Flexible electronic curved conformal non-destructive transfer method based on micro-needle dot matrix structure stamp

Abstract

The present application belongs to the field of micro-nano processing and flexible electronic technology, and provides a flexible electronic curved surface conformal non-destructive transfer method based on a microneedle lattice structure stamp. The free sliding or controllable sequential bending deformation of the microneedle lattice structure is used to realize the conformal attachment of the flexible electronic device and the application substrate surface morphology. The gradual and step-by-step lifting or controllable sequential deformation recovery of the microneedle lattice structure is used to realize the interface viscosity regulation between the flexible electronic device and the application substrate. The conformal attachment and low-stress non-destructive transfer of the flexible electronic device on the application substrate with complex curved surface morphology are realized. The present method is compatible with industrial mass production, does not need to know the curved surface substrate morphology in advance, has simple process, strong controllability, low application threshold and good universality, and can complete the integration of large batch and large area flexible electronic devices on complex curved application substrates with high precision and high efficiency.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano processing and flexible electronics technology, specifically relating to a non-destructive transfer method for flexible electronic curved surfaces based on a microneedle lattice structure stamp. Background Technology

[0002] Flexible electronics technology refers to the integration of organic / inorganic electronic devices onto flexible substrates, enabling them to withstand large deformations such as stretching, bending, and torsion, and conform to complex working surfaces. It has wide applications in energy, information, and medical fields. Transfer printing is the mainstream fabrication technology for flexible electronics, mainly consisting of two processes: transfer and printing. In the transfer stage, a stamp is used to lift the flexible electronic device from the substrate, requiring strong adhesion between the stamp and the flexible electronic device. In the printing stage, the stamp carrying the electronic device is aligned and brought into contact with the substrate, allowing the flexible electronic device to detach from the stamp and be printed onto the substrate, requiring weak adhesion between the stamp and the flexible electronic device. Therefore, successful transfer printing often requires reasonable and on-demand control of the adhesion between the stamp and the flexible electronic device. Furthermore, with the continuous expansion of application demands and the deepening of research, how to transfer and integrate easily damaged and wrinkled flexible electronic devices onto substrates with curved surfaces in a low-stress and non-destructive manner has become a key challenge and a crucial issue.

[0003] Patent document CN110752145B discloses a wet transfer integration method based on liquid capillary force and surface tension. A liquid bridge is formed between a transfer stamp and a flexible electronic device. The capillary force of the liquid bridge lifts the electronic device, and the volume of the liquid bridge is adjusted to detach the electronic device from the transfer stamp. Patent document CN115818563B discloses a universal flexible electronic transfer method based on a bubble / film. This method uses the capillary force of a bubble / film to lift the electronic device and utilizes the controllable rupture characteristics of the bubble / film to achieve contactless integration transfer. It eliminates the need for interface viscosity control and is suitable for non-destructive, wrinkle-free curved surface integration of both thicker (sub-millimeter and micrometer scale) and thinner (sub-micrometer and nanometer scale) flexible electronic devices. This liquid-medium-based wet transfer process often requires consideration of device alignment, liquid inertial sloshing, and subsequent evaporation, resulting in a long processing time and making it difficult to apply to industrial, high-volume, and rapid production.

[0004] Patent document CN106671584A discloses a conformal transfer method for flexible electronic devices applicable to substrates with curved surfaces. It proposes a stamp design that integrates multiple pins in the transfer head, effectively solving the problems of poor deformation ability of elastic stamps and inability to adapt to curved surfaces in traditional dry contact transfer. After knowing the shape of the curved surface, the required displacement of each pin is determined and the up-and-down movement of multiple pins is driven by a passive deformation module. An auxiliary deformation module outputs the curved surface shape corresponding to the target substrate, and an electromagnetic braking module fixes the shape of the pins, so that the transferred electronic film conforms to the target curved surface. Then, the electromagnetic braking module is de-energized, and the pins return to their initial flat state, completing the transfer process. Patent document CN106671584A can solve the problem of flexible films not being able to adhere to the target curved surface with high efficiency and high precision, and is compatible with industrial mass production. However, the overall process requires dynamic identification of the surface substrate morphology, which enhances the process steps. At the same time, if the morphology identification and auxiliary deformation modules have errors, this forced displacement movement will lead to local stress concentration and damage to electronic devices.

[0005] Currently, the key issue in addressing the growing demand for high-quality flexible electronics is how to achieve conformal, low-stress, and non-destructive transfer integration of flexible electronic devices on application substrates with curved surfaces, in order to meet the needs of large-scale, high-efficiency industrial production, lower technical barriers, and simplify processes. Summary of the Invention

[0006] This invention addresses the aforementioned problems by proposing a conformal, non-destructive transfer method for flexible electronic surfaces based on a microneedle lattice structure stamp. This method achieves efficient control over the contact area and interfacial adhesion between the microneedle lattice structure and the flexible electronic device by adjusting the vertical position or bending deformation state of the microneedle lattice structure. This allows for convenient, low-stress, and non-destructive transfer of flexible electronic devices from the fabrication substrate to an application substrate with a curved surface. During the transfer process, the flexible electronic device is only subjected to the self-weight of the microneedle lattice structure or the reaction force caused by the bending deformation of the low-stiffness microneedle lattice structure, ensuring a low stress level and effectively stabilizing the electrical performance of the flexible electronic device. This transfer method based on the microneedle lattice structure stamp is highly compatible with industrial fabrication, enabling high-precision and high-efficiency transfer and integration of large batches of large-format flexible electronic devices onto application substrates with complex curved surfaces. The overall process is simple, requiring no prior knowledge of the substrate surface morphology or precise displacement control of the microneedle lattice structure. It is highly maneuverable, has a low application threshold, and good process versatility, making it suitable for a wide range of electronic materials and substrate morphologies.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A non-destructive, conformal electronic surface transfer method based on a microneedle lattice structure stamp includes the following steps: Step (1): Prepare a microneedle lattice structure stamp comprising a transfer frame 4 and a microneedle lattice structure 3. The microneedle lattice structure 3 is integrated into the hollow channel of the transfer frame 4. The diameter of the individual microneedles in the microneedle lattice structure 3 is slightly smaller than the diameter of the hollow channel in the transfer frame 4. This allows the microneedle lattice structure 3 to slide freely up and down in the hollow channel of the transfer frame 4 without tilting left and right, which would affect the positioning accuracy. In addition, the tip size of the individual microneedles in the microneedle lattice structure 3 should be larger than the diameter of the hollow channel in the transfer frame 4 to effectively prevent the microneedle lattice structure 3 from falling off freely in the hollow channel of the transfer frame 4 and causing transfer failure. Alternatively, the microneedle lattice structure 3 containing microneedles with different lengths and stiffness distributions can be fixed to one side of the transfer frame 4. The stiffness of the individual microneedles in the microneedle lattice structure 3 is inversely proportional to its length, that is, the longer the individual microneedle, the smaller the stiffness. The stiffness of the individual microneedle can be controlled by changing the diameter or cross-sectional shape of the microneedle and by changing the material properties.

[0008] Step (2): Lifting the flexible electronic device 2 from the substrate 1: Move the microneedle lattice structure stamp containing the central hole channel to align it with the flexible electronic device 2 on the substrate 1 with a planar morphology. Under its own weight, the microneedle lattice structure 3 slides freely down the hollow channel in the transfer frame 4 and makes full contact with the flexible electronic device 2, effectively enhancing the contact area and interfacial adhesion between the microneedle lattice structure 3 and the flexible electronic device 2. Lift the transfer frame 4 upward to cause the microneedle lattice structure 3 and the flexible electronic device 2 to peel off from the substrate 1, realizing the lifting and transfer of the flexible electronic device 2 on the substrate 1; or move the microneedle lattice structure 3 and the transfer frame 4 to separate them. The microneedle lattice structure stamp aligns with and contacts the flexible electronic device 2 on the substrate 1 with a planar topography. As the microneedle lattice structure stamp continues to move downward, the longer, low-stiffness microneedles in the microneedle lattice structure 3 bend and deform, allowing the sub-equal length microneedles to contact the flexible electronic device 2 as much as possible. This effectively enhances the contact area and interfacial adhesion between the microneedle lattice structure 3 and the flexible electronic device 2. The transfer frame 4 is then quickly lifted upward, causing the microneedle lattice structure 3 and the flexible electronic device 2 to peel off from the substrate 1. At this point, the longer, low-stiffness microneedles remain bent and deformed to ensure sufficient interfacial adhesion to lift and transfer the flexible electronic device 2 onto the substrate 1.

[0009] Step (3): Printing and integrating the flexible electronic device 2 onto the application substrate 5 with a curved surface: Move the microneedle lattice structure stamp containing the central hole channel, align and contact the flexible electronic device 2 with the application substrate 5 with a curved surface, and under its own weight, the microneedle lattice structure 3 slides freely downward in the hollow channel of the transfer frame 4, driving the flexible electronic device 2 to conformally fit with the curved surface of the application substrate 5. Then, lift some of the microneedles in the microneedle lattice structure 3 step by step to dynamically reduce the interfacial adhesion between the microneedle lattice structure 3 and the flexible electronic device 2 until all the microneedles of the microneedle lattice structure 3 are detached from the flexible electronic device 2, realizing the transfer and integration of the flexible electronic device 2 onto the application substrate 5 with a curved surface; or move the microneedle lattice structure stamp that fixes the microneedle lattice structure 3 and the transfer frame 4, and align and contact the flexible electronic device 2 with the application substrate 5 with a curved surface. After the flexible electronic device 2 is aligned and in contact with the application substrate 5 with a curved surface, the microneedle lattice structure 3, after detaching from the preparation substrate 1, returns from a bent state to its initial vertical state or a slightly bent state. As the microneedle lattice structure stamp continues to move downward, the longer, low-stiffness microneedles in the microneedle lattice structure 3 undergo bending deformation, driving the flexible electronic device 2 to conformally fit with the application substrate 5 with a curved surface. Then, the microneedle lattice structure stamp is lifted vertically, and the low-stiffness deformed microneedles of different lengths in the microneedle lattice structure 3 sequentially return to a vertical state or a slightly bent state, dynamically reducing the interfacial adhesion between the microneedle lattice structure 3 and the flexible electronic device 2 until all the microneedles of the microneedle lattice structure 3 detach from the flexible electronic device 2, thus achieving the transfer integration of the flexible electronic device 2 on the application substrate 5 with a curved surface.

[0010] A further feature is that the microneedle lattice structure 3 in the microneedle lattice structure stamp can control the interfacial adhesion between the microneedle lattice structure 3 and the flexible electronic device 2 through methods such as surface modification, such as dipping the bottom of the microneedle into a viscous liquid (PDMS, Ecoflex, etc.) and heating to cure it, or adding an adhesive layer, etc.

[0011] A further feature is that the microneedle matrix structure 3 in the microneedle matrix structure stamp can be composed of some microneedles with adhesive bottom ends and some microneedles without adhesive bottom ends. Preferably, the microneedles without adhesive bottom ends are distributed on the outside of the microneedles with adhesive bottom ends.

[0012] A further feature is that the stiffness of the microneedle lattice structure 3 in the microneedle lattice structure seal can be controlled by adjusting the microneedle diameter or by selecting a target stiffness material. The microneedle diameter can be adjusted by using an equal diameter method or by using a non-equal diameter structure.

[0013] A further feature is that the distribution of microneedles of different lengths in the microneedle lattice structure 3 fixed in the transfer frame 4 on the surface of the transfer frame 4 can be uniform, random, or concentric.

[0014] A further feature is that the spacing between the microneedles in the microneedle matrix structure 3 of the microneedle matrix structure stamp can be reasonably adjusted, effectively reducing the stress level of the flexible electronic device 2.

[0015] A further feature is that the method for completing the transfer is to lift some of the microneedles in the microneedle lattice structure 3 one by one. An irregular curved surface limiting plate can be arranged on the upper end of the microneedle lattice structure 3. When a force such as a magnetic field is applied uniformly, the microneedle lattice structure 3 can be moved in different directions in the vertical direction through the irregular curved surface limiting plate, thereby dynamically controlling the interfacial adhesion between the microneedle lattice structure 3 and the flexible electronic device 2.

[0016] A further feature is that the flexible electronic device 2 to which the transfer process is applicable can be a relatively thick (submillimeter and micrometer scale) electronic device or a relatively thin (submicrometer and nanometer scale) electronic device, and the surface morphology of the application substrate 5 to which the transfer is applicable can be planar or curved.

[0017] A further feature is that the microneedle lattice structure 3 can be extended to macroscopic dimensions without limitation, and can be applied to the transfer integration of flexible electronic devices 2 at the meter level and above.

[0018] A further feature is that the microneedles in the microneedle lattice structure 3, which slides freely in the hollow channel of the transfer frame, are preferably of equal length.

[0019] The beneficial effects of this invention are: This invention enables non-destructive, low-stress, conformal transfer integration of flexible electronics of varying thicknesses, sizes, and formats onto curved substrates. It utilizes the free sliding or controllable sequential deformation of microneedle lattice structures to achieve conformal bonding between the flexible electronic devices and the curved surface of the application substrate. The interfacial adhesion between the flexible electronic devices and the application substrate is dynamically controlled by the gradual lifting or controllable sequential restoration of the microneedle lattice structure to a vertical or slightly bent state. During the transfer process, the flexible electronic devices are only subjected to the self-weight of the microneedles or the bending deformation reaction force of the long, low-stiffness microneedles, resulting in low stress levels suitable for non-destructive integration of flexible electronic devices. The overall process is simple and versatile, applicable to numerous flexible electronic devices and application substrates with different curved surface morphologies. It eliminates the need for prior knowledge of the application substrate morphology and the need for inversion to determine and precisely control the displacement or deformation of the microneedle lattice structure, making it suitable for industrial manufacturing applications and facilitating the efficient and rapid production of large-scale, large-format flexible electronics. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a microneedle dot matrix structure stamp, which consists of a transfer frame 4 containing a hollow channel and a freely sliding microneedle dot matrix structure 3. Figure 2This is a schematic diagram of a microneedle lattice structure stamp in which microneedle lattice structures 3 of different lengths and stiffnesses are solidified and integrated on one side of the transfer frame 4. Figure 3 This diagram illustrates how the flexible electronic device 2 is lifted from the substrate 1 by utilizing the free sliding property of the microneedle lattice structure 3 within the hollow channel of the transfer frame 4. Once the microneedle lattice structure 3 aligns and contacts the flexible electronic device 2 on the substrate 1, the transfer frame 4 is lifted upwards. Under its own weight, the microneedle lattice structure 3 slides freely downwards within the hollow channel of the transfer frame 4 until the limiting effect caused by the microneedle tip diameter being larger than the hollow channel diameter lifts the microneedle lattice structure 3 and the transfer frame 4 together. At this point, the microneedle lattice structure 3 and the flexible electronic device 2 are in full contact, providing a sufficiently large interfacial adhesion force. Lifting the transfer frame 4 upwards can then lift the flexible electronic device 2 from the substrate 1. In industrial-scale mass production, the position of the microneedle lattice structure 3 can be controlled and fixed in real time using an electromagnetic module or a mechanical control module, eliminating the need to activate the limiting effect and achieving rapid and efficient fabrication. Figure 4 This is a schematic diagram showing how the transfer frame 4 drives the microneedle lattice structure 3 and the flexible electronic device 2 to align with the application substrate 5, which has a curved surface. Figure 5 This is a schematic diagram of the flexible electronic device 2 conformally bonding with the application substrate 5 with a curved surface by utilizing the free sliding characteristics of the microneedle lattice structure 3. After the flexible electronic device 2 comes into contact with the application substrate 5 with a curved surface, the transfer frame 4 continues to move downward. Some microneedles in the microneedle lattice structure 3 stop moving downward after contacting the application substrate 5, while some microneedles move downward with the transfer frame 4 under their own weight, driving the flexible electronic device 2 to conformally bond with the curved surface of the application substrate 5. Figure 6 This diagram illustrates how the microneedle lattice structure 3 is lifted step-by-step to reduce contact area and interfacial adhesion. Different microneedles within the microneedle lattice structure 3 are lifted upwards in stages, dynamically reducing the contact area and interfacial adhesion between the microneedle lattice structure 3 and the flexible electronic device 2. The position of the different microneedles in the microneedle lattice structure 3 can be controlled through a multi-channel method with precise control of each microneedle; alternatively, the microneedle lattice structure 3 can be driven upwards by an external magnetic field, with an irregular curved surface limiting structure above it. This achieves a non-uniform distribution of the microneedle lattice structure 3 in the vertical direction under a single control channel, effectively reducing the contact area and interfacial adhesion between the microneedle lattice structure 3 and the flexible electronic device 2.

[0021] Figure 7This is a schematic diagram showing the microneedle lattice structure 3 and the transfer frame 4 being fully lifted and detached from the application substrate 5. At this time, the transfer frame 4 has been fully lifted, so that the top diameter limiting effect of the microneedle lattice structure 3 is effective, and the different microneedles of the microneedle lattice structure 3 are in a highly aligned state, which is convenient for the next transfer.

[0022] Figure 8 This is a schematic diagram of a flexible electronic device 2 being transferred and integrated onto an application substrate 5 with a curved surface. Figure 9 This is a schematic diagram showing the alignment and contact between a microneedle lattice structure stamp, in which microneedle lattice structures 3 of different lengths and stiffnesses are solidified and integrated on a transfer frame 4, and a flexible electronic device 2 on a substrate 1. Figure 10 This is a schematic diagram of using a microneedle lattice structure stamp containing microneedles of different lengths and stiffnesses to lift the flexible electronic device 2 from the preparation substrate 1. After the microneedle lattice structure 3 comes into contact with the flexible electronic device 2, a displacement load is applied downwards, causing the longer, low-stiffness microneedles in the microneedle lattice structure 3 to bend and deform first, driving more microneedles of different lengths to come into contact with the flexible electronic device 2, increasing the contact area and interfacial adhesion between the microneedle lattice structure 3 and the flexible electronic device 2. At this time, the transfer frame 4 is lifted upwards, causing the microneedle lattice structure 3 and the flexible electronic device 2 to be lifted from the preparation substrate 1. Figure 11 This is a schematic diagram of aligning the curved surface of the flexible electronic device 2 with the application substrate 5 using a microneedle lattice structure stamp containing microneedles of different lengths and stiffnesses. At this time, there is only contact between the microneedle lattice structure 3 and the flexible electronic device 2, so that the microneedles of different lengths and stiffnesses in the microneedle lattice structure 3 return to their initial vertical state or have a small bending deformation state.

[0023] Figure 12 This is a schematic diagram of using a microneedle lattice structure stamp containing microneedles of different lengths and stiffness distributions to fit the flexible electronic device 2 to the curved surface of the application substrate 5. At this time, pressure is applied downward to the transfer frame 4, causing the longer low-stiffness microneedles and the secondary short-stiffness microneedles to bend and deform in sequence, driving the flexible electronic device 2 to conformally fit the curved surface of the application substrate 5.

[0024] Figure 13 This is a schematic diagram of adjusting the contact area between the microneedle lattice structure 3 and the flexible electronic device 2 by lifting the microneedle lattice structure stamp upwards. At this time, the transfer frame 4 moves upwards, so that the microneedles with different lengths and stiffnesses in the microneedle lattice structure 3 are restored to their initial vertical state or slightly bent state in sequence. This dynamically reduces the contact area and interfacial adhesion between the microneedle lattice structure 3 and the flexible electronic device 2, which is conducive to the detachment of the flexible electronic device 2 from the microneedle lattice structure 3. Figure 14 This is a schematic diagram of printing and integrating flexible electronic devices 2 onto an application substrate 5 with a curved surface by utilizing the dynamic sequential bending deformation mechanism of microneedles with different lengths and stiffnesses in the microneedle lattice structure 3.

[0025] In the figure: 1. Fabrication substrate, 2. Flexible electronic device, 3. Microneedle lattice structure, 4. Transfer frame, 5. Application substrate. Detailed Implementation

[0026] The embodiments of the present invention are further described below in conjunction with the technical solutions and accompanying drawings.

[0027] Example 1: A flexible electronic surface conformal non-destructive transfer method based on microneedle lattice structure stamp (microneedle lattice structure free sliding mechanism) Step (1), prepare as follows Figure 1 The microneedle lattice structure stamp shown: The microneedle lattice structure 3 is integrated into the hollow channel in the transfer frame 4. The diameter of the individual microneedles in the microneedle lattice structure 3 should be slightly smaller than the diameter of the hollow channel in the transfer frame 4. This allows the microneedle lattice structure 3 to slide freely up and down in the hollow channel in the transfer frame 4 without tilting left and right, which would affect the positioning accuracy. The top size of the individual microneedles in the microneedle lattice structure 3 should be larger than the diameter of the hollow channel in the transfer frame 4. This can effectively prevent the microneedle lattice structure 3 from falling off freely in the hollow channel in the transfer frame 4 and causing transfer failure. The bottom of the microneedles in the microneedle lattice structure 3 can be dipped into a viscous liquid (such as PDMS, Ecoflex, etc.) and cured or have an adhesive layer added to control the interfacial adhesion of the microneedle lattice structure 3.

[0028] Step (2), as Figure 3 As shown, the microneedle lattice structure stamp containing the central hole channel is moved and aligned with the flexible electronic device 2 on the substrate 1 with a planar morphology. Under its own weight, the microneedle lattice structure 3 slides freely down the hollow channel in the transfer frame 4 and makes full contact with the flexible electronic device 2, effectively enhancing the contact area and interfacial adhesion between the microneedle lattice structure 3 and the flexible electronic device 2. The transfer frame 4 is lifted upward to cause the microneedle lattice structure 3 and the flexible electronic device 2 to peel off from the substrate 1, realizing the detachment and transfer of the flexible electronic device 2 from the substrate 1.

[0029] Step (3), as Figure 4 - Figure 8 As shown, the microneedle lattice structure stamp containing a central hole channel is moved to align and bring the flexible electronic device 2 it carries into contact with the application substrate 5, which has a curved surface (e.g., Figure 4 As shown), under its own weight, the microneedle lattice structure 3 slides freely downward in the hollow channel of the transfer frame 4, driving the flexible electronic device 2 to conformally fit the curved surface morphology of the application substrate 5 (as shown). Figure 5 As shown), then sequentially lift some of the microneedles in the microneedle lattice structure 3 (such as...). Figure 6 As shown), dynamically reduce the interfacial adhesion between the microneedle lattice structure 3 and the flexible electronic device 2 until all microneedles of the microneedle lattice structure 3 detach from the flexible electronic device 2 (e.g., ...). Figure 7 As shown), the flexible electronic device 2 is transferred and integrated onto the application substrate 5 with a curved surface (e.g., Figure 8 (As shown).

[0030] Example 2: A flexible electronic surface conformal non-destructive transfer method based on microneedle lattice structure stamp (based on the dynamic sequential bending deformation mechanism of microneedles with different lengths and stiffness distributions) Step (1), prepare as follows Figure 2 The microneedle lattice structure stamp shown integrates a microneedle lattice structure 3 containing microneedles with different lengths and stiffness distributions on one side of the transfer frame 4 (e.g., Figure 9 As shown, the stiffness of a single microneedle is inversely proportional to its length; that is, the longer the microneedle, the lower its stiffness and the easier it is to bend and deform. Interfacial viscosity can be controlled based on the dynamic sequential bending deformation of microneedles of different lengths. The stiffness of a single microneedle can be controlled by setting its diameter, cross-sectional morphology, or selecting different materials. The distribution of microneedles of different lengths on the surface of the transfer frame 4 can be random, uniform, or concentric. The bottom end of the microneedle lattice structure 3 can be surface modified to improve viscosity, such as by dipping into viscous liquids (e.g., PDMS, Ecoflex) and curing them, or by adding an adhesive layer.

[0031] Step (2), as Figure 9 - Figure 10 As shown, the microneedle lattice structure 3 and the microneedle lattice structure stamp of the transfer frame 4 lift the flexible electronic device 2 from the substrate 1. In the initial state, the heights of the different microneedles in the microneedle lattice structure 3 are inconsistent (e.g., Figure 9 As shown), after aligning and contacting the substrate 1, the microneedle lattice structure stamp continues to move downwards. The longer, low-stiffness microneedles in the microneedle lattice structure 3 bend and deform, allowing the sub-equal-length individual microneedles to contact the flexible electronic device 2 as much as possible (e.g., ...). Figure 10 As shown, this effectively enhances the contact area and interfacial adhesion between the microneedle lattice structure 3 and the flexible electronic device 2. Lifting the transfer frame 4 upwards causes the microneedle lattice structure 3 and the flexible electronic device 2 to peel off from the substrate 1. At this time, the longer, low-stiffness microneedles remain bent and deformed to ensure sufficient interfacial adhesion to lift and transfer the flexible electronic device 2 onto the substrate 1.

[0032] Step (3), as Figure 11 - Figure 14As shown, the movable and solidified microneedle lattice structure 3 and the microneedle lattice structure stamp of the transfer frame 4 print and integrate the flexible electronic device 2 onto the application substrate 5 with a curved surface. In the initial state, after the microneedle lattice structure 3 is detached from the preparation substrate 1, it recovers from a bent state to an initial vertical state or a slightly bent state (e.g., Figure 11 As shown), the microneedle lattice structure stamp continues to move downwards. The longer, low-stiffness microneedles in the microneedle lattice structure 3 bend and deform, driving the flexible electronic device 2 to conformally fit with the application substrate 5, which has a curved surface (as shown). Figure 12 As shown), then the microneedle lattice structure stamp is lifted vertically. The low-stiffness deformable microneedles of different lengths in the microneedle lattice structure 3, under the loss of pressure, sequentially return to a vertical state or a slightly bent state (as shown). Figure 13 As shown), the interfacial adhesion between the microneedle lattice structure 3 and the flexible electronic device 2 is dynamically reduced until all the microneedles of the microneedle lattice structure 3 detach from the flexible electronic device 2, thereby achieving the transfer integration of the flexible electronic device 2 onto the application substrate 5 with a curved surface (as shown). Figure 14 (As shown).

Claims

1. A flexible electronic surface conformal non-destructive transfer method based on a microneedle lattice structure stamp, characterized in that, Includes the following steps: Step (1): Prepare a microneedle lattice structure stamp comprising a transfer frame (4) and a microneedle lattice structure (3): The microneedle lattice structure (3) is integrated into the hollow channel of the transfer frame (4). The diameter of the needle body of a single microneedle in the microneedle lattice structure (3) is smaller than the diameter of the hollow channel in the transfer frame (4), and the top dimension of a single microneedle in the microneedle lattice structure (3) is larger than the diameter of the hollow channel in the transfer frame (4). Alternatively, the microneedle lattice structure (3) containing microneedles with different lengths and stiffness distributions is fixed on one side of the transfer frame (4). The stiffness of a single microneedle in the microneedle lattice structure (3) is inversely proportional to its length, that is, the longer the single microneedle, the smaller its stiffness. The stiffness of a single microneedle is controlled by changing the needle body diameter or cross-sectional morphology of the microneedle and by changing the material properties. Step (2), lifting the flexible electronic device (2) from the substrate (1): Move the microneedle lattice structure stamp with a central hole channel to align with the flexible electronic device (2) on the substrate (1) with a planar morphology. Under its own weight, the microneedle lattice structure (3) slides freely down the hollow channel in the transfer frame (4) and makes full contact with the flexible electronic device (2), effectively enhancing the contact area and interfacial adhesion between the microneedle lattice structure (3) and the flexible electronic device (2). Lifting the transfer frame (4) upwards causes the microneedle lattice structure (3) and the flexible electronic device (2) to peel off from the substrate (1), realizing the lifting and transfer of the flexible electronic device (2) on the substrate (1); or The microneedle lattice structure stamp of the movable and solidified microneedle lattice structure (3) and the transfer frame (4) is aligned and in contact with the flexible electronic device (2) on the preparation substrate (1) with a planar morphology. The microneedle lattice structure stamp continues to move downward, and the longer low-stiffness microneedles in the microneedle lattice structure (3) bend and deform, so that the secondary length microneedles contact the flexible electronic device (2) as much as possible. The transfer frame (4) is quickly lifted upward to drive the microneedle lattice structure (3) and the flexible electronic device (2) to peel off from the preparation substrate (1). At this time, the longer low-stiffness microneedles still remain bent and deformed to ensure sufficient interfacial adhesion to lift and transfer the flexible electronic device (2) on the preparation substrate (1). Step (3): Printing and integrating the flexible electronic device (2) onto the application substrate (5) with a curved surface: Move the microneedle lattice structure stamp containing the central hole channel to align and contact the flexible electronic device (2) with the application substrate (5) with a curved surface. Under its own weight, the microneedle lattice structure (3) slides freely downward in the hollow channel of the transfer frame (4), driving the flexible electronic device (2) to conformally fit with the curved surface of the application substrate (5). Then, lift some of the microneedles in the microneedle lattice structure (3) step by step to dynamically reduce the interfacial adhesion between the microneedle lattice structure (3) and the flexible electronic device (2) until all the microneedles of the microneedle lattice structure (3) are separated from the flexible electronic device (2), realizing the transfer integration of the flexible electronic device (2) on the application substrate (5) with a curved surface; or move the microneedle lattice structure stamp that is fixed between the microneedle lattice structure (3) and the transfer frame (4). After aligning and contacting the flexible electronic device (2) with the application substrate (5) with a curved surface, the microneedle lattice structure (3) returns from a bent state to an initial vertical state or a slightly bent state after detaching from the preparation substrate (1). The microneedle lattice structure stamp continues to move downward, and the longer low-stiffness microneedles in the microneedle lattice structure (3) bend and deform, driving the flexible electronic device (2) to conformally fit with the application substrate (5) with a curved surface. Then, the microneedle lattice structure stamp is lifted in the vertical direction, and the low-stiffness deformed microneedles of different lengths in the microneedle lattice structure (3) return to a vertical state or a slightly bent state in sequence, dynamically reducing the interfacial adhesion of the contact area between the microneedle lattice structure (3) and the flexible electronic device (2) until all the microneedles of the microneedle lattice structure (3) detach from the flexible electronic device (2), realizing the transfer integration of the flexible electronic device (2) on the application substrate (5) with a curved surface.

2. The flexible electronic surface conformal non-destructive transfer method based on a microneedle dot matrix structure stamp according to claim 1, characterized in that, The microneedle lattice structure (3) in the microneedle lattice structure stamp is controlled by surface modification method to regulate the interfacial adhesion between the microneedle lattice structure (3) and the flexible electronic device (2), including dipping the bottom of the microneedle into a viscous liquid and heating and curing it, or adding an adhesive layer.

3. A flexible electronic surface conformal non-destructive transfer method based on a microneedle lattice structure stamp according to claim 1 or 2, characterized in that, The microneedle dot matrix structure (3) in the microneedle dot matrix structure stamp is composed of microneedles with adhesive bottom ends and microneedles without adhesive bottom ends.

4. A flexible electronic surface conformal non-destructive transfer method based on a microneedle lattice structure stamp according to claim 1 or 2, characterized in that, The stiffness of the microneedle lattice structure (3) in the microneedle lattice structure seal is controlled by adjusting the microneedle diameter or selecting a target stiffness material. The microneedle diameter is adjusted by using an equal diameter method or a non-equal diameter structure.

5. A flexible electronic surface conformal non-destructive transfer method based on a microneedle dot matrix structure stamp according to claim 1 or 2, characterized in that, The distribution of microneedles of different lengths in the microneedle lattice structure (3) solidified in the transfer frame (4) on the surface of the transfer frame (4) is uniform, random or concentric.

6. A flexible electronic surface conformal non-destructive transfer method based on a microneedle dot matrix structure stamp according to claim 1 or 2, characterized in that, The spacing between microneedles in the microneedle matrix structure (3) of the microneedle matrix structure stamp can be adjusted.

7. A flexible electronic surface conformal non-destructive transfer method based on a microneedle lattice structure stamp according to claim 1 or 2, characterized in that, The method for completing the transfer is to lift some of the microneedles in the microneedle lattice structure (3) step by step, arrange an irregular curved surface limiting plate on the upper end of the microneedle lattice structure (3), and realize different displacements of the microneedle lattice structure (3) in the vertical direction through the irregular curved surface limiting plate when a uniform force is applied, so as to dynamically control the interfacial adhesion between the microneedle lattice structure (3) and the flexible electronic device (2).

8. A flexible electronic surface conformal non-destructive transfer method based on a microneedle dot matrix structure stamp according to claim 1 or 2, characterized in that, The flexible electronic devices (2) to which the transfer process is applicable are sub-millimeter, micrometer, sub-micrometer or nanometer scale electronic devices, and the surface morphology of the application substrate (5) to which the transfer is applicable is planar or curved.

9. A flexible electronic surface conformal non-destructive transfer method based on a microneedle dot matrix structure stamp according to claim 1 or 2, characterized in that, The microneedle lattice structure (3) can be extended to macroscopic size without limitation and applied to the transfer integration of flexible electronic devices (2) at the meter level and above.

10. A flexible electronic surface conformal non-destructive transfer method based on a microneedle dot matrix structure stamp according to claim 1 or 2, characterized in that, The microneedles in the microneedle lattice structure (3) that slides freely in the hollow channel of the transfer frame are of equal length.

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