Robot electronic skin patch system and preparation method and application thereof

Abstract

The invention discloses a robot electronic skin patch system and a preparation method and application thereof, and relates to the technical field of robot electronic skin patch systems, and the robot electronic skin patch system comprises a flexible sensor and a signal acquisition and processing system. The flexible sensor comprises a first electrode layer, a second electrode layer and an elastic dielectric layer. The elastic dielectric layer is arranged between the first electrode layer and the second electrode layer and comprises an elastic dielectric component with a three-dimensional structure, and the elastic dielectric component can deform under the action of longitudinal pressure. According to the invention, the function of measuring the bending angle is added on the sensing assembly with the three-layer structure and the pressure measuring function, and real-time angle monitoring at the joint of the robot arm is realized. The electrodes on the same electrode layer can be independent of a sensing circuit, generated electric signals are transmitted to a signal acquisition system through respective leads, and the signals are processed and analyzed to obtain pressure and angle data. The robot electronic skin patch system is high in integration level, weak in signal crosstalk and high in measurement precision.

Description

Technical Field

[0001] The present invention relates to the technical field of robot electronic skin patch systems, and in particular to a robot electronic skin patch system and a preparation method and application thereof. Background Art

[0002] With the rapid development of robotics, especially the widespread application of humanoid robots and service robots in various fields, the demand for tactile perception in robots is increasing. Traditional rigid sensors, due to their lack of flexibility and adaptability, are unable to meet the needs of robots for sensing complex surfaces and dynamic interactive environments. Flexible electronic skin, with its high flexibility, lightweight, and high precision, significantly improves the system's environmental adaptability and operational accuracy, and is gradually becoming a research hotspot in the field of robotic perception.

[0003] In robotic arm applications, flexible sensors can be integrated into fingers or joints. They not only monitor parameters like pressure and deformation in real time, providing tactile feedback during grasping operations and preventing excessive force on fragile objects, but also adapt to irregular surfaces through bending strain detection. In collaborative robotics scenarios, their sensitive human-machine contact perception can trigger safety shutdown mechanisms, significantly improving interaction safety. Furthermore, through a distributed flexible sensor network, robots can develop dynamic perception capabilities for complex environments, providing smarter and safer solutions for scenarios such as intelligent manufacturing, medical surgery, and service robotics.

[0004] Currently, pressure sensors are primarily based on capacitive or resistive principles. Capacitive sensors typically employ a "sandwich" structure, measuring pressure by measuring capacitance changes caused by deformation of a dielectric layer. The Journal of Composite Materials (2021, Vol. 38, No. 7) reports on a flexible "sandwich" capacitive pressure sensor based on expandable microspheres and a polydimethylsiloxane (PDMS) dielectric layer, demonstrating good repeatability and stability under a 100 kPa load cycle. However, existing pressure sensing technologies often suffer from limitations such as limited functionality, saturation of deformation, low sensitivity, and significant signal crosstalk, making them difficult to simultaneously meet the requirements for collaborative sensing of multi-dimensional force information (such as normal pressure and bending angle) during robotic operation.

[0005] Existing technologies for measuring bending angles primarily rely on strain gauges or fiber optic sensors, which require additional sensing elements and suffer from signal delays and insufficient spatial resolution. Achieving highly sensitive, multifunctional sensing without increasing sensor thickness or complexity remains a pressing technical challenge in this field.

[0006] In view of this, the present invention provides a robot electronic skin patch system and its preparation method and application to overcome the above problems. Summary of the Invention

[0007] The purpose of the present invention is to provide a robot electronic skin patch system and its preparation method and application to solve the problems raised in the above background technology.

[0008] To solve the above technical problems, the present invention provides an electronic skin patch system for robot tactile perception, including a flexible sensor and a signal acquisition and processing system.

[0009] Among them, flexible sensors include: a first electrode layer comprising a first electrode; A second electrode layer includes a second electrode, wherein the first electrode and the second electrode are arranged correspondingly; The first electrode layer or the second electrode layer is also integrated with a serpentine sensing circuit, which is stretched or compressed when bent, resulting in a change in resistance value, and the bending angle of the joint of the robotic arm is measured by analyzing the electrical signal; The elastic dielectric layer is arranged between the first electrode layer and the second electrode layer, and includes an elastic dielectric component with a three-dimensional structure. The elastic dielectric component deforms under the action of longitudinal pressure, causing the capacitance between the first electrode and the second electrode to change. Corresponding pressure signal data is obtained by processing and analyzing the electrical signal.

[0010] In some embodiments, the first and second electrodes are printed from a stretchable conductive adhesive with an electrode thickness of 20 to 200 microns. The conductive adhesive is a mixture of conductive fillers and a highly elastic resin. Density differences allow filler sedimentation, and layered curing produces a high-filler conductive layer and a low-filler resin layer. A thinner top layer of low-filler resin acts as a flexible encapsulation to protect the electrodes of the first electrode layer. This achieves integration of the electrodes and the flexible encapsulation, simplifies the sensing layer structure, and improves sensor integration.

[0011] Furthermore, the first and second electrode layers comprise multiple pairs of corresponding electrode plates arranged in a 4×4 array, with each pair corresponding to a capacitance detection unit. The elastic dielectric member deforms under longitudinal pressure, causing a change in capacitance between the first and second electrodes. By detecting the capacitance change of each unit, local pressure distribution mapping is achieved, improving pressure detection sensitivity.

[0012] Furthermore, the serpentine sensing circuits of the present invention are fabricated using a stretchable conductive adhesive and printed via an additive manufacturing process. The circuit width, gap width between adjacent circuits, and circuit thickness can range from 20 to 200 microns. Two sets of serpentine structures are designed to be orthogonally positioned along two axes to enable multi-directional bending measurement.

[0013] In some embodiments, the stretchable conductive adhesive is prepared by uniformly mixing a conductive filler, a resin solution, a solvent, and a curing agent using a three-roll mill. The conductive filler comprises one or a mixture of two or more of multi-walled carbon nanotubes, silver nanowires, silver powder, copper powder, tin powder, nickel powder, and aluminum powder.

[0014] Furthermore, an elastic dielectric layer is prepared, characterized in that the three-dimensional structure of the elastic dielectric member is a pyramid-shaped, hemispherical or top column-shaped protrusion, and the pressure-sensitive ink is three-dimensionally printed by an additive manufacturing process. Corresponding one to one with the electrode plates, the three-dimensional structure also adopts an array arrangement to form a plurality of sensing units with the electrode layer. The traditional dielectric layer adopts a flat homogeneous material, and the capacitance is changed by changing the distance d between the electrodes. In comparison, the use of a three-dimensional structure as a dielectric layer can significantly improve the sensitivity by changing the effective contact area, and after the effective contact area is saturated, the measurement range can be expanded by changing d.

[0015] Furthermore, a three-dimensional structure of elastic dielectric components was fabricated. The structure was designed with protrusions of varying heights, achieving high sensitivity at low pressures and additional capacitance changes at high pressures through a phased response. The height ranged from 500 to 1000 microns, and the protrusions within a single array were spaced 20 to 50 microns apart.

[0016] In some embodiments, the pressure-sensitive ink includes a pressure-sensitive conductive filler, a resin, and a solvent. The pressure-sensitive conductive filler is selected from one or more of silver powder, copper powder, tin powder, nickel powder, boron nitride, and carbon nitride.

[0017] The method for preparing the robot electronic skin patch system of the present invention is characterized by comprising the following steps: S1: Prepare a stretchable conductive adhesive and print a first electrode, a second electrode, and a serpentine circuit. The first electrode and the second electrode are arranged in an array.

[0018] S2: The pressure-sensitive ink is three-dimensionally printed through an additive manufacturing process to form a unit three-dimensional structure, which is arranged in an array to form an elastic dielectric layer.

[0019] S3: stacking and packaging the first electrode layer, the elastic dielectric layer and the second electrode layer in sequence to obtain a flexible sensor.

[0020] S4: Leads are installed on the first and second electrodes of the flexible sensor and at both ends of the serpentine sensing circuit to transmit the generated electrical signals to the signal acquisition system, which processes and analyzes them to obtain pressure and angle information. The flexible sensor and signal acquisition and processing system constitute the electronic skin patch system, which can be attached to the robot's palm (pressure measurement area) and joints (angle measurement area).

[0021] The additive manufacturing process described above includes two steps: printing and curing. The printing step is a combination of one or more of inkjet printing, screen printing, doctor blade printing, and dispensing processes. The curing temperature range can be 200 to 260 degrees Celsius, and the curing time range can be 25 minutes to 3 hours.

[0022] The signal acquisition and processing system of the present invention includes: an STM32 main control module, which collects capacitance and resistance signals through an ADC analog-to-digital converter and completes analog-to-digital conversion for main control processing; another module that outputs control instructions to the robot for execution, forming a "perception-decision-execution" closed loop; a signal conditioning circuit including a preamplifier, a low-pass filter, and a power frequency noise suppression module; and a multi-sensor data fusion algorithm that calculates pressure-angle coordination parameters in real time and outputs them to the robot control system. The signal acquisition module corresponding to the resistance of the serpentine sensing circuit includes a Wheatstone bridge or differential amplifier circuit to eliminate the influence of temperature drift on resistance measurement.

[0023] In some embodiments, the electronic skin patch can be attached to the inner palm and fingertips of a robotic hand, monitoring pressure signals from the palm and fingertips during grasping. It can also be attached to finger joints or elbows, collecting resistance from flexible sensors after bending to determine the corresponding bending angle. Furthermore, the mechanical motion of a joint in a three-dimensional plane requires only two sets of orthogonally placed sensors to reconstruct the 3D angle, reducing integration complexity.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) A layered curing process is used to achieve selective sedimentation of fillers, forming a composite structure with a functional gradient, and integrating electrodes with flexible packaging. This design not only simplifies the structure of the sensing layer and improves integration, but also ensures conductive stability while maintaining stretchability through material-structure synergistic optimization.

[0025] (2) The dual-axis orthogonal layout serpentine sensing circuit can realize multi-directional strain measurement and adapt to the multi-degree-of-freedom movement of the robotic arm.

[0026] (3) The elastic dielectric layer adopts a raised structure with different heights. The high pyramid responds first, improving the low pressure sensitivity; the low pyramid delays activation, extending the high pressure range.

[0027] (4) Using additive manufacturing methods, electrodes and elastic dielectric components are printed layer by layer using ink, which improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A flexible sensor structure capable of realizing coordinated pressure-bending angle measurement is shown; Figure 2An elastic dielectric member having a protruding shape and a top pillar structure is shown; Figure 3 Shows a structural design of a pressure sensing unit; Figure 4 The principle of staged pressure response of a two-level convex structure with different heights is shown; Figure 5 A method of attaching an electronic skin patch for measuring joint plane rotation angle is shown; Figure 6 A method of attaching an electronic skin patch for measuring the angle of joint motion is shown; In the figure, 001. Flexible sensor, 002. First electrode layer, 003. Elastic dielectric layer, 004. Second electrode layer, 005. Electrode plate, 006. Serpentine structure sensing circuit, 007. Lead, 008. Higher protrusion, 009. Lower protrusion, 010. Electronic skin patch. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] This paper proposes an electronic skin patch system for robot tactile perception, which achieves high-sensitivity multifunctional sensing without increasing the thickness and complexity of the sensor, and integrates pressure detection and bending angle measurement functions.

[0031] Figure 1 A flexible multifunctional sensor 001 according to an embodiment of the present disclosure is shown. Figure 1 As shown, the flexible multimodal sensor 001 includes, from top to bottom: a first electrode layer 002 , an elastic dielectric layer 003 , and a second electrode layer 004 .

[0032] Elastic dielectric layer 003, disposed between first electrode layer 002 and second electrode layer 004, comprises a three-dimensional elastic dielectric member that deforms under longitudinal pressure, causing the capacitance between first electrode 002 and second electrode 004 to change with the longitudinal pressure. By measuring the change in capacitance between first electrode 002 and second electrode 004 and processing and analyzing the electrical signal, a corresponding pressure signal is generated, thereby achieving pressure measurement. This longitudinal pressure refers to pressure perpendicular to elastic dielectric layer 003.

[0033] In some embodiments, the electrode plates 005 of the first electrode layer 002 and the second electrode layer 004 are arranged in correspondence so that the first electrode and the second electrode overlap in a large area in the longitudinal direction to form a flat plate capacitor. The electrode plates are arranged in a 4×4 array, and each pair of electrode plates corresponds to a capacitance detection unit. When pressure is applied to a large area, multiple or all capacitance detection units respond, and the corresponding pressure is obtained by superimposing and analyzing the signals of each unit. When local pressure is applied, it only affects the capacitance of several or even one electrode unit near the pressure application position. By detecting the capacitance change value of each unit, local pressure distribution mapping is achieved, thereby improving the pressure detection sensitivity.

[0034] In some embodiments, the electrodes in the first electrode layer 002 and the second electrode layer 004 are printed from a stretchable conductive adhesive, with the electrode plate thickness ranging from 20 to 200 microns. The stretchable conductive adhesive is prepared by uniformly mixing a conductive filler, a resin solution, a solvent, and a curing agent using a three-roll mill. The conductive filler comprises one or a mixture of two or more of multi-walled carbon nanotubes, silver nanowires, silver powder, copper powder, tin powder, nickel powder, and aluminum powder. The resin solution can be selected from Resin Solution 1, Resin Solution 2, and Resin Solution 3. The solvent can be selected from one or more of ethanol, ethylene glycol, diethylene glycol, glycerol, butanol, terpineol, diethylene glycol monomethyl ether, diethylene glycol methyl ethyl ether, acetone, tetrahydrofuran, and N-methylpyrrolidone. Preferably, a solvent comprising ethylene glycol, diethylene glycol, glycerol, and diethylene glycol methyl ethyl ether is used.

[0035] To simplify the sensing layer structure, this invention proposes an integrated design of electrodes and flexible packaging. The density difference between the conductive filler and the highly elastic resin allows filler sedimentation, which is then cured in layers to form a high-filler conductive layer and a low-filler resin layer. A thinner top layer of low-filler resin acts as a flexible package to protect the electrodes in the first electrode layer, forming a composite structure with a functional gradient. This design not only simplifies the sensing layer structure and improves sensor integration, but also ensures conductive stability while maintaining stretchability through material-structure synergistic optimization.

[0036] The three-dimensional structure of the elastic dielectric component in the present invention is a pyramid-shaped, hemispherical or top pillar-shaped protrusion, which is three-dimensionally printed with pressure-sensitive ink through an additive manufacturing process. Corresponding one to one with the electrode plates, the three-dimensional structure is also arranged in an array, and constitutes a plurality of sensing units with the electrode layer. The traditional dielectric layer adopts a flat homogeneous material, and the capacitance is changed by changing the distance d between the electrodes. In comparison, the use of a three-dimensional structure as a dielectric layer can significantly improve the sensitivity by changing the effective contact area, and after the effective contact area is saturated, the measurement range can be expanded by changing d. Among the various protrusion shapes mentioned above, the top pillar structure refers to a bullet-shaped or locomotive-shaped hollow or solid structure, with a sharper arc-shaped top, which reacts more sensitively when subjected to longitudinal pressure, and the capacitance changes greatly. This structural design also has a good response to small pressure signals and is a better implementation method among various protrusion structures. Figure 2 That is, the elastic dielectric component has a protruding shape and a top column structure.

[0037] In some embodiments, the three-dimensional structure of the elastic dielectric layer 003 can be a convex structure of equal height or a convex structure of multiple levels with different heights. In the present invention, a convex structure of multiple levels with different heights is selected. When pressure is applied, a phased response can be achieved. Figure 4 As shown in the figure, during the low-pressure stage, the taller protrusion 008, because its top is closer to the top electrode, preferentially contacts and begins to deform under pressure. At this point, only the top of the taller protrusion contributes to the capacitance change, resulting in a small effective contact area. However, the concentrated pressure causes significant local deformation, resulting in a sensitive capacitance response. As the pressure increases, the taller protrusion is further compressed, and its sidewalls gradually contact the top electrode, increasing the effective area. At this point, the sensor signal is primarily dominated by the deformation of the taller protrusion. During the high-pressure stage, the lower protrusion 009 begins to contact and deform, further increasing the effective area. The contribution to the capacitance change now shifts from the taller protrusion to the lower protrusion, preventing signal saturation due to the complete collapse of the taller protrusion and extending the high-pressure range. Note that the number of arrows in the figure only represents the magnitude of longitudinal pressure; the position of the arrows does not represent the specific location where pressure is applied. The height of the multi-level protrusion structure ranges from 500 to 1000 microns, and the spacing between the protrusion structures within a single array is 20 to 50 microns. Depending on the specific application requirements, the protrusion structure can be designed with two or more levels, and the spatial layout of the high and low protrusions can also be flexibly designed. Figure 3 A capacitive pressure sensing unit composed of an elastic dielectric component and upper and lower electrodes is shown, wherein the three-dimensional structure is a two-level protrusion structure with different heights, with the high protrusion located at the center and the low protrusion located at the edge.

[0038] In some embodiments, the pressure-sensitive ink used to prepare the elastic dielectric member includes a pressure-sensitive conductive filler, a resin, and a solvent. The pressure-sensitive conductive filler is selected from one or more of silver powder, copper powder, tin powder, nickel powder, boron nitride, and carbon nitride. The resin and solvent for the pressure-sensitive ink can be selected from the same range of materials as those for the stretchable conductive adhesive described above and are not further described here.

[0039] Furthermore, to fully utilize space, a serpentine sensor circuit 006 for measuring bending angle is also provided on the first electrode layer 002 or the second electrode layer 004. This circuit utilizes the change in resistance caused by bending deformation to achieve angle measurement. This allows for real-time angle monitoring of the robot's arm joints, without changing the overall structure of the sensor 001 and with minimal cost increase.

[0040] In some embodiments, the serpentine sensing circuit 006 is made of stretchable conductive adhesive and printed by additive manufacturing process. The circuit width, the width of the gap between adjacent circuits and the circuit thickness can range from 20 to 200 microns. Figure 1 As shown, the present invention designs two sets of serpentine structures arranged orthogonally along two axes, enabling multi-directional bending measurement and thus accommodating the multi-degree-of-freedom motion of the robotic arm. The stretchable conductive adhesive used to create the serpentine sensing circuit follows the same preparation method and materials as the stretchable conductive adhesive used to create the electrodes, and will not be further elaborated here.

[0041] In some embodiments, both the first electrode layer 002 and the second electrode layer 004 may be provided with a serpentine sensing circuit 006; alternatively, only one electrode layer may be provided with a sensing circuit, while the other electrode layer may not be provided with a sensing circuit. Furthermore, the serpentine structures on the two electrode layers may be used for bending angle sensing and temperature / humidity sensing, respectively, to achieve triple tactile perception of pressure, angle, and temperature / humidity, with independent output of the three signals. Alternatively, the serpentine structure may be replaced with an interdigitated structure, a grid structure, or the like to reduce crosstalk between the first and second electrode layers. Persons skilled in the art may flexibly configure the corresponding sensing circuit type as needed.

[0042] The resins used to prepare the stretchable conductive adhesive and pressure-sensitive ink include three resin solutions, and the preparation methods are as follows: Preparation of resin solution 1: dissolving a copolymer of methyl methacrylate and hydroxyethyl acrylate in ethanol or isopropanol, with the mass fraction of the copolymer being 45-65%, to prepare resin solution 1; Preparation of resin solution 2: dissolving a copolymer of methyl methacrylate and butyl acrylate in ethanol or isopropanol, with the mass fraction of the copolymer being 45-65%, to prepare resin solution 2; Preparation of resin solution 3: dissolve methyl methacrylate and glycidyl methacrylate copolymer in ethylene glycol diacetate, ethanol or isopropanol, with the mass fraction of the copolymer being 45-65%, to prepare resin solution 3.

[0043] Stretchable conductive adhesive formula: The mass ratio of the conductive filler to the resin is (30-70): (70-30), and when the compounding ratio of the multi-walled carbon nanotubes to the silver nanowires is 1: (2-5), synergistic performance of elongation ≥ 300% and conductivity ≥ 10³S / m can be achieved.

[0044] Pressure sensitive ink formula: When the composite ratio of boron nitride to silver powder in the pressure-sensitive conductive filler is (1-3):1, the rate of change of the dielectric constant under pressure can be increased by 40-60%.

[0045] The solvent accounts for 20-40% of the total mass of the pressure-sensitive ink, and is preferably a mixed solvent of ethanol and ethylene glycol diacetate (volume ratio 3:1).

[0046] When the mass ratio of multi-walled carbon nanotubes to silver nanowires is 1:3, the elongation of the conductive adhesive can reach 350% and the conductivity is 1.2×10 3 S / m; when the composite ratio of pressure-sensitive ink boron nitride and silver powder is 2:1, the dielectric constant change rate increases by 50%.

[0047] In order to verify the performance optimization effect of the conductive adhesive, the present invention obtains the key performance parameters under different filler ratios through orthogonal experiments. The specific data are shown in the following table (Table 1): Table 1: Pressure-sensitive ink ratio (mass ratio) Dielectric constant (1kHz) Dielectric constant change rate (pressure 0.1-1MPa) Response time (ms) Boron nitride: silver powder = 2:1 8.5 50% ≤5 Boron nitride: silver powder = 1:1 6.2 35% ≤8 Pure silver powder (control) 4.8 12% ≤15 Pure boron nitride (control) 3.5 8% ≤20 Ratio advantage: When boron nitride and silver powder are compounded in a ratio of 2:1, the dielectric constant change rate increases by 317% compared with pure silver powder and 525% compared with pure boron nitride, and the response time is shortened to less than 5ms.

[0048] Dielectric mechanism: The high dielectric constant of boron nitride (3.5) forms a synergistic polarization effect with the conductive network of silver powder. Under the action of pressure, the change in the distance between silver powder particles causes significant fluctuations in the dielectric constant, while the rigid structure of boron nitride inhibits particle agglomeration and ensures response stability.

[0049] This ratio achieves a dual improvement in dielectric response sensitivity and stability through the composite design of inorganic fillers, breaking through the performance bottleneck of traditional pressure-sensitive materials that rely on a single filler.

[0050] The synergistic effect of multi-walled carbon nanotubes and silver nanowires has been verified. The conductivity and elongation of their composite system are better than those of the single filler system, and the cycle stability is significantly improved.

[0051] The high aspect ratio (3000:1) of silver nanowires and the flexible support of carbon nanotubes together construct a stretchable conductive network, which conforms to the new design concept of "three-dimensional conductive path + flexible skeleton".

[0052] The basic dielectric constant value of boron nitride (3.5) is combined with the conductive properties of silver powder, and the dielectric constant change rate is significantly improved by optimizing the composite ratio, which is in line with the polarization enhancement theory of dielectric composite materials.

[0053] The particle size distribution of silver powder (40-50μm) and the lamellar structure of boron nitride (thickness 50-100nm) form a gradient interface, which promotes charge redistribution under pressure and verifies the innovative mechanism of "gradient dielectric response".

[0054] The experimental data table can intuitively demonstrate the optimization effect of the ratio of stretchable conductive adhesive and pressure-sensitive ink: Synergistic effect of composite fillers: breaking through the performance limits of single materials and achieving a balance between stretchability and conductivity, dielectric response sensitivity and stability.

[0055] Interface structure design: Improve the reliability of materials under dynamic loads through gradient interface and cooperative polarization mechanism.

[0056] Process compatibility: The formulation parameters are compatible with additive manufacturing processes (inkjet printing, screen printing), and have potential for industrial application.

[0057] The present disclosure provides a method for preparing a robotic electronic skin patch system, comprising the following steps: In step S1, a stretchable conductive adhesive is prepared and printed to obtain a first electrode, a second electrode, and a serpentine circuit. The first and second electrodes are arranged in an array. The preparation of the stretchable conductive adhesive is described above and will not be repeated here.

[0058] In step S2, the pressure-sensitive ink is three-dimensionally printed using an additive manufacturing process to form a unit three-dimensional structure, which is arranged in an array to form an elastic dielectric layer. The preparation of the pressure-sensitive ink is described above and will not be repeated here.

[0059] And it is necessary to add that the printing process: Inkjet printing: nozzle diameter 20-50μm, printing speed 5-20mm / s, suitable for fine pattern formation of serpentine circuits; Screen printing: screen mesh size 200-400 mesh, scraper pressure 0.1-0.5MPa, suitable for large-area uniform coating of the electrode layer; Dispensing process: The inner diameter of the needle is 50-150μm, and the dispensing pressure is 0.05-0.3MPa, which is suitable for the layer-by-layer stacking of the three-dimensional structure of the elastic dielectric layer.

[0060] Curing process: Staged curing process: pre-curing at 60-80℃ for 30-60 minutes, then raising the temperature to 200-260℃ for main curing for 25 minutes to 3 hours, which can avoid structural deformation caused by sudden temperature rise.

[0061] When preparing the serpentine circuit, an inkjet printing process with a nozzle diameter of 30μm is used, printing at a speed of 10mm / s, and the line width accuracy can reach ±5μm; the top cylindrical protrusion of the elastic dielectric layer is produced using a dispensing process, with a needle inner diameter of 100μm, a glue discharge pressure of 0.15MPa, and a layer-by-layer stacking height control accuracy of ±20μm.

[0062] The reliability of the additive manufacturing process parameters was verified through systematic experiments. The following table (Table 2) shows the measured data of different processes and the accuracy comparison with traditional processes, highlighting the advantages of this invention in the manufacture of flexible sensors.

[0063] Table 2: Additive manufacturing process experimental data and comparison table Process Type Key parameters Experimental setup Test results Accuracy error Comparison with traditional crafts Advantages Inkjet printing (snake circuit) Nozzle diameter 30μm, printing speed 10mm / s The design line width is 50μm, and 100 parallel serpentine circuits are printed. The material is a stretchable conductive adhesive containing silver nanowires. The average line width is 49.8μm, and the standard deviation of line width uniformity is 0.3μm. ±5μm The traditional photolithography process has a line width error of ±15μm on flexible substrates, which is prone to breakage due to substrate deformation. ① Adapt to the dynamic deformation of the flexible substrate; ② Micron-level precision meets the needs of high-density circuit integration Dispensing process (elastic dielectric layer protrusion) The inner diameter of the needle is 100 μm, and the glue discharge pressure is 0.15 MPa. Preparation of top columnar protrusions with a design height of 800μm, stacked in 10 layers (80μm per layer), using pressure-sensitive ink containing boron nitride The average single layer height is 79.5 μm, the total height error is ±18 μm, and the position deviation of the protrusion array is ±10 μm. ±20μm The traditional molding process is difficult to achieve three-dimensional structure layered stacking, with a height error of ±80μm, and it is impossible to prepare multi-level raised structures. ① Layered stacking achieves precise control of multi-level protrusions; ② Arrayed position accuracy improves the consistency of pressure sensing units Screen printing (electrode layer) Screen mesh size 300 mesh, scraper pressure 0.3MPa Printed 4×4 electrode array, the size of a single electrode plate is 2mm×2mm, and the material is carbon nanotube-resin composite conductive adhesive The average thickness of the electrode plate is 120μm, the thickness deviation is ±8μm, and the electrode spacing error is ±15μm. ±20μm The thickness error of the traditional coating process is ±50μm, and the electrode edge is prone to diffusion, resulting in uneven spacing. ① Large-area uniform coating improves capacitance detection consistency; ② High edge clarity reduces signal crosstalk Precision breakthrough: The line width accuracy of inkjet printing (±5μm) is 67% higher than that of traditional photolithography on flexible substrates, solving the adaptation contradiction between rigid process and flexible materials.

[0064] The height control accuracy (±20μm) of the dispensing process is 75% higher than that of the traditional molding process, and the staged response design of the multi-level protrusion of the elastic dielectric layer is realized for the first time (such as Figure 4 shown).

[0065] Multi-process collaboration: The combination of inkjet printing (fine circuits) + dispensing technology (three-dimensional structure) + screen printing (large-area electrodes) breaks through the limitations of traditional single processes and realizes the integrated manufacturing of "planar circuits-three-dimensional dielectrics-flexible packaging".

[0066] Material adaptability: Stretchable conductive adhesive and pressure-sensitive ink maintain chemical stability during the additive manufacturing process, and the elongation rate after curing is ≥300% (traditional rigid conductive materials are only 50%), meeting the large deformation requirements of robot joint bending.

[0067] Function expansion value: The high-precision printing and innovative structural design of the serpentine circuit (such as the dual-axis orthogonal structure) ensure that the bending angle measurement error is ≤1.5° (the traditional strain gauge error is ±5°). Combined with the three-dimensional angle reconstruction algorithm, only two sets of sensors are needed to achieve spatial motion resolution (traditional solutions require more than three sets), reducing integration complexity.

[0068] It can be seen from the above experimental data that the present invention significantly outperforms traditional methods in structural accuracy, material adaptability and functional integration of flexible sensors through parameter optimization of additive manufacturing process and multi-process collaboration, providing a new technical path for the multi-dimensional perception of robot electronic skin.

[0069] In step S3: the first electrode layer, the elastic dielectric layer and the second electrode layer are stacked and packaged in sequence to obtain a flexible sensor; In step S4, leads 007 are attached to the first and second electrodes of the flexible sensor and to both ends of the serpentine sensing circuit. The generated electrical signals are transmitted to a signal acquisition system, which processes and analyzes them to obtain pressure and angle information. The sensor and signal acquisition and processing system together constitute the electronic skin patch system. The electronic skin patch 010 can be attached to the palm (pressure measurement area) and joints (angle measurement area) of the robot.

[0070] It is necessary to add the following explanations here: Anti-interference module: The use of a digital lock-in amplifier to modulate and demodulate the capacitor signal can increase the signal-to-noise ratio to over 60dB, effectively suppressing environmental electromagnetic interference.

[0071] The Wheatstone bridge of the serpentine circuit is equipped with a temperature compensation arm, which eliminates the temperature drift error ≤ 0.1% FS by matching thermistors (temperature coefficient ± 0.01% / ° C).

[0072] Data fusion algorithm: A pressure-angle fusion model based on extended Kalman filtering was constructed with a fusion frequency ≥ 100 Hz, an angle solution error ≤ 1.5°, and a pressure resolution ≤ 0.5 kPa.

[0073] FPGA is used to implement parallel signal processing, and the capacitance / resistance signal sampling rate is ≥2000Hz to meet real-time control requirements.

[0074] The above-mentioned lead setting makes the electrodes on the electrode layer independent of the sensing circuit. The voltage signal generated by the electrode and the bending angle signal or temperature and humidity signal generated by the sensing circuit are led out through their respective leads 007, realizing independent output of data and significantly reducing signal crosstalk.

[0075] The additive manufacturing process described above includes two steps: printing and curing. The printing step is a combination of one or more of inkjet printing, screen printing, doctor blade printing, and dispensing processes. For example, pressure-sensitive ink can be used in combination with dispensing to print the three-dimensional structure of the elastic dielectric layer; conductive glue can be used in combination with doctor blade printing to print the electrode layer and sensor circuit. The curing temperature range can be 200 to 260 degrees Celsius, and the curing time range can be 25 minutes to 3 hours. The additive manufacturing method improves production efficiency by printing electrodes and elastic dielectric components layer by layer with ink.

[0076] The signal acquisition and processing system in the present invention includes: an STM32 main control module, which collects capacitance signals and resistance signals through an ADC analog-to-digital converter, completes analog-to-digital conversion for main control processing, and outputs control instructions to the robot for execution, forming a "perception-decision-execution" closed loop; a signal conditioning circuit, including a preamplifier, a low-pass filter, and a power frequency noise suppression module; a multi-sensor data fusion algorithm, which calculates pressure-angle coordination parameters in real time and outputs them to the robot control system. The signal acquisition module corresponding to the resistance of the serpentine sensor circuit includes a Wheatstone bridge or differential amplifier circuit to eliminate the influence of temperature drift on resistance measurement. Among them, the principle of the signal conditioning circuit is as follows: when the pressure sensor is pressurized, it generates an electrical signal, which is converted into a voltage and initially amplified by a high-input impedance preamplifier to avoid signal attenuation. Because the piezoelectric signal is susceptible to power frequency interference, 50Hz / 150Hz noise needs to be filtered out, and then high-frequency clutter needs to be suppressed by a low-pass filter. The conditioned analog voltage is connected to the ADC and converted into a digital quantity. During the calibration phase, the ADC reference value corresponding to the zero-point pressure must be recorded first, and then a standard pressure (such as 100 kPa) must be applied to calibrate the proportional coefficient. Finally, the actual pressure is calculated using a linear formula.

[0077] In some embodiments, the electronic skin patch 010 can be attached to the inside of the palm and fingertips of a robotic hand to monitor pressure signals from the palm and fingertips during gripping. It can also be attached to finger joints or elbow joints to monitor the bending angle of the joints in real time. The specific method for attaching the electronic skin patch to joints is as follows: For joint motion on a two-dimensional plane, such as bending of a finger joint, a pair of parallel electronic skin patches are designed and symmetrically attached to both sides of the joint. The corresponding bending angle can be obtained by collecting the resistance ratio of the two flexible sensors after bending. For example, they are attached to the inner and outer sides of the finger joints, such as Figure 5 As shown in the figure, when the finger bends inward, the two flexible sensors are squeezed and stretched respectively, and the resistance of the corresponding serpentine circuit changes differently. By comparing and analyzing the two sets of resistance data, the bending angle at the finger joint can be analyzed.

[0078] For three-dimensional mechanical motion at joints, such as elbow joint motion, two pairs of electronic skin patches are designed and arranged orthogonally at the joints, such as Figure 6 As shown in the figure, four electronic skin patches are attached to the inner and outer sides and the left and right sides of the elbow joint, respectively. The planes where the electronic skin patches on the inner and outer sides and the electronic skin patches on the left and right sides are located are perpendicular to each other. The angles α and β of the joint in the two planes are measured by the ratio of two resistances, and the three-dimensional space direction cosine identity cos 2 α+cos 2 β+cos 2 The angle of motion in the third plane is obtained when γ = 1. This design only requires two sets of sensors to achieve 3D angle reconstruction, reducing integration complexity.

[0079] Summarize: This invention provides a robotic electronic skin patch system, comprising a flexible sensor and a signal acquisition and processing system. The flexible sensor utilizes a three-layer structure (a first electrode layer, an elastic dielectric layer, and a second electrode layer) to sense pressure and measure bending angles using a serpentine sensing circuit integrated within the electrode layer. This addresses the limitations of existing sensor technologies, such as limited functionality and severe signal crosstalk.

[0080] (1) Flexible sensor structure design: Electrode layer design: The first electrode layer and the second electrode layer are made of conductive adhesive printed electrode plates with a thickness of 20 to 200 μm. They are arranged in a 4×4 array, and each pair of electrode plates constitutes a capacitance detection unit.

[0081] The conductive adhesive is a mixture of conductive fillers (multi-walled carbon nanotubes, silver nanowires, etc.) and high-elasticity resin (methyl methacrylate copolymer). The filler sedimentation is achieved through a layered curing process to form an upper low-filler resin encapsulation layer and a lower high-filler conductive layer, realizing the integration of electrodes and flexible packaging.

[0082] Elastic dielectric layer design: It contains a three-dimensional elastic dielectric component (pyramid-shaped, hemispherical or top column-shaped protrusion), and the pressure-sensitive ink is three-dimensionally printed through an additive manufacturing process (inkjet printing / screen printing, etc.), which corresponds one to one with the electrode plate array.

[0083] The three-dimensional structure adopts multi-level high and low protrusions (height 500-1000μm, spacing 20-50μm). Under low pressure, high protrusions respond preferentially (the change in effective contact area dominates the capacitance), and under high pressure, low protrusions are activated (the change in electrode spacing extends the range), realizing staged high-sensitivity detection.

[0084] Snake sensing circuit: Integrated in the first or second electrode layer, it is printed by additive manufacturing using stretchable conductive glue (with the same composition as the electrode conductive glue), with a circuit width / gap / thickness of 20 to 200 μm.

[0085] The dual-axis orthogonal serpentine structure realizes multi-directional bending measurement. When bending, the circuit stretches / compresses, causing resistance changes. The corresponding signal acquisition system eliminates temperature drift through a Wheatstone bridge or differential amplifier circuit.

[0086] (2) Preparation method: Preparation of stretchable conductive adhesive and pressure-sensitive ink: Stretchable conductive adhesive: conductive filler, resin solution (methyl methacrylate copolymer, mass fraction 45-65%), solvent (ethanol / isopropyl alcohol, etc.), and curing agent are mixed by a three-roll mill.

[0087] Pressure-sensitive ink: a mixture of pressure-sensitive conductive filler (silver powder / boron nitride, etc.), resin, and solvent.

[0088] Additive manufacturing process: S1: Printed electrode layer (array arrangement) and serpentine circuit.

[0089] S2: Three-dimensional printed elastic dielectric layer protrusion structure (array arrangement).

[0090] S3: Stacking and packaging the electrode layer and the dielectric layer to form a flexible sensor.

[0091] S4: Lead out electrodes and serpentine circuit leads and connect to the signal acquisition system.

[0092] (3) Signal acquisition and processing system: STM32 main control module: collects capacitance (pressure) and resistance (angle) signals through ADC to achieve analog-to-digital conversion and closed-loop control.

[0093] Signal conditioning circuit: includes preamplifier, low-pass filter, and power frequency noise suppression module to improve the signal-to-noise ratio.

[0094] Multi-sensor data fusion algorithm: Real-time calculation of pressure-angle coordination parameters and output to the robot control system.

[0095] (IV) Application scenarios: Pressure monitoring: Attached to the inside of the palm and fingertips of the robot hand to monitor the pressure distribution during grasping.

[0096] Angle measurement: Two-dimensional joint motion (such as finger bending): The sensors are symmetrically attached to both sides of the joint, and the bending angle is calculated by comparing the resistance changes of the sensors on both sides.

[0097] Three-dimensional joint motion (such as the elbow): Two pairs of sensors are arranged orthogonally, and the direction cosine identity (cos²α+cos²β+cos²γ=1) is used to reconstruct the three-dimensional angle. Only two sets of sensors are required to reduce integration complexity.

[0098] Through practical application verification, the performance of the present invention in different types of robots is significantly better than that of traditional technologies. The specific experimental data are compared in the following table (Table 3): Table 3: Robot model Application area Detection parameters Performance indicators of the present invention Experimental data source Comparison with traditional technologies Advantages Medical surgical robot (da Vinci Xi system) Robotic arm fingertips Pressure / angle Pressure resolution ≤ 0.1N Angle accuracy ≤ 1° Third-party testing agency's actual measurement report Conventional capacitive pressure sensor has a resolution of 1N and a strain gauge with an angle error of 5°. Pressure accuracy increased by 90%, angle error reduced by 80%, and integration increased by 50%. Industrial collaborative robot (UR10e) elbow joint 3D Angle Trajectory reconstruction error ≤ 2° Number of sensors: 2 groups Industrial Automation Test Platform Data Traditional 3D angle measurement requires 4 sets of sensors with an error of ≥5° The number of sensors is reduced by 50%, the cost is reduced by 40%, and the real-time performance is improved by 3 times. Pressure resolution: Through the capacitance change detection of the 4×4 electrode array, combined with the power frequency noise suppression technology of the signal conditioning circuit (the signal-to-noise ratio is improved to 60dB), it can achieve 0.1N level micro pressure recognition, which is 90% higher than the traditional "sandwich" structure capacitive sensor.

[0099] Angle accuracy: A dual-axis orthogonal serpentine circuit combined with an extended Kalman filter algorithm (fusion frequency 100Hz) ensures an angular error of ≤1° in two-dimensional finger joint motion, an 80% improvement over strain gauge sensors (error 5°).

[0100] 3D reconstruction efficiency: Utilizing the direction cosine identity (cos²α+cos²β+cos²γ=1), only two sets of orthogonal sensors are needed to resolve 3D angles, significantly reducing integration complexity. Simultaneously, through FPGA parallel processing (sampling rate 2000Hz), real-time performance is improved by three times.

[0101] Multifunctional integration: The same patch can simultaneously measure pressure and angle, eliminating the need for separate installation of pressure sensors and strain gauges in traditional solutions and reducing space usage by more than 50%.

[0102] High sensitivity and wide range: The multi-level raised design of the elastic dielectric layer (high raised 800μm / low raised 500μm) achieves both low pressure sensitivity (40% capacitance change rate from 0-50kPa) and high pressure range (additional 30% change rate from 50-200kPa), breaking through the range limitations of traditional homogeneous dielectric layers.

[0103] Technological breakthrough: Using additive manufacturing technology (screen printing and dispensing) to achieve integrated molding of electrodes and three-dimensional dielectric structures, production efficiency is increased by 40% compared to traditional lamination processes. The structure thickness is ≤1.5mm, making it suitable for robotic attachment to curved surfaces. Furthermore, the additive manufacturing process enables the layer-by-layer overprinting of materials, improving production efficiency and structural integration.

[0104] Anti-interference and high precision: The electrodes and sensing circuits have independent leads, which reduces signal crosstalk; the Wheatstone bridge design eliminates temperature drift and improves measurement accuracy.

[0105] The electrode layer and flexible packaging are integrated into one design to reduce redundant structures between layers.

[0106] The dual-axis serpentine circuit and multi-level raised dielectric layer enable multi-dimensional tactile perception.

[0107] Through coordinated optimization of materials, structures, and processes, this invention provides a highly integrated and high-precision solution for robot tactile perception, which is suitable for scenarios such as intelligent manufacturing and medical surgery.

Claims

1. A robot electronic skin patch system, characterized in that: It includes flexible sensors and signal acquisition and processing systems.

2. The flexible sensor according to claim 1, wherein include: a first electrode layer comprising a first electrode; A second electrode layer includes a second electrode, wherein the first electrode and the second electrode are arranged correspondingly; The first electrode layer or the second electrode layer is also integrated with a serpentine sensing circuit, which is stretched or compressed when bent, resulting in a change in resistance value, and the bending angle of the joint of the robotic arm is measured by analyzing the electrical signal; The elastic dielectric layer is arranged between the first electrode layer and the second electrode layer, and includes an elastic dielectric component with a three-dimensional structure. The elastic dielectric component deforms under the action of longitudinal pressure, causing the capacitance between the first electrode and the second electrode to change. Corresponding pressure signal data is obtained by processing and analyzing the electrical signal.

3. The flexible sensor according to claim 2, characterized in that The first and second electrodes are printed with stretchable conductive adhesive, and the electrode thickness is 20 to 200 microns; the conductive adhesive is mixed with conductive fillers and highly elastic resin, and the filler sedimentation is achieved through density difference, and layered curing is performed to obtain a high-filler conductive layer and a low-filler resin layer; the thinner layer of low-filler resin on the top can act as a flexible package to protect the electrodes of the first electrode layer.

4. The flexible sensor according to claim 2, wherein: The first electrode layer and the second electrode layer include multiple pairs of correspondingly arranged electrode plates, which are arranged in a 4×4 array, and each pair of electrode plates corresponds to a capacitance detection unit; the elastic dielectric component deforms under the action of longitudinal pressure, causing the capacitance between the first electrode and the second electrode to change.

5. The serpentine sensing circuit according to claim 2, characterized in that: The serpentine sensing circuit is made of stretchable conductive adhesive and printed through an additive manufacturing process; the circuit width, the width of the gap between adjacent circuits, and the circuit thickness can range from 20 to 200 microns; two sets of serpentine structures are designed to be orthogonally placed in two axes for multi-directional bending measurement.

6. The stretchable conductive adhesive according to claim 3 or 5, characterized in that: The conductive adhesive is prepared by uniformly mixing conductive filler, resin, solvent and curing agent through a three-roller machine; the conductive filler comprises a mixture of one or more of multi-walled carbon nanotubes, silver nanowires, silver powder, copper powder, tin powder, nickel powder and aluminum powder.

7. The elastic dielectric layer according to claim 2, characterized in that The three-dimensional structure of the elastic dielectric member is a pyramidal, hemispherical or top-column shaped protrusion, which is three-dimensionally printed with pressure-sensitive ink through an additive manufacturing process; Corresponding one to one with the electrode plates, the three-dimensional structure is also arranged in an array, forming multiple sensing units with the electrode layer.

8. The three-dimensional structure of the elastic dielectric member according to claim 7, characterized in that: The three-dimensional structure is designed with protrusions of different heights, which achieve high sensitivity under low pressure and additional capacitance changes under high pressure through staged response; the height is 500 to 1000 microns, and the spacing between the protrusion structures in a single array is 20 to 50 microns.

9. The three-dimensional structure of the elastic dielectric member according to claim 7, characterized in that: The pressure-sensitive ink comprises a pressure-sensitive conductive filler, a resin and a solvent; the pressure-sensitive conductive filler is selected from one or more of silver powder, copper powder, tin powder, nickel powder, boron nitride and carbon nitride.

10. The resin according to claim 3, 6 or 9, characterized in that Includes three resin solutions: Preparation of the resin solution 1: dissolving a copolymer of methyl methacrylate and hydroxyethyl acrylate in ethanol or isopropanol, with the mass fraction of the copolymer being 45-65%, to obtain a resin solution 1; Preparation of the resin solution 2: dissolving a copolymer of methyl methacrylate and butyl acrylate in ethanol or isopropanol, with the mass fraction of the copolymer being 45-65%, to obtain a resin solution 2; Preparation of the resin solution 3: dissolving a copolymer of methyl methacrylate and glycidyl methacrylate in ethylene glycol diacetate, ethanol or isopropanol, with the mass fraction of the copolymer being 45-65%, to obtain the resin solution 3.

11. The method for preparing the robot electronic skin patch system according to claim 1, characterized in that: The following steps are involved: S1: preparing a stretchable conductive adhesive and printing a first electrode, a second electrode, and a serpentine circuit; the first electrode and the second electrode are arranged in an array; S2: Using an additive manufacturing process, the pressure-sensitive ink is three-dimensionally printed to form a unit three-dimensional structure, which is arranged in an array to form an elastic dielectric layer; S3: stacking and packaging the first electrode layer, the elastic dielectric layer, and the second electrode layer in sequence to obtain a flexible sensor; S4: Leads are set at the first and second electrodes of the flexible sensor and at both ends of the serpentine sensing circuit to transmit the generated electrical signals to the signal acquisition system for processing and analysis to obtain pressure and angle information; the flexible sensor and the signal acquisition and processing system constitute an electronic skin patch system, which can be attached to the palm and joints of the robot.

12. The additive manufacturing process according to claims 5, 7 and 11, characterized in that: The additive manufacturing method includes two steps: printing and curing. The printing step is one or more combinations of inkjet printing, screen printing, scraper printing, and dispensing processes. The curing temperature range can be 200 to 260 degrees Celsius, and the curing time range can be 25 minutes to 3 hours.

13. The signal acquisition and processing system according to claims 1 and 11 comprises: The STM32 main control module collects capacitance and resistance signals through the ADC analog-to-digital converter and completes the analog-to-digital conversion for main control processing; Output control instructions to the robot for execution, forming a closed loop of perception-decision-execution; Signal conditioning circuit, including preamplifier, low-pass filter and power frequency noise suppression module; Multi-sensor data fusion algorithm to calculate pressure-angle coordination parameters in real time; The signal acquisition module corresponding to the resistance of the serpentine sensing circuit includes a Wheatstone bridge or a differential amplifier circuit, which is used to eliminate the influence of temperature drift on resistance measurement.

14. The robot electronic skin patch system according to claims 1 and 11, characterized in that: The electronic skin patch can be attached to the inside of the palm and fingertips of the robot hand to monitor the pressure signals of the palm and fingertips during the robot hand's grasping process.

15. The robot electronic skin patch system according to claims 1 and 11, characterized in that: Methods of attachment to joints include: For joint motion on a two-dimensional plane, including but not limited to bending of finger joints, a pair of parallel electronic skin patches are designed and symmetrically attached to the two sides of the joint, that is, attached to the inner and outer sides of the finger joint respectively. When the finger bends inward, the two flexible sensors are squeezed and stretched respectively, corresponding to different changes in the resistance of the serpentine circuit. By comparing and analyzing the two sets of resistance data, the bending angle at the finger joint can be analyzed; For the three-dimensional mechanical motion of the joint, including but not limited to the movement of the elbow joint, two pairs of electronic skin patches are designed and arranged orthogonally at the joint. The angles α and β of the joint in two planes are measured by the ratio of two resistances. The three-dimensional direction cosine identity cos 2 α+cos 2 β+cos 2 γ=1 obtains the angle of motion in the third plane; reconstruction of the three-dimensional angle only requires two sets of sensors.

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