Piezoelectric fiber sensor for ultra-low flux bubble flow passive detection

Abstract

The application discloses a piezoelectric fiber sensor for passive detection of ultra-low flux bubble flow, and belongs to the field of passive sensor technology for gas flux detection. The core structure comprises an air inlet funnel, a flexible piezoelectric fiber composite porous membrane and a bubble release port. After low flux bubbles enter the air inlet funnel, the bubbles gradually accumulate below the flexible piezoelectric fiber composite porous membrane, and the gas pressure gradually increases. When the accumulated gas reaches the threshold of the porous membrane, the bubbles rapidly and automatically penetrate the porous membrane, causing the pressure of the accumulated gas below the membrane and the tensile load on the piezoelectric fiber to suddenly decrease. By relying on the piezoelectric effect, the interdigital electrodes on the surface of the porous membrane output a voltage signal. The application can significantly enhance the change amplitude of the load on the piezoelectric fiber and enhance the resolution of the sensor to ultra-low flux bubble flow, thereby realizing in-situ sensing and measurement of bubble flow in any underwater environment with ultra-low gas flux.

Description

Technical Field

[0001] This invention belongs to the field of passive sensor technology in gas flux detection, and mainly relates to a piezoelectric fiber sensor for passive detection of ultra-low flux bubble flow. Background Technology

[0002] Underwater bubble flow detection plays a crucial role in numerous fields, including marine resource exploration, seabed methane seepage monitoring, underwater engineering leak early warning, and lake and wetland ecological monitoring. However, bubbles released in natural aquatic environments are typically tiny (mostly sub-millimeter scale) and have extremely low gas flux (as low as 10 μL / min), making it difficult to capture and quantify their flow signals under passive conditions. Currently, underwater bubble flow sensing methods are mainly divided into acoustic and optical types. Acoustic detection methods rely on high-energy-consuming equipment such as ultrasonic transducers and power amplifiers, and the ultrasonic sensing signals used are easily affected by interference. Their inversion models are also difficult to accurately adapt to the size and motion characteristics of sub-millimeter-sized bubbles. Optical detection methods require high-energy-consuming equipment such as image acquisition devices and electric light sources, as well as complex visual detection algorithms. Furthermore, their measurement accuracy is easily affected by water turbidity and suspended impurities. These technical bottlenecks prevent existing methods from meeting the long-term, in-situ, passive sensing requirements for ultra-low flux underwater bubble flow. Therefore, there is an urgent need to develop an underwater passive sensor capable of detecting ultra-low flux bubble flow. Summary of the Invention

[0003] To achieve long-term, in-situ, self-powered sensing of underwater bubble flow rate, this invention discloses a piezoelectric fiber sensor for passive detection of ultra-low flux bubble flow rate. This sensor relies on liquid surface tension to automatically accumulate low-flux bubbles. Once a constant threshold is reached, the bubbles quantitatively release gas. The piezoelectric effect is used to convert the pressure jump before and after bubble release into an electrical signal output. The total volume and average flow rate of the gas flowing through the sensor are derived by inverting the peak count of the output electrical signal.

[0004] The piezoelectric fiber sensor for passive detection of ultra-low flux bubble flow includes an inlet funnel, a flexible piezoelectric fiber composite porous membrane, and a bubble release port. The flexible piezoelectric fiber composite porous membrane is installed above the inlet funnel and completely covers its upper port. The bubble release port is installed above the flexible piezoelectric fiber composite porous membrane and cooperates with the upper port of the inlet funnel to press and fix the edge of the flexible piezoelectric fiber composite porous membrane.

[0005] The flexible piezoelectric fiber composite porous membrane structure includes a flexible substrate, piezoelectric fibers, and flexible interdigitated electrodes. The flexible substrate is circular, comprising a central circular region and an outer annular region. The central circular region of the flexible substrate has densely arranged circular through-holes of the same size, with diameters ranging from 0.8 to 1.7 mm, and adjusted according to the target threshold of the flexible piezoelectric fiber composite porous membrane. A large number of piezoelectric fibers are embedded radially within the outer annular region of the flexible substrate. One end of each piezoelectric fiber is located at the inner edge of the annular region, and the other end extends to the outer edge of the annular region, arranged radially. The diameter of each piezoelectric fiber ranges from 100 to 300 μm, with polarization along its length and operating in d33 mode. The flexible interdigitated electrodes are in pairs, annular in shape, with parallel alternating poles, and are attached to the lower surface of the piezoelectric fibers. The piezoelectric fibers and flexible interdigitated electrodes are perpendicularly intersecting and embedded within the flexible substrate, their surfaces being enclosed by the flexible substrate.

[0006] The lower port of the air inlet funnel has a larger diameter than the upper port, used to collect rising air bubbles in the water. After entering the air inlet funnel, the air bubbles gradually accumulate below the flexible piezoelectric fiber composite porous membrane. The gas pressure causes the flexible piezoelectric fiber composite porous membrane to gradually bulge upwards. The flexible piezoelectric fiber composite porous membrane has a threshold that is inversely proportional to the pore size. When the accumulated gas volume reaches the threshold of the flexible piezoelectric fiber composite porous membrane, the gas passes through the through-holes of the flexible piezoelectric fiber composite porous membrane and is released instantaneously. The gas pressure on the lower surface of the flexible piezoelectric fiber composite porous membrane and the tensile load on the piezoelectric fibers decrease abruptly. Relying on the piezoelectric effect, the flexible interdigitated electrodes of the flexible piezoelectric fiber composite porous membrane output a voltage signal.

[0007] In the piezoelectric fiber sensor for passive detection of ultra-low flux bubble flow, both the inlet funnel and the bubble release port are made of corrosion-resistant rigid materials; in the flexible piezoelectric fiber composite porous membrane, the flexible substrate is made of flexible polymer materials such as silicone rubber or polydimethylsiloxane (PDMS), the piezoelectric fiber is made of lead zirconate titanate piezoelectric ceramic (PZT), and the flexible interdigitated electrode is made of silver nanowires or liquid metal; the water droplet contact angle on the surface of the flexible substrate is acute, and the automatic accumulation and quantitative release of underwater low flux bubbles are achieved by relying on the surface tension of the liquid.

[0008] The working principle of the piezoelectric fiber sensor for passive detection of ultra-low flux bubble flow is as follows: The water droplet contact angle on the surface of the flexible substrate is acute, ensuring that an upwardly convex gas-liquid interface is generated inside the circular through-hole in the central circular area of ​​the flexible substrate. This generates a downward Laplace pressure during the bubble accumulation stage, preventing gas from passing through the through-hole. Before the gas accumulated under the flexible piezoelectric fiber composite porous membrane reaches the threshold, the bubbles continue to accumulate, and the gas pressure gradually increases, causing the flexible piezoelectric fiber composite porous membrane to bulge upward, and the piezoelectric fibers to elongate under tension. Once the accumulated gas reaches the threshold, it is released instantaneously through the through-hole, causing a sudden decrease in the gas pressure on the lower surface of the flexible piezoelectric fiber composite porous membrane. The flexible piezoelectric fiber composite porous membrane quickly rebounds to its original shape. Correspondingly, the tensile load on the piezoelectric fibers decreases instantaneously, and relying on the piezoelectric effect, the flexible interdigitated electrode outputs a voltage signal. Since the flexible piezoelectric fiber composite porous membrane has a fixed threshold, the volume of gas released each time is... V The value is approximately constant (0), and each voltage signal output corresponds to a quantitative bubble release process. Therefore, it is possible to statistically analyze the data over a period of time. t Number of peak values ​​of the internal output voltage signal n The total volume of the bubbles flowing through the piezoelectric fiber sensor within the corresponding time period is calculated. V and average flow Q The calculation formula is as follows:

[0009]

[0010] Compared with the prior art, the present invention has the following advantages: This invention is a passive bubble flow sensor that utilizes a specially designed flexible piezoelectric fiber composite porous membrane as both a sensing element and a conversion element. While sensing the pressure change before and after bubble release and realizing the deformation of the piezoelectric fiber structure, it outputs a voltage signal at the moment of bubble release using the piezoelectric effect. The sensor itself does not consume any energy and does not require a power supply, making it very suitable for in-situ long-term passive sensing and detection of ultra-low flux bubble flow underwater.

[0011] This invention relies on liquid surface tension to achieve quantitative release of ultra-low flux bubbles after they accumulate to a constant threshold. The total gas volume and average flow rate flowing through the sensor are derived by inverting the number of peaks in the output electrical signal. Based on its working principle, given a sufficiently long measurement time, the sensor can accumulate enough gas for release and output a voltage signal. Therefore, its flow measurement range is not limited by low gas flux, thus breaking through the threshold barrier of traditional sensing technologies. It can perform bubble flow rate sensing and measurement in any ultra-low gas flux underwater environment, enhancing the ability to distinguish ultra-low flux bubble flow rates. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a structural diagram of the sensor of the present invention.

[0014] Figure 2 This is a cross-sectional view of the overall structure of the sensor of the present invention.

[0015] Figure 3 This is a top view of the flexible piezoelectric fiber composite porous membrane inside the sensor of the present invention.

[0016] Figure 4 This is a bottom view of the flexible piezoelectric fiber composite porous membrane inside the sensor of the present invention.

[0017] Figure 5 This is a cross-sectional view of the flexible piezoelectric fiber composite porous membrane inside the sensor of the present invention.

[0018] Figure 6 The shape change of the flexible piezoelectric fiber composite porous membrane during the operation of the sensor of the present invention is due to the accumulation and release of air bubbles. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products or devices.

[0021] like Figure 1 and Figure 2The piezoelectric fiber sensor shown is for passive detection of ultra-low flux bubble flow, including an inlet funnel 1, a flexible piezoelectric fiber composite porous membrane 2, and a bubble release port 3. The flexible piezoelectric fiber composite porous membrane 2 is installed above the inlet funnel 1 and completely covers the upper port of the inlet funnel 1. The bubble release port 3 is installed above the flexible piezoelectric fiber composite porous membrane 2 and is installed in conjunction with the upper port of the inlet funnel 1 to press and fix the edge of the flexible piezoelectric fiber composite porous membrane 2. Both the inlet funnel 1 and the bubble release port 3 are made of corrosion-resistant rigid materials.

[0022] like Figure 3 , Figure 4 and Figure 5 As shown, the flexible piezoelectric fiber composite porous membrane 2 comprises a flexible substrate 21, piezoelectric fibers 22, and flexible interdigitated electrodes 23. The flexible substrate 21 is circular, including a central circular region and an outer annular region. The central circular region of the flexible substrate 21 has densely arranged circular through-holes of the same size, with diameters ranging from 0.8 to 1.7 mm, and the actual diameter is set according to the target threshold of the flexible piezoelectric fiber composite porous membrane 2. A large number of piezoelectric fibers 22 are embedded radially within the outer annular region of the flexible substrate 21. One end of each piezoelectric fiber 22 is located at the inner edge of the annular region, and the other end extends to the outer edge of the annular region, forming a radial pattern. The piezoelectric fibers 22 are arranged with a diameter ranging from 100 to 300 μm, with the polarization direction along the length and the operating mode being d33 mode. There is a pair of flexible interdigitated electrodes 23, which are ring-shaped and arranged alternately in parallel, attached to the lower surface of the piezoelectric fibers 22. The piezoelectric fibers 22 and flexible interdigitated electrodes 23 are perpendicularly intersecting and embedded in the interior of the flexible substrate 21, and their surfaces are covered by the flexible substrate 21. The flexible substrate 21 is made of flexible polymer materials such as silicone rubber or polydimethylsiloxane (PDMS), the piezoelectric fibers 22 are made of lead zirconate titanate piezoelectric ceramic (PZT), and the flexible interdigitated electrodes 23 are made of silver nanowires or liquid metal.

[0023] like Figure 6As shown, the lower port of the air inlet funnel 1 has a larger diameter than the upper port, which is used to collect rising bubbles in the water. When the sensor is working, the bubbles first enter the air inlet funnel 1. Since the water droplet contact angle on the surface of the flexible substrate 21 is acute, an upward-convex gas-liquid interface is generated inside the circular through-hole in the central circular area of ​​the flexible substrate 21, thereby generating a downward Laplace pressure to prevent gas from passing through the through-hole, so that the bubbles automatically accumulate below the flexible piezoelectric fiber composite porous membrane 2 after entering the air inlet funnel 1. As the bubbles accumulate, the gas pressure gradually increases, causing the flexible piezoelectric fiber... The composite porous membrane 2 gradually bulges upwards, and the piezoelectric fiber 22 elongates under tension. The flexible piezoelectric fiber composite porous membrane 2 has a threshold that is inversely proportional to its pore size. When the accumulated gas volume reaches the threshold of the flexible piezoelectric fiber composite porous membrane 2, the gas is released instantaneously through the pores, and the gas pressure on the lower surface of the flexible piezoelectric fiber composite porous membrane 2 decreases sharply, causing the flexible piezoelectric fiber composite porous membrane 2 to quickly rebound and return to its original shape. Correspondingly, the tensile load on the piezoelectric fiber 22 decreases instantaneously, and relying on the piezoelectric effect, the flexible interdigitated electrode 23 outputs a voltage signal. The flexible piezoelectric fiber composite porous membrane 2 has a fixed threshold, therefore the volume of gas released after each accumulation is... V The value is approximately constant (0), and each voltage signal output corresponds to one quantitative bubble release process. Therefore, by statistically analyzing a period of time... t Number of peak values ​​of the internal output voltage signal n The total volume of the bubble flowing through the piezoelectric fiber sensor within the corresponding time period is inverted. V and average flow Q .

[0024] To address the challenge of passively measuring ultra-low flux bubble flow rates underwater, this invention discloses a passive flow sensor based on flexible piezoelectric fiber composite materials. Its core structure includes an inlet funnel, a flexible piezoelectric fiber composite porous membrane, and a bubble release port. Low-flux bubbles enter the inlet funnel and gradually accumulate below the flexible piezoelectric fiber composite porous membrane, causing the gas pressure to gradually increase. When the accumulated gas volume reaches the threshold of the porous membrane, the bubbles rapidly and automatically release through the membrane, resulting in a sudden decrease in the pressure of the accumulated gas beneath the membrane and the tensile load on the piezoelectric fibers. Relying on the piezoelectric effect, the interdigitated electrodes on the surface of the porous membrane output a voltage signal. This invention significantly enhances the amplitude of load changes on the piezoelectric fibers, thereby improving the sensor's resolution for ultra-low flux bubble flow rates.

[0025] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A piezoelectric fiber sensor for passive detection of ultra-low flux bubble flow, characterized in that: Includes an air inlet funnel, a flexible piezoelectric fiber composite porous membrane, and a bubble release port; The flexible piezoelectric fiber composite porous membrane is installed above the air inlet funnel, completely covering the upper port of the air inlet funnel; the bubble release port is installed above the flexible piezoelectric fiber composite porous membrane and cooperates with the upper port of the air inlet funnel to press and fix the edge of the flexible piezoelectric fiber composite porous membrane. The flexible piezoelectric fiber composite porous membrane structure includes a flexible substrate, piezoelectric fibers, and flexible interdigitated electrodes; the flexible substrate includes a central circular region and an outer annular region. The flexible substrate has densely arranged circular through holes of the same size in the central circular area; A large number of piezoelectric fibers are embedded in the annular region surrounding the flexible substrate along the radial direction; one end of each piezoelectric fiber is located at the inner edge of the annular region, and the other end extends to the outer edge of the annular region, arranged radially; there is a pair of flexible interdigitated electrodes, which are annular in shape, with the two poles arranged alternately in parallel, and attached to the lower surface of the piezoelectric fibers; the piezoelectric fibers and the flexible interdigitated electrodes are perpendicularly intersecting and embedded in the interior of the flexible substrate, and their surfaces are covered by the flexible substrate; The lower port of the air inlet funnel has a larger diameter than the upper port, used to collect rising bubbles in the water. After entering the air inlet funnel, the bubbles gradually accumulate below the flexible piezoelectric fiber composite porous membrane. As the bubbles accumulate, the gas pressure gradually increases, causing the flexible piezoelectric fiber composite porous membrane to gradually bulge upwards. When the accumulated gas volume reaches the threshold of the flexible piezoelectric fiber composite porous membrane, the gas passes through the pores of the flexible piezoelectric fiber composite porous membrane and is released instantaneously, causing a sudden decrease in the gas pressure on the lower surface of the flexible piezoelectric fiber composite porous membrane and the tensile load on the piezoelectric fibers. Relying on the piezoelectric effect, the flexible interdigitated electrodes of the flexible piezoelectric fiber composite porous membrane output a voltage signal. Each voltage signal output corresponds to a quantitative bubble release process, and the total volume and average flow rate of the bubbles flowing through the piezoelectric fiber sensor are obtained by inverting the number of peak values ​​of the output voltage signal.

2. The piezoelectric fiber sensor for passive detection of ultra-low flux bubble flow rate according to claim 1, characterized in that: Both the air inlet funnel and the bubble release port are made of corrosion-resistant rigid materials.

3. The piezoelectric fiber sensor for passive detection of ultra-low flux bubble flow rate according to claim 1, characterized in that: In the flexible piezoelectric fiber composite porous membrane, the flexible substrate is made of flexible polymer materials such as silicone rubber or polydimethylsiloxane, the piezoelectric fiber is made of lead zirconate titanate piezoelectric ceramic, and the flexible interdigitated electrode is made of silver nanowires or liquid metal.

4. The piezoelectric fiber sensor for passive detection of ultra-low flux bubble flow rate according to claim 1, characterized in that: The diameter of the piezoelectric fiber is set in the range of 100~300 μm, the polarization direction is the length direction, and the working mode is d33 mode.

5. A piezoelectric fiber sensor for passive detection of ultra-low flux bubble flow rate according to claim 1, characterized in that: The water droplet contact angle on the flexible substrate surface of the flexible piezoelectric fiber composite porous membrane is an acute angle. The diameter of the through holes in the central circular area of ​​the flexible substrate is set in the range of 0.8~1.7 mm, and is actually set according to the target threshold of the flexible piezoelectric fiber composite porous membrane. The threshold of the flexible piezoelectric fiber composite porous membrane is inversely proportional to the diameter of the through holes.

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