Multi-mode sensing integrated sensor for underwater environment

Abstract

The invention discloses a multi-mode sensing integrated sensor for an underwater environment. The multi-mode sensing integrated sensor comprises a hemisphere, a coplanar electrode, an elastomer film and an open shell, wherein the coplanar electrode comprises at least one of a first electrode, a second electrode, a third electrode and a temperature sensitive element; the open shell penetrates through the spherical surface of the hemisphere through the hollow area on the top surface of the open shell, so that the bottom surface of the hemisphere is arranged corresponding to the first electrode in the accommodating cavity of the open shell through the elastomer film, and the accommodating cavity is communicated with the external environment through the through area on the side surface of the open shell; and a reverse ionization electric sensing interface capable of changing the number of movable ions at the interface in response to the pressure borne by the hemisphere is formed at the interface where the microcosmic rough surface of the elastomer film is in contact with the first electrode. According to the invention, the flow velocity, flow direction, salinity, depth and temperature of the water body in the underwater environment can be simultaneously measured based on the electric signals output by the coplanar electrodes, and the sensor has the advantages of miniaturization, high sensitivity and high precision.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tactile sensors, and particularly relates to a multi-modal perception integrated sensor for underwater environment. BACKGROUND

[0002] With the global ocean observation system becoming more and more perfect, the demand for high-density and fine information perception is also increasing. Compared with traditional platforms, small-scale mobile platforms that can be deployed on a large scale have both concealment and mobility, and can not only flexibly penetrate unknown sea areas, but also operate in deep sea environment "stealthily", bringing new possibilities for marine military strategy and national interest protection. For complex aquatic environment, it is necessary to monitor multiple hydrological parameters in underwater environment, including depth, temperature, salinity, flow velocity and flow direction.

[0003] Traditional temperature-salinity-depth sensors are mostly based on cable type, ship body fixed type and towing type, and realize system packaging and water pressure resistance through large-size metal shell. In order to realize multi-parameter data acquisition, the traditional single system unified packaging integration method is often used, which further increases the size and weight of the sensing system, and brings a series of problems such as high power consumption, high cost and not easy to carry. Traditional flow velocity and flow direction sensors include electromagnetic type, thermal type, acoustic type and mechanical type. Most of these sensors need metal shell to protect internal components, which makes them not easy to operate underwater. Due to the need for strong power support and high-precision measurement, the power consumption is usually large, which further affects the endurance of the sensor. Moreover, the traditional flow velocity and flow direction sensor usually has single function, and it is difficult to integrate with other monitoring data.

[0004] The invention patent application with publication number CN119618277A provides a bending optical fiber multi-parameter sensor based on bionic side line, which can simultaneously monitor flow field direction, flow field flow velocity and flow field salinity. The application uses TPU flexible cantilever beam and four-quadrant optical fiber probe to convert the direction, flow velocity and salinity into optical intensity difference signals at one time, so that the fiber core acts as a salinity sensitive film, realizing the change of refractive index to light loss and then to voltage change. However, the application scheme needs external laser source and four-way photoelectric conversion, which cannot realize true miniaturization and low power consumption. Moreover, the spacing / angle between receiving and output optical fibers needs to be calibrated at micrometer level, which has great assembly difficulty and assembly man-hours.

[0005] Therefore, it is urgent to develop a small-sized and low-power multi-modal integrated perception system applicable to marine environment. SUMMARY

[0006] To solve the above technical problems, the application proposes a multi-modal perception integrated sensor for underwater environment based on the electro-tribological sensing mechanism, combined with the coplanar electrode and the underwater environment fusion technical concept, which can measure multiple hydrological parameters including flow velocity and flow direction in the underwater environment, and has the advantages of miniaturization, low power consumption, high sensitivity and high precision.

[0007] The multi-modal perception integrated sensor for underwater environment disclosed by the application comprises a hemisphere including a spherical surface and a bottom surface; a coplanar electrode including a substrate, a first electrode formed on the substrate, and at least one of a second electrode, a third electrode and a temperature sensitive element formed on the substrate, wherein the first electrode, the second electrode and the third electrode are all interdigital electrodes; an elastomer film arranged in the accommodating cavity, and one side of the elastomer film is a smooth surface and the other side is a micro-rough surface; an open shell including an accommodating cavity, a top surface hollow area and a side surface through area which are in communication with the accommodating cavity; the open shell passes through the spherical surface of the hemisphere through the top surface hollow area, so that the bottom surface of the hemisphere is arranged opposite to the single electrode through the elastomer film, and the accommodating cavity is in communication with the external environment through the side surface through area, so as to form an inverse electro-tribological sensing interface at the interface between the micro-rough surface of the elastomer film and the single electrode, which can change the number of movable ions at the interface in response to the pressure received by the hemisphere; the first electrode is configured to output an electrical signal based on the inverse electro-tribological sensing mechanism, and the electrical signal is negatively correlated with the pressure change amount applied to the spherical surface, which is used to perceive the flow velocity and flow direction of the water flow; the second electrode is configured to output an electrical signal which is used to perceive the water depth; the third electrode is configured to output an electrical signal which is used to perceive the salinity; and the temperature sensitive element is configured to output an electrical signal which is used to perceive the temperature.

[0008] Based on the above scheme, the multi-modal perception new paradigm for underwater environment proposed by the application designs the coplanar electrode integrated with multiple different sensing modes, in the flow velocity and flow direction sensing part, based on the open shell structure, the seawater which can be used as a natural electrolyte in the environment is used as part of the sensing structure, fills the interface between the micro-rough surface of the elastomer film and the first electrode (conductive surface), and constitutes an inverse electro-tribological sensing interface. When external pressure is applied, the electrolyte at the inverse electro-tribological sensing interface is partially extruded, reducing the number of ions at the interface, reducing the contact area between the electrode and the ions contained in the water body, thereby causing the super capacitor at the interface to decrease, which is just the opposite of the traditional positive electro-tribological sensing, which is an innovative environmental fusion inverse electro-tribological sensing mechanism. Through this open structure design, hydraulic balance is achieved, the hydrostatic pressure on both sides of the sensing interface is offset, self-adaptation in a multi-dimensional hydraulic environment without packaging is achieved, and high-precision detection of tactile information at any water depth is achieved. At the same time, the application also realizes water depth sensing based on the piezoresistive sensing mechanism, temperature sensing based on the thermistor effect, and salinity sensing based on the electro-tribological sensing mechanism.

[0009] The multi-modal perception integrated sensor for underwater environment has the following beneficial effects: (1) The application can realize high-robustness flow velocity and flow direction perception based on the stress structure design of the hemisphere. The unique geometric shape of the hemisphere can efficiently and linearly convert and decompose the water flow impact on the different directions of the hemisphere surface into normal pressure distribution on the different sensing units corresponding to the bottom surface and corresponding to the flow direction. Based on this, the flow direction can be accurately determined by interpreting the spatial distribution pattern of the capacitance signals of the multiple sensing units, and the flow velocity can be determined by analyzing the overall amplitude of the capacitance signals. Based on this principle, the problems of jamming, wear and biological attachment of the moving parts in the traditional underwater flow meter can be fundamentally avoided, so that the sensing structure has higher reliability and longer service life.

[0010] (2) The application adopts an innovative hydraulic balance design, which can break through the water depth limit when used in underwater environment. The hemisphere, elastomer membrane and coplanar electrode are fixed together through the innovative structure design of the open shell, and the hydraulic automatic balance is realized through the through zone design of the open shell, so that the hydrostatic pressure is counteracted on both sides of the sensing interface. This makes the sensor not sensitive to the hydrostatic pressure and only responds to the dynamic pressure (flow velocity), thereby solving the inherent contradiction that the traditional pressure sensor cannot simultaneously consider high-precision micro-pressure measurement (flow velocity) and huge hydrostatic pressure (water depth) due to range limitation in deep water environment, and realizing full-water-depth flow velocity and flow direction high-precision measurement from shallow water to deep water.

[0011] (3) The application realizes true multi-modal integration based on the design of the coplanar electrode. The application can realize flow velocity and flow direction perception based on the reverse electrostatic sensing mechanism, water depth perception based on the piezoresistive sensing mechanism, salinity perception based on the electrostatic sensing mechanism and temperature perception based on the thermoresistance effect by integrating the multi-region electrode distribution and lead design on a single substrate, thereby realizing independent, synchronous and in-situ measurement of the four key hydrological parameters, and avoiding the problems of large volume, complex installation and asynchronous data caused by the use of multiple discrete sensors.

[0012] (4) The application also has high modularity and design flexibility. The application can flexibly design the number, shape and arrangement density of the electrode units in the first electrode according to the hydrological parameter test requirements, cost considerations and performance requirements of the target application, so as to balance the resolution and computational complexity. The water depth, salinity or temperature perception function can also be selectively integrated according to actual needs.

[0013] (5) The application also has the characteristics of simple operation and low power consumption. The application does not need to use external laser sources or other photoelectric conversion circuits, has the characteristics of low power consumption, and does not involve the use of optical fibers, does not have micron-level calibration problems, and is simple to operate. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 Structure diagram of a multi-modal sensing integrated sensor in the embodiment; Figure 2 Exploded view of a multi-modal sensing integrated sensor in the embodiment; Figure 3 Electrode distribution diagram in a coplanar electrode; Figure 4 Exploded view of a multi-modal sensing integrated sensor in another scheme; Figure 5 Schematic diagram of inverse electrostatic sensing mechanism, where A0 is the initial contact area and A1 is the area after being pressed; Figure 6 Schematic diagram of water depth detection mechanism; Figure 7 Schematic diagram of salinity detection mechanism; Figure 8 Schematic diagram of a test model; Figure 9 In the middle: a)~c) are respectively the capacitance-pressure change curves when a 30°, 45°, and 60° tangential force is applied; d) is the capacitance-pressure curve when a 90° normal force is applied; Figure 10 The four graphs in the middle respectively represent the capacitance thermal force diagram under different pressure angles under the action of 3N force; Figure 11 In the middle: a)~g) are respectively schematic diagrams of controlling different water flow directions underwater; Figure 12 Capacitance thermal force diagram when the flow rate is 5m / s and the flow direction is simulated; Figure 13 Capacitance thermal force diagram when the flow rate is 5.5m / s and the flow direction is simulated; Figure 14 Capacitance thermal force diagram when the flow rate is 6m / s and the flow direction is simulated; Figure 15 Resistance-pressure curve of reaction depth; Figure 16 Capacitance-ion concentration change curve of reaction salinity; Figure 17 Resistance-temperature change curve of reaction temperature. DETAILED DESCRIPTION

[0015] For complex underwater environment, it is usually necessary to measure multiple key hydrological parameters including depth, temperature and salinity, flow velocity and flow direction by sensors arranged in the underwater environment simultaneously. The tactile sensing technology is one of the important paths to realize the measurement of these hydrological parameters, and its sensing mechanism mainly includes resistance type, capacitance type, piezoelectric type and triboelectric type. In recent years, the emerging triboelectric tactile sensing mechanism (referred to as "triboelectric sensing mechanism") provides a new idea for tactile measurement, and it has the highest mechanical capacitance sensitivity among all tactile and pressure sensors, which is at least three orders of magnitude higher than that of traditional parallel plate capacitive sensors.

[0016] It is particularly necessary to note that based on this, the applicant further considers that seawater itself is an electrolyte medium rich in ions, and if seawater can be directly used as a functional material for triboelectric sensors, the sensor structure will be greatly simplified, thereby making the underwater sensor more lightweight and having high environmental integration.

[0017] The application provides a multi-modal perception integrated sensor (referred to as "multi-modal sensor") for underwater environment, which adopts an integrated design and integrates multiple functional detection zones on a single structure, and can measure the temperature, salinity and depth of the underwater environment and the flow velocity and flow direction of the water flow.

[0018] The multi-modal perception integrated sensor provided by the application mainly includes a hemisphere, coplanar electrodes, an open shell and an elastomer film, wherein: the hemisphere includes a spherical surface and a bottom surface; the coplanar electrodes include a substrate, a first electrode formed on the substrate, and a second electrode, a third electrode and a temperature-sensitive element formed on the substrate, the first electrode, the second electrode and the third electrode are all single-sided electrodes; the elastomer film is arranged in a receiving cavity of the shell, and one side is a smooth surface and the other side is a micro-rough surface; the open shell includes a receiving cavity, a top surface hollow area communicating with the receiving cavity and a side surface through area communicating with the receiving cavity. Among them, the second electrode, the third electrode and the temperature-sensitive element can be selected to set at least one or more according to actual parameter measurement requirements.

[0019] The open shell passes through the spherical surface of the hemisphere through the top surface hollow area, so that the bottom surface of the hemisphere is arranged opposite to the first electrode through the elastomer film, and the micro-rough surface of the elastomer film is in contact with the first electrode, and the receiving cavity is communicated with the external environment through the side surface through area, so as to form an inverse triboelectric sensing interface at the contact interface of the rough surface of the elastomer film and the first electrode, which can respond to the change of the number of movable ions at the interface under the pressure of the hemisphere.

[0020] The first electrode is configured to output an electric signal based on a reverse ionization sensing mechanism, the electric signal being negatively correlated with a pressure variation amount applied to the hemispherical surface, and is used to sense a flow rate and a flow direction of the water flow. The second electrode is provided with a conductive carbon film on a surface thereof and is configured to output an electric signal based on a piezoresistive sensing mechanism, the electric signal being negatively correlated with a hydrostatic pressure acting on the surface of the second electrode, and is used to sense a water depth. The third electrode is configured to be directly exposed to the water body during use, and outputs an electric signal based on an ionization sensing mechanism, the electric signal being positively correlated with a salinity of seawater, and is used to sense the salinity. The temperature-sensitive element is configured to output an electric signal based on a thermal resistance effect, the electric signal being positively correlated with a temperature of seawater, and is used to sense a temperature change.

[0021] The technical solutions of the present application will be described clearly and completely below in combination with the drawings and embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0022] In the description of the present application, if terms indicating orientation or positional relationship such as "upper", "lower", "left", "right", "inner", "outer", "top", "bottom" and the like appear, they are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and are not intended to indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. For those skilled in the art, the specific meanings of the above terms in the present application can be understood in combination with specific circumstances. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, but can include other elements not clearly listed or inherent to the products or devices.

[0023] In combination with Figures 1 to 3 As shown in the drawings, the multi-modal sensor provided by the embodiments of the present application mainly includes an open shell 1, a hemispherical body 2, a silica gel ring 3, an elastomer film 4, and a coplanar electrode 5. The specific introduction of each part is as follows: The open shell 1 adopts an open structure design, which is mainly used to fix the hemispherical body, and at the same time needs to meet the requirement that water flow can enter the inside of the shell. The vertical projection of the open shell 1 is a circular ring structure, including a containing cavity formed by a top surface and a side surface. The top surface has a circular hollow area 11 at the center, and the diameter of the circular hollow area 11 is matched with the diameter of the bottom surface of the hemispherical body, and is usually equal to or slightly smaller than the diameter of the bottom surface of the hemispherical body, so as to fix the hemispherical body 2; the side surface has four support columns 12, which are distributed equidistantly and circumferentially along the edge of the circular top surface, and a through area 13 is formed between adjacent support columns 12.

[0024] Based on the innovative design of the aforementioned shell structure, the open shell 1 can pass through the hemisphere 2 via the circular hollow area 11 and be fixedly connected to the coplanar electrode 5; at the same time, it can also connect the internal cavity of the shell to the outside through the through area 13 between adjacent support columns 12, thereby allowing water to enter the interior of the shell and penetrate to the interface between the elastomer membrane 4 and the coplanar electrode 5. The cross-section of the cavity can be circular or a regular polygon such as a square.

[0025] The open-type housing 1 can be made of rigid materials such as resin, nylon, or polylactic acid (PLA). The open-type housing 1 can be fixedly connected to the coplanar electrode 5 by means of bonding or other methods.

[0026] The hemisphere 2 receives the force applied by the water flow, converts it, and transmits it to the elastomer membrane 4, thereby causing a change in the output capacitance to reflect the flow velocity and direction in the underwater environment. The hemisphere 2 is a solid structure, comprising an integrally formed spherical surface 21 and a bottom surface 22. The bottom surface 22 and part of the spherical surface 21 (mainly the bottom area) are placed within the accommodating cavity of the open shell 1, and the bottom surface 22 is in contact with the elastomer membrane 4. The hemisphere 2 can be made of a high-hardness homogeneous material with an elastic modulus of 2~30 GPa, such as nylon, polylactic acid (PLA), acrylic acid (PMMA), epoxy resin (EP), polycarbonate (PC), and other rigid materials.

[0027] It is worth noting that this invention employs a hemispherical structure design, similar to a force converter. Its core function is to convert and decompose the complex stress generated by water flows of different directions and sizes acting on its hemispherical surface into an asymmetrical spatial distribution of normal pressure acting on different sensing units on the bottom surface. Specifically, when the water flow impacts vertically, the vertical normal force applied to the center of hemisphere 2 (i.e., the apex position) results in a centrally symmetrical pressure distribution transmitted to the elastic membrane 4, with consistent capacitance changes across all sensing units. However, when the water flow impacts obliquely, i.e., when a shear force at a certain angle to the normal direction is applied to the hemisphere, an asymmetrical pressure distribution is formed, with the sensing units facing the flow experiencing significantly greater pressure than those facing the flow away. Therefore, by analyzing the spatial distribution of the relative strengths of the capacitance signals output by multiple sensing units, the direction of water flow (i.e., the flow direction) can be determined; and by analyzing the overall amplitude of the capacitance signal changes, the water velocity (i.e., the flow rate) can be determined.

[0028] The silicone ring 3 is a circular structure arranged inside the open housing 1. Its inner ring passes through the hemisphere 2 and is adjacent to the elastomer membrane 4, and is fixed by the open housing 1. As a pre-tightening element, the inner diameter of the silicone ring 3 should also match the diameter of the bottom surface of the hemisphere, usually slightly smaller than the diameter of the hemisphere 2; the outer diameter is usually larger than the diameter of the bottom surface of the hemisphere, so that the silicone ring 3 can fit against the side of the open housing 1.

[0029] It should be noted that the silicone ring 3 can also be replaced with materials such as rubber or thermoplastic polyurethane (TPU) to increase the preload. After the open shell passes through the spherical surface of the hemisphere, the silicone ring 3, acting as a preload element, can apply preload pressure to the elastic membrane, enhancing the reliability and tightness of the connection between the hemisphere 2, the elastic membrane 4, and the open shell 1, preventing relative slippage between the structures under load, and ensuring signal stability.

[0030] In another alternative, the silicone ring 3 can also be fixed to the inner side of the top surface of the open housing 1, forming an integral part of the open housing 1.

[0031] The elastomeric membrane 4 is circular and positioned between the hemisphere 2 and the coplanar electrode 5, and is fixed by the open housing 1. The diameter of the elastomeric membrane 4 can be designed to be approximately the same as the outer diameter of the silicone ring 3 or the diameter of the hemisphere base, so as to better clamp it between the open housing 1 and the coplanar electrode 5. The material selected for the elastic membrane usually has resilience and chemical stability, with an elastic modulus in the megapascal range. Specifically, it can be made of materials such as polydimethylsiloxane (PDMS), polyurethane, polyimide, thermoplastic polyurethane (TPU), and rubber.

[0032] One surface of the elastomer membrane 4 is smooth; the other surface is micro-rough. The smooth surface is adjacent to the hemisphere 2, and the rough surface is adjacent to the coplanar electrode 5.

[0033] It is worth noting that the micro-roughness of the surface is primarily for achieving the reverse ionization sensing mechanism. The micro-roughness of the elastomer membrane 4, the corresponding electrodes in the coplanar electrodes, and the ions in the water flow contained between them together constitute the "reverse ionization sensing interface." Therefore, the core characteristic of the micro-roughness is its ability to change the volume of liquid contained between it and the electrodes under external pressure. This change in liquid volume directly leads to a change in the number of mobile ions at the interface, thereby achieving electrical signal output.

[0034] In the optional solutions, the micro-rough surface can be formed by the inherent micro-morphology of the material itself, or by subsequent processing. The inherent micro-morphology of the material mainly includes the micro-rough structure and porous structure of the elastic membrane surface. The rough surface formed by subsequent processing can be a micro-rough structure, a porous structure, or an array of micro-protrusions (such as micropillars, micro-hemisphers, etc.). Specifically, it can be fabricated using MEMS processes, template methods, self-forming methods, 3D printing methods, printing methods, etc. For example, the micro-rough structure can also be obtained by directly curing uncured elastomer material on sandpaper.

[0035] The coplanar electrode 5 includes a substrate and electrodes and a temperature-sensitive element formed on the substrate, including electrodes 51, 52, and 53. The temperature-sensitive element is a metal coil 54, thus forming four functional detection zones: a flow velocity and direction detection zone, a depth detection zone, a salinity detection zone, and a temperature detection zone. All electrodes employ an interdigitated structure made of conductive material. Considering the long-term stability and cost of the sensor in underwater environments, the conductive material should possess good chemical stability and conductivity. Copper electrodes plated with gold or platinum can be used to increase corrosion resistance and conductivity.

[0036] In the flow velocity and direction detection area, electrode 51 includes multiple independent and identical electrode units, which are distributed in a rotationally symmetrical manner with the projection point of the center of the bottom surface of the hemisphere as the center. Specifically, the arrangement can be that the electrodes are arranged at equal angular intervals on the same circumference with the projection point of the center of the bottom surface of the hemisphere as the center; or, they can be arranged in a regular polygon vertex array with the projection point as the center.

[0037] The specific number of electrode units can be determined based on the target flow direction resolution requirements. Understandably, increasing the number of electrode units allows for the acquisition of denser spatial pressure sampling points, thereby helping to improve the resolution of flow direction detection.

[0038] In one design, electrode 51 typically comprises 4N (N≥1) independent electrode units, divided into four groups, used to detect forces in the east, south, west, and north directions. When N equals 1, each independent electrode unit constitutes a measurement channel; when N is greater than 1, for example, with 8 or 16 electrode units, the signals from adjacent 2 or 3 electrode units are fused to form a single measurement channel, thereby improving the resolution of flow direction detection. The 4N electrode units are uniformly arranged around a common center on the circumference. Specifically, the 4N electrode units are arranged at equal angular intervals on the same circumference, with the projection point of the center of the hemispherical base onto the coplanar electrode 5 as the center. Each electrode unit can be designed as an array structure formed by interdigitated electrodes to improve the sensitivity and signal-to-noise ratio of the sensing signal.

[0039] Electrode 51 and the elastic membrane 4 directly above it together form a flow velocity and direction detection zone. Each electrode unit in electrode 51 works in conjunction with its corresponding region on the elastic membrane 4 to form a sensing unit, used to sense changes in pressure distribution in a specific direction. Based on the change data from all sensing units, the flow velocity and direction of the water can be calculated after processing.

[0040] It should be noted that electrode 51 is located directly below hemisphere 2, and can be designed as a circular structure with the same diameter as the elastomer membrane 4. Correspondingly, the electrode unit is a fan-shaped structure with its apex pointing towards the center of the circle. In other designs, when the elastomer membrane 4 is square, electrode 51 can also be designed as a square that matches its shape and size.

[0041] In the depth detection area, a conductive carbon film is coated on the surface of electrode 52. The conductive carbon film is tightly adhered to the surface of electrode 52, together forming a piezoresistive sensor. Specifically, the conductive carbon film can be tightly and gaplessly fixed to the surface of electrode 52 by means of bonding, deposition, or pressing.

[0042] Understandably, conductive carbon films typically contain numerous conductive materials such as carbon nanotubes, graphene sheets, or carbon black particles, with tiny gaps and contact points between them. During use, the hydrostatic pressure from water depth applies pressure to the conductive carbon film, causing changes in its internal conductive pathways and altering its resistance. Therefore, water depth can be sensed through the resistance signal output from the depth detection zone. The salinity detection zone is based on an ionization sensing mechanism. Unlike electrode 52, electrode 53 is directly exposed and in direct contact with seawater. The double-layer capacitance per unit area formed at the interface between electrode 53 and seawater increases with increasing ion concentration in the seawater. Since salinity is positively correlated with ion concentration, seawater salinity information can be obtained by measuring the total interfacial capacitance of electrode 53, showing a positive correlation between the two.

[0043] In the temperature detection zone, the metal coil 54 serves as a temperature-sensitive element, primarily used to sense changes in seawater temperature. The detection principle of the temperature detection zone is mainly based on the resistance effect of metals. When the ambient temperature changes, the resistance value of the metal coil 54 changes accordingly. Therefore, by accurately measuring the change in resistance of the metal coil 54, the temperature of the seawater can be calculated.

[0044] The metal coil 54 can be formed on the substrate of the coplanar electrodes through processes such as photolithography, etching, and electroplating. The material is typically a metal resistive material with a positive temperature coefficient, commonly platinum, nickel, copper, or nickel-iron alloys. In a preferred embodiment, an insulating protective layer can be encapsulated on the surface of the metal coil 54 to prevent electrolytic corrosion in an underwater environment. Specifically, the insulating protective layer can be made of a thin insulating material with high thermal conductivity, such as silicone gel or pyrene.

[0045] The substrate primarily serves as the base material for forming the electrodes in the coplanar electrode 5. However, since the sensor is used in a complex underwater environment and may be subject to water flow impacts and collisions with underwater organisms, this invention preferably uses a flexible substrate as the substrate for the coplanar electrode. The excellent bending and impact resistance of the flexible substrate significantly improves the reliability and lifespan of the multimodal sensor during long-term underwater operation. The flexible substrate can be made of polyimide (PI), but given the corrosive nature of the underwater environment, fluoropolymers with excellent corrosion resistance, such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and perfluoroalkoxyalkanes (PFA), are also preferred.

[0046] Based on the above structure, the multimodal sensor achieves flow velocity and direction detection through the coordinated use of the open housing 1, hemisphere 2, silicone ring 3, elastomer membrane 4, and electrodes 51 in the coplanar electrodes 5. To accommodate open housing 1 designs of different shapes and optimize force transmission, the hemisphere 2 may further include a base 23, which can be integrally formed with its bottom surface.

[0047] In one alternative design, the cross-section of the accommodating cavity of the open housing 1 is circular, with a diameter larger than that of the circular hollow area 11. Correspondingly, the elastomer membrane 4 and the electrode 51 are also circular, with diameters approximately equal to the diameter of the accommodating cavity. In this case, the elastomer membrane 4 and the bottom surface of the hemisphere 2 are not sized mismatched. The base 23 ensures that the force is effectively transmitted from the smaller bottom surface of the hemisphere to the entire circular sensing area, that is, the force on the hemisphere 2 is uniformly transmitted to the circular flow direction detection area formed by the elastomer membrane 4 and the electrode 5.

[0048] For example, the cross-section of the accommodating cavity in the open housing 1 is circular, wherein the diameter of the circular hollow area 11 is 18 mm, the diameter of the accommodating cavity is approximately 22 mm, and the height is approximately 2.4 mm. The bottom diameter of the hemisphere 2 is 18 mm; the diameter of the base 23 is 22 mm, and the thickness is 1 mm. The inner diameter of the silicone ring 3 is 18 mm, the outer diameter is 22 mm, and the thickness is 1 mm. The diameter of the elastomer membrane 4 is 22 mm, and the thickness is 0.4 mm.

[0049] In another alternative, if the cross-section of the accommodating cavity is square or other centrosymmetric structure, and the elastomer membrane 4 and the coplanar electrode 5 and the middle electrode 51 are also square or other centrosymmetric structures, then the shape matching and force transmission can also be achieved through the base 23.

[0050] In yet another alternative, such as Figure 4As shown, the open-shell housing 1 is divided into upper and lower parts, namely, an upper shell and a lower shell. The upper and lower shells can be connected and fixed by means of adhesive, snap-fit, threaded connection, etc., forming an open-shell structure after being assembled. The hollow area is located on the surface of the upper shell and can be designed as a circle, square or other regular polygon structure. When the upper and lower shells are assembled, at least two opposite through areas are formed between adjacent support columns. After installation, the hemisphere 2, silicone ring 3, elastomer membrane 4 and coplanar electrode 5 are arranged in the accommodating cavity enclosed by the upper and lower shells.

[0051] For example, the cross-section of the accommodating cavity of the open shell 1 is square, and the hollow area on the top surface is also square. The side length of the upper and lower shells is 15.6 mm, and the height of the accommodating cavity formed after assembly is approximately 2.4 mm; the side length of the hollow area of ​​the upper shell is 10 mm. The base of the hemisphere 2 is square, with a side length of 13.3 mm, and the diameter of the hemisphere 2 is 10 mm. The elastomer membrane 4 is also square, with a side length of 10 mm and a thickness of 0.3 mm. The silicone ring is also square, with a side length of 13.3 mm, and the diameter of the circular hollow area in the middle is 10 mm, with a thickness of 1 mm. In the coplanar electrode 5, the electrode 51 has an overall square structure, comprising 2*2 identical electrode units.

[0052] It is understood that the present invention does not limit the specific structural form of the open shell 1, as long as it can pass through the spherical surface of the hemisphere 2 and fix its bottom surface to the coplanar electrode surface 5, and ensure that water can be injected into the accommodating cavity of the open shell 1 to penetrate into the interface where the elastomer membrane 4 and the coplanar electrode 5 are in contact.

[0053] Furthermore, the structural design of the base 23 provides a space to accommodate the diameter fit tolerance between the hemisphere 2 and the circular hollow area of ​​the open shell 1. This ensures that the hemisphere 2 is reliably fixed and provides tolerance for the assembly gap between the two, thereby ensuring a good fit between the hemisphere 2 and the open shell 1.

[0054] In multimodal sensors, the arrangement of various functional detection areas is mainly considered from the perspectives of sensor miniaturization, integration, and lead-wire packaging. In one optional solution, a combination of... Figure 3 As shown, electrode 51 is located at the center of coplanar electrode 5, while electrode 52, electrode 53 and metal coil 54 are arranged around electrode 51 in a compact layout, forming a circular structure.

[0055] Furthermore, the external wires of electrodes 51, 52, 53, and the metal coil 54 can be designed to converge and exit from the same location in the same direction. This design greatly simplifies the interface between the sensor and external devices, optimizes the packaging process, and makes the sensor structure compact and aesthetically pleasing. In other alternative solutions, the various functional detection areas can be designed in other shapes or arrangements according to actual application requirements. Furthermore, in other alternative solutions, at least one or two of electrodes 52, 53, and the metal coil 54 can be used, depending on the actual application requirements.

[0056] The multimodal sensor provided by this invention is based on the above-mentioned structural features, and its working principle mainly involves the following parts: Flow velocity and direction sensing is primarily achieved through a flow velocity and direction detection zone based on the reverse ionization sensing mechanism. It is understandable that water flow directly generates distributed normal and shear forces on a solid surface. For any point on the solid surface, the force it experiences can be decomposed into two components: a shear force parallel to the tangential plane at that point and a normal force perpendicular to the tangential plane at that point.

[0057] It is particularly important to note that in this invention, the change in water flow direction is directly reflected in the change in the direction of the shear force acting on the surface of the hemisphere. This invention does not directly measure surface stresses such as normal or tangential forces; instead, it uses the geometric structure of the hemisphere to convert and integrate the surface stresses into a macroscopic normal pressure distribution field at the bottom, corresponding one-to-one with the flow direction. This indirect measurement strategy is key to achieving low-cost, high-reliability detection of water flow velocity and direction.

[0058] Flow velocity detection typically relies on water flow forces of varying magnitudes acting in the same direction. When water impacts a hemisphere at a fixed angle, the total force (i.e., total pressure) exerted on the reverse ionization sensing interface increases with increasing flow velocity. This increased total pressure is transmitted through the hemisphere, transforming into a stronger normal pressure acting on the reverse ionization sensing interface. This normal pressure intensifies the microscopic deformation at the reverse ionization sensing interface, resulting in a significant reduction in interface capacitance. Therefore, by monitoring the attenuation of the capacitance signal output by electrode 51, the magnitude of the water flow velocity can be calculated.

[0059] Flow direction detection typically relies on the same magnitude of water flow force impacting a hemisphere from different directions. The symmetrical structure of the hemisphere efficiently converts the shear forces from different angles into an asymmetrical normal pressure distribution applied to different spatial points on the reverse ionization sensing interface. Specifically, the reverse ionization sensing interface facing the flow will experience a much greater normal pressure than the reverse ionization sensing interface facing the backflow, resulting in a much greater attenuation of the capacitance signal in the former than in the latter. By interpreting the relative strength patterns of the capacitance signals among the multiple circumferentially symmetrically distributed electrode units in electrode 51, the direction of the water flow can be accurately determined.

[0060] When the multimodal sensor is placed in an underwater environment, seawater enters the interior of the open housing 1 through the through-area and permeates into the reverse ionization sensing interface within the accommodating cavity. Ions in the seawater serve as part of the sensing structure. For example, sodium ions are adsorbed onto the negative electrode surface of electrode 51, and chloride ions are adsorbed onto the positive electrode surface of electrode 51. An electric double layer is formed on the electrode surface, consisting of one layer of electrons and one layer of ions.

[0061] Combination Figure 5 As shown, when the multimodal sensor is subjected to force, the hemisphere 2 transmits the force to the elastic membrane 4, causing the elastic membrane 4 to deform. This increases the contact area between the rough surface of the membrane and the electrode 51, resulting in some liquid being squeezed out of the reverse ionization sensing interface. The number of mobile ions decreases, thus reducing the interfacial supercapacitance at the reverse ionization sensing interface. This is the opposite of traditional forward ionization sensing, and this invention defines it as the "reverse ionization" principle. Therefore, the direction of seawater flow in the underwater environment is reflected by the capacitance change caused by the difference in pressure distribution among the electrode units in electrode 51, and the velocity of seawater flow in the underwater environment is reflected by the total capacitance change output by the electrode units in electrode 51.

[0062] This invention is based on this reverse electrostatic sensing mechanism. Through the structural design of the open shell 1, hydraulic balance is achieved, allowing the hydrostatic pressure (i.e., static pressure) to cancel out on both sides of the elastic membrane 4. The dynamic pressure (i.e., hydrodynamic pressure) generated by the water flow impact is transmitted through the hemisphere 2, acting solely on the smooth surface of the elastic membrane 4, thereby inducing effective microscopic deformation of the rough surface. This design makes the sensor insensitive to hydrostatic pressure, responding only to dynamic pressure, thus ensuring the accuracy and resolution of flow velocity and direction measurements at different water depths.

[0063] The depth sensing component primarily utilizes a depth detection zone based on a piezoresistive sensing mechanism. The ambient hydrostatic pressure is typically proportional to the water depth at the sensor's location. When a multimodal sensor is placed underwater, the hydrostatic pressure varies at different water depths. Figure 6 As shown in the schematic diagram of the depth detection area, when the water depth increases, the hydrostatic pressure increases and acts on the conductive carbon film, compressing the film and causing microscopic structural deformation. This reduces the spacing between the conductive materials within the film, enhances the connectivity of the internal conductive network, and consequently lowers the volume resistance. The resistance signal output by electrode 52 is negatively correlated with the water depth; by detecting this resistance value, water depth sensing can be achieved.

[0064] The salinity sensing component primarily utilizes an ionization sensing mechanism based on the double-layer capacitance at the electrode-solution interface within the salinity detection region. Seawater salinity is positively correlated with the ion concentration in seawater, and the ion concentration directly affects the conductivity of seawater. Combined with... Figure 6As shown in the schematic diagram of the salinity detection area, when the multimodal sensor is placed in an underwater environment, the exposed electrode 53 is in direct contact with ions in the seawater. The ion-electron double layer structure formed at the interface is equivalent to a microscopic capacitor, and its capacitance per unit area is determined by the ion concentration at the interface. When the seawater salinity increases, the ion concentration increases, resulting in a more compact ion distribution in the double layer structure, thereby significantly increasing its capacitance per unit area. By measuring the change in this total interfacial capacitance, the salinity value of the seawater can be calculated.

[0065] The temperature sensing part is mainly realized through a temperature detection zone based on the resistance effect. The multimodal sensor is placed in an underwater environment. The metal coil 54 serves as a temperature-sensitive element. Due to the inherent positive temperature coefficient of its material, its resistance value changes with the seawater temperature. By measuring the resistance signal of the metal coil 54, the seawater temperature can be calculated.

[0066] To verify the feasibility of the flow velocity and direction sensing principle under laboratory conditions, this invention underwent a mechanical simulation test. A custom-designed fixture was used to apply forces of different directions and magnitudes to the hemisphere of the multimodal sensor to simulate the impact of water flow from different directions. Figure 8 As shown, the triangular mold is used with the triangular pressure head, and its angle θ represents the direction of pressure application.

[0067] First, flow velocity simulation. Combined with... Figure 9 As shown, with a fixed direction of application (angles θ of 30°, 45°, 60°, and 90°), the capacitance-pressure variation curves were obtained by gradually increasing the applied force. Experimental data show that the attenuation amplitude of the capacitance signal output by each sensing unit in the flow velocity and direction detection zone has a good monotonic relationship with the magnitude of the applied force.

[0068] Next is the flow simulation. Combined with... Figure 10 As shown, with a fixed force magnitude (3N), the direction of the force is changed. Experimental data indicate that sensing units at different spatial locations in the flow velocity and direction detection zone exhibit differentiated capacitive response modes (see...). Figure 8 (Heat map). This pattern has a clear and repeatable correspondence with the direction of the force.

[0069] Specifically, when the force acts perpendicularly to the apex of the hemisphere, i.e., only the normal force exists, all sensing units respond uniformly. However, when the force is inclined, it can be decomposed into normal and tangential forces, resulting in an asymmetric response distribution. These results fully verify the feasibility of the hemispherical structure in converting directional mechanical input into a measurable spatial electrical distribution pattern.

[0070] To further verify the sensor's performance in a real water flow environment, it was tested in a circulating water tank. The experiment controlled the flow rate by changing the water pump power and altered the flow direction by adjusting the sensor orientation or the water flow guide, as shown in Figure 11.

[0071] Combination Figures 12 to 14 As shown, the test results indicate that under different steady flow velocities and flow directions, each sensing unit in the velocity and direction detection area produces a significant response. Specifically, under a fixed flow velocity, the relative strength distribution pattern of the capacitance signals of each sensing unit corresponds one-to-one with the flow direction. Under a fixed flow direction, the overall variation amplitude of the capacitance signals of each sensing unit is related to the flow velocity. Therefore, this water tank experiment demonstrates that the multimodal sensor of this invention can effectively sense and distinguish flow velocity and direction in a real underwater environment.

[0072] To verify the depth sensing function, a multimodal sensor was placed in water, and hydrostatic pressures corresponding to different water depths were applied to the depth detection area using a force gauge (M5-10, Mark-10). The resistance signal output from electrode 52 in the depth detection area was acquired using an LCR meter, resulting in a resistance-pressure change curve reflecting changes in water depth. Figure 15 As shown, the resistance gradually decreases with increasing water depth, thus enabling depth sensing.

[0073] To verify the salinity sensing function, the multimodal sensor was placed in water, and NaCl was added to artificially adjust the sodium and chloride ion content, thus controlling the salinity. In the salinity detection area, electrode 53 is in direct contact with the water. The capacitance signal output by electrode 53 can be collected using LCR to obtain capacitance-salinity change curves at different salinities (1%-5% NaCl solution). Figure 16 As shown, the capacitance gradually increases with increasing salinity, thus enabling salinity sensing.

[0074] To verify the temperature sensing function, a multimodal sensor was placed in a temperature-controlled water bath, and the temperature was manually adjusted. The temperature was gradually increased from 20℃ to 90℃, and the resistance signal output from the temperature detection area was collected using an LCR sensor to obtain a resistance-temperature change curve reflecting the water temperature. Figure 17 As shown, as the water temperature rises, the resistance of the metal coil 54 gradually increases, thereby achieving temperature sensing.

[0075] In summary, the multimodal sensor exhibits good monotonicity and linearity in sensing depth, temperature, and salinity, demonstrating excellent computational and calibration potential. This invention, through a miniaturized design with multi-parameter fusion, achieves independent, accurate, and integrated sensing of temperature, salinity, depth, flow velocity, and flow direction while maintaining pressure resistance and size advantages, providing a precise and reliable new solution for marine environmental monitoring.

[0076] Finally, it should be noted that although the embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art, guided by this specification, can make many other forms without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A multimodal sensing integrated sensor for underwater environments, characterized in that, include: A hemisphere, consisting of a spherical surface and a base; A coplanar electrode includes a substrate, a first electrode formed on the substrate, and at least one of a second electrode, a third electrode, and a temperature-sensitive element formed on the substrate, wherein the first electrode, the second electrode, and the third electrode are all single-sided electrodes; An elastomer membrane is sandwiched between the bottom surface of a hemisphere and a coplanar electrode, with one side being a smooth surface and the other side being a micro-rough surface. An open housing includes a receiving cavity and a top surface perforation area and a side through area connected to the receiving cavity; the open housing is further configured to pass through the spherical surface of a hemisphere through its top surface perforation area, so that the bottom surface of the hemisphere is arranged in the receiving cavity in direct correspondence with the first electrode through an elastomer membrane, and the receiving cavity is connected to the external environment through its side through area, so as to form a reverse ionization sensing interface at the interface where the micro-rough surface of the elastomer membrane contacts the first electrode, which can change the number of mobile ions at the interface in response to the pressure on the hemisphere. The first electrode is also configured to output an electrical signal based on a reverse ionization sensing mechanism, the electrical signal being negatively correlated with the pressure change applied to the hemisphere, for sensing flow velocity and direction; the second electrode is also configured to output an electrical signal for sensing water depth; the third electrode is also configured to output an electrical signal for sensing salinity; and the temperature-sensitive element is also configured to output an electrical signal for sensing temperature.

2. The multimodal sensing integrated sensor as described in claim 1, characterized in that, The surface of the second electrode is covered with a conductive carbon film, which outputs an electrical signal based on the piezoresistive sensing mechanism. The electrical signal is negatively correlated with the hydrostatic pressure acting on the surface of the second electrode. The third electrode is configured to be directly exposed to the water body during use, and it outputs an electrical signal based on the ionization sensing mechanism, which is positively correlated with the salinity of the water body. The temperature-sensitive element is configured to output an electrical signal based on the resistance thermal effect, and the electrical signal is positively correlated with the temperature of the water body.

3. The multimodal sensing integrated sensor as described in claim 2, characterized in that, The single-sided electrode is an interdigitated electrode; the temperature-sensitive element is a metal coil made of platinum or nickel.

4. The multimodal sensing integrated sensor as described in any one of claims 1 to 3, characterized in that, The first electrode comprises multiple independent and identical electrode units, which are distributed in a rotationally symmetrical manner with the projection point of the center of the bottom surface of the hemisphere as the center.

5. The multimodal sensing integrated sensor as described in any one of claims 1 to 3, characterized in that, The second electrode, the third electrode, and the temperature-sensitive element are arranged adjacent to the first electrode, and the external wires of the first electrode, the second electrode, the third electrode, and the temperature-sensitive element are all led out from the same position and in the same direction.

6. The multimodal sensing integrated sensor as described in any one of claims 1 to 3, characterized in that, The micro-rough surface of the elastomer membrane is configured to have any one of the following: a micro-rough structure, a porous structure, or an array of micro-protrusions.

7. The multimodal sensing integrated sensor as described in any one of claims 1 to 3, characterized in that, The hemisphere also includes a base fixedly connected to its bottom surface; the shape of the base matches the shape of the first electrode to achieve force transmission and shape matching from the bottom surface of the hemisphere to the elastomer membrane.

8. The multimodal sensing integrated sensor as described in any one of claims 1 to 3, characterized in that, It also includes a pre-tightening element; the pre-tightening element is configured to have a circular hollow area with a diameter that matches the diameter of the bottom surface of the hemisphere; the pre-tightening element passes through the circular hollow area through the spherical surface of the hemisphere and is sandwiched between the open shell and the elastomer membrane, for applying pre-tightening pressure to the elastomer membrane.

9. The multimodal sensing integrated sensor as described in any one of claims 1 to 3, characterized in that, The hemisphere is a rigid material with an elastic modulus of 2-30 GPa, including one or a combination of nylon, polylactic acid, acrylic acid, epoxy resin, and polycarbonate; the substrate is a flexible substrate, and its material is polyimide or fluoropolymer; the material of the elastomer film is any one of polydimethylsiloxane, polyurethane, polyimide, thermoplastic polyurethane, and rubber.

10. The flow velocity and direction sensor as described in any one of claims 1 to 3, characterized in that, The top surface of the open shell has a circular or regular polygonal cutout area; the open shell has two or more support columns, and a side through area is formed between adjacent support columns.

Images