Flexible hydrogel sensor for underwater multi-parameter real-time synchronous monitoring

Abstract

The invention belongs to the field of water quality monitoring, and particularly relates to a flexible hydrogel sensor for underwater multi-parameter real-time synchronous monitoring. The sensor comprises a piezoelectric hydrogel composite material, compatible carbon quantum dots and a gold-plated printed circuit FPC. Flow monitoring is achieved through the piezoelectric hydrogel composite material, and dynamic monitoring of water flow is achieved through piezoelectric signals generated by sensor deformation caused by water flow changes. The PH of the water flow is monitored through the carbon quantum dots; furthermore, a metal printed circuit FPC is combined, and the temperature of the water flow is measured through the thermal resistance effect of metal. The flexible hydrogel sensor is small in size, high in measurement precision, low in energy consumption and capable of synchronously monitoring multiple underwater parameters in real time; and the parameter measurement adopts a non-interfering mechanism, so that the crosstalk problem caused by the fact that the same material collects various external data in the prior art is avoided.

Description

Technical Field

[0001] The present invention belongs to the field of water quality monitoring, and particularly relates to a flexible hydrogel sensor for underwater multi-parameter real-time synchronous monitoring. Background Art

[0002] Water resources account for more than 70% of the earth's surface area and are one of the most essential necessities for maintaining life entities. They are indispensable resources in human industrial, agricultural, recreational and other activities. With the acceleration of the social process and the deterioration of the environment, the importance of water quality monitoring for ensuring human health and life safety has become increasingly prominent.

[0003] Traditional water quality monitoring characterizes the collected water samples through chromatography and electrochemical analysis, providing parameters such as conductivity, turbidity, temperature, pH, dissolved oxygen, heavy metal ions, chlorine content, etc. These parameters are important for determining water quality. These methods have accurate results, but limited timeliness, and there is also the problem of sample quality change during storage. In recent years, underwater sensor online monitoring technology has attracted much attention due to its effective and rapid response.

[0004] Currently, underwater online monitoring is mainly achieved by fluorescence sensors, electrochemical sensors and pressure sensors. Existing sensors can achieve real-time monitoring of various parameters such as flow rate, pH, temperature, etc. These underwater discrete sensors can achieve real-time monitoring of a certain parameter, but still have difficulty meeting the requirements of multi-parameter measurement in complex underwater environments. The current underwater multi-parameter integrated detection method is achieved through the structural integration of a single sensor, including arrays or stacks. However, these integrated sensors have limitations such as large physical size, low measurement accuracy, high energy consumption, and face the thorny problem of signal interference between different sensors.

[0005] For example, most of the existing piezoelectric hydrogel water quality monitoring sensors can only measure a single parameter; while multi-parameter monitoring sensors have problems such as large volume and difficult signal decoupling. Summary of the Invention

[0006] Aiming at the above existing problems or deficiencies, in order to solve the problems of large volume, difficult signal decoupling and signal crosstalk between various sensors in existing underwater online monitoring multi-parameter measurement sensors, the present invention provides a flexible hydrogel sensor for underwater multi-parameter real-time synchronous monitoring.

[0007] A flexible hydrogel sensor for underwater multi-parameter real-time synchronous monitoring comprises a piezoelectric hydrogel composite material, carbon quantum dots and a metal printed circuit FPC.

[0008] The piezoelectric hydrogel composite material utilizes its piezoelectric effect. When the water flow causes the surface of the piezoelectric hydrogel composite material to deform, a potential difference is generated, and an instantaneous signal of voltage is output.

[0009] When water flows through the carbon quantum dots, different colors are shown under ultraviolet light irradiation to measure the pH value of the water flow.

[0010] The metal printed circuit FPC uses the thermal resistance effect of the metal to measure the temperature of the water flow.

[0011] Furthermore, the metal printed circuit FPC is also integrated with a module for external wireless near-field communication to output the signals collected by the sensor externally.

[0012] Furthermore, the carbon quantum dots are biocompatible carbon quantum dots.

[0013] Furthermore, the piezoelectric hydrogel composite material is a biocompatible composite material synthesized from 1,4-butanediol, 1,3-propanediol, succinic acid, sebacic acid, 1,4-butanediol and sodium alginate.

[0014] Furthermore, the preparation method of the piezoelectric hydrogel composite material is as follows:

[0015] Step 1: Synthesize a piezoelectric elastomer from 1,4-butanediol, 1,3-propanediol, succinic acid, sebacic acid and 1,4-butanediol according to the molar ratio of 0.05:0.225:0.35:0.15:0.225.

[0016] Mix the above monomers, add 0.01 wt% antioxidant phosphorous acid and 0.04 wt% inhibitor hydroquinone, then carry out mechanical stirring in a nitrogen environment and heat during the stirring process.

[0017] First, heat at 130 °C for 1 hour, then heat at 180 °C for 2 hours, then add catalyst TBT; react at 300 Pa and 220 °C for 8 hours to generate an elastomer.

[0018] Dissolve the generated elastomer in chloroform, filter and collect the precipitate, wash it with ethanol, and then vacuum dry it at 60 °C to obtain the piezoelectric elastomer.

[0019] Step 2: Preparation of the piezoelectric hydrogel composite material:

[0020] Add the piezoelectric elastomer obtained in Step 1, sodium alginate, and 0.05 wt% dicumyl peroxide powder of the piezoelectric elastomer to the internal mixer according to the mass ratio of 1:0.5 - 2; stir at 120 °C for 30 minutes until fully blended.

[0021] Then, hot press at 10 MPa and 130 °C for 10 minutes in a flat vulcanizer to obtain the piezoelectric hydrogel composite material.

[0022] Furthermore, the piezoelectric hydrogel composite material is physically blended with the carbon quantum dots into one body.

[0023] Furthermore, the method of physically blending them into one is as follows: the piezoelectric hydrogel composite material is fully swollen in the carbon quantum dot solution, and then dried completely in an oven at a temperature below 80°C.

[0024] Furthermore, the metal printed circuit FPC is a printed circuit FPC plated with gold or platinum to improve the sensitivity.

[0025] In summary, the present invention measures parameters using three non-interfering mechanisms. The water flow rate is monitored through the piezoelectric hydrogel composite material; the water flow pH is monitored through the carbon quantum dots; and further combined with the metal printed circuit FPC, the water flow temperature is measured; and there is no problem of signal decoupling. The flexible hydrogel sensor of the present invention has the advantages of small size, high measurement accuracy, low energy consumption, and real-time synchronous monitoring of multiple underwater parameters; and it can be prepared from biocompatible materials, is environmentally friendly, and will not affect the organisms in the water area. Description of the Drawings

[0026] Figure 1 It is the structural diagram of the flexible hydrogel sensor in the embodiment;

[0027] Figure 2 It is the flow rate monitoring performance diagram of the flexible hydrogel sensor in the embodiment;

[0028] Figure 3 It is the monitoring color display diagram of the flexible hydrogel sensor in the embodiment when the water flow pH value is between 3 and 8;

[0029] Figure 4 It is the temperature monitoring diagram of the flexible hydrogel sensor in the embodiment in the water area from -30°C to 60°C;

[0030] Figure 5 It is the application scenario diagram of the flexible hydrogel sensor of the present invention. Detailed Embodiment

[0031] The following further describes the present invention in detail with reference to the drawings and embodiments.

[0032] A flexible hydrogel sensor for real-time synchronous monitoring of multiple underwater parameters includes a piezoelectric hydrogel composite material, biocompatible carbon quantum dots, and a gold-plated printed circuit FPC; its structure is as Figure 1 shown.

[0033] In this embodiment, it involves: preparation of piezoelectric elastomer → preparation of piezoelectric hydrogel composite material → preparation of carbon quantum dots by hydrothermal method → sputtering gold plating to prepare temperature sensor → composite preparation of piezoelectric hydrogel sensor → monitoring of water outlet flow rate, pH, and temperature.

[0034] Preparation of piezoelectric elastomer: Synthesized from 1,4-butylene glycol, 1,3-propanediol, succinic acid, sebacic acid, and 1,4-butanediol, it has a large number of carbon-oxygen dipoles and a long flexible backbone. The carbon-oxygen dipoles endow it with excellent piezoelectric properties; the long flexible backbone and crosslinking sites endow it with excellent mechanical properties (low elastic modulus and high elasticity), thus realizing dynamic stress monitoring by monitoring the change of piezoelectric properties.

[0035] Synthesize the piezoelectric elastomer according to the ratio of 0.05 mol of 1,4-butylene glycol; 0.225 mol of 1,3-propanediol; 0.35 mol of succinic acid; 0.15 mol of sebacic acid; 0.225 mol of 1,4-butanediol. Mix these monomers, add antioxidant phosphorous acid and inhibitor hydroquinone, then carry out mechanical stirring under a nitrogen atmosphere and heat during the stirring process. First, heat at 130 °C for 1 hour, then heat at 180 °C for 2 hours, and then add catalyst TBT. React at 300 Pa and 220 °C for 8 hours. Dissolve the generated elastomer in chloroform, filter and collect the precipitate, wash it with ethanol, and then dry it in vacuum at 60 °C to obtain the piezoelectric elastomer.

[0036] Preparation of piezoelectric hydrogel composite:

[0037] 1. Add 60 g of piezoelectric elastomer, 40 g of sodium alginate, and 0.03 g of dicumyl peroxide into a mixer; stir and blend at 120 °C for 30 minutes.

[0038] 2. Then hot press at 10 MPa and 130 °C for 10 minutes in a flat vulcanizer to obtain the piezoelectric hydrogel composite (FPH).

[0039] Preparation of carbon quantum dots by hydrothermal method:

[0040] 1. Add 2.8 g of o-phenylenediamine powder and 2 g of anhydrous oxalic acid powder into 70 ml of deionized water to form a suspension.

[0041] 2. Then stir at a speed of 700 r / min in a magnetic stirrer for 15 minutes, and then ultrasonicate in an ultrasonic stirrer for 30 minutes.

[0042] 3. Add the suspension into a reaction kettle and heat it in an oven at 180 °C for 10 hours.

[0043] 4. After removing the reaction kettle, separate the residue through a syringe with a 0.45 μm water filter, leaving the carbon quantum dot solution.

[0044] Preparation of a temperature sensor by sputtering gold plating: Fix the FPC with an NFC wireless module on an ion sputtering instrument, deposit a gold layer with a current of 9 - 10 mA for 100 seconds, deposit repeatedly 6 times, and the total gold plating time is 10 minutes.

[0045] Composite preparation of a piezoelectric hydrogel sensor: The piezoelectric hydrogel sensor consists of a piezoelectric hydrogel composite material, biocompatible carbon quantum dots, and a gold-plated flexible printed circuit (FPC) with wireless near-field communication function.

[0046] 1. Swell the piezoelectric hydrogel composite material in the carbon quantum dot solution for 30 minutes, and then dry it in an oven at 40 °C for 1 hour.

[0047] 2. Then, heat the FPH in an oven at 60 °C for 15 minutes and fix the FPC board under a roller press.

[0048] 3. Finally, paste a copper foil on the side without the FPC board as an electrode to obtain the piezoelectric hydrogel sensor.

[0049] Outlet water flow, pH, and temperature monitoring:

[0050] 1. Flow monitoring: Place the flexible hydrogel sensor prepared in the example on a glass substrate, fix its four surrounding positions with tape, place a water outlet pipe 1 cm above the sensor, and measure the dynamic response of the sensor under the vertical action of different water flows. As Figure 2 shown in the flow monitoring performance diagram of the flexible hydrogel sensor in the example; we can see that when different water flows out of the outlet, there are obvious changes in the piezoelectric signals of the sensor. As the water flow increases, the deformation of the sensor increases, and its piezoelectric signal increases accordingly, showing obvious dynamic mechanical response performance, and the dynamic monitoring of water flow can be realized.

[0051] This is due to the piezoelectric effect of the piezoelectric elastomer. When the water flow reaches the surface of the sensor, the generated deformation causes the polarization of the internal electric dipoles of the sensor, thereby generating a potential difference between two opposite surfaces and generating an instantaneous signal of the output voltage.

[0052] 2. pH monitoring: When water flows with different pH values reach the surface of the sensor, the sensor shows different emission colors. In this example, ultraviolet light with a wavelength of 365 nm is used for irradiation. Figure 3 is the monitoring color development diagram of the flexible hydrogel sensor in the example when the pH value of the water flow is 3 - 8. From Figure 3 it, we can see that for different pH values, the sensor will show different colors.

[0053] Different pH values mean different amounts of H + , H +It will cause the protonation / deprotonation behavior of the surface groups of carbon quantum dots, thereby changing the overall single and double bonds, and ultimately leading to changes in the overall electron cloud, that is, changes in the energy level structure. Therefore, when water flows with different pH values passes through the surface of the sensor, under the irradiation of 365 nm ultraviolet light, different color-changing situations will be shown, and different emission light intensities can be measured.

[0054] 3. Temperature monitoring: When water flows with different temperatures reaches the surface of the sensor, due to the temperature resistance effect of gold, the resistance of gold will increase with the increase of temperature. Figure 4 It is the temperature monitoring situation diagram of the flexible hydrogel sensor in the water area of -30°C to 60°C in the embodiment; when water flows with different temperatures reaches the surface of the sensor, from Figure 4 it can be seen that the sensor has a wide temperature measurement range of -30°C - 60°C, which can cover the temperature ranges required by most application scenarios. At the same time, the sensor can respond to temperature changes in a timely manner, which indicates that the sensor has a high-precision temperature monitoring function, and the fitting curve of the sensor is a straight line, and its goodness of fit R 2 is greater than 0.99, which shows that the temperature measurement method using the metal thermal resistance effect has high precision.

[0055] As can be seen from the above embodiments, the piezoelectric hydrogel sensor prepared in this embodiment: integrates the functions of flow monitoring, pH value sensing and temperature sensing, and can be used for real-time water quality monitoring; multiple signals are decoupled from each other; the sensor has a high stress sensitivity of more than 500 mv / N, a fast piezoelectric response time of 0.05 ms and a fast piezoelectric recovery time of 0.08 ms; the sensor has a wide pH measurement range of 3 - 8; it has a wide temperature measurement range of -30°C to 60°C. The sensor of the present invention not only has a small volume, low power consumption and can be self-powered, but also has good mechanical properties and biocompatibility, providing a technical basis for the application scenario of multi-parameter water flow measurement; Figure 5 It is the application scenario diagram of the flexible hydrogel sensor of the present invention.

Claims

1. A flexible hydrogel sensor for real-time synchronous monitoring of multiple underwater parameters, characterized in that: It consists of a piezoelectric hydrogel composite material, carbon quantum dots, and a gold-plated printed circuit FPC; For the piezoelectric hydrogel composite material, by utilizing its piezoelectric effect, when water flow causes deformation on the surface of the piezoelectric hydrogel composite material, a potential difference is generated, and an instantaneous signal of voltage is output; When water flow passes through the carbon quantum dots, different colors are shown under ultraviolet light irradiation to measure the pH value of the water flow; For the metal printed circuit FPC, the temperature of the water flow is measured by utilizing the thermal resistance effect of the metal.

2. The flexible hydrogel sensor for underwater multi-parameter real-time synchronous monitoring according to claim 1, wherein: The metal printed circuit FPC is also integrated with a module for external wireless near-field communication to output the signals collected by the sensor externally.

3. The flexible hydrogel sensor for real-time synchronous monitoring of multiple underwater parameters according to claim 1, wherein: The carbon quantum dots are biocompatible carbon quantum dots.

4. The flexible hydrogel sensor for real-time synchronous monitoring of multiple underwater parameters according to claim 1, wherein: The piezoelectric hydrogel composite material is a biocompatible composite material synthesized from 1,4-butanediol, 1,3-propanediol, succinic acid, sebacic acid, 1,4-butanediol, and sodium alginate.

5. The flexible hydrogel sensor for real-time synchronous monitoring of multiple underwater parameters according to claim 1, wherein The preparation method of the piezoelectric hydrogel composite material is as follows: Step 1: Synthesize a piezoelectric elastomer from 1,4-butanediol, 1,3-propanediol, succinic acid, sebacic acid, and 1,4-butanediol according to a molar ratio of 0.05:0.225:0.35:0.15:0.225; Mix the above monomers, add 0.01 wt% of antioxidant phosphorous acid and 0.04 wt% of inhibitor hydroquinone, then conduct mechanical stirring in a nitrogen environment and heat during the stirring process; First, heat at 130 °C for 1 hour, then heat at 180 °C for 2 hours, then add catalyst TBT; react at 300 Pa and 220 °C for 8 hours to generate an elastomer; Dissolve the generated elastomer in chloroform, filter to collect the precipitate, wash with ethanol, and then vacuum dry at 60 °C to obtain the piezoelectric elastomer; Step 2: Preparation of the piezoelectric hydrogel composite material: Add the piezoelectric elastomer obtained in Step 1, sodium alginate, and 0.05 wt% of dicumyl peroxide powder of the piezoelectric elastomer into a mixer according to a mass ratio of 1:0.5 - 2; stir at 120 °C for 30 minutes until fully blended; Then, hot press at 10 MPa and 130 °C for 10 minutes in a flat vulcanizer to obtain the piezoelectric hydrogel composite material.

6. The flexible hydrogel sensor for real-time synchronous monitoring of multiple underwater parameters according to claim 1, wherein: The piezoelectric hydrogel composite material and the carbon quantum dots are physically blended into one body.

7. The flexible hydrogel sensor for real-time synchronous monitoring of multiple underwater parameters according to claim 6, characterized in that The way of physically blending into one body is: fully swell the piezoelectric hydrogel composite material in the carbon quantum dot solution, and then dry it completely in an oven below 80 °C.

8. The flexible hydrogel sensor for real-time synchronous monitoring of multiple underwater parameters according to claim 1, characterized in that: The metal printed circuit FPC adopts a printed circuit FPC plated with gold or platinum to improve the sensitivity.

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