with a plurality of fluid inlets/outlets 4-1 corresponding to the fluid channel outlets/inlets 3-3, and if one side of the fluid inlet/outlet 4-1 is an inlet, the other side of the fluid inlet/outlet 4-1 is an outlet. The inlet and the outlet are respectively connected with the fluid inlet and the fluid outlet at two ends of the straight flow channel 3-1 on the second layer PDMS substrate 3 to form an upper cover of the chip, thus forming a closed three-dimensional flow channel area. The growth solution enters the straight flow channel 3-1 through the inlet, and is injected into the cylindrical through hole 2-1 to realize the growth of the patterned zinc oxide nano rod array on the glass substrate 1.

The first layer of PDMS substrate 2, the second layer of PDMS substrate 3 and the third layer of PDMS substrate 4 are bonded with the glass substrate 1, and are packaged into the microfluidic chip.

Referring to fig. 5, which shows the anastomotic positional relationship between the upper, middle and lower PDMS substrates, and the anastomotic positional relationship and the array state with the glass substrate 1, and simultaneously shows the correspondence between the straight channels 3-1 and the cylindrical through holes 2-1 and the positional relationship between the fluid inlet/outlet ports 4-1.

Example 2

The preparation method of the microfluidic chip comprises the following specific steps:

first, PDMS substrate (2, 3, 4) was fabricated

1) Printing a first layer of substrate and a second layer of substrate in batch, drawing by Graphtec Pro Studio, cutting to manufacture a substrate model, and mainly comprising two parts: a straight flow channel 3-1 and a cylindrical through hole 2-1. Wherein the width of the direct current channel 3-1 is 1 millimeter, the height is 200 micrometers, and the length is 15 millimeters; the diameter of the cylindrical through hole 2-1 is 800 micrometers, the height is 200 micrometers, the position of each round hole corresponds to the position of the round micro-cavity structure 3-2, as shown in fig. 5, the first layer PDMS substrate 2 and the second layer PDMS substrate 3 with the marks of the positions of the straight flow channel 3-1 and the cylindrical through hole 2-1 are manufactured by a method of carving machine batch printing, and the thickness of the first layer PDMS substrate and the second layer PDMS substrate 3 is 200 micrometers.

2) Moulding third layer substrate

Mixing liquid PDMS monomer and PDMS (curing agent) according to the mass ratio of 10:1, fully stirring, pouring the mixture on a silicon wafer of a culture dish after bubble removal, curing the mixture for 3 hours at the temperature of 80 ℃ with the thickness of PDMS of 5 mm, stripping the cured PDMS from a mold to form a non-structural PDMS substrate, and positioning the non-structural PDMS substrate by a micromachining milling machine, and opening a corresponding runner inlet and outlet 4-1 on the PDMS substrate by using a needle of 0.75 mm to obtain a third layer PDMS substrate 4.

(II) manufacturing a substrate

1) Preparing 10mM zinc acetate dissolved in ethanol solution;

2) Spin-coating the solution onto a glass sheet at 2000 rpm, repeating 3 times;

3) The above glass sheet spin-coated with zinc acetate was fired at 300℃for 1 hour to prepare a seed layer 5 spin-coated with zinc oxide crystals on a glass substrate 1, the thickness of which was 11 nm.

(III), packaging of chip

1) Bonding of second and third substrates

The surfaces of the second-layer PDMS substrate 3 and the third-layer PDMS substrate 4 are subjected to plasma oxidation treatment, so that an a substrate formed after the second-layer PDMS substrate 3 and the third-layer PDMS substrate 4 are bonded is realized;

2) Bonding of a first layer of substrate to a base

The surfaces of the first layer PDMS substrate 2 and the glass substrate 1 are oxidized by plasma to realize a b substrate formed after the bonding of the first layer PDMS substrate 2 and the glass substrate 1;

3) Chip bonding)

Referring to fig. 6, the surfaces of the substrate a and the substrate b are oxidized by using plasma to realize the bonding of the substrate a and the substrate b, so as to prepare the microfluidic chip for realizing the patterning growth of the zinc oxide nanorod array.

The substrate material of the chip of the embodiment is a glass sheet, and the three-layer substrate is a flat sheet made of PDMS; the height of the straight flow channel 3-1 is 200 micrometers, and the width is 2 millimeters; the height of the cylindrical through hole 2-1 is 200 micrometers, and the diameter is 800 micrometers; the third layer of PDMS substrate 4 was 5 mm in height. The substrate material of the chip is a glass sheet, and the substrate material is a flat sheet made of PDMS.

Example 3

The application of the microfluidic chip for synthesizing the zinc oxide nanorod array comprises the following specific steps:

1) Preparing zinc oxide growth solution

Preparing a solution of hexamethylenetetramine, polyethyleneimine, zinc nitrate hexahydrate and water according to the weight ratio of 1:2 to 2.5:4 to 4.5: 570-580, and adjusting the pH value to 11 by using strong ammonia water to prepare zinc oxide growth solution.

2) Cleaning of flow channels and through holes

Continuously injecting deionized water into the fluid inlet/outlet 4-1, namely the inlet, through a syringe pump at an injection speed of 21.14 microlitres/min; the time was 10 minutes.

3) Injection of zinc oxide growth solution

4) Synthesis of zinc oxide nanorods

After the end of the above step 3, the chip was placed on a heating stage at 90℃for 1 hour, and zinc oxide growth solution was continuously injected into the fluid inlet/outlet 4-1 by a syringe pump at a rate of 21.14. Mu.l/min.

Referring to fig. 7, zinc oxide nanorods having a patterned array structure are manufactured at cylindrical through holes 2-1 on a glass substrate 1.

Referring to fig. 8, the surface morphology of the zinc oxide nanorod array with the patterned array structure prepared above can be seen to be a rod-like structure by scanning with an electron microscope, which indicates that the diameter of the ZnO nanorod synthesized in the micro-chamber is uniform.

Referring to fig. 9, the zinc oxide nanorods with the patterned array structure prepared above are scanned by an electron microscope, so that the side morphology of the zinc oxide nanorod array is a bar-shaped structure, which indicates that the length of the ZnO nanorods synthesized in the micro-chamber is uniform.

According to the invention, the growth solution in the flow channel is accurately regulated and controlled in real time, the growth of zinc oxide is completed through a cavity formed by the flow channel and the through hole in the whole synthesis process, the fluid behavior is mainly determined by viscosity due to the reduction of the size, and the high-specific-surface-area channel can realize rapid mass transfer and heat transfer in a chip, so that a product with smaller difference is obtained and the yield is improved. The preparation of the patterned zinc oxide nano rod is realized by supplying a growth solution to the micro channel in real time and synthesizing and growing on the glass substrate corresponding to the through hole. Compared with the existing material synthesis system, the micro-channel-based material synthesis system can reduce reagent consumption, realize high efficiency and controllability, can change the design of a flow channel and a chamber according to the needs of specific experiments, and realize the functions of different patterned nano-material arrays and high-flux detection.

The invention is further described with reference to the following claims, which are not intended to limit the scope of the invention.

Claims

1. The microfluidic chip is characterized by being formed by packaging a first layer of PDMS substrate, a second layer of PDMS substrate and a third layer of PDMS substrate which are sequentially arranged on a glass substrate, wherein a plurality of cylindrical through holes are formed in the first layer of PDMS substrate to form a through hole array which is arranged in parallel; the second layer of PDMS substrate is provided with a plurality of straight flow channels which are arranged corresponding to the through hole arrays; two ends of the straight flow channel are respectively provided with a flow channel outlet/inlet, a plurality of round micro-cavity structures which are arranged corresponding to the cylindrical through holes are arranged between the two outlet/inlet, and are communicated with the cylindrical through holes of the first layer of PDMS substrate in a bonding way; the third layer PDMS substrate is provided with a plurality of fluid inlets/outlets which are arranged corresponding to the fluid outlets/inlets, and are in bonding communication with the fluid outlets/inlets of the second layer PDMS substrate to form an upper cover of the microfluidic chip, a closed three-dimensional fluid channel area is formed, growth solution enters the straight channel through the fluid inlets/outlets, and the patterned zinc oxide nano rod array is grown on the glass substrate at the cylindrical through hole to prepare the patterned zinc oxide nano rod array; the glass substrate is provided with a seed layer of zinc oxide nanocrystals.

2. A method for preparing a microfluidic chip according to claim 1, wherein the method for preparing a microfluidic chip comprises the following steps:

(I) preparation of PDMS substrate

1) Fabrication of first and second layer substrates

The method for preparing the first layer of PDMS substrate and the second layer of PDMS substrate in batches by machining specifically comprises the following steps: drawing to manufacture substrate models of the straight flow channel and the cylindrical through hole, and respectively manufacturing a first layer of PDMS substrate and a second layer of PDMS substrate with relative position marks of the straight flow channel and the cylindrical through hole by a method of printing in batches by a character carving machine;

2) Fabrication of third layer substrate

Pouring a substrate in a culture dish, molding a third layer of PDMS substrate, and positioning and opening a fluid inlet/outlet on the third layer of PDMS substrate through a micromachining machine tool;

(II) production of glass substrate

Preparing a seed layer of zinc oxide nanocrystals on a glass substrate using zinc acetate dihydrate dissolved in ethanol;

(III), packaging of chip

And bonding the first layer of PDMS substrate with the second layer of PDMS substrate and the third layer of PDMS substrate and the glass substrate of the third layer of PDMS substrate, and packaging the first layer of PDMS substrate and the third layer of PDMS substrate into the microfluidic chip.

3. The method for preparing a microfluidic chip according to claim 2, wherein the first, second and third PDMS substrates are made of a biocompatible polymer material of polydimethylsiloxane, polymethyl methacrylate, polycarbonate or polystyrene, and have a thickness of 300 μm or less.

4. The method for manufacturing a microfluidic chip according to claim 2, wherein the height of the flow channel is 2 mm or less and the width of the second layer of PDMS substrate is the thickness of the second layer of PDMS substrate.

5. The method for manufacturing a microfluidic chip according to claim 2, wherein the diameter of the cylindrical through hole is 1 cm or less and the height thereof is the thickness of the first layer of PDMS substrate.

6. The preparation method of the microfluidic chip according to claim 2, wherein the zinc oxide nanocrystals are prepared into a seed layer on a clean glass substrate by a solution spin coating method, comprising the following specific steps:

1) Sequentially ultrasonically cleaning the glass sheet by using acetone, isopropanol and deionized water for 15 minutes, and then drying by using nitrogen to obtain a clean glass sheet;

2) Zinc acetate dihydrate and ethanol were mixed at 1: mixing 360-370 parts by mass, performing ultrasonic treatment for 3-15 minutes to obtain a seed solution, spin-coating the seed solution on a glass substrate (1) at a speed of 1000-3000 rpm, repeating the spin-coating for 2-5 times, performing heat treatment at the temperature of 250-350 ℃ for 1-3 hours, decomposing zinc acetate into zinc oxide nanocrystals, and obtaining a seed layer (5) for growing a zinc oxide nanorod array, wherein the thickness of the seed layer (5) is 8-16 nanometers.

7. An application of a microfluidic chip prepared by the preparation method of the microfluidic chip according to claim 2 in patterning growth of a zinc oxide nanorod array, which is characterized in that an integrated micropump and a microvalve are arranged on a fluid inlet/outlet (4-1) of a third-layer PDMS substrate (4) for timing and quantitative injection of reactants to realize patterning of the zinc oxide nanorod array, and the synthesis specifically comprises the following steps:

1) Preparation of zinc oxide growth solution

Hexamethylenetetramine, polyethyleneimine, zinc nitrate hexahydrate and water are mixed according to a proportion of 1:2 to 2.5:4 to 4.5: mixing 570-580 by mass ratio, and regulating pH=10-12 by ammonia water to prepare zinc oxide growth solution;

2) Cleaning of flow channels and through holes

Injecting deionized water into the straight flow channel (3-1) through the injection pump to the fluid inlet/outlet (4-1), wherein the flow rate is 5-50 microlitres/min, and cleaning the flow channel and the through hole for 5-15 min;

3) Injection of zinc oxide growth solution

Injecting zinc oxide growth solution into the straight flow channel (3-1) and the cylindrical through hole (2-1) through the injection pump to the fluid inlet/outlet (4-1), so as to finish the update of the growth solution and realize the growth of materials;

4) Synthesis of zinc oxide nanorods

Continuously injecting zinc oxide growth solution into the fluid inlet/outlet (4-1) through an injection pump, placing the chip on a heating table for heating and growing for 1-3 hours, and preparing the zinc oxide nanorods with the patterned array structure at the cylindrical through holes (2-1), wherein the injection time of the zinc oxide growth solution is 15-150 minutes, and the flow rate of the zinc oxide growth solution is 5-50 microlitres/minute.