Field-effect transistor based on micro-fluidic chip and preparation method therefor, and biomarker detection method

Abstract

Provided in the present invention are a field-effect transistor based on a micro-fluidic chip and a preparation method therefor, and a biomarker detection method. The field-effect transistor based on a micro-fluidic chip comprises a substrate, a semiconductor material layer and a micro-fluidic chip, wherein the semiconductor material layer is arranged on the substrate; the micro-fluidic chip covers the semiconductor material layer; the micro-fluidic chip is provided with a central flow channel and an electrode channel; a low-melting-point metal layer is provided in the electrode channel, so as to form a source and a drain; and the part of the semiconductor material layer that is covered with the electrode channel is provided with the low-melting-point metal layer. The field-effect transistor based on a micro-fluidic chip in the present invention can recognize a biomarker, and has good sensitivity and a good specific recognition capability.

Description

Field-effect transistor based on microfluidic chip, preparation method thereof, and biomarker detection method Technical Field

[0001] The present invention relates to a field effect transistor based on a microfluidic chip, a preparation method thereof, and a biomarker detection method, and belongs to the technical field of semiconductors. Background Art

[0002] Biosensors based on field-effect transistors (FETs) offer advantages such as low cost, rapid response, and accurate detection. Their principle is as follows: a field-effect transistor consists of three electrodes: source, drain, and gate. A conductive channel material exists between the source and drain, and the current flowing between the source and drain is regulated by the electric field applied to the gate. By modifying the conductive channel material with specific receptors, it is functionalized to specifically capture target biomolecules. Graphene, with its excellent two-dimensional structure and optoelectronic properties, is an excellent conductive channel material. Graphene field-effect transistors (G-FETs) offer advantages such as high sensitivity, ease of integration, and large surface area. They hold promise for low-cost, portable, low-power, label-free, and highly sensitive rapid detection of biomarkers, making them suitable for both grassroots and on-site testing. However, current G-FET biosensors have complex structures and manufacturing processes, and the photolithography steps are tedious and time-consuming, which can easily damage the graphene structure. Most biochemical reactions occur in ionic solutions, which places high demands on G-FET packaging. Consequently, high cost, complex processes, and inconsistent efficiency have severely limited the potential application of G-FETs in biomarker detection. The rapid advancement of micro- and nanofabrication technologies has opened up new avenues for constructing novel biosensors with simple systems, low costs, short fabrication times, and high precision.

[0003] The structure of traditional graphene field-effect transistors is complex and requires at least two photolithography processes. Layer-by-layer overlay has high process requirements, low yield, high cost, and is easy to damage the structure of graphene, causing device performance to decline. In addition, in most cases, the detection area is a static area, which is not conducive to the reaction, resulting in low reaction efficiency, and is prone to residual other liquids, causing distortion of the detection results. For example, CN114264712A discloses a miRNA detection method based on graphene field-effect transistors and its application. This graphene field-effect transistor can only detect 10pM biological targets, and the detection process is complicated, making it difficult to put into practical use.

[0004] Microfluidics-based graphene field-effect transistors (GFETs) also exist in the prior art. For example, CN107051601A discloses a GFET-based microfluidic chip for nucleic acid detection and its preparation method. However, this device still has several shortcomings: 1. It still utilizes traditional micro-nanofabrication techniques, requiring photolithography to fabricate the electrodes. This not only increases fabrication difficulty and cost, but also damages the graphene, leaving chemical residues on the surface, impacting device performance. 2. The device's structure lacks complete encapsulation, requiring a hole in the center of the flow channel to insert an Ag / AgCl electrode wire as a gate. Furthermore, because the PDMS microfluidic channel sheet directly overlies the device electrodes, the PDMS and gold electrodes exhibit poor bonding, easily damaging the gold electrodes and resulting in a loose bond between the substrate and the GFET. Furthermore, the device lacks a clamp for secure clamping, which can lead to leakage. 3. For DNA detection, the device requires Au nanoparticles to modify the graphene, and immersing the device in chemical reagents can damage the device.

[0005] In summary, the current biosensors based on graphene field-effect transistors have the following main disadvantages: 1. Most biosensors based on graphene field-effect transistors place a micro-reaction area on the surface of the device channel, and the solution is replaced by a syringe. It has two main disadvantages. The first is that the static solution is not easy to react with graphene, and biological molecules are not easy to connect to graphene; the second is that the syringe cannot completely absorb all the solution in the reaction chamber, and the reaction molecules are easy to remain, causing concentration deviation and affecting the test results. 2. Biosensors based on graphene field-effect transistors generally have a multi-layer structure, and their preparation process requires at least two photolithography processes. The photolithography process is not only time-consuming and labor-intensive, but also requires layer-by-layer photolithography, which is also very complicated. The photolithography process needs to be repeated for each biological test.

[0006] Therefore, developing a new type of field-effect transistor for biomarker detection remains one of the urgent problems to be solved in this field.

[0007] Summary of the Invention

[0008] To address the above technical issues, the present invention provides a microfluidic chip-based field-effect transistor and a method for preparing the same. The microfluidic chip-based field-effect transistor of the present invention offers the advantages of modularity and simplicity, can be used to identify biomarkers, and exhibits excellent sensitivity and specificity.

[0009] Another object of the present invention is to provide a method for detecting biomarkers, which uses the above-mentioned field-effect transistor based on the microfluidic chip to detect biomarkers.

[0010] In order to achieve the above-mentioned object, the first aspect of the present invention provides a field effect transistor based on a microfluidic chip, which comprises: a substrate, a semiconductor material layer and a microfluidic chip;

[0011] The semiconductor material layer is provided on the substrate; the microfluidic chip is covered on the semiconductor material layer;

[0012] The microfluidic chip is provided with a central flow channel and a plurality of electrode channels;

[0013] Each pair of electrode channels includes a first electrode channel and a second electrode channel, the first electrode channel and the second electrode channel are respectively arranged on both sides of the central flow channel; the ends of the first electrode channel and the second electrode channel are respectively provided with a wire socket; the first electrode channel and the second electrode channel are both provided with a low melting point metal layer to form a source electrode and a drain electrode;

[0014] The electrode channel is in contact with the semiconductor material layer, and a low-melting-point metal layer is provided on a portion of the semiconductor material layer covered by the electrode channel;

[0015] One end of the central flow channel is a liquid inlet, and the other end is a liquid outlet; a metal electrode is inserted into the liquid inlet of the central flow channel, and the metal electrode serves as a conductive electrode of the gate;

[0016] The central flow channel is in contact with the semiconductor material layer.

[0017] In the above-mentioned field effect transistor based on the microfluidic chip, preferably, the substrate comprises a silicon wafer having an insulating layer.

[0018] In the above-mentioned field-effect transistor based on the microfluidic chip, preferably, the semiconductor material layer is a layer formed of a semiconductor material, and the semiconductor material includes one or a combination of graphene, black phosphorus, carbon nanotubes, molybdenum disulfide, and organic semiconductor materials. More preferably, the semiconductor material is graphene.

[0019] In the above-mentioned field effect transistor based on the microfluidic chip, preferably, the material of the microfluidic chip includes polydimethylsiloxane (PDMS).

[0020] In the above-mentioned field effect transistor based on the microfluidic chip, preferably, the first electrode channel and the second electrode channel are symmetrically distributed with the central flow channel as the symmetry axis.

[0021] In the above-mentioned field effect transistor based on the microfluidic chip, preferably, the ends of the first electrode channel and the second electrode channel are further provided with a low-melting-point metal inlet respectively.

[0022] In the above-mentioned field effect transistor based on the microfluidic chip, preferably, the low-melting-point metal layer is a layer formed of a low-melting-point metal. More preferably, the low-melting-point metal comprises a tin-indium alloy.

[0023] According to a specific embodiment of the present invention, preferably, the above-mentioned field effect transistor based on the microfluidic chip further includes: a plurality of wires, one end of each of which is respectively arranged in the wire sockets of the first electrode channel and the second electrode channel, and is at least partially located in the low-melting-point metal layer.

[0024] In the above-mentioned field effect transistor based on the microfluidic chip, preferably, the area where the semiconductor material layer contacts the central flow channel is covered with ionic liquid, and the ionic liquid contacts the metal electrode; the metal electrode and the ionic liquid form an ionic liquid gate.

[0025] According to a specific embodiment of the present invention, preferably, the above-mentioned field effect transistor based on the microfluidic chip further includes: a clamp, which is used to fix and clamp the substrate and the microfluidic chip.

[0026] A second aspect of the present invention provides a method for preparing the above-mentioned field effect transistor based on the microfluidic chip, which comprises the following steps:

[0027] (1) forming a semiconductor material layer on a substrate;

[0028] (2) preparing a microfluidic chip having a central flow channel and a plurality of electrode channels;

[0029] (3) assembling the substrate with the semiconductor material layer obtained in step (1) and the microfluidic chip obtained in step (2);

[0030] (4) forming a low melting point metal layer in the electrode channel and in the portion of the semiconductor material layer covered by the electrode channel to obtain a source electrode and a drain electrode;

[0031] (5) Inserting a metal electrode into the liquid inlet of the central flow channel to form a conductive electrode of the gate, thereby obtaining the field effect transistor based on the microfluidic chip.

[0032] In the above preparation method, preferably, step (2) specifically includes: preparing a positive mold of the microfluidic chip by micro-nano processing technology; and then using the positive mold to prepare the microfluidic chip by a reverse molding method using polydimethylsiloxane.

[0033] In the above preparation method, preferably, step (3) specifically includes: covering the microfluidic chip obtained in step (2) on the substrate formed with the semiconductor material layer obtained in step (1), and then fixing and clamping them with a clamp.

[0034] According to a specific embodiment of the present invention, preferably, the above preparation method further comprises, before forming the low-melting-point metal layer in step (4), inserting one end of a plurality of wires into the wire sockets of the first electrode channel and the second electrode channel respectively.

[0035] In the above preparation method, preferably, step (4) specifically includes: inserting one end of a plurality of wires into the wire sockets of the first electrode channel and the second electrode channel respectively; passing the low-melting-point metal into the electrode channel through the low-melting-point metal inlet provided at the end of the first electrode channel and the second electrode channel, the liquid low-melting-point metal flows in the electrode channel and contacts the portion of the semiconductor material layer covered by the electrode channel, and flows to the wire socket and contacts the wire, after the liquid low-melting-point metal solidifies into a solid state, a low-melting-point metal layer is formed to obtain a source and a drain, and at least a portion of the wire located in the wire socket is wrapped in the low-melting-point metal layer.

[0036] In the above preparation method, preferably, step (5) further includes: introducing ionic liquid into the central flow channel through the liquid inlet of the central flow channel, the ionic liquid covers the area where the semiconductor material layer contacts the central flow channel, and the ionic liquid contacts the metal electrode, and the metal electrode and the ionic liquid form an ionic liquid gate.

[0037] A third aspect of the present invention provides a biomarker detection method, comprising the following steps:

[0038] An ionic liquid containing a biomarker is injected through the liquid inlet of the central flow channel of the field effect transistor based on the microfluidic chip, and the ionic liquid containing the biomarker flows through the semiconductor material layer to detect the biomarker.

[0039] According to a specific embodiment of the present invention, preferably, the above-mentioned biomarker detection method specifically includes the following steps: injecting a solution containing a functionalized modifier through the liquid inlet of the central flow channel of the field-effect transistor based on the microfluidic chip to functionally modify the semiconductor material layer, and then injecting an ionic liquid containing a biomarker, and the functionalized modified semiconductor material layer captures the biomarker, and then detecting the biomarker.

[0040] In the above-mentioned biomarker detection method, preferably, the biomarker includes one or a combination of DNA, RNA and protein molecules.

[0041] The present invention provides a microfluidic chip-based field-effect transistor, a method for preparing the same, and a method for detecting biomarkers. The microfluidic chip-based field-effect transistor has the advantages of modularity and simplicity, reducing costs. Furthermore, the field-effect transistor is a fully encapsulated device, isolating the device from the external water and oxygen environment while effectively isolating the ionic liquid gate and source and drain electrodes. Furthermore, the preparation process for the microfluidic chip-based field-effect transistor is simple, shortening preparation time and minimizing damage to the semiconductor material layer. Consequently, the microfluidic chip-based field-effect transistor exhibits excellent electrical performance and high stability, avoiding the effects of operating conditions. Furthermore, the microfluidic chip-based field-effect transistor combines the advantages of a microfluidic chip, enabling solutions to modify the semiconductor material layer in a flowing state while also being washable and capable of quantitatively controlling ionic liquids containing biomarkers. The microfluidic chip-based field-effect transistor can detect different biomarkers based on different sensing mechanisms, demonstrating excellent sensitivity and specific recognition capabilities.

[0042] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0043] (1) The present invention simplifies the preparation process of the field effect transistor based on the microfluidic chip, optimizes its performance, and successfully integrates the electrodes, microfluidic channels and test wires into one device, thereby obtaining an integrated biosensor test platform. (2) The field effect transistor based on the microfluidic chip of the present invention has good airtightness and obvious characteristics of the microfluidic chip technology. During use, it can isolate the external water and oxygen environment and can quantitatively control the ionic liquid containing biomarkers. (3) The present invention can effectively protect the semiconductor material layer, reduce the damage to the semiconductor material layer caused by chemical reagents and photolithography technology, and make the field effect transistor based on the microfluidic chip of the present invention have better electrical performance and stability. (4) Using the field effect transistor based on the microfluidic chip of the present invention, high-sensitivity biomarker recognition can be achieved, and a complementary chain of 10fM and a non-complementary chain with only one base mutation can be successfully distinguished; at the same time, it also has the advantages of short detection time, convenience and rapidity. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG1 shows a schematic structural diagram of a field effect transistor based on a microfluidic chip in some specific embodiments of the present invention.

[0045] FIG2 shows a schematic structural diagram of the central flow channel and the electrode channel in some specific embodiments of the present invention.

[0046] FIG3 shows a schematic structural diagram of a clamp in some specific embodiments of the present invention.

[0047] FIG4 shows a schematic flow chart of a method for preparing a field effect transistor based on a microfluidic chip in some specific embodiments of the present invention.

[0048] FIG5 shows the mold mask layout of the microfluidic chip manufactured in Example 1.

[0049] FIG6 shows the Raman spectrum detection results of the graphene in the substrate having the semiconductor material layer formed thereon obtained in step (1) of Example 1 and the graphene in the graphene field effect transistor of Comparative Example 1.

[0050] FIG7 shows the electrical performance test results of the field effect transistor based on the microfluidic chip of Example 1.

[0051] FIG8 shows a comparison of the electrical properties of Example 1 and Comparative Example 1.

[0052] FIG9 shows a specificity detection graph and a sensitivity detection graph in Example 2.

[0053] Explanation of the accompanying drawings: 1-substrate; 2-semiconductor material layer; 3-microfluidic chip; 4-clamp; 301-central flow channel; 302-electrode channel; 303-first electrode channel; 304-second electrode channel; 305-wire socket; 306-low-melting-point metal layer; 307-liquid inlet; 308-liquid outlet; 309-low-melting-point metal inlet; 310-wire. DETAILED DESCRIPTION

[0054] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0055] In some specific embodiments of the present invention, the present invention provides a field effect transistor based on a microfluidic chip, as shown in FIG1 and FIG2 , which includes: a substrate 1, a semiconductor material layer 2 and a microfluidic chip 3;

[0056] A semiconductor material layer 2 is provided on the substrate 1; a microfluidic chip 3 is covered on the semiconductor material layer 2;

[0057] The microfluidic chip 3 is provided with a central flow channel 301 and a plurality of electrode channels 302;

[0058] Each pair of electrode channels 302 includes a first electrode channel 303 and a second electrode channel 304, which are respectively arranged on either side of the central flow channel 301; a wire socket 305 is respectively provided at the end of each of the first electrode channel 303 and the second electrode channel 304; a low-melting-point metal layer 306 is provided in each of the first electrode channel 303 and the second electrode channel 304 to form a source and a drain;

[0059] The electrode channel 302 is in contact with the semiconductor material layer 2, and a low-melting-point metal layer 306 is provided on the portion of the semiconductor material layer 2 covered by the electrode channel 302;

[0060] One end of the central channel 301 is a liquid inlet 307 and the other end is a liquid outlet 308. A metal electrode is inserted into the liquid inlet 307 of the central channel 301, and the metal electrode serves as a conductive electrode of the gate.

[0061] The central flow channel 301 is in contact with the semiconductor material layer 2 .

[0062] In some embodiments, the substrate 1 may include a silicon wafer having an insulating layer. The insulating layer may be made of, but not limited to, silicon dioxide, tantalum pentoxide, or aluminum oxide, preferably silicon dioxide.

[0063] In some embodiments, the semiconductor material layer 2 is a layer formed of a semiconductor material, and the semiconductor material may include one or a combination of graphene, black phosphorus, carbon nanotubes, molybdenum disulfide, and organic semiconductor materials, etc. Preferably, the semiconductor material is graphene.

[0064] In some embodiments, the material of the microfluidic chip 3 includes PDMS.

[0065] In some embodiments, as shown in FIG. 2 , the first electrode channel 303 and the second electrode channel 304 are symmetrically distributed with the central flow channel 301 as the symmetry axis.

[0066] In some embodiments, as shown in FIG. 2 , the number of electrode channels 302 is three pairs.

[0067] In some embodiments, as shown in FIG. 2 , a low-melting-point metal inlet 309 is further provided at the end of each of the first electrode channel 303 and the second electrode channel 304 .

[0068] In some embodiments, the low-melting-point metal layer 306 is a layer formed of a low-melting-point metal. Preferably, the low-melting-point metal includes a tin-indium alloy.

[0069] In some embodiments, the microfluidic chip-based field effect transistor further includes: a plurality of wires 310 , one end of each wire 310 being disposed in the wire sockets 305 of the first electrode channel 303 and the second electrode channel 304 , and at least partially located in the low-melting-point metal layer 306 .

[0070] In some embodiments, the metal electrode is, for example but not limited to, a hollow gold needle.

[0071] In some embodiments, the area of ​​the semiconductor material layer 2 in contact with the central flow channel 301 is covered with an ionic liquid, and the ionic liquid is in contact with a metal electrode; the metal electrode and the ionic liquid form an ionic liquid gate. Those skilled in the art will understand that, generally speaking, the field-effect transistor based on the microfluidic chip of the present invention is in contact with the ionic liquid, thereby forming a gate, only when it is used, that is, when it is used for biomarker detection.

[0072] In some embodiments, the microfluidic chip-based field-effect transistor further includes a fixture 4 for securing and clamping the substrate 1 and the microfluidic chip 3. The fixture 4 may include, for example but not limited to, an upper fixture (left image in FIG3 ) and a lower fixture (right image in FIG3 ), the upper fixture being provided with at least openings corresponding to a liquid inlet 307 , a liquid outlet 308 , a wire jack 305 , and a low-melting-point metal inlet 309 . The upper fixture and the lower fixture are connected to secure and clamp the substrate 1 and the microfluidic chip 3 .

[0073] In other specific embodiments of the present invention, the present invention further provides a method for preparing the above-mentioned field effect transistor based on the microfluidic chip, as shown in FIG4 , which comprises the following steps:

[0074] (1) forming a semiconductor material layer 2 on a substrate 1;

[0075] (2) preparing a microfluidic chip 3 having a central flow channel 301 and a plurality of electrode channels 302;

[0076] (3) assembling the substrate 1 formed with the semiconductor material layer 2 obtained in step (1) and the microfluidic chip 3 obtained in step (2);

[0077] (4) forming a low melting point metal layer 306 in the electrode channel 302 and in the portion of the semiconductor material layer 2 covered by the electrode channel 302 to obtain a source electrode and a drain electrode;

[0078] (5) Inserting a metal electrode into the liquid inlet 307 of the central flow channel 301 to form a conductive electrode of the gate, thereby obtaining a field effect transistor based on the microfluidic chip.

[0079] In some embodiments, in step (1), the method of forming the semiconductor material layer 2 on the substrate 1 may include: directly growing a semiconductor material on the substrate 1 to form the semiconductor material layer 2, or, after preparing the semiconductor material, transferring the prepared semiconductor material to the substrate 1 to form the semiconductor material layer 2. Preferably, when the semiconductor material is graphene, the semiconductor material layer 2 is formed on the substrate 1 by wet transfer.

[0080] In some embodiments, step (2) specifically includes: preparing a positive mold of the microfluidic chip 3 by micro-nano processing technology; then using the positive mold, using polydimethylsiloxane to prepare the microfluidic chip 3 by the reverse molding method. Specifically, in the process of preparing the positive mold of the microfluidic chip 3, the layout of the photolithography mask of the designed microfluidic structure can be drawn by software, and then the photolithography mask is made. Then, the photolithography mask is used to prepare a positive mold with a protruding microfluidic structure on a silicon wafer (e.g., a silicon / silicon dioxide wafer) by micro-nano processing technology. In the process of preparing the microfluidic chip 3, PDMS and a curing agent can be mixed in a suitable ratio (e.g., a mass ratio of 10:1) and poured onto the prepared positive mold. After curing and forming, a PDMS negative mold is obtained. The PDMS negative mold is cut into the desired shape and size, and holes are punched at specific positions to form a liquid inlet 307, a liquid outlet 308, a wire socket 305 and a low-melting-point metal inlet 309, thereby obtaining the microfluidic chip 3.

[0081] In some embodiments, step (3) specifically includes: covering the microfluidic chip 3 obtained in step (2) on the substrate 3 formed with the semiconductor material layer 2 obtained in step (1), and then fixing and clamping them with a clamp 4.

[0082] In some embodiments, before forming the low-melting-point metal layer 306 in step (4) of the preparation method, the step further includes: inserting one end of a plurality of wires 310 into the wire sockets 305 of the first electrode channel 303 and the second electrode channel 304 respectively.

[0083] In some embodiments, step (4) specifically includes: inserting one end of several wires 310 into the wire sockets 305 of the first electrode channel 303 and the second electrode channel 304 respectively; passing the low-melting-point metal into the electrode channel 302 through the low-melting-point metal inlet 309 set at the end of the first electrode channel 303 and the second electrode channel 302, and the liquid low-melting-point metal flows in the electrode channel 302 and contacts the part of the semiconductor material layer 2 covered by the electrode channel, and flows to the wire socket 305 and contacts the wire 310. After the liquid low-melting-point metal solidifies into a solid state, a low-melting-point metal layer 306 is formed to obtain a source and a drain, and at least a portion of the wire 310 located in the wire socket 305 is wrapped in the low-melting-point metal layer 306.

[0084] In some embodiments, step (5) further includes: introducing the ionic liquid into the central flow channel 301 through the liquid inlet 307 of the central flow channel 301, the ionic liquid covers the area where the semiconductor material layer 2 contacts the central flow channel 301, and the ionic liquid contacts the metal electrode, and the metal electrode and the ionic liquid form an ionic liquid gate.

[0085] In some further specific embodiments of the present invention, the present invention further provides a biomarker detection method, which comprises the following steps:

[0086] The ionic liquid containing the biomarker is injected through the liquid inlet 307 of the central flow channel 301 of the field effect transistor based on the microfluidic chip, and the ionic liquid containing the biomarker flows through the semiconductor material layer 2 to perform the detection of the biomarker.

[0087] In some embodiments, the biomarker detection method specifically includes the following steps: injecting a solution containing a functionalized modifier through the liquid inlet 307 of the central flow channel 301 of the field effect transistor based on the microfluidic chip to functionally modify the semiconductor material layer 2, and then injecting an ionic liquid containing a biomarker, and the functionalized modified semiconductor material layer 2 captures the biomarker, thereby detecting the biomarker.

[0088] In some embodiments, the functionalized modifier includes 1-pyrenebutanoic acid succinimidyl ester (PBSE) and a DNA probe.

[0089] In some embodiments, the biomarkers include one or a combination of DNA, RNA, and protein molecules.

[0090] The technical solutions of the present invention are specifically described below through examples and comparative examples, but the present invention is not limited to these examples and can of course be implemented with various modifications within the scope of the gist of the present invention.

[0091] Example 1

[0092] This embodiment provides a field effect transistor based on a microfluidic chip, as shown in FIG1 , FIG2 and FIG3 , which includes: a substrate 1 , a semiconductor material layer 2 , a microfluidic chip 3 , a fixture 4 and a plurality of wires 310 ;

[0093] A semiconductor material layer 2 is provided on the substrate 1; a microfluidic chip 3 is covered on the semiconductor material layer 2;

[0094] The microfluidic chip 3 is provided with a central flow channel 301 and three pairs of electrode channels 302;

[0095] Each pair of electrode channels 302 includes a first electrode channel 303 and a second electrode channel 304, which are symmetrically distributed with the central flow channel 301 as the axis of symmetry. The ends of the first electrode channel 303 and the second electrode channel 304 are respectively provided with a wire socket 305 and a low-melting-point metal inlet 309. A low-melting-point metal layer 306 is provided in each of the first electrode channel 303 and the second electrode channel 304 to form a source and a drain. One end of a plurality of wires 310 is respectively provided in the wire socket 305 of the first electrode channel 303 and the second electrode channel 304, and at least a portion of one end of the plurality of wires 310 is located in the low-melting-point metal layer 306.

[0096] The electrode channel 302 is in contact with the semiconductor material layer 2, and a low-melting-point metal layer 306 is provided on the portion of the semiconductor material layer 2 covered by the electrode channel 302;

[0097] One end of the central channel 301 is a liquid inlet 307 and the other end is a liquid outlet 308. A metal electrode is inserted into the liquid inlet 307 of the central channel 301, and the metal electrode serves as a conductive electrode of the gate.

[0098] The central flow channel 301 is in contact with the semiconductor material layer 2;

[0099] The fixture 4 is used to fix and clamp the substrate 1 and the microfluidic chip 3 , and its structure is shown in FIG3 .

[0100] In this embodiment, the width of the central channel 301 is 50 μm-300 μm.

[0101] In this embodiment, the substrate 1 is a silicon wafer having an insulating layer made of silicon dioxide.

[0102] In this embodiment, the semiconductor material layer 2 is a layer formed of a semiconductor material, and the semiconductor material is graphene.

[0103] In this embodiment, the material of the microfluidic chip 3 includes PDMS.

[0104] In this embodiment, the low-melting-point metal layer 306 is a layer formed of a low-melting-point metal, and the low-melting-point metal is a tin-indium alloy.

[0105] In this embodiment, as shown in FIG3 , the fixture 4 specifically includes an upper fixture (left image in FIG3 ) and a lower fixture (right image in FIG3 ). The upper fixture is provided with at least openings corresponding to a liquid inlet 307, a liquid outlet 308, a wire jack 305, and a low-melting-point metal inlet 309. The upper fixture and the lower fixture are connected to secure and clamp the substrate 1 and the microfluidic chip 3.

[0106] In this embodiment, the metal electrodes are hollow gold needles.

[0107] In this embodiment, when the field effect transistor based on the microfluidic chip is used, the area where the semiconductor material layer 2 contacts the central channel 301 is covered with ionic liquid, and the ionic liquid contacts the metal electrode; the metal electrode and the ionic liquid form an ionic liquid gate.

[0108] This embodiment also provides a method for preparing the above-mentioned field effect transistor based on the microfluidic chip, as shown in FIG4 , which includes the following steps:

[0109] (1) forming a semiconductor material layer 2 on a substrate 1;

[0110] (2) preparing a microfluidic chip 3 having a central flow channel 301 and a plurality of electrode channels 302;

[0111] (3) assembling the substrate 1 formed with the semiconductor material layer 2 obtained in step (1) and the microfluidic chip 3 obtained in step (2);

[0112] (4) forming a low melting point metal layer 306 in the electrode channel 302 and in the portion of the semiconductor material layer 2 covered by the electrode channel 302 to obtain a source electrode and a drain electrode;

[0113] (5) Inserting a metal electrode into the liquid inlet 307 of the central flow channel 301 to form a conductive electrode of the gate, thereby obtaining a field effect transistor based on the microfluidic chip.

[0114] Wherein, step (1) specifically includes:

[0115] (a) Graphene was grown on copper foil using a commercially available chemical vapor deposition method. A polymethyl methacrylate (PMMA) solution was spin-coated on the graphene surface at 4000 rpm for 1 min. The surface was then heated at 170°C until the water in the PMMA solution evaporated completely, forming a PMMA protective layer approximately 200 nm thick on the graphene surface.

[0116] (b) The copper foil was cut into a 0.5 cm × 1.5 cm rectangle and placed in an ammonium persulfate solution with the PMMA protective layer facing upward for etching. When the copper was completely etched, the solution changed from colorless to light blue, and the transparent and colorless PMMA / graphene film floated on the surface of the solution.

[0117] (c) The solution was essentially drained using a pipette, leaving a small amount of solution to float the film, and then ultrapure water was added and washed repeatedly at least four times. A 4-inch silicon / silicon dioxide wafer (with a 300 nm thick silicon dioxide insulating layer on the surface) was used as a substrate and ultrasonically cleaned in acetone, isopropyl alcohol, and deionized water for 15 min in sequence. The PMMA / graphene film was then removed from the water using the cleaned silicon / silicon dioxide wafer and allowed to air dry.

[0118] (d) The silicon / silicon dioxide wafer with the PMMA / graphene film was heated at 90° C. for 30 min and then at 130° C. for 30 min; then, it was immersed in acetone for 4 h to completely remove the PMMA protective layer from the graphene surface. The wafer was then rinsed with isopropyl alcohol and deionized water, and then dried with nitrogen gas to obtain a substrate 1 having a semiconductor material layer 2 (i.e., a graphene layer).

[0119] Step (2) specifically includes:

[0120] (e) Using CAD, a photolithography mask layout of the designed microfluidic structure (i.e., the structure having a central flow channel 301 and three pairs of electrode channels 302 as described above) is drawn, as shown in FIG5 , and then a photolithography mask is manufactured;

[0121] (f) An 8-inch silicon / silicon dioxide wafer was ultrasonically cleaned with acetone, isopropyl alcohol, and deionized water for 15 min, respectively. The cleaned silicon / silicon dioxide wafer was placed in the center of a spin coater and fixed. SU-8 3050 photoresist was spin-coated on the surface of the silicon / silicon dioxide wafer using a two-step spin coating process: the first step was at 500 rpm for 20 s, and the second step was at 3000 rpm for 30 s.

[0122] (g) Placing the silicon / silicon dioxide wafer after spin-coating the photoresist on a hot plate and heating it at 95°C for 25 minutes to complete pre-baking;

[0123] (h) placing the photomask in the corresponding position of the photolithography machine, and then placing the pre-baked silicon / silicon dioxide wafer in the corresponding position of the photolithography machine. The photolithography machine uses direct contact lithography mode and exposes the silicon / silicon dioxide wafer to ultraviolet light for 12 seconds;

[0124] (i) placing the exposed silicon / silicon dioxide wafer on a hot plate, heating it at 95°C for 30 minutes, and then baking it;

[0125] (j) developing the post-baked silicon / silicon dioxide wafer in a negative photoresist developer for 20 seconds;

[0126] (k) Placing the developed silicon / silicon dioxide wafer on a hot plate and heating it at 150° C. for 30 min to harden the mold, thereby obtaining a positive mold of the microfluidic chip 3;

[0127] The above steps complete the preparation of the positive mold of the microfluidic chip 3, which has a raised microfluidic structure with an average height of 50 μm. The positive mold can be reused, avoiding the need for photolithography each time a field effect transistor based on the microfluidic chip is prepared.

[0128] (1) Take 50g of PDMS and 5g of curing agent, mix them evenly, and pour them evenly on the male mold;

[0129] (m) The male mold containing the mixture of PDMS and curing agent is evacuated in a sealed environment for 2 hours to remove bubbles in the mixture of PDMS and curing agent; then, the mold is baked in an environment of 80° C. for 20 minutes to solidify the PDMS;

[0130] (n) The solidified PDMS is peeled off from the male mold to obtain a female PDMS mold. The female PDMS mold is cut into the desired shape and size, and holes are punched at specific locations using a punch to form a liquid inlet 307, a liquid outlet 308, a wire socket 305, and a low-melting-point metal inlet 309, thereby obtaining a microfluidic chip 3.

[0131] The microfluidic chip 3 has a concave microfluidic structure. The overall height of the microfluidic chip 3 is 50 μm. The width of the central flow channel 301 is 50 μm-300 μm. Different microfluidic structures can be designed based on the embodiments of the present invention to obtain positive molds with different microfluidic structures, thereby obtaining microfluidic chips 3 with different microfluidic structures.

[0132] Step (3) specifically includes:

[0133] (o) Covering the microfluidic chip 3 obtained in step (2) with the microfluidic structure on the substrate 3 formed with the semiconductor material layer 2 obtained in step (1), and then fixing and clamping them with a clamp 4 to obtain a package body.

[0134] Step (4) specifically includes:

[0135] (p) Inserting one end of a plurality of wires 310 into the wire sockets 305 of the first electrode channel 303 and the second electrode channel 304, respectively; then injecting a low-melting-point metal (i.e., a tin-indium alloy with a melting point of 85°C) into the electrode channel 302 through the low-melting-point metal inlet 309 provided at the ends of the first electrode channel 303 and the second electrode channel 302; heating the package to 90°C to convert the tin-indium alloy into liquid metal; the liquid low-melting-point metal flows in the electrode channel 302 and contacts the portion of the semiconductor material layer 2 covered by the electrode channel; and flows to the wire socket 305 and contacts the wire 310; after cooling, the liquid low-melting-point metal solidifies into a solid state to form a low-melting-point metal layer 306, thereby obtaining a source and a drain; and at least a portion of the wire 310 located in the wire socket 305 is wrapped in the low-melting-point metal layer 306.

[0136] Step (5) specifically includes:

[0137] (q) inserting a metal electrode into the liquid inlet 307 of the central flow channel 301 to form a conductive electrode of the gate for applying electric field control to obtain a field effect transistor based on the microfluidic chip;

[0138] (r) When using the field effect transistor based on the microfluidic chip, the ionic liquid is introduced into the central flow channel 301 through the liquid inlet 307 of the central flow channel 301. The ionic liquid covers the area where the semiconductor material layer 2 contacts the central flow channel 301, and the ionic liquid contacts the metal electrode. The metal electrode and the ionic liquid form an ionic liquid gate.

[0139] Comparative Example 1

[0140] This comparative example provides a graphene field-effect transistor based on a microfluidic chip.

[0141] The graphene field-effect transistor based on a microfluidic chip includes: a substrate, a graphene layer, a source electrode, a drain electrode, an electric wire and a microfluidic chip; a graphene layer is provided on the substrate; a source electrode and a drain electrode are respectively provided at two ends of the surface of the graphene layer; the source electrode and the drain electrode are respectively connected to electric wires; the microfluidic chip has a central flow channel, the microfluidic chip is covered on the graphene layer, and the central flow channel contacts the graphene layer between the source electrode and the drain electrode; one end of the central flow channel is a liquid inlet and the other end is a liquid outlet; a metal electrode is inserted into the liquid inlet of the central flow channel, the metal electrode is a hollow gold needle, and the metal electrode serves as a conductive electrode of the gate; when in use, the area where the graphene layer contacts the central flow channel is covered with ionic liquid, and the ionic liquid contacts the metal electrode, and the metal electrode and the ionic liquid form an ionic liquid gate.

[0142] The preparation method of the graphene field-effect transistor based on the microfluidic chip comprises the following steps:

[0143] (1) Forming a graphene layer on a substrate

[0144] A graphene layer was formed on a silicon / silicon dioxide wafer substrate by wet transfer using the same method as step (1) of Example 1;

[0145] (2) Depositing gold electrodes on the graphene layer using a lift-off process

[0146] SU-8 3050 photoresist is spin-coated on the surface of the graphene layer, and the photoresist is exposed and developed according to the designed electrode pattern to obtain a patterned photoresist and an area exposed from the patterned photoresist. A gold electrode with a thickness of 100 nm is evaporated on the patterned photoresist and the area exposed from the patterned photoresist. The photoresist is then dissolved with acetone to obtain a source electrode and a drain electrode. Wires are connected to the source electrode and the drain electrode to obtain a graphene field-effect transistor.

[0147] (3) Preparation of microfluidic chip

[0148] Prepare a microfluidic chip with a central flow channel according to step (2) of Example 1;

[0149] (4) Assembly of graphene field-effect transistors and microfluidic chips

[0150] The side of the microfluidic chip obtained in step (3) having the central flow channel is covered on the graphene field effect transistor obtained in step (2), so that the central flow channel contacts the graphene layer between the source and the drain, and a metal electrode is inserted into the liquid inlet of the central flow channel to obtain a graphene field effect transistor based on the microfluidic chip.

[0151] Test Example 1

[0152] The graphene in the substrate 1 having the semiconductor material layer 2 (i.e., the graphene layer) formed thereon obtained in step (1) of Example 1, and the graphene in the graphene field-effect transistor of Comparative Example 1, were scanned using a Raman spectrometer. The Raman spectrum detection results obtained are shown in FIG6 . Raman scans of the graphene in Example 1 and Comparative Example 1 were performed on the same area. As can be seen from the ratios of the 2D peak / G peak and the G peak / D peak in FIG6 , the graphene in Example 1 has fewer defects, better quality, and more excellent performance than that in Comparative Example 1.

[0153] Test Example 2

[0154] The field effect transistor based on the microfluidic chip of Example 1 and the graphene field effect transistor based on the microfluidic chip of Comparative Example 1 were subjected to electrical performance tests. The source, drain and gate of the devices were connected using a semiconductor analyzer for electrical performance tests. The transfer characteristic curve (left figure in Figure 7) was obtained by using I ds -V gs Scan mode, test parameters are: source-drain bias voltage Vds =0.1V, gate V gs The sweep range is -0.9V to 0.9V with a step size of 0.01V. The output characteristic curve (right graph in Figure 7) uses I ds -V ds Scan mode, test parameters are: gate voltage V gs The range is -0.5V to 0.5V, with a step size of 0.2V, and the source-drain bias voltage V ds The range is 0V-0.1V.

[0155] Figure 7 shows the electrical performance test results of the field-effect transistor based on the microfluidic chip of Example 1, including the transfer characteristic curve and the output characteristic curve. The Dirac point is an important parameter for identifying the novel coronavirus. As can be seen from Figure 7, the Dirac point in the intrinsic signal of the field-effect transistor based on the microfluidic chip is close to 0V, which is consistent with the linear distribution of the output characteristic curve, indicating that the graphene and the tin-indium alloy are in ohmic contact, which is consistent with the ideal state of the graphene field-effect transistor.

[0156] Figure 8 compares the electrical performance of the microfluidic chip-based field-effect transistor of Example 1 and the graphene field-effect transistor of Comparative Example 1. As can be seen from Figure 8, the electrical performance of Comparative Example 1 is significantly lower than that of Example 1, with poor performance in terms of current level, transconductance, on / off ratio, and carrier mobility. This indicates that the microfluidic chip-based field-effect transistor of Example 1 has superior electrical performance.

[0157] Example 2

[0158] This embodiment provides a biomarker detection method, which uses the field effect transistor based on the microfluidic chip of Example 1 (the width of the central flow channel 301 is 50 μm) to detect nucleic acids.

[0159] The novel coronavirus sample used in this example contains a complementary strand, a single-stranded RNA that can pair with the DNA probe. The healthy sample contains a non-complementary strand, a single-stranded RNA that cannot fully pair with the DNA probe. Its nucleotide sequence differs from the complementary strand by only one base, resulting in a very high degree of similarity.

[0160] DNA probe nucleotide sequence: 5'-H2N-C6-GCAGATTTCTTAGTGACAGTTTGGCCTTG-3'. Complementary strand nucleotide sequence: 5'-CAAGGCCAAACUGUCACUAAGAAAUCUGC-3'. Non-complementary strand nucleotide sequence: 5'-CAAGGCCAAACUGUCACUAAGGAAUCUGC-3'.

[0161] The biomarker detection method of this embodiment includes the following steps:

[0162] (1) A 5 mM 1-pyrenebutanoic acid succinimidyl ester (PBSE) solution was injected through the liquid inlet 307 of the central flow channel 301 of the field effect transistor based on the microfluidic chip. The solvent in the solution was methanol. The injection time was 1 h and the flow rate was 0.05 μL / min. The flow rate can be controlled by a syringe pump. After completion, a 1× PBS solution was injected for flushing at a flow rate of 10 μL / min.

[0163] (2) Inject a 1 μM DNA probe solution containing 1× PBS solution for 2 h at a flow rate of 0.05 μL / min. After completion, rinse with 1× PBS solution at a flow rate of 10 μL / min.

[0164] (3) Different concentrations of novel coronavirus sample solutions were injected respectively, the solvent in the solution was 1×PBS solution, the concentrations were 10fM, 1pM, 100pM, 10nM and 1μM, and the injection time was 15min; similarly, in the control group experiment, after step (2), different concentrations of healthy sample solutions were injected respectively, the concentrations were 10fM, 1pM, 100pM, 10nM and 1μM, and the injection time was 15min.

[0165] After each injection of the functionalized modifier solution and the sample solution, the electrical signal of the field effect transistor based on the microfluidic chip was tested. The test steps included: using a semiconductor analyzer to connect the source, drain and gate of the device, setting the test mode to I ds -V gs , test the transfer characteristic curve of the device, the test parameters are: source-drain bias voltage V ds =0.1V, gate V gs The scanning range was from -0.3 V to 0.3 V with a step size of 0.01 V. The obtained data were exported and analyzed using software.

[0166] FIG9 is a specificity detection graph (FIG. 9(a) and (b)) and a sensitivity detection graph (FIG. 9(c)) obtained by testing in this embodiment. The concentrations of the novel coronavirus sample solution and the healthy sample solution in FIG9(a) and (b) are both 1 μM. As can be seen from FIG9(a) and (b), the Dirac point of the complementary chain shifts toward the negative gate voltage relative to the signal of the non-complementary chain, indicating that compared with the non-complementary chain, the complementary chain performs n-type doping on the graphene, and the non-complementary chain is not captured by the DNA probe, and the device can successfully distinguish between the novel coronavirus sample and the healthy sample. At the same time, as can be seen from FIG9(c), as the concentration of the complementary chain increases, the Dirac point shifts significantly toward the negative gate voltage, indicating that the combination of the DNA probe and the complementary chain produces n-type doping on the graphene, and its detection limit is as low as 10 fM, and it can effectively distinguish between the complementary chain and the non-complementary chain with a single base mutation. The non-complementary chain with a single base mutation is a nucleotide sequence that differs from the complementary chain by only one base pair, and its similarity to the complementary chain is extremely high. The field-effect transistor based on the microfluidic chip provided in the embodiment of the present invention can successfully distinguish between the complementary chain and the non-complementary chain with only one base difference, indicating its excellent biosensing performance.

Claims

1. A field-effect transistor based on a microfluidic chip, comprising: substrate, semiconductor material layer and microfluidic chip; The semiconductor material layer is provided on the substrate; The microfluidic chip is covered on the semiconductor material layer; The microfluidic chip is provided with a central flow channel and a plurality of electrode channels; Each pair of electrode channels includes a first electrode channel and a second electrode channel, the first electrode channel and the second electrode channel are respectively arranged on both sides of the central flow channel; the ends of the first electrode channel and the second electrode channel are respectively provided with a wire socket; the first electrode channel and the second electrode channel are both provided with a low melting point metal layer to form a source electrode and a drain electrode; The electrode channel is in contact with the semiconductor material layer, and a low-melting-point metal layer is provided on a portion of the semiconductor material layer covered by the electrode channel; One end of the central flow channel is a liquid inlet, and the other end is a liquid outlet; a metal electrode is inserted into the liquid inlet of the central flow channel, and the metal electrode serves as a conductive electrode of the gate; The central flow channel is in contact with the semiconductor material layer.

2. The field effect transistor based on the microfluidic chip according to claim 1, wherein: The substrate includes a silicon wafer having an insulating layer.

3. The field effect transistor based on the microfluidic chip according to claim 1, wherein: The semiconductor material layer is a layer formed of semiconductor materials, and the semiconductor material includes one or a combination of graphene, black phosphorus, carbon nanotubes, molybdenum disulfide and organic semiconductor materials.

4. The field effect transistor based on the microfluidic chip according to claim 3, wherein: The semiconductor material is graphene.

5. The field effect transistor based on the microfluidic chip according to claim 1, wherein: The material of the microfluidic chip includes polydimethylsiloxane.

6. The field effect transistor based on the microfluidic chip according to claim 1, wherein: The first electrode channel and the second electrode channel are symmetrically distributed with the central flow channel as a symmetry axis.

7. The field effect transistor based on the microfluidic chip according to claim 1, wherein: The ends of the first electrode channel and the second electrode channel are each further provided with a low-melting-point metal inlet.

8. The field effect transistor based on the microfluidic chip according to claim 1, wherein: The low-melting-point metal layer is a layer formed of a low-melting-point metal.

9. The field effect transistor based on the microfluidic chip according to claim 8, wherein: The low melting point metal includes a tin-indium alloy.

10. The field effect transistor based on a microfluidic chip according to claim 1, wherein: The field effect transistor based on the microfluidic chip further includes: a plurality of wires, one end of each wire is respectively arranged in the wire sockets of the first electrode channel and the second electrode channel, and at least partially located in the low melting point metal layer.

11. The field effect transistor based on a microfluidic chip according to claim 1, wherein: The area where the semiconductor material layer contacts the central flow channel is covered with ionic liquid, and the ionic liquid contacts the metal electrode; the metal electrode and the ionic liquid form an ionic liquid gate.

12. The field effect transistor based on a microfluidic chip according to claim 1, wherein: The field effect transistor based on the microfluidic chip further includes a clamp, which is used to fix and clamp the substrate and the microfluidic chip.

13. A method for preparing a field effect transistor based on a microfluidic chip according to any one of claims 1 to 12, comprising the following steps: (1) forming a semiconductor material layer on a substrate; (2) preparing a microfluidic chip having a central flow channel and a plurality of electrode channels; (3) assembling the substrate with the semiconductor material layer obtained in step (1) and the microfluidic chip obtained in step (2); (4) forming a low melting point metal layer in the electrode channel and in the portion of the semiconductor material layer covered by the electrode channel to obtain a source electrode and a drain electrode; (5) Inserting a metal electrode into the liquid inlet of the central flow channel to form a conductive electrode of the gate, thereby obtaining the field effect transistor based on the microfluidic chip.

14. The preparation method according to claim 13, wherein Step (2) specifically includes: preparing a positive mold of the microfluidic chip by micro-nano processing technology; and then using the positive mold to prepare the microfluidic chip by a reverse molding method using polydimethylsiloxane.

15. The preparation method according to claim 13, wherein Step (3) specifically includes: covering the microfluidic chip obtained in step (2) on the substrate formed with the semiconductor material layer obtained in step (1), and then fixing and clamping them with a clamp.

16. The preparation method according to claim 13, wherein The preparation method further comprises, before forming the low-melting-point metal layer in step (4), inserting one end of a plurality of wires into the wire sockets of the first electrode channel and the second electrode channel respectively.

17. The preparation method according to claim 16, wherein Step (4) specifically includes: inserting one end of a plurality of wires into the wire sockets of the first electrode channel and the second electrode channel respectively; passing the low-melting-point metal into the electrode channel through the low-melting-point metal inlet provided at the end of the first electrode channel and the second electrode channel, the liquid low-melting-point metal flows in the electrode channel and contacts the portion of the semiconductor material layer covered by the electrode channel, and flows to the wire socket to contact the wire, after the liquid low-melting-point metal solidifies into a solid state, a low-melting-point metal layer is formed to obtain a source and a drain, and at least a portion of the wire located in the wire socket is wrapped in the low-melting-point metal layer.

18. The preparation method according to claim 13, wherein Step (5) further includes: introducing ionic liquid into the central flow channel through the liquid inlet of the central flow channel, the ionic liquid covers the area where the semiconductor material layer contacts the central flow channel, and the ionic liquid contacts the metal electrode, and the metal electrode and the ionic liquid form an ionic liquid gate.

19. A method for detecting a biomarker, comprising the following steps: An ionic liquid containing a biomarker is injected through the liquid inlet of the central flow channel of the field effect transistor based on the microfluidic chip according to any one of claims 1 to 12, and the ionic liquid containing the biomarker flows through the semiconductor material layer to detect the biomarker.

20. The biomarker detection method according to claim 19, wherein: The biomarker detection method specifically includes the following steps: injecting a solution containing a functionalized modifier through the liquid inlet of the central flow channel of the field-effect transistor based on the microfluidic chip to functionally modify the semiconductor material layer, and then injecting an ionic liquid containing the biomarker. The functionalized modified semiconductor material layer captures the biomarker, and then detects the biomarker.

21. The biomarker detection method according to claim 19, wherein: The biomarkers include one or a combination of DNA, RNA and protein molecules.

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