High-sensitivity underwater flexible tactile sensor and pressure detection method

Abstract

The application discloses a kind of high-sensitivity underwater flexible tactile sensor and pressure detection method.Sensor includes top porous boss layer, upper interlocking layer, middle layer and lower interlocking layer arranged coaxially in turn from top to bottom;Upper interlocking layer and lower interlocking layer form airtight cavity between them, the cavity is filled with insulating hydraulic oil, upper interlocking layer is provided with upper interlocking microstructure, lower interlocking layer is provided with lower interlocking microstructure, and upper interlocking microstructure, lower interlocking microstructure and middle layer are all located in the cavity;Middle layer includes middle layer flexible substrate, and sensitive material and flexible electrode arranged above middle layer flexible substrate, sensitive material is designed with patterning and electrically connected with flexible electrode;The method is compensated for water pressure in structure and data processing respectively, and can output high-precision pressure value under different water pressures.The underwater flexible tactile sensor of the application can realize high-sensitivity, low-interference detection of contact force when working in underwater different depth environments.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of underwater contact force detection, in particular to a high-sensitivity underwater flexible tactile sensor and a pressure detection method. BACKGROUND

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

[0003] However, due to a series of obstacles caused by underwater environments, current underwater sensing technology is still very limited, and the technical challenge that needs to be addressed urgently is how to compensate for the increasing water pressure with increasing water depth. Chinese patent CN115752871A uses the self-balancing of water to offset water pressure through an open structure, but water is conductive, especially seawater, so the sensor will lose part of the sensing performance or even short circuit. Chinese patent CN117158953A first detects the water pressure signal, then uses numerical calculation to compensate for the water pressure, but the additional water pressure measurement sensor increases the complexity of the device, and the water pressure is only compensated through data processing without being directly offset by structural design, which reduces the sensitivity and range of the sensor when the water pressure acts on the surface of the sensor. SUMMARY

[0004] To solve the problems in the background art, the present application provides a high-sensitivity underwater flexible tactile sensor and a pressure detection method, which can realize automatic compensation of different sizes of pressure under water and high-sensitivity detection of underwater large-range tactile force.

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

[0006] I. A high-sensitivity underwater flexible tactile sensor

[0007] The sensor comprises, from top to bottom, a top porous boss layer, an upper interlocking layer, a middle layer and a lower interlocking layer arranged coaxially; a closed cavity is formed between the upper interlocking layer and the lower interlocking layer, and the cavity is filled with insulating hydraulic oil, which is used to offset the changing water pressure from the outside. The bottom of the upper interlocking layer is provided with an upper interlocking microstructure, and the top of the lower interlocking layer is provided with a lower interlocking microstructure, and the upper interlocking microstructure, the lower 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 arranged above the middle layer flexible substrate, the sensitive material is designed in a pattern and is electrically connected with the flexible electrode, the pattern of the sensitive material is a sensitive area in the arrangement area of the middle layer flexible substrate, the upper interlocking microstructure is in partial contact with the top surface of the sensitive area of the middle layer flexible substrate, and the lower interlocking microstructure is in partial contact with the bottom surface of the sensitive area of the middle layer flexible substrate.

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

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

[0010] The upper interlocking microstructure and the lower interlocking microstructure each comprise a same number of upper interlocking micro-boss arrays and lower interlocking micro-boss arrays, the upper interlocking micro-boss arrays and the lower interlocking micro-boss arrays are uniformly distributed along the circumferential direction of the upper interlocking layer and the lower interlocking layer respectively, each upper interlocking micro-boss array / lower interlocking micro-boss array comprises 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 inside to outside along the radial direction.

[0011] Each of the upper interlocking micro-bump arrays is correspondingly arranged with a lower interlocking micro-bump array. For a corresponding set of upper interlocking micro-bump arrays and lower interlocking micro-bump arrays, the shape of the upper interlocking micro-bump is adapted to the shape of the lower interlocking micro-bump, and the upper interlocking micro-bump and the lower interlocking micro-bump are arranged in a radial direction (arrangement direction) staggered and capable of being mutually embedded. Specifically, the mutual embedding refers to that in the same upper interlocking micro-bump array / lower interlocking micro-bump array, a micro-groove is formed between two adjacent upper interlocking micro-bumps / lower interlocking micro-bumps, 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-bump in the upper interlocking micro-bump array can be embedded into the micro-groove in the corresponding lower interlocking micro-bump array. When the sensor bears an external load force, the upper interlocking microstructure extrudes the intermediate layer downward, and each upper interlocking micro-bump is pressed into the micro-groove in the corresponding lower interlocking micro-bump array. The staggered arrangement refers to that the projection of the upper interlocking micro-bump and the lower interlocking micro-bump on the same horizontal plane is arranged in a radial direction staggered.

[0012] Correspondingly, the pattern of the sensitive material is set as a continuous curved pattern, and the curved pattern is connected by two symmetrical snake line patterns, the symmetry axis is any two upper interlocking micro-bump arrays or corresponding lower interlocking micro-bump arrays with an interval of 180° central angle, one end of each of the two snake line patterns is connected, the connection of the two snake line patterns is located at the common center of the upper interlocking layer and the lower interlocking layer, the other end of each of the two snake line patterns is respectively arranged on the two sides of the symmetry axis and is located at the edge of the top surface of the flexible substrate of the intermediate layer, and the other end of each of the two snake line patterns is respectively electrically connected with the positive electrode and the negative electrode of the flexible electrode; each of the snake line patterns includes a plurality of circular arc patterns arranged uniformly in a radial direction and connected in a head-to-tail manner, the number of the circular arc patterns is the same as the number of the upper interlocking micro-bumps / lower interlocking micro-bumps in each of the upper interlocking micro-bump arrays / lower interlocking micro-bump arrays, and the common center of all the circular arc patterns is the connection of the two snake line patterns. Each of the circular arc patterns alternately passes from below the corresponding upper interlocking micro-bump to above the corresponding lower interlocking micro-bump.

[0013] Preferably, all the circular arc patterns are connected in a head-to-tail manner by a plurality of U-shaped patterns to form a continuous snake line.

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

[0015] Correspondingly, the symmetry axis of the curved pattern is the first upper interlocking micro -papilla array with a central angle of 180°, and the plurality of arc patterns comprise a first arc pattern, a second arc pattern and a third arc pattern arranged in the radial direction from outside to inside, the first end of the first arc pattern is the end of the serpentine pattern, and the end of the third arc pattern extends to the connection through a U-shaped pattern; the first arc pattern passes under the outermost upper interlocking micro -papilla of the second upper interlocking micro -papilla array, above the outermost lower interlocking micro -papilla of the first lower interlocking micro -papilla array, and under the outermost upper interlocking micro -papilla of the second upper interlocking micro -papilla array in turn; the second arc pattern and the third arc pattern are arranged in the same mode as the first arc pattern and cooperate with the second upper interlocking micro -papilla array, the first lower interlocking micro -papilla array and the second upper interlocking micro -papilla array. The arrangement of the second arc pattern and the third arc pattern is that the second arc pattern passes under the middle upper interlocking micro -papilla of the second upper interlocking micro -papilla array, above the middle lower interlocking micro -papilla of the first lower interlocking micro -papilla array, and under the middle upper interlocking micro -papilla of the second upper interlocking micro -papilla array in turn; the third arc pattern passes under the innermost upper interlocking micro -papilla of the second upper interlocking micro -papilla array, above the innermost lower interlocking micro -papilla of the first lower interlocking micro -papilla array, and under the innermost upper interlocking micro -papilla of the second upper interlocking micro -papilla array in turn.

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

[0017] Preferably, the micro-bumps achieve interlocking between the upper interlocking layer and the lower interlocking layer through a wedge-shaped fit. The compatible shapes are a first wedge and a second wedge, respectively, and the geometric gradient of the first wedge is opposite to that of the second wedge.

[0018] Preferably, in the second upper interlocking micro-bump array, the bottom surface of the upper interlocking micro-bump is in contact with the sensitive area, and in order to improve the sensitivity, the area is larger than the bottom surface area of the upper interlocking micro-bump in the first upper interlocking micro-bump array. Similarly, the bottom surface area of the lower interlocking micro-bump in the first lower interlocking micro-bump array is larger than the bottom surface area of the lower interlocking micro-bump in the second lower interlocking micro-bump array. The sensitive area is the arrangement area of the sensitive material.

[0019] The upper interlocking layer further comprises an upper annular water pressure compensation chamber and an upper layer flexible substrate, the top surface of the upper layer flexible substrate is bonded with a top porous bump layer, and the bottom surface of the top porous bump layer is closely combined with the top surface of the upper layer flexible substrate, the bottom surface of the upper layer flexible substrate is bonded with an upper layer interlocking microstructure, the bottom end of the upper layer interlocking microstructure is in contact with the intermediate layer, the outer edge of the upper layer flexible substrate extends downward along the axial direction to form an upper side portion, the upper layer 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 a ring-shaped main body with a certain height, the inner ring edge of the top of the ring-shaped main body (the main body of the upper annular water pressure compensation chamber) extends radially inward to form an upper annular connecting portion, and the inner wall surface of the upper annular connecting portion is connected with the outer peripheral surface of the upper layer flexible substrate, specifically, the inner wall surface of the upper annular connecting portion is bonded with the outer peripheral surface of the top of the upper layer flexible substrate.

[0020] The lower interlocking layer further comprises a lower annular water pressure compensation chamber and a lower layer flexible substrate, the top surface of the lower layer flexible substrate is bonded with a lower layer interlocking microstructure, the top end of the lower layer interlocking microstructure is in contact with the intermediate layer, the outer edge of the lower layer flexible substrate extends upward along the axial direction to form a lower side portion, and the lower layer 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 a ring-shaped main body with a certain height, the inner ring edge of the bottom of the ring-shaped main body (the main body of the lower annular water pressure compensation chamber) extends radially inward to form a lower annular connecting portion, and the inner wall surface of the lower annular connecting portion is connected with the outer peripheral surface of the lower layer flexible substrate, specifically, the inner wall surface of the lower annular connecting portion is bonded with the outer peripheral surface of the top of the lower layer flexible substrate.

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

[0022] The upper side and the lower side are each provided with a plurality of openings on the outer circumferential surface, the openings are each radially formed, so that the bottom end surface of the upper side and the top end surface of the lower side are bonded in alignment to form an inner cavity in communication with 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 layer flexible substrate and the lower layer flexible substrate are each made of a first flexible material, and the upper annular water pressure compensation chamber and the lower annular water pressure compensation chamber are each 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.

[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 application, the upper annular water pressure compensation chamber and the lower annular water pressure compensation chamber are made of a low Young's modulus copolyester (Exoflex), and the upper layer flexible substrate and the lower layer flexible substrate are made of a high Young's modulus PDMS.

[0025] Further, the upper layer flexible substrate, the upper interlocking microstructure, the lower interlocking microstructure, and the lower layer flexible substrate can be obtained by integrated manufacturing or the like. For example, the integrated manufacturing can be performed by injecting an uncured material into a reverse mold, heating and curing, and demolding. The reverse mold can be manufactured by 3D printing.

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

[0027] The top porous boss layer is used to bear an external load and improve the resistance of the sensor to underwater disturbance. The top porous boss layer is arranged on the top surface of the upper interlocking layer. In the present application, the external load is a normal force, i.e., a force applied from top to bottom. The top porous boss layer is prepared by mixing polydimethylsiloxane (PDMS) and sodium chloride particles (NaCl), and then solidifying and washing with water. NaCl is dissolved to form internal interconnected pores. The particle size of the NaCl particles is 50 μm. The mass ratio of polydimethylsiloxane to sodium chloride particles is preferably 2-5:1. The lower the mass ratio, the more pores, the stronger the water flow resistance, and the weaker the force transmission ability.

[0028] The flexible electrode includes a positive electrode and a negative electrode. The flexible electrode is connected with an external detection circuit, which is used for detecting the resistance change of the sensitive material, and then obtaining the contact force information of the sensor underwater.

[0029] Two, a pressure detection method using the above high-sensitivity underwater flexible tactile sensor

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

[0031] S1) The sensor is installed 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 inward shrinkage degree according to the water pressure change of the external environment, and part of the insulating hydraulic oil flows into the inner cavity to balance the water pressure, and then the water pressure is compensated once on the structure.

[0032] S2) When the sensor is subjected to 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 extrudes 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, the resistance of the sensitive material changes with the deformation of the sensitive material, and the output electric signal of the flexible electrode also changes; the interlocking positioning structure is that the second upper interlocking micro-boss array and the first lower interlocking micro-boss array form a primary interlocking in the circumferential direction of the sensitive material; the first upper interlocking micro-boss array and the first lower interlocking micro-boss array and the second upper interlocking micro-boss array and the second lower interlocking micro-boss array form a secondary interlocking in the diameter direction of the sensitive material.

[0033] S3) The back propagation (BP) neural network is used for secondary compensation of the water pressure in data processing: the output electric signal of the flexible electrode is received by the external controller in real time, and is input into the back propagation (BP) neural network model which is trained in advance 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, accelerate the recovery of the sensor to the initial state, and the resistance of the sensitive material and the output electric signal of the flexible electrode return to the initial value.

[0035] The present application has the beneficial effects that:

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

[0037] 2) The internal holes of the top porous boss layer are connected to each other, and external water can freely enter and fill the internal part of the top porous boss layer, preventing it from being compressed under water pressure to maintain the force transmission performance of the top porous boss; in addition, when the underwater current acts on the top porous boss layer, the current is dispersed by the porous structure to improve the sensor's resistance to underwater disturbances and achieve the detection of small forces underwater.

[0038] 3) The upper and lower annular water pressure compensation chambers balance the water pressure by shrinking inward when there is only water pressure, and expand outward to avoid the sensor being squeezed by the insulating hydraulic oil when there is external load force; in addition, after the external load force is removed, the annular water pressure compensation chamber restores under the material resilience, the upper and lower annular water pressure compensation chambers push the insulating hydraulic oil inward, and the insulating hydraulic oil accelerates the upper and lower interlocking layers to return to the initial state, so the sensor has smaller hysteresis effect and faster recovery time.

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

[0040] 5) The annular water pressure compensation chamber compensates the water pressure once in structure, and the sensor's force detection performance does not decrease significantly under the action of water pressure; the BP neural network compensates the water pressure twice in data processing, and the combination of structural compensation and numerical compensation enables the sensor to maintain high-precision and high-sensitivity force detection capability under different water pressures. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a split stereogram of the layered structure of the underwater flexible sensor of the present application;

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

[0043] Figure 3 is a front view and a top view of the top porous boss layer of the underwater flexible sensor of the present application;

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

[0045] Figure 5(a) is a structure perspective view of the upper and lower interlocking microstructures and the intermediate layer, Figure 5 (b) is a top view of the structure of the upper and lower interlocking microstructures and the intermediate 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 is the deformation and strain simulation result diagram of the underwater flexible sensor of the present application under different water pressures;

[0047] Figure 7 is the deformation and strain simulation result diagram of the underwater flexible sensor of the present application under the same water pressure and different external load forces;

[0048] Figure 8 is the BP neural network model diagram used by the underwater flexible sensor of the present application;

[0049] Figure 9 is the manufacturing process diagram of the underwater flexible sensor of the present application.

[0050] In the figure: 1, top porous boss layer; 2, upper interlocking layer; 3, intermediate layer; 4, lower interlocking layer; 5, upper annular water pressure compensation chamber; 6, upper layer flexible substrate; 7, upper interlocking microstructure; 8, sensitive material; 9, flexible electrode; 10, intermediate layer flexible substrate; 11, lower interlocking microstructure; 12, lower layer 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 application will be further described in detail below in combination with the drawings and specific embodiments.

[0052] As shown in Figure 1 and Figure 2 , the underwater flexible tactile sensor proposed by the present application includes a top porous boss layer 1, an upper interlocking layer 2, an intermediate layer 3, and a lower interlocking layer 4, which are arranged in a stacked manner from top to bottom. The sensor as a whole presents 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 layer flexible substrate 6 and an upper layer interlocking microstructure 7, the bottom surface of the top porous boss layer 1 is tightly attached to the top surface of the upper layer flexible substrate 6, and the outer circumferential surface of the top end of the upper layer flexible substrate 6 is tightly bonded to the inner wall surface of the top end of the upper annular water pressure compensation chamber 5. The height of the upper annular water pressure compensation chamber 5 and the upper layer flexible substrate 6 is 1 mm, and the top surfaces of the two 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 arranged in turn from top to bottom, the two end pins of the sensitive material 8 are connected with the flexible electrode 9 respectively, the flexible electrode 9 is connected with an external detection circuit, which is used for detecting the resistance change of the sensitive material 8, and then obtaining the contact force information of the sensor underwater. The thickness of the sensitive material 8, the flexible electrode 9 and the middle layer flexible substrate 10 is 0.1 mm. The flexible electrode 9 includes a positive electrode and a negative electrode.

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

[0056] The upper interlocking layer 2 and the lower interlocking layer 4 are arranged in close contact to form a closed cavity, the cavity is completely filled with insulating hydraulic oil 14, at different depths underwater, the insulating hydraulic oil 14 shrinks under pressure, the pressure increases to offset the change of external water pressure; the upper layer interlocking microstructure 7 and the lower layer interlocking microstructure 11 form an interlocking positioning structure, under the external load, the upper layer interlocking microstructure 7 and the lower layer interlocking microstructure 11 respectively extrude the middle layer flexible substrate 10, and then stretch the sensitive material 8, so that the sensitive material 8 outputs a change in resistance signal.

[0057] As shown in Figure 1 and Figure 4 , the upper layer interlocking microstructure 7 is mainly composed of a first upper interlocking micro boss array 7-A and a second upper interlocking micro boss array 7-B; the lower layer interlocking microstructure 11 is mainly composed of a first lower interlocking micro boss array 11-A and a second lower interlocking micro boss array 11-B, and the upper layer interlocking microstructure 7 and the lower layer interlocking microstructure 11 are arranged in close contact. 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 layer 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 layer flexible substrate 12.

[0058] As shown in Figure 4 and Figure 5As shown, the micro-protrusions are all wedge-shaped. The larger side of the wedge (such as the top surface of the upper interlocking micro-protrusion and the bottom surface of the lower interlocking micro-protrusion) is used for bonding with the upper flexible substrate 6 or the lower flexible substrate 12, while the smaller side (such as the bottom surface of the upper interlocking micro-protrusion and the top surface of the lower interlocking micro-protrusion) is used for contact with the intermediate flexible substrate 10. Furthermore, the bottom surface area of ​​the upper interlocking micro-protrusions in the second upper interlocking micro-protrusion array 7-B is larger than the bottom surface area of ​​the upper interlocking micro-protrusions in the first upper interlocking micro-protrusion array 7-A. The top surface area of ​​the lower interlocking micro-protrusions in the first lower interlocking micro-protrusion array 11-A is larger than the top surface area of ​​the lower interlocking micro-protrusions in the second lower interlocking micro-protrusion array 11-B.

[0059] like Figure 5 As shown, the upper interlocking microstructure 7 and the lower interlocking microstructure 11 form a two-level interlock. The second upper interlocking micro-protrusion array 7-B and the first lower interlocking micro-protrusion array 11-A form a first-level interlock in the circumferential direction of the sensitive material 8. The first upper interlocking micro-protrusion array 7-A and the first lower interlocking micro-protrusion 7-B, and the second upper interlocking micro-protrusion 11-A and the second lower interlocking micro-protrusion array 11-B form a second-level interlock in the diametrical direction of the sensitive material 8. The two-level interlock causes the sensitive material 8 to be stretched bidirectionally, resulting in higher sensor sensitivity.

[0060] like Figure 1 and Figure 4 As shown, four windows communicating with the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 11 are respectively opened on the outer peripheral surfaces of the upper flexible substrate 6 and the lower flexible substrate 12. 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 protrusion layer 1 is prepared by mixing PDMS with NaCl particles. When the top porous protrusion layer 1 is immersed in water, the NaCl completely dissolves, forming interconnected pores. Therefore, the pores inside the top porous protrusion layer 1 are interconnected, allowing external water to freely enter and fill the interior of the top porous protrusion layer 1, preventing it from being compressed under water pressure and maintaining its force transmission performance. Furthermore, when underwater currents act on the top porous protrusion layer 1, the currents are dispersed by the porous structure, improving the sensor's resistance to underwater disturbances and enabling the sensor to detect minute underwater forces. The top porous protrusion layer 1 is generally truncated conical in shape, with a height of 2 mm, a maximum base diameter of 10 mm, and a minimum top diameter of 5 mm.

[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; 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 more easily deformed than PDMS with high Young's modulus under the same pressure.

[0063] The thickness of the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 13 is less than that of the upper flexible substrate 6 and the lower flexible substrate 12. Specifically, the overall wall thickness of the upper annular water 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 thickness (upper side) is 1 mm; the overall wall thickness of the lower annular water 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 thickness (lower side) is 1 mm. The smaller the wall thickness, the more easily the structure deforms.

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

[0065] As shown in Figure 6 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 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, the positions of the upper flexible substrate 6 and the lower flexible substrate 12 remain stable without obvious deformation and strain, and therefore the resistance of the sensitive material 8 does not change significantly, i.e. 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] As shown in Figure 7 When the sensor is subjected to 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, preventing the sensor from exploding. The simulation results show that under the same water pressure, as the external load force acting on the sensor increases, the degree of outward expansion of the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 13 gradually increases to provide more space for the flow of the insulating hydraulic oil 14.

[0067] After the external load force is removed, the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 13 quickly rebound under the elastic deformation of the material, 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, and the insulating hydraulic oil 14 acts on the upper flexible substrate 6 and the lower flexible substrate 12 in the opposite direction, accelerating the recovery of the sensor to the initial state, so that the sensor has smaller hysteresis effect and faster recovery time.

[0068] As shown in Figure 1 and Figure 8As shown, the water pressure is structurally compensated once by using the upper annular water pressure compensation chamber 5 and the lower annular water pressure compensation chamber 13, and is data-processed compensated twice by using the BP neural network. The BP neural network is constructed by linear combination between inputs (the force output signal x1 of the sensor under the action of water pressure only without the action of external force, and the force output signal x2 under the action of both water pressure and external force), and non-linear conversion by using an activation function. The neural network selects Sigmoid as the activation function, takes the mean square error between the estimated value and the actual measured value as the loss function, and uses the BP propagation algorithm to move in the negative gradient direction of the loss function each time until the loss function reaches the minimum value. The water pressure twice compensation process of the BP neural network is as follows:

[0069] S1: A series of underwater contact force detection experiments are performed on the underwater flexible tactile sensor of the application to obtain a plurality of groups of original data, each group of data including the force output signal x1 of the sensor under the action of water pressure only without the action of external force, and the force output signal x2 under the action of both water pressure and external force.

[0070] S2: The BP neural network is initialized, including 1 input layer, 1 hidden layer and 1 output layer, wherein the input layer has 2 outputs, and the hidden layer has 5 neurons.

[0071] S3: The input signal is activated and forward propagated to obtain the output value of each layer element, and then the value of the loss function is obtained.

[0072] S4: The hidden layer output value is calculated according to the weight w ij and the threshold value θ between the input layer and the hidden layer.

[0073] S5: The output layer output value, i.e. the BP neural network prediction output, is calculated according to the weight w jk , the threshold value ψ and the hidden layer output value between the hidden layer and the output layer.

[0074] S6: The BP neural network prediction error e is calculated according to the BP neural network prediction output and the expected output y.

[0075] S7: The weight w ij , w jk and the threshold value θ, ψ are updated according to the BP neural network prediction error e back propagation.

[0076] S8: Steps S3-S7 are repeated until the loss function is less than a pre-given threshold value or the maximum iteration number is reached, and the parameters at this time are output as the optimal parameters of the current BP neural network.

[0077] S9: The above optimal parameters of the BP neural network are brought into the neural network model to obtain a trained neural network model, which is used for water pressure compensation of the underwater flexible tactile sensor.

[0078] The manufacturing process of the sensor of the present application mainly includes the manufacturing and overall superimposed assembly of each layer of the top porous boss layer 1, the upper interlocking layer 2, the middle layer 3, and the lower interlocking layer 4, and the specific implementation steps are as shown in the following table: Figure 9

[0079] Step 1: Use 3D printing technology to print 3D printing molds matched with each part of the top porous boss layer 1, the upper interlocking layer 2, and the lower interlocking layer 4 respectively, place the finished 3D printing mold in anhydrous ethanol and ultrasonically clean for 30 min, wash off the dirt on the surface of the 3D printing mold, etc., after ultrasonic cleaning, take out the 3D printing mold and dry it completely in a vacuum drying box, evenly apply release agent on the surface of the 3D printing mold to facilitate the stripping of each layer of the sensor parts.

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

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

[0082] ​Step 4: Add 20% NaCl particles into the uncured 5:1 PDMS base material, use ultrasonic disperser to disperse for 30 min, then mix in a planetary mixer at 3000 rpm for 3 min, to obtain the uncured NaCl-PDMS mixture, then pour it into the 3D printed mold matching the top porous boss 1 prepared in step 1, place the 3D printed mold in a vacuum drying oven for 30 min to degas, then heat and cure the 3D printed mold at 70°C for 2 h, demold the prepared top porous boss 1 from the 3D printed mold, and soak it in clean water for 12 h to completely dissolve the NaCl particles, forming internally connected cavities in the top porous boss 1.

[0083] Step 5: Mix the PDMS main agent with the curing agent in a mass ratio of 10:1 to prepare the PDMS base material, apply a layer of polyimide film to the surface of the spin coater, and drop 10:1 PDMS base material onto the polyimide film, and run the spin coater at 1600 rpm to prepare a PDMS film with a thickness of 0.1 mm, which is then heated and cured at 80°C for 1 h, and then cut into the designed shape of the middle layer flexible substrate 10 using a laser cutting machine;

[0084] Mix graphene, carbon nanotubes, polyphenylmethylsiloxane, n-hexane, and 10:1 PDMS base material in a mass ratio of 5:1:6:200:100, first ultrasonically disperse the mixed composite material in an ultrasonic disperser for 30 min, then mix in a planetary mixer at 3000 rpm for 10 min to obtain the uncured sensitive material 8; Place the prepared middle layer flexible substrate 10 on a clean glass plate, place the screen printing plate matching the sensitive material 8 parallel on the upper surface of the middle layer flexible substrate 10, and scrape the prepared uncured sensitive material 8 into the gap of the screen printing plate, remove the screen printing plate after completion, and heat at 70°C for 1 h to completely cure the sensitive material 8;

[0085] Mix silver nanosheets, 10:1 PDMS base material, and polyvinylpyrrolidone in a mass ratio of 225:100:2.5, then stir in a planetary mixer for 3 min to obtain a paste-like flexible electrode 9 material, place the screen printing plate matching the flexible electrode 9 parallel on the upper surface of the middle layer flexible substrate 10 on which the sensitive material 8 has been printed, scrape the prepared paste-like flexible electrode 9 material into the gap of the screen printing plate, remove the screen printing plate after completion, and heat at 70°C for 1 h to cure, so that the flexible electrode 9 is firmly electrically connected with the sensitive material 8.

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

[0087] Step 7: the top porous boss 1, the upper interlocking layer 2, the intermediate layer 3 and the lower interlocking layer 4 are sequentially and directly attached and heated to be bonded, thereby completing the assembly of the underwater flexible tactile sensor. A small gap is left at the connecting interface of the upper interlocking layer 2 and the lower interlocking layer 4, the sensor is completely immersed in a beaker containing insulating hydraulic oil 14, and the beaker is placed in a vacuum environment, so that the insulating hydraulic oil 14 enters the internal cavity of the sensor through the small gap under the action of atmospheric pressure and is completely filled.

[0088] Step 8: the sensor is taken out of the insulating hydraulic oil, the small gap is completely sealed, and the surface of the sensor is subjected to hydrophobic treatment, thereby completing the manufacture of the sensor.

[0089] In the underwater flexible tactile sensor provided by the application, the cavities in the top porous boss layer are connected to each other, the underwater ocean current is dispersed by the porous structure, and the sensor has high sensitivity in detecting underwater micro force. The upper interlocking layer and the lower interlocking layer are arranged in opposition to form a cavity, the cavity is completely filled with insulating hydraulic oil, and the upper annular water pressure compensation chamber and the lower annular water pressure compensation chamber are balanced by inward shrinkage under the action of water pressure only, and are expanded outward to avoid the sensor being squeezed and exploded by the insulating hydraulic oil under the action of external load force. The upper interlocking layer and the lower interlocking layer form a two-stage interlocking, so that the sensitive material is stretched in the circumferential direction and the diameter direction, and therefore the sensor has high sensitivity in detecting force underwater. The underwater flexible tactile sensor of the application includes one-stage compensation for water pressure in structure and two-stage compensation for water pressure in data processing, and compared with the traditional underwater flexible sensor, the performance of the sensor after water pressure compensation is not reduced, and the sensor can realize high sensitivity and low interference detection of contact force in underwater operation at different depths.

[0090] The above specific embodiments are used to explain and illustrate the application, rather than limit the application, and any modification, equivalent replacement and change of the application within the spirit and protection scope of the claims are all within the protection scope of the application.

Claims

1. A high-sensitivity underwater flexible tactile sensor, characterized by: The sensor comprises, from top to bottom, a top porous boss layer (1), an upper interlocking layer (2), an intermediate layer (3), and a lower interlocking layer (4) arranged coaxially; a closed cavity is formed between the upper interlocking layer (2) and the lower interlocking layer (4), and the cavity is filled with insulating hydraulic oil (14); the bottom of the upper interlocking layer (2) is provided with an upper interlocking microstructure (7), and the top of the lower interlocking layer (4) is provided with a lower interlocking microstructure (11); the intermediate layer (3) comprises an intermediate layer flexible substrate (10), and a sensitive material (8) and a flexible electrode (9) arranged above the intermediate layer flexible substrate (10); the sensitive material (8) is designed in a pattern and is 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 partial contact with the top surface of the sensitive area of the intermediate layer flexible substrate (10), and the lower interlocking microstructure (11) is in partial contact with the bottom surface of the sensitive area of the intermediate layer flexible substrate (10).

2. The high-sensitivity underwater flexible tactile sensor according to claim 1, characterized in that: The upper interlocking microstructure (7) and the lower interlocking microstructure (11) each comprise a plurality of upper interlocking micro-boss arrays and a plurality of lower interlocking micro-boss arrays; the upper interlocking micro-boss arrays and the lower interlocking micro-boss arrays are uniformly distributed in the circumferential direction; each upper interlocking micro-boss array / lower interlocking micro-boss array comprises at least two upper interlocking micro-bosses / lower interlocking micro-bosses arranged at equal intervals in the radial direction; each upper interlocking micro-boss array is arranged below a lower interlocking micro-boss array; for a corresponding set of upper interlocking micro-boss arrays and lower interlocking micro-boss arrays, the shape of the upper interlocking micro-bosses is adapted to the shape of the lower interlocking micro-bosses; the upper interlocking micro-bosses and the lower interlocking micro-bosses are arranged in a radial staggered manner and can be mutually embedded.

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

4. The high-sensitivity 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 connected by two symmetrical snake-shaped patterns, one end of each of the two snake-shaped 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 snake-shaped patterns is located at the edge of the intermediate layer flexible substrate (10) and is electrically connected with the flexible electrode (9); each snake-shaped pattern includes a plurality of radially uniformly arranged and connected circular arc patterns, and all the circular arc patterns have the connecting part as the center; each circular arc pattern alternately passes below the upper interlocking micro-boss and above the lower interlocking micro-boss.

5. The high-sensitivity underwater flexible tactile sensor according to any one of claims 2 or 3, characterized in that: The corresponding shapes are a first wedge shape and a second wedge shape, and the geometric gradient of the first wedge shape is opposite to that of the second wedge shape.

6. The high-sensitivity 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 layer flexible substrate (6), the top surface and the bottom surface of the upper layer flexible substrate (6) are respectively bonded with a top porous boss layer (1) and an upper layer interlocking microstructure (7), and the outer edge of the upper layer flexible substrate (6) extends downward to form an upper side part; 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 part, and the inner wall surface of the upper annular connecting part is connected with the outer peripheral surface of the upper layer flexible substrate (6); the lower interlocking layer (4) further comprises a lower annular water pressure compensation chamber (13) and a lower layer flexible substrate (12), the top surface of the lower layer flexible substrate (12) is bonded with a lower layer interlocking microstructure (11), the outer edge of the lower layer flexible substrate (12) extends upward to form a lower side part, and the lower layer flexible substrate (12) is arranged inside the lower annular water pressure compensation chamber (13); the inner ring edge of the bottom of the lower annular water pressure compensation chamber (13) extends radially inward to form a lower annular connecting part, and the inner wall surface of the lower annular connecting part is connected with the outer peripheral surface of the lower layer flexible substrate (12); the upper annular connecting part and the lower annular connecting part are bonded to form the cavity.

7. The high-sensitivity underwater flexible tactile sensor according to claim 6, characterized in that: A plurality of openings are arranged on the upper side part and the lower side part, and the openings are radially arranged; the upper side part and the lower side part are bonded to form an inner cavity in communication with the cavity. 8.The high-sensitivity underwater flexible tactile sensor of claim 6, wherein: The upper layer flexible substrate (6) and the lower layer flexible substrate (12) are 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 made of a second flexible material; the Young's modulus of the first flexible material is greater than that of the second flexible material.

9. The high-sensitivity 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 and washing.

10. A pressure detection method using the high-sensitivity underwater flexible tactile sensor according to any one of claims 1 to 9, characterized by: The steps of the pressure detection method are as follows: S1) install the sensor at a predetermined position under water, at this time 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 inward contraction degree according to the change of external water pressure, and then compensate the water pressure in the structure; S2) When the sensor is subjected to external load force, the upper and lower annular water pressure compensation chambers (5) and (13) expand outward, the external load force presses the upper interlocking layer (2) downward, the upper interlocking layer (2) is pressed with the lower interlocking layer (4), so that the upper and lower interlocking microstructures (7) and (11) form an interlocking positioning structure and stretch the sensitive material (8), the resistance of the sensitive material (8) changes with its deformation, and the output electrical signal of the flexible electrode (9) also changes accordingly; S3) Secondary compensation of water pressure in data processing using back propagation neural network: the output electrical signal of the flexible electrode (9) is received by the external controller and input into the pre-trained back propagation neural network model for processing, and the back propagation neural network model outputs the compensated pressure value; S4) After unloading the external load force, the upper and lower annular water pressure compensation chambers (5) and (13) rebound inward, accelerating the sensor to return to the initial state, and the resistance of the sensitive material (8) and the output electrical signal of the flexible electrode (9) return to the initial value.

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