An elastic stamp imitating the stomata structure of plant leaves and its preparation method and application

Abstract

The invention discloses an elastic stamp imitating the stomata structure of plant leaves and a preparation method and application thereof, belonging to the technical field of transfer printing. The structure of the elastic stamp is composed of a substrate and a polymer film layer located on the upper surface of the substrate, the polymer film layer has stomata with hemispherical micro cavities, and the transfer of the device is achieved by controlling the air pressure in the stomata; the transfer method of the device is as follows: when picking up the device, the elastic stamp is attached to the device surface, the air in the stomata of the elastic stamp is heated, the air in the hemispherical micro cavities of the stomata is discharged, the air pressure drops accordingly and forms a negative pressure with the atmospheric pressure, the elastic stamp / device interface is in an adhered state, and the device is picked up; when releasing the device, the air in the stomata of the elastic stamp is heated, the air pressure in the hemispherical micro cavities of the stomata is increased and is greater than the atmospheric pressure to form a positive pressure, the elastic stamp / device interface is in a debonding state, and the device is released.

Description

Technical Field

[0001] The invention relates to an elastic stamp imitating the stomatal structure of plant leaves and a preparation method and application thereof, belonging to the technical field of transfer printing. Background Art

[0002] Transfer printing technology is a technology that integrates micro-nano materials into spatially ordered two-dimensional or three-dimensional functional modules. It has been widely used in the preparation of some heterogeneous and inhomogeneous high-performance integrated functional systems, such as flexible optical / electronic devices, three-dimensional or curved optical / electronic devices, and biocompatibility detection and measurement equipment.

[0003] Transfer printing is generally achieved using an elastic stamp, which relies on the strong adhesion between the elastic stamp and the device on the donor substrate to pick up the device from the donor substrate; when the device needs to be transferred to the acceptor substrate, the adhesion between the stamp and the device is weakened, and the device is released to the acceptor substrate. The key to transfer printing lies in the regulation of the adhesion performance between the stamp and the device.

[0004] Thermally driven pore transfer technology is an important device transfer method for elastic stamps. This technology heats the stamp / device interface through pulsed lasers, uses the interface heat to drive the device to debond, and can achieve selective device transfer by controlling the laser heating area. Using heat to cause the pressure in the pores of the elastic stamp to change in order to regulate the adhesion of the stamp / device interface and thus achieve device pickup and release is an important way to apply this technology. However, the pore microcavities of existing elastic stamps ([1] Luo, H.; Wang, S.; Wang, C.; Linghu, C.; Song, J., Thermal Controlled Tunable Adhesive for Deterministic Assembly by Transfer Printing. Advanced Functional Materials 2021, 31(16)) are cylindrical, which is prone to deformation, skewness, and even uneven shrinkage. In addition, its preparation involves processes such as substrate etching and stamp demolding. The preparation process is cumbersome and the stamp demolding process also faces the potential problem of stamp structure damage, which is not conducive to large-scale promotion and application. Summary of the invention

[0005] In order to solve the problems in the prior art, the present invention provides an elastic stamp imitating the stomatal structure of plant leaves, and a preparation method and application thereof; the elastic stamp is provided with a polymer layer having pores with hemispherical micro-cavities, and the adhesion between the elastic stamp and the device interface is adjusted by heat to achieve the pickup and release of the device; the elastic stamp has a high application range and a wide adjustable viscosity range, and a high device transfer efficiency, and can effectively solve the problems of pressure application when the elastic stamp picks up the device and the difficulty in releasing the device to a low-viscosity acceptor substrate; the preparation process of the elastic stamp is simple and quick, and has very important practical value and innovative significance.

[0006] The technical solution of the present invention is as follows:

[0007] One of the purposes of the present invention is to provide an elastic stamp imitating the stomata structure of plant leaves, wherein the elastic stamp is a double-layer structure, comprising a substrate and a polymer film layer located on the upper surface of the substrate;

[0008] Furthermore, the surface of the polymer film layer is provided with a plurality of pores, the interior of the pores is a hemispherical micro cavity, and is connected to the substrate located below the polymer film layer;

[0009] Furthermore, the polymer film layer is a highly transparent elastic material; and the substrate is a quartz glass substrate or a sapphire substrate.

[0010] Furthermore, the polymer film layer is specifically polydimethylsiloxane.

[0011] The second object of the present invention is to provide a method for preparing the elastic stamp imitating the stomatal structure of plant leaves, comprising the following steps:

[0012] S1: Spin-coating a positive photoresist on the surface of a substrate, and photolithography the positive photoresist to form a micrometer-sized small cylindrical photoresist bump array; then heating the small cylindrical photoresist bump array to 120-160° C. to melt, and then cooling and naturally forming a hemispherical photoresist bump array, thereby obtaining a substrate having a hemispherical photoresist bump array;

[0013] S2: Spin-coating a layer of polydimethylsiloxane prepolymer solution on the surface of the substrate of the hemispherical photoresist bump array and heating it to 60-100° C. to cross-link and solidify it to form a polymer film layer composed of polydimethylsiloxane;

[0014] S3: bombarding the surface of the polymer film layer with argon ions so that the highest height of the hemispherical photoresist bump array is consistent with the polymer film layer;

[0015] S4: removing the photoresist by using a degumming solution, and forming pores with hemispherical micro cavities inside at positions corresponding to the hemispherical photoresist convex dot array, so that the substrate at the corresponding position is exposed; then the sample is cleaned and dried with nitrogen to obtain the elastic stamp imitating the plant leaf stomatal structure.

[0016] Furthermore, the substrate in step S1 is cleaned with a piranha solution before use; the piranha solution is a mixed solution of concentrated sulfuric acid and hydrogen peroxide in a weight ratio of 3:1.

[0017] Furthermore, the positive photoresist in step S1 is AZP 4620 photoresist.

[0018] Furthermore, the prepolymer liquid in step S2 is a mixture of a polydimethylsiloxane prepolymer (i.e., a long-chain polymer molecule of polydimethylsiloxane having a flexible Si-O main chain and methyl side groups) and a curing agent (vinyl crosslinking agent and platinum catalyst) in a weight ratio of 10:1.

[0019] Furthermore, the thickness of the polymer film layer formed in step S2 should be lower than the highest height of the hemispherical photoresist bump array.

[0020] Furthermore, the degumming solution in step S4 is acetone, N-methyl-pyrrolidone, dimethyl sulfoxide and a mixed solution thereof.

[0021] The present invention also provides a device transfer method of the elastic stamp imitating the stomatal structure of plant leaves, and the specific steps are as follows:

[0022] 1) Picking up the device

[0023] The elastic stamp is attached to the device on the upper surface of the donor substrate, and the air in the pores of the elastic stamp is heated to discharge the air in the hemispherical micro-cavities of the pores. The air pressure in the pores decreases and forms a negative pressure with the atmospheric pressure, so that the elastic stamp / device interface is in an adhered state under the action of the atmospheric pressure, and the device is then picked up from the donor substrate;

[0024] 2) Release of the device

[0025] The air in the pores of the elastic stamp that has picked up the device is heated, so that the air pressure in the hemispherical microcavity of the pore increases and is greater than the atmospheric pressure to form a positive pressure, so that the elastic stamp / device interface is in a debonding state due to the pressure in the microcavity, and the device is released onto the host substrate.

[0026] Furthermore, the air heating method is laser irradiation heating, and the air temperature in the micro-cavity of the pores can be regulated by laser irradiation of the pores of the elastic seal, thereby driving the discharge / entry of air inside / outside the micro-cavity; by laser irradiation of the global pore array on the surface of the elastic seal, the elastic seal can be subjected to global contact pressurization to achieve large-scale device transfer; in addition, the pore array on the surface of the elastic seal can also be locally irradiated with a laser, and the required pores can be selectively driven to achieve selective device transfer.

[0027] Different from the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention proposes an elastic stamp that imitates the stomatal structure of plant leaves. The surface of the polymer layer of the elastic stamp has pores. The air temperature in the micro-cavity of the pores can be regulated by laser irradiation of the pores of the elastic stamp, thereby driving the discharge / entry of air inside / outside the micro-cavity; by laser irradiation of the global stomatal array on the surface of the elastic stamp, the elastic stamp can be globally contact-pressurized to achieve large-scale device transfer; in addition, the stomatal array on the surface of the elastic stamp can also be locally irradiated with a laser to selectively drive the required pores to achieve selective device transfer.

[0029] 2. Compared with the cylindrical pores of previous elastic stamps, the hemispherical pores of the present invention are more stable and will not be skewed or shrink unevenly, which can effectively improve the stability and accuracy of device picking. The stamp structure is simple and the preparation cost is low.

[0030] 3. The elastic stamp preparation method proposed in the present invention is simple and convenient, and does not require complicated preparation processes such as substrate etching and stamp demolding. In addition, elastic stamps with different pore sizes and numbers can be prepared by adjusting the size and number of photoresist bumps. It is worth mentioning that the pore size is closely related to the air pressure stored and released by the pores. The adjustment of the pore size can change the air pressure stored and released by the pores, thereby affecting the internal and external air pressure difference at the seal / device interface, and thereby affecting the adhesion of the seal / device interface. Based on this, the stamp prepared by this method has a wide range of applications, a wide adjustable viscosity range, and strong adhesion. In the process of transferring tiny devices, the devices can be accurately and parallelly transferred to the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The schematic diagram of the structure of the elastic stamp imitating the stomatal structure of plant leaves of the present invention.

[0032] Figure 2 The present invention is a flow chart of the preparation of an elastic stamp imitating the stomatal structure of plant leaves.

[0033] Figure 3 This is the SEM image of an elastic stamp that mimics the stomatal structure of plant leaves.

[0034] Figure 4 The present invention is a schematic diagram of the process of applying the plant-mimicking stomata structure elastic stamp of the present invention to device picking.

[0035] Figure 5 The present invention is a schematic diagram of the process of applying the plant-mimicking stomatal structure elastic stamp to device release.

[0036] The numbers in the figure represent:

[0037] 1. Polymer film layer; 2. Substrate; 3. Cylindrical photoresist bump; 4. Air hole; 5. Hemispherical photoresist bump; 6. Device; 7. Donor substrate; 8. Acceptor substrate. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings and preferred embodiments. The given embodiments are only for illustrating the present invention, rather than for limiting the scope of the present invention.

[0039] Example 1

[0040] This embodiment provides an elastic stamp imitating the pore structure of plant leaves, and its structural schematic diagram is shown in FIG. Figure 1 As shown, the elastic stamp has a double-layer structure, including a substrate 2 and a polymer film layer 1 located on the upper surface of the substrate 2; the surface of the polymer film layer 1 is provided with a plurality of pores 4, the interior of the pores 4 is a hemispherical micro cavity, and is connected to the substrate 2 located below the polymer film layer 1;

[0041] The polymer film layer 1 is a highly transparent elastic material, specifically polydimethylsiloxane; the substrate 2 is a quartz glass substrate.

[0042] The preparation method of the elastic stamp imitating the stomatal structure of plant leaves is as follows: Figure 2 As shown, the following steps are included:

[0043] S1: Spin-coating a positive photoresist on the surface of a substrate 2, and photolithography of the positive photoresist forms an array of small cylindrical photoresist bumps 3 of micrometer scale; then heating the array of small cylindrical photoresist bumps 3 to 120° C. to melt, and then cooling and naturally forming an array of hemispherical photoresist bumps 5, thereby obtaining a substrate 2 having an array of hemispherical photoresist bumps 5;

[0044] S2: Spin-coating a layer of polydimethylsiloxane prepolymer solution on the surface of the substrate of the hemispherical photoresist bump array 5 and heating it to 60° C. and maintaining it for 2 hours to cross-link and solidify it to form a polymer film layer 1 composed of polydimethylsiloxane; the thickness of the formed polymer film layer should be lower than the highest height of the hemispherical photoresist bump array;

[0045] S3: bombarding the surface of the polymer film layer 1 with argon ions so that the highest height of the array of hemispherical photoresist bumps 5 is consistent with the polymer film layer 1;

[0046] S4: using a degumming solution (acetone, N-methyl-pyrrolidone, dimethyl sulfoxide and a mixed solution thereof) to clean and remove the photoresist, and forming pores 4 with hemispherical micro-cavities inside at the positions corresponding to the array of hemispherical photoresist bumps 5, so that the substrate 2 at the corresponding positions is exposed; then the sample is cleaned and dried with nitrogen to obtain the elastic stamp imitating the stomatal structure of plant leaves.

[0047] Wherein, the substrate 2 described in step S1 is cleaned with piranha solution before use; the piranha solution is a mixed solution of concentrated sulfuric acid and hydrogen peroxide in a weight ratio of 3:1; the positive photoresist is AZP 4620 photoresist; the prepolymer liquid described in step S2 is a mixed solution of a prepolymer of polydimethylsiloxane (i.e., a long-chain polymer molecule of polydimethylsiloxane, which has a flexible Si-O main chain and methyl side groups) and a curing agent (vinyl crosslinking agent and platinum catalyst) in a weight ratio of 10:1.

[0048] like Figure 3 As shown, the SEM image of the elastic stamp imitating the stomatal structure of plant leaves prepared in this embodiment shows the leaf-like stomatal structure of the elastic stamp, confirming the successful preparation of the elastic stamp.

[0049] Example 2

[0050] This embodiment provides an elastic stamp imitating the pore structure of plant leaves, and its structural schematic diagram is shown in FIG. Figure 1 As shown, the difference from Example 1 is that: the substrate 2 is a sapphire substrate;

[0051] The preparation method of the elastic stamp imitating the stomatal structure of plant leaves is as follows: Figure 2 As shown, the difference from Example 1 is that:

[0052] In step S1, the small cylindrical photoresist bump 3 array is heated to 160° C. to melt, and then cooled to naturally form a hemispherical photoresist bump 5 array;

[0053] In step S2 , the prepolymer solution of polydimethylsiloxane is cured at 100° C. to form a polymer film layer 1 .

[0054] The remaining steps are the same as those in Example 1 and will not be described in detail herein. The elastic stamp imitating the stomatal structure of plant leaves provided in this embodiment has a structure similar to that in Example 1.

[0055] Example 3

[0056] This embodiment provides an elastic stamp imitating the pore structure of plant leaves, and its structural schematic diagram is shown in FIG. Figure 1As shown, the difference from Example 1 is that: the substrate 2 is a sapphire substrate;

[0057] The preparation method of the elastic stamp imitating the stomatal structure of plant leaves is as follows: Figure 2 As shown, the difference from Example 1 is that:

[0058] In step S1, the small cylindrical photoresist bump 3 array is heated to 140° C. to melt, and then cooled to naturally form a hemispherical photoresist bump 5 array;

[0059] In step S2, the prepolymerized polydimethylsiloxane solution is cured at 80° C. to form a polymer film layer 1 .

[0060] The remaining steps are the same as those in Example 1 and will not be described in detail herein. The elastic stamp imitating the stomatal structure of plant leaves provided in this embodiment has a structure similar to that in Example 1.

[0061] Example 4

[0062] In this embodiment, the elastic stamp imitating the plant pore structure described in Embodiment 1 is applied to device transfer, and the specific steps are as follows:

[0063] 1) Picking up the device

[0064] like Figure 4 As shown, the elastic stamp is attached to the device 6 located on the upper surface of the donor substrate 7, and the air in the pores 4 of the elastic stamp is heated to discharge the air in the hemispherical micro-cavities of the pores 4. The air pressure in the pores 4 then drops and forms a negative pressure with the atmospheric pressure, so that the elastic stamp / device interface is in an adhered state under the action of the atmospheric pressure, and then the device 6 is picked up from the donor substrate 7;

[0065] 2) Release of the device

[0066] like Figure 5 As shown, the air in the pore 4 of the elastic stamp that has picked up the device 6 is heated, so that the air pressure in the hemispherical microcavity of the pore 4 increases and becomes greater than the atmospheric pressure to form a positive pressure, so that the elastic stamp / device interface is in a debonding state due to the pressure in the microcavity, thereby releasing the device 6 onto the receiving substrate 8.

[0067] The air is heated by laser irradiation; the device 6 is a micro-nano device.

[0068] Through the above steps, the device of this embodiment is smoothly transferred from the donor substrate to the acceptor substrate by the transfer printing method.

[0069] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. An elastic stamp imitating the stomata structure of plant leaves, characterized in that: The elastic stamp has a double-layer structure, comprising a substrate (2) and a polymer film layer (1) located on the upper surface of the substrate (2); The surface of the polymer film layer (1) is provided with a plurality of pores (4), the interior of the pores (4) is a hemispherical micro cavity, and is connected to the substrate (2) located below the polymer film layer (1); The polymer film layer (1) is a highly transparent elastic material; the substrate (2) is a quartz glass substrate or a sapphire substrate.

2. The elastic stamp imitating the pore structure of plant leaves as claimed in claim 1, characterized in that: The polymer film layer (1) is specifically polydimethylsiloxane.

3. A method for preparing an elastic stamp imitating the stomatal structure of plant leaves as claimed in claim 2, characterized in that: The steps include: S1: Spin-coating a positive photoresist on the surface of a substrate (2), and photolithography of the positive photoresist forms an array of small cylindrical photoresist bumps (3) of micrometer scale; then heating the array of small cylindrical photoresist bumps (3) to 120-160° C. to melt, and then cooling and naturally forming an array of hemispherical photoresist bumps (5), thereby obtaining a substrate (2) having an array of hemispherical photoresist bumps (5); S2: Spin coating a layer of polydimethylsiloxane prepolymer solution on the surface of the substrate having the hemispherical photoresist bump array (5) and heating the prepolymer solution to 60-100° C. to crosslink and solidify the prepolymer solution to form a polymer film layer (1) composed of polydimethylsiloxane; S3: bombarding the surface of the polymer film layer (1) with argon ions so that the highest height of the array of hemispherical photoresist bumps (5) is consistent with the polymer film layer (1); S4: using a degumming liquid to clean and remove the photoresist, the positions corresponding to the array of hemispherical photoresist bumps (5) respectively form pores (4) with hemispherical micro-cavities inside, so that the substrate (2) at the corresponding positions is exposed; then the sample is cleaned and dried with nitrogen to obtain the elastic stamp imitating the plant leaf pore structure.

4. The method for preparing the elastic stamp imitating the stomatal structure of plant leaves according to claim 3, characterized in that: In step S1, the substrate (2) is cleaned with a piranha solution before use; the piranha solution is a mixed solution of concentrated sulfuric acid and hydrogen peroxide in a weight ratio of 3:

1.

5. The method for preparing the elastic stamp imitating the stomatal structure of plant leaves according to claim 3, characterized in that: The positive photoresist in step S1 is AZP 4620 photoresist.

6. The method for preparing the elastic stamp imitating the stomatal structure of plant leaves according to claim 3, characterized in that: The polydimethylsiloxane prepolymer liquid in step S2 is a mixture of polydimethylsiloxane prepolymer and curing agent in a weight ratio of 10:1; the curing agent is a mixture of a vinyl crosslinking agent and a platinum catalyst.

7. The method for preparing the elastic stamp imitating the stomatal structure of plant leaves according to claim 3, characterized in that: The thickness of the polymer film layer (1) formed in step S2 should be lower than the highest height of the hemispherical photoresist bump (5) array.

8. A device transfer method of the elastic stamp imitating plant pore structure as claimed in claim 1, characterized in that: The specific steps are as follows: 1) Picking up the device The elastic stamp as claimed in claim 1 is attached to the upper part of the device (6) located on the upper surface of the donor substrate (7), and the air in the pores (4) of the elastic stamp is heated to discharge the air in the hemispherical micro-cavities of the pores (4), and the air pressure in the pores (4) is reduced to form a negative pressure with the atmospheric pressure, so that the elastic stamp / device interface is in an adhered state under the action of the atmospheric pressure, and the device (6) is then picked up from the donor substrate (7); 2) Release of the device The air in the pores (4) of the elastic stamp as claimed in claim 1 which has picked up the device (6) is heated, so that the air pressure in the hemispherical micro-cavity of the pore (4) increases and becomes greater than the atmospheric pressure to form a positive pressure, so that the elastic stamp / device interface is in a debonding state due to the pressure in the micro-cavity, and the device (6) is released onto the receiving substrate (8).

9. The device transfer method using the elastic stamp imitating plant pore structure according to claim 8, characterized in that: The air is heated by laser irradiation.

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