A robotic bionic skin and a method of making the same

Abstract

This application discloses a robotic bionic skin and its preparation method, belonging to the field of robotic skin technology. The robotic bionic skin includes a base layer, a bionic skin surface layer, and an elastic heat dissipation layer disposed between the two. The elastic heat dissipation layer is a wound structure formed by 3D printing of elastic material, including a first dense wound layer, a central heat dissipation wound layer, and a second dense wound layer stacked sequentially. The wound structure is formed by bending and winding continuous elastic wire, with bonding nodes formed by the adhesion of semi-molten wire during the 3D printing process. By controlling parameters such as the relative density of each dense layer and the central heat dissipation layer, wire diameter, bending radius, and winding direction, it possesses elastic deformation capabilities, adapting to repeated joint movements, improving motion realism, wear resistance, fatigue resistance, and other properties, extending lifespan, and rapidly dissipating heat to stabilize operating temperature.

Description

Technical Field

[0001] This application relates to the field of robotic skin technology, and in particular to a robotic bionic skin and its preparation method. Background Technology

[0002] With the rapid iteration of robotics technology, especially the widespread adoption of humanoid robots, higher demands are being placed on the overall performance of their outer coverings (i.e., bionic skin). Bionic skin not only needs to possess a soft touch and elastic deformation capability similar to human skin to enhance the realism of interaction, but also needs to take into account mechanical cushioning protection, efficient heat dissipation, long-term durability, and multi-functional sensing capabilities.

[0003] Currently, traditional robot outer layers mostly use rigid shells or ordinary flexible polymer materials. Rigid shells lack elastic deformation capabilities, resulting in low motion realism and failing to provide effective mechanical cushioning. While ordinary flexible materials (such as silicone and ordinary rubber) improve tactile feedback to some extent, their wear resistance, fatigue resistance, and environmental aging resistance are insufficient. Under conditions of repetitive robot joint movements and temperature cycling, existing robot outer skins exhibit significant deficiencies in elastic deformation, fatigue aging resistance, and heat dissipation reliability, making them prone to cracking, permanent deformation, swelling, and other failures, leading to a shortened service life.

[0004] Therefore, there is an urgent need to develop a robotic bionic skin that combines biomimetic performance, high durability, efficient heat dissipation, and expandable sensing capabilities to overcome the shortcomings of existing technologies. Summary of the Invention

[0005] This application addresses the challenge of existing robotic bionic skins in simultaneously achieving a flexible feel, elastic deformation capability, and efficient heat dissipation. It provides a robotic bionic skin and its fabrication method. The bionic skin comprises a base layer, a bionic skin surface layer, and an elastic heat dissipation layer disposed between the two. The elastic heat dissipation layer is a three-layer wound structure formed by 3D printing of elastic material. By limiting the thickness ratio and relative density of the dense layer and the central layer, the densely wound layers on both sides form a dense surface to increase bonding nodes, effectively resisting large deformations (skin effect) during robot movement and preventing filament damage or deformation beyond the skin surface. The central heat dissipation wound layer is relatively loose, providing ample heat dissipation space and airflow, enabling rapid and uniform heat conduction and dissipation. This approach simultaneously achieves the flexible feel, high durability, and efficient heat dissipation performance of the bionic skin. The technical solution provided by this application is as follows: On one hand, this application provides a robotic bionic skin, comprising: Matrix layer; Bionic skin surface layer; and An elastic heat dissipation layer is disposed between the substrate layer and the bionic skin surface layer, comprising a first dense winding layer, a central heat dissipation winding layer and a second dense winding layer stacked sequentially; The elastic heat dissipation layer is a winding structure formed by 3D printing of elastic material. The winding structure is formed by bending, winding and interlacing continuous elastic wires. The continuous elastic wires can be solid or hollow. The hollow part of the hollow wire is used to contain gas or liquid media. The continuous elastic wires are provided with bonding nodes, and the distance between adjacent bonding nodes is 1mm to 20mm. The bonding nodes are formed by the continuous elastic wires that are in a semi-molten state or have uncured surfaces during the 3D printing process and are bonded together. The thickness of the first dense winding layer and the second dense winding layer each independently accounts for 5% to 20% of the total thickness of the elastic heat dissipation layer, and their relative densities are each independently 20% to 80%, wherein the relative density is the ratio of the total volume of the continuous elastic wire in the layer to the total volume of the layer. The relative density of the central heat-dissipating winding layer is less than the relative density of the first dense winding layer and the second dense winding layer; The diameter D of the continuous elastic wire is 0.8mm~3.0mm, and the bending radius R of its bending winding path satisfies R≥5D; The angle between the bending and winding direction of the continuous elastic wire and the plane where the matrix layer is located is 0°~46°; The material of the continuous elastic wire is selected from one or more of thermoplastic polyurethane, polyethylene, polyolefin elastomer, and thermoplastic polyester elastomer; The 3D printing process is selected from at least one of stereolithography photopolymerization 3D printing technology, fused deposition modeling, photopolymerization jetting technology, and sintering.

[0006] In some preferred embodiments, the relative densities of the first dense winding layer and the second dense winding layer are each independently 70% to 80%, and the relative density of the central heat-dissipating winding layer is 20% to 70%.

[0007] In some preferred embodiments, the robotic bionic skin includes jointed regions and non-jointed regions; The bending radius R1 of the continuous elastic wire located in the joint region satisfies R1≥7D and R1≥1.1R2, where R2 is the bending radius of the continuous elastic wire in the non-joint region.

[0008] In some preferred embodiments, the continuous elastic wire is a hollow wire, the material of the elastic wire is thermoplastic polyurethane, and the hollow wire has embedded microchannels inside.

[0009] In some preferred embodiments, a fluorinated liquid is introduced into the embedded microchannel as a heat dissipation medium. The flow velocity of the fluorinated liquid in the embedded microchannel is 0.1 m / s to 0.4 m / s, the flow Reynolds number is less than 2000, and the system operating pressure is ≤0.15 MPa.

[0010] In some preferred embodiments, a liquid cooling circulation system is also included, which is connected to the embedded microchannel and includes a micropump, a semiconductor thermostat module, and pipelines, wherein the pipelines and the embedded microchannels together form a circulation loop. The semiconductor thermostatic module includes a Peltier thermoelectric cooler, a temperature sensor, and a control unit. The temperature sensor is embedded in the surface layer of the bionic skin, and the control unit is used to adjust the current and power of the Peltier thermoelectric cooler according to the feedback signal of the temperature sensor to switch between cooling and heating modes.

[0011] In some preferred embodiments, the outer diameter D1 of the hollow wire is 1.0 mm to 3.0 mm; The wall thickness t of the microchannel of the hollow wire satisfies the following conditions: t / D1≥0.25 in the static region, t / D1≥0.35 in the bending region, t / D1≥0.45 near the joint, and t≥0.3mm; The minimum distance s1 from the embedded microchannel to the outer surface of the bionic skin surface layer is ≥0.8mm, and the minimum distance s2 from the microchannel to the interface between the substrate layer and the elastic heat dissipation layer is ≥1.0mm; at the robot joint and foot, the minimum distance s3 from the embedded microchannel to the surface is ≥1.5mm.

[0012] In some preferred embodiments, the Shore A hardness of the biomimetic skin surface layer is 50-60, and the thickness is 1mm-10mm; The elastic heat dissipation layer has a Shore hardness of 75-90 and a thickness of 5mm-50mm.

[0013] On the other hand, this application also provides a method for preparing robotic bionic skin, including the following steps: (1) Matrix layer formation step: providing or forming a matrix layer; (2) Preparation steps of the elastic heat dissipation layer: (2a) Elastic granule preparation: Elastic granules are prepared by prepolymer method or melt blending method, wherein the material of the elastic granules is selected from one or more of thermoplastic polyurethane, polyethylene, polyolefin elastomer, and thermoplastic polyester elastomer; (2b) 3D printing molding: Using 3D printing molding equipment, the elastic granules are heated and melted and then extruded through a nozzle to form a continuous elastic filament. The nozzle is controlled to move relative to the molding substrate so that the continuous elastic filament is deposited layer by layer on the substrate layer according to a preset bending and winding path, forming a first dense winding layer, a central heat dissipation winding layer and a second dense winding layer in sequence to obtain an elastic heat dissipation layer. (3) Bionic skin surface layer formation step: A bionic skin surface layer is formed on the elastic heat dissipation layer.

[0014] In some preferred embodiments, the elastic granules are thermoplastic polyurethane granules, which are prepared using a prepolymer method, including the following steps: Polytetrahydrofuran ether diol was reacted with 4,4'-diphenylmethane diisocyanate to generate a prepolymer, wherein the isocyanate group (NCO) content in the prepolymer was controlled to be 4.5 wt%~6.5 wt%. Then, 1,4-butanediol is added to carry out a chain extension reaction, and the reaction temperature is controlled at 75℃~85℃. After vacuum degassing, the product is granulated to obtain thermoplastic polyurethane granules. The thermoplastic polyurethane granules were melt-blended with functionalized graphene oxide to obtain a thermoplastic polyurethane composite material with a functionalized graphene oxide content of 0.5wt%~3wt%. In the 3D printing molding step, the thermoplastic polyurethane composite material is heated and melted and then extruded to form a continuous thermoplastic polyurethane filament. The nozzle outlet temperature is 85℃~330℃, the temperature of the molding substrate is 41℃~60℃, and the relative moving speed between the nozzle and the molding substrate is 31mm / s~76mm / s.

[0015] In some preferred embodiments, the thermoplastic polyurethane granules include soft segments and hard segments; The soft segment is polytetrahydrofuran ether diol, with a number-average molecular weight of 2000 g / mol to 4000 g / mol, and accounts for 60% to 75% of the total mass of the thermoplastic polyurethane granules. The hard segment is the reaction product of 4,4'-diphenylmethane diisocyanate and 1,4-butanediol, accounting for 22% to 28% of the total mass of the thermoplastic polyurethane granules, and the molar ratio of isocyanate groups to hydroxyl groups (NCO / OH) is 1.02 to 1.06. The thermoplastic polyurethane granules also contain an additive system, which, based on the total mass of the thermoplastic polyurethane granules, includes 0.3wt% to 0.8wt% of antioxidant, 0.2wt% to 0.5wt% of metal ion scavenger, and 0.1wt% to 0.3wt% of ultraviolet absorber.

[0016] In some preferred embodiments, the functionalized graphene oxide is carboxyl-modified graphene oxide or amino-modified graphene oxide, with a sheet diameter of 5 μm to 10 μm and a thickness of 3 nm to 8 nm.

[0017] In some preferred embodiments, the preparation of the thermoplastic polyurethane composite material includes the following steps: Functionalized graphene oxide was ultrasonically dispersed in N,N-dimethylformamide solvent at an ultrasonic power of 400W~600W for 20min~40min to obtain a dispersion. The dispersion was melt-blended with a portion of the thermoplastic polyurethane granules and extruded and granulated to obtain a masterbatch with a functionalized graphene oxide content of 10wt%~15wt%. The masterbatch is then melt-blended with the remaining thermoplastic polyurethane granules and diluted to a functionalized graphene oxide content of 0.5wt%~3wt% to obtain the thermoplastic polyurethane composite material.

[0018] In some preferred embodiments, during the 3D printing molding step, when preparing hollow filaments, a ring-shaped printing nozzle is used to print the hollow filaments, or a coaxial dual-nozzle system is used to simultaneously extrude elastic granules and soluble sacrificial materials, wherein the soluble sacrificial materials form microchannel core materials. After molding, the soluble sacrificial material is removed by washing with water to form an embedded microchannel; The soluble sacrificial material is a copolymer of polyvinyl alcohol or butanediol.

[0019] By adopting the above technical solution, the robotic bionic skin and its preparation method provided in this application have the following beneficial effects: This application employs a three-layer structure design for the elastic heat dissipation layer. The two densely wound layers on both sides provide a dense surface with a thickness ratio of 5%–20% and a relative density of 20%–80%, increasing the number of bonding nodes between the elastic threads. This effectively resists the skin-like effect caused by large surface deformation during robot movement, preventing damage to the elastic threads or internal thread deformation exceeding the skin surface. Simultaneously, the central heat dissipation winding layer has a lower relative density than the two densely wound layers, being more loosely structured and providing ample heat dissipation space and airflow, enabling rapid and uniform heat conduction and dissipation. Furthermore, the diameter of the elastic threads is limited to 0.8 mm–3.0 mm. The bending and winding radius R≥5D and the angle between the winding direction and the plane of the substrate layer are 0°~46° to avoid problems such as entanglement, twisting, fatigue and fracture caused by large-span winding, thereby improving the overall fatigue resistance and large deformation capacity of the elastic heat dissipation layer. By forming bonding nodes with a spacing of 1mm~20mm through the mutual contact and adhesion of semi-molten or uncured filaments during the 3D printing process, a stable winding layer structure is formed, which enhances the bonding force between filaments. This allows the bionic skin to have both the soft touch and elastic deformation capacity of human skin, adapting to the repeated movement of robot joints, and significantly improving wear resistance, fatigue resistance, aging resistance and motion realism.

[0020] Preferably, this application uses hollow wires embedded with microchannels in conjunction with a liquid cooling circulation system to form a highly efficient heat dissipation and constant temperature control system, which quickly removes internal heat, stabilizes the robot's operating temperature, and extends the service life of the bionic skin and the robot's core components. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of the structure of the solid linear elastic heat dissipation layer provided in the embodiments of this application; Figure 2 A schematic diagram of the hollow linear elastic heat dissipation layer provided in an embodiment of this application; Figure 3 A schematic diagram of the hollow linear elastic heat dissipation layer provided in an embodiment of this application; Figure 4 This is a schematic diagram of the structure of the hollow wire bonding node provided in the embodiment of this application.

[0023] The following is supplementary explanation of the attached figures: 1-Hollow wire; 2-Bending radius; 3-Angle between the bending and winding direction of the continuous elastic wire and the plane of the base layer; 4-Bond joint. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0025] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of this application. In the description of this application, it should be understood that the terms "upper," "lower," "top," "bottom," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein.

[0026] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included. For example, a specified range from “1 to 10” should be considered to include any and all subranges between the minimum value 1 and the maximum value 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0027] This application provides a robotic bionic skin, including a base layer, a bionic skin surface layer, and an elastic heat dissipation layer.

[0028] The matrix layer, which serves as the supporting framework for biomimetic skin, can be made of metallic materials, polymeric materials, or composite materials.

[0029] The surface layer of the biomimetic skin is made of an elastic material, which can be the same as or different from the elastic heat dissipation layer. Specifically, it can be selected from one or more of thermoplastic polyurethane (TPU), polyethylene (PE), polyolefin elastomer (POE), and thermoplastic polyester elastomer (TPEE), with thermoplastic polyurethane (TPU) being preferred.

[0030] An elastic heat dissipation layer is disposed between the substrate layer and the biomimetic skin surface layer, comprising a first dense winding layer, a central heat dissipation winding layer and a second dense winding layer stacked sequentially.

[0031] The elastic heat dissipation layer is a winding structure formed by 3D printing of elastic material. During the bending and winding process, the elastic wires interweave back and forth, forming several bonding nodes 4 on the continuous elastic wires, such as... Figure 4 As indicated by the elliptical circle markings. The spacing between adjacent bonding nodes 4 is 1mm~20mm, thus forming a stable layer structure. Understandably, bonding nodes 4 are formed when partially molten or uncured elastic filaments come into contact with each other during the bending and winding process of the elastic filament 3D printing equipment. Due to the certain viscosity of the partially molten or uncured state, they adhere to form bonding nodes 4.

[0032] The continuous elastic wire can be a solid wire or a hollow wire 1; the hollow structure inside the hollow wire 1 is used to contain a gaseous medium or a liquid heat dissipation medium to achieve passive heat dissipation or active liquid cooling heat dissipation, respectively; among which, the gaseous medium can be air, inert gas, etc.

[0033] The thickness of the first and second densely wound layers each independently accounts for 5% to 20% of the total thickness of the elastic heat dissipation layer, and their relative densities are each independently 20% to 80%. The relative density is defined as the ratio of the total volume of the continuous elastic wires within the layer to the total volume of the layer. The remaining space within the layer, excluding the wires, forms gas flow channels to enhance air convection heat dissipation. By rationally setting the thickness and relative density of the first and second densely wound layers, a relatively dense surface structure can be formed, increasing the number of bonding nodes 4 between the continuous elastic wires. This effectively prevents excessive deformation and wire damage of the continuous elastic wires during robot movement, as well as damage to the internal elastic wires caused by deformation exceeding the surface of the bionic skin. Simultaneously, due to the large deformation of the surface layer of the elastic heat dissipation layer (skin effect), the bonding nodes 4 experience greater stress (tension, torsion, etc. compared to the center or inner layers). Sufficient bonding nodes 4 can enhance the surface structure's resistance to large deformations.

[0034] The relative density of the central heat-dissipating winding layer is less than that of the first and second dense winding layers, and it is looser than the first and second dense winding layers on both sides, so as to provide sufficient heat dissipation space and ensure sufficient airflow, thereby facilitating the rapid and uniform conduction and dissipation of heat.

[0035] The diameter D of the continuous elastic wire is 0.8mm~3.0mm, and the bending radius 2R of its bending and winding path satisfies R≥5D. This helps to avoid problems such as large-span winding of continuous elastic wire, easy entanglement, twisting, fatigue fracture, etc., and improves the overall fatigue resistance of the elastic heat dissipation layer, while also having a large deformation capacity.

[0036] The angle between the bending and winding direction of the continuous elastic wire and the plane of the substrate layer is 0° to 46°. The bending and winding direction of the elastic wire can be parallel to the plane of the substrate layer or at a certain angle to the plane, but the angle range must be strictly limited to avoid problems such as easy damage to the wire, reduced deformation resistance and tensile strength of each layer of the elastic heat dissipation layer during large bending deformation due to excessively steep winding direction or even perpendicular to the plane of the substrate layer.

[0037] The continuous elastic filament is made of one or more of thermoplastic polyurethane (TPU), polyethylene (PE), polyolefin elastomer (POE), and thermoplastic polyester elastomer (TPEE), with thermoplastic polyurethane (TPU) being preferred. All of these materials possess excellent elasticity, flexibility, abrasion resistance, and moldability, perfectly meeting the core requirements of robotic bionic skin for humanoid touch, structural strength, and long-term service reliability. Single materials or a combination of materials can be flexibly selected based on the specific application scenario of the robot.

[0038] The 3D printing method is selected from at least one of stereolithography photopolymerization 3D printing (SLA), fused deposition modeling (FDM), photopolymerization jetting technology, and sintering. The appropriate 3D printing method can be flexibly selected based on the characteristics of the elastic material, the complexity of the winding structure, and the required molding precision, enabling the integrated molding of complex winding structures and embedded flow channel structures.

[0039] In some preferred embodiments, both the first and second dense winding layers are made of solid wire, while the central heat-dissipating winding layer is made of hollow wire 1. This design effectively improves the bending resistance and structural stability of the outer layer of the elastic heat-dissipating layer, while reducing the risk of leakage caused by the hollow wire 1 breaking under stress. Furthermore, the central hollow structure can better accommodate the heat dissipation medium, enhancing the heat dissipation effect in the central area. It should be noted that the type of wire used in the above three-layer winding structure is not strictly limited; it can be configured to use either all solid wire or all hollow wire 1, depending on the actual application requirements. Specifically, as... Figure 1As shown, the three-layer winding structure can all be made of solid wire; as Figure 2 and Figure 3 As shown, the three-layer winding structure can also be entirely composed of hollow wire 1, wherein, Figure 3 The topmost oval circle marks the end of the hollow wire 1, the upper left oval circle marks the bending radius 2 of the continuous elastic wire bending and winding path, and the oval circle near the middle area marks the angle between the bending and winding direction of the continuous elastic wire and the plane where the base layer is located, so as to clearly illustrate each key structural parameter.

[0040] In some preferred embodiments, the relative densities of the first and second dense winding layers are each independently 70% to 80%, and the relative density of the central heat-dissipating winding layer is 20% to 70%. By increasing the relative density of the first and second dense winding layers, it is beneficial to further increase the bonding nodes 4 between the continuous elastic wires on both sides of the central heat-dissipating winding layer, avoiding excessive deformation of the continuous elastic wires during robot movement, which could damage the wires. Internal wire deformation beyond the skin surface is prone to damage. Due to the large deformation (skin effect) of the elastic heat-dissipating layer surface, the bonding nodes 4 are subjected to greater forces (tension, torsion, etc. compared to the center or inner layer). Sufficient connection nodes between the continuous elastic wires are necessary to ensure the ability to resist large deformations and enhance load capacity. The central heat-dissipating winding layer uses a relatively low density, which is conducive to the rapid and uniform conduction and dissipation of heat and improves flexibility.

[0041] In some preferred embodiments, the robotic bionic skin includes jointed regions and non-jointed regions; The bending radius 2R1 of the continuous elastic wire located in the joint region satisfies R1≥7D and R1≥1.1R2, where R2 is the bending radius 2 of the continuous elastic wire in the non-joint region. By increasing the bending radius 2 of the joint region, the deformation capacity of the joint region is increased, the fatigue resistance of the joint region is improved, and the fatigue resistance of different regions tends to be consistent.

[0042] In some preferred embodiments, the continuous elastic wire is a hollow wire 1, and the material of the elastic wire is thermoplastic polyurethane (TPU). The hollow wire 1 forms an embedded microchannel, which can be used to circulate liquid heat dissipation medium, further improving the active heat dissipation efficiency of the elastic heat dissipation layer. At the same time, the elasticity and wear resistance of the TPU material can ensure the sealing and structural integrity of the microchannel structure during the robot's movement.

[0043] In some preferred embodiments, a fluorinated liquid (such as 3M Novec / Fluorinert) is introduced into the embedded microchannel as a heat dissipation medium. This liquid is electrically insulating, non-flammable, low in viscosity, chemically inert, and can operate over a wide temperature range, avoiding direct contact with electronic components that could cause malfunctions. The flow velocity of the fluorinated liquid in the embedded microchannel is 0.1 m / s to 0.4 m / s, the flow Reynolds number is less than 2000, and the system operating pressure is ≤0.15 MPa, ensuring heat dissipation efficiency and avoiding noise, fatigue, and leakage risks caused by turbulence, thereby realizing the embedded fluorinated liquid microchannel.

[0044] In some preferred embodiments, the robotic bionic skin also includes a liquid cooling circulation system connected to an embedded microchannel, comprising a micropump, a semiconductor thermostat module, and tubing, the tubing and the embedded microchannel forming a circulation loop; the semiconductor thermostat module includes a Peltier thermoelectric cooler, a temperature sensor, and a control unit, the temperature sensor being embedded in the surface layer of the bionic skin, and the control unit being used to adjust the current and power of the Peltier thermoelectric cooler based on the feedback signal from the temperature sensor to achieve switching between cooling and heating modes.

[0045] Preferably, a cold-end heat exchanger and a hot-end heat exchanger are also installed in the circulation loop to achieve cooling and heat dissipation, so as to actively regulate the temperature of the coolant.

[0046] Temperature sensors are embedded in the surface layer of the bionic skin, preferably NTC or thin-film temperature sensors, and are strategically placed near key robot joints and electronic components. The control system uses an MCU or control board in conjunction with a PID control algorithm, employing a micro-pump to regulate coolant flow and adjusting the current and power of the Peltier thermoelectric cooler to achieve closed-loop constant temperature control, stabilizing the temperature of the robot's bionic skin within 30℃~35℃ (the anthropomorphic temperature range) or the safe operating temperature range of the electronic components.

[0047] In addition, other sensors, such as tactile feedback sensors, can be embedded in the surface layer of the bionic skin to enrich the sensory functions of the robot's bionic skin.

[0048] In some preferred embodiments, the outer diameter D1 of the hollow wire 1 is 1.0 mm to 3.0 mm. If the outer diameter is less than 1.0 mm, there may be a risk of microchannel blockage and cleaning will be difficult; if the outer diameter is greater than 3.0 mm, the risk of bending and collapse will increase significantly.

[0049] The microchannel wall thickness t of the hollow wire 1 satisfies the following conditions: t / D1≥0.25 in the static region, t / D1≥0.35 in the bending region, and t / D1≥0.45 near the joint, and t≥0.3mm. Here, the static region refers to the parts of the robot's bionic skin that do not undergo or only undergo slight bending deformation, such as the non-joint areas of the torso and limbs; the bending region refers to the parts of the robot's bionic skin that need to withstand repeated bending deformation; and the area near the joint refers to the region around the robot's joint pivot, where the stress is most complex, and it simultaneously bears greater bending deformation and internal pressure, and generates more significant heat. By differentiating the microchannel wall thickness according to the stress characteristics and heat generation characteristics at different locations (for example, the bending area is subjected to internal pressure and bending at the same time, and the heat generation near the joint is more significant and the bending amplitude and internal pressure are greater), it is possible to improve the pressure resistance and fatigue bending resistance of the hollow wire 1 while ensuring heat exchange efficiency, avoid microcracks caused by the combined effect of internal pressure and bending, and thus prevent the fluorinated liquid from penetrating and causing the swelling of the thermoplastic polyurethane soft segment and the precipitous drop in fatigue life.

[0050] The minimum distance s1 from the embedded microchannel to the outer surface of the bionic skin surface layer is ≥0.8mm, and the minimum distance s2 to the interface between the substrate layer and the elastic heat dissipation layer is ≥1.0mm; at the robot joints and foot soles, the minimum distance s3 from the embedded microchannel to the surface is ≥1.5mm. These distance limits effectively prevent microchannel damage caused by external impacts, avoid the risk of coolant leakage due to wear of the bionic skin surface layer, and simultaneously ensure the realistic tactile feel and long-term durability of the bionic skin. These minimum distances can be achieved through the thickness of the bionic skin surface layer, the orientation of the elastic heat dissipation layer, or other feasible methods, which are not specifically limited here.

[0051] In some preferred embodiments, the hollow wire 1 may adopt a bifurcated (Y-shaped or λ-shaped), gradually changing diameter structure, or biomimetic mesh structure. To avoid uneven fluid distribution and excessive local flow resistance, the layout of the hollow wire 1 should avoid long straight segments, 90° right-angle turns, and parallel equidistant PCB-like layouts.

[0052] For the bifurcation structure, the bifurcation angle is preferably 30°~60°, the sub-channel diameter is preferably 0.6~0.75 times the main channel diameter, and the fillet radius R at the bifurcation transition is ≥1.0D (where D is the main channel diameter). Simultaneously, the channel dimensions before and after the bifurcation satisfy D... main ² ≈ D1² + D2², where D main D1 and D2 are the diameters of the main flow channel and the diameters of the sub-flow channels, respectively, to approximately ensure the balance between flow velocity and pressure drop before and after the bifurcation, thereby maintaining stable heat dissipation performance.

[0053] In some preferred embodiments, the biomimetic skin surface layer has a Shore A hardness of 50-60 and a thickness of 1mm-10mm. This hardness range is very close to that of human skin (Shore A hardness approximately 40-60), providing a skin-like soft touch and suitable elastic deformation capability. A thickness of 1mm or more ensures surface abrasion resistance and basic protective performance; while keeping it within 10mm avoids a deterioration in tactile feel and a slower thermal response due to excessive thickness. This layer is continuous and dense, primarily providing tactile interaction, a biomimetic appearance, and basic protection, while also providing a smooth and uniform thermal conduction interface for the underlying elastic heat dissipation layer.

[0054] The elastic heat dissipation layer has a Shore A hardness of 75-90 and a thickness of 5mm-50mm. This hardness is higher than that of the surface layer of bionic skin, aiming to ensure the mechanical stability and resilience of the winding structure, preventing collapse or plastic deformation of the 3D printed filaments during repeated deformation. The choice of thickness range requires a balance between heat dissipation capacity and joint mobility: a lower limit of 5mm allows sufficient space for microchannel arrangement and provides some thermal buffering, while an upper limit of 50mm can accommodate the conventional sizes of most robot limbs. This elastic heat dissipation layer adopts a three-layer winding structure with two dense upper and lower layers and a loose middle layer. While ensuring overall support strength, the loose central layer forms a heat dissipation channel, thus achieving both high elastic support and efficient heat dissipation.

[0055] Corresponding to the aforementioned robotic bionic skin, this application embodiment also provides a method for preparing robotic bionic skin, including the following steps: (1) Substrate layer formation step: Provide or form a substrate layer, which can be the shell or skeleton of the robot body, or a separately made support layer, depending on actual needs.

[0056] (2) Preparation steps of the elastic heat dissipation layer: (2a) Elastic granule preparation: Elastic granules are prepared by prepolymer method or melt blending method. The material of elastic granules is selected from one or more of thermoplastic polyurethane, polyethylene, polyolefin elastomer, and thermoplastic polyester elastomer. During the preparation process, the granules are made uniform and free of lumps, which is convenient for subsequent 3D printing.

[0057] (2b) 3D printing molding: Taking TPU as an example, select a 3D printing molding equipment that is compatible with elastic granules, add the elastic granules to the equipment and heat and melt them, and extrude them through the nozzle to form a continuous elastic filament with a uniform diameter; control the relative movement of the nozzle and the molding substrate (the nozzle can move, the substrate can move, or both can move synchronously), so that the continuous elastic filament is deposited layer by layer on the surface of the substrate layer according to the preset bending and winding path, and the first dense winding layer, the central heat dissipation winding layer and the second dense winding layer are printed in sequence, and finally a complete and firmly bonded elastic heat dissipation layer is obtained.

[0058] (3) Bionic skin surface layer formation steps: On the side of the prepared elastic heat dissipation layer away from the substrate layer, the bionic skin surface layer is formed by coating, injection molding or 3D printing to ensure that the bionic skin surface layer and the elastic heat dissipation layer are tightly bonded and free from defects such as delamination and bubbles, and finally the robot bionic skin is obtained.

[0059] In some preferred embodiments, the elastic granules are thermoplastic polyurethane (TPU) granules, preferably polyether-type TPU. The reason for choosing polyether-type is primarily due to the fact that biomimetic skin will come into contact with a liquid environment and undergo thermal cycling during use; polyester-type TPU is prone to hydrolysis or swelling under these conditions, making it unsuitable. Preferably, the TPU printing material has a tensile strength ≥15MPa and an elongation at break ≥600%, ensuring that the printed structure possesses sufficient mechanical properties and elasticity.

[0060] The TPU granules were prepared using a prepolymer method, and the specific steps are as follows: First, polytetrahydrofuran ether diol is reacted with 4,4'-diphenylmethane diisocyanate to generate a prepolymer. The isocyanate group (NCO) content in the prepolymer is controlled to be 4.5wt%~6.5wt%. If the NCO content is too low, the subsequent chain extension and crosslinking density will be insufficient, and the material will be too soft; if it is too high, the viscosity will be high, making it difficult to extrude during printing, and it is easy to crosslink prematurely.

[0061] Then, 1,4-butanediol is added for chain extension. The reaction temperature is controlled at 75℃~85℃. Lower temperatures result in slower reactions and lower efficiency; higher temperatures lead to more side reactions and a wider molecular weight distribution. All air bubbles are removed to prevent pores in the printed wires, which would affect both mechanical properties and appearance. After degassing, granulation is performed to obtain TPU granules.

[0062] Thermoplastic polyurethane granules were melt-blended with functionalized graphene oxide (f-GO) to obtain thermoplastic polyurethane composites with a functionalized graphene oxide content of 0.5wt%~3wt%. The main purpose of adding f-GO is to improve the wear resistance, thermal conductivity, and rigidity of the material, compensating for the low thermal conductivity of TPU itself (approximately 0.2 W / m·K). f-GO has a large specific surface area and significant interfacial interaction with the TPU matrix. It can bear part of the load during friction, reducing direct wear of the soft segments of the matrix, thereby improving wear resistance and surface scratch resistance. At the same time, appropriate addition can reinforce the material and increase the modulus without excessively sacrificing elasticity.

[0063] The content of functionalized graphene oxide is 0.5wt%~3wt%, preferably 1wt%~2wt%. If the content is less than 0.5wt%, f-GO is difficult to form an effective thermal and mechanical reinforcement network in the matrix, and the reinforcement effect is limited. If the content is higher than 3wt%, f-GO is prone to agglomeration, which leads to a decrease in melt fluidity and elasticity, and problems such as nozzle clogging and poor extrusion are likely to occur during 3D printing.

[0064] Preferably, to ensure more uniform dispersion of f-GO in the matrix, it can be pre-treated with ultrasound: f-GO is ultrasonically dispersed in N,N-dimethylformamide (DMF) solvent, with the ultrasound power controlled at 400W~600W for 20~40 minutes. This ultrasound treatment helps to break up the agglomerates of f-GO and improve its dispersibility, resulting in better dispersion when subsequently melt-blended with TPU granules.

[0065] In the 3D printing molding process, thermoplastic polyurethane composite material is heated and melted, then extruded to form a continuous thermoplastic polyurethane filament. The nozzle's outlet diameter matches the TPU filament diameter, and the nozzle outlet temperature is controlled between 85℃ and 330℃, preferably 180℃ to 230℃. The specific temperature is adjusted according to the hard segment content of the TPU; a higher hard segment content allows for a slightly higher temperature, but it should not exceed 230℃, otherwise degradation may occur. The molding substrate temperature is controlled between 41℃ and 60℃ to prevent the applied layer from cooling too quickly, thus improving the bonding strength of the TPU bonding nodes 4. The relative movement speed between the nozzle and the molding substrate is controlled between 31mm / s and 76mm / s. Too slow a speed reduces efficiency and increases the risk of material degradation, while too fast a speed may result in insufficient melting or cooling, affecting shape accuracy. In practical applications, it is preferable to use a low speed (31~50mm / s) for complex paths in joint areas and a high speed (50~76mm / s) for straight sections in non-joint areas.

[0066] In some preferred embodiments, the thermoplastic polyurethane granules include soft segments and hard segments; The soft segment is made of polytetrahydrofuran ether glycol, with a number-average molecular weight of 2000 g / mol to 4000 g / mol, accounting for 60% to 75% of the total mass of the thermoplastic polyurethane granules. This ensures that the soft segment can form a continuous rubber phase. If the molecular weight is too low (below 2000), the soft segment chains will be too short, resulting in decreased elasticity and higher hardness. If the molecular weight is too high (above 4000), excessive phase separation between the soft and hard segments is likely, leading to poor compatibility and uneven mechanical properties. Controlling the molecular weight between 2000 and 4000 and the mass percentage between 60% and 75% achieves a good balance between high elastic recovery and processing fluidity. This ensures that the printed filament is sufficiently soft and resilient without collapsing during printing due to excessive softness, resulting in good molding stability.

[0067] The hard segment is the reaction product of 4,4'-diphenylmethane diisocyanate and 1,4-butanediol, accounting for 22% to 28% of the total mass of thermoplastic polyurethane granules. This proportion range ensures that the material has appropriate modulus, abrasion resistance, and tear resistance while avoiding excessive rigidity and loss of elasticity caused by excessive hard segment. Too low a hard segment content results in insufficient material strength and poor heat resistance; too high a content leads to decreased elasticity and excessive hardness, failing to meet the design requirements of Shore A hardness of 75 to 90 for elastic heat dissipation layers. The molar ratio of isocyanate groups to hydroxyl groups (NCO / OH) is 1.02 to 1.06. A slight excess of isocyanate groups can compensate for water consumption and side reaction losses during the reaction process, ensuring that the molecular weight reaches the expected level. However, excessive amounts can lead to a sharp increase in prepolymer viscosity or even gelation.

[0068] Thermoplastic polyurethane granules also contain an additive system, comprising, by total TPU granule mass, 0.3wt%~0.8wt% antioxidants, 0.2wt%~0.5wt% metal ion scavengers (such as Irgastab-2002), and 0.1wt%~0.3wt% UV absorbers (such as UV-329 and UV-1577). The antioxidants are preferably a blend of Irganox 1010 and Irganox 168 in a ratio of 1:3 to 2:3. This blend synergistically captures free radicals and decomposes hydroperoxides, effectively inhibiting the thermal oxidative degradation of TPU during melt processing and long-term thermal cycling. The metal ion scavengers are used to complex trace metal ions, preventing them from catalyzing accelerated oxidation. The UV absorbers are used to delay photoaging in outdoor or strong light environments. The content of each additive is controlled at a low level to avoid negatively impacting the mechanical properties and printability of the TPU.

[0069] In some preferred embodiments, the functionalized graphene oxide is selected from carboxyl-modified graphene oxide or amino-modified graphene oxide, with a sheet diameter controlled at 5μm~10μm and a thickness of 3nm~8nm. This size range is primarily based on a balance between dispersibility and thermal conductivity. When the sheet diameter is too small (<5μm), although it is easy to disperse in the TPU matrix, it is difficult to form an effective thermally conductive network, requiring frequent crossings of the filler-matrix interface for heat transfer, leading to increased thermal resistance. When the sheet diameter is too large (>10μm), the specific surface area decreases, reducing the interfacial bonding points with TPU, and it is prone to folding or breaking during melt blending and printing shearing, thus disrupting the thermal conductivity pathway. A thickness controlled at 3nm~8nm (approximately 5~10 layers of graphene) retains the high aspect ratio of graphene oxide, which is beneficial for in-plane thermal conductivity, while avoiding the problem of re-agglomeration due to excessive van der Waals forces during processing when the sheets are too thin (<3nm, i.e., close to a single layer or a few layers).

[0070] The introduction of carboxyl or amino functional groups can, on the one hand, form hydrogen bonds or covalent bonds with urethane groups, ether bonds, etc. in the TPU molecular chain, improve interfacial compatibility, and reduce interfacial thermal resistance; on the other hand, it provides steric hindrance and electrostatic repulsion for the stable dispersion of graphene oxide in TPU, preventing it from re-aggregating during melt blending and multiple thermal processes.

[0071] In some preferred embodiments, the preparation of the thermoplastic polyurethane composite material includes the following steps: Functionalized graphene oxide was ultrasonically dispersed in N,N-dimethylformamide (DMF) solvent at a power of 400W~600W for 20min~40min to obtain a dispersion. The dispersion was melt-blended with a portion of thermoplastic polyurethane granules, and then extruded and granulated to obtain a masterbatch with a functionalized graphene oxide content of 10wt%~15wt%. The concentration of this masterbatch is much higher than the final usage content. The purpose is to achieve sufficient exfoliation and uniform dispersion of graphene oxide in a small amount of matrix through high shear stress at high concentration, avoiding the agglomeration problem caused by insufficient shear force when directly blending at low concentration.

[0072] The masterbatch is then melt-blended with the remaining thermoplastic polyurethane granules and diluted until the content of functionalized graphene oxide is 0.5wt%~3wt% to obtain a thermoplastic polyurethane composite material. The ratio of masterbatch to matrix material is determined based on the target content calculation, and the masterbatch usually accounts for about 3%~30% of the total feed.

[0073] This two-step process can ensure the effective dispersion of nanofillers, avoid the adverse effects of high graphene oxide content on the melt flowability and printability of TPU, and also facilitate the flexible adjustment of the final content according to actual thermal conductivity requirements.

[0074] In some preferred embodiments, two processes can be used when preparing the hollow wire 1 in the 3D printing molding step: Annular printing nozzle: TPU composite material is directly extruded through an annular cross-section nozzle to form hollow wires. The process is simple, but it requires high melt strength. It is necessary to avoid the wires from collapsing due to insufficient melt strength after extrusion.

[0075] Coaxial dual-nozzle system: Simultaneously extrudes TPU composite material and soluble sacrificial material; the former forms the tube wall, while the latter fills the interior as the microchannel core material. Core material support ensures molding accuracy under bending paths and has a wider range of applications.

[0076] After molding, soluble sacrificial materials are removed by washing with water to form embedded microchannels. The preferred washing temperature is 40℃~60℃, and the washing time is 30 minutes to 4 hours to ensure that the core material is fully dissolved without damaging the TPU matrix.

[0077] The soluble sacrificial material can be either polyvinyl alcohol (PVA) or butanediol-vinyl alcohol copolymer (BVOH). PVA has low cost and good water solubility, but its thermal stability is slightly worse; BVOH has better thermal stability, good compatibility with TPU co-extrusion process, and its dissolution rate can be adjusted by the copolymerization ratio, making it more suitable for simultaneous extrusion molding of high-temperature TPU materials. The specific choice depends on the printing temperature and post-processing conditions.

[0078] The following detailed description of examples of this application is exemplary and is used only to explain this application, and should not be construed as limiting this application. The raw materials used are as follows: polytetrahydrofuran ether glycol, BASF PolyTHF 3000, with a number average molecular weight of 3000 g / mol; 4,4'-diphenylmethane diisocyanate, WANNATE® MDI-100LL from Wanhua Chemical; 1,4-butanediol, BASF industrial grade; antioxidant, BASF Irganox 1010 and Irganox 168 compound system; metal ion scavenger, BASF Irgastab 2002; UV absorber, BASF Tinuvin 329; amino-modified graphene oxide, Changzhou Sixth Element Materials Technology's amino-modified graphene oxide (GO-NH2), with a sheet diameter of 5~10 μm and a thickness of 3~8 nm; sacrificial material, Kuraray Mowiflex TC 232, a water-soluble support material for 3D printing; and fluorinated liquid heat dissipation medium, 3M Fluorinert™. FC-40; silane coupling agent primer, Dow Z-6040; aliphatic polyurethane, Covestro Desmodur N 3300 combined with a polyether polyol curing system; aluminum alloy skeleton matrix, 6061-T6, surface sandblasted. All the above raw materials are commercially available industrial-grade products and can be purchased and used directly.

[0079] Example 1 This embodiment provides a robotic bionic skin, which includes, in sequence along the thickness direction, a base layer, an elastic heat dissipation layer, and a bionic skin surface layer.

[0080] The substrate layer utilizes the aluminum alloy skeleton of a robotic arm. The biomimetic skin surface layer employs an aliphatic polyurethane coating with a Shore A hardness of 55. The elastic heat dissipation layer comprises a first dense winding layer, a central heat dissipation winding layer, and a second dense winding layer, stacked sequentially, with a total thickness of 20 mm and a Shore A hardness of 82. This elastic heat dissipation layer is a winding structure formed by fused deposition modeling (FDM) 3D printing of TPU. The winding structure is formed by bending and winding continuous TPU filaments, and bonding nodes are provided on the continuous TPU filaments, with an average spacing of 6 mm between adjacent nodes.

[0081] The first and second dense winding layers use solid TPU wires, while the central heat-dissipating winding layer uses hollow TPU wires. Embedded microchannels are formed within the hollow TPU wires for introducing fluorinated liquid as a heat dissipation medium. The outer diameter of the hollow TPU wires is 2.0 mm, and the wall thickness of the microchannels varies depending on the region: the wall thickness to wire diameter ratio t / D1 = 0.30 in the static region, t / D1 = 0.35 in the bending region, and t / D1 = 0.45 near the joint. The minimum distance from the microchannel to the outer surface of the bionic skin surface layer is 1.0 mm, and the minimum distance to the interface between the substrate layer and the elastic heat dissipation layer is 1.2 mm; at the robot's elbow joint, this minimum distance increases to 1.8 mm.

[0082] The thickness of the first and second dense winding layers each accounts for 15% (3 mm) of the total thickness of the elastic heat dissipation layer, and the relative density is 75%; the thickness of the central heat dissipation winding layer accounts for 70% (14 mm) of the total thickness, and the relative density is 45%.

[0083] In terms of printing path design, the bending radius R1 of the continuous TPU filament is 16mm in the elbow joint area and 12mm in the non-joint area. The angle between the bending and winding direction of the continuous TPU filament and the plane of the substrate layer is approximately 35°.

[0084] In addition, this embodiment is equipped with a liquid cooling circulation system connected to the embedded microfluidic channel. This system includes a micropump, a semiconductor thermostat module, and piping, which together with the microfluidic channel form a circulation loop. Fluorinated liquid is circulated within the microfluidic channel as a heat dissipation medium, with a flow rate controlled at 0.2 m / s to 0.3 m / s, a flow Reynolds number Re < 2000 (laminar flow), and a system operating pressure of 0.08 MPa. The semiconductor thermostat module includes a Peltier thermoelectric cooler, a temperature sensor, and a control unit. The temperature sensor is embedded within the surface layer of the bionic skin, and the control unit adjusts the current and power of the Peltier thermoelectric cooler based on the feedback signal from the temperature sensor, thereby achieving closed-loop temperature control.

[0085] The above-mentioned method for preparing robotic bionic skin includes the following steps: (1) Steps for forming the matrix layer An aluminum alloy skeleton is provided as the base layer for the robotic arm.

[0086] (2) Preparation steps of elastic heat dissipation layer (2a) Preparation of elastic granules TPU granules were prepared using a prepolymer method. Specifically, polytetrahydrofuran ether diol (PTMG) with a number-average molecular weight of 3000 g / mol was reacted with 4,4'-diphenylmethane diisocyanate (MDI) at 80°C to generate a prepolymer, with the isocyanate group (NCO) content in the prepolymer controlled at 5.5 wt%. Then, 1,4-butanediol (BDO) was added for chain extension, with the reaction temperature controlled at 80°C and the NCO / OH molar ratio at 1.04. After the reaction was completed, the mixture was degassed under vacuum for 2 hours, followed by extrusion granulation to obtain TPU granules.

[0087] The granules also contain an additive system, which, based on the total mass of the TPU granules, includes 0.5 wt% antioxidant (Irganox 1010 and Irganox 168 in a 1:2 ratio), 0.3 wt% metal ion scavenger (Irgastab-2002), and 0.2 wt% ultraviolet absorber (UV-329).

[0088] Amino-modified graphene oxide was ultrasonically dispersed in DMF solvent at a power of 460W for 35 minutes to obtain a dispersion. This dispersion was then melt-blended with a portion of TPU granules and extruded to produce a masterbatch with a graphene oxide content of 12 wt%. The masterbatch was then melt-blended with the remaining TPU granules and diluted to a final graphene oxide content of 1.5 wt% to obtain the TPU composite material. The amino-modified graphene oxide sheets had a diameter of 6 μm–8 μm and a thickness of 4 nm–6 nm.

[0089] (2b) 3D printing The printing was performed using a dual-nozzle FDM device, with the two nozzles loaded with TPU composite material and PVA soluble sacrificial material, respectively.

[0090] When printing the first dense winding layer, switch to single nozzle mode, heat and melt the TPU composite material and extrude it through the nozzle to form a solid TPU filament. Deposit it layer by layer according to the preset bending and winding path, and control the relative density of the layer to be 75% and the thickness to be 3mm.

[0091] When printing the central heat-dissipating wrapping layer, switch to coaxial dual-nozzle mode. The outer nozzle extrudes TPU composite material to form a hollow TPU filament, while the central channel simultaneously extrudes PVA as a soluble sacrificial material to fill the interior of the filament, forming a microchannel core material. Deposit along a curved winding path, controlling the relative density of this layer to 45% and the thickness to 14mm.

[0092] When printing the second dense winding layer, switch back to single nozzle mode to extrude solid TPU filaments and deposit them layer by layer, controlling the relative density of this layer to be 75% and the thickness to be 3mm.

[0093] The printing parameters are uniformly set as follows: nozzle outlet temperature 210℃, substrate temperature 50℃, and relative movement speed between the nozzle and the substrate 50mm / s.

[0094] After printing, the part is immersed in 50°C deionized water for 2 hours to dissolve and remove the PVA core material in the central heat dissipation winding layer, thereby forming an embedded microchannel inside the hollow wire of the central layer, while the solid structure of the dense layers on both sides remains unaffected.

[0095] (3) Steps for forming the surface layer of bionic skin An aliphatic polyurethane coating is sprayed onto the surface of the elastic heat dissipation layer and cured at room temperature for 24 hours to form a biomimetic skin surface layer. Simultaneously, a miniature PT100 temperature sensor is embedded within the surface layer and connected to the control unit of the liquid cooling circulation system for real-time monitoring of the skin surface temperature.

[0096] Example 2 The robotic bionic skin of Example 1 differs in that the relative density of the first and second dense winding layers is 50%, and the relative density of the central heat-dissipating winding layer is 80%.

[0097] Example 3 The preparation method is the same as in Example 1, except that a direct blending method is used: amino-modified graphene oxide (Changzhou Sixth Element GO-NH2-10) is directly melt-blended with all TPU granules in one step, with a target graphene oxide content of 1.5 wt%, without the masterbatch method.

[0098] Example 4 The preparation method is the same as in Example 1, except that the nozzle outlet temperature is 85°C, the substrate temperature is maintained at 50°C, and the printing speed is maintained at 50 mm / s.

[0099] Comparative Example 1 Referring to the bionic skin of the robot in Embodiment 1, the difference is that the elastic heat dissipation layer does not have a layered structure of a first dense winding layer, a central heat dissipation winding layer and a second dense winding layer. The elastic heat dissipation layer is a single-layer winding structure with a continuous elastic wire (diameter 1.5mm, solid) with a bending radius R=10mm and a bending direction with an angle of about 15° with the plane of the base layer. The overall relative density of the elastic heat dissipation layer is 50%.

[0100] Comparative Example 2 The robotic bionic skin of Example 1 differs in that the diameter D of the continuous elastic wire is 2.0 mm, and the bending radius R of the bending winding path is 8 mm.

[0101] Comparative Example 3 The robotic bionic skin of Example 1 differs in that the angle between the bending and winding direction of the continuous elastic wire and the plane of the substrate layer is approximately 50°.

[0102] Comparative Example 4 The robotic bionic skin of Example 1 differs in that the spacing between adjacent bonding nodes is approximately 25 mm.

[0103] Test case For the robotic bionic skins of Examples 1-4 and Comparative Examples 1-4, the following tests were conducted: Steady-state surface temperature was monitored using an infrared thermal imager under continuous working load on the robotic skin, and the average temperature after stabilization was recorded to evaluate the impact of different structural designs on heat dissipation efficiency; Cyclic bending fatigue life was assessed by simulating repeated bending motions of robot joints (e.g., reciprocating bending from 0° to 90°), recording the number of cycles until obvious cracks, fractures, or performance degradation occurred, to evaluate the durability and fatigue resistance of the bionic skin under long-term dynamic use. Specific test results are shown in Table 1.

[0104] Table 1

[0105] Based on the above data analysis, it can be seen that Example 1, due to its optimized three-layer dense-loose-dense structure, exhibits the best overall performance, with a steady-state surface temperature of 34.0℃ (within the anthropomorphic comfort range) and a cyclic bending fatigue life exceeding 100,000 cycles. Comparative Example 1, lacking layering, suffers from the worst heat dissipation and lifespan. Comparative Examples 2-4 experience slight decreases in fatigue life due to excessively small bending radii, excessively large angles, or excessively long node spacing, respectively. Example 2 shows a slight increase in heat dissipation temperature due to an excessively dense central layer (relative density of 80%). Example 3, employing a direct blending method to replace masterbatch, shows slight deterioration in both temperature and lifespan. In Example 4, lowering the nozzle temperature to 85℃ results in a slight increase in temperature and a decrease in lifespan. In summary, this application effectively achieves efficient heat dissipation and reliable mechanical deformation capability of biomimetic skin through the layered structure design of the elastic heat dissipation layer and the strict limitation of key geometric parameters.

Claims

1. A robotic bionic skin, characterized in that, include: Matrix layer; Bionic skin surface layer; as well as An elastic heat dissipation layer is disposed between the substrate layer and the bionic skin surface layer, comprising a first dense winding layer, a central heat dissipation winding layer and a second dense winding layer stacked sequentially; The elastic heat dissipation layer is a winding structure formed by 3D printing of elastic material. The winding structure is formed by bending, winding and interlacing continuous elastic wires. The continuous elastic wires can be solid or hollow. The hollow part of the hollow wire is used to contain gas or liquid media. The continuous elastic wires are provided with bonding nodes, and the distance between adjacent bonding nodes is 1mm to 20mm. The bonding nodes are formed by the continuous elastic wires that are in a semi-molten state or have uncured surfaces during the 3D printing process and are bonded together. The thickness of the first dense winding layer and the second dense winding layer each independently accounts for 5% to 20% of the total thickness of the elastic heat dissipation layer, and their relative densities are each independently 20% to 80%, wherein the relative density is the ratio of the total volume of the continuous elastic wire in the layer to the total volume of the layer. The relative density of the central heat-dissipating winding layer is less than the relative density of the first dense winding layer and the second dense winding layer; The diameter D of the continuous elastic wire is 0.8mm~3.0mm, and the bending radius R of its bending winding path satisfies R≥5D; The angle between the bending and winding direction of the continuous elastic wire and the plane where the matrix layer is located is 0°~46°; The material of the continuous elastic wire is selected from one or more of thermoplastic polyurethane, polyethylene, polyolefin elastomer, and thermoplastic polyester elastomer; The 3D printing process is selected from at least one of stereolithography photopolymerization 3D printing technology, fused deposition modeling, photopolymerization jetting technology, and sintering.

2. The robotic bionic skin according to claim 1, characterized in that, The relative densities of the first dense winding layer and the second dense winding layer are each independently 70%~80%, and the relative density of the central heat-dissipating winding layer is 20%~70%.

3. The robotic bionic skin according to claim 1, characterized in that, The robotic bionic skin includes joint areas and non-joint areas; The bending radius R1 of the continuous elastic wire located in the joint region satisfies R1≥7D and R1≥1.1R2, where R2 is the bending radius of the continuous elastic wire in the non-joint region.

4. The robotic bionic skin according to claim 1, characterized in that, The continuous elastic wire is a hollow wire, and the material of the elastic wire is thermoplastic polyurethane. Embedded microchannels are formed inside the hollow wire.

5. The robotic bionic skin according to claim 4, characterized in that, Fluorinated liquid is introduced into the embedded microchannel as a heat dissipation medium. The flow velocity of the fluorinated liquid in the embedded microchannel is 0.1m / s to 0.4m / s, the flow Reynolds number is less than 2000, and the system working pressure is ≤0.15MPa.

6. The robotic bionic skin according to claim 4 or 5, characterized in that, It also includes a liquid cooling circulation system, which is connected to the embedded microchannel and includes a micro pump, a semiconductor thermostat module and pipelines, wherein the pipelines and the embedded microchannels together form a circulation loop; The semiconductor thermostatic module includes a Peltier thermoelectric cooler, a temperature sensor, and a control unit. The temperature sensor is embedded in the surface layer of the bionic skin, and the control unit is used to adjust the current and power of the Peltier thermoelectric cooler according to the feedback signal of the temperature sensor to switch between cooling and heating modes.

7. The robotic bionic skin according to any one of claims 4 to 6, characterized in that, The outer diameter D1 of the hollow wire is 1.0mm~3.0mm; The wall thickness t of the microchannel of the hollow wire satisfies the following conditions: t / D1≥0.25 in the static region, t / D1≥0.35 in the bending region, t / D1≥0.45 near the joint, and t≥0.3mm; The minimum distance s1 from the embedded microchannel to the outer surface of the bionic skin surface layer is ≥0.8mm, and the minimum distance s2 from the microchannel to the interface between the substrate layer and the elastic heat dissipation layer is ≥1.0mm; at the robot joint and foot, the minimum distance s3 from the embedded microchannel to the surface is ≥1.5mm.

8. The robotic bionic skin according to claim 1, characterized in that, The biomimetic skin surface layer has a Shore A hardness of 50-60 and a thickness of 1mm-10mm; The elastic heat dissipation layer has a Shore hardness of 75-90 and a thickness of 5mm-50mm.

9. A method for preparing the robotic bionic skin according to any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Matrix layer formation step: providing or forming a matrix layer; (2) Preparation steps of the elastic heat dissipation layer: (2a) Elastic granule preparation: Elastic granules are prepared by prepolymer method or melt blending method, wherein the material of the elastic granules is selected from one or more of thermoplastic polyurethane, polyethylene, polyolefin elastomer, and thermoplastic polyester elastomer; (2b) 3D printing molding: Using 3D printing molding equipment, the elastic granules are heated and melted and then extruded through a nozzle to form a continuous elastic filament. The nozzle is controlled to move relative to the molding substrate so that the continuous elastic filament is deposited layer by layer on the substrate layer according to a preset bending and winding path, forming a first dense winding layer, a central heat dissipation winding layer and a second dense winding layer in sequence to obtain an elastic heat dissipation layer. (3) Bionic skin surface layer formation step: A bionic skin surface layer is formed on the elastic heat dissipation layer.

10. The preparation method according to claim 9, characterized in that, The elastic granules are thermoplastic polyurethane granules, which are prepared using a prepolymer method, including the following steps: Polytetrahydrofuran ether diol was reacted with 4,4'-diphenylmethane diisocyanate to generate a prepolymer, wherein the isocyanate group (NCO) content in the prepolymer was controlled to be 4.5 wt%~6.5 wt%. Then, 1,4-butanediol is added to carry out a chain extension reaction, and the reaction temperature is controlled at 75℃~85℃. After vacuum degassing, the product is granulated to obtain thermoplastic polyurethane granules. The thermoplastic polyurethane granules were melt-blended with functionalized graphene oxide to obtain a thermoplastic polyurethane composite material with a functionalized graphene oxide content of 0.5wt%~3wt%. In the 3D printing molding step, the thermoplastic polyurethane composite material is heated and melted and then extruded to form a continuous thermoplastic polyurethane filament. The nozzle outlet temperature is 85℃~330℃, the temperature of the molding substrate is 41℃~60℃, and the relative moving speed between the nozzle and the molding substrate is 31mm / s~76mm / s.

11. The preparation method according to claim 10, characterized in that, The thermoplastic polyurethane granules include soft segments and hard segments; The soft segment is polytetrahydrofuran ether diol, with a number-average molecular weight of 2000 g / mol to 4000 g / mol, and accounts for 60% to 75% of the total mass of the thermoplastic polyurethane granules. The hard segment is the reaction product of 4,4'-diphenylmethane diisocyanate and 1,4-butanediol, accounting for 22% to 28% of the total mass of the thermoplastic polyurethane granules, and the molar ratio of isocyanate groups to hydroxyl groups (NCO / OH) is 1.02 to 1.

06. The thermoplastic polyurethane granules also contain an additive system, which, based on the total mass of the thermoplastic polyurethane granules, includes 0.3wt% to 0.8wt% of antioxidant, 0.2wt% to 0.5wt% of metal ion scavenger, and 0.1wt% to 0.3wt% of ultraviolet absorber.

12. The preparation method according to claim 10, characterized in that, The functionalized graphene oxide is carboxyl-modified graphene oxide or amino-modified graphene oxide, with a sheet diameter of 5μm~10μm and a thickness of 3nm~8nm.

13. The preparation method according to claim 10, characterized in that, The preparation of the thermoplastic polyurethane composite material includes the following steps: The functionalized graphene oxide was ultrasonically dispersed in N,N-dimethylformamide solvent at a power of 400W to 600W for 20 to 40 minutes to obtain a dispersion. The dispersion is melt-blended with a portion of the thermoplastic polyurethane granules and extruded and granulated to obtain a masterbatch with a functionalized graphene oxide content of 10wt%~15wt%. The masterbatch is then melt-blended with the remaining thermoplastic polyurethane granules and diluted to a functionalized graphene oxide content of 0.5wt%~3wt% to obtain the thermoplastic polyurethane composite material.

14. The preparation method according to claim 9, characterized in that, In the 3D printing molding step, when preparing hollow filaments, a ring-shaped printing nozzle is used to print the hollow filaments, or a coaxial dual-nozzle system is used to simultaneously extrude elastic granules and soluble sacrificial materials, wherein the soluble sacrificial materials form microchannel core materials. After molding, the soluble sacrificial material is removed by washing with water to form an embedded microchannel; The soluble sacrificial material is a copolymer of polyvinyl alcohol or butanediol.

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