CN114849800A

CN114849800A - Micro-fluidic chip, preparation method and application of patterned growth of zinc oxide nanorod array

Info

Publication number: CN114849800A
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: 2022-08-05
Anticipated expiration: 2042-04-15
Also published as: CN114849800B

Abstract

The invention discloses a micro-fluidic chip and a preparation method thereof and application of patterned growth of a zinc oxide nanorod array, and is characterized in that the chip is used for preparing a PDMS substrate by using a machining method, and aligning and packaging three PDMS substrates and a glass substrate to obtain the micro-fluidic chip so as to realize the growth of the patterned zinc oxide nanorod array, 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-cavity flow channel and an outlet; the micro-chamber flow channel is composed of circular chamber structures parallel to the substrate, the circular chamber structures correspond to the through hole structures one by one, and a double-layer structure of the upper-layer flow channel of the lower-layer micro-chamber 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 synthesizing materials and reducing the chip cost, can be widely used for developing field emission devices, gas sensors and bioluminescence detection sensors, and provides good idea design and reference for related workers.

Description

Micro-fluidic chip, preparation method and application of patterned growth of zinc oxide nanorod array

Technical Field

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

Background

In recent years, the technology for manufacturing microfluidic chips has been developed with the development of fields such as bioanalytical testing, organ chips, chemical synthesis, food testing, and environmental testing. Common microfluidic chip fabrication techniques include photolithography, hot pressing, molding, soft lithography, laser ablation, machining, and LIGA. The photolithography is a processing technology for patterning on a substrate of a microfluidic chip, such as silicon, glass and the like, by using optical imaging and photosensitive adhesive; the hot pressing method is a chip processing technology with a microstructure, which is obtained by aligning and heating a polymer substrate and a mould and applying certain pressure; the molding method is a chip processing technology for obtaining a mold through photoresist and the like and curing high polymer 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 methods are commonly used to machine oversized microstructure chips on hard substrates; the LIGA method is commonly used for manufacturing chips with a relatively large aspect ratio. According to the processing method, the three-dimensional flow channel chip can be processed.

The micro-reactor is an important component part for the development of the micro-fluidic technology, has obvious and outstanding advantages in the material synthesis aspect compared with the common synthesis technology, such as less reagent consumption, high heat transfer and mass transfer efficiency, easy and accurate control of reaction parameters, 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 development of a novel microfluidic synthesis chip can effectively realize the positioning synthesis of the nano material, and opens up a new way for the development of a detection device based on the nano material.

Zinc oxide is an n-type group II-VI semiconductor compound having a direct forbidden band width of 3.37 eV, and has a large exciton confinement energy (60 meV) at room temperature. The zinc oxide is a polar semiconductor material, 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 multiple research fields, such as ultraviolet lasers, solar cells, nano generators, gas sensors and the like. The zinc oxide also has good biocompatibility and biodegradability, and is widely used in the field of biological detection. In the field of detection, in order to achieve efficient and high-throughput detection, multiple detection units are often required to achieve 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 amount of zinc oxide nano rod arrays with higher quality, but because the material prepared by the conventional method has large reagent consumption and poorer instant controllability, the synthesis condition is long in optimization time consumption, and the microfluidic synthesis technology can optimize the reaction condition to obtain a material with better performance. In addition, in order to enhance the performance of the detection sensor based on the zinc oxide nano material, optimize the zinc oxide nano structure and realize periodic or local patterning growth, the mass production of the zinc oxide nano material array by manufacturing diversified substrates on a large scale is very important.

The preparation method of the patterned nanostructure array in the prior art comprises photoetching, nanosphere photoetching, interference photoetching, laser writing, electron beam photoetching, nano-injection and the like. However, these techniques typically require clean rooms and expensive equipment with low throughput. The designs developed to date for patterned in situ synthesis of materials involve expensive equipment and are difficult to mass produce, resulting in limitations in their use.

Disclosure of Invention

The invention aims to provide a micro-fluidic chip, a preparation method and application of patterned growth of a zinc oxide nanorod array aiming at the defects of the prior art, the micro-fluidic chip consisting of a plurality of flow channel arrays and through hole arrays is adopted, the circular cavity structures of the flow channel arrays correspond to the through hole structures of the through hole arrays one by one, a double-layer structure of a lower micro-cavity and an upper flow channel is formed and is used for defining a region for patterned growth, the lower part of the circular micro-cavity structure on each flow channel corresponds to the through hole to form a three-dimensional flow channel structure, and a micro pump and a micro valve can be integrated at the inlet and the outlet of each flow channel and are used for realizing the timed and quantitative injection of chemical substances; the growth solution is provided through a flow channel connected with the outside and enters the circular chamber to carry out chemical reaction, so that the positioned growth of the material is realized, and the patterned zinc oxide nanorod array is obtained. The invention provides a reaction environment of flow synthesis through a flow passage, improves the efficiency of synthesizing materials, utilizes the micro-fluidic chip to synthesize the zinc oxide nano rod, has less reagent dosage, stable quality and convenient controllable synthesis, prepares the micro-fluidic chip by a machining method, can realize batch production, greatly reduces the cost of the chip, has simple manufacturing method and easy operation, can be widely used for researching field emission devices, gas sensors, biological fluorescence detection sensors and the like, and provides good idea design and reference for related workers. And can be widely applied to the field of biological fluorescence detection for efficiently detecting different types of fluorescence-labeled biomolecules, such as DNA, cytokines, proteins, bacteria, viruses and the like.

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

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

(I) preparing a PDMS substrate

1) Fabrication of substrates

Mixing a PDMS monomer and a PDMS (curing agent) according to a mass ratio of 1-50: 1 mixing, preferably 10:1, uniformly mixing, putting into a vacuum drying oven, vacuumizing for 15 minutes, removing bubbles, pouring on a silicon chip, curing to obtain a PDMS substrate, and replacing the PDMS material with a PMMA, PC or PS substrate.

2) Manufacture 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, manufacturing a PDMS layer with relative position marks of the straight flow channel and the cylindrical through hole by a batch printing method of a carving machine, and mechanically processing and preparing a first PDMS substrate and a second PDMS substrate in batch, wherein the straight flow channel on the second PDMS substrate has the height of less than or equal to 300 micrometers and the width of less than or equal to 2 millimeters; the height of the cylindrical through hole on the first layer PDMS substrate is less than or equal to 300 micrometers, and the diameter of the cylindrical through hole on the first layer PDMS substrate is less than or equal to 1 millimeter.

3) Fabrication of third layer substrate

Mixing a PDMS monomer and a PDMS (curing agent) according to a mass ratio of 1-50: 1, preferably 10:1, uniformly mixing, placing in a vacuum drying oven, vacuumizing for 15 minutes, removing bubbles, pouring on a structureless silicon chip, curing to obtain a molded third-layer PDMS substrate serving as an upper cover of the chip, wherein the thickness of the third-layer PDMS substrate is less than or equal to 8 millimeters, and positioning and opening a fluid inlet/outlet on the third-layer PDMS substrate through a micro machining tool.

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

(II) production of glass substrate

1) And ultrasonically cleaning the glass sheet for 15 minutes by using acetone, isopropanol and deionized water in sequence, and then drying by using nitrogen to obtain the clean glass sheet.

2) Dissolving zinc acetate dihydrate in ethanol, performing ultrasonic treatment for 3-15 minutes to obtain a seed solution, spin-coating the seed solution on a glass substrate at the speed of 1000-3000 revolutions per minute, repeating the steps for 2-5 times, performing heat treatment at the temperature of 250-350 ℃ for 1-3 hours to decompose the zinc acetate into zinc oxide nanocrystals, and preparing a seed layer of a zinc oxide nano material rod array on a clean glass substrate, wherein the mass ratio of the zinc acetate dihydrate to the ethanol is 1: 360-370.

(III) encapsulation of chip

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

The application of the micro-fluidic chip in patterned growth of the zinc oxide nanorod array is characterized in that an integrated micro pump and a micro valve are arranged on a fluid inlet/outlet of a third PDMS substrate and are used for injecting reactants at regular time and in fixed quantity to realize the patterned zinc oxide nanorod 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, wherein the weight ratio of the solution to the water is 1: 2-2.5: 4-4.5: 570-580, and regulating the pH to be 10-12 by using concentrated ammonia water to prepare a zinc oxide growth solution;

2) cleaning of flow passages and through holes

Injecting deionized water into the straight flow channel from the fluid inlet/outlet through an injection pump, and cleaning the flow channel and the through hole, wherein the flow rate is 5-50 microliters/minute, and the cleaning time is 5-15 minutes;

3) injection of zinc oxide growth solution

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

4) synthesis of zinc oxide nano-rod

And continuously injecting a 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 nanorod 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 microliters/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 batch production to realize the growth of the patterned zinc oxide nanorod array, can reduce the consumption of reagents based on a microchannel, realize high efficiency and controllability, change the design of a flow channel and a chamber according to the requirements of specific experiments, 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 field of biological fluorescence detection to efficiently detect different types of fluorescence-labeled biomolecules such as DNA, cytokines, proteins, bacteria, viruses and the like.

Drawings

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

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

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

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

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

FIG. 6 is a photograph of a real object of the 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 encapsulating 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 inlet/outlet ports 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 of PDMS substrate to form an upper cover of the microfluidic chip to form a closed three-dimensional flow channel area, a growth solution is injected into the flow channel 3-1 of the second layer of PDMS substrate 3 through the fluid inlet and finally enters the cylindrical through hole 2-1 of the first layer of PDMS substrate 2, the growth of the patterned zinc oxide nanorod array is realized on the glass substrate, and the patterned zinc oxide nanorod 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, a parallel array of a plurality of cylindrical through holes 2-1 is formed in the first layer PDMS substrate 2 to form a patterned growth region, wherein the height of the cylindrical through holes 2-1 is not more than 300 micrometers, and the diameter is not more than 1 mm.

Referring to fig. 3, the second layer of PDMS substrate 3 is a parallel array composed of a plurality of straight channels 3-1, two ends of the straight channels 3-1 are provided with channel inlets/outlets 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 inlets/outlets 3-3. Wherein, each round micro-chamber structure 3-2 arranged in the horizontal direction of the straight flow channel 3-1 corresponds to the cylindrical through hole 2-1 on the first layer PDMS substrate 2 one by one, and the growth solution is injected into the cylindrical through hole 2-1 through the straight flow channel 3-1, and the updating of the growth solution is completed, so as to realize the growth of the material.

Referring to fig. 4, a plurality of fluid inlets/outlets 4-1 corresponding to the fluid channel outlets/inlets 3-3 are disposed on the third PDMS substrate 4, and if the fluid inlet/outlet 4-1 on one side is an inlet and the fluid inlet/outlet 4-1 on the other side is an outlet. The inlet and the outlet are respectively connected with the fluid inlet and the fluid outlet at the two ends of the straight flow channel 3-1 on the second layer PDMS substrate 3 to form an upper cover of the chip, so as to form 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 nanorod array on the glass substrate 1.

And bonding the first layer of PDMS substrate 2, the second layer of PDMS substrate 3 and the third layer of PDMS substrate 4 with the glass substrate 1, and packaging the substrates into the microfluidic chip.

Referring to fig. 5, the diagram shows the coincidence position relationship between the PDMS substrates of the upper, middle and lower layers, and the coincidence position relationship and the array state with the glass substrate 1, and also shows the correspondence relationship between the straight flow channel 3-1 and the cylindrical through hole 2-1, and the position relationship between the fluid inlet/outlet 4-1.

Example 2

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

first, preparing PDMS substrate (2, 3, 4)

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

2) Molding the third layer substrate

Mixing a liquid PDMS monomer and PDMS (curing agent) according to a mass ratio of 10:1, fully stirring, removing bubbles, pouring onto a silicon chip of a culture dish, curing at 80 ℃ for 3 hours, peeling the cured PDMS from a mold to obtain a structurally-free PDMS substrate, positioning the substrate by a micro-machining milling machine, and punching a corresponding flow channel inlet and outlet 4-1 on the PDMS substrate by using a 0.75 mm needle to obtain a third layer of PDMS substrate 4.

(II) preparing a substrate

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

2) spin-coating the solution onto glass sheets at 2000 rpm, and repeating for 3 times;

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

(III) encapsulation of chip

1) Bonding of second and third substrates

Carrying out oxidation treatment on the surfaces of the second layer of PDMS substrate 3 and the third layer of PDMS substrate 4 by using plasma, so as to realize a substrate a formed after the second layer of PDMS substrate 3 is bonded with the third layer of PDMS substrate 4;

2) bonding of first layer substrate to base

Carrying out oxidation treatment on the surfaces of the first layer of PDMS substrate 2 and the glass substrate 1 by using plasma to realize the bonding of the first layer of PDMS substrate 2 and the glass substrate 1 to form a substrate b;

3) ) bonding of chips

Referring to fig. 6, the surfaces of the substrate a and the substrate b are oxidized by plasma to realize the bonding of the substrate a and the substrate b, and the microfluidic chip for realizing the patterned growth of the zinc oxide nanorod array is prepared.

The substrate material of the chip of the embodiment is a glass sheet, and the three layers of substrates are flat sheets 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 high. 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 in 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: 2-2.5: 4-4.5: 570-580, and adjusting the pH to be 11 by using strong ammonia water to prepare the zinc oxide growth solution.

2) Cleaning of flow passages and through holes

Continuously injecting deionized water into the fluid inlet/outlet 4-1, namely the inlet by using a syringe pump, wherein the injection speed is 21.14 microliter/min; the time period required was 10 minutes.

3) Injection of zinc oxide growth solution

4) Synthesis of zinc oxide nano-rod

After the end of the above step 3, the chip was placed on a heating table, heated at 90 ℃ for 1 hour, and the zinc oxide growth solution was continuously injected into the fluid inlet/outlet port 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 fabricated at cylindrical through-holes 2-1 on a glass substrate 1.

Referring to fig. 8, the surface morphology of the prepared zinc oxide nanorod array with the patterned array structure can be seen to be a rod-shaped structure through scanning of 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, and it can be seen that the side morphology of the zinc oxide nanorod array is a rod-shaped structure, which indicates that the lengths of the ZnO nanorods synthesized in the micro-chamber are uniform.

The invention utilizes the growth solution in the flow channel to accurately regulate and control 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 channel with high specific surface area ensures that the rapid mass transfer and heat transfer can be realized in the chip, thereby obtaining products with smaller difference and improving the yield. And synthesizing and growing on the glass substrate corresponding to the through hole by supplying a growth solution to the micro-channel in real time, so as to realize the preparation of the patterned zinc oxide nano-rod. Compared with the existing material synthesis system, the micro-channel-based nano material synthesis chip can reduce reagent consumption, realize high efficiency and controllability, change the design of a flow channel and a cavity according to the needs of specific experiments, and realize the functions of different patterned nano material arrays and high-flux detection.

The invention has been described in further detail in order to avoid limiting the scope of the invention, and it is intended that all such equivalent embodiments be included within the scope of the following claims.

Claims

1. A micro-fluidic chip is characterized in that the micro-fluidic chip is formed by packaging a first PDMS substrate (2), a second PDMS substrate (3) and a third PDMS substrate (4) which are sequentially arranged on a glass substrate (1), wherein a plurality of cylindrical through holes (2-1) are arranged on the first PDMS substrate (2) to form a through hole array which is arranged in parallel; a plurality of straight flow channels (3-1) which are arranged corresponding to the through hole array are arranged on the second layer PDMS substrate (3); two ends of the straight flow channel (3-1) are respectively provided with a flow channel outlet/inlet (3-3), a plurality of circular micro-chamber structures (3-2) which correspond to the cylindrical through holes (2-1) are arranged between the two outlets and inlets, and are in bonding communication with the cylindrical through holes (2-1) of the first layer of PDMS substrate (2); the third layer of PDMS substrate (4) is provided with a plurality of fluid inlet/outlet (4-1) which are arranged corresponding to the fluid channel outlet/inlet (3-3), and are in bonding communication with the fluid channel outlet/inlet (3-3) of the second layer of PDMS substrate (3) to form an upper cover of the microfluidic chip, so as to form a closed three-dimensional flow channel area, a growth solution enters the straight flow channel (3-1) through the fluid inlet/outlet (4-1), and the growth of the patterned zinc oxide nanorod array is realized on the glass substrate (1) at the cylindrical through hole (2-1), so that the patterned zinc oxide nanorod array is prepared.

2. The microfluidic chip according to claim 1, wherein the glass substrate (1) is provided with a seed layer (5) of zinc oxide nanocrystals.

3. The method for preparing the microfluidic chip of claim 1, wherein the method for preparing the microfluidic chip specifically comprises the following steps:

preparation of PDMS substrate

1) Manufacture of first and second layer substrates

The method for preparing the first layer of PDMS substrate (2) and the second layer of PDMS substrate (3) in batches by machining specifically comprises the following steps: drawing and manufacturing substrate models of the straight flow channel (3-1) and the cylindrical through hole (2-1), and respectively manufacturing a first layer PDMS substrate (2) and a second layer PDMS substrate (3) with relative position marks of the straight flow channel (3-1) and the cylindrical through hole (2-1) by a carving machine batch printing method;

2) fabrication of third layer substrate

Pouring a substrate in a culture dish, molding a third layer of PDMS substrate (4), and positioning and opening a fluid inlet/outlet (4-1) on the third layer of PDMS substrate (4) through a micro machining machine tool;

(II) production of glass substrate

Preparing a seed layer of zinc oxide nanocrystals on a glass substrate (1) by using zinc acetate dihydrate dissolved in ethanol;

(III) encapsulation of chip

And bonding the first PDMS substrate (2), the second PDMS substrate (3), the third PDMS substrate (4) and the glass substrate (1) thereof, and packaging the bonded substrates into the microfluidic chip.

4. The method for preparing a microfluidic chip according to claim 3, wherein the first PDMS substrate (2), the second PDMS substrate (3) and the third PDMS substrate (4) are made of a biocompatible polymer material such as Polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), Polycarbonate (PC) or Polystyrene (PS), and the thickness of the biocompatible polymer material is less than or equal to 300 μm.

5. The method for preparing a microfluidic chip according to claim 3, wherein the height of the flow channel (3-1) is the thickness of the second PDMS substrate (3), and the width thereof is less than or equal to 2 mm.

6. The method for preparing a microfluidic chip according to claim 3, wherein the diameter of the cylindrical through hole (2-1) is less than or equal to 1 cm, and the height of the cylindrical through hole is equal to the thickness of the first PDMS substrate (2).

7. The method for preparing a microfluidic chip according to claim 3, wherein the zinc oxide nanocrystals are prepared as a seed layer on a clean glass substrate by a solution spin coating method, comprising the following steps:

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

2) zinc acetate dihydrate and ethanol were mixed in 1: mixing the materials according to a mass ratio of 360-370, performing ultrasonic treatment for 3-15 minutes to prepare a seed solution, coating the seed solution on a glass substrate (1) in a rotating manner at a speed of 1000-3000 r/min, repeating the steps for 2-5 times, performing heat treatment at a temperature of 250-350 ℃ for 1-3 hours, decomposing zinc acetate into zinc oxide nano crystals, and preparing a seed layer (5) for growth of a zinc oxide nano-rod array, wherein the thickness of the seed layer is 8-16 nanometers.

8. An application of the micro-fluidic chip prepared by the preparation method of the micro-fluidic chip according to claim 3 in patterned growth of a zinc oxide nano-rod array is characterized in that an integrated micro-pump and a micro-valve are arranged on a fluid inlet/outlet (4-1) of a third PDMS substrate (4) and are used for timed 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

Mixing hexamethylenetetramine, polyethyleneimine, zinc nitrate hexahydrate and water according to the weight ratio of 1: 2-2.5: 4-4.5: 570-580, and adjusting the pH to 10-12 with ammonia water to obtain a zinc oxide growth solution;

2) cleaning of flow passages and through holes

Injecting deionized water into the straight flow channel (3-1) from the fluid inlet/outlet (4-1) through an injection pump, wherein the flow rate of the deionized water is 5-50 microliters/minute, and cleaning the flow channel and the through hole for 5-15 minutes;

3) injection of zinc oxide growth solution

Injecting a 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) to complete the renewal of the growth solution and realize the growth of the material;

4) synthesis of zinc oxide nano-rod

Continuously injecting a 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 nanorod with the patterned array structure at the cylindrical through hole (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 microliters/minute.