CN114054109B

CN114054109B - Blood coagulation detection micro-fluidic chip based on conductive elastomer material

Info

Publication number: CN114054109B
Application number: CN202111316428.3A
Authority: CN
Inventors: 邢晓星; 李恬怡; 蔡瑶; 俞度立
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2021-11-08
Filing date: 2021-11-08
Publication date: 2022-12-27
Anticipated expiration: 2041-11-08
Also published as: CN114054109A

Abstract

The invention discloses a blood coagulation detection microfluidic chip based on a conductive elastomer material, which comprises a single flow channel, a pair of main body electrodes vertical to the direction of the flow channel, a deformable structure connected with the main body electrodes and suspended up and down in the middle of the flow channel, a block-shaped side wall, an insulating channel and a sample inlet and outlet. The piezoresistive effect of the conductive elastic material is utilized to convert the deformation of the material caused by the strain of flowing blood into the change of an electrical signal, so that the blood coagulation process is detected. The preparation proportion of the conductive elastic material is adjusted according to the elastic modulus, the sensitivity coefficient and other mechanical parameters, so that the optimal conductivity and sensitivity are achieved. The invention does not relate to technical means such as fluorescent labeling and the like, has the advantages of low cost, easy use and high sensitivity, and has wide application prospect when being used as blood coagulation detection equipment.

Description

Blood coagulation detection micro-fluidic chip based on conductive elastomer material

Technical Field

The invention belongs to the technical field of microfluidic chips, and particularly relates to a blood coagulation detection microfluidic chip based on a conductive elastomer material.

Background

The blood coagulation detection has important functions on the selection of hemostatic and antithrombotic drugs, and can accurately detect the blood coagulation process in time, thereby having great significance on the diagnosis and treatment of cardiovascular and cerebrovascular diseases, such as cerebral thrombosis, cerebral infarction, myocardial infarction and the like. For example, during surgery, blood coagulation tests are one of the important means for diagnosing potential bleeding causes and predicting the risk of surgical bleeding, and in the post-operative stage, patients are treated with oral anticoagulation according to the blood coagulation test results to control thrombosis or ensure no excessive coagulation.

The existing detection method and medical apparatus (such as thromboelastography) have certain limitations, for example, the moving parts are not easy to miniaturize, the operation is carried out by professional technicians, the problems of processing or sampling errors and the like are easy to occur, the process is complex, and the detection cost is high.

In recent years, due to the characteristics of low cost, high throughput, simple operation and the like of the microfluidic technology, the blood coagulation detection based on the microfluidic chip technology is developed rapidly, and the detection methods commonly used at present are mainly divided into three major types, namely a fluorescence detection method, a mechanical detection method and an electrical detection method. Fluorescence detection is a method in which a coagulant or a fluorescent-labeled substance is added and then the coagulation of blood is directly observed with an analysis instrument such as a microscope. Although this method is intuitive and clear, the detection is not accurate enough; the principle of the detection method based on mechanics is to detect the change of shearing force or platelet contractility force of blood in the coagulation process, and the detection method is accurate but still depends on a fluorescence detection method, so that the operation is complicated and the cost is high; the detection method based on electricity is used for detecting the change of electrical parameters such as resistance, capacitance or dielectric constant of blood in the blood coagulation process, is real-time and sensitive, and also avoids the mechanical action between the blood and a device, but most of the detection based on electricity is static detection and cannot simulate the flowing state of the blood. At present, the research of pressure sensing or flow sensing by using a flexible piezoresistive sensor chip is very advanced, the microfluidic technology combines the excellent performance of piezoresistive deformation detection to open up a new idea for the detection of the blood coagulation process, namely, the method for detecting the blood coagulation process by converting the deformation of a device into the change of an electrical signal by using the characteristics of easy deformation and high sensitivity of a conductive elastomer under stress besides directly detecting the blood coagulation process based on fluorescence, mechanics or electricity is also a method with a very good application prospect, has the characteristics of high precision and low cost, and can simulate the real environment of blood flow in a micro-channel.

Piezoresistive effect refers to the phenomenon of resistivity varying with applied strain. Through the reasonable and feasible micro-fluidic chip structure of design, make the strain structure be in the middle of the blood flow all the time in the experimentation, along with the change of blood state takes place the deformation, make chip resistance also change thereupon to the process of reaction blood coagulation. Because the tiny channel in the microfluidic chip flows through the small-volume blood sample, the uniformity of the sample can be ensured. Meanwhile, the precise micromachining technology provides a precise and controllable environmental condition for the measurement of the blood coagulation process. Compared with the traditional analysis technology, the micro-fluidic chip is utilized, strain is applied to the conductive elastomer through the coagulation process, and then the change of the electrical characteristics is caused, so that the coagulation detection is more sensitive and accurate, and a more convenient and lower-cost method is provided for the measurement of blood coagulation.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention designs the blood coagulation detection microfluidic chip based on the conductive elastomer material, and a three-dimensional electrode structure is formed through a double-layer mold so as to be connected with a deformable structure suspended in a flow channel. The conductive elastomer is a mixture of a polymer and metal or conductive nonmetal micro-nano particles, and the cured mixture with elasticity has the advantages of high sensitivity, quick response and the like, and can convert strain into resistivity change during deformation (bending, stretching and the like). When blood is injected into the microfluidic chip at a certain flow rate, the deformable structure made of the conductive elastomer deforms due to the shearing force of the blood fluid. Along with the blood coagulation process, the deformation of the deformable structure is increased along with the increase of the viscosity of the blood, and the blood coagulation process is monitored by detecting the change of the electrical impedance of the chip.

The purpose of the invention is realized by the following technical scheme:

the blood coagulation detection microfluidic chip based on the conductive elastomer material is characterized by comprising a top layer (1), a middle layer (2) and a bottom layer (3) which are of a three-layer structure from top to bottom. The top layer (1) is in a flow channel (13) structure, and the middle layer (2) is provided with a flow channel, an electrode and a deformable structure.

The lower part of the top layer (1) is concave to form the upper half part of the flow channel (13). Two ends of the top layer (1) in the direction of the flow channel (13) are provided with two holes (5) which are used as the inlet and outlet of the flow channel.

Intermediate level (2) contain run through intermediate level (2) and with runner (13) the upper half of top layer (1) alignment from top to bottom runner (13) the latter half, be located runner (13) midstream both sides a pair of cubic cuboid and parallel placement's main part electrode (6) of latter half runner (13), around the cubic lateral wall (7) of latter half runner (13) upper reaches and low reaches, be located runner (13) both ends of latter half and with access & exit (8) that top layer hole (5) were aimed at. The main body electrode (6) is coplanar and contactless with the block-shaped side wall (7), and a slit structure-insulating channel (11) for insulation is formed in the middle. Two ends of the strip-shaped deformable structure (9) are respectively fixed on the upper part of the main body electrode (6) so as to be suspended in the flow channel (13). The electrode structure of the middle layer (2) is made of conductive elastic material. When blood is introduced into the chip, the deformable structure (9) made of the conductive elastic material deforms due to stress, so that the electrical impedance of the chip is changed, and the chip is connected into the measuring circuit through the main body electrode (6), so that the change of the electrical impedance of the chip in the blood coagulation process is measured.

The deformable structure (9) crosses the flow channel (13) and has the same width as the flow channel (13), and the height of the deformable structure is smaller than that of the main body electrode (6). The two ends of the deformable structure (9) are respectively fixed on the top of the main body electrode (6), and the top of the deformable structure (9) is flush with the top of the main body electrode (6). After the upper half part of the flow channel (13) positioned on the top layer (1) is aligned with the lower half part of the flow channel (13) positioned on the middle layer (2), the deformable structure (9) is positioned in the middle of the depth of the flow channel (13) and does not contact with the top of the flow channel positioned on the top layer (1) and the bottom of the flow channel positioned on the upper surface of the bottom layer (3), so that the deformable structure (9) and the upper part and the lower part respectively form an upper passage (4) and a lower passage (10) allowing a sample to flow through.

Further, the top layer (1) and the bottom layer (3) of the blood coagulation detection microfluidic chip based on the flexible conductive material are made of insulating transparent materials, wherein the material of the top layer (1) is preferably Polydimethylsiloxane (PDMS), and the height is 2-3mm; the bottom layer (3) is preferably glass.

Further, the conductive elastic material comprises but is not limited to a mixture of various polymers with elasticity and metal or conductive non-metal micro-nano particles; polymers include, but are not limited to, silica gel, polydimethylsiloxane, and the like; the metal micro-nano particles comprise but are not limited to nano silver powder, micron silver powder, nano copper powder, micron copper powder, nano carbon powder and the like; preferably a silver-polydimethylsiloxane mixture (Ag-PDMS) with a silver powder mass fraction of less than 85%.

Furthermore, the deformable structure (9) of the blood coagulation detection microfluidic chip based on the conductive elastomer material is suspended in the center of the flow channel and is as wide as the flow channel, and the shape of the deformable structure includes but is not limited to a cuboid, a thin film, a cylinder and the like.

Furthermore, the width of an insulation channel (11) between the main body electrode (6) and the block-shaped side wall (7) of the micro-fluidic chip for detecting blood coagulation based on the conductive elastomer material is 50-100 mu m.

Further, the insulation channel (11) is filled with an insulation material (12).

Further, when the middle layer (2) is made of Ag-PDMS, the complete processing flow of the micro-fluidic chip for detecting blood coagulation comprises die processing, die making, die filling, alignment key combination, substrate bonding and chip packaging, and the specific steps are as follows:

step 1, processing a die: and processing a mask plate according to a pattern designed by the structure of the blood coagulation detection microfluidic chip based on the flexible conductive material.

Step 2, manufacturing a die: respectively processing a single-layer SU-8 structure and a double-layer SU-8 structure by using a photoetching machine and the mask prepared in the step 1 to obtain a mould required by a top PDMS structure and a middle layer structure; the die can be repeatedly used after being processed.

Step 3, filling a top layer mold: mixing and grinding silver powder and PDMS according to a certain proportion, covering the mixed Ag-PDMS on the surface of the manufactured double-layer structure mould, turning the mould downwards, sliding the mould on A4 paper along the direction vertical to the electrode, removing the excess Ag-PDMS mixture on the surface of the mould, enabling the Ag-PDMS filler to be flush with the upper surface of the mould, and heating and curing the Ag-PDMS;

step 4, filling of the middle layer mold: filling a transparent insulating material, preferably PDMS (polydimethylsiloxane), preferably 3-5mm, on the manufactured single-layer structure mold, and heating and curing the mold and then removing the mold;

step 5, aligning and bonding: carrying out plasma bonding on the PDMS in the step 4 and the mold filled with the Ag-PDMS in the step 3, aligning and bonding the two parts by using an optical alignment platform within three minutes, naturally synthesizing the bonded PDMS and the Ag-PDMS into a whole, heating, then taking off the whole structure from the mold, and perforating a flow channel-electrode functional layer to form a flow channel inlet and a flow channel outlet;

step 6, substrate bonding: bonding the alignment key and the chip main body after the alignment key and the cleaned glass together by using a plasma bonding method or a PDMS (polydimethylsiloxane) spin coating method and the like, and filling an insulation channel between the main body electrode and the block-shaped side wall with an insulation material, preferably PDMS after bonding;

step 7, chip packaging: and 6, cutting the chip bonded with the glass in the step 6 from the side surface until the main body electrode is exposed, connecting the electrode with a copper wire through silver colloid, fixing the chip on the customized PCB, and welding the device and the PCB bonding pad together through the copper wire.

Compared with the prior detection technology, the invention has the following beneficial effects:

the invention provides a method for detecting a blood coagulation process by using a conductive elastomer as a deformable structure for the first time, adopts a novel three-dimensional deformable structure suspended in the center of a flow channel, and adopts a corresponding low-cost, quick, simple and convenient micromachining method based on a reverse mold. The chip provided by the invention allows the test process to simulate the blood flow, and simultaneously converts the strain generated by the shearing force applied to the deformable structure in the blood coagulation process into the electrical impedance change, thereby realizing the detection of the blood coagulation process. The detection method combines the sensitive strain of the conductive elastomer with the electrical detection, and has the advantages of high sensitivity of mechanical detection, simple configuration based on the electrical detection, low cost, accurate and sensitive detection, and simple and low-cost chip processing compared with the existing optical deformation detection method based on the fluorescent marker.

Compared with the existing clinical detection equipment, the invention is based on the microfluidic technology, has the advantages of low cost, high flux, miniaturization and the like, improves the convenience of blood coagulation detection to a great extent, and can meet the detection requirements of patients taking anticoagulant drugs and in backward areas of medical equipment.

Compared with a fluorescence detection method and a mechanical detection method based on a microfluidic detection method, the method does not relate to a fluorescence labeling substance, does not need optical detection or image analysis and other equipment, and saves the detection cost; compared with the existing electrical detection method, the invention is dynamic detection, can detect the coagulation condition of blood in a flowing state and simulate the coagulation process of blood in blood vessels, thereby better reducing the coagulation condition of blood in human bodies in different health states.

Drawings

Fig. 1 is a schematic diagram of an overall structure of a blood coagulation detection microfluidic chip based on a conductive elastomer material, which is sequentially provided with a top layer, a middle layer and a bottom layer from left to right.

Fig. 2 is a schematic structural diagram of a blood coagulation detection microfluidic chip based on a conductive elastomer material according to the present invention, which is respectively (a) a top view, (b) a side view, and (c) a front view.

Fig. 3 is a schematic diagram of a state of a microfluidic chip for detecting blood coagulation according to the present invention when a sample is introduced into the microfluidic chip, which is respectively shown as (a) a top view and (b) a side view.

Fig. 4 is a schematic structural diagram of a middle layer mold of the microfluidic chip for blood coagulation detection based on a conductive elastomer material according to the present invention.

Fig. 5 is a schematic structural view of a PDMS top mold of a blood coagulation detection microfluidic chip based on a conductive elastomer material according to the present invention.

Fig. 6 is a schematic process flow diagram of a blood coagulation detection microfluidic chip based on a conductive elastomer material according to the present invention.

Fig. 7 is an overall view of the chip with the chip body and the PCB connected after packaging.

FIG. 8 is a graph showing the current change of glycerol solutions of different viscosities at a flow rate of 1 ml/min.

FIG. 9 is a graph showing the current change at flow rates of 0ml/min, 0.5ml/min, 1ml/min and 2ml/min for a 30cP glycerol solution, respectively.

The reference numbers are as follows: 1. the chip comprises a chip top layer, 2, a chip middle layer, 3, a bottom layer, 4, an upper passage allowing a sample to flow through, 5, a top layer flow channel inlet and outlet, 6, a main body electrode, 7, a block-shaped side wall, 8, a sample inlet and outlet positioned in the middle layer, 9, a deformable structure, 10, a lower passage allowing the sample to flow through, 11, an insulating channel, 12, an insulating material, 13, a sample flow channel, 14, an excitation voltage, 15, a

silicon chip

1, 16, a first layer SU-8 photoresist structure, 17, a second layer SU-8 photoresist structure, 18, a middle layer mold, 19, a top layer mold, 20, a

silicon chip

2, 21, a customized PCB board, 22, an SMA interface, 23, a bonding pad, 24, a copper wire, 25 and silver glue.

Detailed Description

For further explanation of objects, advantages and features of the present invention, the following detailed description is given with reference to the accompanying drawings and examples, but the embodiments of the present invention are not limited to the following examples.

Example 1

The invention provides a blood coagulation detection microfluidic chip based on a conductive elastomer material, the complete structure of which is shown in figure 1 and comprises a chip top layer 1, a middle layer 2 and a bottom layer 3. The height of the chip PDMS top layer 1 is 4mm, and the diameter of an inlet and an outlet 5, used for injecting a sample and collecting waste liquid, of the top layer 1 is 1.2mm.

The top view and the side view of the microfluidic chip for detecting the blood coagulation process are shown in fig. 2, the excitation voltage 14 is connected to two ends of the main body electrode 6, and the change of the electrical impedance when the deformable structure 9 deforms is detected. The height of the upper channel 4 through which the sample is allowed to flow and the height of the lower channel 10 through which the sample is allowed to flow are preferably 30 μm, so as to prevent the deformable structure 9 from being deformed inconspicuously due to clogging or too small flow resistance.

The invention provides a micro-fluidic chip for detecting blood coagulation based on a conductive elastomer material, the structure of the middle layer of the chip is shown in figure 3, two block-shaped side walls 7 are provided with two holes which are used as sample inlets and outlets 8, the diameter of the two holes is 1.2mm, a single sample flow channel 13 connected with the sample inlets and outlets 8 is arranged in the middle, the width of the flow channel is 400 micrometers, and the length of the flow channel is 5000 micrometers.

The main body electrode 6 is located on two sides of the deformable structure 9, and the deformable structure 9 is coplanar with the main body electrode 6 and the block-shaped side wall 7. The main body electrode 6 and the block-shaped side wall 7 are separated by an insulation channel 11, and the insulation material liquid PDMS is sucked into the insulation channel 11 by utilizing the capillary action, so that the insulation material is flush with the heights of the main body electrode 6 and the block-shaped side wall 7, the leakage of a sample from the insulation channel 11 is prevented, and the width of the insulation channel is 100 micrometers.

The height of the deformable structure 9 is half of that of the main body electrode 6 and the blocky side wall 7, the deformable structure is suspended in the center of the flow channel 13, the deformable structure is always in contact with a sample while the sample does not flow through the deformable structure, the deformable structure is sensitively deformed along with the change of the state of the sample, and the height of the deformable structure 9 is 30 micrometers. The upper passage 4 through which the sample is allowed to flow is substantially level with the lower passage 10 through which the sample is allowed to flow.

When the deformable structure 9 is deformed during detection, the plan view and the side view of the microfluidic chip are shown in fig. 4, and when a sample is introduced into the chip at a certain flow rate, the sample deforms the deformable structure 9. Along with the blood coagulation process, the blood viscosity gradually increases, the impact force on the deformable structure 9 also increases, and the deformation of the deformable structure 9 gradually increases along with the blood coagulation process. The deformation of the deformable structure 9 causes the electrical impedance of the chip to change, the deformation is increased, the electrical impedance is increased, and the detection result shows that the current is reduced.

As shown in fig. 6, a flow chart of a process of a microfluidic chip for detecting blood coagulation based on a conductive elastomer material according to an embodiment of the present invention includes die processing, die making, die filling, alignment bonding, substrate bonding, and chip packaging, and is described in detail as follows:

a. processing a die: pattern processing mask plate designed according to blood coagulation detection micro-fluidic chip based on flexible conductive material

b. Manufacturing a mould: spin-coating a first layer of SU-8 photoresist (16) on a silicon wafer 1 (15) and exposing, then spin-coating a second layer of SU-8 photoresist (17) and exposing, wherein the thickness of the photoresist is 30 mu m, and developing the exposed photoresist to obtain a mold of a microfluidic chip middle layer (2), as shown in step 1-3 of FIG. 6; and (3) spinning and coating a layer of SU-8 photoresist (16) on the silicon wafer 2 (20) and exposing, wherein the thickness of the photoresist is 30 mu m, and developing the exposed photoresist to obtain a mold of the top layer (1) of the microfluidic chip, as shown in step 5-6 of FIG. 6.

c. Filling of the mould (18): mixing and grinding 75% of silver powder and PDMS according to a certain proportion, grinding the mixture into paste to obtain Ag-PDMS, coating the Ag-PDMS on the surface of a mould (18), turning the mould to downwards buckle the surface coated with the Ag-PDMS on A4 paper, pressing the mould (18) and dragging the mould on the paper along the flow channel direction, and removing the redundant Ag-PDMS on the surface of the mould (18); heating to cure the Ag-PDMS, as shown in fig. 6, step 4.

d. Filling a mold (19), namely mixing the mixture with a curing agent according to the ratio of 10:1 and the PDMS is poured on the mold (19) and heated to cure the PDMS, as shown in step 7 of fig. 7, and then removed from the mold (19).

e. Aligning and bonding: carrying out plasma bonding on the uncovered PDMS and a mold (18) filled with Ag-PDMS together, aligning and bonding the two parts by using a stereoscope within three minutes, and naturally synthesizing the bonded PDMS and the Ag-PDMS into a whole as shown in step 8 of FIG. 6; after heating, the whole structure is taken off from the mould (18), and holes are punched from the runner-electrode functional layer to form a runner inlet and a runner outlet;

f. substrate bonding: after the preferred glass (3) is cleaned, putting the preferred glass (3) and the surface of the chip with the runner structure after aligning bonding into a plasma cleaning machine upwards, after plasma bonding treatment, putting the chip on the surface of the preferred glass (3) and pressing, and naturally combining the chip main body and the preferred glass (3) into a whole after bonding is finished, as shown in step 9 of fig. 6; then filling an insulation channel (11) between the main body electrode (6) and the block-shaped side wall (7) by using an insulation material, preferably PDMS;

g. packaging the chip: cutting is carried out from the side face of the chip until a main body electrode (6) is exposed, the electrode is connected with a copper wire (24) through silver paste (25), the chip is fixed on a customized PCB (21), and the chip and a PCB pad (23) are welded together through the copper wire (24).

And (3) testing the chip by using glycerol solutions with different concentrations as blood models in different viscosity states in a blood coagulation process, and testing the performance of the chip by performing a constant-concentration variable-flow-rate or constant-flow-rate variable-concentration experiment at a plurality of flow rates. The specific implementation mode comprises the following steps:

step 1, connecting a chip and signal processing equipment:

one end of the chip main body electrode 6 receives the excitation voltage 14 of the output port of the impedance instrument through the SMA interface 22 on the PCB, and the other end is connected with the input port of the impedance instrument through the preamplifier through the SMA interface 22 on the PCB for data receiving and processing.

Step 2, preparing a glycerol solution:

placing a clean plastic measuring cup on a precision electronic scale, adding 19.25g of glycerol into the plastic measuring cup after peeling the precision electronic scale, adding filtered deionized water into the cup until the reading number of the precision electronic scale reaches 50g, uniformly stirring and mixing the glycerol and the deionized water, sucking the mixture into a needle cylinder, and injecting the glycerol solution into a 50ml conical tube through a needle filter to obtain the glycerol solution with the viscosity of 3.5 cP; adding 23.5g of glycerol into a plastic measuring cup, and adding deionized water to 50g to obtain a glycerol solution with the viscosity of 5 cP; adding 32.5g of glycerol into a plastic measuring cup, and adding deionized water to 50g of glycerol to obtain a glycerol solution with the viscosity of 15 cP; to a plastic measuring cup was added 36.5g of glycerol and then deionized water to 50g to give a glycerol solution with a viscosity of 30 cP.

Step 3, configuring a fluid driving device:

the glycerol solution is sucked into a needle cylinder, the needle cylinder is placed on an injection pump, an injection port of the needle cylinder is connected with a soft rubber tube, the other end of the soft rubber tube provided with an injection head is aligned to a top layer sample injection port 5 and inserted, a waste liquid collecting port is connected with a waste liquid collecting tube through the soft rubber tube provided with the injection head, and the injection flow rate is set on a control interface of the injection pump.

Step 4, signal acquisition:

setting the excitation voltage of the impedance meter to 200mV, starting an excitation switch of the impedance meter to collect data, starting the injection pump after 10 seconds, recording detection data when the solution is not introduced and the solution is introduced, closing the injection pump after 20 seconds of continuous injection, and stopping collecting data after 40 seconds.

And 5, data processing:

and importing the recorded detection data into excel software, calculating a current module value by using a data analysis function of the excel software, generating a scatter diagram of the current changing along with time, and observing the trend of the current change through the scatter diagram.

Respectively injecting 3.5cP, 5cP, 15cP and 30cP of glycerol solution at the same flow rate, such as 1ml/min, and carrying out signal acquisition and data processing; solutions of the same viscosity, such as 30cP glycerol solution, were tested at different flow rates and signal acquisition and data processing were performed.

The test results were as follows:

as shown in fig. 8, when the injection pump is turned on to inject the sample into the chip, the current curve starts to decrease, which is because the sample exerts a force on the deformable structure, which causes the deformable structure to deform, so that the electrical impedance of the chip increases, and the current decreases from the detection result; when the electrode reaches the maximum deformation under the flow velocity, the electrical impedance keeps stable, and the current curve also presents a straight state; when the injection pump is closed, the deformable structure rebounds gradually, the electrical impedance is reduced, and the current curve rises along with the rebound. For the experiment at the same flow velocity, when the viscosity of the sample is higher, the action of force on the deformable structure is higher, the deformation of the deformable structure is higher, so that the electrical impedance change is higher, the amplitude of the current reduction is correspondingly increased, and the slope of the descending section of the current change curve is increased along with the increase of the viscosity of the sample.

As shown in fig. 9, for glycerol solution with the same viscosity, the deformable structure does not deform and the electrical impedance does not change when no sample is injected, so that the current curve is stable and is straight; when the injection flow rate is increased, the solution at the high flow rate generates larger force on the deformable structure at the same moment, and the electrical impedance of the chip is larger, so that the chip at the higher flow rate at the same moment generates larger electrical impedance, the current value is smaller, and the slope of the descending section is larger.

Claims

1. The blood coagulation detection microfluidic chip based on the conductive elastomer material is characterized by comprising a top-down three-layer structure, a middle layer (2) and a bottom layer (3); the top layer (1) is in a structure of a flow channel (13), and the middle layer (2) is provided with the flow channel, a main body electrode (6) and a deformable structure (9);

the lower part of the top layer (1) is concave to form the upper half part of the flow channel (13); two holes (5) which are used as the inlet and the outlet of the flow channel are arranged at two ends of the top layer (1) along the direction of the flow channel (13);

the middle layer (2) comprises a lower half part of a flow channel (13) which penetrates through the middle layer (2) and is aligned with the upper half part of the flow channel (13) of the top layer (1) up and down, a pair of block-shaped cuboid body electrodes (6) which are positioned on two sides of the middle trip of the lower half part of the flow channel (13) and are placed in parallel, block-shaped side walls (7) which surround the upstream and downstream of the lower half part of the flow channel (13), and an inlet and outlet (8) which are positioned at two ends of the lower half part of the flow channel (13) and are aligned with the holes (5) of the top layer; the main body electrode (6) is coplanar and contactless with the block-shaped side wall (7), and a slit structure-insulating channel (11) for insulation is formed in the middle; two ends of the deformable structure (9) are respectively fixed on the upper part of the main body electrode (6) so as to be suspended in the flow channel (13); the electrode structure of the middle layer (2) is made of conductive elastic material.

2. The microfluidic chip for detecting blood coagulation based on conductive elastomer material of claim 1, wherein when blood is introduced into the microfluidic chip, the electrode structure made of conductive elastomer material is deformed due to stress, the electrical impedance of the microfluidic chip is changed, and the microfluidic chip is connected to a measuring circuit through a main body electrode (6), thereby measuring the change of the electrical impedance of the microfluidic chip in the blood coagulation process.

3. The microfluidic chip for blood coagulation detection based on conductive elastomer material of claim 1, wherein the deformable structure (9) spans the flow channel (13) and is as wide as the flow channel (13) and has a height smaller than the body electrode (6); two ends of the deformable structure (9) are respectively fixed on the top of the main body electrode (6), and the top of the deformable structure (9) is flush with the top of the main body electrode (6); when the upper half part of the flow channel (13) positioned on the top layer (1) and the lower half part of the flow channel (13) positioned on the middle layer (2) are aligned, the deformable structure (9) is positioned in the middle of the depth of the flow channel (13) and does not contact with the top of the flow channel positioned on the top layer (1) and the bottom of the flow channel positioned on the upper surface of the bottom layer (3), and an upper passage (4) and a lower passage (10) allowing a sample to flow through are respectively formed above and below the deformable structure (9).

4. The microfluidic chip for detecting blood coagulation based on conductive elastomer material according to claim 1, wherein the top layer (1) and the bottom layer (3) of the microfluidic chip for detecting blood coagulation based on flexible conductive material are made of insulating transparent material, wherein the material of the top layer (1) is Polydimethylsiloxane (PDMS), and the height is 2-3mm; the bottom layer (3) is glass.

5. The microfluidic chip for detecting blood coagulation according to claim 1, wherein the conductive elastic material comprises a mixture of a polymer with elasticity and metal or conductive non-metal micro-nano particles; the polymer comprises silica gel and polydimethylsiloxane; the metal micro-nano particles comprise nano silver powder, micron silver powder, nano copper powder, micron copper powder and nano carbon powder.

6. The microfluidic chip for blood coagulation detection based on conductive elastomer material of claim 1, wherein the deformable structure (9) of the microfluidic chip for blood coagulation detection based on conductive elastomer material is suspended in the center of the flow channel and has the same width as the flow channel, and the shape of the deformable structure comprises a cuboid, a thin film and a cylinder.

7. The microfluidic chip for blood coagulation detection based on conductive elastomer material according to claim 1, wherein the width of the insulation channel (11) between the main body electrode (6) and the block-shaped side wall (7) is 50-100 μm.

8. The microfluidic chip for blood coagulation detection based on conductive elastomer material according to claim 1, wherein the insulating channel (11) is filled with an insulating material (12).

9. The microfluidic chip for blood coagulation detection based on conductive elastomer material according to claim 1, wherein when the intermediate layer (2) is made of Ag-PDMS, the complete process flow comprises die processing, die making, die filling, alignment key bonding, substrate bonding and chip packaging, and comprises the following steps:

step 1, processing a die: processing a mask plate according to a pattern designed by a structure of a blood coagulation detection microfluidic chip based on a flexible conductive material;

step 2, manufacturing a die: respectively processing a single-layer SU-8 structure and a double-layer SU-8 structure by using a photoetching machine and the mask prepared in the step 1 to obtain a mould required by a top PDMS structure and a middle layer structure; the die can be repeatedly used after being processed;

step 3, filling of a top layer mold: mixing and grinding silver powder and PDMS according to a certain proportion, covering the mixed Ag-PDMS on the surface of the manufactured double-layer structure mould, turning the mould downwards, sliding the mould on A4 paper along the direction vertical to the electrode, removing the excess Ag-PDMS mixture on the surface of the mould, enabling the Ag-PDMS filler to be flush with the upper surface of the mould, and heating and curing the Ag-PDMS;

and 4, filling the middle layer mold: filling transparent insulating material PDMS on the manufactured single-layer structure mould, heating and curing, and then removing;

step 5, aligning and bonding: carrying out plasma bonding on the PDMS obtained in the step 4 and the mold filled with the Ag-PDMS obtained in the step 3, aligning and bonding the two parts by using an optical alignment platform within three minutes, naturally synthesizing the bonded PDMS and the Ag-PDMS into a whole, heating, then taking off the whole structure from the mold, and punching a flow channel-electrode functional layer to form a flow channel inlet and a flow channel outlet;

step 6, substrate bonding: bonding the alignment key and the chip main body after the alignment key and the cleaned glass together by a plasma bonding or PDMS (polydimethylsiloxane) spin coating method, and filling an insulation channel between the main body electrode and the block-shaped side wall with PDMS by using an insulation material after bonding;