阅读说明：本技术 电极修饰的重金属离子微流控检测芯片及制备方法 (Electrode-modified heavy metal ion microfluidic detection chip and preparation method thereof ) 是由 洪颖 刘佳 高玲 唐晨 张跃 王金陵 安伟 薛鑫 万其露 陈建松 于 2019-11-04 设计创作，主要内容包括：本发明实施例提供了一种电极修饰的重金属离子微流控检测芯片,包括微流控模块和三电极传感器,其中：微流控模块由3D打印一体成型,内部有微通道和传感器插槽；三电极传感器包括由印制于卡片状底板上的三个电极,其中工作电极为经多孔纳米NiMn<Sub>2</Sub>O<Sub>4</Sub>修饰的裸碳电极；将三电极传感器插入与其匹配的传感器插槽组成所述微流控检测芯片。NiMn<Sub>2</Sub>O<Sub>4</Sub>多孔纳米材料修饰的裸碳工作电极阻抗增加不大且保持了良好的可逆性,使用该工作电极的检测芯片对铅和镉具有更好的线性响应,显著提升了对痕量铅和镉的检测灵敏度,检出限低至使用原有裸碳工作电极时的一半,增强微流控检测芯片的检测性能。本发明实施例还提供了所述微流控检测芯片的制备方法。(The embodiment of the invention provides an electrode-modified heavy metal ion microfluidic detection chip, which comprises a microfluidic module and a three-electrode sensor, wherein: the micro-fluidic module is integrally formed by 3D printing, and a micro-channel and a sensor slot are arranged in the micro-fluidic module; the three-electrode sensor comprises three electrodes printed on a card-shaped bottom plate, wherein the working electrode is porous nano NiMn 2 O 4 A modified bare carbon electrode; and inserting the three-electrode sensor into a sensor slot matched with the three-electrode sensor to form the microfluidic detection chip. NiMn 2 O 4 The impedance of the bare carbon working electrode modified by the porous nano material is not greatly increased, good reversibility is kept, a detection chip using the working electrode has better linear response to lead and cadmium, the detection sensitivity to trace lead and cadmium is obviously improved, and the detection limit is increasedThe detection performance of the micro-fluidic detection chip is enhanced by half of the original bare carbon working electrode. The embodiment of the invention also provides a preparation method of the microfluidic detection chip.)

1. The utility model provides an electrode modified heavy metal ion micro-fluidic detection chip, includes micro-fluidic module (1) and three electrode sensor (2), wherein:

the micro-fluidic module (1) comprises a micro-channel (10) inside, and a liquid inlet pipe (12) and a liquid outlet pipe (13) which are communicated with the outside are arranged at two ends of the micro-channel (10); the three-electrode sensor (2) comprises three all-solid-state planar electrodes arranged on a card-shaped bottom plate (20), namely a working electrode (21), an auxiliary electrode (22) and a reference electrode (23), one end of the three-electrode sensor (2) is provided with an interface area (24), and contact pins (240) at the tail ends of leads of the three all-solid-state planar electrodes are arranged in the interface area (24); the microfluidic module (1) is provided with a sensor slot (11) matched with the three-electrode sensor (2) at the bottom of the microchannel (10); after the three-electrode sensor (2) is inserted into the sensor slot (11), the three all-solid-state planar electrodes are communicated with the microchannel (10), and the interface area (24) is left outside the sensor slot (11); the method is characterized in that:

the micro-fluidic module (1) is a transparent flexible device for 3D printing, and the micro-channel (10), the liquid inlet pipe (12), the liquid outlet pipe (13) and the sensor slot (11) in the micro-fluidic module are integrally formed along with the printing of the micro-fluidic module (1); the working electrode (21) is a bare carbon electrode, and the surface of the working electrode is provided with porous nano NiMn₂O₄Modifying; the auxiliary electrode (22) is an Ag electrode; the reference electricityThe electrode (23) is an Ag/AgCl electrode.

2. The microfluidic detection chip according to claim 1, wherein the microchannel (10) is a saddle-shaped thin layer, and the liquid inlet tube (12) and the liquid outlet tube (13) are respectively connected to two saddle-shaped ends of the microchannel (10) and extend in a direction tangential to the ends.

3. The microfluidic detection chip according to claim 1, wherein the liquid inlet tube (12) and the liquid outlet tube (13) have a liquid inlet nozzle (121) and a liquid outlet nozzle (131) protruding from the surface of the microfluidic module (1), respectively.

4. The microfluidic detection chip according to any one of claims 1 to 3, wherein the interface region (24) and the contact pins (240) are arranged according to USB specification, so that the interface region (24) can be directly inserted into the USB interface (3), and the contact pins (240) can correspondingly communicate with the pins of the USB interface (3).

5. The preparation method of the electrode-modified heavy metal ion microfluidic detection chip of claim 1, which is characterized by comprising the following steps of:

manufacturing a microfluidic module: the method comprises the following steps of manufacturing a microfluidic module by adopting a 3D printing polymer jet process, wherein a microchannel, a liquid inlet pipe, a liquid outlet pipe and a sensor slot in the microfluidic module are integrally formed along with the microfluidic module by printing, and a printing material is Vero Clear photosensitive resin;

manufacturing a three-electrode sensor: manufacturing a three-electrode sensor matched with the microfluidic module by adopting a screen printing mode, taking an insulating card as a bottom plate, and printing three electrodes on the bottom plate in a layered mode, wherein the three electrodes comprise a working electrode, an auxiliary electrode and a reference electrode, and the tail ends of lead wires of the three electrodes are arranged at one end of the bottom plate to form an interface area; reused porous nano NiMn₂O₄Modifying the surface of the working electrode;

assembling a microfluidic detection chip: and inserting one end of the non-interface area of the three-electrode sensor into the sensor slot to enable the three electrodes to be communicated with the micro-channel, sealing the three-electrode sensor with the sensor slot, and leaving the interface area outside the sensor slot for external connection, namely assembling the micro-fluidic module and the three-electrode sensor into the micro-fluidic detection chip.

6. The manufacturing method of claim 5, wherein in the step of manufacturing the three-electrode sensor, the bottom plate is made of flexible PVC material, and the step of printing the three electrodes in layers comprises the following steps:

printing the bottom Ag layer of the three electrodes and the leads on the bottom plate;

printing an Ag/AgCl layer on the Ag layer of the reference electrode;

printing carbon layers on the lead wires of the three electrodes and the Ag layer of the working electrode;

and printing covering insulating ink on other areas of the bottom plate except the three electrodes and the lead areas.

7. The method for preparing the sensor of claim 5, wherein in the step of preparing the three-electrode sensor, the porous nano NiMn is used₂O₄The step of modifying the surface of the working electrode comprises:

preparation of porous Nano NiMn₂O₄；

Modifying the working electrode, i.e. using Nafion to mix porous nano NiMn₂O₄Is immobilized on the surface of the working electrode to modify the working electrode.

8. The method for preparing porous NiMn, according to claim 7, wherein the porous NiMn is prepared₂O₄Comprises the following steps:

mixing MnCl₂•6H₂O 20mmol/L，NiCl₂•6H₂O 40mmol/L，Mn(NH₂)₂120mmol/L and NH₄Dissolving 0.1g of F in 5mL of ethanol and 30mL of deionized water, and violently stirring for 30 min; after the solution is naturally cooled to room temperature, washing the reaction product with distilled water for at least 5 times, and then drying; will reactThe product is annealed in air in a tubular furnace at 2 ℃/min and kept at 350 ℃ for 3 hours to prepare the porous nano NiMn₂O₄And (3) powder.

9. The method of claim 7, wherein the step of modifying the working electrode comprises:

porous nano NiMn₂O₄Adding the powder into a methanol solution, and performing ultrasonic treatment to uniformly disperse the powder;

transferring 5 mu L of solution to be dripped on the surface of the carbon layer of the working electrode, and airing at room temperature;

transferring 5 mul of Nafion solution with the mass percent of 0.5 percent to be coated on the dropping coated porous nano NiMn₂O₄Drying the surface of the working electrode for 3 hours at room temperature to obtain the porous nano NiMn₂O₄A modified working electrode.

Technical Field

The invention belongs to the technical field of electrochemical detection, and particularly relates to an electrode-modified heavy metal ion microfluidic detection chip. The invention also provides a preparation method of the microfluidic chip.

Background

With the development of internet industrialization and industrial intelligence, the number of electronic and electrical products is explosively increased, and people face increasing threats to living environment caused by a large amount of electronic garbage while enjoying brand new life styles brought by modern scientific technologies and electronic commerce. Heavy metal is one of the most main pollution components in electronic waste, and the wide presence is in the electron electrical product, if raw materials, product or discarded object can not obtain good management and control, heavy metal can directly get into soil, water and atmosphere, causes direct pollution, also can cause indirect pollution through mutual migration between different environment. Heavy metals are undegradable, can be finally ingested by a human body through food chain migration and enrichment and accumulated in visceral organs, and the ingested heavy metals are difficult to be discharged out of the body, so that the heavy metals in the human body are easy to be combined with protein, enzyme and the like to cause inactivation, chronic poisoning and other serious pathological changes are caused, and the immeasurable damage is caused to the life health of human beings. Therefore, the control of toxic and harmful pollutants, especially heavy metal ions, in electronic waste is becoming more and more strict in various countries, and higher requirements are also put forward on detection technologies for heavy metal content in various media.

Disclosure of Invention

The invention provides an electrode-modified heavy metal ion microfluidic detection chip and a preparation method thereof, wherein porous nano NiMn is adopted₂O₄The bare carbon working electrode in the all-solid-state planar electrode is modified, so that the sensitivity of the micro-fluidic chip on trace lead and cadmium detection is effectively improved.

In order to solve the above technical problems, an embodiment of the present invention provides an electrode-modified heavy metal ion microfluidic detection chip, including a microfluidic module and a three-electrode sensor, wherein:

the micro-fluidic module comprises a micro-channel inside, and a liquid inlet pipe and a liquid outlet pipe which are communicated with the outside are arranged at two ends of the micro-channel; the three-electrode sensor comprises three all-solid-state planar electrodes arranged on a card-shaped bottom plate, namely a working electrode, an auxiliary electrode and a reference electrode, wherein one end of the three-electrode sensor is an interface area, and the tail ends of leads of the three all-solid-state planar electrodes are arranged in the interface area as contact pins; the microfluidic module is provided with a sensor slot matched with the three-electrode sensor at the bottom of the microchannel; when the three-electrode sensor is inserted into the sensor slot, the three all-solid-state planar electrodes are communicated with the micro-channel, and the three-electrode sensor is assembled with the micro-fluidic module by being inserted into the sensor slot and is in a detachable design; the interface area is left outside the sensor slot, and each electrode of the interface area is connected by an external connector during detectionThe contact pin applies voltage to the electrode and detects the current of the electrode loop; the micro-fluidic module is a transparent flexible device for 3D printing, and the micro-channel, the liquid inlet pipe, the liquid outlet pipe and the sensor slot in the micro-fluidic module are integrally formed along with the printing of the micro-fluidic module; the working electrode is a bare carbon electrode, and porous nano NiMn is coated on the surface of the bare carbon electrode₂O₄Modifying; the auxiliary electrode is an Ag electrode; the reference electrode is an Ag/AgCl electrode.

Preferably, the micro-fluidic module is a saddle-shaped thin layer, and the liquid inlet pipe and the liquid outlet pipe are respectively connected to two saddle-shaped end parts of the micro-channel and extend along a direction tangential to the end parts.

Preferably, the liquid inlet pipe and the liquid outlet pipe are respectively provided with a liquid inlet pipe orifice and a liquid outlet pipe orifice which protrude out of the surface of the microfluidic module, so that the liquid inlet pipe and the liquid outlet pipe are conveniently connected with an external fluid pipeline.

As the optimization of the three-electrode sensor, the interface area and the contact pins are arranged according to the USB specification, so that the interface area can be directly inserted into the USB interface, and the contact pins can be correspondingly communicated with pins of the USB interface; because the standard USB interface is provided with four pins which are arranged in parallel, when the interface area is butted with the USB interface, only three contact pins are needed to be contacted with any three pins in the standard USB interface, and the standard USB interface can be freely selected according to actual requirements.

The embodiment of the invention also provides a preparation method of the electrode-modified heavy metal ion microfluidic detection chip, which comprises the following steps:

1. manufacturing a microfluidic module: the method comprises the following steps of manufacturing a microfluidic module by adopting a 3D printing polymer jet process, wherein a microchannel, a liquid inlet pipe, a liquid outlet pipe and a sensor slot in the microfluidic module are integrally formed along with the microfluidic module by printing, and a printing material is Vero Clear photosensitive resin;

2. manufacturing a three-electrode sensor: manufacturing a three-electrode sensor matched with the microfluidic module by adopting a screen printing mode, taking an insulating card as a bottom plate, and printing three electrodes on the bottom plate in a layered mode, wherein the three electrodes comprise a working electrode, an auxiliary electrode and a reference electrode, and the tail ends of lead wires of the three electrodes are arranged at one end of the bottom plate to form an interface area; reused porous nano NiMn₂O₄Modifying the surface of the working electrode;

3. assembling a microfluidic detection chip: and inserting one end of the non-interface area of the three-electrode sensor into the sensor slot to enable the three electrodes to be communicated with the micro-channel, sealing the three-electrode sensor with the sensor slot, and leaving the interface area outside the sensor slot for external connection, namely assembling the micro-fluidic module and the three-electrode sensor into the micro-fluidic detection chip.

As a preferable option for manufacturing the three-electrode sensor in step 2, the bottom plate is made of flexible PVC material, and the step of printing the three electrodes in layers includes:

2.1. printing the bottom Ag layer of the three electrodes and the leads on the bottom plate;

2.2. printing an Ag/AgCl layer on the Ag layer of the reference electrode;

2.3. printing carbon layers on the lead wires of the three electrodes and the Ag layer of the working electrode;

2.4. and printing covering insulating ink on other areas of the bottom plate except the three electrodes and the lead areas.

As the optimization of the step 2 three-electrode sensor, the porous nano NiMn is used₂O₄The step of modifying the surface of the working electrode comprises:

2.5. preparation of porous Nano NiMn₂O₄；

2.6. Modifying the working electrode: using Nafion to mix porous nanometer NiMn₂O₄Is immobilized on the surface of the working electrode to modify the working electrode.

Preparation of porous Nano NiMn as step 2.5₂O₄Preferably, the method comprises the following specific steps:

2.5.1. mixing MnCl₂•6H₂O 20mmol/L，NiCl₂•6H₂O 40mmol/L，Mn(NH₂)₂120mmol/L and NH₄Dissolving F0.1g in 5mL of ethanol and 30mL of deionized water, and stirring vigorously for 30 min;

2.5.2. after the solution is naturally cooled to room temperature, washing the reaction product with distilled water for at least 5 times, and then drying;

2.5and 3, carrying out air annealing on the reaction product in a tubular furnace at the temperature of 2 ℃/min, and keeping the temperature at 350 ℃ for 3 hours to obtain the porous nano NiMn₂O₄And (3) powder.

As a preference of modifying the working electrode in step 2.6, the specific steps include:

2.6.1. porous nano NiMn₂O₄Adding the powder into a methanol solution, and performing ultrasonic treatment to uniformly disperse the powder;

2.6.2. transferring 5 mu L of solution to be dripped on the surface of the carbon layer of the working electrode, and airing at room temperature;

2.6.3. transferring 5 mul of Nafion solution with the mass percent of 0.5 percent to be coated on the dropping coated porous nano NiMn₂O₄Drying the surface of the working electrode for 3 hours at room temperature to obtain the porous nano NiMn₂O₄A modified working electrode.

The technical scheme is based on the microfluidic technology, the 3D integrally-formed and printed microfluidic control module with the microchannel and the screen-printed all-solid-state planar electrode are matched to form the heavy metal ion microfluidic detection chip for detecting the concentration of heavy metal ions in solution by the ASV method, and the porous nano NiMn is used on the basis of the existing all-solid-state planar electrode bare carbon working electrode₂O₄The modification has the beneficial effects that: on the premise that the impedance of the working electrode is not greatly increased and good reversibility is kept, the detection chip has good linear response to lead and cadmium, the detection sensitivity to trace lead and cadmium is obviously improved, the detection sensitivity can be respectively improved by more than 30 percent and more than 50 percent, the detection limit is reduced to half of that of the original bare carbon working electrode, and the heavy metal ion detection performance of the micro-fluidic detection chip is effectively enhanced.

Drawings

Fig. 1 is a schematic structural diagram of a heavy metal ion microfluidic detection chip provided in an embodiment of the present invention;

fig. 2 is a schematic diagram of an internal structure of a microfluidic module according to an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of a three-electrode sensor according to an embodiment of the present invention;

fig. 4 is a schematic assembly diagram of a three-electrode sensor and a microfluidic module according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of the ASV detection principle;

fig. 6 is a schematic diagram illustrating a matching connection between an interface area of a three-electrode sensor and a USB connector according to an embodiment of the present invention;

fig. 7 is a flowchart illustrating steps of a method for manufacturing a heavy metal ion microfluidic detection chip according to an embodiment of the present invention;

FIG. 8 is a flowchart illustrating steps in the fabrication of a three-electrode sensor according to an embodiment of the present invention;

fig. 9 is a schematic diagram of layered printing of three electrodes by a screen printing process according to an embodiment of the invention.

[ main component symbol description ]

1-a microfluidic module; 10-a microchannel; 11-a sensor socket; 12-a liquid inlet pipe; 121-liquid inlet pipe orifice; 13-a liquid outlet pipe; 131-liquid outlet pipe orifice; 2-a three-electrode sensor; 20-a base plate; 21-a working electrode; 22-an auxiliary electrode; 23-a reference electrode; 24-an interface region; 240-contact pin; 3-USB interface.

Detailed Description

In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.

The invention aims at the technical problem that the detection performance of a microfluidic chip for detecting ASV heavy metal ions in the prior art needs to be further improved, and the embodiment provides an electrode-modified heavy metal ion microfluidic detection chip shown in fig. 1, wherein the microfluidic detection chip comprises a microfluidic module 1 and a three-electrode sensor 2 which are matched with each other and shown in fig. 2-4, and the specific structure is as follows:

as shown in fig. 2, the microfluidic module 1 includes a microchannel 10 therein, and a liquid inlet pipe 12 and a liquid outlet pipe 13 communicated with the outside are disposed at two ends of the microchannel 10; the microfluidic module 1 is provided with a sensor slot 11 matched with the three-electrode sensor 2 at the bottom of the microchannel 10; the micro-fluidic module 1 is a transparent flexible device manufactured by 3D printing, has a transparent detection window, is convenient for monitoring the flow state of liquid in a micro-channel and the reaction condition of the surface of an electrode in the detection process, and is also convenient for the three-electrode sensor 2 and the sensor slot 11 to be tightly matched by virtue of a flexible material; the micro-channel 10, the liquid inlet pipe 12, the liquid outlet pipe 13 and the sensor slot 11 in the micro-fluidic module 1 are integrally formed along with the printing of the micro-fluidic module 1, and the whole micro-fluidic module 1 and the internal structure thereof are seamless and integral, so that the liquid leakage risk caused by splicing of a plurality of parts is avoided.

As shown in fig. 3, the three-electrode sensor 2 includes three all-solid-state planar electrodes, namely, a working electrode 21, an auxiliary electrode 22 and a reference electrode 23, disposed on the card-shaped bottom plate 20, one end of the three-electrode sensor 2 is an interface region 24, and the tail ends of the leads of the three all-solid-state planar electrodes are arranged in the interface region 24 as contact pins 240;

as shown in fig. 4, when the three-electrode sensor 2 is inserted into the sensor slot 11, the three all-solid-state planar electrodes are communicated with the micro-channel 10, and the three-electrode sensor 2 and the micro-fluidic module 1 can form the micro-fluidic detection chip; the three-electrode sensor 2 is detachably designed and can be freely inserted and pulled in the sensor slot 11, and only the three-electrode sensor 2 is required to be tightly fit with the sensor slot 11, so that liquid in the micro-channel 10 cannot leak from a gap between the three-electrode sensor 2 and the sensor slot 11, different sensors can be replaced by inserting and pulling so as to meet the detection requirements of a plurality of samples, and cross contamination among the samples is avoided; the interface area 24 is left outside the sensor slot 11, and during detection, the external connectors are connected with the contact pins 240 of each electrode of the interface area 24, so that voltage can be applied to the electrodes, and the current of an electrode loop can also be detected.

In the three-electrode sensor 2, the working electrode 21 is required to have smaller resistance and larger specific surface, so that the bottom layer is made of Ag with the strongest conductivity, a layer of nano-carbon is covered on the Ag layer to form a bare carbon working electrode, and the surface of the bare carbon working electrode is further made of porous nano-NiMn₂O₄And (5) modifying. After the working electrode is modified, the micro-fluidic detection chip has better linear response to lead and cadmium, and the detection sensitivity to trace lead and cadmium is obviously improved; the auxiliary electrode is required to have small resistance and is formed by an exposed Ag layer; the reference electrode 23 is required to have stable potential, is composed of an Ag layer at the bottom layer and an Ag/AgCl layer covered on the Ag layer, and controls the potential by the Ag/AgCl layer; the surface of the three-electrode sensor 2 is provided with other parts except the exposed part of the insulating layerCovered with a carbon layer.

The heavy metal ion microfluidic detection chip modified by the electrode provided by the embodiment is used for detecting ASV heavy metal ions. The ASV is a very suitable electrochemical analysis method for detecting trace heavy metals from the working process, the detection steps are divided into two processes of reduction pre-electrolysis enrichment and reverse oxidation electrolysis stripping, as shown in FIG. 5, a volt-ampere characteristic curve of the ASV heavy metal ion detection process is shown in a vertical axis of the curve, an applied voltage E is shown in a vertical axis of the curve, and a measured current i is shown in a horizontal axis of the curve; during detection, a constant-value reduction negative voltage is applied to the surface of a working electrode, metal ions with reduction potential higher than the voltage are reduced to metal simple substances on the surface of the working electrode to be enriched, the enrichment amount is in positive correlation with the time for applying the voltage and the concentration of the metal ions, and the current of an electrode loop is measured to obtain an enrichment voltammetry curve in the positive region of a longitudinal axis E in the graph 5; then a positive scanning voltage is applied on the working electrode, the enriched metal simple substance is oxidized into ions again to be dissolved out, the current and the potential are recorded to obtain a dissolution voltammetry curve of a vertical axis E negative area in figure 5, and the peak current of the mu A level or less can be obtained from the dissolution voltammetry curvei _pIf all the operating conditions (electrolyte base solution, electrode, pressurization parameters, etc.) are controlled to be consistent, each metal has a specific oxidation or dissolution peak potential, peak currenti _pThe size of the metal ion is in direct proportion to the concentration of the metal ion in the solution to be detected, and qualitative and quantitative analysis is carried out on the heavy metal in the solution according to the concentration.

The basic flow of the electrode-modified heavy metal ion microfluidic detection chip for detecting specific heavy metal ions in a solution by using an ASV method provided in the above embodiment is as follows:

1. preparing a solution to be detected: adding bismuth ions (Bi) into solution to be detected containing heavy metal ions³⁺) A solution and an acidic base solution;

2. assembling a detection platform: a liquid inlet pipe and a liquid outlet pipe of the microfluidic module are respectively connected with a hose; a peristaltic pump is arranged on a hose connected with the liquid inlet pipe and is communicated with a solution container to be detected; discharging waste liquid through a hose connected with a liquid outlet pipe; correspondingly connecting pins of a working electrode, a reference electrode and an auxiliary electrode of an interface area of the three-electrode sensor with leads of a working electrode WE, a reference electrode RE and an auxiliary electrode AE of an electrochemical workstation respectively;

3. enrichment: applying a negative voltage between the working electrode and the reference electrode by the electrochemical workstation; opening a peristaltic pump, driving a solution to be detected to flow into a micro-channel through a liquid inlet pipe, starting pre-electrolysis under the action of three electrodes, reducing heavy metal ions into metal simple substances, enriching the metal simple substances on the surface of a working electrode, and discharging waste liquid; after the pre-electrolysis is finished, closing the peristaltic pump and standing the solution to be detected;

4. dissolution: applying a forward scanning voltage between the working electrode and the reference electrode by an electrochemical workstation, and oxidizing the heavy metal enriched on the working electrode into heavy metal ions for dissolution;

5. collecting voltammetry data: recording the current and the working electrode potential in the working electrode and counter electrode loop in the stripping process to obtain a stripping voltammetry curve; obtaining the peak current of the solution to be measured through stripping voltammetry curvei _pWill bei _pAnd comparing the peak current with the peak current detected by a standard sample with known concentration under the same condition, and obtaining the concentration of the specific heavy metal ions in the solution to be detected.

According to the working process of the heavy metal ion microfluidic detection chip, the heavy metal ion microfluidic detection chip provided by the embodiment can be optimized for ASV detection, and the method specifically comprises the following steps:

in order to reduce the amount of solution to be measured, the volume of the microchannel as a fluid working area should be as small as possible, and the fluid working area should be designed in a thin layer form, so as to be beneficial to improving the action efficiency of the three electrodes on the solution flowing through, therefore, as a better implementation mode, the microchannel 10 should be processed into a thin layer, the two-dimensional shape of the microchannel 10 can be saddle-shaped, rectangular, circular, oval and other shapes, the rectangular shape and saddle-shaped shape are most commonly used, and theoretical analysis and experiments prove that the saddle-shaped thin-layer microchannel 10 shown in fig. 2 is the best;

the connection positions and the pipe mouth directions of the liquid inlet pipe 12 and the liquid outlet pipe 13 and the microchannel 10 are also selected in various ways, so as to be favorable for the solution to be measured to smoothly flow through the microchannel 10, as shown in fig. 2, when the microchannel 10 is a saddle-shaped thin layer, the liquid inlet pipe 12 and the liquid outlet pipe 13 are respectively connected to two saddle-shaped end parts of the microchannel 10 and extend along the direction tangential to the end parts;

to facilitate the connection of the liquid inlet pipe 12 and the liquid outlet pipe 13 to external fluid pipelines, as shown in fig. 1, the liquid inlet pipe 12 and the liquid outlet pipe 13 are respectively provided with a liquid inlet pipe orifice 121 and a liquid outlet pipe orifice 131 protruding out of the surface of the microfluidic module 1 for connecting fluid pipelines such as hoses.

In order to facilitate the real-time monitoring of the flow state of the liquid in the microchannel and the reaction condition of the electrode surface in the detection process, a transparent material is selected to manufacture the microfluidic module 1;

as a preferred micro-fluidic module, the micro-channel 10 is a saddle-shaped thin layer, and the liquid inlet pipe 12 and the liquid outlet pipe 13 are respectively connected to two saddle-shaped ends of the micro-channel 10 and extend along a direction tangential to the ends.

Preferably, the liquid inlet pipe 12 and the liquid outlet pipe 13 have a liquid inlet pipe orifice 121 and a liquid outlet pipe orifice 131 respectively protruding from the surface of the microfluidic module 1, so as to facilitate connection with an external fluid pipeline.

Preferably, the microfluidic module 1 is made of a transparent material, so that the microfluidic module 1 has a transparent detection window, and real-time observation of working conditions in the detection process is facilitated.

As a preferred choice of the three-electrode sensor 2, the interface area 24 and the contact pins 240 are arranged according to the USB specification, so that the interface area 24 can be directly inserted into the standard USB interface, and the contact pins 240 can be correspondingly communicated with the pins of the standard USB interface; because the standard USB interface has four pins arranged in parallel, when the interface region 24 is in butt joint with the USB interface, only three contact pins 240 need to be sequentially contacted with any three pins of the four pins in the standard USB interface, as shown in fig. 6, the three contact pins 240 respectively correspond to three adjacent pins on the right side of the USB interface 3 one by one, and the design can be freely performed according to actual requirements in actual work.

In order to better realize the technical scheme, the invention also provides a preparation method of the heavy metal ion microfluidic detection chip, the flow of the steps is shown in fig. 7, and the preparation method comprises the following steps:

s1, manufacturing a microfluidic module: the method comprises the following steps of manufacturing a microfluidic module by adopting a 3D printing polymer jet process, wherein a microchannel, a liquid inlet pipe, a liquid outlet pipe and a sensor slot in the microfluidic module are integrally formed along with the microfluidic module by printing, and a printing material is Vero Clear photosensitive resin;

s2, manufacturing the three-electrode sensor: manufacturing a three-electrode sensor matched with the microfluidic module by adopting a screen printing mode, taking an insulating card as a bottom plate, and printing three electrodes on the bottom plate in a layered mode, wherein the three electrodes comprise a working electrode, an auxiliary electrode and a reference electrode, and the tail ends of lead wires of the three electrodes are arranged at one end of the bottom plate to form an interface area; reused porous nano NiMn₂O₄Modifying the surface of the working electrode;

s3, assembling a microfluidic detection chip: and inserting one end of the non-interface area of the three-electrode sensor into the sensor slot to enable the three electrodes to be communicated with the micro-channel, sealing the three-electrode sensor with the sensor slot, and leaving the interface area outside the sensor slot for external connection, namely assembling the micro-fluidic module and the three-electrode sensor into the micro-fluidic detection chip.

In step S1, the microfluidic module 3D printing may be performed by using an Eden260vs type 3D printer, and a polymer jet (PolyJet) process, so that a microfluidic module device with high transparency and certain flexibility can be printed in a high-light gloss printing mode; PolyJet is the leading 3D printing technology at present, the working principle is similar to that of an ink-jet printer, photosensitive polymer micro-droplets are sprayed out of a nozzle array, and a printing layer is obtained by synchronous solidification of an ultraviolet light source arranged on a nozzle; then the working table descends one layer thickness to carry out the next layer of manufacture. The precision of a workpiece formed by the PolyJet is very high, the plane precision can reach 40 mu m, the thickness can reach 16 mu m, a very complex and fine model can be manufactured, and the precision requirement of most of microfluidic chips is met; during specific printing, the material of the microfluidic module body is Vero Clear photosensitive resin, the internal structure position is firstly printed and formed integrally with the microfluidic module body by adopting a supporting material, and then the supporting material is removed, so that the internal structure reserved in the microfluidic module can be obtained; the supporting material is preferably water-soluble FullCure707, and the printed part is removed in a water-soluble supporting and removing solution box after printing.

In step S2, three electrodes are printed on the bottom plate layer by using a screen printing process, so as to obtain an all-solid-state planar three-electrode sensor unit. The bottom plate of the screen printing electrode can be made of flexible materials (such as PVC, PET, PC and the like) or rigid materials (such as glass, ceramics and the like), and as a more implementation mode, the bottom plate made of flexible PVC materials is selected for manufacturing the planar electrode for facilitating batch printing, cutting, storage and carrying of the screen printing electrode, and the flexible material bottom plate can ensure that the electrode can still normally work when the bending curvature radius is smaller

FIG. 8 shows the step S2 of printing three electrodes in layers by screen printing and using NiMn₂O₄An example of the porous nano material for modifying the surface of the working electrode comprises the following specific steps:

s21, printing a bottom Ag layer of the three electrodes and the leads on the bottom plate, wherein the shape of the bottom plate is shown as layer I in figure 9, and the pattern of the Ag layer is shown as layer II in figure 9;

s22, printing an Ag/AgCl layer on the Ag layer of the reference electrode, wherein the pattern of the Ag/AgCl layer is shown as a layer III in the figure 9;

s23, printing a carbon layer on the lead of the three electrodes and the Ag layer of the working electrode, wherein the carbon layer is shown as a layer IV in the graph of FIG. 9;

s24, printing covering insulating ink on other areas of the bottom plate except the three electrodes and the lead areas, wherein the pattern of the insulating layer is shown as a V layer in FIG. 9;

s25 preparation of porous nano NiMn₂O₄The specific steps of one example of step S25 include:

s251, adding MnCl₂•6H₂O 20mmol/L，NiCl₂•6H₂O 40mmol/L，Mn(NH₂)₂120mmol/L and NH₄Dissolving F0.1g in 5mL of ethanol and 30mL of deionized water, and stirring vigorously for 30 min;

s252, after the solution is naturally cooled to the room temperature, washing the reaction product for at least 5 times by using distilled water, and then drying;

s253, carrying out air annealing on the reaction product in a tubular furnace at the temperature of 2 ℃/min, and keeping the temperature at 350 ℃ for 3 hours to obtain the porous nano NiMn₂O₄And (3) powder.

S26 modified working electrode: using Nafion to mix porous nanometer NiMn₂O₄Fixing to the surface of the working electrode to modify the working electrode; the steps of a specific example of the step include:

s261. preparing porous nanometer NiMn₂O₄Adding the powder into a methanol solution, and performing ultrasonic treatment to uniformly disperse the powder;

s262, transferring 5 mu L of solution to be dripped on the surface of the carbon layer of the working electrode, and airing at room temperature;

s263, transferring 5 microliter of Nafion solution with the mass percent of 0.5 percent to be coated on the porous NiMn coated by drops₂O₄Drying the surface of the working electrode for 3 hours at room temperature to obtain the porous nano NiMn₂O₄A modified working electrode.

By porous nano-NiMn₂O₄Modifying a working electrode on the three-electrode sensor, and observing the performance difference between the modified working electrode and a bare carbon working electrode in the detection of heavy metal ions in the microfluidic detection chip by replacing the three-electrode sensor in the microfluidic detection chip to find that the porous nano NiMn is subjected to the Nafion treatment₂O₄After the powder is modified on the surface of the planar electrode, the impedance of the working electrode is not greatly increased, good reversibility is maintained, good linear response is realized on trace lead and cadmium, the sensitivity is respectively improved by more than 30 percent and 50 percent, the detection limit is as low as half of that of a bare carbon electrode, and the performance of the microfluidic detection chip is obviously improved.

For the embodiments of the present invention, the common general knowledge of the known specific structures and characteristics in the schemes is not described too much; the embodiments are described in a progressive manner, technical features related to the embodiments can be combined with each other on the premise of not conflicting with each other, and the same and similar parts among the embodiments can be referred to each other.

In the description of the present invention, the terms "upper", "lower", "bottom", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and should not be construed as limiting the present invention.

Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can make modifications and equivalents to the embodiments of the present invention without departing from the spirit and scope of the present invention, which is set forth in the claims of the present application.