Direct-writing type 3D printing magnetic ink, preparation method and application of direct-writing type 3D printing magnetic ink serving as flexible gripper

Abstract

According to the direct-writing type 3D printing magnetic ink, the preparation method and the application of the direct-writing type 3D printing magnetic ink as the flexible gripper, the direct-writing type 3D printing magnetic ink is prepared from the following raw materials in parts by weight: 0.5 to 5 parts of polydimethylsiloxane prepolymer, 1 to 10 parts of magnetic particles and 0.05 to 0.5 part of emulsifier. The direct-writing type 3D printing magnetic ink provided by the invention can meet the rheological requirement of direct-writing type printing, has better printing precision, meets the adhesive force requirement of non-contact transfer printing, and can be applied to a flexible gripper to grab tiny and fragile articles.

Description

Technical Field

[0001] The present invention relates to the technical fields of 3D printing and robotic grippers, and more specifically, to a direct-write 3D printing magnetic ink, a preparation method thereof, and an application as a flexible gripper. Background Art

[0002] Traditional robotic grippers are rigid and consist of a set of rigid joints and links, but still face many challenges, such as dexterity, control complexity, and the difficulty of handling soft and deformable objects. The progress of soft robotics technology, materials science, and stretchable electronics has enabled the rapid development of flexible grippers. In the past few decades, researchers around the world have explored new methods and technologies for developing and controlling flexible grippers. Flexible grippers mainly include controlling actuation, controlling stiffness, and controlling adhesion. Using these three control techniques, soft robots can mimic the grasping and movement mechanisms of various animals.

[0003] Additive manufacturing, known as 3D printing technology, is a new type of material manufacturing technology that breaks through the limitations of traditional manufacturing technology in terms of efficiency and design, and can achieve high-level customization of materials quickly and accurately. Among them, direct ink writing (DIW) has become the most versatile 3D printing technology. During the direct ink writing process, viscoelastic ink is extruded by depositing nozzles to construct a patterned structure in a computer-predefined manner. To prepare flexible magnetic composites using direct ink writing technology, the 3D printing magnetic ink must meet certain rheological property requirements. The viscosity of the ink needs to satisfy shear thinning, that is, the greater the shear rate, the smaller the viscosity of the ink, so as to facilitate extrusion. And it should satisfy that when the shear stress is small, the storage modulus of the ink is greater than the loss modulus, so as to maintain the shape after printing, and when the shear stress is large, the storage modulus of the ink is less than the loss modulus, so as to facilitate flow during extrusion.

[0004] The challenges faced by flexible grippers include miniaturization, robustness, integration of speed and control. Improving materials, processing methods, and sensing are the mainstream directions in future research. Controlling stiffness with a magnetic field is expected to solve the problems of robustness and speed. Controlling the hardness of the magnetic fluid through a magnetic field can achieve grasping, but the current research in this area is still scarce and the functions are not perfect. Summary of the Invention

[0005] In view of the above problems, the purpose of the present invention is to provide a direct-write 3D printing magnetic ink, a preparation method thereof, and an application as a flexible gripper. The prepared direct-write 3D printing magnetic ink can meet the rheological requirements of direct ink writing, has good printing accuracy, and at the same time meets the adhesion force requirements of non-contact transfer printing.

[0006] The present invention provides a direct-write 3D printing magnetic ink. By weight, the raw materials include: 0.5-5 parts of polydimethylsiloxane prepolymer, 1-10 parts of magnetic particles, and 0.05-0.5 parts of emulsifier.

[0007] Preferably, the emulsifier is at least one of ethylene glycol, propylene glycol, glycerol, diethylene glycol, and isopropanol.

[0008] Preferably, the magnetic particles are Fe 3 O 4 、Fe 2 O 3 、SmCo, NdFeB, SrFe 12 O 19 or at least one of them.

[0009] Preferably, the magnetic particles are NdFeB.

[0010] Preferably, the particle size of the magnetic particles is 1 μm to 20 μm.

[0011] Preferably, by weight, the ratio of the magnetic particles to the polydimethylsiloxane prepolymer is 0.1-10:1, and the ratio of the polydimethylsiloxane prepolymer to the emulsifier is 5-20:1.

[0012] The present invention also provides a preparation method of the direct-write 3D printing magnetic ink for preparing the above-mentioned direct-write 3D printing magnetic ink. The preparation method includes:

[0013] S1: Mix the polydimethylsiloxane prepolymer and the magnetic particles evenly according to a preset ratio to obtain a prepolymer;

[0014] S2: Add the emulsifier to the prepolymer according to a preset ratio, mix evenly, and defoam to obtain the direct-write 3D printing magnetic ink.

[0015] Preferably, in step S1, a high-speed mixer is used to stir and mix the polydimethylsiloxane prepolymer and the magnetic particles. Among them, the rotation speed of the high-speed mixer is 5000 rpm to 20000 rpm, and the stirring time of the high-speed mixer is 0.5 min to 10 min.

[0016] Preferably, in step S2, adding the emulsifier to the prepolymer according to a preset ratio, mixing evenly, and defoaming includes the following steps:

[0017] Use a high-speed mixer to stir and mix the emulsifier and the prepolymer;

[0018] The mixture formed by stirring the emulsifier and the prepolymer is defoamed using a vacuum defoaming machine to obtain the direct-write 3D printing magnetic ink.

[0019] Preferably, the rotation speed of the high-speed mixer is 5000 rpm to 20000 rpm, and the stirring time of the high-speed mixer is 0.5 min to 10 min; the defoaming time of the vacuum defoaming machine is 5 min to 20 min.

[0020] The present invention also provides an application of the 3D printing magnetic ink as a flexible gripper. The flexible gripper is printed using the above-mentioned direct-write 3D printing magnetic ink, which specifically includes:

[0021] Load the direct-write 3D printing magnetic ink into a direct-write 3D printer;

[0022] Print the flexible gripper pattern structure through the direct-write 3D printer according to a preset program to obtain the flexible gripper.

[0023] As can be seen from the above technical solutions, the direct-write 3D printing magnetic ink, preparation method, and application as a flexible gripper provided by the present invention form a 3D printing magnetic ink with a specific component ratio of polydimethylsiloxane prepolymer, magnetic particles, and emulsifier. The viscosity satisfies shear thinning, that is, the greater the shear rate, the smaller the viscosity of the ink, so as to facilitate extrusion; and when the shear stress is small, the storage modulus of the ink is greater than the loss modulus, so as to facilitate maintaining the shape after printing, and when the shear stress is large, the storage modulus of the ink is less than the loss modulus, so as to facilitate flowing during extrusion; the 3D printing magnetic ink meets the rheological property requirements of direct-write printing, has good printing accuracy, can print patterned structures, and is applied to flexible grippers.

[0024] To achieve the above and related purposes, one or more aspects of the present invention include the features described in detail later. The following description and the accompanying drawings illustrate certain exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention aims to include all these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the technical description. Obviously, the drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 It is a viscosity-shear rate curve graph of the magnetic ink at room temperature in Example 1 of the present invention.

[0027] Figure 2 This is the storage / loss modulus - oscillating strain curve graph of the magnetic ink at room temperature in Example 1 of the present invention.

[0028] Figure 3 This is the adhesion force - preloading force curve graph of the magnetic ink before and after applying a magnetic field at room temperature in Example 1 of the present invention.

[0029] Figure 4 This is a physical display of the magnetic ink sample in Example 1 of the present invention.

[0030] Figure 5 This is a physical display diagram of the printer transfer in the example of the present invention.

[0031] Figure 6 This is a schematic flow diagram of the preparation method of the direct writing 3D printing magnetic ink according to the embodiment of the present invention.

[0032] Figure 7 This is the viscosity - shear rate curve graph of the magnetic ink in Comparative Example 1.

[0033] Figure 8 This is the storage / loss modulus - oscillating strain curve graph of the magnetic ink in Comparative Example 1.

[0034] In all the accompanying drawings, the same reference numerals indicate similar or corresponding features or functions. Detailed Description of the Invention

[0035] To make the above - mentioned objects, features, and advantages of the present invention more obvious and understandable, the following will describe the specific embodiments of the present invention in detail with reference to the accompanying drawings.

[0036] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0037] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the description of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of the present invention are obvious to those skilled in the art. The description and embodiments of this application are only exemplary.

[0038] In order to meet the rheological property requirements of magnetic ink, when the shear stress is small, the storage modulus of the ink is greater than the loss modulus to facilitate maintaining the shape after printing, and when the shear stress is large, the storage modulus of the ink is less than the loss modulus to facilitate flowing during extrusion. The present invention proposes a direct-write 3D printing magnetic ink, a preparation method, and an application as a flexible gripper. The prepared direct-write 3D printing magnetic ink can well meet the rheological requirements of direct-write printing, has good printing accuracy, and at the same time meets the adhesion requirements of non-contact transfer.

[0039] The present invention provides a direct-write 3D printing magnetic ink. By weight, the raw materials include: 0.5 - 5 parts of polydimethylsiloxane prepolymer, 1 - 10 parts of magnetic particles, and 0.05 - 0.5 parts of emulsifier.

[0040] In an embodiment of the present invention, the direct-write 3D printing ink prepared from the above raw materials is used for direct-write 3D printing, which well meets the rheological property requirements of direct-write 3D printing, has good printing accuracy, and can print a three-dimensional self-supporting structure and maintain this self-supporting structure during the printing and curing processes.

[0041] Among them, the emulsifier can be at least one of ethylene glycol, propylene glycol, glycerol, diethylene glycol, and isopropanol. After the direct-write 3D printing magnetic ink is magnetized, it can increase the viscosity of the 3D printing ink, change the storage modulus and loss modulus, and broaden the composition range of printable inks; and in this state, the magnetic particles will not settle in the polydimethylsiloxane matrix, which can improve the uniformity of the ink. In addition, 3D printing can print patterned structures and perform patterned transfer.

[0042] Among them, the magnetic particles can be Fe 3 O 4 、Fe 2 O 3 、SmCo, NdFeB, SrFe 12 O 19 or at least one of them. Further, the particle size range of the magnetic particles is 1 μm - 10 μm. The magnetic particles within this particle size range can take into account both the uniformity and printing accuracy of the printing ink.

[0043] In addition, NdFeB is currently the hardest magnetic material with the strongest magnetism at room temperature, having the characteristics of high remanence and high coercivity. It can retain a high residual magnetic flux density after magnetization in a saturation field and is not easily affected by the outside world. It is an ideal magnetic component for preparing flexible magnetic composites. When the magnetic particles are NdFeB, the direct-write 3D printing magnetic ink can obtain better effects.

[0044] Among them, by weight, the ratio of the magnetic particles to the polydimethylsiloxane prepolymer is 0.1-10:1, and the ratio of the polydimethylsiloxane prepolymer to the emulsifier is 5-20:1.

[0045] In the embodiments of the present invention, the 3D printing magnetic ink formed by the above specific polydimethylsiloxane prepolymer, magnetic particles and emulsifier formula, and the above specific component ratio has a viscosity that satisfies shear thinning, that is, the greater the shear rate, the smaller the viscosity of the ink, so as to facilitate extrusion; and it satisfies that when the shear stress is small, the storage modulus of the ink is greater than the loss modulus, so as to facilitate maintaining the shape after printing, and when the shear stress is large, the storage modulus of the ink is less than the loss modulus, so as to facilitate flowing during extrusion; the ink meets the rheological property requirements of direct writing printing, has good printing accuracy, and can print patterned structures.

[0046] In addition, the direct writing 3D printing magnetic ink in the above embodiments of the present invention will deform after being applied with a magnetic field, and this deformation will change its adhesion ability, enabling it to be used as a gripper for grasping and releasing. The present invention also provides a preparation method for the direct writing 3D printing magnetic ink. Figure 6 The flowchart of the preparation method of the direct writing 3D printing magnetic ink according to the embodiment of the present invention is shown.

[0047] As Figure 6 shown, the preparation method for the direct writing 3D printing magnetic ink provided by the present invention prepares the above direct writing 3D printing magnetic ink, and the preparation method includes:

[0048] S1: Mix the polydimethylsiloxane prepolymer and the magnetic particles evenly according to a preset ratio to obtain a prepolymer;

[0049] S2: Add the emulsifier to the prepolymer according to a preset ratio, mix evenly and defoam to obtain the direct writing 3D printing magnetic ink.

[0050] In step S1, a high-speed mixer is used to stir and mix the polydimethylsiloxane prepolymer and the magnetic particles. Among them, the rotation speed of the high-speed mixer is 5000 rpm to 20000 rpm, and the stirring time of the high-speed mixer is 0.5 min to 10 min; so that the prepolymer is mixed more evenly.

[0051] Preferably, in step S2, the adding the emulsifier to the prepolymer according to a preset ratio, mixing evenly and defoaming includes the following steps:

[0052] Use a high-speed mixer to stir and mix the emulsifier and the prepolymer;

[0053] The mixture formed by stirring the emulsifier and the prepolymer is defoamed using a vacuum defoaming machine to obtain the direct-write 3D printing magnetic ink.

[0054] Preferably, the rotation speed of the high-speed mixer is 5000 rpm to 20000 rpm, and the mixing time of the high-speed mixer is 0.5 min to 10 min to make the mixture more uniform. In addition, a vacuum defoaming machine can be used for defoaming, and the defoaming time can be 5 min to 20 min to more effectively remove the bubbles in the ink.

[0055] In the above embodiment, by mixing the raw materials in a specific order and then performing defoaming treatment, the uniformity and stability of the ink during printing and transfer are ensured. By further optimizing the parameters of each step, the uniformity and stability of the ink during printing and pick-and-place are further improved.

[0056] According to another aspect of the present invention, the present invention also provides an application of the 3D printing magnetic ink as a flexible gripper. The flexible gripper is printed using the above-mentioned direct-write 3D printing magnetic ink, which specifically includes:

[0057] Loading the direct-write 3D printing magnetic ink into a direct-write 3D printer;

[0058] Printing the flexible gripper pattern structure through the direct-write 3D printer according to a preset program to obtain the flexible gripper.

[0059] In the embodiment of the present invention, the direct-write 3D printing magnetic ink will deform after applying a magnetic field, and this deformation will change its adhesion ability, enabling it to be used as a gripper for grasping and releasing.

[0060] Further, the printed flexible gripper (printed part) is transferred. The transfer method includes: fixing the printed part and the glass substrate to a three-dimensionally movable transfer table; placing the part to be transferred at a specified position, lowering the transfer table to stick to the part to be transferred; moving the transfer table to the target position, applying a magnetic field, and releasing the transferred part to complete the transfer. In Figure 5 The shown embodiment demonstrates the process of 3D printing magnetic ink from printing to transfer.

[0061] To illustrate the performance of the direct-write 3D printing magnetic ink provided by the present invention, the following examples and comparative examples are described in detail with specific data.

[0062] Example 1

[0063] Preparation method: Pour 2 g of polydimethylsiloxane prepolymer and 0.2 g of diethylene glycol into a 50 mL beaker, then add 8 g of NdFeB magnetic powder. After stirring evenly, put the sample into a vacuum degassing machine to remove air bubbles, and set the degassing time to 15 min to obtain the final direct-write 3D printing magnetic ink. Among them, the raw material polydimethylsiloxane prepolymer is DC184 from Dow Corning Corporation.

[0064] Printing method: 1) Fill the prepared direct-write 3D printing magnetic ink into the extrusion barrel of a direct-write 3D printer. The diameter of the extrusion needle is 0.6 mm, and the extrusion air pressure is set to 0.4 MPa. 2) Perform printing according to the preset program to print a specific pattern to obtain a printed part.

[0065] Among them, the magnetic particles used in this embodiment are NdFeB magnetic powder with a particle size of 5 μm. After magnetizing the direct-write 3D printing magnetic ink obtained in this embodiment, the rheological properties are tested at room temperature.

[0066] Figure 1 The viscosity-shear rate curve of the ink obtained in this embodiment at room temperature is shown, Figure 2 The storage / loss modulus-oscillation strain curve of the ink obtained in this embodiment at room temperature is shown. As Figure 1-2 shown, the viscosity of the ink obtained in this embodiment decreases with the increase of shear stress, and when the oscillation strain is between 0.01% and 2%, the storage modulus of the ink is less than the loss modulus, and when the oscillation strain is between 2% and 100%, the storage modulus of the ink is greater than the loss modulus, meeting the requirements of the rheological properties of the ink for direct-write printing. The obtained patterned printed part can be used as a flexible gripper. As Figure 3 shown, the upper figure is the printed part, which shows high adhesion due to its own viscosity for grasping objects, and the lower figure is the morphology after applying a magnetic field. By changing the stiffness and interface contact area of the magnetic ink through the magnetic field, it is transformed into low adhesion, thereby realizing the release of the target object. Figure 4 The adhesion force test before and after applying the magnetic field further verifies the conversion of the adhesion force of the magnetic ink through the magnetic field.

[0067] Comparative Example 1

[0068] Compared with Example 1, in the process of preparing 3D printing magnetic ink in this comparative example, no magnetization is carried out to obtain the final 3D printing magnetic ink. The rheological properties of the final 3D printing magnetic ink obtained in this comparative example are detected at room temperature. Figure 7 and Figure 8 are respectively the viscosity-shear rate curve of the 3D printing magnetic ink obtained in this comparative example at room temperature and the storage / loss modulus-oscillation strain curve at room temperature. As Figure 7 and Figure 8As shown, the viscosity of the ink in this comparative example decreases with the increase of shear stress. However, within the range of oscillation strain from 0.01% to 100%, the storage modulus of the ink is always less than the loss modulus, which does not meet the requirements of the rheological properties of the ink for direct writing printing.

[0069] The above-described embodiments have described the technical solutions of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, supplements, or substitutions in a similar manner within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A direct writing 3D printing magnetic ink, characterized in that: The raw materials include, by weight: 0.5 to 5 parts of polydimethylsiloxane prepolymer, 1 to 10 parts of magnetic particles and 0.05 to 0.5 parts of emulsifier.

2. The direct writing 3D printing magnetic ink according to claim 1, characterized in that: The emulsifier is at least one of ethylene glycol, propylene glycol, glycerol, diethylene glycol, and isopropanol.

3. The direct writing 3D printing magnetic ink according to claim 1, characterized in that: The magnetic particles are Fe3O4, Fe2O3, SmCo, NdFeB, SrFe 12 O 19 At least one of .

4. The direct writing 3D printing magnetic ink according to claim 1, characterized in that: The magnetic particles are NdFeB.

5. The direct writing 3D printing magnetic ink according to claim 1, characterized in that: The particle size of the magnetic particles is 1 μm to 20 μm.

6. The direct writing 3D printing magnetic ink according to claim 1, characterized in that: In parts by weight, the ratio of the magnetic particles to the polydimethylsiloxane prepolymer is 0.1-10:1, and the ratio of the polydimethylsiloxane prepolymer to the emulsifier is 5-20:

1.

7. A method for preparing direct-write 3D printing magnetic ink, characterized in that: Prepare the direct-write 3D printing magnetic ink as described in any one of claims 1 to 6, the preparation method comprising: S1: uniformly mixing polydimethylsiloxane prepolymer and magnetic particles according to a preset ratio to obtain a prepolymer; S2: adding the emulsifier into the prepolymer in a preset ratio, mixing evenly, and degassing to obtain the direct writing 3D printing magnetic ink.

8. The method for preparing direct writing 3D printing magnetic ink according to claim 7, characterized in that: In step S1, a high-speed stirrer is used to stir and mix the polydimethylsiloxane prepolymer and the magnetic particles, wherein the rotation speed of the high-speed stirrer is 5000 rpm to 20000 rpm, and the stirring time of the high-speed stirrer is 0.5 min to 10 min.

9. The method for preparing direct writing 3D printing magnetic ink according to claim 7, characterized in that: In step S2, the emulsifier is added to the prepolymer according to a preset ratio and mixed evenly and degassed, which includes the following steps: Using a high-speed stirrer to stir and mix the emulsifier and the prepolymer; A vacuum degassing machine is used to degas the mixture formed by stirring the emulsifier and the prepolymer to obtain the direct writing 3D printing magnetic ink.

10. The method for preparing direct writing 3D printing magnetic ink according to claim 9, characterized in that: The rotation speed of the high-speed stirrer is 5000 rpm to 20000 rpm, and the stirring time of the high-speed stirrer is 0.5 min to 10 min; the degassing time of the vacuum degassing machine is 5 min to 20 min.

11. An application of 3D printed magnetic ink as a flexible gripper, characterized in that: The flexible gripper is printed by using the direct writing 3D printing magnetic ink as described in any one of claims 1 to 6, specifically comprising: Loading direct writing 3D printing magnetic ink into a direct writing 3D printer; The flexible gripper is obtained by printing a flexible gripper pattern structure through the direct writing 3D printer according to a preset program.

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