Liquid leakage monitoring device

Abstract

Disclosed in the present invention is a liquid leakage monitoring device, comprising a piezoelectric-piezoresistive dual-mode sensor, a temperature sensor, an ion concentration sensor, a moisture sensing structure, a support and a detection circuit, wherein the moisture sensing structure comprises a liquid-absorbing swelling material and a liquid-absorbing layer; the surface of the support is an inclined planar surface, which is provided with a first hollow-out and a second hollow-out; the liquid-absorbing swelling material is arranged in the first hollow-out, the piezoelectric-piezoresistive dual-mode sensor is arranged above the first hollow-out, and the liquid-absorbing layer is arranged below the first hollow-out and the second hollow-out; and the detection circuit is configured to calculate a liquid dropping frequency based on a piezoelectric signal from the piezoelectric-piezoresistive dual-mode sensor, and to calculate a liquid leakage amount after compensation by a temperature signal from the temperature sensor and a concentration signal from the ion concentration sensor based on the piezoresistive signal from the piezoelectric-piezoresistive dual-mode sensor. The present invention can accurately detect the liquid dropping frequency and the liquid leakage amount.

Description

Liquid leakage monitoring device Technical Field

[0001] The present invention relates to a monitoring device, in particular to a liquid leakage monitoring device. Background Art

[0002] Undersea tunnels are essential transportation projects that facilitate daily commutes and promote regional economic development. However, serving in harsh environments, undersea tunnels face high water pressure, ocean currents, and marine corrosion, making water seepage a significant safety hazard that cannot be ignored during construction. Water seepage also poses a challenge to the durability of infrastructure such as underground heat exchange stations, subway tunnels, and water supply and drainage pipelines. Water seepage is often accompanied by deformation and cracks in building materials, stemming from construction flaws or external damage from long-term service. Water seepage can further accelerate building degradation, reduce its service life, and, in severe cases, lead to devastating disasters, including landslides and flooding, seriously endangering the safety of both the public and property.

[0003] Currently, in the field of water leakage monitoring and alarm, most pipe network leak detection systems monitor water supply networks using sensors to sense vibration or sound signals of leaks. However, due to the weak vibration signals and significant external interference, the precision instruments of such leak detection systems are relatively expensive. Some systems also use pressure sensors to detect water leaks. This technology combines a material that expands when exposed to water with a pressure sensor. When liquid leaks, the pressure sensor senses pressure changes, thereby monitoring and alarming the liquid leak. For example, CN214063051U discloses a tunnel leakage advance monitoring and early warning device that is easy to install and durable. However, it can only detect small amounts of slow water seepage and cannot quickly respond to high-frequency water leaks. CN114596694A discloses a dual-mode pressure sensing monitoring and alarm device for sensing tunnel water seepage. This dual-mode pressure sensor can simultaneously sense mechanical information in both dynamic and static conditions, enabling detection of small amounts of slow water seepage and rapid response to high-frequency water leaks. However, this technology cannot accurately detect the ultra-low frequency dripping frequency and specific leakage volume at the initial stage of liquid leakage. At the same time, circuit design is used to improve sensing accuracy.

[0004] Summary of the Invention

[0005] Purpose of the invention: In order to solve the problems existing in the prior art, the present invention provides a liquid leakage monitoring device that can detect the ultra-low frequency dripping frequency and specific leakage amount at the initial stage of liquid leakage.

[0006] Technical solution: The liquid leakage monitoring device described in the present invention includes a piezoelectric-voltage-resistive dual-mode sensor, a temperature sensor, an ion concentration sensor, a moisture sensing structure, a bracket and a detection circuit. The moisture sensing structure includes a liquid-absorbing and expanding material and a liquid-absorbing layer. The surface of the bracket is an inclined plane, and a first hollow and a second hollow are provided on the plane. The liquid-absorbing and expanding material is filled in the first hollow. The piezoelectric-voltage-resistive dual-mode sensor is arranged above the first hollow, and the liquid-absorbing layer is arranged below the first hollow and the second hollow. The detection circuit is respectively connected to the piezoelectric-voltage-resistive dual-mode sensor, the temperature sensor, and the ion concentration sensor, and is used to calculate the liquid dripping frequency based on the piezoelectric signal of the piezoelectric-voltage-resistive dual-mode sensor, and calculate the liquid leakage amount after compensation by the temperature signal of the temperature sensor and the concentration signal of the ion concentration sensor based on the piezoresistive signal of the piezoelectric-voltage-resistive dual-mode sensor.

[0007] Furthermore, the detection circuit includes:

[0008] A filtering and amplifying module, connected to the piezoelectric signal output terminal of the piezo-piezoresistive dual-mode sensor, for filtering and amplifying the piezoelectric signal;

[0009] A first AD conversion module, configured to perform analog-to-digital conversion on the signal output by the filtering and amplifying module;

[0010] A voltage stabilization module, used for stabilizing the signal output by the first AD conversion module to obtain a digital piezoelectric signal;

[0011] a resistance-to-voltage conversion module, connected to the piezoresistive signal output terminal of the piezo-piezoresistive dual-mode sensor, for converting the piezoresistive signal in the form of current into a piezoresistive signal in the form of voltage;

[0012] The second AD conversion module is used to perform analog-to-digital conversion on the piezoresistive signal in the form of voltage to obtain a digital piezoresistive signal;

[0013] a microprocessor configured to calculate a liquid dripping frequency based on the digital piezoelectric signal according to a preset first algorithm, and to calculate a liquid leakage amount based on the digital piezoresistive signal, the temperature signal, and the concentration signal according to a preset second algorithm;

[0014] A transmission module, configured to transmit the liquid dripping frequency and the liquid leakage amount;

[0015] Power module, used to provide power to each module.

[0016] Furthermore, the resistance-to-voltage conversion module is specifically a Wheatstone bridge circuit composed of four resistors.

[0017] Furthermore, the first algorithm obtains the liquid dripping frequency by obtaining the interval time between two pulses of the digital piezoelectric signal.

[0018] Furthermore, the second algorithm is specifically a calculation formula obtained by fitting the digital piezoresistive signal, temperature signal, concentration signal and corresponding liquid leakage amount obtained by multiple measurements.

[0019] Furthermore, the piezo-piezoresistive dual-mode sensor includes a piezoresistive sensing layer, a piezoresistive electrode, a first piezoelectric substrate, a piezoelectric film, a piezoelectric electrode, a second piezoelectric substrate, a piezoresistive signal output end and a piezoelectric signal output end. The piezoresistive sensing layer, the piezoresistive electrode, the first piezoelectric substrate, the piezoelectric film, the piezoelectric electrode and the second piezoelectric substrate are stacked in sequence. The piezoresistive signal output end is connected to the piezoresistive electrode, and the piezoelectric signal output end is connected to the piezoelectric electrode.

[0020] Furthermore, the bracket is formed of a high molecular polymer material. The second hollow is located downhill from the first hollow. The piezo-piezoresistive dual-mode sensor and the liquid absorbing layer are fixed to the bracket by adhesive tape.

[0021] Furthermore, the liquid-absorbing and swelling material is a micro-granular superabsorbent resin.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. The device is a relatively low-cost solution for monitoring tunnel water seepage. 2. The present invention fully utilizes the advantages of the dual-mode pressure sensor and designs a dual-path water flow structure based on slope constraints. The piezoelectric part can make a pulse response to the falling water droplets, thereby distinguishing the frequency of water droplet leakage, while the piezoresistive part can use the water-absorbing and swelling characteristics of the water-absorbing material to sense different leakage amounts. The combination of the two can provide rich information for monitoring and analyzing complex water seepage scenarios. 3. The present invention cooperates with a specially designed detection circuit to obtain the ultra-low frequency liquid dripping frequency based on the piezoelectric signal calculation, and also introduces a temperature sensor and the seepage ion concentration to simultaneously process the environmental signal and the piezoresistive signal, taking into account the influence of the environment and liquid ion concentration on the leakage amount, realizing liquid leakage detection with environmental compensation function, and the detected liquid leakage result is more accurate. The present invention can timely detect water seepage diseases in buildings such as submarine tunnels, and help analyze and judge the actual situation of water seepage problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a schematic structural diagram of a liquid leakage monitoring device in a liquid leakage monitoring device provided by the present invention;

[0024] FIG2 is a schematic diagram of a specific circuit of a detection circuit;

[0025] FIG3 shows the piezoresistive response and corresponding characteristics of the piezo-piezoresistive dual-mode sensor of the present invention for different leakage amounts;

[0026] FIG4 shows the piezoresistive response of the piezo-piezoresistive dual-mode sensor of the present invention to different dripping frequencies;

[0027] FIG5 shows the piezoelectric response of the piezo-piezoresistive dual-mode sensor of the present invention to different dripping frequencies;

[0028] Figure 6 shows the comparative structure and its response to different leakage amounts and dripping speeds;

[0029] FIG7 is a comparison of the relative current change curves of the piezo-piezoresistive dual-mode sensor of the present invention for each 0.5 mL drop at different room temperatures;

[0030] FIG8 is a relative current change curve of the piezoelectric-piezoresistive dual-mode sensor of the present invention for each 0.3 mL leakage of seawater;

[0031] FIG9 is a schematic diagram of an ultra-low frequency dripping frequency detection circuit portion of the detection circuit of the present invention;

[0032] FIG10 is a schematic diagram of the environmental compensation water seepage detection circuit portion of the detection circuit of the present invention. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] This embodiment provides a liquid leakage monitoring device, as shown in Figures 1 and 2 , comprising a piezo-piezoresistive dual-mode sensor 1, a moisture sensing structure 2, a bracket 3, a detection circuit, a temperature sensor, and an ion concentration sensor. The moisture sensing structure 2 comprises a liquid-absorbing swelling material 21 and a liquid-absorbing layer 22. The bracket 3 has a tilted surface with a first hollow 31 and a second hollow 32 defined therein. The second hollow 32 is located downhill from the first hollow 31. The liquid-absorbing swelling material 21 is filled in the first hollow 31, the piezoelectric-voltage-resistive dual-mode sensor 1 is arranged above the first hollow 31, and the liquid-absorbing layer 32 is arranged below the first hollow 31 and the second hollow 32. The detection circuit is respectively connected to the piezoelectric-voltage-resistive dual-mode sensor, the temperature sensor, and the ion concentration sensor. The detection circuit and the piezoelectric-voltage-resistive dual-mode sensor, the temperature sensor, and the ion concentration sensor can be integrated on a single board or installed separately. It is specifically used to calculate the liquid dripping frequency based on the piezoelectric signal of the piezoelectric-voltage-resistive dual-mode sensor, and to calculate the liquid leakage amount after compensation by the temperature signal of the temperature sensor and the concentration signal of the ion concentration sensor based on the piezoresistive signal of the piezoelectric-voltage-resistive dual-mode sensor.

[0035] As shown in Figure 1, the piezo-piezoresistive dual-mode sensor 1 includes a piezoresistive sensing layer 11, a piezoresistive electrode 12, a first piezoelectric substrate 13, a piezoelectric film 14, a piezoelectric electrode 15, a second piezoelectric substrate 16, a piezoresistive signal output terminal, and a piezoelectric signal output terminal. The piezoresistive sensing layer 11, the piezoresistive electrode 12, the first piezoelectric substrate 13, the piezoelectric film 14, the piezoelectric electrode 15, and the second piezoelectric substrate 16 are stacked in sequence. The piezoresistive signal output terminal is connected to the piezoresistive electrode, and the piezoelectric signal output terminal is connected to the piezoelectric electrode. The microstructure template used for the piezoresistive sensing layer 11 is commercial sandpaper, but is not limited to this. It can also be a commercial product with a microstructure and low cost, such as nylon mesh or fabric. The piezoresistive conductive material is a carbon nanotube film prepared by spraying or other nanomaterials with excellent conductivity. The piezoresistive electrode 12 is made of nanometer-thick metal particles such as Pt, Au, or Ag sputtered by a vacuum coating machine, and is a planar electrode with two ends separated by a 2 mm gap. The first piezoelectric substrate 13 and the second piezoelectric substrate 16 are specifically PDMS substrates. The piezoelectric film 14 is made of PVDF and / or P(DVF-TrFE) or other materials that can be made into flexible piezoelectric films. The preferred preparation process is spin coating. The film thickness is 5-10 μm. The piezoelectric electrodes 15 are interdigital electrodes of sputtered metal.

[0036] The method for preparing the piezoelectric-piezoresistive dual-mode sensor 1 comprises the following steps:

[0037] (1) PDMS and curing agent were mechanically stirred at a weight ratio of 10:1, allowed to stand to remove bubbles, and then a thin film was spin-coated on commercial sandpaper using a coating machine. After high-temperature curing, a PDMS flexible substrate with a sandpaper surface morphology was obtained, i.e., the first piezoelectric substrate 13. An appropriate amount of carbon nanotube dispersion was sprayed onto the surface of the first piezoelectric substrate 13 of the desired size to obtain a composite MWCNTs / PDMS piezoresistive sensing layer 11.

[0038] (2) P(VDF-TrFE) powder is dissolved in a solvent and spin-coated to form a piezoelectric film 14 with controllable thickness using a coating machine. A 500 μm thick uncured PDMS film is prepared on a glass slide using a doctor blade. The piezoelectric film 14 is placed on it. After curing on an 80°C hot plate for 1 hour, the cut and plated piezoelectric electrodes 15 are carefully removed. A 250 μm thick PDMS layer is then scraped to form a second piezoelectric substrate 16. The piezoelectric film 14 with the second piezoelectric substrate 16 is then reversed and placed on the first piezoelectric substrate 13 of PDMS. After curing, the packaging is completed.

[0039] (3) A layer of discontinuous electrode material, namely the piezoresistive electrode 12, is deposited on the contact surface between the piezoresistive sensing layer 11 and the first piezoelectric substrate 13, and is led out on both sides with wires. The resulting material is then packaged to obtain the piezoresistive and piezoelectric dual-mode pressure sensor 1.

[0040] The liquid-absorbing swelling material 21 is a microscopic, highly absorbent resin with a high water absorption and expansion ratio. The liquid-absorbing layer 22 is specifically a thin absorbent cotton pad. It absorbs water from the second hollow portion, which is then absorbed by the liquid-absorbing swelling material 21. After the liquid-absorbing swelling material 21 expands, it squeezes the piezoresistive and piezoelectric dual-mode pressure sensor 1 to generate a signal. The piezoresistive and piezoelectric dual-mode pressure sensor 1 and the liquid-absorbing layer 22 are secured using standard scotch tape and medical PU film tape, respectively. This allows the sensor and the liquid-absorbing swelling material 21 to be interchanged with the thin absorbent cotton pad, achieving device reuse.

[0041] Bracket 3 is made of a polymer material. In the experiment, bracket 3 was fixed to a container with a sloping bottle mouth as a base. During use, it can be directly fixed to a building at an angle, depending on the layout. Liquid-absorbing swelling material 21 is placed in the first hollow 31. This space will impose a certain limit on the expansion of the water-absorbing material, thereby maximizing the conversion of deformation into a pressure that the piezoresistive and piezoelectric dual-mode pressure sensor 1 can respond to. The surface of bracket 3 is tilted. When a water droplet falls on this slope, the vibration is sensed by the sensitive piezoelectric film 14 of the piezoresistive and piezoelectric dual-mode pressure sensor 1, outputting a voltage signal. The water droplet continues to slide down to the second hollow, where it is absorbed by the liquid-absorbing layer 22, transporting water to the location of the liquid-absorbing swelling material 21. The liquid-absorbing swelling material 21 expands. Due to the positional constraints of the first hollow 31, it effectively applies pressure to the piezoresistive sensing layer 11 of the piezoresistive and piezoelectric dual-mode pressure sensor 1 above, resulting in different piezoresistive responses depending on the pressure conditions.

[0042] As shown in Figure 2, the detection circuit includes a filter amplifier module, a first AD conversion module, a voltage stabilizing module, a resistance voltage conversion module, a second AD conversion module, a microprocessor, a transmission module, and a power supply module. Among them, the filter amplifier module, the first AD conversion module, the voltage stabilizing module, and the microprocessor form the ultra-low frequency dripping frequency detection circuit part (Figure 8), and the environmental compensation module composed of the resistance voltage conversion module, the second AD conversion module, the microprocessor, the temperature sensor, and the ion concentration sensor forms the environmental compensation seepage detection circuit part (Figure 9). The filter amplifier module is connected to the piezoelectric signal output end of the piezoelectric-voltage-resistance dual-mode sensor and is used to filter and amplify the piezoelectric signal. Specifically, it is a low-pass amplification filter circuit composed of an operational amplifier and a capacitor. It can filter out clutter and noise in the input signal and amplify the signal by about 100 times, making the output signal more accurate and stable. The first AD conversion module is used to perform analog-to-digital conversion on the signal output by the filter amplifier module. Specifically, it is a hysteresis comparison circuit that can avoid frequent switching of the output signal due to small fluctuations of the input voltage near the threshold and convert it into a digital pulse signal. The voltage stabilization module is specifically a voltage follower, which is used to stabilize the signal output by the first AD conversion module to obtain a digital piezoelectric signal, which is input to the microprocessor. The resistance-to-voltage conversion module is connected to the piezoresistive signal output terminal of the piezo-piezoresistive dual-mode sensor. It is specifically a Wheatstone bridge circuit composed of four resistors: three standard resistors and one variable resistor. It is used to convert the piezoresistive signal in the form of current into a piezoresistive signal in the form of voltage. The second AD conversion module is an HX711, which is used to perform analog-to-digital conversion on the piezoresistive signal in the form of voltage to obtain a digital piezoresistive signal. The microprocessor is composed of an STM32 minimum circuit and is used to calculate the liquid dripping frequency based on the digital piezoelectric signal according to a preset first algorithm. It is also used to calculate the liquid leakage amount based on the digital piezoresistive signal, temperature signal, and concentration signal according to a preset second algorithm. The transmission module is used to transmit the liquid dripping frequency and liquid leakage amount. It can be a wireless transmission module or a wired transmission module. The preferred method is a wireless transmission module. For wireless transmission, a Bluetooth wireless transceiver can be used to transmit the signal to a mobile terminal for display. The relationship between the leakage value and time can also be recorded and plotted into a graph. The power supply module consists of a transformer, a voltage regulator filter, and a bridge rectifier circuit, which converts 220V AC power into 5V DC power to power each module.

[0043] The first algorithm in the microprocessor obtains the liquid dripping frequency by obtaining the interval time between two pulses of the digital piezoelectric signal. The second algorithm is specifically a calculation formula fitted according to the digital piezoresistive signal, temperature signal, concentration signal and the corresponding liquid leakage obtained by multiple measurements.

[0044] The present invention is experimentally verified below.

[0045] In order to verify the effect of the present invention, a comparative example was set up, specifically: the bracket plane was not tilted and fixed, the upper part of the plane was made of absorbent thin cotton and a porous PU film as a volume limiting structure and water seepage channel, and the lower part was made of a dual-mode pressure sensor.

[0046] As can be seen from Figure 3, the larger the amount of dripping water, the longer it takes to reach the stable plateau period and the greater the intensity of the piezoresistive response, which can basically distinguish the size of the leakage. The position of the heart represents the time when the dripping starts. The delay time to the response is more than ten seconds. This is because it takes time for the water to be absorbed by the liquid-absorbing layer and transported to the vicinity of the liquid-absorbing expansion material and for it to expand to the minimum detection threshold of the device. Figure 4 shows that the device can distinguish the speed of the dripping frequency. The faster the frequency, the faster the liquid-absorbing expansion material expands, the less time it takes, and the faster the response curve reaches the plateau period, but the specific frequency is more difficult to distinguish. Figure 5 shows that the piezoelectric part can distinguish the changes in different dripping frequencies, and as the frequency increases, the voltage response becomes larger, thereby providing additional information to help analyze specific leakage scenarios.

[0047] If the assembly method in the comparative example is adopted, although the piezoresistive part can still roughly distinguish the leakage amount and leakage frequency as shown in FIG6 , the piezoelectric part cannot provide accurate dripping frequency information.

[0048] Temperature affects the water absorption rate of liquid-absorbent expandable polymer (SAP). SAP's water absorption performance decreases with decreasing temperature. Therefore, the device's response was investigated under two conditions: summer (~30°C) and winter (~10°C). As shown in Figure 7, at higher temperatures, the device's response exhibits a step with each water drop, but the change gradually decreases. This may be due to the water-absorbent resin that has already absorbed water hindering further water absorption by the unabsorbed resin, or perhaps the piezoresistive component's ability to withstand pressure approaches saturation. However, at lower temperatures, the device exhibits almost no response after six water drops, indicating that it can operate at low temperatures, but with reduced performance. Figure 8 illustrates a similar phenomenon. Because seawater is rich in ions such as Ca2+ and Mg2+ that inhibit SAP's water absorption, the SAP's absorption rate and expansion ratio are significantly reduced. The increase is most pronounced with the first drop of seawater, and remains almost unchanged by the fifth drop. This indicates that, while performance may be affected, the device can still be used for building leak alarms in seawater environments.

Claims

1. A liquid leakage monitoring device, characterized in that: The invention comprises a piezo-resistive dual-mode sensor, a temperature sensor, an ion concentration sensor, a moisture sensing structure, a bracket and a detection circuit, wherein the moisture sensing structure comprises a liquid-absorbing swelling material and a liquid-absorbing layer, the surface of the bracket is an inclined plane, a first hollow and a second hollow are provided on the plane, the liquid-absorbing swelling material is filled in the first hollow, the piezo-resistive dual-mode sensor is arranged above the first hollow, the liquid-absorbing layer is arranged below the first hollow and the second hollow, the detection circuit is respectively connected to the piezo-resistive dual-mode sensor, the temperature sensor and the ion concentration sensor, and is used for calculating the liquid dripping frequency according to the piezoelectric signal of the piezo-resistive dual-mode sensor, and calculating the liquid leakage amount after the temperature signal of the temperature sensor and the concentration signal of the ion concentration sensor are compensated according to the piezoresistance signal of the piezo-resistive dual-mode sensor.

2. The liquid leakage monitoring device according to claim 1, characterized in that: The detection circuit comprises: A filtering and amplifying module, connected to the piezoelectric signal output terminal of the piezo-piezoresistive dual-mode sensor, and used for filtering and amplifying the piezoelectric signal; A first AD conversion module, used for performing analog-to-digital conversion on the signal output by the filtering and amplifying module; A voltage stabilization module, used for stabilizing the signal output by the first AD conversion module to obtain a digital piezoelectric signal; A resistance-to-voltage conversion module, connected to the piezoresistive signal output terminal of the piezoresistive-piezoresistive dual-mode sensor, and used for converting the piezoresistive signal in the form of current into a piezoresistive signal in the form of voltage; The second AD conversion module is used for performing analog-to-digital conversion on the piezoresistive signal in the form of voltage to obtain a digital piezoresistive signal; A microprocessor, used for calculating the liquid dripping frequency according to a preset first algorithm based on the digital piezoelectric signal, and for calculating the liquid leakage amount according to a preset second algorithm based on the digital piezoresistive signal, the temperature signal and the concentration signal; A transmission module, used for transmitting the liquid dripping frequency and the liquid leakage amount; The power module is used to supply power to each module.

3. The liquid leakage monitoring device according to claim 1, characterized in that: The resistance-to-voltage conversion module is specifically a Wheatstone bridge circuit consisting of four resistors.

4. The liquid leakage monitoring device according to claim 1, characterized in that: The first algorithm obtains the liquid dripping frequency by obtaining the interval time between two pulses of the digital piezoelectric signal.

5. The liquid leakage monitoring device according to claim 1, characterized in that: The second algorithm is specifically a calculation formula obtained by fitting the digital piezoresistive signal, temperature signal, concentration signal and corresponding liquid leakage obtained by multiple measurements.

6. The liquid leakage monitoring device according to claim 1, characterized in that: The piezo-piezoresistive dual-mode sensor includes a piezoresistive sensing layer, a piezoresistive electrode, a first piezoelectric substrate, a piezoelectric film, a piezoelectric electrode, a second piezoelectric substrate, a piezoresistive signal output end and a piezoelectric signal output end. The piezoresistive sensing layer, the piezoresistive electrode, the first piezoelectric substrate, the piezoelectric film, the piezoelectric electrode and the second piezoelectric substrate are stacked in sequence. The piezoresistive signal output end is connected to the piezoresistive electrode, and the piezoelectric signal output end is connected to the piezoelectric electrode.

7. The liquid leakage monitoring device according to claim 1, characterized in that: The stent is a stent formed of a high molecular polymer material.

8. The liquid leakage monitoring device according to claim 1, characterized in that: The second hollow is located downhill from the first hollow.

9. The liquid leakage monitoring device according to claim 1, characterized in that: The piezo-piezoresistive dual-mode sensor and the liquid absorbing layer are fixed on the bracket by adhesive tape.

10. The liquid leakage monitoring device according to claim 1, characterized in that: The liquid-absorbing and swelling material is a micro-granular high water-absorbent resin.

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