A flexible self-powered tactile sensor based on 3D printing and a manufacturing method thereof

Abstract

The application belongs to the technical field of tactile sensing equipment, and discloses a flexible self-powered tactile sensor based on 3D printing and a manufacturing method thereof. The tactile sensor comprises a flexible coil layer composed of a flexible film and a plurality of liquid metal coils, and the flexible film wraps the liquid metal coils inside. The flexible coil layer is sleeved outside a finger-shaped support layer, so that the liquid metal coils are uniformly distributed in each direction outside the finger-shaped support layer. A magnetic block is arranged at the fingertip end of the finger-shaped support layer, and a gap is arranged between the magnetic block and the inner side wall of the flexible coil layer. When the flexible coil layer is subjected to external force in any direction, the liquid metal coil can be driven to generate deformation in the opposite direction of the external force, so as to generate relative movement with the magnetic block, and further change the magnetic flux passing through the liquid metal coil to generate an induced electric signal. The application has simple equipment structure, can realize multidirectional tactile sensing, and has simple manufacturing method.

Description

Technical Field

[0001] This invention belongs to the field of tactile sensing device technology, and more specifically, relates to a flexible self-powered tactile sensor based on 3D printing and its manufacturing method. Background Technology

[0002] Tactile perception is an indispensable source of information for robots to explore the external world, helping them perceive their surroundings. Compared to visual and auditory perception, it has unparalleled advantages in tasks such as object recognition and localization. Currently, the research and development of robot tactile sensors has received widespread attention, especially high spatial resolution tactile sensor arrays similar to human fingertips. Their research focuses on flexibility, multiple arrays, and lightweight design.

[0003] Multidirectional tactile perception is a crucial function for both humans and robots, providing robots with richer information to perform complex tasks. This primarily stems from the arrayed arrangement of tactile sensitive units. However, most existing robotic tactile sensors rarely focus on multidirectional tactile sensing in three-dimensional space. Some vision-based tactile sensors can monitor changes in the shape of an external membrane caused by pressure in real time using built-in cameras, and determine the location and direction of the pressure through image analysis and processing, thus achieving multidirectional tactile perception. However, these sensors are structurally complex and require mature computer vision algorithms and corresponding software assistance, resulting in high costs. Other robotic fingertip tactile sensor arrays integrate numerous Hall elements and small magnets into the finger bone and flexible layer to achieve multidirectional sensing. However, the large-scale integration of these non-self-powered devices limits their flexibility, increases their complexity, and the resulting wiring issues hinder further development. In summary, existing tactile sensors are structurally complex, lack flexibility, and can only achieve unidirectional tactile sensing, making it difficult to achieve accurate multidirectional tactile sensing. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a flexible self-powered tactile sensor based on 3D printing and its manufacturing method, thereby solving the problem that existing flexible self-powered tactile sensors are unable to achieve high-precision multi-directional tactile sensing.

[0005] To achieve the above objectives, the present invention provides a flexible self-powered tactile sensor based on 3D printing. The self-powered tactile sensor includes a support layer and a flexible coil layer integrally formed by 3D printing, wherein:

[0006] The flexible coil layer includes a flexible thin film and multiple liquid metal coils, with the flexible thin film enclosing the liquid metal coils inside. The flexible coil layer is sleeved on the outside of the finger-shaped support layer, so that the liquid metal coils are evenly distributed in various positions on the outside of the finger-shaped support layer. A magnetic block is provided at one end of the fingertip of the finger-shaped support layer, and there is a gap between the magnetic block and the inner wall of the flexible coil layer. When the flexible coil layer is subjected to an external force in any direction, it can drive the liquid metal coil to produce a deformation in the opposite direction of the external force, so as to generate relative movement with the magnetic block, thereby changing the magnetic flux passing through the liquid metal coil and generating an induced electrical signal.

[0007] Furthermore, the gap between one end of the support layer where the magnetic block is located and the inner wall of the flexible coil layer is 2mm-7mm.

[0008] Furthermore, the finger-shaped support layer has a mounting groove at one end that is the same shape as the magnetic block. The magnetic block is assembled in the mounting groove, and its N pole or S pole points towards the finger-shaped support layer.

[0009] Furthermore, the liquid metal coils comprise a plurality of coils and are arranged in an array within the flexible film; preferably, the number of liquid metal coils is 4 to 7; more preferably, each liquid metal coil has 1 to 3 turns of coil.

[0010] Furthermore, the remanence of the magnetic block is 0.5T-2T.

[0011] According to another aspect of the present invention, a method for manufacturing a flexible, self-powered tactile sensor based on 3D printing as described above is also disclosed, the method comprising the following steps:

[0012] S1 uses photopolymer 3D printing technology to print the support layer, inner mold and outer mold, and the inner surface of the outer mold has multiple coil-shaped protrusions.

[0013] S2 uses Plasma hydrophilic treatment technology to hydrophilically treat the inner mold and the outer mold for a specific time, then removes them, cools them, and assembles them to obtain a low-adhesion shell mold.

[0014] S3 injects the Ecoflex solution into the low-adhesion shell mold and cures it to obtain a flexible film with coil-shaped microchannels on the outer surface.

[0015] S4 Injects liquid metal into the coil-shaped microchannel, and then connects the external metal leads to the liquid metal in the coil-shaped microchannel and solidifies it to obtain a flexible film with a liquid metal coil.

[0016] S5 encapsulates the flexible film obtained in step S4 with Ecoflex solution and cures it to prevent the liquid metal coil from leaking out, thereby obtaining a flexible coil layer;

[0017] S6 installs a magnetic block at one end of the fingertip of the finger-shaped support layer, and then sleeves the flexible coil layer over the finger-shaped support layer, so that there is a gap between the magnetic block and the flexible coil layer.

[0018] Furthermore, the coil-shaped protrusion structure comprises 4 to 7 coils; preferably, the width of the coil-shaped protrusion structure is 0.1 mm to 1 mm, and the height of the coil-shaped protrusion structure is 0.1 mm to 1 mm; more preferably, each coil-shaped protrusion structure comprises 1 to 3 coils.

[0019] Furthermore, in step S6, after the flexible coil layer is fitted over the finger-shaped support layer, the distance between the magnetic block and the flexible coil layer is 2mm-7mm.

[0020] Furthermore, the Ecoflex solution contains at least one of Ecoflex 00-10, Ecoflex 00-20, and Ecoflex 00-30; preferably, the liquid metal is a gallium-based liquid metal.

[0021] Furthermore, in step S5, the encapsulation step is repeated 1 to 5 times.

[0022] Compared with the prior art, the above-described technical solutions conceived in this invention have the following main advantages:

[0023] 1. The multi-directional flexible self-powered sensor of the present invention includes a rigid finger-shaped support layer. A magnetic block is provided at one end of the fingertip of the support layer. A fully flexible conductive coil layer composed of a flexible polymer and a liquid metal coil integrally formed by 3D printing is sleeved on the outside of the rigid support layer, so that the liquid metal coil surrounds the outside of the support layer in various directions. A special gap is provided between the support layer where the magnetic block is located and the inner wall of the flexible coil layer. When the flexible coil layer is subjected to an external force in any direction, it can drive the liquid metal coil inside to produce a deformation opposite to the direction of the external force, so as to generate relative movement with the static magnetic block. This causes a change in the magnetic flux passing through the liquid metal coil, thereby generating an induced electrical signal. It can realize tasks such as object recognition and space exploration without the need for additional power supply wires. Overall, the flexible tactile sensor of the present invention has a simple structure, high sensitivity and simple fabrication.

[0024] 2. This invention enables multi-directional tactile sensing in three-dimensional space. The liquid metal coil array, composed of several liquid metal coils located in different orientations, is the source of this multi-directional tactile sensing. The preferred number of liquid metal coils is 4-7. The liquid metal coils are uniformly distributed within a finger-shaped flexible film. The more liquid metal coils there are, the more induced electrical signals are obtained, which is more beneficial for multi-directional tactile sensing. For example, a five-coil array can provide at least 21 different types of pressure sensing. However, if there are more liquid metal coils, the fabrication difficulty increases. The number of turns in each liquid metal coil is limited to 1-3 turns. More turns result in stronger induced electrical signals, which is beneficial for increasing the sensor's sensitivity. However, if the number of turns exceeds this range, the number of metal coils to be fabricated needs to be considered, leading to greater fabrication difficulty.

[0025] 3. In the finger-shaped flexible multidirectional self-powered tactile sensor of the present invention, after the finger-shaped flexible film is integrated with the finger-shaped rigid support layer, there is a certain gap between one end of the support layer with the magnetic block and the flexible coil layer, which provides deformation space for the flexible coil layer; the distance between the end of the mounting groove where the magnetic block is placed and the flexible coil layer is 2-7mm. The larger the distance, the easier the deformation and the larger the generated induced electrical signal, which is beneficial to improving the sensitivity of the tactile sensor. However, if the distance exceeds this range, the generated induced electrical signal will be smaller and difficult to distinguish.

[0026] 4. The finger-shaped flexible multi-directional self-powered tactile sensor of the present invention has a remanent magnetization of 0.5-2T. The larger the remanent magnetization, the larger the induced electrical signal, thus improving the sensitivity of the sensor. However, if the remanent magnetization is less than this range, the generated induced electrical signal will be smaller and difficult to distinguish.

[0027] 5. The manufacturing method of the flexible self-powered tactile sensor of the present invention is simple. It adopts 3D printing integral molding technology and prepares tactile sensors of various shapes by pre-designing the shape, size, thickness and other process parameters of the tactile sensor support layer and flexible coil layer. Moreover, the materials used in the preparation process are low cost, chemically stable and non-toxic and harmless to the human body. The manufacturing method is simple and the preparation efficiency is high. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structural model of the finger-shaped flexible self-powered tactile sensor in an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the sensing principle of the multi-directional tactile sensor in Embodiment 1 of the present invention;

[0030] Figure 3 This is a schematic diagram of the induced voltage output signal when the top of the multi-directional tactile sensor is pressed in Embodiment 1 of the present invention;

[0031] Figure 4 This is a schematic diagram of the induced voltage output signal when the right side of the multi-directional tactile sensor is pressed in Embodiment 1 of the present invention;

[0032] Figure 5 These are the 16 special directions that the multi-directional tactile sensor in Embodiment 1 of the present invention can recognize;

[0033] Figure 6 This is the confusion matrix for the multi-directional tactile sensor in Embodiment 2 of the present invention to identify different objects.

[0034] In the diagram: A - flexible coil layer, B - support layer, C - assembled tactile sensor, D - eight-channel voltmeter, 1 - liquid metal coil, 2 - magnetic block. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0036] In the description of this invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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. Therefore, they should not be construed as limitations on this invention.

[0037] 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0038] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0039] This invention provides a flexible, self-powered tactile sensor based on 3D printing. The self-powered tactile sensor includes a finger-shaped support layer and a flexible coil layer integrally formed by 3D printing, wherein:

[0040] The flexible coil layer includes a flexible thin film and multiple liquid metal coils. The flexible thin film encloses the liquid metal coils inside. The flexible coil layer is fitted over a finger-shaped support layer, so that the liquid metal coils are evenly distributed in various directions outside the support layer, surrounding the finger-shaped support layer. The end of the finger-shaped support layer away from the fingertip has an opening for wearing. A magnetic block is provided at the fingertip end of the finger-shaped support layer. There is a certain gap between the fingertip end of the finger-shaped support layer where the magnetic block is located and the inner wall of the flexible coil layer. When the flexible coil layer is subjected to an external force in any direction, it can drive the liquid metal coil to produce a deformation in the opposite direction of the external force, so as to generate relative movement with the magnetic block, thereby changing the magnetic flux passing through the liquid metal coil and generating an induced electrical signal.

[0041] In a preferred embodiment, the gap between the fingertip of the finger-shaped support layer containing the magnetic block and the inner wall of the flexible coil layer is 2mm-7mm, such as 2mm, 2.3mm, 2.7mm, 3mm, 4mm, 4.5mm, 5mm, 6mm, 7mm, etc. Within this range, the larger the gap distance, the greater the degree of deformation, and the larger the generated induced electrical signal, which is beneficial to improving the sensitivity of the tactile sensor. However, if the gap distance exceeds this range, the generated induced electrical signal will be smaller and difficult to distinguish. If the gap distance is smaller than this range, the flexible film will be difficult to deform sufficiently, thereby affecting the sensitivity of the tactile sensor. If the gap distance is larger than this range, it is not conducive to the mechanical stability of the flexible coil layer.

[0042] In a preferred embodiment, one end of the finger-shaped support layer is provided with a mounting groove with the same shape as the magnetic block. The magnetic block is assembled in the mounting groove, and its N pole or S pole points towards the finger-shaped support layer. Specifically, the shape of the magnetic block can be a cylinder, cuboid, sphere, or other shapes of magnet, and the corresponding mounting groove is also prepared into various shapes that match the shape of the magnetic block.

[0043] In a preferred embodiment, the liquid metal coils include multiple coils and are arranged in an array in the flexible film. For example, when the finger-shaped support layer is columnar, the multiple liquid metal coils form a ring array surrounding the columnar finger-shaped support layer. Additionally, liquid metal coils are located at the bottom surface of the columnar finger-shaped support layer, so that the columnar finger-shaped support layer is completely surrounded by the liquid metal coils.

[0044] In a more preferred embodiment, the number of liquid metal coils is 4 to 7, such as 4, 5, 6, or 7. If the number of liquid metal coils is less than this range, it cannot properly surround the finger-shaped support layer, which will lead to the loss of multi-directional sensing function. If it is greater than this range, the size and structure of the finger-shaped support layer need to be adjusted accordingly, which will increase the difficulty of preparation.

[0045] More preferably, each liquid metal coil has 1 to 3 turns of coil. Using 1, 2, or 3 turns of coil can more effectively collect the induced voltage signal. If the number of turns exceeds this range, the induced voltage signal will be weaker.

[0046] In a preferred embodiment, the remanence of the magnetic block is 0.5T-2T. Within this range, the tactile sensor can obtain a relatively obvious induced electrical signal, which is easy to further analyze, process and distinguish.

[0047] The liquid coil of any of the aforementioned tactile sensors is connected to an external eight-channel voltmeter via an external metal wire to transmit the voltage signal of the liquid metal coil to the eight-channel voltmeter. The eight-channel voltmeter then transmits the voltage signal to a computer, and machine learning algorithms can be used to train the tactile sensor's recognition accuracy.

[0048] According to another aspect of the present invention, in another embodiment, a method for manufacturing a flexible, self-powered tactile sensor based on 3D printing as shown above is also disclosed. The manufacturing method includes the following steps:

[0049] S1 pre-designs different process parameters for the mold to be prepared, uses photocurable resin as raw material, and uses photocurable 3D printing technology to print and prepare finger-shaped support layer, inner mold and outer mold, and the inner surface of the outer mold is provided with multiple coil-shaped protrusions.

[0050] S2 employs Plasma hydrophilic treatment technology to hydrophilically treat the inner and outer molds for a specific time, then remove, cool, and assemble them to obtain a low-adhesion shell mold; specifically, the hydrophilic treatment time is 15min-60min, and after removal and cooling, a low-adhesion shell mold is obtained.

[0051] S3 involves injecting Ecoflex solution (i.e., liquid silicone resin solution) into a low-adhesion shell mold and curing it to obtain a flexible film with coil-shaped microchannels on the outer surface; specifically, the curing process is carried out in an oven at 50℃-70℃ for 15min-60min.

[0052] S4 Injects liquid metal into a coil-shaped microchannel and connects the external metal lead to the liquid metal in the coil-shaped microchannel before curing. Specifically, conductive silver paste is dropped at the connection point and then cured in an oven at 50℃-90℃ for 30min-80min to obtain a flexible film with a liquid metal coil.

[0053] S5 encapsulates the flexible film obtained in step S4 with Ecoflex solution and cures it to prevent the liquid metal coil from leaking out, thereby obtaining a flexible coil layer; specifically, the side of the flexible film on which the liquid metal coil is prepared is encapsulated with Ecoflex solution, and after encapsulation, it is cured in an oven at 50-70℃ for 15-60 minutes to obtain a flexible coil layer.

[0054] S6 installs a magnetic block at one end of the finger-shaped support layer, and fits the flexible coil layer over the finger-shaped support layer. There is a gap between the end of the finger-shaped support layer with the magnetic block and the flexible coil layer, while the rest of the part away from the magnetic block is in close contact with the flexible coil layer.

[0055] In a preferred embodiment, the coil-shaped protrusion structure comprises 4 to 7, and each protrusion structure is a continuous annular coil structure;

[0056] In a more preferred embodiment, the width of the coil-shaped protrusion structure is 0.1mm-1mm, and the height of the coil-shaped protrusion structure is 0.1mm-1mm, such as 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, etc., so that the diameter of the formed liquid metal coil is within this range;

[0057] In a more preferred embodiment, each coil-shaped protrusion structure includes 1 to 3 coils, and the coils are continuous and uninterrupted, so that the coil can be formed with a single injection.

[0058] In a preferred embodiment, in step S6, after the flexible coil layer is fitted over the finger-shaped support layer, the distance between one end of the finger-shaped support layer of the magnetic block and the flexible coil layer is 2mm-7mm, such as 2mm, 2.3mm, 2.7mm, 3mm, 4mm, 4.5mm, 5mm, 6mm, 7mm, etc. Within this size range, the larger the gap distance, the greater the degree of deformation and the larger the generated induced electrical signal, which is beneficial to improving the sensitivity of the tactile sensor. If the gap distance is smaller than this range, it will be difficult for the flexible film to undergo sufficient deformation, thereby affecting the sensitivity of the tactile sensor. If the gap distance is larger than this range, it is not conducive to the mechanical stability of the flexible coil layer.

[0059] In a preferred embodiment, the Ecoflex solution contains at least one of Ecoflex 00-10, Ecoflex 00-20, and Ecoflex 00-30, such as a mixed solution of Ecoflex 00-10 and Ecoflex 00-20, or a mixed solution of Ecoflex 00-10, Ecoflex 00-20, and Ecoflex 00-30, or only one of Ecoflex 00-10, Ecoflex 00-20, or Ecoflex 00-30.

[0060] In a more preferred embodiment, the aforementioned liquid metal is a gallium-based liquid metal, such as gallium indium tin liquid metal, gallium indium liquid metal, etc.

[0061] In a preferred embodiment, in step S5, when encapsulating the flexible film, after encapsulating one layer, it is necessary to cure it in an oven at 50-70°C for 15-60 minutes, and repeat this step 1 to 5 times to obtain a robust flexible coil layer.

[0062] To better illustrate the implementation details of the present invention, the following embodiments are provided to further illustrate the present invention. It should be understood that the following embodiments are only preferred implementation methods and are not intended to limit the scope of protection of the present invention in any way.

[0063] Example 1

[0064] This invention provides a 3D-printed, finger-shaped, multi-directional, flexible, self-powered tactile sensor, the specific manufacturing method of which is as follows:

[0065] (1) Design the parameters of each component of the tactile sensor using modeling software:

[0066] The inner mold model used to prepare the flexible thin film layer is finger-shaped, with a height of 2.5cm and a width of 1.5cm. Its fingertip has a mounting grid (i.e., mounting slot) for mounting a magnetic block, with an inner side length of approximately 5mm. The length of the portion of the rigid support layer that will be fitted with the flexible thin film layer is 5mm longer than the inner length of the flexible thin film layer. The thickness of the flexible thin film layer is 2mm. Based on this, the distance between the outer mold model and the inner mold model after fitting together is determined to be 2mm. The inner wall of the outer mold model has five coil-shaped protrusions. Four coils are arranged in a ring around the circumference of the inner wall of the outer mold, and the other coil is located at the end of the inner wall. Each protrusion structure has one coil, with an outer width of 0.5mm and a height of 0.5mm. The magnetic block required for the tactile sensor is a cube with a side length of 5mm.

[0067] Based on the aforementioned parameters, an outer mold model with microchannels and a rigid support layer model were designed. Then, using photocurable resin as raw material, the aforementioned inner mold, outer mold, and rigid support layer for mounting the flexible thin film layer were prepared by photocurable 3D printing technology.

[0068] (2) Clean the surfaces of the prepared inner and outer molds with ethanol to remove the residual light-curing resin on the surface and in the corners, and then dry them in an oven; treat the cleaned inner and outer molds with Plasma hydrophilic treatment technology for 20 minutes, take them out and cool them to obtain low-adhesion inner and outer molds, and then assemble the two together.

[0069] (3) Inject the pre-prepared Ecoflex 00-10 solution into the gap between the assembled inner and outer molds, and then cure it in a 60℃ oven for 30 minutes to obtain a flexible film with 5 microchannels, and the end of the flexible film away from the fingertip is an opening that allows the finger to enter.

[0070] (4) Gallium-based liquid metal was injected one by one into five microchannels on the flexible film, and a 0.2 mm copper coil was inserted into the liquid metal. Conductive silver paste was dropped at the connection between the copper coil and the liquid metal, and the copper wire was led out to the outside. Then, it was cured in an oven at 60°C for 50 min to obtain a flexible film with a liquid metal coil.

[0071] (5) The flexible film obtained above is then encapsulated using Ecoflex solution. After each encapsulation, it is cured in an oven at 60°C for 20 minutes. This encapsulation step is repeated 3 times to obtain a flexible coil layer.

[0072] (6) Figure 1 As shown, the magnetic block 2 and the flexible coil layer A are sequentially integrated and installed onto the rigid support layer B, so that the N pole of the magnetic block 2 is aligned with the fingertip direction, specifically towards the end of the support layer, thereby obtaining a finger-shaped multi-directional flexible self-powered tactile sensor. In the figure, A in the left figure is a flexible coil layer with a liquid metal coil 1, B is a rigid cylindrical support layer structure with the magnetic block 2 installed, and C in the right figure is the multi-directional flexible self-powered tactile sensor obtained after assembling A and B. In addition, the bottom of the rigid support layer 2 is integrally printed with a base for fixing to the robot finger, and the base also has screw holes for fixing.

[0073] The working principle of the multi-directional self-powered tactile sensor obtained through the above steps is as follows:

[0074] During operation, the obtained multi-directional self-powered tactile sensor is installed on a robot finger. Then, five sets of liquid metal coils are connected to an eight-channel voltmeter via copper wire to collect the voltage signals from the five sets of liquid metal coils in real time. Figure 2As shown, the working principle of the tactile sensor is illustrated. When the tactile sensor is pressed from the top, the magnetic flux through the top coil Ch1 and the four surrounding coils Ch2-Ch4 will change differently. Based on Faraday's law of electromagnetic induction, induced electrical signals will be generated on the Ch1-Ch5 coils respectively. The induced electrical signals are collected by an eight-channel voltmeter D and can be transmitted to other computers for analysis and processing.

[0075] When the top of the tactile sensor Ch1 is pressed, the peak value of the generated induced voltage signal is as follows: Figure 3 As shown, similarly, when the tactile sensor is pressed from the side, different induced electrical signals will be generated on the Ch1-Ch5 coils respectively. For example, when the right side Ch5 of the tactile sensor is pressed, the peak value of the generated induced voltage signal is as follows: Figure 4 As shown; in summary, when the tactile sensor is subjected to external forces from different directions, it generates different sets of induced electrical signals. By analyzing the characteristics of these electrical signal sets, it is statistically determined that the tactile sensor can distinguish approximately 21 different directions of force, including 5 frontal directions and others. Figure 5 The 16 arrows shown indicate specific directions, thus enabling the tactile sensor to perceive touch in multiple directions, thereby giving robots the ability to explore complex and unknown spaces.

[0076] Example 2

[0077] This invention provides a 3D-printed, finger-shaped, multi-directional, flexible, self-powered tactile sensor, the specific manufacturing method of which is as follows:

[0078] (1) Design the parameters of each component of the tactile sensor:

[0079] The finger-shaped inner mold model used to prepare the flexible thin film layer has an external height of 3cm and a width of 2cm. The fingertip also has a mounting grid (i.e., mounting groove) for mounting a magnetic block. The inner side length of the mounting grid is 7mm. The overall length of the part of the rigid support layer to be prepared that covers the flexible thin film layer is 7mm longer than the external length of the flexible thin film layer. The thickness of the flexible thin film layer is 3mm. Based on this, the distance between the outer mold model and the inner mold model after they are assembled is determined to be 3mm.

[0080] The inner wall of the outer mold has three coil-shaped protrusions. The three coils are arranged in a ring around the circumference of the inner wall of the outer mold, and the other coil is located at the end of the inner wall of the outer mold. Each protrusion has one coil, and the outer width and height of each coil are 0.8mm. The magnetic block required for the tactile sensor is a cube with a side length of 7mm.

[0081] Then, using photocurable resin as raw material, the above-mentioned inner and outer molds and rigid support layer are prepared by photocurable printing technology.

[0082] (2) The surfaces of the prepared inner and outer molds are cleaned with ethanol to remove the residual light-curing resin on the surface and in the corners, and then dried in an oven at the same temperature as in Example 1. The cleaned inner and outer molds are treated with Plasma hydrophilic treatment technology for 30 minutes, taken out and cooled to obtain low-adhesion inner and outer molds, and then the two are assembled together.

[0083] (3) The prepared Ecoflex 00-20 solution was injected into the assembled inner and outer molds and cured in an oven at 75°C for 20 minutes to obtain a flexible film with 4 microchannels.

[0084] (4) Gallium-based liquid metal was injected one by one into the four microchannels of the flexible film and led out using a 0.5 mm copper coil. Conductive silver paste was dropped at the connection between the two and cured in an oven at 75°C for 30 min to obtain a flexible film with liquid metal coil.

[0085] (5) The flexible film with liquid metal coil obtained in step (4) is encapsulated with Ecoflex. Each encapsulation is cured in an oven at 75°C for 15 minutes. The encapsulation and curing steps are repeated 4 times to obtain a flexible coil layer.

[0086] (6) The magnetic block and the flexible coil layer are assembled onto the rigid support layer in sequence, and the N pole of the magnetic block is oriented toward the fingertip to obtain a finger-shaped multi-directional flexible self-powered tactile sensor.

[0087] The working principle of the multi-directional self-powered tactile sensor obtained by the aforementioned steps is as follows:

[0088] During operation, the obtained multi-directional flexible self-powered tactile sensor is installed on a robot finger, and then four sets of liquid metal coils are connected to an eight-channel voltmeter through copper wires to collect the voltage signals of the four sets of liquid metal coils in real time.

[0089] Six different objects were pressed against the top of a multi-directional self-powered haptic sensor, including sponge, porous plastic, foam board, cardboard, Ecoflex block, and cured resin. Each object was pressed 500 times, and the resulting induced electrical signals at the Ch1 coil were recorded. 80% of these signals (approximately 400 signals) were used as the training group, and 20% (100 signals) as the test group. Machine learning was then used to train the multi-directional self-powered haptic sensor. Figure 6As shown, after training, the top of the tactile sensor in this embodiment can successfully distinguish different objects with a total accuracy of 97.46%. Similarly, when the tactile sensor is pressed from the side, different induced electrical signals generated on the liquid metal coil at the corresponding position can be collected and the same machine learning training can be performed, so that the multi-directional self-powered tactile sensor obtained in this embodiment has higher recognition accuracy in all directions.

[0090] Example 3

[0091] This invention provides a 3D-printed, finger-shaped, multi-directional, flexible, self-powered tactile sensor, the specific manufacturing method of which includes the following steps:

[0092] (1) Design the parameters of each component of the tactile sensor:

[0093] The finger-shaped inner mold model used to prepare the flexible thin film layer has an external height of 2.7 cm and a width of 1.8 cm. Its fingertips also have a mounting hole for installing a magnetic block, with an internal diameter of 6 mm. The overall length of the portion of the rigid support layer to be prepared that covers the flexible thin film layer is 4.5 mm longer than the external length of the flexible thin film layer. The thickness of the flexible thin film layer is 2.3 mm. Based on this, the distance between the outer mold model and the inner mold model after assembly is determined to be 2.3 mm.

[0094] The inner wall of the outer mold has five coil-shaped protrusions. The five coils are arranged in a ring around the circumference of the inner wall of the outer mold, and the other coil is located at the end of the inner wall of the outer mold. Each protrusion has three coils, and the outer width and height of each coil are 0.2mm. The magnetic block required for the tactile sensor is a sphere with a diameter of 6mm.

[0095] Based on the aforementioned parameters, an inner and outer mold model with microchannels and a rigid support layer model were designed. Then, using photocurable resin as raw material, the aforementioned inner and outer molds and rigid support layer were prepared by photocurable 3D printing technology.

[0096] (2) The prepared inner and outer molds are cleaned with ethanol to remove the residual light-curing resin on the surface and in the corners, and then dried in an oven. The cleaned inner and outer molds are treated with Plasma hydrophilic treatment technology for 40 minutes, and then taken out and cooled to obtain low-adhesion inner and outer molds.

[0097] (3) The prepared Ecoflex 00-30 solution was injected into the assembled inner and outer molds and cured in an oven at 65°C for 25 minutes to obtain a flexible film with 5 microchannels.

[0098] (4) Gallium-based liquid metal was injected one by one into the five microchannels of the flexible film, and a 0.3 mm thick external copper coil was connected to the liquid metal. After adding conductive silver paste at the connection point, the film was cured in an oven at 65°C for 25 min to obtain a flexible film with a liquid metal coil.

[0099] (5) Then Ecoflex is used to encapsulate the flexible film with liquid metal coil. Each encapsulation is cured in an 80°C oven for 10 minutes. The encapsulation and curing steps are repeated 5 times to obtain the flexible coil layer.

[0100] (6) The spherical magnetic block and the flexible coil layer are sequentially integrated into the rigid support layer, and the S pole of the spherical magnetic block is oriented towards the fingertip to obtain a finger-shaped multi-directional flexible self-powered tactile sensor.

[0101] Through the above steps, a multi-directional self-powered tactile sensor is obtained. The working principle of this sensor is as follows:

[0102] During operation, the obtained multi-directional self-powered tactile sensor is fitted onto a finger. Five sets of liquid metal coils are then connected to an eight-channel voltmeter via copper wire to collect voltage signals from the five coils in real time. The top of the multi-directional self-powered tactile sensor is used to press against six different objects: sponge, porous plastic, foam board, cardboard, Ecoflex block, and cured resin. Each object is pressed repeatedly 500 times, and the resulting induced electrical signal sets are recorded. 80% of the induced electrical signal sets (approximately 400 sets of signals) are used as the training group, and 20% (100 sets of signals) as the test group. Machine learning is then used to train the multi-directional self-powered tactile sensor. Similarly, when the sensor is pressed from the side, different induced electrical signals generated on the coils at the corresponding positions are collected, and the same machine learning training is performed, resulting in a multi-directional self-powered tactile sensor with higher recognition accuracy in this embodiment.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flexible, self-powered tactile sensor based on 3D printing, characterized in that, The self-powered tactile sensor includes a finger-shaped support layer and a flexible coil layer integrally formed by 3D printing, wherein: The flexible coil layer includes a flexible thin film and multiple liquid metal coils. The flexible thin film encloses the liquid metal coils inside it. The flexible coil layer is sleeved on the outside of the finger-shaped support layer, so that the liquid metal coils are evenly distributed on the outside of the finger-shaped support layer. A magnetic block is provided at one end of the finger-shaped support layer. There is a gap between the magnetic block and the inner wall of the flexible coil layer. When the flexible coil layer is subjected to an external force in any direction, it can drive the liquid metal coil to produce a deformation in the opposite direction of the external force, so as to generate relative movement with the magnetic block, thereby changing the magnetic flux passing through the liquid metal coil and generating an induced electrical signal.

2. The flexible, self-powered tactile sensor based on 3D printing as described in claim 1, characterized in that, The gap between one end of the support layer where the magnetic block is located and the inner wall of the flexible coil layer is 2mm-7mm.

3. The flexible self-powered tactile sensor based on 3D printing as described in claim 1, characterized in that, The finger-shaped support layer has a mounting groove at one end that is the same shape as the magnetic block. The magnetic block is assembled in the mounting groove, and its N pole or S pole points towards the finger-shaped support layer.

4. A flexible, self-powered tactile sensor based on 3D printing as described in claim 1, characterized in that, The liquid metal coils comprise multiple coils and are uniformly distributed in an array within the flexible film; the number of liquid metal coils is 4 to 7; each liquid metal coil has 1 to 3 turns of coil.

5. A flexible, self-powered tactile sensor based on 3D printing as described in any one of claims 1-4, characterized in that, The remanence of the magnetic block is 0.5T-2T.

6. A method for manufacturing a flexible, self-powered tactile sensor based on 3D printing as described in any one of claims 1-5, characterized in that, The manufacturing method includes the following steps: S1 uses photopolymer 3D printing technology to print the support layer, inner mold and outer mold, and the inner surface of the outer mold has multiple coil-shaped protrusions. S2 uses Plasma hydrophilic treatment technology to hydrophilically treat the inner mold and the outer mold for a specific time, then removes them, cools them, and assembles them to obtain a low-adhesion shell mold. S3 injects the Ecoflex solution into the low-adhesion shell mold and cures it to obtain a flexible film with coil-shaped microchannels on the outer surface. S4 Injects liquid metal into the coil-shaped microchannel, and then connects the external metal leads to the liquid metal in the coil-shaped microchannel and solidifies it to obtain a flexible film with a liquid metal coil. S5 encapsulates the flexible film obtained in step S4 with Ecoflex solution and cures it to prevent the liquid metal coil from leaking out, thereby obtaining a flexible coil layer; S6 Installs a magnetic block at one end of the finger-shaped support layer, and then sleeves the flexible coil layer over the finger-shaped support layer, creating a gap between the magnetic block and the flexible coil layer.

7. A method for manufacturing a flexible, self-powered tactile sensor based on 3D printing as described in claim 6, characterized in that, The coil-shaped protrusion structure comprises 4 to 7 coils; the width of the coil-shaped protrusion structure is 0.1mm-1mm, and the height of the coil-shaped protrusion structure is 0.1mm-1mm; each coil-shaped protrusion structure comprises 1 to 3 coils.

8. A method for manufacturing a flexible, self-powered tactile sensor based on 3D printing as described in claim 6, characterized in that, In step S6, after the flexible coil layer is fitted over the finger-shaped support layer, the distance between the magnetic block and the flexible coil layer is 2mm-7mm.

9. A method for manufacturing a flexible, self-powered tactile sensor based on 3D printing as described in claim 6, characterized in that, The Ecoflex solution contains at least one of Ecoflex 00-10, Ecoflex 00-20, and Ecoflex 00-30; the liquid metal is a gallium-based liquid metal.

10. A method for manufacturing a flexible, self-powered tactile sensor based on 3D printing as described in claim 6, characterized in that, In step S5, the encapsulation steps are repeated 1 to 5 times.

Images