3D printing system for manufacturing magnetic-drive soft robot

Abstract

The invention discloses a 3D printing system for magnetic drive soft robot manufacturing, and belongs to the technical field of soft robot manufacturing and 3D printing. The method aims at solving the problems of programmable space magnetization distribution and three-dimensional structure forming in the manufacturing process of an existing soft robot. Comprising a magnetic field generation unit used for forming a uniform magnetic field with adjustable strength and direction in a printing area, so that magnetic particles of a printing layer in a printing material are aligned to the same direction according to a target magnetization direction; the layer printing unit is used for carrying out light curing on the magnetized printing layer formed by the printing material to obtain a new cured layer; and the forming unit realizes cross-linking with the surface of the printing layer by controlling the position of the formed printing structure and carries the new curing layer to vertically move to be separated from the printing layer, so that multi-layer stacking forming of the magnetic-driven soft-bodied robot is realized. The method is used for printing the magnetic drive soft robot.

Description

Technical Field

[0001] The invention relates to a 3D printing system for manufacturing a magnetically driven soft robot, and belongs to the technical field of soft robot manufacturing and 3D printing. Background Art

[0002] Soft robots are flexible, versatile, and safe to interact with, and are widely used in robotics, bionics, and biomedicine. In particular, magnetically driven soft robots can achieve unfettered movement and manipulation driven by an external magnetic field, thereby achieving functions such as in vivo navigation, targeted drug delivery, and minimally invasive treatment. The versatility of robots depends on their deformation posture and motion mode, which depends on the structure and magnetization distribution design of the robot, but the manufacture of soft robots with complex and precise structures and programmable magnetization distribution remains a major challenge.

[0003] At present, the main manufacturing methods of magnetically driven soft robots include mold method, assembly method and additive manufacturing method. The mold method is to shape the robot through a mold and magnetize it to saturation in a deformed state to obtain a specific magnetization distribution. This method is only suitable for the manufacture of simple robots. The assembly method realizes programmable manufacturing by arranging magnetic voxels, which improves the freedom of robot design and manufacturing, but lacks automated processes, and the manufacturing difficulty increases significantly with the increase of design complexity.

[0004] The development of additive manufacturing technology has brought new possibilities for the manufacture of magnetically driven soft robots. This method relies on an external magnetic field to align magnetic particles in the same direction during the printing process to achieve magnetic programming. Therefore, the uniformity and accuracy of the external magnetic field directly affect the accuracy of magnetic programming and the performance of the robot. Existing magnetic field generating devices mainly include permanent magnets and electromagnetic coil systems. The structure and control of permanent magnets are simple, but it is difficult to generate a large-scale uniform magnetic field. The electromagnetic coil system improves the uniformity and freedom of the magnetic field, but can only produce a limited magnetic field strength. The long-term application of a large-scale, high-intensity, adjustable uniform magnetic field during the printing process remains an urgent problem to be solved.

[0005] In addition, among the photocuring 3D printing methods, the patterned printing method based on digital light processing (DLP) provides higher efficiency and greater freedom in the manufacture of planar two-dimensional robots, but there are still many problems in the manufacture of soft robots with complex three-dimensional structures. First, during the multi-layer stacking process, the separation force between the printed structure and the exposure window may cause defects or even destruction of subtle features and soft structures. At the same time, the printed structure will be disturbed and deformed by the magnetic torque of the external induced magnetic field, resulting in printing failure. Therefore, the manufacture of soft robots with programmable three-dimensional structures and spatial magnetization distribution with high degrees of freedom and complexity still faces many severe challenges. Summary of the invention

[0006] In view of the problems of programmable spatial magnetization distribution and three-dimensional structure forming in the existing soft robot manufacturing process, the present invention provides a 3D printing system for magnetic-driven soft robot manufacturing.

[0007] A 3D printing system for manufacturing magnetically driven soft robots according to the present invention comprises:

[0008] A magnetic field generating unit, used to form a uniform magnetic field with adjustable strength and direction in the printing area, so that the magnetic particles of the printing layer in the printing material are aligned in the same direction according to the target magnetization direction;

[0009] A layer printing unit, used for photocuring the magnetized printed layer formed by the printing material to obtain a new cured layer;

[0010] The molding unit is used to achieve cross-linking with the surface of the printed layer by controlling the position of the formed printed structure, and to carry the new solidified layer to move vertically and separate from the printed layer, thereby realizing multi-layer stacking molding of the magnetically driven soft robot.

[0011] According to the 3D printing system for manufacturing magnetically driven soft robots of the present invention, the magnetic field generating unit includes a permanent magnet array and an electromagnetic coil. The permanent magnet array adopts three coaxial and equidistant Halbach arrays to form a circular ring, and forms a unidirectional magnetic field inside the formed circular ring; the electromagnetic coil is nested inside the permanent magnet array, and the electromagnetic coil is a hollow solenoid. The plane normal uniform magnetic field strength is adjusted by adjusting the excitation current; the inner ring of the electromagnetic coil forms a cylindrical cavity, which serves as a channel for the layer printing unit and the molding unit to print.

[0012] According to the 3D printing system for manufacturing magnetic-driven soft robots of the present invention, the magnetic field generating unit also includes a ball bearing and a transmission belt. The outer ring surface of the permanent magnet array is connected to the ball bearing. The upper Halbach array and the lower Halbach array rotate under the drive of the transmission belt, forming an angle with the middle Halbach array to achieve regulation of the magnetic field intensity; the three Halbach arrays rotate synchronously under the drive of the transmission belt to achieve the generation of two-dimensional magnetic fields in different directions in the plane.

[0013] According to the 3D printing system for manufacturing magnetically driven soft robots of the present invention, the layer printing unit includes a barrel and a DLP optical machine.

[0014] The barrel is loaded with printing material, which consists of an elastomer matrix, a photoinitiator, magnetic particles and a rheology modifier; a printing layer formed by the printing material in the barrel is induced by a target three-dimensional magnetic field generated by a magnetic field generating unit, causing the magnetic particles to rotate to the same direction; a DLP optical machine projects a UV light pattern onto the printing layer according to an exposure pattern, causing the magnetic particles to embed into the elastomer matrix and solidify to obtain a new solidified layer.

[0015] According to the 3D printing system for manufacturing magnetically driven soft robots of the present invention, the molding unit includes a leveling mechanism, a force sensor and a building platform. The building platform is used to accommodate the formed printed structure. The leveling mechanism is used to adjust the building platform and thereby adjust the molding surface of the formed printed structure to be parallel to the exposure window of the printing layer; the force sensor is used to detect the force between the formed printed structure and the exposure window to control the printing process.

[0016] According to the 3D printing system for magnetically driven soft robots of the present invention, the printing process is controlled according to the real-time force feedback of the force sensor; the force sensor is installed on the building platform; each printing process includes three stages:

[0017] Approaching: lowering the building platform until the distance between the formed printing structure and the exposure window is equal to the preset printing layer thickness; the distance between the formed printing structure and the exposure window is determined according to the fluid resistance of the printing material detected by the force sensor;

[0018] Orientation and curing: Stop the building platform from moving, at which point the fluid resistance of the printing material detected by the force sensor is zero; enable the DLP optical machine to project a UV light pattern onto the printing layer to obtain a new curing layer, which is integrated with the currently formed printing structure;

[0019] Separation: The build platform rises, and the newly cured layer is carried vertically by the formed printing structure to separate from the printing layer; the force sensor collects the adhesion force generated by the separation of the newly cured layer and the exposure window. When the adhesion force disappears, it is determined that the newly cured layer is separated from the printing material; at the same time, the printing material in the barrel continues to be filled into the printing area under the action of the vacuum force.

[0020] According to the 3D printing system for manufacturing magnetically driven soft robots of the present invention, the barrel includes a barrel wall, a release film, an adjustment ring and a quartz sheet.

[0021] The adjusting ring is located at a position corresponding to the bottom surface of the printing layer and is fixedly connected to the cylinder wall, and is used to tension the release film to make the release film flat; the quartz sheet is installed under the release film, and is used to limit the downward deformation of the release film to make the thickness of the printing layer uniform; and a pressure equalizing hole is arranged on the quartz sheet;

[0022] During the vertical movement of the newly solidified layer and the separation from the printing material, the build platform rises to cause elastic deformation of the release film, and edge cracks appear at the cross-linked interface between the newly solidified layer and the printing material. The cracks gradually expand toward the middle, thus achieving the separation of the newly solidified layer from the printing material.

[0023] According to the 3D printing system for manufacturing magnetically driven soft robots of the present invention, the rotation angle of the permanent magnet array of the magnetic field generating unit and the excitation current of the electromagnetic coil are calculated based on the target magnetic field and the current magnetic field parameters;

[0024] Controlling the permanent magnet array to rotate according to the rotation angle to generate a two-dimensional magnetic field in a plane, and exciting the electromagnetic coil according to the excitation current to generate a plane normal magnetic field, so that the two-dimensional magnetic field in the plane and the plane normal magnetic field are naturally orthogonal in the plane;

[0025] A 3D Hall probe is used to collect magnetic field data and perform closed-loop control of the magnetic field generating unit.

[0026] According to the 3D printing system for manufacturing magnetically driven soft robots of the present invention, it also includes a supporting structure, which is used to support the inner wall of the formed printed structure in the non-strain concentration area during the multi-layer stacking forming process of the magnetically driven soft robot, and the non-strain concentration area is determined according to the strain distribution cloud map of the formed printed structure under the action of the magnetic field; the supporting structure includes a central axis and a plurality of blades evenly distributed along the circumferential direction of the central axis, the outer edges of the blades are arc-shaped to match the inner wall contour of the magnetically driven soft robot, the circumferential width of the blades is 2 to 10 times the wall thickness of the magnetically driven soft robot, and the distance between adjacent blades is 2 to 10 times the wall thickness of the magnetically driven soft robot.

[0027] According to the 3D printing system for manufacturing magnetic-driven soft robots of the present invention, the printing process of the magnetic-driven soft robots includes:

[0028] Determine the target magnetic field and DLP optical machine exposure pattern based on the three-dimensional structure and magnetization distribution design of the magnetic-driven soft robot;

[0029] The force signal fed back by the force sensor controls the building platform to move to the target position, so that the formed printed structure is cross-linked with the surface of the printed layer; the magnetic particles in the printed layer rotate to the same direction under the induction of the target three-dimensional magnetic field, and then the DLP optical machine is controlled to project the corresponding exposure pattern to solidify the corresponding area of ​​the printed layer to obtain a new solidified layer; then the force signal fed back by the force sensor controls the building platform to move to separate the new solidified layer from the printed layer.

[0030] Beneficial effects of the invention: The system of the invention is used to manufacture a soft robot with a three-dimensional structure and programmable magnetization distribution, and can be widely used in the fields of robotics, bionics, biomedicine, etc.

[0031] The system of the present invention realizes high-precision manufacturing of soft robots with programmable magnetization distribution; designs a hybrid magnetic field generating device, realizes high-precision magnetic field control through a magnetic field decoupling strategy, and improves system stability and adaptability; optimizes printing parameters based on a printing control strategy based on real-time force feedback, improves printing accuracy and success rate; the gradually peeled interface separation strategy reduces the separation force and ensures the printing integrity of complex and fine structures; the system of the present invention optimizes the pressure balance design of the printing area to avoid the influence of the vacuum effect on the printing process; and enhances the printability of thin-walled structures by adding supports that avoid stress concentration points. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the 3D printing system for manufacturing magnetic-driven soft robots according to the present invention;

[0033] Figure 2 It is a 3D printing flow chart of the magnetic drive soft robot of the present invention;

[0034] Figure 3 is a schematic diagram of the control strategy of the magnetic field generating unit; in the figure (B k ,θ k ,j k ) is the spherical coordinate expression of the three-dimensional magnetic field, B k The first is the magnetic field strength, θ k The second is the angle between the magnetic field direction and the positive z-axis, j k The third is the anti-clockwise rotation angle between the projection of the magnetic field direction on the xy plane and the positive x-axis, Dy 1,k is the rotation angle of the upper and lower Halbach arrays, Dy 2,k is the rotation angle of the Halbach array;

[0035] Figure 4 This is a schematic diagram of the three stages of control based on real-time force feedback during the printing process; V is the speed of vertical movement of the build platform, and F d is the fluid resistance of the printing material, F a is the adhesion force generated by the separation of the new cured layer from the exposure window, F s P is the suction force generated by the vacuum area formed by the separation of the newly solidified layer and the exposure window. 0 is standard atmospheric pressure;

[0036] Figure 5 It is a schematic diagram of the separation process of the new solidified layer and the exposure window;

[0037] Figure 6 It is a strain distribution cloud diagram based on the support addition strategy of the support structure;

[0038] Figure 7 It is a schematic diagram of the change of magnetic field intensity of the permanent magnet array with the rotation angle;

[0039] Figure 8 It is a periodic schematic diagram showing that the magnetic field strength of the electromagnetic coil changes linearly with the magnitude of the excitation current;

[0040] Fig. 9 is the angular error distribution diagram of the magnetic field generating unit;

[0041] Fig.10 is the real-time force measurement curve during the printing process;

[0042] Fig.11 Schematic diagram of the design of a butterfly-like magnetic soft robot using the system of the present invention; Dθ up is the upward deformation angle, Dθ down is the downward deformation angle;

[0043] Fig.12 It is a schematic diagram of designing a magnetic robot for a soft capsule with threads using the system of the present invention;

[0044] Fig.13 It is a schematic diagram of a support structure supporting a magnetically driven soft robot. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0047] The present invention will be further described below in conjunction with the accompanying drawings, but is not intended to be a limitation of the present invention.

[0048] Specific implementation method 1. Combination Figures 1 to 6 As shown, the present invention provides a 3D printing system for manufacturing magnetically driven soft robots, comprising:

[0049] A magnetic field generating unit, used to form a uniform magnetic field with adjustable strength and direction in the printing area, so that the magnetic particles of the printing layer in the printing material are aligned in the same direction according to the target magnetization direction;

[0050] A layer printing unit, used for photocuring the magnetized printed layer formed by the printing material to obtain a new cured layer;

[0051] The molding unit is used to achieve cross-linking with the surface of the printed layer by controlling the position of the formed printed structure, and to carry the new solidified layer to move vertically and separate from the printed layer, thereby realizing multi-layer stacking molding of the magnetically driven soft robot.

[0052] In this embodiment, the magnetic field generating unit is a hybrid structure composed of a permanent magnet and an electromagnetic coil, which can generate a high-intensity target uniform magnetic field in real time with low energy consumption through a decoupled magnetic field control strategy. The molding unit can solve the disturbance deformation problem during the printing process through a gradual peeling interface separation strategy and a soft structure support addition strategy, and optimize the printing parameters based on real-time force feedback to improve the printing quality and success rate.

[0053] The manufacturing objectives of the magnetic soft robot in this embodiment include programmable magnetization direction manufacturing and three-dimensional structure multi-layer construction, and the robot is automatically manufactured according to the magnetic field parameters and the exposure pattern sequence. During the programmable magnetization direction manufacturing process, the target magnetic field induces the magnetic particles to align in the same direction, and the DLP projection is used to solidify the target area resin to orient the magnetic particles to achieve a specific magnetization distribution. During the multi-layer construction of the three-dimensional structure, the printed structure is stacked and formed by vertically moving the building platform. The approach, curing and release steps in the printing process are controlled by force feedback to achieve reliable three-dimensional structure manufacturing. In order to meet the long-term working requirements of the system, the particle size of the magnetic particles can be reduced and the viscosity of the printing material can be increased to prepare a long-term stable printing material, and the heat dissipation efficiency of the system can be improved by a water cooling system and an aluminum structure. This embodiment can be used to manufacture three-dimensional thin-walled structures with spatial magnetization distribution, and promote the development of fields such as robotics, bionics and biomedicine.

[0054] Furthermore, the magnetic field generating unit includes a permanent magnet array 11 and an electromagnetic coil 12. The permanent magnet array 11 is formed into a circular ring by three coaxial and equidistantly distributed Halbach arrays, and a unidirectional magnetic field is formed inside the formed circular ring. The electromagnetic coil 12 is nested inside the permanent magnet array 11. The electromagnetic coil 12 is a hollow solenoid, and the plane normal uniform magnetic field strength is adjusted by adjusting the excitation current. The inner ring of the electromagnetic coil 12 forms a cylindrical cavity, which serves as a channel for the layer printing unit and the molding unit to print.

[0055] The magnetic field generating unit can generate a high-intensity uniform magnetic field in its internal printing area, and through the cylindrical cavity, a channel is formed to allow access to the mechanical structure and the optical path. The permanent magnet array 11 can generate a large range of isotropic magnetic fields inside, and the mechanical rotation of the array can adjust the intensity and direction of the generated magnetic field.

[0056] The magnetic field generating unit also includes a ball bearing 13 and a transmission belt 14. The outer ring surface of the permanent magnet array 11 is connected to the ball bearing 13. The upper Halbach array and the lower Halbach array rotate under the drive of the transmission belt 14, forming an angle with the middle Halbach array to achieve the regulation of the magnetic field intensity; the three Halbach arrays rotate synchronously under the drive of the transmission belt 14 to achieve the generation of two-dimensional magnetic fields in different directions in the plane.

[0057] In this embodiment, the cooperation of the ball bearing 13 and the transmission belt 14 enables the permanent magnet array 11 to rotate smoothly. The electromagnetic coil 12 can be equipped with a water cooling system to ensure the working performance and thermal stability of the system. This embodiment provides long-term stable printing materials and efficient heat dissipation design, which can meet the needs of long-term continuous printing.

[0058] Furthermore, the layer printing unit includes a barrel 21 and a DLP optical machine 22.

[0059] The barrel 21 is loaded with printing material, which consists of an elastomer matrix, a photoinitiator, magnetic particles and a rheology modifier; the printing layer formed by the printing material in the barrel 21 causes the magnetic particles to rotate to the same direction under the induction of the target three-dimensional magnetic field generated by the magnetic field generating unit; the DLP optical machine 22 projects a UV light pattern onto the printing layer according to the exposure pattern, so that the magnetic particles are embedded in the elastomer matrix and solidified to obtain a new solidified layer.

[0060] The magnetic particles provide magnetic responsiveness and the rheology modifier increases the viscosity of the elastomer matrix.

[0061] Furthermore, the molding unit includes a leveling mechanism 31, a force sensor 32 and a building platform 33. The building platform 33 is used to accommodate the formed printed structure. The leveling mechanism 31 is used to adjust the building platform 33 and then adjust the molding surface of the formed printed structure to be parallel to the exposure window of the printing layer to ensure printing accuracy; the force sensor 32 is used to detect the force between the formed printed structure and the exposure window, and perform real-time force feedback to control the printing process.

[0062] In this embodiment, combined with Figure 4 As shown, the printing process is controlled according to the real-time force feedback of the formed printed structure during the printing process collected by the force sensor 32; the force sensor 32 is installed on the building platform 33; each printing process includes three stages:

[0063] Approach: lower the building platform 33 until the distance between the formed printing structure and the exposure window is equal to the preset printing layer thickness; the distance between the formed printing structure and the exposure window is determined according to the fluid resistance of the printing material detected by the force sensor 32; the fluid resistance of the printing material detected by the force sensor 32 can ensure the positioning accuracy;

[0064] Orientation and curing: the building platform 33 stops moving, at which time the fluid resistance of the printing material detected by the force sensor 32 disappears and becomes zero; the magnetic field orients the magnetic particles, and the DLP optical machine 22 projects a UV light pattern onto the printing layer to obtain a new curing layer, which is integrated with the currently formed printing structure;

[0065] Separation: The building platform 33 is raised, and the newly solidified layer is carried by the formed printing structure to move vertically and separate from the printing layer. The newly solidified layer is separated from the exposure window to release the adhesion between the interfaces; the force sensor 32 collects the adhesion generated by the separation of the newly solidified layer and the exposure window. When the adhesion disappears, it is determined that the newly solidified layer is separated from the printing material; at the same time, the printing material in the barrel 21 continues to be filled into the printing area under the action of the vacuum force. By controlling the printing parameters through real-time force feedback, optimizing the printing accuracy and separation speed, etc., and monitoring the printing status, the printing accuracy and success rate of the three-dimensional structure can be effectively improved.

[0066] Going a step further, combined Figure 5 As shown, the barrel 21 includes a barrel wall 211, a release film 212, an adjustment ring 213 and a quartz plate 214.

[0067] The adjusting ring 213 is located at a position corresponding to the bottom surface of the printing layer and is fixedly connected to the cylinder wall 211, and is used to tension the release film 212 to make the release film 212 flat; the quartz plate 214 is installed under the release film 212 to limit the downward deformation of the release film 212 to make the thickness of the printing layer uniform; the quartz plate 214 is provided with a pressure equalizing hole 215 to balance the air pressure to prevent the vacuum effect from affecting the upward deformation of the release film 212;

[0068] During the vertical movement of the new solidified layer and the separation from the printing material, the building platform 33 rises to elastically deform the release film 212, and edge cracks are generated at the cross-linked interface between the new solidified layer and the printing material. The cracks gradually expand toward the middle, thereby achieving the separation of the new solidified layer from the printing material.

[0069] Combination Figure 5 As shown, multi-layer printing with low separation force is achieved by gradually releasing the cross-linked interface adhesion between the newly solidified layer and the exposure window. The interface separation strategy of this embodiment can effectively reduce the separation force, avoid defects or damage to the printed structure, and enable the successful molding of precise and fine structures.

[0070] In this embodiment, the rotation angle of the permanent magnet array 11 of the magnetic field generating unit and the excitation current of the electromagnetic coil 12 are calculated based on the target magnetic field and the current magnetic field parameters;

[0071] The permanent magnet array 11 is controlled to rotate according to the rotation angle to generate a two-dimensional magnetic field in a plane, and the electromagnetic coil 12 is excited according to the excitation current to generate a plane normal magnetic field, so that the two-dimensional magnetic field in the plane and the plane normal magnetic field are naturally orthogonal in the plane;

[0072] A 3D Hall probe is used to collect magnetic field data and perform closed-loop control of the magnetic field generating unit.

[0073] In this embodiment, the magnetic field generating unit adopts a decoupling design, and the center plane of the permanent magnet array and the electromagnetic coil coincides with the printing plane, so that the magnetic fields generated by the two magnetic field sources are naturally orthogonal in this plane. Figure 3 As shown in the figure, the rotation angle of the permanent magnet array and the excitation current of the electromagnetic coil are calculated through the target magnetic field and the current magnetic field parameters. The main controller drives the permanent magnet array to rotate according to the angle value to generate an in-plane magnetic field, and excites the coil according to the current value to generate a plane normal magnetic field. At the same time, the 3D Hall probe collects magnetic field data in real time and feeds it back to the host computer to achieve closed-loop control. This strategy generates a three-dimensional precise magnetic field in any direction in a low-energy way.

[0074] This embodiment also includes a supporting structure, which is used to support the inner wall of the formed printed structure in a non-strain concentration area during the multi-layer stacking forming process of the magnetically driven soft robot, and the non-strain concentration area is determined based on the strain distribution cloud map of the formed printed structure under the action of the magnetic field; the supporting structure includes a central axis and a plurality of blades evenly distributed along the circumferential direction of the central axis, the outer edges of the blades are arc-shaped to match the inner wall contour of the magnetically driven soft robot, the circumferential width of the blades is 2 to 10 times the wall thickness of the magnetically driven soft robot, and the distance between adjacent blades is 2 to 10 times the wall thickness of the magnetically driven soft robot.

[0075] The support structure is added at the non-strain concentration point of the magnetic-driven soft robot structure to solve the disturbance deformation problem caused by the magnetic field during the printing process, such as Figure 6 As shown in the figure. The strain concentration point is defined by the finite element simulation stress distribution cloud diagram after the structural deformation under the driving magnetic field. By analyzing the magnetic structure of the magnetic-driven soft robot, the setting position of the support structure is determined, which can not only ensure the stability of the magnetic structure during the printing process, but also will not affect the deformation ability of the structure after the support structure is removed.

[0076] Going further, the printing process of the magnetically driven soft robot includes:

[0077] Determine the target magnetic field and the exposure pattern of the DLP optical machine 22 according to the three-dimensional structure and magnetization distribution design of the magnetic drive soft robot;

[0078] The building platform 33 is controlled to move to the target position according to the force signal fed back by the force sensor 32, so that the formed printed structure is cross-linked with the surface of the printed layer; the magnetic particles in the printed layer are turned to the same direction under the induction of the target three-dimensional magnetic field, and then the DLP light machine 22 is controlled to project the corresponding exposure pattern to solidify the corresponding area of ​​the printed layer to obtain a new solidified layer; then the building platform 33 is controlled to move according to the force signal fed back by the force sensor 32 to separate the new solidified layer from the printed layer.

[0079] Combination Figure 2As shown in the figure, the printing process mainly includes equipment initialization, magnetization programming, pattern curing, multi-region manufacturing and multi-layer stacking. According to the three-dimensional structure and magnetization distribution of the robot, the magnetic field setting and exposure pattern sequence are designed as the input of the printing system. After the equipment is initialized, the force sensor controls the building platform to move to the target position through real-time force feedback, so that the printed structure can be cross-linked with the molding surface. The three-dimensional magnetic field generating device generates a target three-dimensional magnetic field according to the magnetic field setting to induce the magnetic particles in the printing material to turn to the same direction, and then the DLP optical machine projects the corresponding exposure pattern to cure the printing material in this area, so that the magnetic particles are embedded in the elastomer matrix to realize the programming manufacturing of the magnetization direction. Repeat the magnetization programming and pattern curing steps until all the magnetization distributions of the current printing layer are manufactured. Then the building platform moves to separate the current printing layer and refill the resin for the next printing layer manufacturing, and the multi-layer stacking is used to manufacture a three-dimensional structure with a spatial magnetization distribution.

[0080] The present invention will be described in more detail below in conjunction with specific embodiments:

[0081] Example 1: 3D printing for magnetically driven soft robot manufacturing:

[0082] Combination Figure 1 As shown, the magnetic field generating unit is a hybrid structure formed by the combination of a permanent magnet array and an electromagnetic coil. The permanent magnet array is three coaxial and equidistantly distributed Halbach arrays. Each Halbach array is composed of 16 permanent magnets arranged in a special way, which can generate a large-scale uniform magnetic field at the solidification plane. The upper and lower Halbach arrays rotate synchronously, and different magnetic field intensities are generated by adjusting the angle between the Halbach array and the middle Halbach array. The Halbach array combination rotates as a whole to generate two-dimensional magnetic fields in different directions in the plane, and the array is ensured to rotate smoothly by ball bearings and transmission belts. The electromagnetic coil is a hollow solenoid, which adjusts the uniform magnetic field intensity in the normal direction of the plane by the size of the excitation current, and is equipped with a water cooling system to ensure the working performance and thermal stability of the system. The internal space of the solenoid allows access to mechanical structures and optical paths such as the build platform, barrel, and DLP optical machine.

[0083] The leveling mechanism adjusts the molding surface of the building platform to be parallel to the exposure window to ensure printing accuracy. The force sensor is installed above the building platform to provide real-time force feedback between the printing structure and the exposure window to control the printing process. The building platform moves vertically to separate the newly cured layer from the exposure window, and multi-layer stacking is used to achieve the manufacture of three-dimensional structures. The barrel is loaded with printing materials. The printing material consists of an elastomer matrix, a photoinitiator, magnetic particles and a rheology modifier. The magnetic particles are neodymium iron boron particles with a particle size of 1-5μm, and the addition amount is 5-50wt%, preferably 5-20wt%, to provide magnetic responsiveness; the rheology modifier is fumed silica, and the addition amount is 0.5-10wt%, preferably 0.5-2wt%, to increase the viscosity of the elastomer matrix. The DLP optical machine projects a UV light pattern to cure the printing material so that the magnetic particles are embedded in the elastomer matrix.

[0084] Example 2: Process flow and parameter control of magnetic programmable 3D printing:

[0085] Combination Figure 2 As shown, the printing process first performs preparation work, slices the model into I layer patterns according to the printing layer thickness design, and then divides the layer pattern into J magnetization patterns as exposure patterns according to the magnetization distribution design, and the magnetization direction of the area is used as the magnetic field setting. The magnetic field setting and exposure pattern sequence are used as the input of the printing system. The system workflow is as follows:

[0086] The first step is to initialize the device: reset the Halbach array to the positive direction of the y-axis, set the input current of the electromagnetic coil to 0A, and lower the build platform to the target position h on the first floor through force feedback control. 0 .

[0087] The second step is magnetization programming: magnetize the target direction The rotation angle converted to the Halbach array (upper and lower Halbach array Dy 1,ij , Halbach array Dy 2,ij ) and the excitation current I of the electromagnetic coil ij , generating a target three-dimensional magnetic field B on the solidification plane ij Induce the magnetic particles in the printed material to align in the same direction.

[0088] The third step is patterned curing: after the magnetic particles are arranged (1 to 60 seconds, preferably 5 to 10 seconds), the DLP optical machine projects the i-th layer and the j-th exposure pattern. The exposure time of the bottom layer is 10 to 100 seconds, preferably 20 to 60 seconds, and the exposure time of the common layer is 3 to 25 seconds, preferably 5 to 15 seconds, to ensure that the printed material in the exposure area is fully cured and the magnetic particles are embedded in the elastomer matrix.

[0089] Step 4: Printing layer manufacturing: Repeat steps 2 and 3 until the Jth pattern of the current printing layer, that is, all magnetization distributions are manufactured, and the i-th layer is printed.

[0090] Step 5, multi-layer stacking: The building platform is lifted at a speed of 0.01-10 mm / s, preferably 0.1-0.5 mm / s to separate the current printing layer, and wait for 5-60 seconds, preferably 10-20 seconds to complete the resin refilling into the printing area for the next printing layer. Then repeat steps 2-4, and stack multiple layers until a total of I layers are printed.

[0091] Example 3: Magnetic field data and error of a hybrid magnetic field generating device

[0092] Combination Figures 7 to 9 As shown in the figure, the magnetic field data and error of the proposed hybrid magnetic field generating device are tested and analyzed. The upper and lower Halbach arrays that rotate synchronously in the Halbach array combination are regarded as an equivalent Halbach array. The angle between the equivalent array and the middle Halbach array is 2y. The generated magnetic field intensity varies cosine with the rotation angle y, as shown in Figure 7 As shown. The direction of the magnetic field generated is in the xy plane, the maximum field strength exceeds 80mT, and the maximum error does not exceed 2% of the maximum field strength, indicating that the system error is small. The magnetic field strength generated by the electromagnetic coil changes linearly with the excitation current, as shown Figure 8 As shown. The direction of the magnetic field generated is in the z direction, and the maximum field strength exceeds 80mT. The test results show that the magnetic fields generated by the two magnetic field sources have the characteristics of orthogonality, high intensity and high precision, proving the controllability and stability of the device.

[0093] In order to verify the accuracy of the device in generating three-dimensional magnetic fields of arbitrary strength and direction, the angular errors of the generated three-dimensional magnetic fields of different strengths and directions are analyzed, such as Fig. 9 shown. Fig. 9 (a) to (d) show the measurement results of the magnetic field angle error when the magnetic field plane rotates from the xz plane to the yz plane. The results show that the angle error decreases with the increase of the magnetic field strength. When the magnetic field strength is greater than 80mT, the angle error does not exceed 1.2°. Comprehensive analysis shows that the hybrid magnetic field generating device can stably and accurately generate a three-dimensional magnetic field in any direction, providing important support for robotic magnetization programming manufacturing.

[0094] Example 4: Real-time force feedback curve during printing:

[0095] like Fig.10 As shown, this embodiment shows a real-time force feedback curve during the printing process. The curve is based on the force sensor installed on the building platform to record the force feedback in real time, and combines the force curves of the three stages of approach, orientation and curing and separation to achieve precise printing control.

[0096] During the approach phase, the building platform gradually descends to the set initial printing layer thickness (20-500 μm, preferably 50-200 μm). When approaching the target position, the force sensor detects the rapidly increasing fluid resistance. When the fluid resistance increases to exceed the target value, it indicates that the distance between the printed structure and the exposure window has reached the target printing layer thickness, triggering the platform to stop descending to ensure the printing position accuracy.

[0097] During the orientation and curing stage, the fluid resistance disappears rapidly, and the magnetic field induces the magnetic particles in the printing material to align in an oriented manner. The DLP optical machine then projects the UV light pattern to solidify the printing material, thereby jointly realizing the magnetization programming of the target area.

[0098] During the separation stage, the printing platform rises at a speed of 0.01 to 10 mm / s, preferably 0.1 to 0.5 mm / s, gradually releasing the adhesion between the newly solidified layer and the exposure window. In the early stage of separation, cracks appear at the edge of the cross-linked interface and gradually expand toward the center. The adhesion force is gradually released to maintain the separation force at a low value, ensuring the stability of the separation process, effectively avoiding damage to the printed structure, and ensuring printing accuracy and structural integrity.

[0099] The real-time force feedback curve can effectively optimize the parameter control and state monitoring during the printing process, improve the printing success rate and quality of complex and fine three-dimensional structures, and verify the applicability of the printing control strategy based on real-time force feedback to the multi-layer stacking 3D printing process, providing a reliable basis for further improving printing accuracy and efficiency. This force feedback mechanism is suitable for high-precision light-curing 3D printing scenarios of various complex soft structures and has broad application prospects.

[0100] Example 5: Precision and fine structure design and application effect based on interface separation strategy:

[0101] like Fig.11 and Fig.12 As shown, this embodiment realizes the manufacture of three-dimensional structures with precise and subtle features based on the interface separation strategy, and applies these features to the design of magnetic soft robots, giving them excellent controllability and functionality.

[0102] The butterfly-like magnetic soft robot is designed with symmetrical wings and delicate antennae. Fig.11 (a) As shown. Through precise magnetization programming, the wings can produce asymmetric up and down flapping movements, imitating the real flying movements of butterflies, such as Fig.11 (b) As shown. The main body of the threaded soft capsule magnetic robot is a tubular structure with a fine thread structure on the surface. The radial net magnetic moment is achieved through a specific magnetization distribution, as shown in Fig.12(a) As shown. Under the action of the external magnetic field, the cross-section of the capsule structure changes from a circle to an ellipse, squeezing the internal cavity, as shown in Fig.12 (b) The simulation and experimental results of this embodiment both show consistent deformation behavior, proving the accuracy and reliability of the manufacturing method proposed in the present invention.

[0103] This example shows that the proposed interface separation strategy effectively solves the defects and damage problems that may be caused by separation force in the manufacture of precise and fine-featured three-dimensional structures, and realizes the high-precision manufacturing and multifunctional integration of magnetic soft robots. This strategy improves the manufacturing freedom and precision of soft three-dimensional structures, enables the successful formation of optimized magnetic distribution and fine structural design, and provides strong support for the development of bionics, biomedicine and intelligent soft robots.

[0104] Example 6: Thin-wall structure design and application effect based on support addition strategy:

[0105] Combination Fig.12 As shown, this embodiment provides a thin-walled structure design solution based on the support addition strategy. First, a finite element analysis is performed to calculate the strain (LE) distribution cloud map of the structure under the action of a magnetic field, and the strain concentration area (LE>90% Max) is identified. Figure 6 Add support structures in non-strain concentration areas, such as Fig.13 (a) is shown. The width of the support structure is 2 to 10 times the wall thickness, preferably 2 to 3 times, and the distance between adjacent support points is 2 to 10 times the wall thickness, preferably 3 to 6 times. This support strategy ensures the structural stability during the printing process and effectively avoids interference deformation and fracture problems. After printing, the soft support structure can be easily cut off without negatively affecting the deformation ability and functionality of the structure.

[0106] Thin-walled structures manufactured using support strategies such as Fig.13 As shown in (b), the manufacturing of a magnetic thin-walled structure with a wall thickness of only 200 μm was successfully achieved. The structure exhibited excellent magnetic response characteristics under the action of a magnetic field. This support strategy ensures the structural stability during the printing process and effectively avoids interference deformation and fracture problems. After printing, the soft support structure can be easily cut off without negatively affecting the deformation ability and functionality of the structure. It is proved that this support addition strategy provides reliable support for the realization of high-precision and stable printing of magnetic thin-walled soft structures.

[0107] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A 3D printing system for manufacturing magnetically driven soft robots, characterized in that: include, A magnetic field generating unit, used to form a uniform magnetic field with adjustable strength and direction in the printing area, so that the magnetic particles of the printing layer in the printing material are aligned in the same direction according to the target magnetization direction; A layer printing unit, used for photocuring the magnetized printed layer formed by the printing material to obtain a new cured layer; The molding unit is used to achieve cross-linking with the surface of the printed layer by controlling the position of the formed printed structure, and to carry the new solidified layer to move vertically and separate from the printed layer, thereby realizing multi-layer stacking molding of the magnetically driven soft robot.

2. The 3D printing system for manufacturing magnetically driven soft robots according to claim 1, characterized in that: The magnetic field generating unit comprises a permanent magnet array (11) and an electromagnetic coil (12); the permanent magnet array (11) is formed into a circular ring shape by using three coaxial and equidistantly distributed Halbach arrays, and a magnetic field in the same direction is formed inside the formed circular ring; the electromagnetic coil (12) is nested inside the permanent magnet array (11); the electromagnetic coil (12) is a hollow solenoid, and the uniform magnetic field intensity in the plane normal direction is adjusted by adjusting the excitation current; the inner ring of the electromagnetic coil (12) forms a cylindrical cavity, which serves as a channel for the layer printing unit and the molding unit to perform printing.

3. The 3D printing system for manufacturing magnetically driven soft robots according to claim 2, characterized in that: The magnetic field generating unit further comprises a ball bearing (13) and a transmission belt (14); the outer ring surface of the permanent magnet array (11) is connected to the ball bearing (13); the upper Halbach array and the lower Halbach array rotate under the drive of the transmission belt (14) and form an angle with the middle Halbach array to achieve regulation of the magnetic field intensity; the three Halbach arrays rotate synchronously under the drive of the transmission belt (14) to achieve the generation of two-dimensional magnetic fields in different directions within a plane.

4. The 3D printing system for manufacturing magnetically driven soft robots according to claim 1, characterized in that: The layer printing unit comprises a material barrel (21) and a DLP optical machine (22). The barrel (21) is loaded with printing material, which is composed of an elastomer matrix, a photoinitiator, magnetic particles and a rheology modifier; a printing layer formed by the printing material in the barrel (21) is induced by a target three-dimensional magnetic field generated by a magnetic field generating unit to cause the magnetic particles to rotate in the same direction; a DLP optical machine (22) projects a UV light pattern onto the printing layer according to an exposure pattern, so that the magnetic particles are embedded in the elastomer matrix and cured to obtain a new cured layer.

5. The 3D printing system for manufacturing magnetically driven soft robots according to claim 4, characterized in that: The molding unit comprises a leveling mechanism (31), a force sensor (32) and a building platform (33); the building platform (33) is used to accommodate a molded printing structure; the leveling mechanism (31) is used to adjust the building platform (33) and thereby adjust the molding surface of the molded printing structure to be parallel to the exposure window of the printing layer; the force sensor (32) is used to detect the force between the molded printing structure and the exposure window to control the printing process.

6. The 3D printing system for manufacturing magnetically driven soft robots according to claim 5, characterized in that: The printing process is controlled according to the real-time force feedback of the force sensor (32); the force sensor (32) is installed on the building platform (33); each printing process includes three stages: Approaching: lowering the building platform (33) until the distance between the formed printed structure and the exposure window is equal to the preset printing layer thickness; The distance between the formed printing structure and the exposure window is determined according to the fluid resistance of the printing material detected by the force sensor (32); Orientation and curing: stopping the movement of the building platform (33), at which time the fluid resistance of the printing material detected by the force sensor (32) is zero; causing the DLP optical machine (22) to project a UV light pattern onto the printing layer to obtain a new curing layer, wherein the new curing layer is integrated with the currently formed printing structure; Separation: the building platform (33) is raised, and the newly solidified layer is carried by the formed printing structure to move vertically and separate from the printing layer; the force sensor (32) collects the adhesion force generated by the separation of the newly solidified layer and the exposure window, and when the adhesion force disappears, it is determined that the newly solidified layer is separated from the printing material; at the same time, the printing material in the barrel (21) continues to be filled into the printing area under the action of the vacuum force.

7. The 3D printing system for manufacturing magnetically driven soft robots according to claim 5, characterized in that: The barrel (21) comprises a barrel wall (211), a release film (212), an adjustment ring (213) and a quartz plate (214). The adjusting ring (213) is located at a position corresponding to the bottom surface of the printing layer and is fixedly connected to the cylinder wall (211), and is used to tension the release film (212) to make the release film (212) flat; the quartz plate (214) is installed below the release film (212) and is used to limit the downward deformation of the release film (212) to make the thickness of the printing layer uniform; A pressure equalizing hole is provided on the quartz plate (214); During the process of vertical movement of the newly solidified layer and separation from the printing material, the building platform (33) rises to cause elastic deformation of the release film (212), and edge cracks are generated at the cross-linked interface between the newly solidified layer and the printing material. The cracks gradually expand toward the middle, thereby achieving separation of the newly solidified layer from the printing material.

8. The 3D printing system for manufacturing magnetically driven soft robots according to claim 2, characterized in that: The rotation angle of the permanent magnet array (11) of the magnetic field generating unit and the exciting current of the electromagnetic coil (12) are calculated and obtained according to the target magnetic field and the current magnetic field parameters; Controlling the permanent magnet array (11) to rotate according to the rotation angle to generate a two-dimensional magnetic field in a plane, and exciting the electromagnetic coil (12) according to the excitation current to generate a plane normal magnetic field, so that the two-dimensional magnetic field in the plane and the plane normal magnetic field are naturally orthogonal in the plane; A 3D Hall probe is used to collect magnetic field data and perform closed-loop control of the magnetic field generating unit.

9. The 3D printing system for manufacturing magnetically driven soft robots according to claim 1, characterized in that: It also includes a supporting structure, which is used to support the inner wall of the formed printed structure in the non-strain concentration area during the multi-layer stacking forming process of the magnetically driven soft robot, and the non-strain concentration area is determined according to the strain distribution cloud map of the formed printed structure under the action of the magnetic field; the supporting structure includes a central axis and a plurality of blades evenly distributed along the circumferential direction of the central axis, the outer edges of the blades are arc-shaped to match the inner wall contour of the magnetically driven soft robot, the circumferential width of the blades is 2 to 10 times the wall thickness of the magnetically driven soft robot, and the distance between adjacent blades is 2 to 10 times the wall thickness of the magnetically driven soft robot.

10. The 3D printing system for manufacturing magnetically driven soft robots according to claim 5, characterized in that: The printing process of the magnetically driven soft robot includes: Determine the target magnetic field and the DLP optical machine (22) exposure pattern according to the three-dimensional structure and magnetization distribution design of the magnetic-driven soft robot; The building platform (33) is controlled to move to the target position according to the force signal fed back by the force sensor (32), so that the formed printed structure is cross-linked with the surface of the printed layer; the magnetic particles in the printed layer are turned to the same direction under the induction of the target three-dimensional magnetic field, and then the DLP optical machine (22) is controlled to project the corresponding exposure pattern to solidify the corresponding area of ​​the printed layer to obtain a new solidified layer; and then the building platform (33) is controlled to move according to the force signal fed back by the force sensor (32), so as to separate the new solidified layer from the printed layer.

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