Patent Publication Number: US-2023158508-A1

Title: Microfluidic substrate, microfluidic chip and manufacturing method thereof

Description:
TECHNICAL FIELD 
     The present disclosure relates to the field of biological detection, in particular to a microfluidic substrate, a microfluidic chip and a manufacturing method thereof. 
     BACKGROUND 
     Digital polymerase chain reaction chip technology (dPCR) is a quantitative analysis method that provides digitalized DNA quantitative information. Since its proposal, it has shown significant advantages in many fields. However, the initial dPCR technology develops very slowly, because if the traditional 96-well plate or 384-well plate is used for PCR amplification, several multi-well plates need to perform amplification simultaneously, which not only involves complicated operations, but also consumes a large amount of experimental samples and reagents. With the emergence of the microfluidic technology and its rapid development in recent years, the combination of microfluidic technology and dPCR technology has greatly improved the sensitivity and accuracy. So far, many companies have successively launched dPCR products. These products have shown huge technological advantages and commercial prospects in research fields such as single cell analysis, early cancer diagnosis, prenatal diagnosis, and the like. 
     SUMMARY 
     The present disclosure provides a microfluidic substrate, a microfluidic chip and a manufacturing method thereof. The patterned design of the conductive layer improves the uniformity of heating and reduces the low-temperature edge area of the conductive layer. As a result, the actual size of the microfluidic chip can be effectively reduced, and the number of reaction chambers per unit area can be increased. 
     According to an aspect of the present disclosure, there is provided a microfluidic substrate. The microfluidic substrate comprises: a first substrate; a conductive layer on the first substrate; and a defining layer on a side of the conductive layer facing away from the first substrate, the defining layer defining a concave portion; wherein the conductive layer comprises a plurality of conductive patterns corresponding to the concave portion, the plurality of conductive patterns are arranged along a first direction, each conductive pattern extends along a second direction and comprises a first end and a second end, the first direction is perpendicular to the second direction, and each conductive pattern has a maximum local resistance value at the first end and the second end of the conductive pattern. 
     Optionally, in some embodiments, the conductive layer has a uniform thickness, each conductive pattern has a midpoint in the second direction, and each conductive pattern has a maximum width along the first direction at the midpoint. 
     Optionally, in some embodiments, each conductive pattern has a minimum width along the first direction at the first end and the second end of the conductive pattern. 
     Optionally, in some embodiments, each conductive pattern has a width that changes continuously along the second direction. 
     Optionally, in some embodiments, each conductive pattern has linear sides. 
     Optionally, in some embodiments, each conductive pattern has curvilinear sides. 
     Optionally, in some embodiments, each conductive pattern has a width that changes discontinuously along the second direction. 
     Optionally, in some embodiments, each conductive pattern has an axisymmetric shape, and a symmetry axis of the axisymmetric shape is parallel to the second direction. 
     Optionally, in some embodiments, each conductive pattern has a minimum thickness at the first end and the second end of the conductive pattern. 
     Optionally, in some embodiments, an overall resistance value between the first end and the second end of each conductive pattern decreases as a distance between the conductive pattern and a center of the concave portion increases. 
     Optionally, in some embodiments, the conductive layer has a uniform thickness, and a width of each conductive pattern in the first direction increases as a distance between the conductive pattern and a center of the concave portion increases. 
     Optionally, in some embodiments, the plurality of conductive patterns has a same length in the second direction. 
     Optionally, in some embodiments, the plurality of conductive patterns constitute a parallel circuit, and a current path of each conductive pattern is along the second direction. 
     Optionally, in some embodiments, the first substrate is a glass substrate. 
     Optionally, in some embodiments, a material of the conductive layer comprises at least one of indium tin oxide and indium zinc oxide. 
     Optionally, in some embodiments, a surface of the concave portion is hydrophilic. 
     Optionally, in some embodiments, the microfluidic substrate further comprises: a wiring between the conductive layer and the first substrate, and a passivation layer between the wiring and the conductive layer, the passivation layer comprising a through hole; the conductive layer is electrically connected to the wiring via the through hole. 
     Optionally, in some embodiments, the wiring comprises a Mo-AlNd-Mo alloy layer. 
     According to another aspect of the present disclosure, there is provided a microfluidic chip. The microfluidic chip comprises: the microfluidic substrate described in any of the foregoing embodiments; a counter substrate on a side of the defining layer facing away from the first substrate; and a sealant on the periphery of the concave portion, the sealant defining a chamber. 
     Optionally, in some embodiments, the chamber is a reaction chamber, and the counter substrate comprises a sample inlet and a sample outlet. 
     According to a further aspect of the present disclosure, there is provided a method for manufacturing a microfluidic chip. The method comprises: providing a first substrate; forming a conductive layer on the first substrate and patterning the conductive layer; forming a defining layer on a side of the conductive layer facing away from the first substrate, the defining layer defining a concave portion, the conductive layer comprising a plurality of conductive patterns corresponding to the concave portion, the plurality of conductive patterns being arranged along a first direction, each conductive pattern extending along a second direction and comprising a first end and a second end, the first direction being perpendicular to the second direction, and each conductive pattern having a maximum local resistance value at the first end and the second end of the conductive pattern; arranging a sealant on the periphery of the concave portion, the sealant defining a chamber; and arranging a counter substrate on a side of the defining layer facing away from the first substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to illustrate embodiments of the present disclosure or the technical solutions in the prior art more clearly, the drawings that need to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the description below are only some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings may be further obtained based on these drawings without creative work. 
         FIG.  1    illustrates a top view of a microfluidic substrate according to an embodiment of the present disclosure; 
         FIG.  2 A  illustrates a cross-sectional view of the microfluidic substrate shown in  FIG.  1    taken along line A-A′ according to an embodiment of the present disclosure; 
         FIG.  2 B  illustrates a cross-sectional view of the microfluidic substrate shown in  FIG.  1    taken along line B-B′ according to an embodiment of the present disclosure; 
         FIG.  2 C  illustrates a cross-sectional view of the microfluidic substrate shown in  FIG.  1    taken along line B-B′ according to another embodiment of the present disclosure; 
         FIG.  3    illustrates a top view of a microfluidic substrate according to another embodiment of the present disclosure; 
         FIG.  4    illustrates a top view of a microfluidic substrate according to a further embodiment of the present disclosure; 
         FIG.  5    illustrates a cross-sectional view of a microfluidic chip according to an embodiment of the present disclosure; and 
         FIG.  6    illustrates a flow chart of a manufacturing method of a microfluidic chip according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     The technical solutions in embodiments of the present disclosure will be described clearly and comprehensively below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all of them. All other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present disclosure. 
     According to an aspect of the present disclosure, a microfluidic substrate is provided.  FIG.  1    illustrates a top view of a microfluidic substrate according to an embodiment of the present disclosure.  FIG.  2 A  illustrates a cross-sectional view of the microfluidic substrate shown in  FIG.  1    taken along line A-A′.  FIG.  2 B  illustrates a cross-sectional view of the microfluidic substrate shown in  FIG.  1    taken along line B-B′. The shape, size, and thickness of each film layer in the drawings do not reflect the true scale of each film layer, and are only intended to illustrate the present disclosure. As shown in  FIGS.  1 - 4   , a microfluidic substrate  100  comprises: a first substrate  101 ; a conductive layer  102  on the first substrate  101 ; and a defining layer  103  on a side of the conductive layer  102  facing away from the first substrate  101 , the defining layer  103  defining a concave portion  104 ; wherein the conductive layer  102  comprises a plurality of conductive patterns  105  corresponding to the concave portion  104 , the plurality of conductive patterns  105  are arranged along a first direction X, each conductive pattern  105  extends along a second direction Y and includes a first end 1051 and a second end 1052, the first direction X is perpendicular to the second direction Y; each conductive pattern  105  has the maximum local resistance value at the first end and the second end of the conductive pattern  105 . 
     In the context of the present disclosure, the “local resistance value” refers to a resistance value per unit length of each conductive pattern in the length direction (i.e., second direction). 
     In the embodiments of the present disclosure, for a single conductive pattern, the first end and the second end of the conductive pattern have a local resistance value greater than that of the middle position of the conductive pattern. According to the resistance heating formula P=I 2 R, the heating power at the first end and the second end of the conductive pattern will also be greater than the heating power at the middle position of the conductive pattern. According to the microfluidic substrate provided by the embodiment of the present disclosure, by designing the resistance of the conductive layer, the uniformity of heating is improved, and the low-temperature edge area of the conductive layer is reduced. As a result, the actual size of the microfluidic chip can be effectively reduced, and the number of reaction chambers per unit area can be increased. 
     Optionally, in some embodiments, as shown in  FIGS.  1 ,  2 A,  2 B,  3  and  4   , the conductive layer  102  has a uniform thickness, each conductive pattern  105  has a midpoint  106  in the second direction Y, and each conductive pattern  105  has a maximum width along the first direction X at the midpoint  106 . 
     For example, each conductive pattern  105  may have a centrally symmetrical shape having a maximum width along the first direction X at the center of symmetry (i.e., the midpoint  106  in the second direction Y). 
     A distance between two adjacent conductive patterns  105  may be in a range of 1 to 200 µm. A simulation result shows that after patterning the conductive patterns in two directions, the temperature uniformity in the region of the concave portion has been significantly improved. 
     Optionally, in some embodiments, as shown in  FIGS.  1 ,  3  and  4   , each conductive pattern  105  has a minimum width along the first direction X at the first end and the second end of the conductive pattern. 
     As shown in  FIGS.  1 ,  3  and  4   , each conductive pattern  105  has a minimum width along the first direction X at the first end and the second end of the conductive pattern. 
     Optionally, in some embodiments, as shown in  FIGS.  1  and  3   , each conductive pattern  105  has a width that changes continuously along the second direction Y. As shown in  FIG.  3   , each conductive pattern  105  has linear sides. As shown in  FIG.  1   , each conductive pattern  105  has curvilinear sides. 
     Optionally, in some embodiments, as shown in  FIG.  4   , each conductive pattern  105  has a width that changes discontinuously along the second direction Y. 
     Optionally, in some embodiments, as shown in  FIGS.  1 ,  3  and  4   , each conductive pattern  105  has an axisymmetric shape, and the symmetry axis of the axisymmetric shape is parallel to the second direction Y Similarly, each conductive pattern  105  may also have a centrally symmetrical shape. 
     Optionally, in some embodiments, as shown in  FIG.  2 C , each conductive pattern  105  has a minimum thickness (denoted by the dashed circle in  FIG.  2 C ) at the first end and the second end of the conductive pattern  105 . 
     For example, each conductive pattern  105  may have a shape as shown in  FIG.  1   ,  FIG.  3    or  FIG.  4    on the X-Y plane, and each conductive pattern  105  has a minimum thickness at the first end and the second end of the conductive pattern  105 . Alternatively, each conductive pattern  105  may have a rectangular shape (i.e., having a constant width) on the X-Y plane, and each conductive pattern  105  has a minimum thickness at the first end and the second end of the conductive pattern  105 . As a result, it can be ensured that each conductive pattern  105  has the maximum local resistance value at the first end and the second end of the conductive pattern  105 . 
     Optionally, in some embodiments, the overall resistance value between the first end and the second end of each conductive pattern  105  decreases as a distance between the conductive pattern  105  and a center C of the concave portion increases. 
     In the context of the present disclosure, the “overall resistance value” refers to a resistance value between the first end and the second end of each conductive pattern, i.e., a resistance value across the first end and the second end. A desired overall resistance value can be obtained by designing the shape of each conductive pattern. The overall resistance value of the conductive pattern can also be determined by performing measurement at two ends of the conductive pattern in the longitudinal direction. 
     In some embodiments, the overall resistance value between the first end and the second end of each conductive pattern decreases as the distance between the conductive pattern and the center of the concave portion increases. That is, the conductive pattern at the edge of the concave portion has a smaller overall resistance value than the conductive pattern at the center of the concave portion. Therefore, according to the resistance heating formula P=U 2 /R, the heating power of the conductive pattern  105  away from the center C will be greater than the heating power of the conductive pattern  105  close to the center C. According to the microfluidic substrate provided by the embodiment of the present disclosure, by further designing the resistance of the conductive layer, the uniformity of heating is improved, and the low-temperature edge area of the conductive layer is reduced. As a result, the actual size of the microfluidic chip can be effectively reduced, and the number of reaction chambers per unit area can be increased. 
     Optionally, in some embodiments, as shown in  FIGS.  1  and  2 B , the conductive layer  102  has a uniform thickness, and the width of each conductive pattern  105  in the first direction X increases as the distance between the conductive pattern  105  and the center C of the concave portion  104  increases. 
     As shown in  FIGS.  1  and  2 B , the plurality of conductive patterns  105  may have the same thickness, and a conductive pattern  105  away from the center C has a larger width. Thus, a conductive pattern having a desired resistance value can be obtained in a simple design manner. 
     In the context of the present disclosure, unless otherwise specified, “the width of the conductive pattern in a certain direction” refers to the maximum width of the conductive pattern in that direction. 
     Optionally, in some embodiments, as shown in  FIGS.  1 ,  3  and  4   , the plurality of conductive patterns  105  have the same length in the second direction Y 
     With the above arrangement, the projection of the plurality of conductive patterns on the first substrate corresponds to a rectangular reaction chamber. Thus, uniform heating can be provided over the area of the rectangular reaction chamber. 
     Optionally, in some embodiments, as shown in  FIGS.  1 ,  3  and  4   , the plurality of conductive patterns  105  constitute a parallel circuit, and the current path of each conductive pattern  105  is along the second direction Y. 
     In some embodiments, as shown in  FIGS.  1 - 4   , a wiring pattern  107  and a conductor plug  108  may be used, so that the plurality of conductive patterns  105  form a parallel circuit. The conductor plug  108  may be connected to an external circuit (not shown) to provide power to the parallel circuit. Thus, the present disclosure provides uniform heating over the area of the reaction chamber by using a simple parallel circuit structure. The same material can be used to fabricate the wiring pattern  107  and the plurality of conductive patterns  105 . For example, the film lay of the conductive layer  102  may be patterned into the wiring pattern  107  and the plurality of conductive patterns  105  in the same patterning process. 
     Optionally, in some embodiments, the first substrate  101  is a glass substrate. 
     According to the embodiments of the present disclosure, a microfluidic substrate and a microfluidic chip may be manufactured using a glass substrate. Compared with using a silicon substrate, the manufacturing process is simplified and the process difficulty is decreased. 
     Optionally, in some embodiments, a material of the conductive layer  102  includes at least one of indium tin oxide and indium zinc oxide. 
     Indium tin oxide and indium zinc oxide are optically transparent. Therefore, fabricating the conductive layer using indium tin oxide and/or indium zinc oxide avoids optical interference to detection. 
     Optionally, in some embodiments, as shown in  FIG.  2 A , a surface of the concave portion  104  is hydrophilic. 
     Hydrophilization treatment may be performed on the surface of the concave portion  104 , or a hydrophilic layer  109  may be vapor-deposited on the surface of the concave portion  104 , so as to confine liquid in the concave portion  104 . A material of the hydrophilic layer  109  may be silicon dioxide, and the embodiment of the present disclosure is not limited thereto. In addition, a hydrophobic layer  110  may be further arranged on a surface of the defining layer  103  located outside the concave portion. A material of the hydrophobic layer  110  may be resin or silicon nitride, and the embodiment of the present disclosure is not limited thereto. 
     Optionally, in some embodiments, as shown in  FIG.  2 A , the microfluidic substrate  100  further comprises: a wiring  111  between the conductive layer  102  and the first substrate  101 , and a passivation layer  112  between the wiring  111  and the conductive layer  102 . The passivation layer  112  includes a through hole  113 , and the conductive layer  102  is electrically connected to the wiring  111  via the through hole  113 . 
     Those skilled in the art can understand that the conductive layer  102  may be electrically connected to the wiring  111  via a conductor plug  108  (shown in  FIG.  1   ) disposed in the through hole  112 . With the above arrangement, the conductive layer can be connected to an external circuit. In addition, an insulating layer  114  may be further arranged between the conductive layer  102  and the defining layer  103  to prevent the conductive layer  102  from being short-circuited. 
     Optionally, in some embodiments, the wiring  111  includes a Mo-AlNd-Mo alloy layer. 
     According to an embodiment of the present disclosure, the wiring  111  is made of, for example, a Mo-AlNd-Mo alloy layer, which decreases the resistance of the wiring  111 , thereby reducing heat generated on the wiring  111 . 
     According to another aspect of the present disclosure, a microfluidic chip is provided. The microfluidic chip comprises the microfluidic substrate described in the above embodiment, so the structure of the microfluidic chip may also refer to the embodiment of the microfluidic substrate and the drawings. As shown in  FIGS.  1  and  5   , a microfluidic chip  500  comprises: a first substrate  101 ; a conductive layer  102  on the first substrate  101 ; and a defining layer  103  on a side of the conductive layer  102  facing away from the first substrate  101 , the defining layer  103  defining a concave portion  104 ; wherein the conductive layer  102  includes a plurality of conductive patterns  105  corresponding to the concave portion  104 , the plurality of conductive patterns  105  are arranged along a first direction X, each conductive pattern  105  extends along a second direction Y and includes a first end 1051 and a second end 1052, the first direction X is perpendicular to the second direction Y, and each conductive pattern  105  has the maximum local resistance value at the first end and the second end of the conductive pattern  105 ; a counter substrate  115  on a side of the defining layer  103  facing away from the first substrate  101 ; and a sealant  116  on the periphery of the concave portion  104 , the sealant  116  defining a chamber  117 . 
     In the embodiment of the present disclosure, for a single conductive pattern, the first end and the second end of the conductive pattern have a local resistance value greater than that of the middle position of the conductive pattern. Therefore, according to the resistance heating formula P=I 2 R, the heating power at the first end and the second end of the conductive pattern will also be greater than the heating power at the middle position of the conductive pattern. According to the microfluidic substrate provided by the embodiment of the present disclosure, by designing the resistance of the conductive layer, the uniformity of heating is improved and the low-temperature edge area of the conductive layer is reduced. As a result, the actual size of the microfluidic chip can be effectively reduced, and the number of reaction chambers per unit area can be increased. 
     Optionally, in some embodiments, as shown in  FIGS.  1 ,  2 A,  2 B,  3  and  4   , the conductive layer  102  has a uniform thickness, each conductive pattern  105  has a midpoint  106  in the second direction Y, and each conductive pattern  105  has a maximum width along the first direction X at the midpoint  106 . 
     For example, each conductive pattern  105  may have a centrally symmetrical shape, and the centrally symmetrical shape has a maximum width along the first direction X at the center of symmetry (i.e., the midpoint  106  in the second direction Y). 
     A distance between two adjacent conductive patterns  105  may be in a range of 1 to 200 µm. A simulation result shows that after patterning the conductive patterns in two directions, the temperature uniformity in the region of the concave portion has been significantly improved. 
     Optionally, in some embodiments, as shown in  FIGS.  1 ,  3  and  4   , each conductive pattern  105  has a minimum width along the first direction X at the first end and the second end of the conductive pattern. 
     As shown in  FIGS.  1 ,  3  and  4   , each conductive pattern  105  has a minimum width along the first direction X at the first end and the second end of the conductive pattern. 
     Optionally, in some embodiments, as shown in  FIGS.  1  and  3   , each conductive pattern  105  has a width that changes continuously along the second direction Y. As shown in  FIG.  3   , each conductive pattern  105  has linear sides. As shown in  FIG.  1   , each conductive pattern  105  has curvilinear sides. 
     Optionally, in some embodiments, as shown in  FIG.  4   , each conductive pattern  105  has a width that changes discontinuously along the second direction Y 
     Optionally, in some embodiments, as shown in  FIGS.  1 ,  3  and  4   , each conductive pattern  105  has an axisymmetric shape, and the symmetry axis of the axisymmetric shape is parallel to the second direction Y. Similarly, each conductive pattern  105  may also have a centrally symmetrical shape. 
     Optionally, in some embodiments, as shown in  FIG.  2 C , each conductive pattern  105  has a minimum thickness (denoted by the dashed circle in  FIG.  2 C ) at the first end and the second end of the conductive pattern  105 . 
     For example, each conductive pattern  105  may have a shape as shown in  FIG.  1   ,  FIG.  3    or  FIG.  4    on the X-Y plane, and each conductive pattern  105  has a minimum thickness at the first end and the second end of the conductive pattern  105 . Alternatively, each conductive pattern  105  may have a rectangular shape (i.e., having a constant width) on the X-Y plane, and each conductive pattern  105  has a minimum thickness at the first end and the second end of the conductive pattern  105 . As a result, it can be ensured that each conductive pattern  105  has the maximum local resistance value at the first end and the second end of the conductive pattern  105 . 
     Optionally, in some embodiments, the overall resistance value between the first end and the second end of each conductive pattern  105  decreases as the distance between the conductive pattern  105  and the center C of the concave portion increases. 
     In some embodiments, the overall resistance value between the first end and the second end of each conductive pattern decreases as the distance between the conductive pattern and the center of the concave portion increases. That is, the conductive pattern at the edge of the concave portion has a smaller overall resistance value than the conductive pattern at the center of the concave portion. Therefore, according to the resistance heating formula P=U 2 /R, the heating power of the conductive pattern  105  away from the center C will be greater than the heating power of the conductive pattern  105  close to the center C. According to the microfluidic substrate provided by the embodiment of the present disclosure, by further designing the resistance of the conductive layer, the uniformity of heating is improved, and the low-temperature edge area of the conductive layer is reduced. As a result, the actual size of the microfluidic chip can be effectively reduced, and the number of reaction chambers per unit area can be increased. 
     Optionally, in some embodiments, as shown in  FIGS.  1  and  2 B , the conductive layer  102  has a uniform thickness, and the width of each conductive pattern  105  in the first direction X increases as the distance between the conductive pattern  105  and the center C of the concave portion  104  increases. 
     As shown in  FIGS.  1  and  2 B , the plurality of conductive patterns  105  may have the same thickness, and a conductive pattern  105  away from the center C has a larger width. Thus, a conductive pattern having a desired resistance value can be obtained in a simple design manner. 
     Optionally, in some embodiments, as shown in  FIGS.  1 ,  3  and  4   , the plurality of conductive patterns  105  have the same length in the second direction Y. 
     With the above arrangement, the projection of the plurality of conductive patterns on the first substrate corresponds to a rectangular reaction chamber. Thus, uniform heating can be provided over the area of the rectangular reaction chamber. 
     Optionally, in some embodiments, as shown in  FIGS.  1 ,  3  and  4   , the plurality of conductive patterns  105  constitute a parallel circuit, and the current path of each conductive pattern  105  is along the second direction Y. 
     In some embodiments, as shown in  FIGS.  1 - 4   , a wiring pattern  107  and a conductor plug  108  may be used, so that the plurality of conductive patterns  105  form a parallel circuit. The conductor plug  108  may be connected to an external circuit (not shown) to provide power to the parallel circuit. Thus, the present disclosure provides uniform heating over the area of the reaction chamber by using a simple parallel circuit structure. The same material can be used to fabricate the wiring pattern  107  and the plurality of conductive patterns  105 . For example, the film layer of the conductive layer  102  may be patterned into the wiring pattern  107  and the plurality of conductive patterns  105  in the same patterning process. 
     Optionally, in some embodiments, the first substrate  101  is a glass substrate. 
     According to the embodiments of the present disclosure, a microfluidic substrate and a microfluidic chip may be manufactured using a glass substrate. Compared with using a silicon substrate, the manufacturing process is simplified and the process difficulty is decreased. 
     Optionally, in some embodiments, a material of the conductive layer  102  includes at least one of indium tin oxide and indium zinc oxide. 
     Indium tin oxide and indium zinc oxide are optically transparent. Therefore, fabricating the conductive layer using indium tin oxide and/or indium zinc oxide avoids optical interference to detection. 
     Optionally, in some embodiments, as shown in  FIG.  2 A , a surface of the concave portion  104  is hydrophilic. 
     Hydrophilization treatment may be performed on the surface of the concave portion  104 , or a hydrophilic layer  109  may be vapor-deposited on the surface of the concave portion  104 , so as to confine liquid in the concave portion  104 . A material of the hydrophilic layer  109  may be silicon dioxide, and the embodiment of the present disclosure is not limited thereto. In addition, a hydrophobic layer  110  may be further arranged on a surface of the defining layer  103  located outside the concave portion. A material of the hydrophobic layer  110  may be resin or silicon nitride, and the embodiment of the present disclosure is not limited thereto. 
     Optionally, in some embodiments, as shown in  FIG.  2 A , the microfluidic substrate  100  further comprises: a wiring  111  between the conductive layer  102  and the first substrate  101 , and a passivation layer  112  between the wiring  111  and the conductive layer  102 . The passivation layer  112  includes a through hole  113 , and the conductive layer  102  is electrically connected to the wiring  111  via the through hole  113 . 
     Those skilled in the art can understand that the conductive layer  102  may be electrically connected to the wiring  111  via a conductor plug  108  (shown in  FIG.  1   ) disposed in the through hole  112 . With the above arrangement, the conductive layer can be connected to an external circuit. In addition, an insulating layer  114  may be further arranged between the conductive layer  102  and the defining layer  103  to prevent the conductive layer  102  from being short-circuited. 
     Optionally, in some embodiments, the wiring  111  includes a Mo-AlNd-Mo alloy layer. 
     According to an embodiment of the present disclosure, the wiring  111  is made of, for example, a Mo-AlNd-Mo alloy layer, which decreases the resistance of the wiring  111 , thereby reducing heat generated on the wiring  111 . 
     Optionally, in some embodiments, as shown in  FIG.  5   , the chamber  117  is a reaction chamber, and the counter substrate  115  includes a sample inlet  119  and a sample outlet  120 . 
     The microfluidic chip provided by the embodiment of the present disclosure can be used for dPCR. A patterned temperature control module is integrated on a chip to achieve efficient, accurate and uniform temperature control, which effectively reduces the size of the chip, increases the number of reaction chamber arrays, and avoids the inaccuracy in detection results. 
     According to a further aspect of the present disclosure, a method for manufacturing a microfluidic chip is provided. As shown in  FIG.  6   , the method comprises: S 11 , providing a first substrate; S 12 , forming a conductive layer on the first substrate and patterning the conductive layer; S 13 , forming a defining layer on a side of the conductive layer facing away from the first substrate, the defining layer defining a concave portion, wherein the conductive layer includes a plurality of conductive patterns corresponding to the concave portion, the plurality of conductive patterns are arranged along a first direction, each conductive pattern extends along a second direction and includes a first end and a second end, the first direction is perpendicular to the second direction, and each conductive pattern has the maximum local resistance value at the first end and the second end of the conductive pattern; S 14 , arranging a sealant on the periphery of the concave portion, the sealant defining a chamber; and S 15 , arranging a counter substrate on a side of the defining layer facing away from the first substrate. 
     According to the manufacturing method of a microfluidic substrate provided by the embodiment of the present disclosure, by designing the resistance of the conductive layer, the uniformity of heating is improved, and the low-temperature edge area of the conductive layer is reduced. As a result, the actual size of the microfluidic chip can be effectively reduced, and the number of reaction chambers per unit area can be increased. 
     An example is provided below to introduce the manufacturing method of a microfluidic chip provided by the present disclosure. The microfluidic chip  500  may comprise the microfluidic substrate described in any of the foregoing embodiments. Hereinafter, the steps of the method will be briefly described by taking the microfluidic chip  500  comprising the microfluidic substrate  100  as an example. 
     Step  701 : 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  702 : 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 deposited successively 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 wiring  111 . 
     Step  703 : depositing a first insulating film layer  112  on the wiring  111  at about 200° C., and patterning the first insulating film  112  to form a first insulating layer  112  covering the wiring  111 . In an example, the first insulating layer  112  is a SiO 2  layer with a thickness of about 3000 Å. 
     Step  704 : patterning the first insulating layer  112  to form at least one through hole  113  penetrating the first insulating layer  112 , the at least one through hole  113  exposing a portion of the wiring  111 . In an example, the first insulating layer  112  is etched in a dry etching machine to form the through hole  113 . The specific process is described as follows: performing etching for 10 seconds under the conditions of a pressure being about 150 mtorr, a power being about 800 w, and a volume flow of O 2  being about 400 sccm (standard cubic centimeter per minute); performing etching for 200 seconds under the conditions of a pressure being about 60 mtorr, a power being about 800 w, and a volume flow ratio of CF 4  to O 2  being about 200:50; performing etching for 30 seconds under the conditions of a pressure being about 130 mtorr, a power being about 800 w, and a volume flow ratio of CF 4  to O 2  being about 400:40; and performing etching for 160 seconds under the conditions of a pressure being about 60 mtorr, a power being about 800 w, and a volume flow ratio of CF 4  to O 2  being about 200:50. 
     Step  705 : depositing a conductive film layer (conductive layer) on a side of the first insulating layer  112  away from the first substrate  101 , and then performing processes such as exposure, development, etching, peeling, and the like on the conductive film layer to form a plurality of conductive patterns  105  (i.e., heaters). In an example, the material of the conductive pattern  105  is ITO. 
     Step  706 : depositing a second insulating film layer on a side of the conductive pattern  105  away from the first substrate  101 , and patterning the second insulating film layer to form a second insulating layer  114  that at least partially covers the conductive pattern  105 . In an example, the material of the second insulating layer  114  is SiO 2 . In another example, the second insulating layer  114  includes an SiO 2  layer with a thickness of about 1000 Å and a SiNx layer with a thickness of about 2000 Å that are sequentially stacked. 
     Step  707 : coating a defining film layer on a side of the second insulating layer  114  away from the first substrate  101 , and patterning the defining film layer to form a defining layer  103  that defines a concave portion  104 . In an example, the process of forming the defining layer  103  is described as follows: firstly, spin-coating an optical adhesive on a surface of the second insulating layer  114  away from the first substrate  101  at a speed of 300 revolutions per minute under a pressure of 30 Kpa, the spin coating taking about 10 seconds, and then curing the optical adhesive for 120 seconds at a temperature of 90° C. The above process is repeated 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 the defining layer  103  defining the concave portion  104  is obtained. The material of the defining layer  103  includes a photoresist. In an example, the concave portion  104  of the defining layer  103  is a cylindrical concave, and the bottom of the concave portion  104  has a diameter of 50 µm and a depth between 40 and 50 µm. The defining layer  103  may define a plurality of concave portions  104 , and the distance between the centers of two adjacent concave portions  104  is 100 micrometers. 
     Step  708 : depositing an insulating film layer on a surface of the defining layer  103  away from the first substrate  101  at 200° C., and performing exposure, development and etching on 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 a hydrophilic layer  109 . The hydrophilic layer  109  covers the surface of the defining layer  103  away from the first substrate  101  and covers the bottom and sidewalls of the concave portion  104 . In an example, the hydrophilic layer  109  is a SiO 2  layer with a thickness of about 3000 Å. 
     Step  709 : depositing an insulating film layer on a surface of the hydrophilic layer  109  away from the first substrate  101 , and performing exposure, development and etching on the insulating film layer to form a first hydrophobic layer  110 . In an example, the process of forming the first hydrophobic layer  110  is as follows: in a plasma enhanced chemical vapor deposition (PECVD) apparatus, introducing SiH 4  (whose volume flow is 110 sccm), NH 3  (whose volume flow is 700 sccm), and N 2  (whose volume flow is 2260 sccm, the introduction time being 100 seconds) into the reaction chamber under 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 apparatus being about 1000 mils, so as to deposit a SiN x  film layer with a thickness of 1000 Å on the surface of the hydrophilic layer  108  away from the first substrate  101 , and performing exposure, development and etching on the SiN x  film layer to form the first hydrophobic layer  110 . 
     Step  710 : encapsulating the microfluidic substrate  100  on which hydrophilic treatment and hydrophobic treatment have been performed. 
     Step  711 : providing a counter substrate  115 . The counter substrate  115  may be made of any suitable material. In an example, the counter substrate  115  is made of glass. 
     Step  712 : depositing a film layer on a side of the counter substrate  115  close to the first substrate  101 , and processing the film layer to form a second hydrophobic layer  118 . The second hydrophobic layer  118  is a TiO 2  layer with a thickness of about 1000 Å. In an example, the second hydrophobic layer  118  is formed of SiN x . 
     Step  713 : punching holes on the counter substrate  115  and the second hydrophobic layer  118  to form at least one sample inlet  119  and at least one sample outlet  120  penetrating the counter substrate  115  and the second hydrophobic layer  118 . In an example, the at least one sample inlet  119  and the at least one sample outlet  120  each has a diameter ranging from 0.6 mm to 1.2 mm. 
     Step  714 : curing and encapsulating the microfluidic substrate  100  and the counter substrate  115  with a sealant, and defining a spacing between the microfluidic substrate  100  and the counter substrate  115 . 
     It is to be noted that the manufacturing method may further comprise more steps, which can be determined according to actual requirements, and is 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 microfluidic substrate  100  and the microfluidic chip  500 , which will not be repeated here. 
     In the description of the present disclosure, the orientations or positional relationships indicated by the terms such as “upper” and “lower” are based on orientations or positional relationships shown in the drawings, which are only for facilitating description of the present disclosure, rather than requiring that the present disclosure must be constructed and operated in a particular orientation, thus they cannot be construed as limitations to the present disclosure. 
     In the description of this specification, the description with reference to the terms “an embodiment”, “another embodiment”, etc. means that a specific feature, structure, material or characteristic described in conjunction with said embodiment is included 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 feature, structure, material or characteristic may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine different embodiments or examples and the features of the different embodiments or examples described in this specification in the case of causing no conflict. In addition, it is to be noted that in this specification, the terms “first” and “second” are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. 
     What have been stated above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art familiar with this technical field within the technical scope revealed by the present disclosure should be encompassed within the protection scope of the present disclosure. Thus, the protection scope of the present disclosure should be based on the protection scope of the claims.