Detection substrate and preparation method thereof, microfluidic chip

Abstract

The application belongs to the technical field of microfluidics, and particularly relates to a detection substrate and a preparation method thereof and a microfluidic chip. The detection substrate is used for a microfluidic chip. The microfluidic chip comprises a driving substrate arranged opposite to the detection substrate. The detection substrate is located below the driving substrate. The detection substrate comprises a substrate, a pressure transmission structure and a detection unit. The pressure transmission structure is arranged on the substrate. The detection unit is arranged between the substrate and the pressure transmission structure and is used for generating an electrical parameter change in response to external pressure. When a liquid drop is located between the driving substrate and the detection substrate, the gravity of the liquid drop is transmitted to the detection unit through the pressure transmission structure, so that the electrical parameter change of the detection unit is caused to determine the position of the liquid drop. The application can realize accurate detection of the position of the liquid drop by causing the electrical parameter change through the gravity of the liquid drop.

Description

Technical Field

[0001] This application belongs to the field of microfluidics technology, specifically relating to a detection substrate and its preparation method, and a microfluidic chip. Background Technology

[0002] Microfluidic chip technology integrates multiple operational units in biological, chemical, and medical analysis processes onto a single micrometer-scale chip, enabling automated sample processing and analysis. This technology offers advantages such as high throughput, fast analysis speed, low reagent consumption, and low power consumption, and is widely used in biochemical detection, drug screening, and disease diagnosis. In the actual operation of microfluidic chips, it is typically necessary to inject the analyte droplet into the chip and control its movement within the microchannels via driving electrodes. Therefore, real-time and accurate acquisition of the droplet's position within the chip is crucial for droplet manipulation, reaction control, and result analysis.

[0003] Currently, the main methods for detecting the position of droplets in microfluidic chips include direct microscopic observation and fluorescent labeling. Microscopic observation is difficult to accurately identify the position of droplets that are too small or have high transparency. Fluorescent labeling requires the addition of fluorescent materials, but it is not suitable for scenarios where labeling is not possible or where the labeling would affect the reaction system. Therefore, existing detection methods have significant limitations and cannot meet the universal detection needs of various droplets. Summary of the Invention

[0004] The purpose of this application is to provide a detection substrate and its preparation method, and a microfluidic chip that can accurately detect the position of a droplet by changing the electrical parameters caused by the gravity of the droplet.

[0005] A first aspect of this application provides a detection substrate for a microfluidic chip. The microfluidic chip includes a driving substrate disposed opposite to the detection substrate, with the detection substrate located below the driving substrate. The detection substrate includes: a substrate; a pressure transmission structure disposed on the substrate; and a detection unit disposed between the substrate and the pressure transmission structure for generating changes in electrical parameters in response to external pressure. When a droplet is located between the driving substrate and the detection substrate, the gravity of the droplet is transmitted to the detection unit via the pressure transmission structure, causing a change in the electrical parameters of the detection unit to determine the position of the droplet.

[0006] In one exemplary embodiment of this application, the detection unit includes a first electrode, a second electrode, and a first support structure disposed between the first electrode and the second electrode. The first electrode is disposed on the substrate, the second electrode is disposed on the side of the first support structure away from the substrate, and the pressure transmission structure is disposed on the side of the second electrode away from the substrate. The pressure transmission structure transmits the gravity of the droplet to the second electrode, causing the second electrode to deform toward the first electrode, thereby changing the distance between the second electrode and the first electrode, and thus changing the electrical parameters.

[0007] In one exemplary embodiment of this application, the first electrode is a strip electrode extending along a first direction, and the second electrode is a strip electrode extending along a second direction, wherein the first direction intersects the second direction.

[0008] In one exemplary embodiment of this application, the pressure transmission structure includes a plurality of second support structures, which are spaced apart from each other on the side of the second electrode away from the substrate, and the cross-sectional area of ​​the second support structures gradually increases from the first electrode to the second electrode.

[0009] In one exemplary embodiment of this application, the pressure transmission structure is further provided with a flexible membrane and a common electrode on the side away from the substrate, and the common electrode is provided on the side of the flexible membrane away from the substrate.

[0010] In one exemplary embodiment of this application, the flexible membrane is provided with at least one opening that penetrates the flexible membrane and is located in the region between adjacent detection units.

[0011] A second aspect of this application provides a microfluidic chip, comprising: a driving substrate; and a detection substrate as described above, wherein the detection substrate is disposed opposite to the driving substrate and is located below the driving substrate, and the driving substrate is provided with driving electrodes for driving the movement of the droplet.

[0012] A third aspect of this application provides a method for preparing a detection substrate as described in any one of the above-mentioned methods, the method comprising the steps of: forming a detection unit on a substrate; and forming a pressure transmission structure on the detection unit.

[0013] In one exemplary embodiment of this application, the detection unit includes a first electrode, a second electrode, and a first support structure disposed between the first electrode and the second electrode, and there is a gap between the second electrode and the first electrode. The step of forming the detection unit on the substrate includes: forming the first electrode on the substrate; forming the first support structure on the first electrode; forming a first sacrificial layer around the first support structure; forming a second electrode on the first support structure and the first sacrificial layer, wherein the second electrode is a deformable electrode; and removing the first sacrificial layer to form a gap between the second electrode and the first electrode.

[0014] In one exemplary embodiment of this application, after forming the detection unit, the method further includes: filling the area outside the detection unit with photoresist, so that the recessed area between the detection units is filled by the photoresist; forming a second sacrificial layer on the photoresist and the detection unit; forming a second support structure on the second sacrificial layer, the height of the second support structure being lower than the height of the second sacrificial layer, and the second support structure and the second sacrificial layer being complementary in the horizontal direction; forming a flexible film on the second support structure and the second sacrificial layer; opening at least one opening in the flexible film, the opening being disposed in the area between adjacent detection units; removing the photoresist and the second sacrificial layer through the opening; and forming a common electrode on the flexible film.

[0015] The detection substrate and its preparation method, as well as the microfluidic chip described in this application, have at least the following beneficial effects:

[0016] This application utilizes a detection unit and a pressure transmission structure mounted on a substrate. When a droplet is positioned between a driving substrate and a detection substrate, its own gravity is transmitted to the detection unit via the pressure transmission structure, causing a change in electrical parameters and thus determining the droplet's position. This detection method requires no external light source or markers, making it suitable for tiny, transparent, or unmarkable droplets. It offers broad detection versatility and does not interfere with the droplet's movement. Furthermore, this microfluidic chip positions the driving and detection substrates opposite each other, with the driving substrate above for driving droplet movement and the detection substrate below for detecting droplet position. These two substrates function separately yet work collaboratively, achieving an organic integration of droplet driving and detection. The chip structure is compact and highly integrated. Moreover, this fabrication method, by first forming the detection unit on the substrate and then forming the pressure transmission structure on the detection unit, ensures that the layering relationship meets design requirements. The steps are clear and compatible with existing processes, facilitating large-scale production.

[0017] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0018] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0020] Figure 1 A cross-sectional view of the droplet located between the driving substrate and the detection substrate is shown.

[0021] Figure 2 A cross-sectional schematic diagram of the pressure transmission structure located on the detection unit is shown.

[0022] Figure 3 A schematic diagram of the structure of the first electrode and the second electrode from a top-down view is shown.

[0023] Figure 4 A cross-sectional schematic diagram of a pressure transmission structure with a flexible membrane and a common electrode is shown.

[0024] Figure 5 A schematic diagram of a structure with openings on a flexible membrane is shown.

[0025] Figure 6 A schematic diagram of the fabrication process of the detection substrate is shown.

[0026] Figure 7 A schematic diagram of the fabrication process of the detection unit is shown.

[0027] Figure 8 A schematic diagram of the preparation method for the detection of [substance name] is shown.

[0028] Figure 9 A schematic diagram of the fabrication process of the pressure transmission structure is shown.

[0029] Figure 10 A schematic diagram of the fabrication process of the pressure transmission structure is shown.

[0030] Figure 11 A schematic diagram of the fabrication process for forming a flexible membrane and a common electrode on a pressure transmission structure is shown.

[0031] Figure 12 A schematic diagram of the fabrication process for forming a flexible membrane and a common electrode on a pressure transmission structure is shown.

[0032] Explanation of reference numerals in the attached figures:

[0033] 10. Microfluidic chip; 100. Detection substrate; 110. Substrate; 120. Detection unit; 121. First electrode; 122. First support structure; 123. Second electrode; 1231. Flexible material layer; 1232. Conductive material layer; 124. First sacrificial layer; 125. Void; 130. Pressure transmission structure; 131. Second support structure; 132. Second sacrificial layer; 133. Photoresist; 140. Flexible film; 141. Opening; 150. Common electrode; 200. Driving substrate; 210. Driving electrode; 300. Droplet; X, First direction; Y, Second direction. Detailed Implementation

[0034] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art.

[0035] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0036] In this application, unless otherwise expressly specified and limited, the terms "assembly," "connection," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0037] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0038] Example 1

[0039] See Figure 1 As shown, this embodiment provides a detection substrate 100, which is used in a microfluidic chip 10. The microfluidic chip 10 also includes a driving substrate 200 disposed opposite to the detection substrate 100. The detection substrate 100 is located below the driving substrate 200, thereby utilizing the gravity of the droplet 300 as a signal source. When the droplet 300 is located between the driving substrate 200 and the detection substrate 100, the gravity of the droplet 300 acts downward on the detection substrate 100. The gravity signal is converted into an electrical signal through the pressure transmission structure 130 and the detection unit 120 inside the detection substrate 100, thereby achieving accurate detection of the position of the droplet 300.

[0040] In some embodiments, see Figure 2 As shown, the detection substrate 100 may include a substrate 110, a detection unit 120, and a pressure transmission structure 130. The substrate 110 is a support layer for the detection substrate 100 and may be made of transparent or opaque materials such as glass, quartz, silicon wafers, or flexible polymer materials.

[0041] For example, the substrate 110 can be a glass substrate 110 because it has good light transmittance, chemical stability and compatibility with microelectronic processes.

[0042] In some embodiments, see Figure 2 As shown, the detection unit 120 can be disposed on the substrate 110, and the pressure transmission structure 130 is disposed on the side of the detection unit 120 away from the substrate 110, that is, the detection unit 120 is located between the substrate 110 and the pressure transmission structure 130. The detection unit 120 is used to generate changes in electrical parameters in response to external pressure.

[0043] like Figure 1 As shown, when the droplet 300 is located between the driving substrate 200 and the detection substrate 100, the gravity of the droplet 300 is transmitted to the detection unit 120 through the pressure transmission structure 130, causing a change in the electrical parameters of the detection unit 120. The position of the droplet 300 can be determined by detecting this change in electrical parameters. This gravity-based detection method does not require an external light source or fluorescent marker, and is suitable for tiny, transparent, or unmarkable droplets 300. It has strong detection versatility and does not interfere with the droplet 300 itself, ensuring the accuracy of subsequent biochemical analysis.

[0044] In some embodiments, such as Figure 2 As shown, the detection unit 120 may include a first electrode 121, a second electrode 123, and a first support structure 122 disposed between the first electrode 121 and the second electrode 123. The first electrode 121 is disposed on the substrate 110 and may be made of conductive materials such as indium tin oxide (ITO), metal thin films (such as Au, Ag, Cu, Al, etc.) or conductive polymer materials.

[0045] For example, the first electrode 121 can be made of ITO material, deposited on the glass substrate 110 by sputtering process, and patterned into a strip electrode by photolithography process, extending along the first direction X.

[0046] It should be noted that the first electrode 121 serves as the fixed electrode of the detection unit 120 and does not participate in deformation. It is used to form a capacitance or resistance detection structure with the second electrode 123.

[0047] In some embodiments, a microstructure (not shown) is provided on the surface of the first electrode 121 opposite to the second electrode 123. The microstructure can be a microbump, microgroove, microstripes, or a periodic grating structure, formed by etching or nanoimprinting processes, and has a feature size of 0.1 μm to 0.5 μm. Thus, when the second electrode 123 deforms, causing a decrease in the distance between it and the first electrode 121, the microstructure can alter the local electric field distribution, enhance the electric field strength, thereby amplifying the capacitance change and improving detection sensitivity.

[0048] For example, the microbump structure can generate a stronger local electric field at the same electrode spacing, making the capacitance value more sensitive to distance changes; the microgroove structure can increase the effective electrode area, further improving the capacitance reference value. In addition, the presence of microstructures can reduce the risk of adhesion between the second electrode 123 and the first electrode 121 due to electrostatic adsorption or adhesion, improving the reliability and lifespan of the chip.

[0049] In some embodiments, see Figure 2 As shown, the first support structure 122 is disposed on the first electrode 121 to support the second electrode 123 and maintain the initial distance between the first electrode 121 and the second electrode 123. The first support structure 122 can be made of a rigid insulating material, such as silicon nitride (SiNx), silicon oxide (SiOx), polymethyl methacrylate (PMMA), SU-8 photoresist, etc.

[0050] For example, the first support structure 122 can be made of silicon nitride (SiNx) material because of its good rigidity, insulation and compatibility with semiconductor processes.

[0051] In some embodiments, the shape of the first support structure 122 may be columnar, strip-shaped, or ring-shaped.

[0052] For example, such as Figure 2As shown, it can be in the form of a support pillar. The cross-sectional area of ​​the end of the first support structure 122 that contacts the first electrode 121 can be larger than the cross-sectional area of ​​its other end, forming a trapezoidal or conical structure to enhance the support stability of the second electrode 123. The first support structure 122 is formed on the first electrode 121 by deposition and etching processes. Its height determines the initial distance between the first electrode 121 and the second electrode 123. This distance can be optimized according to the detection sensitivity and process capability, for example, set to 0.5 μm to 5 μm.

[0053] In some embodiments, the first support structure 122 is arranged in an array on the first electrode 121, and a plurality of first support structures 122 are provided in the area of ​​each detection unit 120.

[0054] For example, within the detection unit 120 area corresponding to each intersection point, multiple first support structures 122 in a 2×2, 3×3, or ring array are provided. In this way, multiple support points jointly support the second electrode 123, enabling the second electrode 123 to maintain better flatness and stability in its initial state, reducing tilting or warping of the second electrode 123 caused by single-point support. Simultaneously, when the second electrode 123 is subjected to compressive deformation, the multiple support points can more evenly distribute the force, resulting in a more regular deformation profile for the second electrode 123, improving the linear relationship between deformation and pressure, thereby enhancing detection accuracy and repeatability. Furthermore, the redundant support structure formed by multiple support points ensures that even if individual support structures are damaged due to process defects or long-term use, the other support structures can still maintain the basic position of the second electrode 123, improving the chip's reliability and lifespan.

[0055] In some embodiments, such as Figure 2 As shown, the second electrode 123 is disposed on the side of the first support structure 122 away from the substrate 110, and is a deformable electrode. The second electrode 123 may include a flexible material layer 1231 and a conductive material layer 1232 disposed on the flexible material layer 1231, and the flexible material layer 1231 is connected to the first support structure 122. The flexible material layer 1231 may be made of polymeric materials with good flexibility and elasticity, such as polyimide (PI), polymethyl methacrylate (PMMA), and polydimethylsiloxane (PDMS). The conductive material layer 1232 may be made of materials such as indium tin oxide (ITO), silver nanowires, and conductive polymers.

[0056] For example, the flexible material layer 1231 can be made of polyimide (PI) material because of its good flexibility, thermal stability and compatibility with semiconductor processes. The conductive material layer 1232 can be made of indium tin oxide (ITO) and formed on the flexible material layer 1231 by sputtering or coating processes.

[0057] In some embodiments, the flexible material layer 1231 and the conductive material layer 1232 together constitute the second electrode 123. The flexible material layer 1231 serves as a deformation layer, and the conductive material layer 1232 serves as a conductive layer. Figure 3 As shown, the second electrode 123 is a strip electrode extending along the second direction Y, and the first direction X intersects with the second direction Y.

[0058] For example, the first direction X and the second direction Y can intersect perpendicularly to form an array of intersection points, with each intersection point corresponding to a detectable position.

[0059] Understandably, this strip-shaped cross electrode layout can achieve two-dimensional positioning of the droplet 300 by scanning the changes in the electrical parameters of the first electrode 121 and the second electrode 123. The detection circuit is simple and the positioning accuracy is high.

[0060] In some other embodiments, the edge region of the second electrode 123 is provided with a reinforcing structure (not shown in the figure).

[0061] For example, an additional layer of polyimide (PI) material or micron-level reinforcing ribs are added to the strip-shaped edge or intersection edge region of the second electrode 123, making the thickness of the edge region of the second electrode 123 slightly larger than that of the central region (e.g., 0.5 μm thick in the central region and 0.8 μm-1.0 μm thick in the edge region). Thus, when the second electrode 123 is subjected to compressive deformation, the central region is the main deformation area, while the edge region deforms less due to the reinforcement structure, forming a bowl-shaped deformation profile with a concave center and relatively fixed edges. This deformation profile can more effectively change the distance between the central region and the first electrode 121, while having less impact on the edge region, thereby improving the signal-to-noise ratio of the detection signal. Simultaneously, the edge reinforcement structure can also improve the mechanical strength at the connection between the second electrode 123 and the first support structure 122, mitigating fatigue cracking at the connection interface caused by repeated deformation after long-term use.

[0062] In other embodiments, micron- or submicron-scale grooves, pits, or micropore arrays are formed on the top surface of the first support structure 122. The groove depth is 0.2 μm to 0.5 μm, and the width is 0.3 μm to 0.8 μm. When the flexible material layer 1231 (PI layer) of the second electrode 123 is formed, the polyimide (PI) solution flows into these microgrooves or micropores and solidifies to form a micro-locking structure. In this way, the micro-locking structure significantly enhances the interface's ability to resist shear and tensile stresses. Even if the interface is subjected to repeated deformation, the micro-locking structure can provide continuous mechanical holding force, improving the slippage or peeling of the second electrode 123 from the surface of the first support structure 122.

[0063] In other embodiments, an elastic recovery structure (not shown) is provided inside or below the flexible material layer 1231 of the second electrode 123. For example, elastic microspheres (such as hollow glass microspheres or rubber microspheres) can be incorporated into the flexible material layer 1231, or a layer of elastomeric material (such as PDMS or SEBS) with a thickness of micrometers can be provided below the flexible material layer 1231 (near the first electrode 121). The elastic microspheres or elastomeric material layer have a higher elastic modulus and better recovery performance than PI. Thus, when the external force is removed, the elastic microspheres or elastomeric material layer can generate a rebound force, assisting the flexible material layer 1231 in restoring its original shape and reducing the accumulation of permanent deformation. Simultaneously, the elastomeric material layer can also buffer excessive pressure, improving the plastic deformation or damage to the flexible material layer 1231 caused by excessive deformation. This structural design improves deformation recovery capability at the material level, extending the chip's lifespan.

[0064] In some embodiments, see Figure 1 and Figure 2 As shown, the pressure transmission structure 130 is disposed on the side of the second electrode 123 away from the substrate 110, for transmitting the gravity of the droplet 300 to the second electrode 123. The pressure transmission structure 130 may include a plurality of second support structures 131, which are disposed at intervals on the side of the second electrode 123 away from the substrate 110. The second support structures 131 may be made of rigid materials, such as silicon nitride (SiNx), silicon oxide (SiOx), polymethyl methacrylate (PMMA), SU-8 photoresist, etc. For example, the second support structure 131 may be SiNx.

[0065] In some embodiments, the center of each second support structure 131 coincides with the center of its corresponding second electrode 123 in a direction perpendicular to the substrate 110. Thus, when the droplet 300 acts under gravity on the second support structure 131, the pressure can be transmitted vertically and uniformly to the central region of the second electrode 123, causing symmetrical deformation of the second electrode 123. This reduces torsional or non-uniform deformation of the second electrode 123 caused by eccentric forces, thereby improving the predictability of deformation and the stability of the detection signal. Simultaneously, the center-aligned design allows the pressure to be concentrated to the maximum extent in the central region of the second electrode 123, further enhancing the pressure amplification effect and improving detection sensitivity.

[0066] In some embodiments, such as Figure 2As shown, the second support structure 131 is designed with a gradually increasing cross-sectional area from the first electrode 121 to the second electrode 123 (i.e., away from the substrate 110), for example, in an inverted trapezoidal or inverted conical shape. Thus, when the droplet 300 acts under gravity on the second support structure 131, because the cross-sectional area of ​​the end of the second support structure 131 that contacts the second electrode 123 (the lower end) is smaller, according to the pressure formula... Under the same force, a smaller contact area generates greater pressure, thus concentrating the gravity of the droplet 300 onto a localized area of ​​the second electrode 123, significantly enhancing the deformation of the second electrode 123 and improving detection sensitivity. Simultaneously, the spaced-apart second support structures 131 reduce mechanical crosstalk between adjacent detection units 120, ensuring that each detection unit 120 independently responds to the gravity of the droplet 300 above it, thereby improving the accuracy of position detection.

[0067] In some embodiments, the height of the second support structure 131 can be designed according to process requirements, for example, set to 2μm to 10μm. The cross-sectional shape of the second support structure 131 can be circular, square or polygonal. For example, the cross-section of the second support structure 131 can be square to facilitate patterning in the photolithography process.

[0068] Understandably, the gap between the second support structures 131 can be optimized based on the size of the droplet 300 and the surface tension, for example, set to 0.1 μm to 1 μm. This improves the mutual influence caused by the contact between adjacent support structures while minimizing the obstruction of the gap to the movement of the droplet 300. Since the droplet 300 typically has a size of tens to hundreds of micrometers and is subject to surface tension, it can cross tiny gaps much smaller than its own size without being affected. Therefore, this gap setting will not interfere with the normal movement of the droplet 300.

[0069] In some embodiments, the second support structure 131 may adopt a double-layer composite structure, which may include a lower rigid portion in contact with the second electrode 123 and an upper elastic portion away from the second electrode 123. The lower rigid portion is made of a high-rigidity material such as silicon nitride (SiNx) or silicon oxide (SiOx), and its thickness accounts for approximately 60%-80% of the total height of the second support structure 131; the upper elastic portion is made of an elastic material such as polyimide (PI) or polydimethylsiloxane (PDMS), and its thickness accounts for approximately 20%-40%. In this way, the lower rigid portion ensures that the second support structure 131 has sufficient rigidity to effectively transfer the gravity of the droplet 300 to the second electrode 123 without deforming itself; the upper elastic portion has a certain buffering effect. When the gravity of the droplet 300 is too large or there is an impact, the upper elastic portion can undergo slight deformation to absorb some energy, reducing the excessive pressure or damage to the second electrode 123 caused by the rigid structure. Meanwhile, the upper elastic part provides better mechanical matching between the top of the second support structure 131 and the subsequently formed flexible membrane 140, reducing interface stress and improving structural stability.

[0070] In some embodiments, a hydrophobic layer (not shown) is further provided on the side of the pressure transmission structure 130 away from the substrate 110. The hydrophobic layer may be made of hydrophobic materials such as polytetrafluoroethylene (PTFE), fluorinated polymers (such as Cytop), or fluorinated silanes.

[0071] For example, fluorinated polymer materials can be used due to their good hydrophobicity and compatibility with the microfluidic chip 10 process. The hydrophobic layer reduces the friction of the droplet 300 on the surface of the detection substrate 100, making the droplet 300 easier to move under the action of the driving electrode 210, thereby improving the sensitivity and response speed of the droplet 300 manipulation.

[0072] The hydrophobic layer can be formed using vapor deposition or spin coating. By controlling process parameters (such as deposition rate, solution concentration, spin coating speed, etc.), the hydrophobic layer material can be ensured to cover only the top surface of the second support structure 131 and not flow into the tiny gaps between the second support structures 131. For spin coating, the surface tension of the solution and the rapid evaporation characteristics of the solvent can be utilized to prevent the hydrophobic material from seeping into the gaps before curing. For vapor deposition, a mask or selective deposition method can be used to ensure that the hydrophobic layer is formed only in a predetermined area.

[0073] Furthermore, the thickness of the hydrophobic layer is controlled within a relatively thin range of 100nm to 500nm, further reducing the possibility of it flowing into the gaps. Through the above process control, it is ensured that the hydrophobic layer is only placed on the top of the second support structure 131, while the gaps between the second support structures 131 remain open. This achieves the hydrophobic function without affecting the stress deformation of the second support structure 131 or the sensitivity of the detection unit 120.

[0074] When the droplet 300 is located between the driving substrate 200 and the detection substrate 100, the gravity of the droplet 300 acts on the second support structure 131 on the detection substrate 100, and the second support structure 131 transmits this pressure to the second electrode 123 below it. The flexible material layer 1231 (PI layer) of the second electrode 123 deforms under pressure and is recessed towards the substrate 110, thereby changing the distance between the second electrode 123 and the first electrode 121. Since the conductive material layer 1232 of the second electrode 123 is tightly attached to the flexible material layer 1231, the conductive material layer 1232 deforms synchronously with the flexible material layer 1231, so the overall distance between the second electrode 123 and the first electrode 121 changes. This change in distance causes a change in the capacitance value between the second electrode 123 and the first electrode 121. By detecting the capacitance value between the first electrode 121 and the second electrode 123 at each intersection point and comparing it with the initial capacitance value when there is no droplet 300, it is possible to determine which locations have droplets 300.

[0075] It is worth mentioning that, at the locations where droplets 300 are present, the second electrode 123 deforms more significantly due to gravity, resulting in a smaller electrode spacing and an increased capacitance; at the locations without droplets 300, the capacitance remains at its initial state. By scanning the intersection of the first electrode 121 and the second electrode 123, the two-dimensional position distribution of the droplets 300 can be obtained.

[0076] In some other embodiments, a stress relief structure (not shown) is provided on the side of the substrate 110 away from the detection unit 120 (i.e., the back of the substrate 110). The stress relief structure can be an annular groove, a mesh-like groove, or a periodic array of micropores, formed by laser etching or wet etching processes, with a depth of 10%-30% of the thickness of the substrate 110. Thus, during chip fabrication and use, due to the difference in the thermal expansion coefficients of the multilayer materials, thermal stress will be generated inside the substrate 110, causing warping of the substrate 110 or displacement of the detection unit 120. The stress relief structure can absorb and disperse these internal stresses, reducing deformation of the substrate 110, maintaining the flatness and positional accuracy of the detection unit 120, thereby improving the consistency and long-term stability of the detection. Simultaneously, the stress relief structure can also improve the reliability of the chip during thermal cycling, extending the chip's lifespan.

[0077] It is worth mentioning that after the microfluidic chip 10 is used a certain number of times (e.g., 10, 50, 100 times) or for a certain period of time (e.g., 1 day, 1 week, 1 month), the control system automatically triggers a calibration program. In the absence of droplets 300, the system scans the electrical parameters (e.g., capacitance values) of all detection units 120 and updates the current values ​​to new initial reference values, storing them in memory. Subsequent determination of the droplet 300's position is based on a comparison between the current detection value and the updated initial reference value. In this way, even if the flexible material undergoes a certain degree of permanent deformation or creep, as long as the post-deformation state is relatively stable, the incremental change caused by the gravity of the droplet 300 can still be accurately detected by recalibrating the reference value. This method does not require changes to the chip structure; it can be implemented solely through the control algorithm. It is low-cost, easy to implement, and can effectively compensate for detection errors caused by various factors such as material fatigue, temperature drift, and humidity changes.

[0078] In this application, the detection unit 120 and the pressure transmission structure 130 are both integrated on the detection substrate 100, functionally separated from the driving substrate 200. The driving substrate 200 is provided with driving electrodes 210, such as TFT array electrodes or digital microfluidic electrodes, for driving the movement of the droplet 300. Voltage is applied to control the movement of the droplet 300 within the chip. The detection substrate 100 is located below the driving substrate 200, monitoring the position of the droplet 300 in real time and feeding the position information back to the control system. The control system adjusts the voltage of the driving electrodes 210 based on the position information, achieving precise control of the droplet 300. This structural design, separating driving and detection, allows the driving substrate 200 to utilize existing mature microfluidic driving technology without requiring additional modifications for the detection function, reducing chip design complexity and manufacturing costs. Furthermore, the modular design of the detection substrate 100 facilitates individual optimization and improvement of detection performance.

[0079] Example 2

[0080] This embodiment further optimizes the pressure transmission structure 130 based on Embodiment 1. A flexible membrane 140 and a common electrode 150 are also provided on the side of the pressure transmission structure 130 away from the substrate 110, such as... Figure 4 As shown.

[0081] A flexible film 140 is formed on the second support structure 131, covering the second support structure 131 and the gap region between the two support structures. The flexible film 140 can be made of flexible materials such as polyimide (PI), polymethyl methacrylate (PMMA), or polydimethylsiloxane (PDMS). The common electrode 150 can be made of transparent conductive materials such as indium tin oxide (ITO) or silver nanowires.

[0082] For example, the flexible membrane 140 can be made of polyimide (PI) material. A common electrode 150 is disposed on the side of the flexible membrane 140 away from the substrate 110. The common electrode 150 can be made of silver nanowires, which have good flexibility and conductivity, and can adapt to the deformation of the flexible membrane 140 without easily breaking.

[0083] Understandably, firstly, the flexible membrane 140 covers the gap between the second support structures 131, so that the droplet 300 does not need to cross the tiny gap when moving, but moves directly on the surface of the continuous flexible membrane 140, which greatly reduces the resistance to the movement of the droplet 300 and improves the driving efficiency and reliability of the droplet 300.

[0084] Secondly, the common electrode 150 serves as the counter electrode to the driving electrode 210, cooperating with the driving electrode 210 on the driving substrate 200 to form a driving electric field that controls the movement of the droplet 300. Since the common electrode 150 is disposed on the detection substrate 100, it is closer to the droplet 300 and is a continuous electrode across the entire surface, enabling a stronger and more uniform electric field distribution. In this embodiment, the distance between the common electrode 150 and the driving electrode 210 is shortened, resulting in a stronger electric field intensity. This generates a greater driving force at the same driving voltage, or significantly reduces the required driving voltage to achieve the same driving force. A lower driving voltage reduces chip power consumption, simplifies the driving circuit, extends chip lifespan, and reduces the risk of electrical damage to the biological sample in the droplet 300.

[0085] Furthermore, since the common electrode 150 is disposed on the flexible film 140, and the flexible film 140 has a certain degree of flexibility, when the second support structure 131 is compressed, the flexible film 140 and the common electrode 150 can undergo slight deformation, which improves the risk of rigid electrode breaking due to deformation and improves the durability and reliability of the chip.

[0086] Furthermore, the continuous flexible film 140 allows the gap between the second support structures 131 to be appropriately increased (e.g., increased to 1 μm to 5 μm), which reduces the requirements for photolithography process precision, increases the allowable range of the process, and is conducive to mass production.

[0087] In some embodiments, such as Figure 5 As shown, the flexible membrane 140 has at least one opening 141 that penetrates the flexible membrane 140 and is located in the area between adjacent detection units 120.

[0088] The detection unit 120 is formed by the intersection of the first electrode 121 and the second electrode 123, and is arranged in a grid-like array in a planar layout. The area between adjacent detection units 120 is the blank area of ​​the grid, which can include the following positions: the gap area between two adjacent first electrodes 121 along the first direction X, and the gap area between two adjacent second electrodes 123 along the second direction Y.

[0089] For example, the opening 141 is located in the central region enclosed by four adjacent detection units 120, that is, at the center of the rectangular or square blank area enclosed by two adjacent first electrodes 121 in the first direction X and two adjacent second electrodes 123 in the second direction Y.

[0090] The location of this opening has the following technical advantages: First, the opening 141 is located outside the movement path of the droplet 300. Under the action of the driving electrode 210, the droplet 300 mainly moves along the first direction X or the second direction Y, and its movement path typically passes above the detection unit 120 (i.e., the electrode intersection area). The opening 141 is positioned in the blank area between adjacent detection units 120, avoiding the main movement path of the droplet 300 and reducing the obstruction or interference caused by the opening 141 to the normal movement of the droplet 300. Second, the area below the opening 141 corresponds to the concentrated area of ​​the sacrificial layer material. During the fabrication process, the photoresist 133 and the second sacrificial layer 132 mainly fill the recessed area between adjacent detection units 120. Positioning the opening 141 here allows the removal liquid to directly act on the sacrificial layer material, improving removal efficiency and shortening process time. Third, the opening 141 is uniformly distributed on the chip surface, which facilitates the uniform diffusion of the removal liquid throughout the entire chip, ensuring that the sacrificial layer material in all areas can be completely removed.

[0091] The shape of the opening 141 can be set to a circle, a square, or a cross, such as a circle.

[0092] In some embodiments, the aforementioned hydrophobic layer is provided on the side of the common electrode 150 away from the substrate 110. The hydrophobic layer reduces the contact angle of the droplet 300 on the surface of the detection substrate 100, decreases the frictional force during droplet movement, and makes the droplet 300 easier to move under the action of the driving electrode 210, thereby improving the sensitivity and response speed of droplet manipulation. The thickness of the hydrophobic layer can be from 50 nm to 200 nm, ensuring good hydrophobicity without significantly affecting the deformation of the flexible film 140.

[0093] In some embodiments, an insulating layer (not shown) is further provided between the hydrophobic layer and the common electrode 150. The insulating layer may be made of silicon oxide (SiO2) or silicon nitride (SiN). xInorganic insulating materials such as aluminum oxide (Al2O3) are used, formed through atomic layer deposition (ALD) or plasma-enhanced chemical vapor deposition (PECVD) processes, with a thickness ranging from 50 nm to 200 nm. The insulating layer prevents electrical conduction between the common electrode 150 and the subsequently formed hydrophobic layer, while protecting the common electrode 150 from direct contact and electrochemical corrosion by the droplets 300, ensuring electrical isolation between the driving electric field and the detection signal. The insulating layer also enhances the chemical stability of the common electrode 150 surface, improving the long-term reliability of the chip.

[0094] Example 3

[0095] like Figure 1 As shown, this embodiment provides a microfluidic chip 10, including a driving substrate 200 and a detection substrate 100 as described in Embodiment 1 or Embodiment 2. The driving substrate 200 and the detection substrate 100 are disposed opposite to each other, with the detection substrate 100 located below the driving substrate 200. The driving substrate 200 is provided with a driving electrode 210 for driving the movement of a droplet 300. The driving electrode 210 can be in the form of a TFT array, a digital microfluidic electrode array, etc., and generates dielectric wetting force or electrophoretic force on the droplet 300 by applying voltage, thereby controlling the movement of the droplet 300 within the chip. The detection substrate 100, as described in Embodiment 1 or Embodiment 2, is used to detect the position of the droplet 300.

[0096] The operation of the microfluidic chip 10 is as follows: First, the droplet 300 to be analyzed is injected into the chip through the injection port, and the droplet 300 enters the space between the driving substrate 200 and the detection substrate 100. The control system applies voltage through the driving electrode 210 on the driving substrate 200 to drive the droplet 300 to move along a preset path. During the movement of the droplet 300, the detection substrate 100 monitors the position of the droplet 300 in real time. When the droplet 300 moves above a certain detection unit 120, the gravity of the droplet 300 acts on the second support structure 131 of the detection unit 120, causing the second electrode 123 to deform, resulting in a change in the electrical parameters (such as capacitance) of the detection unit 120. The detection circuit scans all detection units 120 on the detection substrate 100 and feeds back the position information of the electrical parameter changes to the control system. Based on the feedback position information, the control system adjusts the voltage timing of the subsequent driving electrode 210 to ensure that the droplet 300 moves accurately along the predetermined path. Once the droplet 300 reaches the target location, subsequent biochemical reactions or analytical detection can be performed.

[0097] The microfluidic chip 10 separates the droplet driving function and the position detection function onto different substrates. The driving substrate 200 is responsible for driving, and the detection substrate 100 is responsible for detection; the two work together. This architecture has the following advantages: the driving substrate 200 can use mature microfluidic driving technology without modification for the detection function; the detection substrate 100 can independently optimize detection performance, such as improving detection sensitivity and reducing power consumption; the overall chip structure is compact, highly integrated, and easy to implement multi-channel parallel detection and high-throughput analysis.

[0098] Example 4

[0099] like Figures 6 to 12 As shown, this embodiment provides a method for preparing a detection substrate 100 as described in Embodiment 1 or Embodiment 2 above, comprising the following steps:

[0100] In step S100, a detection unit 120 is formed on the substrate 110, such as... Figure 7 and Figure 8 As shown.

[0101] After cleaning the substrate 110, the detection unit 120 is fabricated. The detection unit 120 includes a first electrode 121, a first support structure 122, and a second electrode 123.

[0102] In step S110, a first electrode 121 is formed on the substrate 110. An indium tin oxide (ITO) thin film with a thickness of approximately 100 nm to 300 nm is deposited on the substrate 110 using a sputtering or evaporation process. Then, patterning is performed using a photolithography process: spin-coating photoresist, exposure and development to form the pattern of the first electrode 121, etching the indium tin oxide (ITO) with an acid etchant, and removing the photoresist to obtain a strip-shaped first electrode 121 extending along the first direction X. The linewidth and spacing of the first electrode 121 can be designed according to the detection resolution requirements, for example, a linewidth of 20 μm to 100 μm and a spacing of 20 μm to 100 μm.

[0103] In step S120, a first support structure 122 is formed on the first electrode 121. A silicon nitride (SiNx) thin film with a thickness of approximately 1 μm to 3 μm is deposited using plasma-enhanced chemical vapor deposition (PECVD). Then, a photolithography process is used for patterning: spin-coating photoresist, exposure and development to form the pattern of the first support structure 122, and reactive ion etching (RIE) to etch the silicon nitride (SiNx) to form a columnar first support structure 122. The first support structure 122 is located on the first electrode 121, and its cross-sectional shape can be rectangular or trapezoidal. For example, the first support structure 122 is trapezoidal, meaning the cross-sectional area of ​​the end in contact with the first electrode 121 is larger than the cross-sectional area of ​​the other end, to enhance the support stability for the second electrode 123. The height of the first support structure 122 determines the initial spacing between the first electrode 121 and the second electrode 123.

[0104] In step S130, a first sacrificial layer 124 is formed around the first support structure 122. A layer of photoresist or a thermally degradable material is spin-coated as the first sacrificial layer 124, with a thickness slightly higher than or equal to the height of the first support structure 122, for example, 0.5 μm to 1 μm higher. The first sacrificial layer 124 is patterned using photolithography to cover the area except for the top of the first support structure 122; that is, the first sacrificial layer 124 fills the gaps 125 between the first support structures 122, but exposes the top of the first support structure 122 for connection with the subsequent second electrode 123. The material of the first sacrificial layer 124 can be a soluble or thermally degradable material such as photoresist, polyimide, or polymethyl methacrylate. For example, photoresist is used as the first sacrificial layer because it is easy to coat and remove.

[0105] In step S140, a second electrode 123 is formed on the first support structure 122 and the first sacrificial layer 124. The second electrode 123 is a deformable electrode, comprising a flexible material layer 1231 and a conductive material layer 1232. First, a layer of polyimide (PI) solution is spin-coated and then thermally cured to form a polyimide (PI) film with a thickness of approximately 0.5 μm to 2 μm. The polyimide (PI) film covers the top of the first support structure 122 and the surface of the first sacrificial layer 124, and is tightly connected to the top of the first support structure 122. Then, an indium tin oxide (ITO) film with a thickness of approximately 100 nm to 200 nm is sputtered onto the polyimide (PI) film to form a conductive layer. The conductive material layer 1232 and the flexible material layer 1231 are patterned using photolithography: spin-coating photoresist, exposure and development to form the pattern of the second electrode 123, and etching the indium tin oxide (IOT) and polyimide (PI) with RIE to obtain a strip-shaped second electrode 123 extending along the second direction Y. The first direction X is perpendicular to the second direction Y, forming an array of intersection points. During the etching process, the etching depth needs to be controlled to reduce the damage to the first sacrificial layer 124 below.

[0106] Step S150: Remove the first sacrificial layer 124. Immerse the first sacrificial layer 124 (photoresist) in an organic solvent (such as acetone or N-methylpyrrolidone) to dissolve and remove it, creating a void 125 between the flexible material layer 1231 of the second electrode 123 and the substrate 110. During removal, the organic solvent seeps in from the edge region of the detection substrate 100 and gradually diffuses into the chip interior through the tiny channels between the first support structures 122. Since the first support structures 122 are spaced apart, they form a connected mesh of voids 125. The organic solvent flows along these voids 125, gradually dissolving the first sacrificial layer 124 material. The dissolved photoresist product flows out along the same path to the chip edge with the solvent, ultimately completely removing the sacrificial layer between the first support structures 122 within the entire detection unit 120 area, forming a connected open void 125. The gap 125 provides deformation space for the second electrode 123, allowing the second electrode 123 to deform towards the first electrode 121 under pressure, thereby changing the distance between the second electrode 123 and the first electrode 121. After removing the first sacrificial layer 124, the detection unit 120 is fabricated.

[0107] In step S200, a pressure transmission structure 130 is formed on the detection unit 120, such as... Figure 9 and Figure 10 or Figure 11 and Figure 12 As shown.

[0108] After the detection unit 120 is fabricated, the pressure transmission structure 130 is fabricated. The pressure transmission structure 130 includes multiple second support structures 131, as well as an optional flexible membrane 140 and a common electrode 150.

[0109] In step S210, photoresist 133 is filled in the area outside the detection unit 120, so that the recessed area between the detection units 120 is filled by the photoresist 133. A layer of photoresist is spin-coated and patterned by photolithography, so that the photoresist fills the gap area between adjacent first electrodes 121 and the gap area between adjacent second electrodes 123. Since the second electrode 123 is located above the first electrode 121, when filling the area between adjacent second electrodes 123, the photoresist 133 will naturally cover the area of ​​the first electrode 121 below. The photoresist 133 serves as a temporary support material, and its thickness can be equal to or higher than the height of the detection unit 120, for example, 1 μm to 3 μm higher, so as to facilitate the subsequent formation of the second support structure 131.

[0110] In step S220, a second sacrificial layer 132 is formed on the photoresist 133 and the detection unit 120. A layer of metal material, such as aluminum (Al), copper (Cu), titanium (Ti), or their alloys, is deposited as the second sacrificial layer 132 using a physical vapor deposition (PVD) process, with a thickness of approximately 2 μm to 5 μm, covering the surfaces of the photoresist 133 and the detection unit 120. The metal second sacrificial layer 132 is patterned using a photolithography process: spin-coating photoresist, exposure and development to form a pattern, and wet etching or dry etching to remove part of the metal, so that the second sacrificial layer 132 is retained in the area between adjacent detection units 120, while a window is formed in the area directly above the detection unit 120, with the bottom of the window exposing the detection unit 120 below (which can be the second electrode 123). The patterned second sacrificial layer 132 is distributed in a grid or strip shape, with its retained portion overlapping the adjacent detection units 120 on opposite sides, connecting the two detection units 120 like a bridge, while the area directly above the detection unit 120 is in a hollowed-out state. Using a metal material as the second sacrificial layer 132 has the following advantages: the metal and the subsequent second support structure 131 material (such as silicon nitride) have extremely high etching selectivity, which facilitates precise control of the pattern; the metal layer has good conductivity and can be used as an electrode in the subsequent electrochemical process; the metal layer can be quickly dissolved by acid solution, resulting in high removal efficiency.

[0111] In step S230, a second support structure 131 is formed within the second sacrificial layer 132 and the window. A rigid material, such as silicon nitride (SiNx), is deposited using chemical vapor deposition (CVD). The deposition thickness is less than the thickness of the second sacrificial layer 132, for example, 1 μm to 2 μm (the thickness of the second sacrificial layer 132 is 2 μm to 5 μm). This allows the silicon nitride to fill the bottom and sidewalls of the window and form a thin layer covering the surface of the second sacrificial layer 132. Because the deposition thickness is less than the thickness of the sacrificial layer, the window is not completely filled, but rather forms a groove-like structure consistent with the shape of the window. The silicon nitride layer is patterned using photolithography: photoresist is spin-coated, and exposure and development are performed to form the pattern of the second support structure 131. Reactive ion etching (RIE) is then used to etch the silicon nitride, removing the silicon nitride material from the surface of the second sacrificial layer 132, leaving only the silicon nitride at the bottom and sidewalls of the window to form the second support structure 131.

[0112] The shape of the window determines the shape of the second support structure 131. Since the window sidewalls are designed as inverted trapezoids, the resulting second support structure 131 has a shape with a gradually increasing cross-sectional area from the first electrode 121 to the second electrode 123, i.e., an inverted trapezoid or inverted cone shape that is wider at the top and narrower at the bottom, to enhance the pressure amplification effect. The second support structures 131 are spaced apart from each other, their positions corresponding one-to-one with the detection units 120, and the center of each second support structure 131 coincides with the center of its corresponding detection unit 120. After the second support structure 131 is formed, the second sacrificial layer 132 (metal) remains on the chip for support and protection in subsequent processes. This center-aligned design has the following technical effects: when the droplet 300 acts on the second support structure 131 by gravity, the pressure can be transmitted vertically and uniformly to the central region of the second electrode 123, causing symmetrical deformation of the second electrode 123, reducing torsional or non-uniform deformation of the second electrode 123 due to eccentric force, thereby improving the predictability of deformation and the stability of the detection signal.

[0113] In step S240, a flexible film 140 is formed on the second support structure 131 and the second sacrificial layer 132. A layer of polyimide (PI) solution is spin-coated and thermo-cured to form a polyimide (PI) film with a thickness of approximately 1 μm to 3 μm, covering the surfaces of the second support structure 131 and the second sacrificial layer 132. Since the photoresist 133 has filled all the recessed areas and the surface of the second sacrificial layer 132 is basically flat, the formed flexible film 140 is also flat and continuous, providing a good foundation for the subsequent installation of the common electrode 150 across the entire surface. The flexible film 140 has good flexibility and can adapt to subsequent deformation.

[0114] In step S250, at least one opening 141 is formed on the flexible film 140. At least one opening 141 is etched into the flexible film 140 using a photolithography process. The opening 141 penetrates the flexible film 140 and is located in the region between adjacent detection units 120. The position of the opening 141 corresponds to the channel for subsequent removal of the photoresist 133 and the second sacrificial layer 132; therefore, it is chosen to be on a non-droplet 300 movement path to reduce interference with the normal movement of the droplets 300. The shape of the opening 141 can be circular, square, or cross-shaped; for example, it can be circular to facilitate the flow and diffusion of the removal liquid.

[0115] In step S260, the photoresist 133 and the second sacrificial layer 132 are removed through opening 141. The second metal sacrificial layer 132 is dissolved and removed using an acid solution (such as a mixture of phosphoric acid, nitric acid, and acetic acid used to remove aluminum), and the photoresist 133 is dissolved and removed using an organic solvent (such as acetone). During the removal process, the removal solution enters the interior through opening 141, dissolving the metal sacrificial layer and the photoresist 133, allowing them to flow out from opening 141, ultimately forming gaps between and below the second support structures 131. After removing the photoresist 133 and the second sacrificial layer 132, the second support structure 131 is retained, with gaps around and below it, ensuring that the second support structure 131 can bear force independently without affecting each other. Removing the metal sacrificial layer with acid has advantages such as speed, thoroughness, and no damage to the silicon nitride support structure.

[0116] In step S270, a common electrode 150 is formed on the flexible film 140. A conductive layer of silver nanowires, with a thickness of approximately 100 nm to 200 nm, is formed on the flexible film 140 using a sputtering or coating process, serving as the common electrode 150. Since the surface of the flexible film 140 is flat and continuous, the common electrode 150 can be formed across the entire surface without the need for complex patterning processes. The silver nanowires possess good flexibility and conductivity, enabling them to adapt to minute deformations of the flexible film 140 without easily breaking. The common electrode 150 is patterned using photolithography to form the desired electrode pattern.

[0117] This preparation method uses a metallic material as the second sacrificial layer 132. Through physical vapor deposition and photolithography, an inverted trapezoidal or inverted conical opening 141 is precisely formed in the area directly above the detection unit 120, providing an ideal template for the subsequent formation of the second support structure 131, which is wider at the top and narrower at the bottom. The opening 141 is filled and patterned using chemical vapor deposition of silicon nitride, achieving precise control over the shape and position of the second support structure 131. This ensures that the center of each second support structure 131 coincides with the center of its corresponding detection unit 120, laying the foundation for uniform pressure transmission and signal stability. Simultaneously, before forming the second support structure 131, the recessed area outside the detection unit 120 is filled with photoresist 133 to flatten the chip surface, creating conditions for continuous film formation of the flexible film 140. Through the opening 141 on the flexible film 140, the second sacrificial metal layer 132 and photoresist 133 are removed using acid and organic solvents respectively, forming a complete gap between and below the second support structure 131. This ensures that the second support structure 131 is independently stressed and provides sufficient space for the deformation of the second electrode 123. The entire process flow is smooth, with good material etching selectivity, a wide process parameter window, and compatibility with existing drive substrate 200 fabrication processes, providing strong support for the large-scale production and widespread application of the microfluidic chip 10.

[0118] In the description of this specification, references to terms such as "some embodiments," "exemplarily," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. The illustrative expressions of the above terms in this specification do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0119] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application. Therefore, any changes or modifications made in accordance with the claims and description of this application should fall within the scope of this patent application.

Claims

1. A detection substrate, the detection substrate being used in a microfluidic chip, the microfluidic chip including a driving substrate disposed opposite to the detection substrate, characterized in that, The detection substrate is located below the driving substrate, and the detection substrate includes: Base; A pressure transmission structure is disposed on the substrate. The pressure transmission structure includes a plurality of second support structures. A flexible membrane and a common electrode are also provided on the side of the pressure transmission structure away from the substrate. The common electrode is provided on the side of the flexible membrane away from the substrate. A detection unit is disposed between the substrate and the pressure transmission structure, and is used to generate changes in electrical parameters in response to external pressure. The detection unit includes a first electrode and a second electrode disposed opposite to each other, and a first support structure disposed between the first electrode and the second electrode. The second electrode is a deformable electrode. The changes in electrical parameters include changes in capacitance between the first electrode and the second electrode. The first electrode is disposed on the substrate, the second electrode is disposed on the side of the first support structure away from the substrate, and the pressure transmission structure is disposed on the side of the second electrode away from the substrate. The second support structures are spaced apart from each other on the side of the second electrode away from the substrate, and the cross-sectional area of ​​the second support structures gradually increases from the first electrode to the second electrode. When the droplet is located between the driving substrate and the detection substrate, the gravity of the droplet is transmitted to the second electrode through the pressure transmission structure, causing the second electrode to deform toward the first electrode, thereby changing the distance between the second electrode and the first electrode, and thus changing the electrical parameters to determine the position of the droplet.

2. The detection substrate according to claim 1, characterized in that, The first electrode is a strip electrode extending along a first direction, and the second electrode is a strip electrode extending along a second direction, wherein the first direction and the second direction intersect.

3. The detection substrate according to claim 1, characterized in that, The flexible membrane has at least one opening that penetrates the flexible membrane and is located in the area between adjacent detection units.

4. A method for preparing a detection substrate as described in any one of claims 1 to 3, characterized in that, The method includes the following steps: Form detection units on the substrate; A pressure transmission structure is formed on the detection unit.

5. The method according to claim 4, characterized in that, The detection unit includes a first electrode, a second electrode, and a first support structure disposed between the first electrode and the second electrode, and there is a gap between the second electrode and the first electrode. The step of forming the detection unit on the substrate includes: The first electrode is formed on the substrate; The first support structure is formed on the first electrode; A first sacrificial layer is formed around the first support structure; A second electrode is formed on the first support structure and the first sacrificial layer, and the second electrode is a deformable electrode. Remove the first sacrificial layer to create a gap between the second electrode and the first electrode.

6. The method according to claim 4, characterized in that, After forming the detection unit, the method further includes: Photoresist is filled in the area outside the detection unit so that the recessed area between the detection units is filled with photoresist. A second sacrificial layer is formed on the photoresist and the detection unit; A second support structure is formed on the second sacrificial layer, the height of the second support structure is lower than the height of the second sacrificial layer, and the second support structure and the second sacrificial layer are arranged complementaryly in the horizontal direction; A flexible membrane is formed on the second support structure and the second sacrificial layer; At least one opening is formed on the flexible membrane, and the opening is located in the region between adjacent detection units; The photoresist and the second sacrificial layer are removed through the opening; A common electrode is formed on the flexible membrane.

7. A microfluidic chip, characterized in that, include: Drive substrate; as well as The detection substrate according to any one of claims 1 to 3, wherein the detection substrate is disposed opposite to the driving substrate and is located below the driving substrate, and the driving substrate is provided with a driving electrode for driving the movement of the droplet.

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