High-sensitivity underwater flexible touch sensor and pressure detection method

Abstract

The invention discloses a high-sensitivity underwater flexible touch sensor and a pressure detection method. The sensor comprises a top porous boss layer, an upper interlocking layer, a middle layer and a lower interlocking layer which are sequentially and coaxially arranged from top to bottom. A closed cavity is formed between the upper interlocking layer and the lower interlocking layer, the cavity is filled with insulating hydraulic oil, the upper interlocking layer is provided with an upper-layer interlocking microstructure, the lower interlocking layer is provided with a lower-layer interlocking microstructure, and the upper-layer interlocking microstructure, the lower-layer interlocking microstructure and the middle layer are all located in the cavity; the middle layer comprises a middle layer flexible substrate, and a sensitive material and a flexible electrode which are arranged above the middle layer flexible substrate, and the sensitive material adopts a patterning design and is electrically connected with the flexible electrode; according to the method, the water pressure is compensated in the aspects of structure and data processing, and high-precision pressure values can be output under different water pressures. According to the underwater flexible touch sensor, high-sensitivity and low-interference detection of the contact force can be realized when the underwater flexible touch sensor works in different depth environments.

Description

Technical Field

[0001] The invention relates to a flexible tactile sensor in the field of underwater contact force detection, and in particular to a highly sensitive underwater flexible tactile sensor and a pressure detection method. Background Art

[0002] Marine resources are abundant and vast, and the demand for related scientific research, marine exploration, and aquatic life detection activities is increasing day by day. Among them, sensing various information from the water environment is crucial for underwater activities. However, existing underwater sensing technologies rely heavily on acoustic and optical detection equipment, which are easily restricted by complex aquatic environments, such as turbidity and brightness, and lack the ability to detect contact forces generated during underwater operations, which greatly restricts the development of my country's underwater intelligent equipment and marine resource exploration. Flexible sensors with excellent force detection capabilities have been widely used in many fields under the ground environment, such as intelligent robots, human-computer interaction, wearable devices, etc. Introducing the emerging flexible tactile sensor technology into the underwater environment is expected to overcome the above limitations and meet the needs of underwater force sensing.

[0003] However, due to a series of obstacles caused by the underwater environment, the current underwater sensing technology is still very limited. Among them, the technical challenge that needs to be solved urgently is how to compensate for the water pressure that increases with the depth of the water. Chinese patent CN115752871A uses an open structure to use the self-balance of water to offset the water pressure, but water is conductive, especially seawater, so the sensor will lose some of its sensing performance or even short-circuit. Chinese CN117158953A first detects the water pressure signal and then uses numerical calculation to compensate for the water pressure, but the additional water pressure measurement sensor increases the complexity of the equipment, and the water pressure is only compensated by data processing rather than directly offset by structural design. When the water pressure acts on the sensor surface, the sensitivity and range of the sensor are reduced. Summary of the invention

[0004] In order to solve the problems existing in the background technology, the present invention provides a highly sensitive underwater flexible tactile sensor and a pressure detection method, which can realize automatic compensation of different underwater pressures and highly sensitive detection of a large range of underwater tactile forces.

[0005] The technical solution adopted by the present invention is:

[0006] 1. A highly sensitive underwater flexible tactile sensor

[0007] The sensor includes a top porous boss layer, an upper interlocking layer, an intermediate layer and a lower interlocking layer which are coaxially arranged from top to bottom; a closed cavity is formed between the upper interlocking layer and the lower interlocking layer, and the cavity is filled with insulating hydraulic oil, and the insulating hydraulic oil is used to offset the water pressure changes in the outside world. An upper interlocking microstructure is provided at the bottom of the upper interlocking layer, and a lower interlocking microstructure is provided at the top of the lower interlocking layer. The upper interlocking microstructure, the lower interlocking microstructure and the intermediate layer are all located in the cavity. The intermediate layer includes an intermediate layer flexible substrate and a sensitive material and a flexible electrode arranged above the intermediate layer flexible substrate. The sensitive material adopts a patterned design and is electrically connected to the flexible electrode. The pattern of the sensitive material is a sensitive area in the arrangement area of ​​the intermediate layer flexible substrate. The upper interlocking microstructure is in contact with the top surface portion of the sensitive area of ​​the intermediate layer flexible substrate, and the lower interlocking microstructure is in contact with the bottom surface portion of the sensitive area of ​​the intermediate layer flexible substrate.

[0008] When the sensor does not bear an external load, the bottom surface of the upper interlocking microstructure is arranged in contact with the top surface of the middle layer, and the top surface of the lower interlocking microstructure is arranged in contact with the bottom surface of the middle layer. Under an external load, the upper interlocking layer and the lower interlocking layer squeeze the middle layer, while the upper interlocking microstructure and the lower interlocking microstructure form an interlocking structure to stretch the sensitive material and deform it. The resistance of the sensitive material changes with its own deformation, and the electrical signal output by the flexible electrode changes accordingly.

[0009] Furthermore, in order to improve the stability of the sensor, the contact positions of the upper interlocking microstructure and the lower interlocking microstructure with the intermediate flexible substrate can be fixedly connected by bonding or plasma treatment.

[0010] The upper interlocking microstructure and the lower interlocking microstructure respectively include a plurality of upper interlocking micro-boss arrays and a plurality of lower interlocking micro-boss arrays of the same number, and the upper interlocking micro-boss array and the lower interlocking micro-boss array are respectively evenly distributed along the circumference of the upper interlocking layer and the lower interlocking layer, and each upper interlocking micro-boss array / lower interlocking micro-boss array includes at least two upper interlocking micro-bosses / lower interlocking micro-bosses, and the upper interlocking micro-bosses / lower interlocking micro-bosses are arranged at equal intervals from the inside to the outside in the radial direction.

[0011] There is a corresponding lower interlocking micro-boss array arranged directly below each upper interlocking micro-boss array. For a corresponding group of upper interlocking micro-boss arrays and lower interlocking micro-boss arrays, the shape of the upper interlocking micro-boss is adapted to the shape of the lower interlocking micro-boss, and the upper interlocking micro-boss and the lower interlocking micro-boss are staggered in the radial direction (arrangement direction) and can be interlocked with each other. Specifically, the mutual interlocking means that in the same upper interlocking micro-boss array / lower interlocking micro-boss array, a micro-groove is formed between two adjacent upper interlocking micro-bosses / lower interlocking micro-bosses, and when the upper interlocking layer and the lower interlocking layer are pressed together under the action of an external load force, the upper interlocking micro-boss in the upper interlocking micro-boss array can be embedded in the micro-groove in the corresponding lower interlocking micro-boss array. When the sensor bears an external load force, the upper interlocking microstructure squeezes the middle layer downward, and each upper interlocking micro-boss is pressed into the micro-groove in the corresponding lower interlocking micro-boss array. The staggered arrangement means that the projections of the upper interlocking micro-bosses and the lower interlocking micro-bosses on the same horizontal plane are staggered in the radial direction.

[0012] Correspondingly, the pattern of the sensitive material is set as a continuous curved pattern, and the curved pattern is formed by connecting two symmetrical serpentine line patterns, and the symmetry axis is any two upper interlocking micro-convex platform arrays or their corresponding lower interlocking micro-convex platform arrays spaced at a central angle of 180°, and one end of each of the two serpentine line patterns is connected, and the connection point of the two serpentine line patterns is located at the common center of the upper interlocking layer and the lower interlocking layer, and the ends of the other ends of each of the two serpentine line patterns are respectively arranged on both sides of the symmetry axis, and are both located at the edge of the top surface of the intermediate layer flexible substrate, and the two The ends of the serpentine line pattern are electrically connected to the positive electrode and the negative electrode in the flexible electrode respectively; each serpentine line pattern includes a number of arc patterns that are evenly arranged along the radial direction and connected end to end, and the number of the arc patterns is the same as the number of upper interlocking micro-bosses / lower interlocking micro-bosses in each upper interlocking micro-boss array / lower interlocking micro-boss array, and the common center of all the arc patterns is the connection point of the two serpentine line patterns, and each arc pattern passes alternately from the bottom of the corresponding upper interlocking micro-boss and the top of the corresponding lower interlocking micro-boss in turn.

[0013] Preferably, all arc patterns are formed by connecting a number of U-shaped patterns end to end to form a continuous serpentine line.

[0014] Preferably, the upper interlocking micro-boss array includes four first upper interlocking micro-boss arrays and four second upper interlocking micro-boss arrays, and the lower interlocking micro-boss array includes four first lower interlocking micro-boss arrays and four second lower interlocking micro-boss arrays, and the number of upper interlocking micro-boss / lower interlocking micro-boss in each upper interlocking micro-boss array / lower interlocking micro-boss array is three. The first upper interlocking micro-boss array, the second upper interlocking micro-boss array, the first lower interlocking micro-boss array, and the second lower interlocking micro-boss array are uniformly arranged along the circumferential direction, that is, two adjacent first upper interlocking micro-boss arrays, two adjacent second upper interlocking micro-boss arrays, two adjacent first lower interlocking micro-boss arrays, and two adjacent second lower interlocking micro-boss arrays are spaced at a central angle of 90°. In the first upper interlocking micro-boss array and the first lower interlocking micro-boss array, the shape of the upper interlocking micro-boss is adapted to the shape of the lower interlocking micro-boss; in the second upper interlocking micro-boss array and the second lower interlocking micro-boss array, the shape of the upper interlocking micro-boss is adapted to the shape of the lower interlocking micro-boss. The second upper interlocking micro-boss array and the first lower interlocking micro-boss array form a primary interlock in the circumferential direction of the sensitive material; the first upper interlocking micro-boss array and the first lower interlocking micro-boss array, the second upper interlocking micro-boss array and the second lower interlocking micro-boss array form a secondary interlock in the diameter direction of the sensitive material.

[0015] Correspondingly, the axis of symmetry of the curved pattern is two first upper interlocking micro-boss arrays spaced 180° apart at a central angle, and the several arc patterns include a first arc pattern, a second arc pattern and a third arc pattern arranged in sequence from outside to inside in the radial direction, the starting end of the first arc pattern is the end of the serpentine line pattern, and the end of the third arc pattern extends to the connection point through a U-shaped pattern; the first arc pattern passes in sequence under an outermost upper interlocking micro-boss of the second upper interlocking micro-boss array, above an outermost lower interlocking micro-boss of the first lower interlocking micro-boss array, and under an outermost upper interlocking micro-boss of the second upper interlocking micro-boss array; the second arc pattern and the third arc pattern are arranged in coordination with the second upper interlocking micro-boss array, the first lower interlocking micro-boss array and the second upper interlocking micro-boss array in the same pattern as the first arc pattern. The arrangement of the second arc pattern and the third arc pattern is specifically as follows: the second arc pattern passes sequentially from under the middle upper interlocking micro-boss of the second upper interlocking micro-boss array, above the middle lower interlocking micro-boss of the first lower interlocking micro-boss array, and under the middle upper interlocking micro-boss of the second upper interlocking micro-boss array; the third arc pattern passes sequentially from under the innermost upper interlocking micro-boss of the second upper interlocking micro-boss array, above the innermost lower interlocking micro-boss of the first lower interlocking micro-boss array, and under the innermost upper interlocking micro-boss of the second upper interlocking micro-boss array.

[0016] The upper interlocking micro-bosses / lower interlocking micro-bosses in the same upper interlocking micro-boss array / lower interlocking micro-boss array have the same shape, which can be a geometric shape such as a cylinder, a cone, a wedge, a prism, and a prism, so as to achieve the best interlocking effect between the two layers of platforms.

[0017] Preferably, the micro-protrusions realize interlocking between the upper interlocking layer and the lower interlocking layer through wedge-shaped matching. The corresponding shapes are respectively a first wedge-shaped body and a second wedge-shaped body, and the geometric gradient of the first wedge-shaped body is opposite to the geometric gradient of the second wedge-shaped body.

[0018] Preferably, since the bottom surface of the upper interlocking micro-boss in the second upper interlocking micro-boss array contacts the sensitive area, in order to improve the sensitivity, its area is larger than the bottom surface area of ​​the upper interlocking micro-boss in the first upper interlocking micro-boss array. Similarly, the bottom surface area of ​​the lower interlocking micro-boss in the first lower interlocking micro-boss array is larger than the bottom surface area of ​​the lower interlocking micro-boss in the second lower interlocking micro-boss array. The sensitive area is the arrangement area of ​​the sensitive material.

[0019] The upper interlocking layer also includes an upper annular water pressure compensation chamber and an upper flexible substrate, the top surface of the upper flexible substrate is bonded with a top porous boss layer, and the bottom surface of the top porous boss layer is tightly fitted with the top surface of the upper flexible substrate, the bottom surface of the upper flexible substrate is bonded with an upper interlocking microstructure, the bottom end of the upper interlocking microstructure is in contact with the middle layer, the outer edge of the upper flexible substrate extends downward along its own axis to form an upper side portion, the upper flexible substrate is arranged on the inner side of the upper annular water pressure compensation chamber, the main body of the upper annular water pressure compensation chamber is an annular main body with a certain height, the inner ring edge of the top of the annular main body (upper annular water pressure compensation chamber main body) extends radially inward and forms an upper annular connecting portion, the inner wall surface of the upper annular connecting portion is connected to the outer peripheral surface of the upper flexible substrate, specifically, the inner wall surface of the upper annular connecting portion is bonded to the outer peripheral surface of the top of the upper flexible substrate.

[0020] The lower interlocking layer also includes a lower annular water pressure compensation chamber and a lower flexible substrate, the top surface of the lower flexible substrate is bonded with a lower interlocking microstructure, the top of the lower interlocking microstructure is in contact with the middle layer, the outer edge of the lower flexible substrate extends upward along its own axis to form a lower side portion, and the lower flexible substrate is arranged on the inner side of the lower annular water pressure compensation chamber; the main body of the lower annular water pressure compensation chamber is an annular main body with a certain height, the inner ring edge of the bottom of the annular main body (lower annular water pressure compensation chamber main body) extends radially inward and forms a lower annular connecting portion, the inner wall surface of the lower annular connecting portion is connected to the outer peripheral surface of the lower flexible substrate, specifically, the inner wall surface of the lower annular connecting portion is bonded to the outer peripheral surface of the top of the lower flexible substrate.

[0021] The upper annular connecting part and the lower annular connecting part are aligned and bonded to form the cavity. Specifically, the bottom surface of the upper annular connecting part and the top surface of the lower annular connecting part are bonded and connected.

[0022] Multiple openings are provided on the outer circumferential surfaces of the upper side portion and the lower side portion, and the openings are all opened radially, so that the bottom end surface of the upper side portion and the top end surface of the lower side portion are aligned up and down and then bonded to form an inner cavity connected to the cavity, and the insulating hydraulic oil can partially flow into or partially flow out of the inner cavity under different water pressures to compensate for the water pressure.

[0023] The upper flexible substrate and the lower flexible substrate are both made of a first flexible material, the upper annular water pressure compensation chamber and the lower annular water pressure compensation chamber are both made of a second flexible material, and the Young's modulus of the first flexible material is greater than that of the second flexible material.

[0024] Preferably, the higher the ratio of the Young's modulus of the first flexible material to the Young's modulus of the second flexible material, the more obvious the water pressure compensation effect. As an optional embodiment of the present invention, the upper annular water pressure compensation chamber and the lower annular water pressure compensation chamber are made of copolyester (Exoflex) with low Young's modulus; the upper flexible substrate and the lower flexible substrate are made of PDMS with high Young's modulus.

[0025] Furthermore, the upper flexible substrate, the upper interlocking microstructure, the lower interlocking microstructure and the lower flexible substrate can all be obtained by integrated manufacturing. For example, the integrated manufacturing can be performed by injecting uncured material into the mold, heating and curing, and demolding. The mold can be manufactured by 3D printing.

[0026] Preferably, the thickness of the upper annular connecting portion and the lower annular connecting portion is less than the thickness of the upper flexible substrate and the lower flexible substrate. The axial height of the upper annular water pressure compensation chamber is the same as the axial height of the upper flexible substrate. The top surface of the upper annular water pressure compensation chamber is flush with the top surface of the upper flexible substrate.

[0027] The top porous boss layer is used to bear the external load force and improve the sensor's resistance to underwater disturbances. The top porous boss layer is arranged on the top surface of the upper interlocking layer. In the present invention, the external load force is a normal force, that is, a force applied from top to bottom. The top porous boss layer is prepared by mixing polydimethylsiloxane (PDMS) with sodium chloride particles (NaCl), curing them, and washing them with water. NaCl dissolves to form internal pores that are interconnected. Among them, the particle size of the NaCl particles is 50μm. The mass ratio of polydimethylsiloxane to sodium chloride particles is preferably 2 to 5:1. The lower the mass ratio, the more pores there are, the stronger the water flow resistance is, and the weaker the force conduction ability is.

[0028] The flexible electrode includes a positive electrode and a negative electrode. The flexible electrode is connected to an external detection circuit to detect the resistance change of the sensitive material, thereby obtaining the contact force information of the sensor under water.

[0029] 2. A pressure detection method using the above-mentioned highly sensitive underwater flexible tactile sensor

[0030] The steps of the pressure detection method are specifically as follows:

[0031] S1) Install the sensor at a preset position underwater. At this time, the sensor is not subjected to external load force. The upper annular water pressure compensation chamber and the lower annular water pressure compensation chamber automatically adjust the degree of inward contraction according to the change of external water pressure. Part of the insulating hydraulic oil flows into the inner cavity to balance the water pressure, thereby compensating the water pressure once in the structure.

[0032] S2) When the sensor is subjected to an external load force, the upper annular water pressure compensation chamber and the lower annular water pressure compensation chamber expand outward, and part of the insulating hydraulic oil flows out of the inner cavity to prevent the sensor from exploding; the external load force squeezes the upper interlocking layer downward, and the upper interlocking layer and the lower interlocking layer are pressed together, so that the upper interlocking microstructure and the lower interlocking microstructure form an interlocking positioning structure and stretch the sensitive material, and the resistance of the sensitive material changes with its own deformation, and the output electrical signal of the flexible electrode also changes accordingly; the interlocking positioning structure is: the second upper interlocking micro-boss array and the first lower interlocking micro-boss array form a primary interlock in the circumferential direction of the sensitive material; the first upper interlocking micro-boss array and the first lower interlocking micro-boss array, the second upper interlocking micro-boss array and the second lower interlocking micro-boss array form a secondary interlock in the diameter direction of the sensitive material.

[0033] S3) Use back propagation (BP) neural network to perform secondary compensation for water pressure in data processing: an external controller receives the output electrical signal of the flexible electrode in real time, and inputs it into a pre-trained back propagation (BP) neural network model for processing, and the back propagation neural network model outputs the compensated pressure value.

[0034] S4) After the external load force is unloaded, the upper annular water pressure compensation chamber and the lower annular water pressure compensation chamber rebound inward, the acceleration sensor returns to its initial state, and the resistance of the sensitive material and the output electrical signal of the flexible electrode return to their initial values.

[0035] The present invention has the following beneficial effects:

[0036] 1) The upper and lower annular water pressure compensation chambers are made of Exoflex material with low Young's modulus and thin wall thickness, so they shrink inward first under the action of water pressure; the upper and lower flexible substrates are made of PDMS material with high Young's modulus and thick wall thickness, so they shrink inward slowly and to a small extent. The relative positions of the sensor layers remain stable, and the sensitive material does not produce obvious force signal output when only under the action of water pressure.

[0037] 2) The internal holes of the top porous boss layer are interconnected, and external water can freely enter and fill the top porous boss layer to prevent it from being compressed under water pressure, so as to maintain the force conduction performance of the top porous boss; in addition, when the underwater ocean current acts on the top porous boss layer, the ocean current is dispersed by the porous structure to improve the sensor's resistance to underwater disturbances and realize the sensor's detection of tiny underwater forces.

[0038] 3) The upper and lower annular water pressure compensation chambers balance the water pressure by contracting inward when only water pressure acts, and expand outward when external load acts to prevent the sensor from being squeezed and exploded by the insulating hydraulic oil. In addition, after unloading the external load, the annular water pressure compensation chamber recovers under the rebound force of the material, and the upper and lower annular water pressure compensation chambers push the insulating hydraulic oil inward, which accelerates the upper and lower interlocking layers to return to their initial state. Therefore, the sensor has a smaller hysteresis effect and a faster recovery time.

[0039] 4) The upper and lower interlocking microstructures form two-level interlocking in the circumferential direction and the diameter direction of the sensitive material, respectively, so that the sensitive material is bidirectionally stretched, so the sensitivity of the sensor is higher.

[0040] 5) The annular water pressure compensation chamber compensates for the water pressure once in its structure, and the force detection performance of the sensor does not decrease significantly under the action of water pressure; the BP neural network compensates for the water pressure twice in data processing, and the structural compensation is combined with the numerical compensation. The sensor maintains high-precision and high-sensitivity force detection capabilities under different water pressures. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a disassembled stereogram of the layered structure of the underwater flexible sensor of the present invention;

[0042] Figure 2 is a cross-sectional view of the underwater flexible sensor of the present invention;

[0043] Figure 3 1. are a front view and a top view of the porous boss layer on the top of the underwater flexible sensor of the present invention;

[0044] Figure 4 is a bottom view of the upper interlocking layer and a top view of the lower interlocking layer of the underwater flexible sensor of the present invention;

[0045] Figure 5(a) is a three-dimensional diagram of the structure of the interlocking microstructures of the upper and lower layers and the middle layer. Figure 5 (b) is a top view of the interlocking microstructures of the upper and lower layers and the structure of the middle layer. Figure 5 (c) is a schematic diagram of the primary interlocking in the circumferential direction. Figure 5 (d) is a schematic diagram of the secondary interlocking in the diameter direction.

[0046] Figure 6 It is a diagram of the deformation and strain simulation results of the underwater flexible sensor of the present invention under different water pressures;

[0047] Figure 7 It is a diagram showing the deformation and strain simulation results of the underwater flexible sensor of the present invention under the same water pressure and different external load forces;

[0048] Figure 8 It is a BP neural network model diagram adopted by the underwater flexible sensor of the present invention;

[0049] Fig. 9 It is a manufacturing flow chart of the underwater flexible sensor of the present invention.

[0050] In the figure: 1. Top porous boss layer; 2. Upper interlocking layer; 3. Middle layer; 4. Lower interlocking layer; 5. Upper annular water pressure compensation chamber; 6. Upper flexible substrate; 7. Upper interlocking microstructure; 8. Sensitive material; 9. Flexible electrode; 10. Middle layer flexible substrate; 11. Lower interlocking microstructure; 12. Lower flexible substrate; 13. Lower annular water pressure compensation chamber; 14. Insulating hydraulic oil; 7-A. First upper interlocking micro-boss array; 7-B. Second upper interlocking micro-boss array; 11-A. First lower interlocking micro-boss array; 11-B. Second lower interlocking micro-boss array. DETAILED DESCRIPTION

[0051] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0052] like Figure 1 and Figure 2 As shown, the underwater flexible tactile sensor proposed by the present invention comprises a top porous boss layer 1, an upper interlocking layer 2, an intermediate layer 3, and a lower interlocking layer 4, wherein the top porous boss layer 1, the upper interlocking layer 2, the intermediate layer 3, and the lower interlocking layer 4 are stacked in sequence from top to bottom. The sensor is generally a cylindrical structure with a maximum diameter of 15 mm and a height of 4 mm.

[0053] The upper interlocking layer 2 is mainly composed of an upper annular water pressure compensation chamber 5, an upper flexible substrate 6 and an upper interlocking microstructure 7, the bottom surface of the top porous boss layer 1 is tightly fitted with the top surface of the upper flexible substrate 6, and the outer peripheral surface of the top of the upper flexible substrate 6 is tightly bonded with the inner wall surface of the top of the upper annular water pressure compensation chamber 5. The height of the upper annular water pressure compensation chamber 5 and the upper flexible substrate 6 are both 1 mm, and the top surfaces of the two overlap and are on the same horizontal plane.

[0054] The middle layer 3 is mainly composed of a sensitive material 8, a flexible electrode 9 and a middle layer flexible substrate 10 stacked in sequence from top to bottom. The pins at both ends of the sensitive material 8 are respectively connected to the flexible electrode 9, and the flexible electrode 9 is connected to an external detection circuit to detect the resistance change of the sensitive material 8, and then obtain the contact force information of the sensor under water. The thickness of the sensitive material 8, the flexible electrode 9 and the middle layer flexible substrate 10 are all 0.1mm. The flexible electrode 9 includes a positive electrode and a negative electrode.

[0055] The lower interlocking layer 4 is mainly composed of a lower interlocking microstructure 11, a lower flexible substrate 12 and a lower annular water pressure compensation chamber 13. The outer peripheral surface of the bottom end of the lower flexible substrate 12 is tightly bonded to the inner wall surface of the bottom end of the lower annular water pressure compensation chamber 13. The height of the lower annular water pressure compensation chamber 13 and the lower flexible substrate 12 are both 1 mm, and the bottom surfaces of the two overlap and are on the same horizontal plane.

[0056] The upper interlocking layer 2 and the lower interlocking layer 4 are arranged opposite each other and fit tightly to form an enclosed cavity, which is completely filled with insulating hydraulic oil 14. At different depths underwater, the insulating hydraulic oil 14 is compressed and contracted, and the pressure increases to offset the changing water pressure of the outside world; the upper interlocking microstructure 7 and the lower interlocking microstructure 11 form an interlocking positioning structure. Under the external load force, the upper interlocking microstructure 7 and the lower interlocking microstructure 11 respectively squeeze the middle layer flexible substrate 10 and then stretch the sensitive material 8, so that the output resistance signal of the sensitive material 8 changes.

[0057] like Figure 1 and Figure 4 As shown, the upper interlocking microstructure 7 is mainly composed of the first upper interlocking micro-boss array 7-A and the second upper interlocking micro-boss array 7-B; the lower interlocking microstructure 11 is mainly composed of the first lower interlocking micro-boss array 11-A and the second lower interlocking micro-boss array 11-B, and the upper interlocking microstructure 7 and the lower interlocking microstructure 11 are arranged vertically opposite each other. Among them, the first upper interlocking micro-boss array 7-A and the second upper interlocking micro-boss array 7-B are arranged at an angle of 45° on the inner bottom surface of the upper flexible substrate 6, and the first lower interlocking micro-boss array 11-A and the second lower interlocking micro-boss array 11-B are arranged at an angle of 45° on the inner bottom surface of the lower flexible substrate 12.

[0058] like Figure 4 and Figure 5As shown, the shape of the micro-bosses is a wedge-shaped body, and the side with a larger area (such as the top surface of the upper interlocking micro-boss and the bottom surface of the lower interlocking micro-boss) of the wedge-shaped body is used for bonding and connecting with the upper flexible substrate 6 or the lower flexible substrate 12, and the side with a smaller area (such as the bottom surface of the upper interlocking micro-boss and the top surface of the lower interlocking micro-boss) is used for contacting with the middle flexible substrate 10. In addition, the bottom surface area of ​​the upper interlocking micro-boss in the second upper interlocking micro-boss array 7-B is larger than the bottom surface area of ​​the upper interlocking micro-boss in the first upper interlocking micro-boss array 7-A. The top surface area of ​​the lower interlocking micro-boss in the first lower interlocking micro-boss array 11-A is larger than the top surface area of ​​the lower interlocking micro-boss in the second lower interlocking micro-boss array 11-B.

[0059] like Figure 5 As shown, the upper interlocking microstructure 7 and the lower interlocking microstructure 11 form a two-level interlocking, wherein the second upper interlocking micro-boss array 7-B and the first lower interlocking micro-boss array 11-A form a primary interlocking in the circumferential direction of the sensitive material 8; the first upper interlocking micro-boss array 7-A and the first lower interlocking micro-boss 7-B, the second upper interlocking micro-boss 11-A and the second lower interlocking micro-boss array 11-B form a secondary interlocking in the diameter direction of the sensitive material 8. The two-level interlocking causes the sensitive material 8 to produce bidirectional stretching, and the sensor sensitivity is higher.

[0060] like Figure 1 and Figure 4 As shown, four windows are respectively opened on the outer circumference of the upper flexible substrate 6 and the lower flexible substrate 12, which are connected to the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 11, and each window is 2 mm long and 0.6 mm high. The insulating hydraulic oil 14 flows freely in the cavity formed between the upper interlocking layer 2 and the lower interlocking layer 3.

[0061] like Figure 3 As shown, the top porous boss layer 1 is made of PDMS mixed with NaCl particles. The top porous boss layer 1 is immersed in water, and NaCl is completely dissolved to form internal holes that are interconnected. Therefore, the internal holes of the top porous boss layer 1 are interconnected, and external water can freely enter and fill the top porous boss layer 1 to prevent it from being compressed under water pressure, so as to maintain the force conduction performance of the top porous boss 1; in addition, when the underwater ocean current acts on the top porous boss layer 1, the ocean current is dispersed by the porous structure to improve the sensor's resistance to underwater disturbances and realize the sensor's detection of underwater micro-forces. Among them, the top porous boss layer 1 is a truncated cone shape as a whole, with a height of 2mm, a maximum bottom diameter of 10mm, and a minimum top diameter of 5mm.

[0062] like Figure 2 and Figure 4As shown, the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 13 are made of Exoflex with low Young's modulus, and the upper flexible substrate 6 and the lower flexible substrate 12 are made of PDMS with high Young's modulus. Exoflex with low Young's modulus is easier to deform when subjected to the same pressure than PDMS with high Young's modulus.

[0063] The thickness of the upper annular hydraulic pressure compensation chamber 5 and the lower annular hydraulic pressure compensation chamber 13 is smaller than that of the upper flexible substrate 6 and the lower flexible substrate 12. Specifically, the overall wall thickness of the upper annular hydraulic pressure compensation chamber 5 is 0.2 mm, the bottom wall thickness of the upper flexible substrate 6 is 0.4 mm, and the side support wall (upper side) is 1 mm thick; the overall wall thickness of the lower annular hydraulic pressure compensation chamber 13 is 0.2 mm, the bottom wall thickness of the lower flexible substrate 12 is 0.4 mm, and the side support wall (lower side) is 1 mm thick. The smaller the wall thickness, the easier it is for the structure to deform.

[0064] The water pressure compensation method of the underwater flexible tactile sensor of the present invention is as follows:

[0065] like Figure 6 As shown, when the sensor is not subjected to external load force, the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 13 automatically adjust the degree of inward contraction to compensate for the water pressure according to the change of external water pressure. The simulation results show that as the underwater pressure increases, the deformation and strain of the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 13 increase significantly, and the positions of the upper flexible substrate 6 and the lower flexible substrate 12 remain stable without obvious deformation and strain. Therefore, the resistance value of the sensitive material 8 does not change significantly, that is, there is no significant force response output, and the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 13 have excellent water pressure self-compensation effect.

[0066] like Figure 7 As shown in the figure, when the sensor is subjected to an external load force, the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 13 expand outward to allow the insulating hydraulic oil 14 to flow, thereby preventing the sensor from exploding. The simulation results show that under the same water pressure, as the external load force on the sensor increases, the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 13 gradually expand outward to provide a larger space for the insulating hydraulic oil 14 to flow.

[0067] After unloading the external load force, the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 13 rebound quickly under the elastic deformation of the material, and the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 13 push the insulating hydraulic oil 14 to flow back. The insulating hydraulic oil 14 acts in reverse on the upper flexible substrate 6 and the lower flexible substrate 12, accelerating the sensor to return to its initial state. Therefore, the sensor has a smaller hysteresis effect and a faster recovery time.

[0068] like Figure 1 and Figure 8As shown, the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 13 are used to compensate the water pressure once in the structure, and the BP neural network is used to compensate the water pressure twice in data processing. The BP neural network is constructed by a linear combination of inputs (the force output signal x1 of the sensor when there is only water pressure but no external force, and the force output signal x2 when there is both water pressure and external force), and is constructed by nonlinear conversion using an activation function. This neural network uses Sigmoid as the activation function, and uses the mean square error between the estimated value and the actual measured value as the loss function. The BP propagation algorithm is used to move in the negative gradient direction of the loss function each time until the loss function reaches the minimum value. The water pressure secondary compensation process of the BP neural network is as follows:

[0069] S1: A series of underwater contact force detection experiments are carried out on the underwater flexible tactile sensor of the present invention to obtain multiple groups of original data, each group of data includes a force output signal x1 of the sensor when only water pressure acts but no external force acts, and a force output signal x2 when both water pressure and external force act.

[0070] S2: Initialize the BP neural network, including 1 input layer, 1 hidden layer and 1 output layer, where the input layer has 2 outputs and the hidden layer has 5 neurons.

[0071] S3: Activate the forward propagation of the input signal to obtain the output value of each layer element, and then obtain the value of the loss function.

[0072] S4: According to the weight w between the input layer and the hidden layer ij And threshold θ, calculate the hidden layer output value.

[0073] S5: According to the weight w between the hidden layer and the output layer jk , threshold ψ and hidden layer output value, calculate the output value of the output layer, which is the predicted output of the BP neural network.

[0074] S6: Calculate the BP neural network prediction error e based on the BP neural network prediction output and the expected output y.

[0075] S7: Update the weight w according to the BP neural network prediction error e back propagation ij 、w jk and thresholds θ, ψ.

[0076] S8: Repeat steps S3-S7 until the loss function is less than a predetermined threshold or the maximum number of iterations is reached, and the parameters output at this time are the optimal parameters of the current BP neural network.

[0077] S9: Bring the above-mentioned optimal parameters of the BP neural network into the neural network model to obtain a trained neural network model, and use it for water pressure compensation of the underwater flexible tactile sensor.

[0078] The manufacturing process of the sensor of the present invention mainly includes the manufacturing and overall superposition assembly of the top porous boss layer 1, the upper interlocking layer 2, the middle layer 3, and the lower interlocking layer 4. The specific implementation steps are as follows: Fig. 9 As shown:

[0079] Step 1: Use 3D printing technology to print 3D printed molds that match the top porous boss layer 1, the upper interlocking layer 2, and the lower interlocking layer 4. Place the completed 3D printed mold in anhydrous ethanol and ultrasonically clean it for 30 minutes to wash away the dirt on the surface of the 3D printed mold. After ultrasonic cleaning, take out the 3D printed mold and completely dry it in a vacuum drying oven. Evenly apply a release agent on the surface of the 3D printed mold to peel off the various layers of the sensor components.

[0080] Step 2: Mix the polydimethylsiloxane (PDMS) main agent and the curing agent in a mass ratio of 5:1 to prepare a high-modulus PDMS substrate material, and pour it into the 3D printing mold prepared in step 1 that matches the upper flexible substrate 6, the upper interlocking microstructure 7, the lower interlocking microstructure 11 and the lower flexible substrate 12, place the 3D printing mold in a vacuum drying oven for degassing for 30 minutes, and then heat and cure the 3D printing mold at 70°C for 2 hours, and demold the prepared upper flexible substrate 6, the upper interlocking microstructure 7, the lower interlocking microstructure 11 and the lower flexible substrate 12 from the 3D printing mold.

[0081] Step 3: Mix the copolyester (Exoflex) main agent and the curing agent in a mass ratio of 1:1 to prepare a low-modulus Exoflex base material, and pour it into the 3D printed mold prepared in step 1 that matches the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 13, place the 3D printed mold in a vacuum drying oven for degassing for 30 minutes, then heat and cure the 3D printed mold at 70°C for 2 hours, and demold the prepared upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 13 from the 3D printed mold.

[0082] Step 4: Add 20% NaCl particles to the uncured 5:1 PDMS base material, use an ultrasonic disperser to ultrasonically disperse for 30 minutes, and then mix it in a planetary stirrer at a speed of 3000 rpm for 3 minutes to obtain an uncured NaCl-PDMS mixed solution, and then pour it into the 3D printed mold prepared in step 1 that matches the top porous boss 1, place the 3D printed mold in a vacuum drying oven for degassing for 30 minutes, and then heat and cure the 3D printed mold at 70°C for 2 hours, demold the prepared top porous boss 1 from the 3D printed mold, and soak it in clean water for 12 hours to completely dissolve the NaCl particles, forming an internally connected cavity in the top porous boss 1.

[0083] Step 5: PDMS main agent and curing agent are mixed in a mass ratio of 10:1 to prepare a PDMS base material, a layer of polyimide film is applied to the surface of a spin coater, and a 10:1 PDMS base material is dripped onto the polyimide film, and the spin coater is operated at a speed of 1600 revolutions per second to prepare a PDMS film with a thickness of 0.1 mm, which is heated and cured at 80° C. for 1 hour, and then a laser cutting machine is used to cut out the designed shape of the intermediate layer flexible substrate 10;

[0084] Graphene, carbon nanotubes, polyphenylmethylsiloxane, n-hexane, and 10:1 PDMS substrate material are mixed in a mass ratio of 5:1:6:200:100, and the mixed composite material is first ultrasonically dispersed in an ultrasonic disperser for 30 minutes, and then mixed in a planetary stirrer at a speed of 3000 rpm for 10 minutes to obtain an uncured sensitive material 8; the prepared intermediate layer flexible substrate 10 is placed on a clean glass plate, a screen printing plate matching the sensitive material 8 is placed parallel to the upper surface of the intermediate layer flexible substrate 10, and the prepared uncured sensitive material 8 is scraped into the gap of the screen printing plate. After completion, the screen printing plate is removed, and the sensitive material 8 is heated at 70°C for 1 hour to completely cure the sensitive material 8;

[0085] Silver nanosheets, 10:1 PDMS substrate material and polyvinyl pyrrolidone were mixed in a mass ratio of 225:100:2.5 and stirred in a planetary mixer for 3 minutes to obtain a paste-like flexible electrode 9 material. A screen printing plate matching the flexible electrode 9 was placed parallel to the upper surface of the intermediate layer flexible substrate 10 printed with the sensitive material 8, and the prepared paste-like flexible electrode 9 material was scraped into the gap of the screen printing plate. After completion, the screen printing plate was removed and heated at 70°C for 1 hour to cure, so that the flexible electrode 9 and the sensitive material 8 were firmly electrically connected.

[0086] Step 6: The connecting surfaces among the upper annular water pressure compensation chamber 5, the upper flexible substrate 6, the upper interlocking microstructure 7, the lower interlocking microstructure 11, the lower flexible substrate 12 and the lower annular water pressure compensation chamber 13 are subjected to plasma active treatment, and then the structures are aligned, heated and bonded to complete the manufacture of the upper interlocking layer 2 and the lower interlocking layer 4.

[0087] Step 7: Align the top porous boss 1, the upper interlocking layer 2, the middle layer 3, and the lower interlocking layer 4 in sequence, heat and cure them, and complete the assembly of the underwater flexible tactile sensor. A small gap is left at the connection interface between the upper interlocking layer 2 and the lower interlocking layer 4. The sensor is completely immersed in a beaker filled with insulating hydraulic oil 14, and the beaker is placed in a vacuum environment. Using the atmospheric pressure, the insulating hydraulic oil 14 enters the cavity of the sensor through the small gap and completely fills it.

[0088] Step 8: Remove the sensor from the insulating hydraulic oil, completely seal the small gap, perform hydrophobic treatment on the sensor surface, and complete the sensor manufacturing.

[0089] In the underwater flexible tactile sensor provided by the present invention, the holes in the top porous boss layer are interconnected, the underwater ocean currents are dispersed by the porous structure, and the sensor has a high sensitivity to detect underwater tiny forces. The upper interlocking layer and the lower interlocking layer are arranged opposite to each other to form a cavity, and the cavity is completely filled with insulating hydraulic oil. The upper annular water pressure compensation chamber and the lower annular water pressure compensation chamber balance the water pressure by contracting inward when only water pressure acts, and expand outward when there is an external load force to prevent the sensor from being squeezed and exploded by the insulating hydraulic oil. The upper interlocking layer and the lower interlocking layer form a secondary interlock, which can make the sensitive material stretch in both the circumferential direction and the diameter direction, so the sensor has high sensitivity in underwater force detection. The underwater flexible tactile sensor of the present invention includes a primary compensation for water pressure in the structure and a secondary compensation for water pressure in data processing. Compared with the traditional underwater flexible sensor, the sensor performance after water pressure compensation is not reduced, and high sensitivity and low interference detection of contact force when operating in different depths underwater can be achieved.

[0090] The above-mentioned specific implementation modes are used to explain the present invention rather than to limit the present invention. Any modification, equivalent substitution and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A highly sensitive underwater flexible tactile sensor, characterized in that: The sensor comprises a top porous boss layer (1), an upper interlocking layer (2), an intermediate layer (3) and a lower interlocking layer (4) which are coaxially arranged in sequence from top to bottom; a closed cavity is formed between the upper interlocking layer (2) and the lower interlocking layer (4), the cavity is filled with insulating hydraulic oil (14), an upper interlocking microstructure (7) is provided at the bottom of the upper interlocking layer (2), and a lower interlocking microstructure (11) is provided at the top of the lower interlocking layer (4); the intermediate layer (3) comprises an intermediate layer flexible substrate (10) and A sensitive material (8) and a flexible electrode (9) are arranged above an intermediate layer flexible substrate (10); the sensitive material (8) is patterned and electrically connected to the flexible electrode (9); the arrangement area of ​​the sensitive material (8) on the intermediate layer flexible substrate (10) is a sensitive area; the upper interlocking microstructure (7) is in contact with the top surface portion of the sensitive area of ​​the intermediate layer flexible substrate (10); and the lower interlocking microstructure (11) is in contact with the bottom surface portion of the sensitive area of ​​the intermediate layer flexible substrate (10).

2. The highly sensitive underwater flexible tactile sensor according to claim 1, characterized in that: The upper interlocking microstructure (7) and the lower interlocking microstructure (11) respectively include a plurality of upper interlocking micro-boss arrays and a plurality of lower interlocking micro-boss arrays, and the upper interlocking micro-boss arrays and the lower interlocking micro-boss arrays are uniformly distributed along the circumferential direction, and each upper interlocking micro-boss array / lower interlocking micro-boss array includes at least two upper interlocking micro-boss / lower interlocking micro-boss arrays arranged at equal intervals along the radial direction; a corresponding lower interlocking micro-boss array is arranged directly below each upper interlocking micro-boss array, and for a corresponding group of upper interlocking micro-boss arrays and lower interlocking micro-boss arrays, the shape of the upper interlocking micro-boss is adapted to the shape of the lower interlocking micro-boss, and the upper interlocking micro-boss and the lower interlocking micro-boss are staggered along the radial direction and can be interlocked with each other.

3. The highly sensitive underwater flexible tactile sensor according to claim 2, characterized in that: The upper interlocking micro-boss array includes four first upper interlocking micro-boss arrays (7-A) and four second upper interlocking micro-boss arrays (7-B), and the lower interlocking micro-boss array includes four first lower interlocking micro-boss arrays (11-A) and four second lower interlocking micro-boss arrays (11-B), and the number of upper interlocking micro-boss / lower interlocking micro-boss in each upper interlocking micro-boss array / lower interlocking micro-boss array is three; in the first upper interlocking micro-boss array (7-A) and the first lower interlocking micro-boss array (11-A), the shape of the upper interlocking micro-boss is adapted to the shape of the lower interlocking micro-boss; in the second upper interlocking micro-boss array (7-B) and the second lower interlocking micro-boss array (11-B), the shape of the upper interlocking micro-boss is adapted to the shape of the lower interlocking micro-boss.

4. The highly sensitive underwater flexible tactile sensor according to any one of claims 2 or 3, characterized in that: The pattern of the sensitive material (8) is a continuous curved pattern, which is formed by connecting two symmetrical serpentine line patterns, one end of each of the two serpentine line patterns is connected at the center of the upper interlocking layer (2) and the lower interlocking layer (4), and the other end of each of the two serpentine line patterns is located at the edge of the intermediate layer flexible substrate (10) and is electrically connected to the flexible electrode (9) respectively; each serpentine line pattern includes a plurality of circular arc patterns that are evenly spaced and connected end to end along the radial direction, and all the circular arc patterns have the connection point as the center of the circle; each circular arc pattern alternately passes through the bottom of the upper interlocking micro-protrusion and the top of the lower interlocking micro-protrusion.

5. The highly sensitive underwater flexible tactile sensor according to any one of claims 2 or 3, characterized in that: The adapted shapes are respectively a first wedge-shaped body and a second wedge-shaped body, wherein the geometric gradient of the first wedge-shaped body is opposite to the geometric gradient of the second wedge-shaped body.

6. The highly sensitive underwater flexible tactile sensor according to claim 1, characterized in that: The upper interlocking layer (2) further comprises an upper annular water pressure compensation chamber (5) and an upper flexible substrate (6), the top surface and the bottom surface of the upper flexible substrate (6) are respectively bonded with a top porous boss layer (1) and an upper interlocking microstructure (7), the outer edge of the upper flexible substrate (6) extends downward to form an upper side portion; the inner ring edge of the top of the upper annular water pressure compensation chamber (5) extends radially inward to form an upper annular connecting portion, the inner wall surface of the upper annular connecting portion is connected to the outer peripheral surface of the upper flexible substrate (6); the lower interlocking layer (4) further comprises a lower annular water pressure compensation chamber (13 ) and a lower flexible substrate (12), the top surface of the lower flexible substrate (12) being bonded with a lower interlocking microstructure (11), the outer edge of the lower flexible substrate (12) extending upward to form a lower side portion, and the lower flexible substrate (12) being arranged inside a lower annular water pressure compensation chamber (13); the inner ring edge of the bottom of the lower annular water pressure compensation chamber (13) extending radially inward to form a lower annular connecting portion, the inner wall surface of the lower annular connecting portion being connected to the outer peripheral surface of the lower flexible substrate (12); the upper annular connecting portion and the lower annular connecting portion being bonded to form the cavity.

7. The highly sensitive underwater flexible tactile sensor according to claim 6, characterized in that: The upper side portion and the lower side portion are both provided with a plurality of openings, and the openings are all opened in the radial direction. After the upper side portion and the lower side portion are bonded together, an inner cavity communicating with the cavity is formed.

8. The highly sensitive underwater flexible tactile sensor according to claim 6, characterized in that: The upper flexible substrate (6) and the lower flexible substrate (12) are both made of a first flexible material, and the upper annular water pressure compensation chamber (5) and the lower annular water pressure compensation chamber (13) are both made of a second flexible material, and the Young's modulus of the first flexible material is greater than the Young's modulus of the second flexible material.

9. The highly sensitive underwater flexible tactile sensor according to claim 1, characterized in that: The top porous boss layer (1) is prepared by mixing polydimethylsiloxane and sodium chloride particles, curing the mixture, and washing the mixture with water.

10. A pressure detection method using the highly sensitive underwater flexible tactile sensor according to any one of claims 1 to 9, characterized in that: The steps of the pressure detection method are specifically as follows: S1) installing the sensor at a preset position underwater, at which time the sensor is not subjected to external load force, and the upper annular water pressure compensation chamber (5) and the lower annular water pressure compensation chamber (13) automatically adjust the degree of inward contraction according to the change of external water pressure, thereby compensating the water pressure once in the structure; S2) When the sensor is subjected to an external load force, the upper annular water pressure compensation chamber (5) and the lower annular water pressure compensation chamber (13) expand outward, and the external load force presses the upper interlocking layer (2) downward, and the upper interlocking layer (2) and the lower interlocking layer (4) are pressed together, so that the upper interlocking microstructure (7) and the lower interlocking microstructure (11) form an interlocking positioning structure and stretch the sensitive material (8), and the resistance of the sensitive material (8) changes with its own deformation, and the output electrical signal of the flexible electrode (9) also changes accordingly; S3) using a back propagation neural network to perform secondary compensation for the water pressure in data processing: an external controller receives an output electrical signal of the flexible electrode (9), and inputs it into a pre-trained back propagation neural network model for processing, and the back propagation neural network model outputs a compensated pressure value; S4) After the external load force is unloaded, the upper annular water pressure compensation chamber (5) and the lower annular water pressure compensation chamber (13) rebound inward, the acceleration sensor returns to its initial state, and the resistance of the sensitive material (8) and the output electrical signal of the flexible electrode (9) return to their initial values.

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