CN110006969A - A multi-parameter water environment integrated microsensor based on electrochemical detection technology and its preparation method - Google Patents

Abstract

A kind of multi-parameter water environment integrated microsensor and preparation method thereof based on electrochemical measuring technique, is related to electrochemical sensor technology field.The present invention is the electrochemical sensor device in order to solve to be currently used for water quality detection, and volume is big, clean and maintenance program is complicated, and required reagent is more, the problem of having an impact to test result.A kind of multi-parameter water environment integrated microsensor based on electrochemical measuring technique of the present invention, including substrate, No.1 insulating layer, heater layer, No. two insulating layers, microelectrode floor and the test chamber being cascading from bottom to up.PH sensor and temperature sensor are provided on Electrochemistry Micro-sensors, the temperature value that the pH value measured using PH sensor and temperature sensor are measured can be modified the water quality parameter that other two sensor measures, realize the precise measurement of water quality parameter.

Description

A multi-parameter water environment integrated microsensor based on electrochemical detection technology and its Preparation

technical field

The invention belongs to the technical field of electrochemical sensors, in particular to a water environment electrochemical sensor.

Background technique

Water environment monitoring is the main basis for water quality evaluation and water pollution prevention and control. The water quality of rivers is closely related to national production and people's lives. Therefore, fast and accurate water environment sensors are particularly important.

At present, the methods of measuring water quality parameters mainly include chemical analysis, separation analysis, spectroscopic analysis, electrochemical analysis and the combination of various detection methods. Electrochemical analysis is a quantitative and qualitative analysis method that uses the electrical and electrochemical properties of the substance to be tested to determine its properties. This method is closely related to other disciplines. In the aspect of water quality detection, electrochemical analysis is a recognized sensitive, fast and accurate micro and trace analysis method, and its instrument is simple, low cost and suitable for miniaturization.

In the traditional measurement of the existing electrochemical sensor devices for water quality detection, the measurement solution is mainly placed in the laboratory, and a large electrode measurement device is used to realize the water quality measurement. These devices are not only bulky, but also have complicated cleaning and maintenance procedures, require more reagents, and consume a lot of manpower and material resources. At the same time, due to the complexity of the electrochemical solution system, many parameters such as the pH value and temperature of the solution will affect the test results of other parameters.

SUMMARY OF THE INVENTION

The invention is to solve the problems that the existing electrochemical sensor device for water quality detection has large volume, complicated cleaning and maintenance procedures, and requires many reagents, which will affect the test results. Multi-parameter water environment integrated microsensor and preparation method thereof.

A multi-parameter water environment integrated micro-sensor based on electrochemical detection technology, comprising a substrate, a No. 1 insulating layer, a heater layer, a No. 2 insulating layer, a micro-electrode layer and a test cavity sequentially stacked from bottom to top;

The heater layer includes a heater and two heater pads, the heater is in a square wave structure, and two ends of the heater are respectively welded to the two heater pads;

The microelectrode layer includes a temperature sensing electrode and three microelectrodes. The microelectrodes include a working electrode, a counter electrode and a reference electrode. The working electrode has a circular structure, and the counter electrode and the reference electrode are both semicircular structures and distributed in the working electrode. On both sides of the electrode, the counter electrode and the reference electrode are mirror-symmetrical and the openings are opposite;

The No. 1 insulating layer is rectangular, and the two heater pads are arranged along one side of the No. 1 insulating layer. There are also 11 electrode pads on the No. 1 insulating layer, of which 2 electrode pads are located on the two heater pads. Between the plates, the two ends of the temperature sensing electrodes are welded to the two electrode pads respectively, and the remaining nine electrode pads are arranged in a straight line every three to form an electrode group. The remaining three sides of the insulating layer are arranged, the three micro-electrodes are in one-to-one correspondence with the three electrode groups, and the working electrode, the counter electrode and the reference electrode are respectively electrically connected to the three electrode pads in their corresponding electrode groups;

The test cavity is a cavity structure, and its upper surface is provided with a liquid inlet and a liquid outlet. There are four micro-reaction pools inside the test chamber cavity, and the four micro-reaction cells are located at the temperature sensing electrodes and the three micro-electrodes respectively. Just above, the liquid inlet can inject test liquid into the four micro-reaction cells through the microchannel, and the test liquid can be discharged through the liquid outlet.

The above-mentioned substrate is a silicon wafer, and the size of the silicon wafer is 20mm*20mm*1mm.

The above-mentioned No. 1 insulating layer and No. 2 insulating layer are both silicon dioxide insulating layers.

The above-mentioned heaters and heater pads are both Pt films.

The above three microelectrodes are respectively a pH sensing electrode, an ammonium ion concentration sensing electrode, and a heavy metal ion concentration sensing electrode.

The working electrode surface of the ammonium ion concentration sensing electrode is covered with a polyaniline sensitive film, and the working electrode surface of the heavy metal ion concentration sensing electrode is covered with a nano-gold particle film.

The above working electrode is an Au film or a Pt film, the counter electrode is a Pt film, and the reference electrode is an Ag or AgCl film.

The above test cavity is made of PMMA material.

The above-mentioned preparation method of a multi-parameter water environment integrated micro-sensor based on electrochemical detection technology, the method comprises the following steps:

Step 1: grow No. 1 insulating layer on the substrate,

Step 2: Define the shapes of heaters, heater pads and electrode pads by using the positive photolithography method. After sputtering metal, carry out positive glue stripping to form heaters, heater pads and electrode pads.

Step 3: Prepare No. 2 insulating layer on the heater,

Step 4: Define the shape of the temperature sensing electrode and the microelectrode by using the positive photolithography method, and then carry out the positive adhesive stripping after metal sputtering to form the temperature sensing electrode and the microelectrode,

Step 5: prepare a test cavity, and then seal the test cavity on the temperature sensing electrode and the microelectrode by using the fumigation bonding method to complete the preparation of the multi-parameter water environment integrated microsensor.

The specific method for preparing the test cavity above is as follows:

The liquid inlet, the liquid outlet, the micro-reaction pool and the micro-channel were processed on the PMMA substrate by a micro-precision engraving machine.

Since most parameters in the water environment are affected by pH value and temperature, the present invention sets a pH sensor and a temperature sensor on the electrochemical micro-sensor, and the pH value measured by the pH sensor and the temperature value measured by the temperature sensor can be used for The water quality parameters measured by the other two sensors are corrected to achieve accurate measurement of water quality parameters; there is a Pt membrane heater in the middle, which is used in conjunction with the temperature sensor, which is convenient for real-time control, provides suitable working temperature for each sensor unit, and improves the detection of the sensor. Accuracy: Using MEMS technology, multiple micro-electrode measurement units are integrated on the same sensor (such as pH value, temperature, etc.), which can achieve accurate measurement of water quality parameters, and the entire sensor is small in size and requires less samples.

Description of drawings

Fig. 1 is the discrete schematic diagram of the multi-parameter water environment integrated micro-sensor according to the present invention;

Figure 2 is a top view of the heater layer;

Fig. 3 is the top view of No. 2 insulating layer;

4 is a top view of a microelectrode layer;

FIG. 5 is a schematic structural diagram of a microelectrode;

6 is a top view of the multi-parameter water environment integrated micro sensor according to the present invention;

7 is a perspective view of the multi-parameter water environment integrated micro-sensor according to the present invention;

8 is a perspective perspective view of a test chamber;

FIG. 9 is a schematic diagram of the preparation process of the multi-parameter water environment integrated microsensor according to the present invention.

Detailed ways

With the development of MEMS technology, the miniaturization and integration of sensors has become an inevitable trend in the development of water quality parameter detection technology. Microelectrode sensors and microfluidic sensors in the prior art have reduced volume, require less sample, do not need deoxygenation and stirring, and do not need to add supporting electrolytes. Integrating these two sensors together is inevitable for the development of electrochemical sensors. trend. Therefore, the present invention realizes the integration of the two sensors through the following embodiments.

Embodiment 1: This embodiment is described in detail with reference to FIGS. 1 to 8. A multi-parameter water environment integrated micro-sensor based on electrochemical detection technology described in this embodiment includes silicon wafer substrates 1 stacked sequentially from bottom to top. , No. 1 silicon dioxide insulating layer 2 , heater layer, No. 2 silicon dioxide insulating layer 6 , micro-electrode layer and test cavity 9 .

The size of the silicon wafer substrate 1 is 20mm*20mm*1mm.

The heater layer includes a heater 4 and two heater pads 5, the heater 4 is in a square wave structure, and the two ends of the heater 4 are respectively welded with the two heater pads 5; the heater 4 and the heater are welded. The disks 5 are all made of Pt metal material with excellent temperature coefficient of resistance (TCR) linearity.

The microelectrode layer includes a temperature sensing electrode 7 and three microelectrodes 8. The temperature sensing electrode 7 has a "ji"-shaped structure, and the top of the "ji"-shaped structure is recessed downward; the temperature sensing electrode 7 adopts the temperature coefficient of resistance (TCR) Pt metal material with very good linearity realizes the detection of water temperature. The micro-electrode 8 is composed of a three-electrode measurement system. The micro-electrode 8 includes a working electrode 8-1, a counter electrode 8-2 and a reference electrode 8-3. The working electrode 8-1 has a circular structure, and the counter electrode 8-2 has a circular structure. Both the reference electrode 8-3 and the reference electrode 8-3 have a semicircular structure and are distributed on both sides of the working electrode 8-1. The counter electrode 8-2 and the reference electrode 8-3 are mirror-symmetrical and have opposite openings; the working electrode 8-1 is Au film or Pt film, the counter electrode 8-2 is a Pt film, and the reference electrode 8-3 is an Ag or AgCl film.

The above three microelectrodes 8 are respectively a pH sensing electrode, an ammonium ion concentration sensing electrode, and a heavy metal ion concentration sensing electrode, and are respectively used for pH value detection of aqueous solution, ammonium ion concentration detection of aqueous solution, and heavy metal ion detection of aqueous solution. In practical applications, the working electrode surfaces of the ammonium ion concentration sensing electrode and the heavy metal ion concentration sensing electrode are covered with a sensitive film. Specifically, the working electrode surface of the ammonium ion concentration sensing electrode is covered with a polyaniline sensitive film, and the heavy metal ion concentration The surface of the working electrode of the sensing electrode is covered with a nano-gold particle film.

No. 1 silicon dioxide insulating layer 2 is rectangular, two heater pads 5 are arranged along one side of No. 1 silicon dioxide insulating layer 2, and 11 electrode pads are also arranged on No. 1 silicon dioxide insulating layer 2 3. The two electrode pads 3 are located between the two heater pads 5, and are arranged in a straight line with the two heater pads 5. The two ends of the temperature sensing electrode 7 are respectively connected to the above-mentioned two electrode pads. 3 Welding; the remaining 9 electrode pads 3 are arranged in a straight line every three and form an electrode group, and the three electrode groups are respectively arranged along the remaining three sides of the No. 1 silicon dioxide insulating layer 2; three microelectrodes 8 respectively correspond to the three electrode groups one-to-one, and the working electrode 8-1, the counter electrode 8-2 and the reference electrode 8-3 are respectively electrically connected to the three electrode pads 3 in their corresponding electrode groups.

The test cavity 9 is a cavity structure made of PMMA material, and its upper surface is provided with a liquid inlet 9-1 and a liquid outlet 9-2. The inside of the test cavity 9 is provided with four micro-reaction pools 9-3, four micro-reaction The reaction cells 9-3 are located directly above the temperature sensing electrode 7 and the three microelectrodes 8, respectively, as shown in FIGS. 7 and 8 .

The four micro-reaction pools 9-3 are numbered 1, 2, 3, and 4 respectively, and the liquid inlet 9-1 and the three micro-reaction pools 9-3 numbered 1, 2, and 3 pass through the micro-channel 9-4 Connected, the liquid outlet 9-2 is connected with the three micro-reaction pools 9-3 numbered 1, 3, and 4 through the micro-channel 9-4, and the two micro-reaction pools 9-3 numbered 2 and 4 are connected through the micro-channel 9-4. The channels 9-4 communicate with each other, so that the liquid inlet 9-1 can inject the test liquid into the four micro-reaction cells 9-3, and the test liquid can be discharged through the liquid outlet 9-2.

In practical application, the heater pad 5 and the electrode pad 3 are connected to the external circuit to realize the detection of various water quality parameter signals. The heater 4 is used in conjunction with the temperature sensing electrode 7 to measure the water temperature on the one hand, and accurately control the temperature of the measurement environment on the other hand. Using the pH value measured by the pH sensor electrode and the temperature value measured by the temperature sensor electrode 7, the measured values of the ammonium ion concentration sensor electrode and the heavy metal ion concentration sensor electrode can be corrected to achieve accurate measurement of water quality parameters.

The above-mentioned multi-parameter water environment integrated micro-sensor is used to detect the pH value and temperature value of the solution. The specific steps are as follows:

The pH value detection adopts a three-electrode structure, which is composed of a Pt working electrode, a Pt counter electrode, and an Ag/AgCl reference electrode; the detection method adopts the chronopotentiometry, and cooperates with the electrochemical workstation to connect each electrode with the electrochemical workstation correspondingly, and work on Pt A constant current is applied between the electrode and the counter electrode. When the current flows through the Pt electrode, a redox reaction occurs on the surface of the Pt electrode, and the electrode potential changes. The pH value of the solution is measured by measuring the potential difference between the Pt electrode and the reference electrode. Fits the Nernst equation: E is the measurement potential, E ₀ is the standard electrode potential, R is the gas constant (8.314JK ^-1 mol ^-1 ), T is the absolute temperature (K), and F is the Faraday constant (96487.3415Cmol ^-1 ).

It can be known from the Nernst equation that the accurate measurement of pH value is related to temperature T. The temperature sensor is made of Pt metal material with very good linearity of temperature coefficient of resistance (TCR) to realize temperature measurement of water environment. Heater for precise temperature control.

The above-mentioned multi-parameter water environment integrated microsensor is used to detect the ammonium ion concentration of the solution, and the specific steps are as follows:

Firstly, the electrodes were cleaned routinely, heated and air-dried, then the Pt sheet working electrode, Pt sheet counter electrode and Ag/AgCl reference electrode were connected to the electrochemical workstation correspondingly, and then cyclic voltammetry was used to deposit ammonium on the surface of the Pt sheet working electrode. Ion-selective membrane (polyaniline), the electrolyte is a prepared ammonium ion-selective solution, the voltage range is set to 0 to 0.45V, the scan rate is 50mV/s, the number of scan cycles is 20, and the electrode is placed in a desiccator Stroke-dried to prepare ammonium ion-selective thin films.

After the ammonium ion selective electrode is prepared, it can be used for the detection of the ammonium ion concentration in the aqueous solution. The detection method is the ion-sensitive potential measurement method, which is composed of a working electrode and a reference electrode. Among them, the working electrode is an ion-selective electrode modified with an ammonium ion-sensitive membrane, and the reference electrode is an Ag/AgCl electrode. The electrode potential of the reference electrode remains stable, and the open-circuit voltage of the ammonium ion-selective electrode can reflect the concentration of ammonium ions in the solution. The size of the open circuit voltage conforms to the Nernst equation, so the measurement result is related to the pH value of the solution and the temperature value of the solution. The pH value and temperature value measured in Example 2 can be used to correct the ammonium ion concentration value.

The above experiments can prove that the multi-parameter water environment electrochemical micro-sensor described in this embodiment can realize the simultaneous measurement of various water quality parameters, and the measured pH value and temperature value can be corrected for other water quality parameters. Surface modification of different sensitive films can further expand the functionality of the sensor.

Embodiment 2: This embodiment is described in detail with reference to FIG. 9 . This embodiment is a method for preparing a multi-parameter water environment integrated microsensor based on electrochemical detection technology described in Embodiment 1. The method includes the following steps:

Step 1: cleaning the silicon wafer substrate 1 and thermally oxidizing the silicon wafer, and growing a No. 1 silicon dioxide insulating layer 2 with a thickness of 10 μm on the silicon wafer substrate 1 .

Step 2: Define the shapes of the heater 4, the heater pad 5 and the electrode pad 3 by using the positive glue photolithography method, then sputter Pt metal with a thickness of 10 μm, and finally carry out positive glue lift-off (Lift-off) to form a heating Heater 4, heater pad 5 and electrode pad 3 to obtain a heater layer.

Step 3: Prepare a No. 2 silicon dioxide insulating layer 6 with a thickness of 10 μm on the upper surface of the heater 4. The No. 2 silicon dioxide insulating layer 6 can cover the area where the heater 4 is located, and then the heater pad 5 and the electrode are The area of pad 3 is vacant.

Step 4: Define the shape of the temperature sensing electrode 7 and the microelectrode 8 by using the positive photolithography method, and then sputter Au or Pt metal with a thickness of 10 μm to make the working electrode 8-1; sputter Pt metal with a thickness of 10 μm, The counter electrode 8-2 was made; Ag metal with a thickness of 10 μm was sputtered to make a reference electrode 8-3; Pt metal with a thickness of 10 μm was sputtered to make a temperature sensing electrode 7, and then the positive adhesive was peeled off respectively;

Using Ag metal as the anode and Pt metal as the cathode, electrolysis was carried out in a saturated potassium chloride solution to deposit a layer of silver chloride on the surface to make a silver-silver chloride reference electrode to obtain a temperature sensing electrode 7 and a micrometer. Electrode 8, forming a microelectrode layer.

In the above steps, since the silicon dioxide insulating layer 6 vacates the areas of the heater pad 5 and the electrode pad 3, the heater pad 5 and the electrode pad 3 can be electrically connected to the electrodes of the micro-electrode layer.

Step 5: Use a micro-precision engraving machine to process the liquid inlet 9-1, the liquid outlet 9-2, the micro-reaction pool 9-3 and the micro-channel 9-4 on the PMMA substrate with a size of 17mm*17mm*2mm, A test chamber 9 is obtained; the liquid inlet 9-1 and the liquid outlet 9-2 are both 2mm in diameter, and penetrate the PMMA substrate up and down. The cross section of the channel 9-4 is a square of 0.5mm*0.5mm;

Then, the test chamber 9 is sealed and covered on the temperature sensing electrode 7 and the microelectrode 8 by the fumigation bonding method, so as to complete the preparation of the multi-parameter water environment integrated microsensor.

Further, when the ammonium ion concentration sensing electrode is prepared, the electrode is firstly cleaned, heated and air-dried, and then an ammonium ion selective film (polyaniline) is deposited on the working surface of the Pt metal sheet by cyclic voltammetry. For the prepared ammonium ion selective solution, the Pt metal sheet is used as the counter electrode, Ag/AgCl is used as the reference electrode, the voltage range is set to 0 to 0.45V, the scan rate is 50mV/s, and the number of scan cycles is 20. Place in a desiccator to air dry.

For the preparation of heavy metal ion concentration sensing electrodes, cyclic voltammetry is often used to detect the concentration of heavy metal ions. Modifying the nanoparticle film on the surface of the working electrode can effectively increase the surface area of the electrode and increase the electrolytic enrichment efficiency. The sensitivity of detection is also improved. Taking the modified nano-gold particle film as an example to illustrate: first, the electrode is routinely cleaned, and the electrode is subjected to a potentiostatic method in 2mmol/L HAuCl ₄ (0.5mol/L H ₂ SO ₄ in the bottom solution) at a voltage of -0.3V. Electrodeposition of nano-gold particles, after 150s deposition, a layer of nano-gold particle film can be deposited on the surface of the working electrode.

Claims (10)

1. a kind of multi-parameter water environment integrated microsensor based on electrochemical measuring technique, which is characterized in that including from down toward On the substrate (1), No.1 insulating layer (2), heater layer, No. two insulating layers (6), microelectrode floor and the test chamber that are cascading (9)；

Heater layer includes heater (4) and two heater pads (5), and the heater (4) is in square wave configuration, heater (4) it is welded respectively with two heater pads (5) at both ends；

Microelectrode layer includes temperature sensing electrode (7) and three microelectrodes (8), and microelectrode (8) includes working electrode (8-1), right Electrode (8-2) and reference electrode (8-3), working electrode (8-1) rounded structure are equal to electrode (8-2) and reference electrode (8-3) Semicircular in shape structure and the two sides for being distributed in working electrode (8-1), to electrode (8-2) and reference electrode (8-3) mirror symmetry and Opening is opposite；

No.1 insulating layer (2) is in rectangle, and two heater pads (5) are arranged along a line of No.1 insulating layer (2), No.1 insulation 11 electrode pads (3) are additionally provided on layer (2), wherein 2 electrode pads (3) are located between two heater pads (5), temperature The both ends of sensing electrode (7) are welded with 2 electrode pads (3) respectively, and remaining 9 electrode pads (3) every three are in one Straight line arranges and constitutes an electrode group, and three electrode groups are arranged along three sides of the residue of No.1 insulating layer (2) respectively, and three micro- Electrode (8) is corresponded with three electrode groups respectively, and working electrode (8-1) distinguishes electrode (8-2) and reference electrode (8-3) Three electrode pads (3) electrical connection in corresponding electrode group；

Test chamber (9) is cavity body structure, and upper surface is provided with inlet (9-1) and liquid outlet (9-2), in test chamber (9) cavity Portion is set there are four micro reaction pool (9-3), and four micro reaction pools (9-3) are located at temperature sensing electrode (7) and three microelectrodes (8) surface, inlet (9-1) can inject test fluid to four micro reaction pools (9-3) by micro- channel, and test fluid can It is discharged by liquid outlet (9-2).

2. a kind of multi-parameter water environment integrated microsensor based on electrochemical measuring technique according to claim 1, It is characterized in that, substrate (1) is silicon wafer, die size 20mm*20mm*1mm.

3. a kind of multi-parameter water environment integrated microsensor based on electrochemical measuring technique according to claim 1, It is characterized in that, No.1 insulating layer (2) and No. two insulating layers (6) are silicon dioxide insulating layer.

4. a kind of multi-parameter water environment integrated microsensor based on electrochemical measuring technique according to claim 1, It is characterized in that, heater (4) and heater pad (5) are Pt film.

5. a kind of multi-parameter water environment integrated microsensor based on electrochemical measuring technique according to claim 1, It is characterized in that, three microelectrodes (8) are respectively PH sensing electrode, ammonium concentration sensing electrode, concentration of heavy metal ion sensing Electrode.

6. a kind of multi-parameter water environment integrated microsensor based on electrochemical measuring technique according to claim 1, It is characterized in that, the working electrode surface of ammonium concentration sensing electrode is covered with polyaniline sensitive membrane, concentration of heavy metal ion sensing The working electrode surface of electrode is covered with nanogold particle film.

7. a kind of multi-parameter water environment integrated microsensor based on electrochemical measuring technique according to claim 1, It is characterized in that, it is Pt film to electrode (8-2) that working electrode (8-1), which is Au film or Pt film, and reference electrode (8-3) is Ag or AgCl Film.

8. a kind of multi-parameter water environment integrated microsensor based on electrochemical measuring technique according to claim 1, It is characterized in that, test chamber (9) is PMMA material.

9. a kind of preparation side of multi-parameter water environment integrated microsensor based on electrochemical measuring technique described in claim 1 Method, which comprises the following steps:

Step 1: growing No.1 insulating layer (2) on substrate (1),

Step 2: defining the shape of heater (4), heater pad (5) and electrode pad (3) using positive photoresist photoetching process, sputtering Positive photoresist removing is carried out after metal, forms heater (4), heater pad (5) and electrode pad (3),

Step 3: preparing No. two insulating layers (6) on heater (4),

Step 4: the shape of temperature sensing electrode (7) and microelectrode (8) is defined using positive photoresist photoetching process, is carried out after splash-proofing sputtering metal Positive photoresist removing, formation temperature sensing electrode (7) and microelectrode (8),

Step 5: preparing test chamber (9), and test chamber (9) is then covered in temperature sensing electrode using stifling bonding method (7) and on microelectrode (8), the preparation of multi-parameter water environment integrated microsensor is completed.

10. preparation method as claimed in claim 9, which is characterized in that prepare test chamber (9) method particularly includes:

Inlet (9-1), liquid outlet (9-2), micro reaction pool (9-3) and micro- are processed on PMMA substrate using micro- accurate engraving machine Channel (9-4).