Patent Publication Number: US-2023158500-A1

Title: Array substrate, microfluidic device, microfluidic system, and fluorescence detection method

Description:
RELATED APPLICATIONS 
     The present application is a 35 U.S.C. 371 national stage application of PCT International Application No. PCT/CN2021/080444 filed on Mar. 12, 2021, the entire disclosure of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to the field of biomedical detection, and in particular to an array substrate, a microfluidic device comprising the array substrate, a microfluidic system comprising the microfluidic device, and a fluorescence detection method. 
     BACKGROUND 
     Polymerase Chain Reaction (PCR) is a molecular biology technique used to amplify specific deoxyribonucleic acid (DNA) fragments, which can replicate a small amount of DNA in large quantities and increase its number significantly. Digital polymerase chain reaction (dPCR) technology is a quantitative analysis technology developed on the basis of PCR that can provide digital DNA quantitative information, and greatly improves the sensitivity and accuracy in combination with the microfluidic technology. In the dPCR technology, the nucleic acid sample is sufficiently diluted so that the number of target molecules (i.e., DNA template) in each reaction unit is less than or equal to one. In each reaction unit, the target molecule is amplified through PCR, and after the amplification is completed, the fluorescent signal of each reaction unit is statistically analyzed, so as to realize the absolute quantitative detection of single-molecule DNA. Because dPCR has the advantages of high sensitivity, strong specificity, high detection throughput, accurate quantification, etc., it is widely used in various fields such as clinical diagnosis, gene instability analysis, single-cell gene expression, environmental microbial detection and prenatal diagnosis. 
     SUMMARY 
     According to an aspect of the present disclosure , an array substrate is provided. The array substrate comprises at least one recess. The array substrate is in a plane, and a ratio of an area of an orthographic projection of the at least one recess on the plane to an area of an orthographic projection of the array substrate on the plane is between 0.05 and 0.60. 
     In some embodiments, the array substrate further comprises a first substrate, a defining layer on the first substrate and defining the at least one recess, and a shielding layer defining at least one opening. An orthographic projection of the at least one opening on the first substrate at least partially overlaps an orthographic projection of the at least one recess on the first substrate, and an orthographic projection of the shielding layer on the first substrate at least partially overlaps an orthographic projection of the defining layer on the first substrate. 
     In some embodiments, the at least one recess penetrates the defining layer. 
     In some embodiments, the shielding layer is between the first substrate and the defining layer. 
     In some embodiments, the shielding layer is on a side of the first substrate away from the defining layer. 
     In some embodiments, the shielding layer comprises a first portion, the first portion is on a side of the defining layer away from the first substrate, and the first portion is attached to side surfaces of the defining layer and a surface of the defining layer away from the first substrate. The first portion defines the at least one opening. 
     In some embodiments, the shielding layer further comprises a second portion, the second portion is attached to a surface of the defining layer close to the first substrate to surround the defining layer together with the first portion. The second portion defines the at least one opening. 
     In some embodiments, an orthographic projection of the at least one opening defined by the first portion of the shielding layer on the first substrate and an orthographic projection of the at least one opening defined by the second portion of the shielding layer on the first substrate completely overlap. 
     In some embodiments, a surface of the defining layer close to the first substrate and/or a surface of the defining layer away from the first substrate constitute the shielding layer. 
     In some embodiments, a tangent to any point on a sidewall of the at least one recess is at an angle to the plane where the array substrate is located, and the angle is not equal to 90°. 
     In some embodiments, the defining layer defines a plurality of recesses, the shielding layer defines a plurality of openings, the plurality of recesses correspond to the plurality of openings one by one, and an orthographic projection of each of the plurality of openings on the first substrate is within an is orthographic projection of a recess corresponding to the opening on the first substrate. 
     In some embodiments, both a shape of an orthographic projection of each of the at least one recess and a shape of an orthographic projection of each of the at least one opening on the first substrate comprise a circle or a regular polygon. 
     In some embodiments, the defining layer defines a plurality of recesses, the shielding layer defines a plurality of openings, the plurality of recesses correspond to the plurality of openings one by one, and an orthographic projection of each of the plurality of openings on the first substrate is within an orthographic projection of a recess corresponding to the opening on the first substrate. Both a shape of an orthographic projection of each opening and a shape of an orthographic projection of a recess corresponding to the opening on the first substrate are circular, a diameter of each opening is in a range of 20-80 μm, and a diameter of the recess corresponding to the opening is in a range of 25-90 μm; or a shape of an orthographic projection of each opening on the first substrate is a first regular polygon, and a shape of an orthographic projection of the recess corresponding to the opening on the first substrate is a second regular polygon, a diameter of an inscribed circle of the first regular polygon is in a range of 20-80 μm, and a diameter of an inscribed circle of the second regular polygon is in a range of 25-90 μm. 
     In some embodiments, a material of the defining layer comprises photoresist. 
     In some embodiments, a material of the shielding layer comprises an opaque material, and the opaque material comprises chromium, chromium oxide, and black resin. 
     In some embodiments, a thickness of the shielding layer in a direction perpendicular to the first substrate is in a range of 0.6-2.4 μm. 
     In some embodiments, the array substrate further comprises a heating electrode between the first substrate and the defining layer, the heating electrode is configured to heat the at least one recess. 
     In some embodiments, a material of the heating electrode comprises is indium tin oxide. 
     In some embodiments, the heating electrode comprises a plurality of sub-parts separated from each other. 
     In some embodiments, the array substrate further comprises a conductive layer. The conductive layer is between the first substrate and the heating electrode and is electrically connected to the heating electrode; and an orthographic projection of at least a portion of the conductive layer on the first substrate falls on a periphery of an orthographic projection of the heating electrode on the first substrate, and the conductive layer at least partially surrounds the heating electrode. 
     In some embodiments, the array substrate further comprises a hydrophilic layer and a first hydrophobic layer. The hydrophilic layer covers at least a sidewall of the at least one recess; and the first hydrophobic layer is on a side of the defining layer away from the first substrate and farther away from the first substrate than the hydrophilic layer. 
     In some embodiments, the hydrophilic layer further covers a surface of the defining layer away from the first substrate and a bottom of the at least one recess. 
     In some embodiments, the first hydrophobic layer defines a plurality of holes, the defining layer defines a plurality of recesses, the shielding layer defines a plurality of openings, and the plurality of holes, the plurality of recesses, and the plurality of openings correspond one by one with each other. Both a first orthographic projection of each of the plurality of holes on the first substrate and a third orthographic projection of an opening corresponding to the hole on the first substrate are within a second orthographic projection of a recess corresponding to the hole on the first substrate, and the first orthographic projection, the second orthographic projection, and the third orthographic projection form concentric rings. The first orthographic projection is between the second orthographic projection and the third orthographic projection, and the third orthographic projection is within the first orthographic projection. 
     In some embodiments, a ratio of an area of the first hydrophobic layer to an area of the hydrophilic layer is between 0.01 and 2.00. 
     According to another aspect of the present disclosure, a microfluidic device is provided. The microfluidic device comprises the array substrate described in any of the previous embodiments, a counter substrate for assembling with the array substrate, and a space between the array substrate and the counter substrate. The counter substrate comprises a second substrate and a second hydrophobic layer on a side of the second substrate close to the first substrate. The counter substrate comprises at least one through hole penetrating the second substrate and the second hydrophobic layer. 
     In some embodiments, a material of the first substrate and the second substrate comprises glass. 
     In some embodiments, the second hydrophobic layer comprises a light-absorbing material, and the light-absorbing material comprises at least one of TiO 2  and TiON. 
     According to still another aspect of the present disclosure, a microfluidic system is provided. The microfluidic system comprises a control device and the microfluidic device described in any of the previous embodiments. The control device is electrically connected to the microfluidic device, and is configured to control the temperature of the microfluidic device. 
     According to yet another aspect of the present disclosure, a fluorescence detection method is provided. The fluorescence detection method comprises: containing a reagent to be tested in at least one recess of the microfluidic device described in any of the previous embodiments; making a light of a first wavelength emitted by a light source irradiate the at least one recess through at least one opening defined by the shielding layer; and detecting a light of a second wavelength emitted by the reagent to be tested. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to more clearly describe the technical solutions in the embodiments of the present disclosure, the following will briefly introduce the drawings that need to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work. 
         FIG.  1    illustrates a partial cross-sectional view of an array substrate according to an embodiment of the present disclosure; 
         FIG.  2    illustrates a partial cross-sectional view of an array substrate according to an embodiment of the present disclosure; 
         FIG.  3    illustrates a partial top plan view of a shielding layer and a defining layer defining recesses in an array substrate according to an embodiment of the present disclosure; 
         FIG.  4    illustrates a top plan view of a defining layer defining recesses in an array substrate according to an embodiment of the present disclosure; 
         FIG.  5    illustrates a top plan view of an array substrate according to an embodiment of the present disclosure; 
         FIG.  6    illustrates a top plan view of a portion of the structure in an array substrate according to an embodiment of the present disclosure; 
         FIG.  7    illustrates a partial cross-sectional view of an array substrate according to another embodiment of the present disclosure; 
         FIG.  8    illustrates a partial cross-sectional view of an array substrate according to still another embodiment of the present disclosure; 
         FIG.  9    illustrates a partial cross-sectional view of an array substrate according to yet another embodiment of the present disclosure; 
         FIG.  10    illustrates a partial cross-sectional view of a microfluidic device according to an embodiment of the present disclosure; 
         FIG.  11    illustrates a block diagram of a microfluidic system according to an embodiment of the present disclosure; 
         FIG.  12    illustrates a flowchart of a fluorescence detection method according to an embodiment of the present disclosure; 
         FIG.  13    illustrates a schematic diagram of a fluorescence detection process of a microfluidic device according to an embodiment of the present disclosure; 
         FIG.  14 A  illustrates a fluorescence picture of a microfluidic device in the related art after being irradiated by a light source; and 
         FIG.  14 B  illustrates a fluorescence picture of a microfluidic device according to an embodiment of the present disclosure after being irradiated by a light source. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     The technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a portion of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present disclosure. 
     Because the dPCR technology has the advantages of high sensitivity, strong specificity, high detection throughput, accurate quantification, etc., it is widely used in various fields such as clinical diagnosis, gene instability analysis, single-cell gene expression, environmental microbial detection and prenatal diagnosis. In the application of dPCR, after the PCR amplification of the reaction system solution in each reaction chamber in the microfluidic device is completed, it is usually necessary to use an excitation light of a certain wavelength to perform fluorescence detection on the reagent to be tested in each reaction chamber. However, the inventor(s) found that in a conventional microfluidic device, since the area occupied by all reaction chambers is much smaller than the area of the microfluidic device, that is, each reaction chamber has a very small volume, the amplification reaction cannot be fully performed on the reaction system solution in each reaction chamber and a small dose of the reagent to be tested is therefore obtained. Such a dose of the reagent to be tested, which is much lower than the required dose, cannot radiate the desired fluorescence intensity under the irradiation of the excitation light, which seriously affects the fluorescence detection accuracy of the reagent to be tested in the reaction chamber. As a result, the fluorescence detection results obtained cannot meet the diagnostic requirements of the biomedical field (such as single-cell analysis, early cancer diagnosis, and prenatal diagnosis). 
     It should be noted that in this specification, the “reagent to be tested” refers to the reagent after the polymerase chain reaction of the reaction system solution in the microfluidic device, that is, the reaction system reagent after the amplification reaction is completed. 
     Based on this, the embodiments of the present disclosure provide an array substrate, a microfluidic device, a microfluidic system, and a fluorescence detection method. The array substrate can improve the fluorescence detection accuracy of the reagent to be tested in the microfluidic device comprising the array substrate. 
     Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be noted that the same reference numerals in different drawings will be used to refer to the same elements. 
     According to an aspect of the present disclosure, an array substrate  100  is provided.  FIG.  1    illustrates a partial cross-sectional view of the array substrate  100 ,  FIG.  2    illustrates another cross-sectional view of the array substrate  100  ( FIG.  2    is a cross-sectional view taken along the line A-A′ of  FIG.  5   ), and  FIG.  3    illustrates a top plan view of a portion of the structure in the array substrate  100 . Referring to  FIGS.  1  to  3   , the array substrate  100  comprises at least one recess  103 , the array substrate  100  is located in a plane. A ratio of an area of an orthographic projection of the at least one recess  103  on the plane to an area of an orthographic projection of the array substrate  100  on the plane is between 0.05 and 0.60. For example, the ratio of the area of the orthographic projection of the at least one recess  103  on the plane to the area of the orthographic projection of the array substrate  100  on the plane may be 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60. It should be noted that, in this context, the “plane where the array substrate  100  is located” refers to the plane where the array substrate  100  as a whole is located, and the array substrate  100  extends in this plane. In some examples, the number of the at least one recess  103  may be 2,000 to  1 ,000,000. In some examples, the number of the at least one recess  103  may be 40,000 to 100,000. In one example, the number of the at least one recess  103  is 22,500. The shape of the orthographic projection of each recess  103  on the plane where the array substrate  100  is located can be any suitable shape such as a circle, an ellipse, a rectangle, a square, a triangle, a regular hexagon, a polygon (for example, a regular polygon), an irregular shape, etc. 
     The recess  103  is used to contain the reaction system solution (for example, DNA molecules), and the reagent to be tested is obtained after the quantity of the reaction system solution is amplified by the dPCR technology. The inventor(s) of the present application design(s) the area ratio of the plurality of recesses  103  to the array substrate  100  so that the two have an appropriate area ratio relationship. That is, the ratio of the area of the orthographic projection of the plurality of recesses  103  on the plane where the array substrate  100  is located to the area of the orthographic projection of the array substrate  100  on the plane is between 0.05 and 0.60, so that it is possible to make the array substrate  100  have an appropriate number of recesses  103  each with an appropriate chamber volume. In this way, the dPCR reaction can be fully performed on the reaction system solution contained in each recess  103  so as to improve the utilization ratio of the reaction system solution, so that more doses of the reagent to be tested can be obtained after amplification. Such dose of the reagent to be tested can radiate a desired fluorescence intensity under the irradiation of the excitation light, which can improve the fluorescence detection accuracy of the reagent to be tested, so that the obtained fluorescence detection result can meet the diagnostic requirements of the biomedical field (for example, single cell analysis, early cancer diagnosis and prenatal diagnosis). 
     Continuing to refer to  FIGS.  1  to  3   , the array substrate  100  further comprises: a first substrate  101 ; a defining layer  102  on the first substrate  101  and defining the aforementioned at least one recess  103 ; and a shielding layer  104  defining at least one opening  105 . An orthographic projection of the at least one opening  105  on the first substrate  101  at least partially overlaps an orthographic projection of the at least one recess  103  on the first substrate  101 , and an orthographic projection of the shielding layer  104  on the first substrate  101  at least partially overlaps an orthographic projections of the defining layer  102  on the first substrate  101 . 
     It should be noted that in this specification, phrases such as “the defining layer  102  defines the at least one recess  103 ” means that the defining layer  102  comprises or has at least one recess  103 , the recess  103  is formed by patterning the defining layer  102 , for example, a plurality of recesses  103  are obtained by digging the defining layer  102 . In addition, it should be noted that although the defining layer  102  and the shielding layer  104  are described in this specification, the defining layer  102  and the shielding layer  104  may be two independent film structures or the same film structure. In some embodiments, the defining layer  102  and the shielding layer  104  are two independent film structures, the defining layer  102  is formed of a film layer with a suitable material, and the shielding layer  104  is formed of another film layer with light-shielding property. In an alternative embodiment, the defining layer  102  and the shielding layer  104  are the same film structure, for example, a portion of the defining layer  102  (for example, a surface of the defining layer  102  close to the first substrate  101  and/or a surface of the defining layer  102  away from the first substrate  101 ) is physically or chemically treated to make it opaque, so that the portion of the defining layer  102  serves as the shielding layer  104 ; and the remaining untreated portion of the defining layer  102  continues to play the role of the defining layer  102 . 
     The excitation light of a certain wavelength is irradiated to the recess  103  through the opening  105  defined by the shielding layer  104  in the direction from the bottom to the top (that is, the direction from the first substrate  101  to the defining layer  102  in  FIG.  1   ), so that the reagent with fluorescent property in the recess  103  is excited and emits a fluorescent spectrum. Due to its inherent material property, the defining layer  102  in the array substrate  100  usually emits undesirable fluorescence after being irradiated by the excitation light. However, in the embodiment of the present disclosure, by providing the shielding layer  104  and making the orthographic projection of the shielding layer  104  on the first substrate  101  at least partially overlap the orthographic projection of the defining layer  102  on the first substrate  101 , when excitation light is irradiated to the recess  103  through the opening  105 , the shielding layer  104  can at least partially shield the defining layer  102  from being irradiated by the excitation light, thereby preventing the defining layer  102  from being irradiated by the excitation light and causing interference fluorescence. In this way, the excitation light can only excite the reagent to be tested in the recess  103  through the opening  105 . Therefore, through this arrangement, the fluorescence interference caused by the defining layer  102  can be reduced or even avoided, so that the fluorescent signal emitted by the reagent to be tested in the recess  103  can be accurately identified by the detector and the reaction signal can be read more sensitively and accurately, the fluorescence detection accuracy of the reagent to be tested can be improved, and image data support for subsequent nucleic acid amplification reaction data analysis is provided. In addition, through such an arrangement, clearer micro-hole array imaging can be achieved, detection errors caused by false positives can be reduced, and interference between different channels in the process of multi-channel fluorescence signal detection can be well avoided. 
     It should be noted that “a reagent with fluorescent property” means that when the reagent is irradiated by excitation light of a specific wavelength, it will emit fluorescence with a longer wavelength than the excitation light in a short period of time. Under the irradiation of the excitation light of the specific wavelength, the reagent is easier to emit fluorescence than other films in the array substrate  100 . 
     The first substrate  101  protects and supports the array substrate  100 . The first substrate  101  may be made of any suitable material, for example, a rigid material or a flexible material. The rigid or flexible material comprises but is not limited to, glass, ceramic, silicon, polyimide, and other materials. In an example, the first substrate  101  is made of glass, and the glass material can reduce the surface roughness of the first substrate  101  and facilitate the movement of the reaction solution (for example, liquid droplets) on the surface of the corresponding film layer. 
     The defining layer  102  can be made of any suitable material. In some embodiments, the material of the defining layer  102  is photoresist. The photoresist may be formed on the first substrate  101  by any suitable method (for example, spin coating), and be patterned to form the defining layer  102 . The defining layer  102  generally has a relatively thick thickness. In an example, the thickness of the defining layer  102  may range from 5 microns to 100 microns, for example, 9.8 microns. The defining layer  102  defines a plurality of recesses  103 , and the plurality of recesses  103  are spaced apart from each other. Each recess  103  may penetrate the defining layer  102  or not completely penetrate the defining layer  102 . In the latter case, a portion of the defining layer  102  is formed at the bottom of the recess  103 . In the embodiment of the present disclosure, the recess  103  may penetrate the defining layer  102 . In this way, when the excitation light is irradiated to the recess  103  through the opening  105 , it can be directly irradiated to the reagent in the recess  103 , so that the fluorescence detection accuracy of the reagent can be further improved. The recess  103  provides a containing space for the reaction system solution, and the reaction system solution that moves into the recess  103  stays in the recess  103  in a relatively stable manner. For example, the recess  103  may be a groove, a notch, a micro-hole, etc., as long as it has a space capable of accommodating the reaction system solution, which is not limited in the embodiment of the present disclosure. 
     The shapes of the plurality of recesses  103  may be completely the same, or may be partially different. In some embodiments, the shape of the orthographic projection of each recess  103  on the first substrate  101  is a circle. The three-dimensional shape of each recess  103  is, for example, an approximate cylinder, that is, the cross section in the direction perpendicular to the first substrate  101  is an approximate rectangle and the cross section on a plane parallel to the first substrate  101  is an approximate circle. In some embodiments, the diameter of the bottom surface of the cylinder ranges from 1 micron to 100 microns, for example, from 20 microns to 50 microns, or from 50 microns to 90 microns. The height of the cylinder ranges from 5 microns to 100 microns, for example, from 30 microns to 50 microns. For example, in some examples, the diameter of the bottom surface of the cylinder is about 50 microns, the height of the cylinder is in the range of 40 to 50 microns, and the distance between the centers of two adjacent recesses  103  is about 100 microns. 
     The shape of the recesses  103  can be designed according to actual requirements. For example, the shape of each recess  103  can also be a truncated cone, a rectangular parallelepiped, a polygonal prism, a sphere, an ellipsoid, etc., which are not limited in the embodiments of the present disclosure. For example, the cross-sectional shape of the recess  103  on a plane parallel to the first substrate  101  may be an ellipse, a triangle, a polygon, an irregular shape, etc., and the cross-section in a direction perpendicular to the first substrate  101  may be a square, circle, parallelogram, trapezoid and other polygons. 
     In some embodiments, a tangent to any point on the sidewall of each recess  103  is at a certain angle to the plane where the array substrate  100  is located, and the angle is not equal to 90°. In other words, the sidewall of each recess  103  is not perpendicular to the plane where the array substrate  100  is located, but has a certain inclination. The inclination angle may be, for example, an acute angle (greater than 0° and less than 90°) or an obtuse angle (greater than 90° and less than 180°). In an example, as illustrated in  FIG.  1   , the sidewall of the recess  103  is at an obtuse angle to the plane where the array substrate  100  is located, and the inclination angle of the sidewall makes the area of the bottom of the recess  103  smaller than the area of the upper opening corresponding to the bottom. Of course, the shape of the recess  103  is not limited to this. In another example, the sidewall of the recess  103  is at an acute angle to the plane where the array substrate  100  is located, and the inclination angle of the sidewall makes the area of the bottom of the recess  103  larger than the area of the upper opening corresponding to the bottom. By designing the sidewall of the recesses  103  in this way, each recess  103  can obtain a larger volume in a limited space, so that each recess  103  can contain more reaction system solution. More doses of the reagent to be tested are obtained after the amplification reaction, the fluorescence emission intensity of the reagent to be tested is increased, and the fluorescence detection accuracy of the reagent to be tested can be improved. 
     It should be noted that all the inner walls surrounding the recess  103  can be referred to as the sidewall of the recess  103 . As illustrated in  FIGS.  2  and  3   , the sidewall of the recess  103  is adjacent to the defining layer  102 , and the height of the sidewall of the recess  103  in the direction perpendicular to the first substrate  101  is substantially the same as the height of the defining layer  102  in the direction perpendicular to the first substrate  101 . The sidewall of the recess  103  and the bottom of the recess  103  constitute a reaction chamber of the recess  103  to contain the reagent to be tested. In addition, it should be noted that the sidewall of the recess  103  may be an inclined surface, an arc-shaped surface, or a curved surface with any curvature (for example, a varying curvature). The embodiment of the present disclosure does not specifically limit the shape of the sidewall of the recess  103 . 
       FIG.  3    illustrates a top plan view of the shielding layer  104  and the defining layer  102  defining the recess  103  in  FIG.  2   , and  FIG.  4    illustrates a top plan view of the defining layer  102  defining the recess  103  in the array substrate  100 . Each small circle in  FIG.  4    represents a recess  103 . As illustrated in  FIG.  3    and  FIG.  4   , a plurality of recesses  103  are uniformly distributed on the first substrate  101 . For example, on the first substrate  101 , a plurality of recesses  103  are arranged in an array along the horizontal direction and the vertical direction. In this way, the fluorescence images obtained during the optical detection of the microfluidic device containing the array substrate  100  in the subsequent stage can be more regular and tidy, so that the detection result can be obtained quickly and accurately. Of course, the embodiment of the present disclosure is not limited to this, and the plurality of recesses  103  may also be unevenly distributed on the first substrate  101 , or arranged in other manners, which is not limited in the embodiment of the present disclosure. The number of the recesses  103  may be 2,000 to 1,000,000. In some examples, the number of the recesses  103  is 40,000 to 100,000. In an example, the number of the recesses  103  is 22,500. Therefore, the array substrate  100  has a high detection throughput. 
     It should be noted that in the embodiments of the present disclosure, the size and number of the recesses  103  may be determined according to actual requirements, and the size and number of the recesses  103  are related to the sizes of the first substrate  101  and the array substrate  100 . When the size of the recess  103  is unchanged, the larger the number of the recesses  103 , the larger the sizes of the first substrate  101  and the array substrate  100 . 
     Since the target molecule (i.e., DNA molecule) in the reaction system solution is fully diluted, when the reaction system solution enters each recess  103 , the number of the target molecule in each recess  103  is less than or equal to 1, that is, each recess  103  comprises only one target molecule or does not comprise the target molecule, so that accurate detection results can be obtained in the subsequent stage. 
     As illustrated in  FIGS.  1  and  2   , the shielding layer  104  is located between the first substrate  101  and the defining layer  102 . In an example, the shielding layer  104  is attached to the bottom surface of the defining layer  102  facing the first substrate  101 . In an example, the orthographic projection of the defining layer  102  on the first substrate  101  completely falls within the orthographic projection of the shielding layer  104  on the first substrate  101 , as illustrated in  FIG.  3   . With this arrangement, the excitation light incident through the opening  105  will not irradiate the defining layer  102 . The shielding layer  104  may be made of any suitable material as long as the material can shield or absorb light. The embodiment of the present disclosure does not specifically limit the material of the shielding layer  104 . In some embodiments, the material of the shielding layer  104  is an opaque material, and the opaque material may be, for example, an opaque metal. In some examples, the material of the shielding layer  104  is a black matrix (BM) commonly used in the display field, and the material of the black matrix comprises one or more of chromium, chromium oxide, and black resin. In some examples, the thickness of the shielding layer  104  in a direction perpendicular to the first substrate  101  is in the range of 0.6 microns to 2.4 microns, for example, 2 microns. 
     The shielding layer  104  defines a plurality of openings  105 , and the plurality of openings  105  correspond to the plurality of recesses  103  one by one, and the orthographic projection of each opening  105  on the first substrate  101  is within the orthographic projection of a recess  103  corresponding to the opening  105  on the first substrate  101 . That is, the area of the orthographic projection of each opening  105  on the first substrate  101  is smaller than the area of the orthographic projection of a recess  103  corresponding to the opening  105  on the first substrate  101 . Through this arrangement, in the subsequent fluorescence detection, the excitation light can only be irradiated to the recess  103  through the opening  105 , but not to the area around the recess  103 , so that the interference of the film(s) in the surrounding area near the recess  103  (for example, a portion of the defining layer  102 ) on the fluorescence detection can be avoided. In actual product design, the size of the opening  105  of the shielding layer  104  can be correspondingly designed according to the size of the irradiation spot of the incident excitation light, the thickness of the defining layer  102 , and the like. It should be noted that terms such as “a plurality of A correspond to a plurality of B one by one” mean that the number of A is equal to the number of B, and each A corresponds to one B, and the orthographic projection of each A on the first substrate  101  at least partially overlaps the orthographic projection of a B corresponding to the A on the first substrate  101 . In some embodiments, the shape of each opening  105  and the shape of the recess  103  corresponding to the opening  105  may be the same or different. The shape of the opening  105  may be a cylindrical, a truncated cone, a rectangular parallelepiped, a polygonal prism, a sphere, an ellipsoid, etc., which is not limited in the embodiments of the present disclosure. For example, the cross-sectional shape of the opening  105  on a plane parallel to the first substrate  101  may be an ellipse, a triangle, a polygon, an irregular shape, etc., and the cross-section in a direction perpendicular to the first substrate  101  may be a square, a circle, a parallelogram, a trapezoid, or other polygons. In an example, both the shape of the orthographic projection of each opening  105  and the shape of the orthographic projection of a corresponding recess  103  on the first substrate  101  are circular, and the diameter of each opening  105  is in the range of 20 to 80 microns, and the diameter of a recess  103  corresponding to the opening  105  is in the range of 25 to 90 microns. It should be noted that the diameter of the opening  105  is smaller than the diameter of the recess  103  corresponding to the opening  105 . For example, if the diameter of the opening  105  is 20 microns, the diameter of the corresponding recess  103  may be 25 microns; if the diameter of the opening  105  is 60 microns, the diameter of the corresponding recess  103  may be 70 microns; if the diameter of the opening  105  is 80 microns, the diameter of the corresponding recess  103  may be 90 microns, etc. In another example, the shape of the orthographic projection of each opening  105  on the first substrate  101  is a first regular polygon, and the shape of the orthographic projection of a recess  103  corresponding to the opening  105  on the first substrate  101  is a second regular polygon, the diameter of the inscribed circle of the first regular polygon is in the range of 20 to 80 μm, and the diameter of the inscribed circle of the second regular polygon is in the range of 25 to 90 μm. It should be noted that the diameter of the inscribed circle of the first regular polygon is smaller than the diameter of the inscribed circle of the second regular polygon. For example, if the diameter of the inscribed circle of the first regular polygon is 20 microns, the diameter of the inscribed circle of the second regular polygon may be 25 microns; if the diameter of the inscribed circle of the first regular polygon is 60 microns, the diameter of the inscribed circle of the second regular polygon may be 70 microns; if the diameter of the inscribed circle of the first regular polygon is 80 microns, the diameter of the inscribed circle of the second regular polygon may be 90 microns, etc. By making the shape of the opening  105  and the recess  103  substantially the same and making the diameter of the opening  105  smaller than the diameter of the recess  103 , the excitation light can be irradiated to the recess  103  at a higher utilization ratio, and as described above, only the recess  103  can be irradiated, and the surrounding area of the recess  103  will not be irradiated. 
     Since the shielding layer  104  is located between the first substrate  101  and the defining layer  102 , the orthographic projection of the shielding layer  104  on the first substrate  101  necessarily at least partially overlaps the first substrate  101  per se, that is, the shielding layer  104  necessarily shields at least a portion of the first substrate  101 . Therefore, when the excitation light is irradiated to the recess  103  through the opening  105  in the direction from bottom to top, the shielding layer  104  can not only block the excitation light from irradiating the defining layer  102 , but also block the excitation light irradiated on the first substrate  101  from being transmitted through the shielding layer  104 , so as not only to prevent the defining layer  102  from emitting undesired fluorescence, but also to at least partially reduce the slight fluorescence interference (possibly) generated by the first substrate  101  when it is irradiated by the excitation light. This further improves the fluorescence detection accuracy of the reagent in the recess  103 . 
     Although the foregoing embodiment is described with the defining layer  102  and the shielding layer  104  as two separate film structures, as mentioned above, the defining layer  102  and the shielding layer  104  may also be the same film structure. In the embodiment where the defining layer  102  and the shielding layer  104  have the same film structure, the surface of the defining layer  102  close to the first substrate  101  (that is, the lower surface of the defining layer  102 ) is physically or chemically treated to make it opaque, so that the lower surface of the defining layer  102  serves as the shielding layer  104 . The remaining untreated portion of the defining layer  102  continues to function as the defining layer  102 . When the recess  103  penetrates the defining layer  102  (that is, the recess  103  is a structure similar to a through hole), the opening at the bottom of the recess  103  is equivalent to the opening  105  of the shielding layer  104 ; when the recess  103  does not completely penetrate the defining layer  102  (that is, the recess  103  is a structure similar to a blind hole), by processing the lower surface of the defining layer  102 , an opening is formed at a position corresponding to the recess  103 , which is equivalent to the opening  105  of the shielding layer  104 . 
     During the dPCR reaction, the double-stranded structure of the DNA fragment is denatured to form a single-stranded structure at a high temperature (for example, 90° C.). At a low temperature (for example, 65° C.), the primer and the single strand are combined according to the principle of base complementary pairing and achieve base-binding extension at the most suitable temperature (for example, 72° C.) for the DNA polymerase, the above process is the temperature cycle of denaturation-annealing-extension. Through multiple temperature cycles of denaturation-annealing-extension, DNA fragments can be replicated in large numbers. 
     In order to realize the above-mentioned temperature cycling process, a series of external devices are usually used to heat and cool the microfluidic device comprising the array substrate  100 , which makes the device bulky, complicated to operate, and costly. Moreover, in the process of heating and cooling the microfluidic device, the overall temperature of the microfluidic device changes accordingly, so that in addition to the recess  103  which contains the DNA fragments, the temperature of other structures and components in the microfluidic device also changes. This change increases the risk of damage to components such as circuits. In addition, since tens of thousands to hundreds of thousands of recesses  103  are usually distributed in the microfluidic device, the phenomenon of uneven temperature at each recess  103  may occur during heating the microfluidic device, for example, the temperature in the middle area of the reaction area (which is composed of the plurality of recesses  103 ) is high while the temperature in the edge area of the reaction area is low, which will affect the entire dPCR process and make the final detection result of the reagent inaccurate. 
     In order to solve the above-mentioned problems, as illustrated in  FIGS.  1  and  2   , the array substrate  100  further comprises a heating electrode  106  located between the first substrate  101  and the defining layer  102 , and the heating electrode  106  is configured to heat the plurality of recesses  103 . 
     The heating electrode  106  is located on the first substrate  101 , and the heating electrode  106  can receive an electrical signal (such as a voltage signal), so that when a current flows through the heating electrode  106 , heat is generated, and the heat is conducted to the recess  103  for polymerase chain reaction. For example, the heating electrode  106  can be made of a conductive material with a large resistivity, so that the heating electrode  106  can generate a large amount of heat when provided with a small electrical signal, so as to increase the power conversion efficiency. The heating electrode  106  may be made of, for example, a transparent conductive material, such as indium tin oxide (ITO), tin oxide, etc., or may be made of other suitable materials, such as metal, which is not limited in the embodiments of the present disclosure. 
     As illustrated in the figure, the orthographic projection of the plurality of recesses  103  on the first substrate  101  is located within the orthographic projection of the heating electrode  106  on the first substrate  101 . Here, the orthographic projection refers to the projection on the first substrate  101  in a direction perpendicular to the first substrate  101 . For example, as illustrated in  FIG.  2   , in the direction perpendicular to the first substrate  101 , the orthographic projection of the plurality of recesses  103  on the first substrate  101  is located within the orthographic projection of the heating electrode  106  on the first substrate  101 , and the orthographic projection of the heating electrode  106  is larger than the orthographic projection of the plurality of recesses  103 . In this way, the heating electrode  106  can heat each recess  103 . Due to the edge heat dissipation effect of the heating electrode  106 , the operating temperature at the edge of the heating electrode  106  is generally lower than the operating temperature at the center area of the heating electrode  106 . By making the above-mentioned projection of the heating electrode  106  larger than the above-mentioned projection of the plurality of recesses  103 , the central area of the heating electrode  106  having a uniform temperature corresponds to the plurality of recesses  103  and heats the plurality of recesses  103 , so as to prevent the plurality of recesses  103  from being heated by the edge of the heating electrode  106  (for example, an area 5 mm, 8 mm or other suitable size from the edge), so that the heating of the plurality of recesses  103  is more uniform and the temperature uniformity is better, which in turn facilitates the effective amplification reaction of the reaction system solution in the recesses  103 . 
       FIG.  5    illustrates a top plan view of the array substrate  100 . As illustrated in the figure, the heating electrode  106  comprises a plurality of sub-parts which are separated from each other and extending in a first direction X (i.e., the vertical direction in the figure). The figure illustrates five sub-parts which are separated and insulated from each other, but the embodiments of the present disclosure are not limited to this, the heating electrode  106  may comprise more or less separated sub-parts, such as two separated sub-parts, ten separated sub-parts, one hundred separated sub-parts, etc. The embodiments of the present disclosure do not limit the spacing between the adjacent sub-parts, as long as the product design requirements are met. In an example, the spacing between each sub-part of the heating electrode  106  is in the range of 1 micron to 200 microns. By applying electrical signals to each sub-part of the heating electrode  106  respectively, for example, applying a high voltage to one end of each sub-part, and applying a low voltage (for example, a ground signal) to the other end of each sub-part, the separated sub-parts of the heating electrode  106  flow substantially the same amount of current, and therefore maintain substantially the same temperature, thereby further improving the temperature uniformity of the heating electrode  106 , so that the heating of the plurality of recesses  103  is more uniform, and the temperature uniformity is better, which in turn facilitates the amplification reaction of the reaction system solution in the recesses  103 . 
     In  FIG.  5   , each sub-part of the heating electrode  106  is illustrated as an elongated rectangle, but the embodiment of the present disclosure does not limit the shape of each sub-part of the heating electrode  106 , which may be any appropriate shape. For example,  FIG.  6    illustrates another possible planar shape of each sub-part of the heating electrode  106 . As illustrated in the figure, the heating electrode  106  comprises a plurality of strip-like structures that extend along the first direction X and are separated from each other. The width of the middle part of each strip structure in the second direction Y is wider than the width of the two end parts of the strip structure in the second direction Y. The second direction Y is a direction perpendicular to the first direction X in a plane parallel to the first substrate  101 . Of course, the plurality of strip structures in the heating electrode  106  are not limited to the shapes illustrated at the left side of  FIG.  6   , as long as the strip structure has a shape such that the width of the middle portion is wider than the width of the two end portions. For example, as illustrated at the right side of  FIG.  6   , the shape of the strip structure of the heating electrode  106  may also be an ellipse or a rectangle with an edge profile in the shape of a broken line. 
     In the embodiment of the present disclosure, by arranging the heating electrode  106  in the array substrate  100  (for example, integrating the heating electrode  106  on the first substrate  101 ), the heating of the recess  103  of the array substrate  100  can be effectively realized, thereby realizing the temperature control of the recess  103  without external heating equipment and with high integration. By arranging the heating electrode  106  as a plurality of sub-parts separated from each other, the heating electrode  106  can be maintained at substantially the same temperature everywhere, thereby further improving the temperature uniformity of the heating electrode  106  and making the heating of the plurality of recesses  103  more uniform. In addition, compared to some array substrates that need to drive liquid droplets to move through regions of multiple temperatures in order to be heated, the array substrate  100  can realize temperature cycling without driving the liquid droplets, and has simple operation and low production cost. 
     Returning to continue referring to  FIGS.  1  and  2   , the array substrate  100  further comprises a conductive layer  107  and a first insulating layer  110 . The conductive layer  107  is located between the first substrate  101  and the heating electrode  106 , and the first insulating layer  110  is located between the conductive layer  107  and the heating electrode  106 , the conductive layer  107  is electrically connected to the heating electrode  106  through the via  112  in the first insulating layer  110 . The conductive layer  107  is configured to apply an electric signal (for example, a voltage signal) to the heating electrode  106 . After the heating electrode  106  receives the electrical signal, it can generate heat under the action of the electrical signal, thereby heating the recess  103 . It should be noted that the first insulating layer  110  may also cover a portion of the first substrate  101  that is not overlapped by the conductive layer  107 . 
     The via  112  exposes a portion of the conductive layer  107  so that the heating electrode  106  can be electrically connected to the conductive layer  107  through the via  112 . The shape of the via  112  may be cylindrical, truncated cone, or the like. For example, the conductive layer  107  may be electrically connected to the heating electrode  106  through one or more vias  112 . When the electrical connection is achieved through a plurality of vias  112 , the connection resistance can be effectively reduced, and the energy loss can be reduced. When the electrical connection is achieved through one via  112 , the production process can be simplified. 
     The number of conductive layer  107  may be one or more, which is not limited in the embodiment of the present disclosure. When a plurality of conductive layers  107  are used to apply electrical signals to the heating electrode  106 , different portions of the heating electrode  106  can receive the electrical signal at the same time, so that substantially the same amount of current flows through each position of the heating electrode  106 , so the heating is more uniform. For example, when there are a plurality of conductive layers  107 , the first insulating layer  110  may comprise a plurality of vias  112 , and each via  112  exposes a portion of the conductive layer  107 , so that the heating electrode  106  is electrically connected to the plurality of conductive layers  107  respectively through the plurality of vias  112 . For example, the plurality of conductive layers  107  and the plurality of vias  112  correspond one by one. For another example, the number of the plurality of vias  112  may also be greater than the number of the plurality of conductive layers  107 , and each conductive layer  107  is electrically connected to the heating electrode  106  through one or more vias  112 . 
     It should be noted that in the embodiments illustrated in  FIGS.  1  and  2   , the heating electrode  106  and the conductive layer  107  are located in different layers. In some other embodiments, the heating electrode  106  and the conductive layer  107  may also be located in the same layer. In this case, the first insulating layer  110  may be omitted from the array substrate  100 , and the heating electrode  106  is directly electrically connected to the conductive layer  107 . 
     The resistance value of the heating electrode  106  is greater than the resistance value of the conductive layer  107 , so that under the same electrical signal, the heating electrode  106  generates more heat to heat the recess  103 . The conductive layer  107  generates less heat, thereby reducing energy loss. For example, the conductive layer  107  may use a material with a small resistivity, so as to reduce the energy loss on the conductive layer  107 . The conductive layer  107  may be made of a metal material. The metal material may be copper or copper alloy, aluminum or aluminum alloy, etc., and may be a single metal layer or a composite metal layer, which is not limited in the embodiments of the present disclosure. 
     In some embodiments of the present disclosure, the heating electrode  106  is made of indium tin oxide (ITO) or tin oxide, and the conductive layer  107  is made of a metal material. Since ITO is not easily oxidized, it can prevent the oxidation of the portion of the heating electrode  106  exposed to the air, thereby avoiding problems such as uneven heating or increased power consumption caused by the oxidation of the heating electrode  106 . The conductive layer  107  is covered by the first insulating layer  110 , so even if it is made of a metal material, the problem of oxidation is unlikely to occur. 
     Referring to  FIG.  5   , the vias  112  in the first insulating layer  110  comprise a first plurality of vias  112   a  and a second plurality of vias  112   b . The first set of vias  112   a  and the second set of vias  112   b  are respectively located on opposite sides of the array substrate  100 . The conductive layer  107  comprises a first set of conductive layers  1071  and a second set of conductive layers  1072 . The first set of conductive layers  1071  and the first set of vias  112   a  are located on the same side. The first set of conductive layers  1071  are electrically connected to the heating electrode  106  through the first set of vias  112   a.  The orthographic projection of the second set of conductive layers  1072  on the first substrate  101  falls on the periphery of the orthographic projection of the heating electrode  106  on the first substrate  101 , and the second set of conductive layers  1072  at least partially surround the heating electrode  106 . The second set of conductive layers  1072  are electrically connected to the heating electrode  106  through the second set of vias  112   b.  Through this arrangement, the conductive layer  107  can at least partially surround the heating electrode  106 , the heat loss of the heating electrode  106  can be reduced, the temperature of each recess  103  can be more uniform, and the heating efficiency of the heating electrode  106  can be improved, thereby reducing the power consumption. 
     In a conventional array substrate, a high voltage signal is usually applied to the heating electrode through only one conductive layer, and a low voltage signal (such as a ground voltage) is applied to the heating electrode through the other conductive layer, so as to form, for example, a current path along the first direction on the heating electrode, which causes the heating electrode to generate heat. Since the heating electrode itself has a large resistance value, a large voltage drop will be generated at the junction between the heating electrode and the conductive layer in the second direction perpendicular to the first direction, so that the heating electrode can be divided into a first electrode and a second electrode distributed in the second direction. The first electrode receives a relatively large voltage signal. The first electrode is, for example, the part of the electrode at the junction of the heating electrode and the conductive layer. The second electrode receives a relatively small voltage signal. The second electrode is, for example, the part of the electrode that is away from the above-mentioned junction in the second direction. Correspondingly, the current in the heating electrode is not uniform, the current in the first electrode is relatively large and the heat generated is relatively large, and the current in the second electrode is relatively small and the heat generated is relatively small. Therefore, when such heating electrode is used to heat the recesses in the array substrate, the recesses at different positions have different temperatures, which ultimately affects the amplification reaction of the reaction system solution in the recesses, and hence affects the accuracy of the detection effect. 
     In the embodiment of the present disclosure, the first plurality of conductive layers  1071  (two are illustrated in the figure) apply a first voltage signal (for example, a high voltage signal) to the heating electrode  106  through the first set of vias  112   a.  The second plurality of conductive layers  1072  (two are illustrated in the figure) apply a second voltage signal (for example, a ground signal) to the heating electrode  106  through the second set of vias  112   b  to form a current path on the heating electrode  106 . By arranging such a plurality of sets of conductive layers and each set containing a plurality of conductive layers, and in combination with the heating electrode  106  which is divided into a plurality of separate sub-parts, it is possible to make one end of each sub-part of the heating electrode  106  (an end close to the first set of vias  112   a ) be simultaneously applied with the same first voltage signal, and the other end of each sub-part of the heating electrode  106  (an end close to the second set of vias  112   b ) be simultaneously applied with the same second voltage signal, thereby a uniform current is formed in the heating electrode  106  and uniform heat is generated, so that the recesses  103  at different positions reach a uniform temperature, the amplification reaction of the reaction system solution in the recesses  103  is promoted, and the accuracy of the detection effect is improved. 
     In order to facilitate the electrical connection of the conductive layer  107  with an external device (not illustrated) independent of the array substrate  100  to receive electrical signals (such as voltage signals), the array substrate  100  may further comprise a contact  113  (as illustrated in  FIG.  5   , for example, the pad area), the contact  113  is not covered by the first insulating layer  110 . For example, the contact  113  has a large square shape, so that it can be easily contacted and connected with a probe or electrode in an external device, and has a large contact area, so it can stably receive electrical signals. In this way, the array substrate  100  can be plug and play, simple to operate, and convenient to use. For example, the contact  113  may be located on the same layer as the conductive layer  107  and formed by a single patterning process. When the conductive layer  107  is made of a metal material, the contact  113  can be electroplated, thermal sprayed, or vacuum-plated to form a metal protective layer on the surface of the contact  113  to prevent the contact  113  from being oxidized without affecting its electrical conductivity. 
     Continuing to refer to  FIG.  5   , the array substrate  100  comprises a reaction area  1001  and a peripheral area  1002 , and the peripheral area  1002  at least partially surrounds the reaction area  1001 . In some embodiments, in the first direction X, the peripheral area  1002  comprises a first sub-area  1002   a  and a second sub-area  1002   b  respectively located on both sides of the reaction area  1001 . In other embodiments, the peripheral area  1002  completely surrounds the reaction area  1001 , that is, the peripheral area  1002  is ring-shaped and surrounds the reaction area  1001 . In this case, in the first direction X, the peripheral area  1002  comprises a first sub-area  1002   a  and a second sub-area  1002   b  respectively located on both sides of the reaction area  1001 , and in the second direction Y, the peripheral area  1002  also comprises a third sub-area and a fourth sub-area respectively located on both sides of the reaction area  1001 , the first sub-area  1002   a  is connected with the third sub-area and the fourth sub-area, and the second sub-area  1002   b  is also connected with the third sub-area and the fourth sub-area, so that the peripheral area  1002  surrounds the reaction area  1001 . 
     As illustrated in  FIG.  5   , the vias  112  are located in the peripheral area  1002 , and the heating electrode  106  is at least partially located in the reaction area  1001 . In some embodiments, the reaction area  1001  further comprises a functional area  1001   a,  and the recesses  103  are located in the functional area  1001   a.  For example, the orthographic projection of the heating electrode  106  on the first substrate  101  completely covers the functional area  1001   a  of the reaction area  1001 , that is, the functional area  1001   a  is located within the orthographic projection of the heating electrode  106  on the first substrate  101 , thereby ensuring that the heating electrode  106  can heat each recess  103 . 
     It should be noted that when the peripheral area  1002  further comprises the third sub-area and the fourth sub-area located on both sides of the reaction area  1001  in the second direction Y, the third sub-area and the fourth sub-area may also provide a plurality of conductive layers  107 . The embodiments of the present disclosure do not impose restrictions on the number, placement positions, etc. of the conductive layers  107 . 
     Returning to continue referring to  FIGS.  1  and  2   , the array substrate  100  may further comprise a hydrophilic layer  108  covering at least the sidewall of each recess  103 . In some embodiments, the hydrophilic layer  108  covers the sidewall of each recess  103 . In an alternative embodiment, the hydrophilic layer  108  not only covers the sidewall of each recess  103 , but also covers the surface of the defining layer  102  away from the first substrate  101  and the bottom of each recess  103 . In the embodiment where the recess  103  penetrates the defining layer  102  (that is, the recess  103  is a through-hole structure), the hydrophilic layer  108  covers the sidewall of the recess  103 . In the embodiment where the recess  103  does not completely penetrate the defining layer  102  (that is, the recess  103  is a blind hole structure), the hydrophilic layer  108  covers the sidewall and bottom of the recess  103 . The hydrophilic layer  108  has the characteristics of being hydrophilic and oleophobic. Since the sidewall (and bottom) of the recess  103  is provided with the hydrophilic layer  108 , the hydrophilicity of the recess  103  is greatly improved, and the contact angle between the droplets in the reaction system solution and the surface of the recess  103  is relatively small. When no driving force is exerted on the reaction system solution from the outside, the reaction system solution can automatically gradually enter each recess  103  based on the capillary phenomenon, thereby realizing automatic sampling and avoiding cross-flow. 
     In some embodiments, the material of the hydrophilic layer  108  is silicon oxide, such as silicon dioxide (SiO 2 ). Of course, the embodiments of the present disclosure are not limited to this, and the hydrophilic layer  108  can also be made of other suitable inorganic or organic materials, as long as the surface of the hydrophilic layer  108  away from the defining layer  102  is hydrophilic. In some embodiments, the hydrophilic layer  108  may be directly prepared using hydrophilic materials. In other embodiments, the hydrophilic layer  108  may be made of a material that is not hydrophilic. In this case, it is necessary to perform a hydrophilic treatment on the surface of the hydrophilic layer  108  away from the defining layer  102 , so that the surface of the hydrophilic layer  108  away from the defining layer  102  has hydrophilicity. If a non-hydrophilic material (such as silicon nitride, etc.) is used to prepare the hydrophilic layer  108 , the non-hydrophilic material can be hydrophilized, for example, gel modification, ultraviolet radiation, plasma method and other methods may be selected to make the surface of the non-hydrophilic material have a hydrophilic group, thereby having hydrophilicity. 
     As illustrated in  FIGS.  1  and  2   , the array substrate  100  may also comprise a first hydrophobic layer  109  on a side of the hydrophilic layer  108  away from the first substrate  101 , and a portion of the hydrophilic layer  108  (that is, the portion of the hydrophilic layer  108  that covers the surface of the defining layer  102  away from the first substrate  101 ) is located between the first hydrophobic layer  109  and the defining layer  102 . The first hydrophobic layer  109  covers the surface of the hydrophilic layer  108  (on the defining layer  102 ) away from the first substrate  101  and extends to the boundary between the surface and the sidewall of the recess  103 , so that the first hydrophobic layer  109  defines a plurality of holes  114 . In an example, the plurality of recesses  103  defined by the defining layer  102 , the plurality of openings  105  defined by the shielding layer  104 , and the plurality of holes  114  defined by the first hydrophobic layer  109  correspond one by one with each other, and both the first orthographic projection of a hole  114  on the first substrate  101  and the third orthographic projection of an opening  105  corresponding to the hole  114  on the first substrate  101  are located within the second orthographic projection of a recess  103  corresponding to the hole  114  on the first substrate  101 , and the first orthographic projection, the second orthographic projection, and the third orthographic projection form concentric rings, the first orthographic projection is located between the second orthographic projection and the third orthographic projection, and the third orthographic projection is located within the first orthographic projection, a concentric ring pattern as illustrated at the right side of  FIG.  5    is formed. That is, the size of the circular opening  105  defined by the shielding layer  104  is the smallest, the size of the circular recess  103  defined by the defining layer  102  is the largest, and the size of the circular hole  114  defined by the first hydrophobic layer  109  is between the two. Of course, the recess  103 , the opening  105 , and the hole  114  are not limited to forming concentric circular rings. They can also form, for example, concentric rectangular rings, concentric square rings, concentric elliptical rings, concentric polygonal rings, and the like. 
     The first hydrophobic layer  109  has hydrophobic and lipophilic characteristics, and the material of the first hydrophobic layer  109  is resin or silicon nitride, for example, it may be a commercially available epoxy resin with the model number DL-1001C. The first hydrophobic layer  109  may also be made of other suitable inorganic or organic materials, as long as the first hydrophobic layer  109  is hydrophobic. In some embodiments, the first hydrophobic layer  109  may be directly prepared using a hydrophobic material. In other embodiments, the first hydrophobic layer  109  may be made of a material that does not have hydrophobicity. In this case, hydrophobization treatment needs to be applied to the surface of the first hydrophobic layer  109 , so that the surface of the first hydrophobic layer  109  is hydrophobic. 
     In the embodiment of the present disclosure, the hydrophilic layer  108  and the first hydrophobic layer  109  can jointly adjust the surface contact angle of the droplets of the reaction system solution, so that the microfluidic device containing the array substrate  100  can realize self-absorption liquid sampling and oil sealing. In the array substrate  100 , the first hydrophobic layer  109  is provided to improve the hydrophobic performance of the outside of the recess  103 , and the hydrophilic layer  108  is provided to improve the hydrophilic performance of the inside of the recess  103  (the sidewall (and bottom) of the recess  103 ), thereby facilitating the infiltration of the reaction system solution from the outside of the recess  103  to the inside of the recess  103 . Therefore, under the joint action of the hydrophilic layer  108  and the first hydrophobic layer  109 , the reaction system solution is more likely to enter each recess  103 . 
     In some embodiments, the ratio of the area of the first hydrophobic layer  109  to the area of the hydrophilic layer  108  is between 0.01 and 2.00. For example, the ratio of the area of the first hydrophobic layer  109  to the area of the hydrophilic layer  108  may be 0.01, 0.05, 0.10, 0.50, 1.00, 1.20, 1.40, 1.60, 1.80, 2.00, etc. If the area of the first hydrophobic layer  109  is too large and the area of the hydrophilic layer  108  is too small, the reaction system solution injected into the microfluidic device from the outside is likely to adhere to the surface of the first hydrophobic layer  109  and is difficult to enter the recess  103 . In the embodiment of the present disclosure, by making the first hydrophobic layer  109  and the hydrophilic layer  108  have a suitable area ratio, under the joint action of the hydrophilic layer  108  and the first hydrophobic layer  109 , it is easier for the reaction system solution to enter each recess  103 , thereby avoiding waste of the reaction system solution and improving the utilization ratio, thereby increasing the fluorescence emission intensity of reagent to be tested in each recess  103 , and in turn improving the fluorescence detection accuracy of reagent to be tested. 
     As illustrated in  FIGS.  1  and  2   , the array substrate  100  may further comprise a second insulating layer  111 , and the second insulating layer  111  is located between the heating electrode  106  and the shielding layer  104 . The second insulating layer  111  is used to protect the heating electrode  106 , provide insulation, prevent liquid from corroding the heating electrode  106 , slow down the aging of the heating electrode  106 , and can play a flattening effect. When the recess  103  penetrates the defining layer  102 , the bottom of the recess  103  exposes a part of the surface of the second insulating layer  111 , and the hydrophilic layer  108  covers the sidewall of the recess  103  and the exposed surface of the second insulating layer  111 . 
     In some embodiments, the first insulating layer  110  and the second insulating layer  111  may be made of the same insulating material, for example, made of an inorganic insulating material or an organic insulating material. In an example, the material of the first insulating layer  110  and the second insulating layer  111  comprises silicon dioxide, silicon nitride, or the like. 
     It should be noted that although the figure illustrates that the shielding layer  104  is located between the defining layer  102  and the second insulating layer  111 , this is only an example. As mentioned above, the shielding layer  104  may be located in any film layer between the first substrate  101  and the defining layer  102  or in other positions as described later. For example, the shielding layer  104  may be located between the first substrate  101  and the conductive layer  107 , between the conductive layer  107  and the first insulating layer  110 , between the first insulating layer  110  and the heating electrode  106 , or between the heating electrode  106  and the second insulating layer  111 , and so on. 
     In the embodiment of the present disclosure, by providing the shielding layer  104  with the opening  105 , the shielding layer  104  at least partially shields the first substrate  101  and the defining layer  102 , thereby avoiding or at least reducing the background fluorescence interference caused by the defining layer  102  and the first substrate  101  and improving the fluorescence detection accuracy of reagent to be tested in the recess  103 . By arranging the heating electrode  106  with a plurality of separated sub-parts and optimizing the arrangement of the conductive layer  107 , the temperature uniformity of the heating electrode  106  is improved, thereby facilitating the amplification reaction of the reaction system solution in the recess  103 ; by providing the hydrophilic layer  108  and the first hydrophobic layer  109 , the reaction system solution can more easily enter each recess  103 , thereby improving reaction efficiency and avoiding cross-flow. 
       FIG.  7    illustrates a partial cross-sectional view of an array substrate  200  according to another embodiment of the present disclosure. As illustrated in the figure, except for the arrangement of the shielding layer  104  and the additional third insulating layer  115 , the array substrate  200  is basically the same as the array substrate  100  illustrated in  FIGS.  1  and  2   . The shielding layer  104  and the third insulating layer  115  in the array substrate  200  will be described below. For other structures and corresponding technical effects, reference may be made to the array substrate  100  illustrated in  FIGS.  1  and  2   , which will not be repeated herein. 
     As illustrated in the figure, the shielding layer  104  is located on a side of the first substrate  101  away from the defining layer  102 , that is, on the back side of the first substrate  101 . The shielding layer  104  defines at least one opening  105 , the orthographic projection of the at least one opening  105  on the first substrate  101  at least partially overlaps the orthographic projection of the at least one recess  103  on the first substrate  101 , and the orthographic projection of the shielding layer  104  on the first substrate  101  at least partially overlaps the orthographic projection of the defining layer  102  on the first substrate  101 . It should be noted that the figure only schematically illustrates one opening  105  defined by the shielding layer  104  and one recess  103  defined by the defining layer  102 , but as described above, the shielding layer  104  actually defines a plurality of openings  105 , and the defining layer  102  defines a plurality of recesses  103 , and each opening  105  corresponds to each recess  103 . In an example, the shape of the orthographic projection of each opening  105  on the first substrate  101  is a circle, the shape of the orthographic projection of each recess  103  on the first substrate  101  is also a circle, and the diameter of the opening  105  is smaller than the diameter of a corresponding recess  103 . In the subsequent optical detection process, the excitation light may be incident into the recess  103  from the side of the first substrate  101  through the opening  105  of the shielding layer  104 . The shielding layer  104  is provided on the side of the first substrate  101  away from the defining layer  102 , the arrangement of the shielding layer  104  is no longer limited to other layers in the array substrate  200 . The shielding layer  104  can occupy a larger area, which is beneficial for the shielding layer  104  to shield a larger part of the first substrate  101  and the defining layer  102  or to completely shield the first substrate  101  and the defining layer  102 , thereby further reducing or even avoiding the background fluorescence generated by the defining layer  102  and the first substrate  101 , and improving the fluorescence detection accuracy of the reagent to be tested in the recess  103 . 
     As illustrated in the figure, the array substrate  200  further comprises a third insulating layer  115  located on a side of the shielding layer  104  away from the first substrate  101 . The third insulating layer  115  covers the shielding layer  104  to protect the shielding layer  104  from the influence of external environment. The figure illustrates that the third insulating layer  115  is a continuous film layer and completely fills the opening  105  of the shielding layer  104 . In another example, the third insulating layer  115  is broken at a position corresponding to the opening  105 , and a film layer of the same material as the third insulating layer  115  fills the opening  105  of the shielding layer  104 . In still another example, the third insulating layer  115  is also a continuous film layer but does not fill the opening  105  of the shielding layer  104 . The first insulating layer  110 , the second insulating layer  111 , and the third insulating layer  115  may be made of the same insulating material, for example, made of an inorganic insulating material or an organic insulating material. In an example, the materials of the first insulating layer  110 , the second insulating layer  111 , and the third insulating layer  115  comprise silicon dioxide, silicon nitride, or the like. 
       FIG.  8    illustrates a partial cross-sectional view of an array substrate  300  according to another embodiment of the present disclosure. As illustrated in the figure, except for the arrangement of the shielding layer  104  and the hydrophilic layer  108 , the array substrate  300  is basically the same as the array substrate  100  illustrated in  FIGS.  1  and  2   . The shielding layer  104  and the hydrophilic layer  108  in the array substrate  300  will be described below. For other structures and corresponding technical effects, reference may be made to the array substrate  100  illustrated in  FIG.  1    and  FIG.  2   , which will not be repeated herein. 
     As illustrated in the figure, the shielding layer  104  comprises a first portion  104   a,  which is located on a side of the defining layer  102  away from the first substrate  101 . The first portion  104   a  is attached to the side surfaces of the defining layer  102  and the surface of the defining layer  102  away from the first substrate  101 . It should be noted that terms such as “A is attached to B” in this application refer to the direct contact between the surfaces of A and B. That is, the first portion  104   a  of the shielding layer  104  is in direct contact with the side surfaces of the defining layer  102  and the surface of the defining layer  102  away from the first substrate  101 , and at least partially surrounds the defining layer  102 . The first portion  104   a  of the shielding layer  104  defines a plurality of openings  105 , and the orthographic projection of each opening  105  on the first substrate  101  at least partially overlaps the orthographic projection of a corresponding recess  103  on the first substrate  101 . In an example, the shape of the orthographic projection of each opening  105  on the first substrate  101  is a circle, the shape of the orthographic projection of each recess  103  on the first substrate  101  is also a circle. The diameter of the opening  105  is smaller than the diameter of a corresponding recess  103 . Through this arrangement, in the subsequent optical detection process, the excitation light can be directly irradiated to the reagent to be tested in the recess  103  from above the array substrate  300  through the opening  105  of the shielding layer  104  (that is, in the direction from top to bottom in the figure), which can increase the utilization ratio of the light source and increase the fluorescence emission intensity of the reagent to be tested. The side surfaces of the defining layer  102  and the surface of the defining layer  102  away from the first substrate  101  are completely shielded by the first portion  104   a  of the shielding layer  104 , and therefore will not be irradiated by the excitation light. 
     Although the foregoing embodiment is described in terms of the defining layer  102  and the first portion  104   a  of the shielding layer  104  as two separate film structures, as mentioned above, the defining layer  102  and the first portion  104   a  of the shielding layer  104  may also be the same film structure. In the embodiment where the defining layer  102  and the first portion  104   a  of the shielding layer  104  are of the same film structure, for example, the side surfaces of the defining layer  102  and the surface of the defining layer  102  away from the first substrate  101  (i.e., the upper surface) are physically or chemically treated to make it opaque, so that the side and upper surfaces of the defining layer  102  serve as the first portion  104   a  of the shielding layer  104 ; and the remaining untreated portion of the defining layer  102  continues to function as the defining layer  102 . 
     The hydrophilic layer  108  is disposed on the surface of the first portion  104   a  of the shielding layer  104  away from the first substrate  101 , and covers the surface of the first portion  104   a  of the shielding layer  104  and at least the sidewall of each recess  103 . The hydrophilic layer  108  has the characteristics of being hydrophilic and oleophobic. Since the hydrophilic layer  108  covers at least the sidewall of the recess  103 , the hydrophilicity of the recess  103  can be improved. The reaction system solution can automatically and gradually enter each recess  103  based on the capillary phenomenon when no driving force is applied to the reaction system solution from the outside, thereby realizing automatic sampling and avoiding cross-flow.  FIG.  9    illustrates a partial cross-sectional view of an array substrate  400  according to yet another embodiment of the present disclosure. As illustrated in the figure, except for the arrangement of the shielding layer  104  and the hydrophilic layer  108 , the array substrate  400  is basically the same as the array substrate  100  shown in  FIGS.  1  and  2   . The shielding layer  104  and the hydrophilic layer  108  in the array substrate  400  will be described below. For other structures and corresponding technical effects, reference may be made to the array substrate  100  illustrated in  FIG.  1    and  FIG.  2   , which will not be repeated herein. 
     As illustrated in the figure, the shielding layer  104  comprises a first portion  104   a  and a second portion  104   b.  The first portion  104   a  is located on the side of the defining layer  102  away from the first substrate  101 , and is attached to the side surfaces of the defining layer  102  and the surface of the defining layer  102  away from the first substrate  101 ; the second portion  104   b  is located between the second insulating layer  111  and the defining layer  102 , and is attached to the surface of the defining layer  102  close to the first substrate  101  (i.e., the bottom surface). The first portion  104   a  and the second portion  104   b  together surround the defining layer  102 . The first portion  104   a  of the shielding layer  104  defines a plurality of openings  105 , and the orthographic projection of each opening  105  on the first substrate  101  at least partially overlaps the orthographic projection of a corresponding recess  103  on the first substrate  101 . The second portion  104   b  of the shielding layer  104  defines a plurality of openings  105 , and the orthographic projection of each opening  105  on the first substrate  101  at least partially overlaps the orthographic projection of a corresponding recess  103  on the first substrate  101 . Through this arrangement, in the subsequent optical detection process, the excitation light can be either directly irradiated to the reagent to be tested in the recess  103  from above the array substrate  400  through the opening  105  of the first portion  104   a  of the shielding layer  104  (that is, in the direction from top to bottom in the figure), or irradiated to the recess  103  from below the array substrate  400  through the opening  105  of the second portion  104   b  of the shielding layer  104  (that is, in the direction from bottom to top in the figure), so that the position of the light source emitting the excitation light can be arranged flexibly according to needs. Since all surfaces (upper surface, lower surface, and each side surface) of the defining layer  102  are completely shielded by the shielding layer  104 , the defining layer  102  will not be irradiated by the excitation light. 
     In an example, the orthographic projection of the opening  105  defined by the first portion  104   a  of the shielding layer  104  on the first substrate  101  completely overlaps the orthographic projection of the opening  105  defined by the second portion  104   b  of the shielding layer  104  on the first substrate  101 . For example, the shape of the orthographic projection of the opening  105  defined by the first portion  104   a  of the shielding layer  104  on the first substrate  101  is circular, and the shape of the orthographic projection of the opening  105  defined by the second portion  104   b  of the shielding layer  104  on the first substrate  101  is also circular. The sizes of the openings respectively defined by the first portion  104   a  and the second portion  104   b  are exactly the same. In another example, the shape of the orthographic projection of the recess  103  on the first substrate  101  is circular, the shape of the orthographic projection of the opening  105  defined by the first portion  104   a  of the shielding layer  104  on the first substrate  101  is circular, and the shape of the orthographic projection of the opening  105  defined by the second portion  104   b  of the shielding layer  104  on the first substrate  101  is also circular. The openings respectively defined by the first portion  104   a  and the second portion  104   b  have the same size and are both smaller than the size of the recess  103 . 
     Although the foregoing embodiment is described in terms of the defining layer  102  and the first portion  104   a  and the second portion  104   b  of the shielding layer  104  as separate film layer structures, as described above, the defining layer  102  and the first portion  104   a  and the second portion  104   b  of the shielding layer  104  may also be the same film structure. In the embodiment in which the defining layer  102  and the first portion  104   a  and the second portion  104   b  of the shielding layer  104  are of the same film structure, for example, the side surfaces of the defining layer  102 , the surface of the defining layer  102  away from the first substrate  101  (that is, the upper surface) and the surface of the defining layer  102  close to the first substrate  101  (that is, the lower surface) are physically and chemically treated to make it opaque, thereby making the side surfaces, upper surface, and lower surface of the defining layer  102  (that is, all outer surfaces of the defining layer  102 ) serve as the first portion  104   a  and the second portion  104   b  of the shielding layer  104 ; and the remaining untreated portion of the defining layer  102  (for example, the inner portion of the defining layer  102  wrapped by the outer surface) continues to function as the defining layer  102 . 
     The hydrophilic layer  108  is disposed on the surface of the first portion  104   a  of the shielding layer  104  away from the first substrate  101 , and covers the surface of the first portion  104   a  of the shielding layer  104  and at least covers the sidewall of each recess  103 . The hydrophilic layer  108  has the characteristics of being hydrophilic and oleophobic. Since the hydrophilic layer  108  covers at least the sidewall of the recess  103 , the hydrophilicity of the recess  103  can be improved. The reaction system solution can automatically and gradually enter each recess  103  based on the capillary phenomenon when no driving force is applied to the reaction system solution from the outside, thereby realizing automatic sampling and avoiding cross-flow. 
     According to another aspect of the present disclosure, a microfluidic device is provided. The microfluidic device comprises the array substrate described in any of the previous embodiments. The following takes the microfluidic device comprising the array substrate  100  as an example to introduce. It should be noted that the array substrate provided herein can be used not only in the field of microfluidics, but also in any other appropriate fields, such as the display field, the automobile field, and the like. 
       FIG.  10    illustrates a microfluidic device  500  which comprises the array substrate  100 , a counter substrate  2000  for assembling with the array substrate  100 , and a space between the array substrate  100  and the counter substrate  2000 . The counter substrate  2000  comprises a second substrate  201  and a second hydrophobic layer  202 , and the second hydrophobic layer  202  is located on a side of the second substrate  201  close to the first substrate  101 . The counter substrate  2000  comprises at least one through hole penetrating the second substrate  201  and the second hydrophobic layer  202 . In some embodiments, the size of the microfluidic device  500  is 1.5 cm*1.5 cm. 
     In an example, both the first substrate  101  and the second substrate  201  are glass substrates. The second substrate  201  is disposed opposite to the first substrate  101 , and plays a role of protection, support, isolation, and the like. The microfluidic device  500  is prepared by a glass-based microfabrication method combined with a semiconductor process, so that mass production can be realized, and the corresponding production cost can be greatly reduced. It should be noted that in multiple embodiments of the present disclosure, the first substrate  101  and the second substrate  201  may also use other suitable materials, which are not limited in the embodiments of the present disclosure. 
     In some embodiments, the shape of the first substrate  101  and the shape of the second substrate  201  are both rectangular. In some examples, the size of the first substrate  101  is 3.2 cm*4.5 cm, and the size of the second substrate  201  is 3.2 cm*3 cm. In some embodiments, the size of the second substrate  201  is smaller than the size of the first substrate  101 , the second substrate  201  covers the reaction area  1001 , and the orthographic projection of the second substrate  201  on the first substrate  101  can completely overlap with the reaction area  1001 . It should be noted that the embodiments of the present disclosure are not limited to this. In some other examples, the size of the second substrate  201  may also be the same as the size of the first substrate  101 . In this case, the second substrate  201  covers the reaction area  1001  and the peripheral area  1002 . For example, the orthographic projection of the second substrate  201  on the first substrate  101  may completely coincide with the first substrate  101 . 
     The second hydrophobic layer  202  has hydrophobic and lipophilic characteristics, and is located on a side of the second substrate  201  facing the first substrate  101 . By providing the second hydrophobic layer  202 , the reaction system solution can more easily enter each recess  103 . In an example, the material of the second hydrophobic layer  202  comprises SiN x . In an alternative example, the second hydrophobic layer  202  is a light-absorbing layer, and the material of the light-absorbing layer comprises at least one of TiO 2  and TiON. By designing the second hydrophobic layer  202  as a light-absorbing layer, some unused excitation light can be further absorbed and hence can be prevented from being irradiated on the first substrate  101  and/or the defining layer  102  in a certain way, thereby the fluorescence interference of the first substrate  101  and/or the defining layer  102  can be further reduced. 
     The counter substrate  2000  comprises at least one through hole penetrating the second substrate  201  and the second hydrophobic layer  202 . As illustrated in the figure, the counter substrate  2000  comprises a sample inlet hole  203  and a sample outlet hole  205 , and both the sample inlet hole  203  and the sample outlet hole  205  penetrate the second substrate  201  and the second hydrophobic layer  202 . In an example, the reaction system solution can be injected into the sample inlet hole  203  through a micro-syringe pump or through a pipette, and then into each recess  103  through a self-aspiration liquid manner. In some embodiments, with reference to  FIG.  5   , the reaction area  1001  further comprises a non-functional area  1001   b.  The sample inlet hole  203  and the sample outlet hole  205  are both located in the non-functional area  1001   b,  and are located on different sides of the functional area  1001   a,  such as symmetrically distributed on different sides of the functional area  1001   a.  As illustrated in  FIG.  5   , in the first direction X, the sample inlet hole  203  and the sample outlet hole  205  are respectively located on both sides of the functional area  1001   a.  For example, the sample inlet hole  203  and the sample outlet hole  205  are symmetrically distributed with respect to the second direction Y, so that the flow of the reaction system solution in the microfluidic device  500  can be more uniform, and the reaction system solution can easily enter each recess  103 . Of course, the embodiment of the present disclosure is not limited to this, and the sample inlet hole  203  and the sample outlet hole  205  may also be symmetrically distributed with respect to the first direction X or other arbitrary directions. It should be noted that the sample inlet hole  203  and the sample outlet hole  205  may also be located in the functional area  1001   a.    
     Continuing to refer to  FIG.  10   , the microfluidic device  500  further comprises a plurality of sealants  204 . The plurality of sealants  204  are arranged in the peripheral area  1002  and located between the array substrate  100  and the counter substrate  2000 . The plurality of sealants  204  are configured to maintain the space between the array substrate  100  and the counter substrate  2000 , thereby providing a space for the flow of the reaction system solution. In some embodiments, some sealants  204  may also be arranged in the reaction area  1001 , for example, dispersedly arranged in multiple places in the reaction area  1001 , so as to improve the compressive strength of the microfluidic device  500  and prevent the microfluidic device  500  from being damaged due to external force applied to the reaction area  1001 . In some embodiments, the size and shape of the plurality of sealants  204  may be the same as each other, thereby improving the thickness uniformity of the microfluidic device  500 . In an alternative embodiment, the size and shape of the plurality of sealants  204  can also be set according to the possible stress conditions of the microfluidic device  500 . For example, the size of the sealant  204  is larger on the periphery and the center of the microfluidic device  500 , while the size of the sealant  204  is smaller in the remaining positions of the microfluidic device  500 . 
     In some embodiments, in a direction perpendicular to the first substrate  101 , the height of the sealant  204  is greater than the height of the defining layer  102 , the first substrate  101 , the defining layer  102 , and the sealant  204  jointly define the sample injection channel and the sample output channel of the reaction system solution to ensure that the reaction system solution can move into each recess  103 , and the reaction system solution that does not enter the recess  103  flows out of the space between the array substrate  100  and the counter substrate  2000 . In some embodiments, the height of the sealant  204  is 30% or 50% larger than the height of the defining layer  102 , and the specific ratio between the two may be determined according to actual requirements, which is not limited in the embodiments of the present disclosure. 
     The material of the sealant  204  may be a curable organic material, such as a thermal curing material or a light curing material, for example, an ultraviolet (UV) hardening acrylic resin or other suitable materials. The shape of the sealant  204  may be a spherical shape. In this case, the array substrate  100  and the counter substrate  2000  can be cured and packaged by the sealant  204 , so that the array substrate  100  and the counter substrate  2000  can be assembled together. In this way, the sealant  204  can control the distance between the array substrate  100  and the counter substrate  2000 . The embodiments of the present disclosure include but are not limited thereto. The shape of the sealant  204  can also be any suitable shape such as a columnar shape or an ellipsoidal shape. 
     In some embodiments, the microfluidic device  500  may further comprise a first temperature sensor (not illustrated in the figure). The first temperature sensor is arranged on a side of the first substrate  101  away from the second substrate  201  and is located in the reaction area  1001 . The first temperature sensor is configured to detect the temperature of the reaction area  1001 . For example, the temperature of the reaction area  1001  needs to be maintained at a predetermined temperature (for example, 95° C., 55° C., or 72° C., etc.). The first temperature sensor can detect the temperature of the reaction area  1001  in real time, and then adjust the temperature of the reaction area  1001  in real time through the heating electrode  106  to keep the temperature of the reaction area  1001  at a predetermined temperature, thereby preventing the temperature of the reaction area  1001  from being too high or too low to affect the amplification reaction. The first temperature sensor may be various types of temperature sensors, comprising but not limited to a contact temperature sensor or a non-contact temperature sensor, such as a thermocouple temperature sensor or an infrared temperature sensor. 
     The microfluidic device  500  provided by the embodiments of the present disclosure can have basically the same technical effects as the array substrates described in the previous embodiments. Therefore, for the sake of brevity, the description will not be repeated herein. 
     According to still another aspect of the present disclosure, a microfluidic system is provided, which comprises a control device and the microfluidic device  500  described in any of the foregoing embodiments. The control device is electrically connected to the microfluidic device  500  and is configured to control the temperature of the microfluidic device  500 . The microfluidic system helps to make the droplets automatically enter the recesses  103  of the microfluidic device  500 , can achieve effective sample injection and avoid cross-flow, and can effectively realize the temperature control of the recesses  103  of the microfluidic device  500 . The temperature cycle can be realized without driving the liquid droplets, and no external heating equipment is needed. The integration is high, the operation is simple, and the production cost is low. 
       FIG.  11    illustrates a schematic block diagram of a microfluidic system  600  according to an embodiment of the present disclosure. As illustrated in  FIG.  11   , the microfluidic system  600  comprises a microfluidic device  500 , a control device  620 , and a power supply device  630 . The power supply device  630  provides a signal voltage or a driving voltage or the like to the microfluidic device  500  and the control device  620 . The control device  620  is electrically connected to the microfluidic device  500  and is configured to apply an electrical signal to the microfluidic device  500  to drive the heating electrode  106  of the microfluidic device  500 . The multiple recesses  103  of the microfluidic device  500  can accommodate the reaction system solution. The control device  620  applies an electrical signal to the heating electrode  106  of the microfluidic device  500  to cause the heating electrode  106  to release heat, thereby controlling the temperature of the functional area of the microfluidic device  500 , so that the reaction system solution undergoes the amplification reaction. For example, the control device  620  may be implemented as general-purpose or special-purpose hardware, software, or firmware, etc., for example, it may also comprise a central processing unit (CPU), an embedded processor, a programmable logic controller (PLC), etc. The embodiment of the present disclosure does not limit this. 
     In some embodiments, the microfluidic system  600  may optionally further comprise a second temperature sensor  650 . For example, when the microfluidic device  500  does not comprise the first temperature sensor, the second temperature sensor  650  needs to be provided in the microfluidic system  600 , and the second temperature sensor  650  needs to be installed in the microfluidic device  500  at a position basically the same as that of the first temperature sensor, so as to realize the function of detecting temperature. For example, the second temperature sensor  650  is arranged on the side of the first substrate  101  of the microfluidic device  500  away from the second substrate  201  and is located in the reaction area  1001  of the array substrate  100 , and the second temperature sensor  650  is configured to detect the temperature of the reaction area  1001  of the microfluidic device  500 . The second temperature sensor  650  may be various types of temperature sensors, comprising but not limited to a contact temperature sensor or a non-contact temperature sensor, such as a thermocouple temperature sensor or an infrared temperature sensor. It should be noted that in some other embodiments, when the microfluidic device  500  comprises the first temperature sensor, the microfluidic system  600  comprising the microfluidic device  500  does not need to provide the second temperature sensor  650 . 
     The microfluidic system  600  may further comprise an optical unit  640  configured to perform optical detection on the microfluidic device  500 . In some embodiments, the optical unit  640  comprises a fluorescence detection device configured to perform fluorescence detection on the reagent to be tested in the plurality of recesses  103 . For example, the fluorescence detection device may comprise a fluorescence light source and an image sensor (for example, a charge coupled device (CCD) image sensor). The optical unit  640  may, for example, further comprise an image processing device configured to process the detection image output by the fluorescence detection device. For example, the image processing device may comprise a central processing unit (CPU) or a graphics processing unit (GPU) or the like. For example, the control device  620  is also configured to control the fluorescence detection device and the image processing device to perform corresponding functions. 
     The working principle and process of the microfluidic system  600  are described as follows. 
     First, prepare the reaction system solution. For example, the reaction system solution may comprise a cell lysis solution, a DNA fragment sample solution fragmented by a DNA lyase, and PCR amplification reagents. In an example, it is assumed that the DNA to be tested is exon 19 of the epidermal growth factor receptor (EGFR) gene, and correspondingly, the PCR amplification reagents comprise PCR amplification primers specific for exon 19 of the EGFR gene. For example, the volume of the reaction system solution is 20 microliters, and the reaction system solution comprises 10 microliters of MIX reagent (MIX reagents comprise Taq enzyme, dNPTs and MgCl 2 ), 0.6 microliters of upstream primers (10 millimoles (mM)), 0.6 microliters (10 mM) of downstream primers, 7.8 microliters of water and 1 microliter of fully diluted template deoxyribonucleic acid (DNA), to ensure that the amount of template DNA in each micro-reaction chamber is less than or equal to 1. 
     Then, install a polytetrafluoroethylene joint and a silicone tube into the sample inlet hole  203  of the microfluidic device  500 , and inject the prepared reaction system solution into the sample inlet hole  203  through a micro-syringe pump or a pipette. The reaction system solution enters the sample inlet hole  203  through the polytetrafluoroethylene joint and the silicone tube, and then the reaction system solution enters each recess  103  through self-absorption under the cooperation of the hydrophilic layer  108  and the first hydrophobic layer  109 . 
     Next, a three-step method dPCR is used to carry out the thermal cycle amplification process. The oil-sealed microfluidic device  500  is placed on the chip carrier of the microfluidic system  600  and fixed by a clamp, so that the conductive layer  107  of the microfluidic device  500  and an electrode are electrically connected. For example, the parameter setting button is used to set the parameters. The cycle parameters are denaturation at 95° C. for 15 seconds, annealing at 55° C. for 45 seconds, and extension at 72° C. for 45 seconds. A total of 30 thermal cycles are set. For example, the pre-denaturation at 95° C. for 5 minutes can also be set. The droplets in the micro-reaction chamber containing template DNA in the microfluidic device  500  undergo PCR amplification reaction, while the droplets in the micro-reaction chamber without template DNA serve as a control group. 
     It should be noted that before PCR amplification, the recess  103  can be filled with a bovine serum albumin (BSA) solution of 0.2% mass fraction and soaked for 1 hour to reduce the adsorption of the PCR reagents and the sample template by the inner surface of the recess  103 , and improve the reaction efficiency and detection accuracy. Then, the BSA solution is pumped clean with a micro-pump, the reaction system solution is injected into the recess  103 , and then seal the device with oil phase liquid. The material of the oil phase liquid may be mineral oil, liquid paraffin isopropyl palmitate, butyl laurate, perfluoroalkane oil, etc., and the oil phase liquid may be used to seal the sample inlet hole  203  and the sample outlet hole  205  to prevent the reaction system solution from volatilizing. 
     After 30 cycles of amplification, the reaction system solution in the recess  103  becomes the reagent to be tested after undergoing polymerase chain reaction. The microfluidic device  500  is taken out, and the microfluidic device  500  is observed by a fluorescence microscope. The excitation wavelength may be, for example, 450 nm to 480 nm, so as to obtain a fluorescence spectrum. In an example, when the reagent to be tested contains exon 19 of the EGFR gene mutation, since the reagent to be tested comprises the specific PCR amplification primers of exon 19 of the EGFR gene mutation, under the action of the PCR amplification primers, the mutated exon 19 is greatly amplified, so that the reagent to be tested shows a positive result, that is, at least a part of the reagent to be tested undergoes a fluorescence reaction. In another example, when the reagent to be tested does not contain exon 19 of the EGFR gene mutation, the reagent to be tested shows a negative result, that is, the reagent to be tested does not have a fluorescence reaction. As a result, the detection of exon 19 of the EGFR gene can be achieved. 
     The microfluidic system  600  provided by the embodiments of the present disclosure may have basically the same technical effects as the array substrates described in the previous embodiments. Therefore, for the sake of brevity, the description will not be repeated herein. 
     According to yet another aspect of the present disclosure, a fluorescence detection method is provided.  FIG.  12    illustrates a flowchart of a fluorescence detection method  700  according to an embodiment of the present disclosure, and  FIG.  13    illustrates a schematic diagram of a fluorescence detection process of a microfluidic device  500  according to an embodiment of the present disclosure. The fluorescence detection method  700  will be described below in conjunction with  FIG.  12    and  FIG.  13   . 
     S 701 : containing the reagent to be tested in at least one recess of the microfluidic device. 
     In an example, the prepared reaction system solution is injected into the sample inlet hole  203  of the microfluidic device  500 , and the reaction system solution enters each recess  103  of the microfluidic device  500  through self-absorption under the cooperation of the hydrophilic layer  108  and the first hydrophobic layer  109 . After the reaction system solution in each recess  103  undergoes the polymerase chain reaction, that is, after the amplification reaction is completed, the aforementioned reagent to be tested is formed. 
     S 702 : making a light of a first wavelength emitted by the light source irradiate the at least one recess through the at least one opening of the shielding layer. 
     As illustrated in  FIG.  13   , the fluorescence detection device  300  comprises a light source system (not illustrated) that emits light  301  of a first wavelength. The light  301  of the first wavelength is irradiated to the corresponding plurality of recesses  103  defined by the defining layer  102  through the plurality of openings  105  of the shielding layer  104 , thereby exciting the reagent to be tested in each recess  103  to emit fluorescence. The light  301  of the first wavelength illustrated in the figure is incident from the bottom to the top, because the shielding layer  104  is located below the defining layer  102 . When the shielding layer  104  is located above the defining layer  102  (as illustrated in  FIGS.  8  and  9   ), the light  301  of the first wavelength can also be incident from the top to the bottom. In addition, it should be noted that the light source system may be integrated in the fluorescence detection device  300  or independent of the fluorescence detection device  300 , which is not limited in the embodiments of the present disclosure. 
     S 703 : detecting a light of a second wavelength emitted by the reagent to be tested. 
     In an example, after the reagent to be tested in the recess  103  is excited by the light  301  of the first wavelength, the light  302  of the second wavelength is emitted by the reagent to be tested, and the second wavelength is greater than the first wavelength. For example, the light  301  of the first wavelength may be blue light, and the light  302  of the second wavelength may be green light; alternatively, the light  301  of the first wavelength may be yellow light, and the light  302  of the second wavelength may be red light. The fluorescence detection device  300  may comprise, for example, a fluorescence light source and an image sensor (for example, a charge coupled device (CCD) image sensor). The image processing device is configured to process the detection picture output by the fluorescence detection device  300 . For example, the image processing device may comprise a central processing unit (CPU) or a graphics processing unit (GPU) or the like. 
       FIG.  14 A  illustrates a fluorescence picture of a conventional microfluidic device that does not comprise a shielding layer, and  FIG.  14 B  illustrates a fluorescence picture of a microfluidic device  500  according to an embodiment of the present disclosure. Each dot in  FIG.  14 A  represents the recess  103 ′ of the microfluidic device. It can be seen from  FIG.  14 A  that each recess  103 ′ and its surrounding area present substantially the same color. This is because the conventional microfluidic device is not provided with a shielding layer. When the excitation light irradiates the recess, not only the reagent to be tested in the recess is excited to emit fluorescence, but also the substrate and defining layer in the microfluidic device are excited to emit fluorescence. Compared with the usually small volume of the reagent to be tested, the background fluorescence caused by the substrate and the defining layer in the microfluidic device greatly affects the fluorescence detection accuracy of the reagent to be tested in the recess, making it impossible to obtain accurate detection results. Therefore, there is a phenomenon that almost all areas emit fluorescence as illustrated in  FIG.  14 A . 
     Each dot in  FIG.  14 B  represents the recess  103  of the microfluidic device  500  according to an embodiment of the present disclosure. It can be seen from  FIG.  14 B  that the color presented by each recess  103  and the color presented by the surrounding area of each recess  103  are very different, and the contrast is very obvious. Each recess  103  presents a relatively bright color, and the surrounding area presents black color. This is because the shielding layer  104  is provided in the microfluidic device  500 , and the orthographic projection of the shielding layer  104  on the first substrate  101  at least partially overlaps the orthographic projection of the defining layer  102  on the first substrate  101 . That is to say, the shielding layer  104  shields at least a part or all of the defining layer  102 , and the orthographic projection of the shielding layer  104  on the first substrate  101  necessarily also at least partially overlaps the first substrate  101  itself. When the light  301  of the first wavelength is irradiated to the recess  103  through the opening  105  of the shielding layer  104 , the shielding layer  104  can shield the first substrate  101  and the defining layer  102 . Therefore, the shielding layer  104  can not only prevent the defining layer  102  from being irradiated by the light  301  of the first wavelength, but can also block the fluorescence emitted by the first substrate  101  irradiated by the light  301  of the first wavelength from transmitting through the shielding layer  104 . Therefore, the light  301  of the first wavelength can only be irradiated to the recess  103  through the opening  105  to excite the reagent to be tested in the recess  103  to emit fluorescence, so that the position corresponding to the recess  103  in  FIG.  14 B  presents a relatively bright color, while the area other than the recess  103  appears black. Therefore, through such a fluorescence detection method, the fluorescence interference caused by the first substrate  101  and the defining layer  102  can be reduced or even avoided, so that the fluorescence signal emitted by the reagent to be tested in the recess  103  can be accurately identified by the detector, so that it can be more sensitively and accurately to read the reaction signal, the fluorescence detection accuracy of the reagent to be tested is improved, and image data support for subsequent nucleic acid amplification reaction data analysis is provided. In addition, through this detection method, clearer micro-hole array imaging can be achieved, detection errors caused by false positives can be reduced, and interference between different channels in the process of multi-channel fluorescence signal detection can be well avoided. 
     Another aspect of the present disclosure provides a method  800  for manufacturing a microfluidic device  500 , which may comprise the array substrate described in any of the previous embodiments. Hereinafter, the method steps are briefly described by taking the microfluidic device  500  comprising the array substrate  100  as an example. 
     Step  801 : providing a first substrate  101 . The first substrate  101  may be made of any suitable material. In an example, the first substrate  101  is made of glass. 
     Step  802 : forming a conductive film layer on the first substrate  101  at about 240° C. In an example, a molybdenum (Mo) layer with a thickness of 200 Å, an aluminum neodymium (AlNd) layer with a thickness of 3000 Å, and a molybdenum (Mo) layer with a thickness of 800 Å are sequentially deposited on the first substrate  101  to form a conductive film layer. The conductive film layer is patterned, such as exposure, development, etching, etc., to form a conductive layer  107 . 
     Step  803 : depositing a first insulating film layer on the conductive layer  107  at about 200° C., and patterning the first insulating film layer to form a first insulating layer  110  covering the conductive layer  107 . In an example, the first insulating layer  110  is a SiO 2  layer with a thickness of about 3000 Å. 
     Step  804 : patterning the first insulating layer  110  to form at least one via  112  penetrating the first insulating layer  110 , and the at least one via  112  exposes a part of the conductive layer  107 . In an example, the first insulating layer  110  is etched in a dry etching machine to form the via  112 . The specific process is described as follows: etching for 10 s at a pressure of about 150 mtorr, a power of about 800 W, and the volumetric flow rate of O 2  of 400 sccm (standard cubic centimeter per minute); etching for 200 s at a pressure of about 60 mtorr, a power of about 800 W, and a gas volume flow ratio of CF 4  and O 2  of about 200:50; etching for 30 s at a pressure of about 130 mtorr, a power of about 800 W, and a gas volume flow ratio of O 2  and CF 4  of about 400:40; and etching for 160 s at a pressure of about 60 mtorr, a power of about  800  W, and a gas volume flow ratio of CF 4  and O 2  about 200:50. 
     Step  805 : depositing a conductive film layer on a side of the first insulating layer  110  away from the first substrate  101 , and then performing processes such as exposure, development, etching, and peeling of the conductive film layer to form a patterned heating electrode  106 . In an example, the material of the heating electrode  106  is ITO. In an example, the heating electrode  106  comprises a plurality of sub-parts separated from each other. 
     Step  806 : depositing a second insulating film layer on a side of the heating electrode  106  away from the first substrate  101 , and patterning the second insulating film layer to form a second insulating layer  111  that at least partially covers the heating electrode  106 . In an example, the material of the second insulating layer  111  is SiO 2 . In another example, the second insulating layer  111  comprises a SiO 2  layer with a thickness of about 1000 A and a SiN x  layer with a thickness of about  2000  A that are sequentially stacked. 
     Step  807 : coating a shielding film layer on a side of the second insulating layer  111  away from the first substrate  101 , and patterning the shielding film layer to form a shielding layer  104  that defines openings  105 . In an example, the specific steps of forming the shielding layer  104  may comprise: spin-coating the shielding film layer on the side of the second insulating layer  111  away from the first substrate  101  under the condition of a pressure of 30 Kpa, and the spin coating speed is about 380 r/min, spin coating time is about 7 seconds. Then, the spin-coated shielding film layer is pre-cured at 90° C. for 120 seconds. Then, the shielding film layer is exposed, developed, and etched through a mask, and the development time is about 75 seconds. Finally, the etched shielding film layer is post-cured at 230° C. for about 20 minutes to form the shielding layer  104  defining the openings  105 . The thickness of the shielding layer  104  is, for example, in the range of 0.6-2.4 microns, for example, 2 microns. In an example, the material forming the shielding layer  104  comprises chromium, chromium oxide, and black resin. 
     Step  808 : coating a defining film layer on a side of the shielding layer  104  away from the first substrate  101 , and patterning the defining film layer to form a defining layer  102  that defines a plurality of recesses  103 . In an example, the process of forming the defining layer  102  is described as follows: first, under a pressure of  30  Kpa, the optical glue is spin-coated on the surface of the shielding layer  104  away from the first substrate  101  at a speed of 300 r/min. The spin-coating time is about 10 seconds. Then the optical glue is cured for 120 seconds at a temperature of 90° C. Repeat the above process twice to obtain a defining film layer. Next, the defining film layer is exposed through a mask, and then the exposed defining film layer is developed with a developing solution for 100 seconds, and then etched. At a temperature of 230° C., the etched defining film layer is cured for 30 minutes, and finally a defining layer  102  defining a plurality of recesses  103  is obtained. The material of the defining layer  102  comprises photoresist. The orthographic projection of each opening  105  of the shielding layer  104  on the first substrate  101  at least partially overlaps the orthographic projection of a corresponding recess  103  of the defining layer  102  on the first substrate  101 , and the orthographic projection of the shielding layer  104  on the first substrate  101  at least partially overlaps the orthographic projection of the defining layer  102  on the first substrate  101 . In an example, the recess  103  of the defining layer  102  is a cylinder, the bottom diameter of the recess  103  is 50 microns, the depth is between 40 and 50 microns, and the distance between the centers of two adjacent recesses  103  is 100 microns. 
     Step  809 : at 200° C., depositing an insulating film layer on the surface of the defining layer  102  away from the first substrate  101 , and exposing, developing, and etching the insulating film layer to form a patterned layer. The patterned layer is treated with a 0.4% KOH solution for about 15 minutes to perform hydrophilic modification on the patterned layer, thereby forming the hydrophilic layer  108 . The hydrophilic layer  108  covers the surface of the defining layer  102  away from the first substrate  101  and at least covers the sidewall of each recess  103 . In an example, the hydrophilic layer  108  is a SiO 2  layer with a thickness of about 3000 Å. 
     Step  810 : depositing an insulating film layer on the surface of the hydrophilic layer  108  away from the first substrate  101 , and exposing, developing, and etching the insulating film layer to form the first hydrophobic layer  109 . In an example, the process of forming the first hydrophobic layer  109  is as follows: in a plasma enhanced chemical vapor deposition (PECVD) equipment, at a temperature of about 200° C., a power of about 600 W, a pressure of about 1200 mtorr, and the distance between the plasma reaction enhancement target and the sample to be deposited in the PECVD equipment of about 1000 mils, SiH 4  (volumetric flow rate of 110 sccm), NH 3  (volumetric flow rate of 700 sccm), and N 2  (volumetric flow rate of 2260 sccm, access time of 100 seconds) are passed into the reaction chamber to deposit a SiN x  film with a thickness of 1000 Å on the surface of the hydrophilic layer  108  away from the first substrate  101 . The SiN x  film layer is exposed, developed, and etched to form the first hydrophobic layer  109 . 
     Step  811 : packaging the array substrate  100  on which the hydrophilic treatment and hydrophobic treatment have been completed. 
     Step  812 : providing a second substrate  201 . The second substrate  201  may be made of any suitable material. In an example, the second substrate  201  is made of glass. 
     Step  813 : depositing a film on a side of the second substrate  201  close to the first substrate  101 , and processing the film to form a second hydrophobic layer  202 , which is a TiO 2  layer with a thickness of about 1000 Å. In an example, the second hydrophobic layer  202  is made of a light-absorbing material, and the light-absorbing material comprises at least one of TiO 2  and TiON. In another example, the second hydrophobic layer  202  is formed of SiN x . The second substrate  201  and the second hydrophobic layer  202  constitute a counter substrate  2000  opposite to the array substrate  100 . 
     Step  814 : perforating the second substrate  201  and the second hydrophobic layer  202  to form at least one sample inlet hole  203  and at least one sample outlet hole  205  penetrating the second substrate  201  and the second hydrophobic layer  202 . In an example, the diameter of the at least one sample inlet hole  203  and the at least one sample outlet hole  205  is between 0.6 mm and 1.2 mm. 
     Step  815 : curing and assembling the array substrate  100  and the counter substrate  2000  with a sealant, and defining the space between the array substrate  100  and the counter substrate  2000 . 
     It should be noted that the manufacturing method may further comprise more steps, which may be determined according to actual requirements, which are not limited in the embodiments of the present disclosure. For the technical effects achieved by the manufacturing method, reference may be made to the above description of the array substrate  100  and the microfluidic device  500 , which will not be repeated herein. 
     When the microfluidic device  500  comprises the array substrate  200  illustrated in  FIG.  7   , the manufacturing method of the microfluidic device  500  is basically the same as the method  800  described above, except that the sequence of steps is slightly different. According to the above steps  801 - 806  and steps  808 - 811 , the first substrate  101 , the conductive layer  107 , the first insulating layer  110 , the heating electrode  106 , the second insulating layer  111 , the defining layer  102 , the recess  103 , the hydrophilic layer  108  and the first hydrophobic layer  109  are sequentially prepared and packaged, that is, step  807  is omitted (i.e., the step of preparing the shielding layer  104  is omitted). After the packaging is completed, the array substrate formed with the above-mentioned film layers is turned over, a shielding film layer is coated on the side of the first substrate  101  away from the defining layer  102 , and the shielding film layer is patterned to form a shielding layer  104  defining openings  105 . In an example, the specific steps of forming the shielding layer  104  may comprise: spin-coating a shielding film layer on the side of the first substrate  101  away from the defining layer  102  under the condition of a pressure of 30 Kpa, and the spin coating speed is about 380 r/min, spin coating time is about 7 seconds. Then, the spin-coated shielding film layer is pre-cured at 90° C. for 120 seconds. Then, the shielding film layer is exposed, developed, and etched through a mask, and the development time is about 75 seconds. Finally, the etched shielding film layer is post-cured at 230° C. for about 20 minutes to form the shielding layer  104  defining the openings  105 . The orthographic projection of each opening  105  of the shielding layer  104  on the first substrate  101  at least partially overlaps the orthographic projection of a corresponding recess  103  of the defining layer  102  on the first substrate  101 , and the orthographic projection of the shielding layer  104  on the first substrate  101  at least partially overlaps the orthographic projection of the defining layer  102  on the first substrate  101 . The thickness of the shielding layer  104  is, for example, in the range of 0.6-2.4 microns, for example, 2 microns. In an example, the material forming the shielding layer  104  comprises chromium, chromium oxide, and black resin. 
     Then, at about 200° C., a third insulating film layer is deposited on the side of the shielding layer  104  away from the first substrate  101 , and the third insulating film layer is patterned to form a third insulating layer  115 . The third insulating layer  115  has a protective effect on the shielding layer  104 . In an example, the third insulating layer  115  is SiO 2  with a thickness of about 3000 Å. 
     Finally, continue to prepare the counter substrate  2000  according to the above steps  812 - 815 , and perform curing and packaging on the array substrate  200  and the counter substrate  2000 , so that the microfluidic device  500  comprising the array substrate  200  is prepared. 
     When the microfluidic device  500  comprises the array substrate  300  illustrated in  FIG.  8   , the manufacturing method of the microfluidic device  500  is basically the same as the method  800  described above, except that the order of step  807  and step  808  is reversed. That is, after the first substrate  101 , the conductive layer  107 , the first insulating layer  110 , the heating electrode  106 , and the second insulating layer  111  are sequentially prepared in the order of the above steps  801 - 806 , prepare a defining layer  102  defining a plurality of recesses  103  on the surface of the second insulating layer  111  away from the first substrate  101  according to step  808 . Then, the shielding layer  104  defining the openings  105  is prepared on the surface of the defining layer  102  away from the first substrate  101 , and the preparation process is the same as that described in the foregoing step  807 . The formed shielding layer  104  covers the side surfaces of the defining layer  102  and the surface of the defining layer  102  away from the first substrate  101 . Finally, continue the subsequent preparation in line with steps  809  to  815  to complete the microfluidic device  500  comprising the array substrate  300 . 
     When the microfluidic device  500  comprises the array substrate  400  illustrated in  FIG.  9   , the manufacturing method of the microfluidic device  500  is basically the same as the method  800  described above, except that another step is added between step  808  and step  809 . That is, the first substrate  101 , the conductive layer  107 , the first insulating layer  110 , the heating electrode  106 , the second insulating layer  111 , the shielding layer  104  and the defining layer  102  are sequentially prepared according to the above steps  801 - 808 . In step  808 , the process of preparing an example of the defining layer  102  is as follows: first, under a pressure of 30 Kpa, an optical glue is spin-coated on the surface of the shielding layer  104  away from the first substrate  101  at a speed of 200 r/min, and the spin coating time is about 10 seconds, then, cure the optical glue for 120 seconds at a temperature of 90° C. Next, the optical glue is exposed through a mask, and then the exposed optical glue is developed with a developing solution for 240 seconds and etched. At a temperature of 230° C., the etched optical glue is cured for  30  minutes, and finally a defining layer  102  that defines a plurality of recesses  103  is obtained. The material of the defining layer  102  comprises photoresist. 
     After the defining layer  102  is prepared, the shielding layer  104  defining the openings  105  is again prepared on the surface of the defining layer  102  away from the first substrate  101 , and the preparation method is the same as that described in step  807 . The formed shielding layer  104  covers the side surfaces of the defining layer  102  and the surface of the defining layer  102  away from the first substrate  101 . Finally, follow steps  809 - 815  to continue to complete subsequent preparations, so as to obtain the microfluidic device  500  comprising the array substrate  400 . That is, when preparing the microfluidic device  500  comprising the array substrate  400 , the shielding layer  104  needs to be prepared twice before and after the process of preparing the defining layer  102 . 
     Another aspect of the present disclosure provides a method  900  for using the microfluidic device  500 . The method  900  may comprise the following steps: 
     Step  901 : making the reaction system solution enter a plurality of recesses  103  of the microfluidic device  500  through the sample inlet hole  203  of the microfluidic device  500 ; 
     Step  902 : supplying an electrical signal to the conductive layer  107  of the microfluidic device  500 , so as to drive the heating electrode  106  through the conductive layer  107  to heat the plurality of recesses  103 . 
     In some embodiments, the method  900  further comprises: cooling the plurality of recesses  103  to change the temperature of the plurality of recesses  103 , so that the reaction system solution in the plurality of recesses  103  undergoes a temperature cycle of a denaturation stage, an annealing stage, and an extension stage. For example, it can be cooled by air-cooled equipment, which has a simple structure and is easy to implement. 
     It should be noted that the method  900  may further comprise more steps, which may be determined according to actual requirements, and the embodiment of the present disclosure does not limit this. 
     In the description of this specification, the description with reference to the terms “one embodiment”, “another embodiment”, etc., means that specific features, structures, materials, or characteristics described in conjunction with the embodiment is comprised in at least one embodiment of the present disclosure. In this specification, the schematic representations of the above-mentioned terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine the different embodiments or examples and the features of the different embodiments or examples described in this specification without contradicting each other. 
     Unless otherwise defined, the technical or scientific terms used in the present disclosure shall have the usual meanings understood by those with ordinary skills in the field to which this disclosure belongs. The “first”, “second” and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. “comprise” or “include” and other similar words mean that the element or item appearing before the word encompasses the element or item listed after the word and its equivalents, but does not exclude other elements or items. Similar words such as “connect” or “connection” are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. “Up”, “down”, “left”, “right”, etc., are only used to indicate the relative position relationship. When the absolute position of the described object changes, the relative position relationship may also change accordingly. 
     As those skilled in the art will understand, although the various steps of the method in the present disclosure are described in a specific order in the drawings, this does not require or imply that these steps must be performed in the specific order, unless the context clearly indicates otherwise. Additionally or alternatively, multiple steps can be combined into one step for execution, and/or one step can be decomposed into multiple steps for execution. In addition, other method steps can be inserted between the steps. The inserted steps may represent such as an improvement of the method described herein, or may be unrelated to the method. In addition, a given step may not be fully completed before the next step starts. 
     The above are only specific implementations of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, and they should be covered by the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.