Magnetic control liquid metal burr transfer stamp and transfer method

Abstract

The application first proposes a magnetic control liquid metal spike transfer printing stamp and a transfer printing method. The stamp is composed of a base and a spike-shaped stamp body. The stamp body is composed of a mixed fluid of pre-magnetized spike-shaped liquid metal and micron-sized iron powder. The transfer printing method is as follows: (1) during picking up, no magnetic field is applied, the spikes of the stamp are soft and easy to bend and deform; the stamp is brought into contact with the element, and the strong surface tension of the liquid metal is used to pick up the element from the donor substrate; (2) during printing, an external magnetic field is applied, the spikes become sharp, the rigidity increases, the instantaneous deformation of the stamp reduces the interfacial adhesion and generates an ejection force, so as to release the element. The stamp has a simple structure and low cost, the magnetic control response speed is fast, and non-contact transfer printing can be realized at room temperature; the liquid metal stamp has strong shape adaptability and can transfer two-dimensional and three-dimensional elements; by changing the action range of the magnetic field, the method can realize efficient global transfer printing and precise patterned transfer printing.

Description

TECHNICAL FIELD

[0001] The present application relates to a transfer printing technology, in particular to a magnetic control liquid metal spur transfer printing stamp and a transfer printing method, which can be used for deterministic assembly of any patterned two-dimensional or three-dimensional elements. BACKGROUND

[0002] Transfer integration technology is a highly efficient heterogeneous integration technology, which is combined with planar micro-nano processing to prepare new micro-nano information electronic devices, and has good application prospects in the field of wearable integrated devices and Internet of Things.

[0003] There are many existing transfer integration technologies, which can be divided into contact transfer printing and non-contact transfer printing according to whether the element is in direct contact with the host substrate during printing. The printing process of contact transfer printing is affected by the adhesion of the substrate and the element, and the transfer printing can achieve accurate positioning. The printing of non-contact transfer printing is not affected by the substrate, and selective transfer printing can be achieved, but the transfer printing accuracy needs to be improved.

[0004] Transfer printing technologies can also be classified according to different transfer media, such as micro-mechanical operation (Dechev N, Cleghorn W L, Mills J K. Microassembly of 3-D microstructures using a compliant, passive microgripper [J]. JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, 2004, 13(2): 176-189.), tape transfer, polymer stamp transfer (Luo H Y, Linghu C H, Song J Z. Review of transfer mechanics of stretchable flexible inorganic electronic devices [J]. Chinese Science Bulletin: Physics, Mechanics and Astronomy, 2018, 48(09): 134-148.), and liquid transfer. Micro-mechanical operation transfer and tape transfer are both contact transfer. Micro-mechanical transfer has high precision, but it is difficult to manipulate thin, flexible, brittle, small components, has high transfer cost, low efficiency, and is easy to cause physical damage to the components. Tape transfer can be used for large-area transfer in parallel, and the transfer process introduces chemical regulation methods, with a larger adhesion regulation range. The most widely used tape transfer at present is water-soluble tape (Sim K, Chen S, Li Y, et al. High fidelity tape transfer printing based on chemically induced adhesive strength modulation [J]. SCIENTIFIC REPORTS, 2015, 5: 16133.) and thermal release tape (Yan Z C, Pan T S, Xue M, et al. Thermal release transfer printing for stretchable conformal bioelectronics [J]. ADVANCED SCIENCE, 2017, 4(11): 1700251.), but additional chemical or heating treatment is required for the components during the transfer process, which can cause chemical contamination of the components, affect the performance of the components, and the tape cannot be reused.

[0005] Polymer stamp transfer technology is the most popular transfer technology, which separates functional components from the original substrate by polymer stamp and transfers and prints them onto the use substrate. The adhesion between the stamp and the component during picking should be greater than that between the component and the substrate, and the adhesion between the stamp and the component during printing should be less than that between the component and the substrate. The adhesion between the component and the substrate is usually uncontrollable, so regulating the adhesion between the stamp and the component interface has become the key to developing polymer stamp transfer technology.

[0006] According to different force regulation principles, the polymer stamp transfer printing technology has developed rate-dependent dynamic controllable transfer printing technology (Meitl M A, Zhu Z T, Kumar V, et al. Transfer printing by kinetic control of adhesion to an elastomeric stamp [J]. NATURE MATERIALS, 2006, 5(1): 33-38.), load-enhanced transfer printing technology (Cheng H Y, Wu J, Yu Q M, et al. An analytical model for shear-enhanced adhesiveless transfer printing [J]. MECHANICS RESEARCH COMMUNICATIONS, 2012, 43: 46-49.), and curvature-controlled transfer printing technology (Cho S, Kim N, Song K, et al. Adhesiveless transfer printing of ultrathin microscale semiconductor materials by controlling the bending radius of an elastomeric stamp [J]. LANGMUIR, 2016, 32(31): 7951-7957.). These three transfer printing technologies respectively require control of the stamp peeling speed, the applied shear load, and the curvature of the stamp, and have high dependence on the operation precision and great regulation difficulty.

[0007] According to different stamp design, high polymer stamp developed the use of mushroom-shaped microstructure to reduce the stress concentration at the boundary, to inhibit the occurrence of boundary crack, so as to enhance the adhesion of support stamp transfer printing technology (Kim S, Carlson A, Cheng H Y, et al. Enhanced adhesion with pedestal-shaped elastomeric stamps for transfer printing [J]. APPLIED PHYSICS LETTERS, 2012, 100(17): 171909.); microcolumn array stamp transfer printing technology imitating the design of gecko foot bottom fiber-like setae (Jeong J, Kim J, Song K, et al. Geckoprinting: assembly of microelectronic devices on unconventional surfaces by transfer printing with isolated gecko setal arrays [J]. JOURNAL OF THE ROYAL SOCIETY INTERFACE, 2014, 11(99): 20140627.); based on the proportionality of van der Waals force to area, inflatable stamp transfer printing technology (Kim S, Wu J A, Carlson A, et al. Microstructured elastomeric surfaces with reversible adhesion and examples of their use in deterministic assembly by transfer printing [J]. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2010, 107(40): 17095-17100.).

[0008] The above transfer printing technologies need direct contact between the elements and the receiving substrate during printing, with high printing precision; but the contact type high polymer stamp transfer printing technology usually needs to apply some load to the stamp to regulate adhesion during printing, and the elements are easy to be wrinkled or broken under pressure or shear force between the stamp and the substrate.

[0009] To avoid damage to components caused by extrusion during printing, researchers proposed a laser-driven transfer technology based on thermal mismatch by introducing external drives such as thermal control and magnetic control and optimizing the stamp design. (Huang Y, Zheng N, Cheng ZG, et al. Direct laser writing-based programmable transfer printing via bioinspired shape memory reversible adhesive[J]. ACS APPLIED MATERIALS &

[0010] INTERFACES, 2016, 8(51): 35628-35633.), Laser-driven programmable non-contact transfer printing of objects onto arbitrary receivers via an active elastomeric microstructured stamp[J]. NATIONAL SCIENCE REVIEW, 2020, 7(2): 296-304.), Aphid-inspired magnetic transfer technology[J]. SOFT MATTER, 2019, 15(1): 30-37.

[0011] These transfer technologies offer fast response, continuously adjustable adhesion, and non-contact transfer capabilities. The transfer printing process is unaffected by the substrate and allows for selective, programmable printing. Polymer stamp transfer technology enables large-scale transfer of massive quantities of micro-components using large-area stamps. The stamps are reusable, avoiding the use of adhesives and preventing chemical contamination of the components. However, sufficient pressure still needs to be applied during pickup to activate van der Waals forces, resulting in shear forces at the interface due to the Poisson effect. When transferring complex three-dimensional or thin-film devices, these interfacial shear forces may cause wrinkling or breakage, damaging the device's performance. Summary of the Invention

[0012] The present application aims at the shortcomings of the existing high polymer stamp transfer printing technology, and proposes a magnetic control liquid metal spur transfer printing stamp and a transfer printing method. The stamp structure is simple and low in cost, the magnetic control response speed is fast, non-contact transfer printing can be realized at normal temperature environment, the liquid metal stamp has strong shape adaptability, and two-dimensional and three-dimensional elements can be transferred, the transfer printing method of the present application can realize efficient global transfer printing and accurate patterned transfer printing by changing the action range of the magnetic field.

[0013] The present application adopts the following technical solutions:

[0014] A magnetic control liquid metal spur transfer printing stamp, which is composed of a base and a spur-shaped stamp body; a groove is arranged on the base, and the spur-shaped stamp body is arranged in the groove. The material of the spur-shaped stamp body is a mixed fluid composed of pre-magnetized spur-shaped liquid metal and micron-sized iron powder. The main body of the stamp is liquid metal fused with magnetic particles, and the surface is wrapped with an oxide layer to maintain the spur-shaped shape. When there is no magnetic field, the spur array composed of magnetic particles and liquid metal mainly shows the characteristics of liquid metal, low rigidity, smooth shape and strong fluidity. After applying a magnetic field, the magnetic control liquid metal shows a spur shape, high spur rigidity, sharp shape and low surface adhesion.

[0015] The specific transfer printing method is as follows: 1) during picking up, no magnetic field is applied, and the stamp is close to the element; after the stamp contacts the element, the element is picked up by using the surface tension of the liquid metal; 2) during printing, different intensity magnetic fields are applied to make the spur sharp and the rigidity large, so that the instantaneous deformation of the stamp can further reduce the interfacial adhesion and generate an ejection force, thereby releasing the element.

[0016] The external magnetic field can be a global magnetic field or a local magnetic field. Under the global magnetic field, large-scale and high-efficiency transfer printing can be realized; under the local magnetic field, programmable patterned transfer printing can be realized.

[0017] The base of the stamp can be made of non-magnetic acrylic, glass or other materials, which can ensure that it is not easy to deform and is not affected by the magnetic field.

[0018] The material of the spur-shaped stamp body is a mixture of liquid metal and magnetic particles, wherein the liquid metal can be one or more of gallium, indium and their alloys, and the magnetic particles can be one or more of iron, cobalt and nickel. The mass ratio of the magnetic particles to the liquid metal is (0.05-0.25):1.

[0019] Preferably, the stamp base can be made of easily processed acrylic thin plate with good light transmission, which is convenient for monitoring the transfer printing process.

[0020] Preferably, the liquid metal can be selected from the EGaIn alloy with a mass ratio of 3:1, which is liquid at room temperature, has strong fluidity, and has good adaptability to the shape of the element when picking up; the magnetic particles can be selected from 1-10 micron iron powder which is low in cost and easy to purchase; the iron powder and the liquid metal can be mixed in different proportions to obtain the stamp with adjustable magnetism and fluidity.

[0021] Preferably, the preparation method of the burr-shaped stamp body is as follows: the liquid metal and the magnetic particles are mixed in proportion, the magnetic particles are fully contacted with the oxide layer on the surface of the liquid metal, hydrochloric acid with a concentration of 4 mol / L-8 mol / L is added, and the mixture is fully stirred on a magnetic stirrer with a preset temperature of 40-60 DEG C until the solution is clear; the mixture of the magnetic metal particles and the liquid metal is taken out and cleaned with deionized water (at least 3 times) (since the liquid metal has strong surface tension and the magnetic particles have been internalized into the liquid metal, the magnetic fluid mixture is adsorbed on the rotor and can be taken out by the rotor), dried (such as using dust-free paper to absorb the moisture on the surface of the material), and then placed in the groove of the base, and then disturbed by the magnetic field of the permanent magnet, and the burr-shaped formation is observed, and then placed above the permanent magnet for 1-3 days to form a dense oxide film, thereby obtaining the burr-shaped stamp body magnetic field. The mixture is in a spread fluid state when it is just placed in the groove of the base, and then forms a radial sharp burr shape along the magnetic induction lines by the disturbance of the magnetic field of the permanent magnet, and then continues to be placed above the permanent magnet for 1-3 days, and a dense oxide film is formed on the surface to maintain the burr shape of the stamp body.

[0022] Preferably, the liquid metal EGaIn is mixed with the iron powder in a mass ratio of 4:1.

[0023] Generally, the mixture of the liquid metal and the magnetic particles has strong fluidity, and after the magnetic field is removed, it is not easy to maintain the burr-shaped shape formed spontaneously under the action of the magnetic field by gravity; therefore, it needs to be placed in the magnetic field for 1-3 days to react with air to form a dense oxide film, so as to maintain the burr shape. If the stamp is inverted (the burr of the stamp body is downward), the placement time in the magnetic field can be shortened (one day).

[0024] The beneficial effects of the present application are:

[0025] The stamp is simple to prepare and can realize non-contact transfer at room temperature; compared with the polymer stamp, the magnetic liquid metal burr transfer stamp has good shape adaptability, small physical damage to the element, and can be used for the transfer of two-dimensional and three-dimensional objects; under the action of the magnetic field, it can realize high-efficiency global transfer and precise selective transfer.

[0026] CN 113119149 A is a patent application similar to the present application, which only uses magnetic field to transfer the magnetic liquid metal in the whole transfer process, and does not involve the change of liquid metal shape and material performance by magnetic field. It uses the solid-liquid phase change of liquid metal to switch adhesion in the picking and printing process, and the phase change needs to regulate temperature, the heating and cooling process has slow response speed, low printing efficiency and complex operation. The present application changes the ratio and manufacturing method, designs the shape of the stamp body as a sharp structure, picks up by using the surface tension of liquid metal, has good shape adaptability, and will not damage the elements; and changes the shape and rigidity of the stamp by using magnetic field, so as to control adhesion and realize printing of elements. The response speed of magnetic field control is fast (<0.5s), the transfer efficiency is high, and batch printing and selective printing can be realized by applying global magnetic field or local magnetic field. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is the structural schematic diagram of the minimum unit of the magnetic control liquid metal burr transfer printing stamp proposed by the present application.

[0028] Figure 2 is the magnetic field response schematic diagram of the magnetic control liquid metal burr transfer printing stamp proposed by the present application.

[0029] Figure 3 is the transfer principle diagram of the magnetic control liquid metal burr transfer printing stamp proposed by the present application.

[0030] Figure 4 is the structural schematic diagram of the array type magnetic control liquid metal burr transfer printing stamp proposed by the present application.

[0031] Figure 5 is the flow chart of applying global magnetic field to realize large-scale and high-efficiency transfer of the array type magnetic control liquid metal burr transfer printing stamp proposed by the present application.

[0032] Figure 6 is the flow chart of applying selective magnetic field to realize programmable printing of the array type magnetic control liquid metal burr transfer printing stamp proposed by the present application.

[0033] In the figure: 1-base, 2-stamp body, 2-1-stamp body without magnetic field effect, 2-2-stamp body under magnetic field effect, 3-external magnetic field effect, 3-1-global magnetic field effect, 3-2-local magnetic field effect, 4-donor substrate, 5-acceptor substrate, 6-element, 7-groove. DETAILED DESCRIPTION

[0034] The content of the present application will be further illustrated below in combination with the drawings and embodiments.

[0035] As an example, but not limiting the scope of the present application, Figure 1The structural schematic diagram of the minimum unit of the magnetic control liquid metal burr transfer printing stamp of the present application. The base 1 is an acrylic sheet, which is provided with a groove 7, and the stamp body 2 is arranged in the groove 7; the material of the stamp body 2 is selected from a magnetic mixed fluid of 10 μm iron powder and EGaIn liquid metal, and the mass ratio of the iron powder to the liquid metal is 1:4; the stamp body 2 is in the burr structure formed spontaneously under the action of magnetic field disturbance, and the gallium-based oxide film is formed on the surface after being placed in the air for 2-3 days, so that the burr structure can be maintained.

[0036] As an example, but not limiting the scope of the present application, Figure 2 The magnetic field response schematic diagram of the magnetic control liquid metal burr transfer printing stamp of the present application. Figure 2 a is the magnetic control liquid metal burr transfer printing stamp without magnetic field action, and the burr shape of the stamp body 2-1 is round and soft without magnetic field action; Figure 2 b is the magnetic control liquid metal burr transfer printing stamp under the action of magnetic field, and the burr shape of the stamp body 2-2 is sharp and hard under the action of magnetic field.

[0037] As an example, but not limiting the scope of the present application, Figure 3 The transfer principle diagram of the magnetic control liquid metal burr transfer printing stamp of the present application. Figure 3 a-c: picking up the element under no external magnetic field action. Figure 3 d-f: printing the element under the action of external magnetic field 3.

[0038] Under no magnetic field action, the stamp is slowly approached to the element 6 on the donor substrate 4 Figure 3 a) to contact the element 6 Figure 3 b), the element 6 is picked up by the surface tension of the liquid metal Figure 3 c); then transferred to above the receptor substrate 5, a vertical downward magnetic field is applied Figure 3 d), the stamp is instantaneously deformed to reduce adhesion and at the same time generate an ejection force to make the element 6 fall off Figure 3 e), the element 6 is successfully printed on the receptor substrate 5 Figure 3 f), and non-contact printing is realized.

[0039] As an example, but not limiting the scope of the present application, Figure 4 The structural schematic diagram of the array type magnetic control liquid metal burr transfer printing stamp of the present application. The base 1 is provided with array type grooves 7; the stamp body 2 in the burr shape is arranged in the grooves 7, and 2-1 is the stamp body under no magnetic field action, and 2-2 is the stamp body under the action of magnetic field.

[0040] As an example, but not limiting the scope of the present application, Figure 5is the flow chart of the arrayed magnetic control liquid metal burs transfer printing stamp applying global magnetic field to realize large-scale and high-efficiency transfer printing proposed by the application. The pickup process Figure 5 a-c) in Figure 3 a-c) is the same, that is, in the case of no magnetic field, the stamp contacts the element 6, and the element 6 is picked up by the surface tension and oxide layer of the liquid metal. Only the pickup process can pick up the element 6 in batches; the printing process (5d-f in the figure) is the same as d-f in Figure 3 , only that the printing process applies a large range of global magnetic field 3-1 to print the element 6 in large scale and improve the transfer printing efficiency.

[0041] As an example, but not limited to the scope of the application, Figure 6 is the flow chart of the arrayed magnetic control liquid metal burs transfer printing stamp applying selective magnetic field to realize programmable printing proposed by the application. The pickup process Figure 6 a-c) is the same as Figure 5 a-c); the printing process Figure 6 d-f) is to transfer the stamp with the picked-up element 6 to above the host substrate 5 (d in Figure 6 , a local magnetic field 3-2 is applied to the area to be printed, the stamp at the printing site is instantaneously deformed to reduce the adhesion and at the same time generate an ejection force to make the element 6 fall off (e in Figure 6 , the element 6 is successfully printed on the host substrate 5 (f in Figure 6 , realizing the non-contact printing of the element.

Claims

1. A magnetically controlled liquid metal splatter transfer stamp, characterized in that, The seal is composed of a base and a burr-shaped seal body; the base is provided with a groove, and the groove is provided with the burr-shaped seal body; The burr-shaped seal body is a liquid metal fused with magnetic particles, and a layer of oxide is wrapped on the surface to maintain the burr-shaped shape; the liquid metal is one or more of gallium, indium or their alloys; the magnetic particles are one or more of iron, cobalt or nickel.

2. The magnetically controlled liquid metal bump transfer stamp of claim 1, wherein, The base material is a non-magnetic and non-deformable transparent material.

3. The magnetically controlled liquid metal bump transfer stamp of claim 1, wherein, In the burr-shaped seal body, the liquid metal is a gallium-indium alloy EGaIn with a mass ratio of gallium to indium of 3:1, and is in a liquid state at room temperature; the magnetic particles are iron with a size of 1-10 microns; the mass ratio of the magnetic particles to the liquid metal is (0.05-0.25):

1.

4. The magnetically controlled liquid metal bump transfer stamp of claim 1, wherein, The preparation method of the burr-shaped seal body is as follows: the liquid metal and the magnetic particles are mixed in proportion, the magnetic particles are fully contacted with the oxide layer on the surface of the liquid metal, hydrochloric acid with a concentration of 4 mol / L-8 mol / L is added, and the mixture is fully stirred in a magnetic stirrer with a preset temperature of 40-60°C until the solution is clear; the mixture of the magnetic metal particles and the liquid metal is taken out and washed with deionized water, dried, and then placed in the groove of the base, and then disturbed by the magnetic field of a permanent magnet, and the burr-shaped formation is observed, and then placed above the permanent magnet for 1-3 days to form a dense oxide film, thereby obtaining the burr-shaped seal body.

5. The magnetically controlled liquid metal bump transfer stamp of claim 4, wherein, The permanent magnet is cubic or cylindrical.

6. The magnetically controlled liquid metal bump transfer stamp of claim 4, wherein, The liquid metal is EGaIn, the magnetic particles are iron powder, and the mass ratio of EGaIn to iron powder is 4:

1.

7. A magnetron non-contact printing method characterized by, Based on the seal as claimed in any one of claims 1-6, the steps are as follows: When picking up, no magnetic field is applied, and the burr of the seal is soft and easy to bend and deform; the seal is brought into contact with the element, and the element is picked up from the donor substrate by using the strong surface tension of the liquid metal; When printing, an external magnetic field is applied, the burr becomes sharp, the rigidity increases, the instantaneous deformation of the seal decreases the interfacial adhesion and generates an ejection force, thereby releasing the element.

8. The magnetically controlled non-contact printing method of claim 7, wherein, When the external driving is a global magnetic field, the seal is driven to realize large-scale and efficient transfer printing; when the external driving is a local magnetic field, the seal is driven to realize programmable patterned transfer printing.

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