Structural body

Abstract

A structural body (100) according to the present invention has a structure capable of self assembly, said structural body comprising: a substrate (101); a sacrificial layer which is formed on one main surface of the substrate; and a laminate (103) which is formed on the sacrificial layer and which is obtained by laminating a conductor layer and a dielectric layer, wherein an outer peripheral part of the laminate (103) has a bending region (R1) that bends along with self assembly and a non-bending region (R2) that does not bend, and the laminate (103) has a plurality of through holes (106) that are arranged along the non-bending region (R2) of the outer peripheral part and that pass therethrough in the lamination direction.

Description

structure

[0001] The present invention relates to a structure comprising a laminate capable of self-assembly.

[0002] Self-assembly of thin films patterned on a substrate into a three-dimensional shape spontaneously under tension or stress has been applied to the fabrication of three-dimensional electrodes that encase biological tissues such as cells and nerve bundles and measure their electrical activity. Micro-three-dimensional structures have attracted attention because they enable the thin films to be deformed into a variety of shapes, allowing the three-dimensional electrodes to be brought into contact with flexible structures with curved surfaces such as cells and biological tissues.

[0003] In particular, a self-assembly technique in which a thin film pattern consisting of graphene and a polymer thin film is formed on a sacrificial layer and the stress released when the sacrificial layer is dissolved is utilized. The thin film material used is low-cost, highly biocompatible, and can be easily processed into various patterns, making it useful for cell culture and the evaluation of its electrical properties (Non-Patent Document 1).

[0004] However, the conventional technology has a problem that it is difficult to control the direction of self-assembly. For example, １ ×L ２ , L １ >L ２ ) (Figure 8A) self-assembles into a cylindrical shape. However, unless skilled manipulations such as the use of a thermosensitive thin film and temperature control are used (Non-Patent Document 1), in self-assembly using the dissolution of a sacrificial layer, the rectangular thin film pattern 10 almost always becomes cylindrical along the long axis (i.e., the long side is the axial direction) (Figure 8B). Self-assembly gradually begins from the melted portion of the sacrificial layer, in this case the edge of the rectangle. However, because the long side has a larger melting area than the short side, bending due to self-assembly is preferentially induced from the long side. However, there are also cases where it is necessary to bend the rectangular thin film pattern 10 along the short axis (i.e., the short side is the axial direction) (Figure 8C).

[0005] For example, when considering wrapping a rectangular thin film pattern 10 around a fiber-like biological tissue 11, cylindrical wrapping along the long axis is inconvenient ( Fig. 9A ). When self-assembling a rectangular thin film pattern like wrapping a fiber, it is preferable to assemble it cylindrically along the short axis ( Fig. 9B ). This is because wrapping a fiber along the long axis requires a longer side (long side) than the length (short side) required for wrapping, resulting in a large thin film area. Since a larger thin film area increases the risk of measurement noise and damage to the thin film, electrical measurements are preferably performed using a cylindrical thin film obtained by self-assembling the rectangular thin film along the short axis, which allows contact with the thin wire over the minimum necessary area.

[0006] However, as mentioned above, rectangular thin film patterns tend to self-assemble into cylinders along their long axis, making electrical measurements in living organisms difficult in this state. While it might be possible to use square patterns instead of rectangles, square patterns have a low probability of self-assembling into cylinders and cannot be used in this state. As described above, even when simply forming a rectangular thin film pattern into a cylinder, controlling the direction of cylindrical formation is important for sample evaluation and the fabrication of micro-samples.

[0007] Non-Patent Document 2 discloses a technique for controlling the self-assembly direction of such thin films. Non-Patent Document 2 discloses a technique in which one of two gel thin film layers contains alginate chains, and the direction of self-assembly is controlled by the concentration of added cations. While this technique is capable of controlling the direction of self-assembly, it is intended for sizes of mm or more, and since the gel thin film self-assembles, which requires adjustment of the concentration of added cations, it is disadvantageous in terms of drying, durability, and operability. To self-assemble any thin film other than a gel thin film, it is necessary to develop a method other than the prior art.

[0008] S. Chen et al., “Kirigami / origami: unfolding the new regime of advanced 3D microfabrication / nanofabrication with “folding” ” Light: Science & Applications (2020)JC Athas et al., “Cation-induced folding of alginate-bearing bilayer gels: an unusual example of spontaneous folding along the long axis” Soft Matter (2018) Vol.14 2735-2743.

[0009] The present invention has been made in view of the above circumstances, and has as its object to provide a structure that allows self-assembly and direction control thereof.

[0010] In order to solve the above problems, the present invention employs the following means.

[0011] A structure according to one aspect of the present invention is a structure comprising a self-assembling laminate, comprising a substrate, a sacrificial layer formed on one main surface of the substrate, and a laminate formed on the sacrificial layer and comprising a dielectric layer and a conductive layer stacked together, wherein the outer periphery of the laminate has a curved region that curves with the self-assembly and a non-curved region that does not curve, and the laminate has a plurality of through holes aligned along the non-curved region of the outer periphery and penetrating in the stacking direction.

[0012] According to the present invention, it is possible to provide a structure that allows self-assembly and direction control thereof.

[0013] 1 is a cross-sectional view of a structure according to one embodiment of the present invention; 2 is a plan view of the structure; 3 is a perspective view of the structure; 4 is a plan view of a laminate constituting the structure; 5 is a cross-sectional view during the manufacturing process of the structure; 6 is a plan view of the structure during the manufacturing process; 7 is a photograph of the laminate obtained in Example 1 before self-assembly; 8 is a photograph of the laminate after self-assembly; 9 is a photograph of the laminate obtained in Comparative Example 1 before self-assembly; 10 is a photograph of the laminate after self-assembly; 11 is a photograph of the laminate obtained in Example 2 before self-assembly; 12 is a photograph of the laminate after self-assembly; 13 is a photograph of the laminate obtained in Comparative Example 2 before self-assembly; 14 is a photograph of the laminate after self-assembly; 15 is a view of a laminate obtained by conventional technology before self-assembly; 16 is a view of the laminate after self-assembly in the long axis direction; 17 is a view of the laminate after self-assembly in the short axis direction; 18 is a view of the laminate brought close to the laminate and self-assembled in the long axis direction; 19 is a view of the laminate brought close to the laminate and self-assembled in the short axis direction.

[0014] Hereinafter, a structure according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the drawings used in the following description may show characteristic portions enlarged for the sake of clarity, and the dimensional ratios of the components may not be the same as in reality. Furthermore, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate modifications may be made within the scope of the present invention.

[0015] Fig. 1A is a cross-sectional view showing the layered structure of a structure 100 according to one embodiment of the present invention. Fig. 1B is a plan view of the structure 100 viewed from the stacking direction L. Fig. 1C is a perspective view of the structure 100. The structure 100 has a self-assembling structure and includes a substrate 101, a sacrificial layer 102, and a self-assembling layered body 103.

[0016] The substrate 101 is a plate-like member having one flat surface 101. The constituent material of the substrate 101 may be any material that can be used in ordinary semiconductor processes, such as glass, silicon, plastic, etc. The constituent material of the substrate 101 may also be a flexible material such as polyethylene terephthalate (PET).

[0017] The sacrificial layer 102 is formed on one main surface of the substrate. The sacrificial layer 102 is composed of a material that can be removed by a predetermined method without damaging the thin film layers or biological tissue. The material for the sacrificial layer 102 is not particularly limited, but in this embodiment, calcium alginate is used as an example. A sodium alginate aqueous solution is filtered through a hydrophilic filter, spin-coated onto the solid substrate 101, and then immersed in a calcium chloride aqueous solution to obtain a gelled calcium alginate thin film. The calcium alginate thin film can be removed by adding EDTA (ethylenediaminetetraacetic acid), which chelates the calcium ions in the calcium alginate with the EDTA.

[0018] The laminate 103 is a thin film layer formed on the sacrificial layer 102 and formed by stacking a conductive layer 104 and a dielectric layer 105. While the present embodiment illustrates a case in which the conductive layer 104 and the dielectric layer 105 are stacked one by one in this order, the number of conductive layers 104 and the dielectric layer 105 and the stacking order are not limited. For example, the laminate 103 may have a layer structure in which the dielectric layer 105 is sandwiched between two conductive layers 104, or a layer structure in which the conductive layer 104 is sandwiched between two dielectric layers 105. However, in either layer structure, the laminate 103 must be self-assembling, i.e., all layers must be configured to bend in the same direction. Such a layer structure can be obtained, for example, by configuring the Young's modulus of the upper layers, which are farther from the substrate 101, to be smaller.

[0019] The conductive layer 104 is made of graphene, MoS ２The dielectric layer 105 is preferably a two-dimensional atomic layer made up of atoms arranged along one plane, as shown in the figure. The dielectric layer 105 can be made of, for example, parylene (polyparaxylene), which is a type of polymer.

[0020] 2 is a plan view of the laminate 103 as viewed from the stacking direction L. The outer periphery of the laminate 103 is curved as the laminate 103 self-assembles, forming a curved region R. １ and a non-curved region R ２ The curved region R １ The non-curved region R is a region where the dissolution of the sacrificial layer 102 proceeds relatively quickly during self-assembly and the sacrificial layer 102 curves. ２ The dissolution of the sacrificial layer 102 proceeds relatively slowly, and the curved region R curves first. １ This is the region where curvature is suppressed by

[0021] When the laminate 103 is rectangular in plan view from the lamination direction L, the non-curved region R ２ is a region along one of the sides of a rectangle. Here, a case is illustrated in which the laminate 103 is rectangular in plan view, and the non-curved region is a region along a short side of the rectangle (short side portion).

[0022] The laminate 103 has a non-curved region R ２ The laminate 103 has a plurality of through holes (hole patterns) 106 that are aligned along the laminate 103 (here, the region near the short side) and penetrate in the stacking direction L. The shape of the through holes 106 in a plan view from the stacking direction L is not particularly limited. The size (inner diameter) of the through holes 106 in the plan view is preferably one-tenth (1 / 10) or less of the size (maximum diameter) of the laminate 103. For example, when the laminate 103 and the through holes 106 are rectangular and arranged as shown in FIG. 2 , the length of the long side (inner diameter) of the through holes 106 is preferably one-tenth (1 / 10) or less of the length of the long side (maximum diameter) of the laminate.

[0023] The outer periphery of the laminate 103 is a region having a predetermined width (distance) D from the outer periphery edge to the inside. This width D is determined by the length L of the laminate 103 (here, the length of the long side). １It is preferable that the through-holes 106 are formed within this outer periphery. In other words, the non-curved region R ２ is a region extending inward from the outer peripheral edge of the laminate 103 and having a width equal to or less than 1 / 5 of the length of the laminate 103 .

[0024] The structure 100 can be fabricated by the following procedure.

[0025] (Substrate Cleaning) The substrate 101 is cleaned with piranha, oxygen plasma, etc. If treatment with a strong acid such as piranha is not possible, treatment with an organic solvent such as ethanol, acetone, or IPA may be used.

[0026] (Formation of Sacrificial Layer) A sacrificial layer 102 is formed on one main surface 101a of the cleaned substrate. At this time, the sacrificial layer 102 may be formed on the entire surface of the substrate 101, or the sacrificial layer 102 may be patterned in a predetermined region of the substrate 101 using photolithography or the like in combination. When the sacrificial layer 102 is made of metal or calcium alginate, it can be used as a sacrificial layer even after the photoresist pattern is removed with acetone.

[0027] (Conductor Layer Formation) For example, a two-dimensional atomic thin film is transferred as the conductor layer 104 onto the substrate 101 (here, one of the main surfaces 101a) on which the sacrificial layer 102 has been formed. The two-dimensional atomic layer may be an atomic layer peeled off from a two-dimensional crystal and transferred onto the substrate, or an atomic layer grown by CVD may be transferred. The two-dimensional atomic layer is preferably a monolayer to 100 atomic layers, with a thickness of approximately 0.1 nm to 50 nm.

[0028] (Dielectric Layer Formation) The dielectric layer 105 is formed. When parylene is used as the material for the dielectric layer 105, a parylene polymer grown by CVD from a dimer is formed. Parylene can be easily formed into a film by vapor deposition, and is strongly bonded to a π-conjugated two-dimensional thin film such as graphene through π-π conjugation. This prevents the formed dielectric layer 105 from easily peeling off from the π-conjugated two-dimensional thin film. When parylene is used, the thickness of the dielectric layer 105 is preferably 100 nm to 3000 nm.

[0029] (Patterning) The formed thin film of the laminate 103 is patterned by lithography. Fig. 3A is a cross-sectional view of the structure 100 during patterning. Fig. 3B is a plan view of the structure 100 after patterning.

[0030] For example, as shown in Fig. 3A, a resist 107 is spin-coated onto the laminate 103. The resist 107 may be either positive or negative, but it is formed so that the resist 107 after development is formed in the area where it is desired to leave a pattern. The resist 107 that forms the pattern preferably has a film thickness that is sufficient to remain without being removed even after the subsequent dry etching process. Note that although the thin film pattern is rectangular here, any pattern may be used depending on the purpose.

[0031] In this embodiment, the hole pattern (through hole 106) at the end of the thin film pattern (laminate 103) that controls the direction of self-assembly is also patterned at this stage, but the patterning of the thin film pattern and the hole pattern may be performed separately.

[0032] When a rectangular pattern is bent and self-assembled to form a cylinder with its long side oriented in the axial direction, hole patterns are provided on both short sides of the rectangular pattern. In this case, both long sides become curved and both short sides become non-curved regions. When a square pattern is bent and self-assembled to form a cylinder, hole patterns are provided on both opposing end sides that intersect with the axial direction of the cylinder.

[0033] The number, size, and position of the hole patterns can be adjusted according to the purpose. For example, if you want to obtain a self-assembled cylinder by bending a rectangle so that the long side direction is the axial direction, you can set the maximum size (maximum diameter) L of the hole pattern to the size of the long side L. １It is preferable to keep the hole size within 1 / 10 of the rectangular pattern. For example, if the laminate has a rectangular pattern of 200 μm x 400 μm, the hole pattern is preferably up to 40 μm x 40 μm if it is rectangular (square or oblong), and preferably up to 40 μm in diameter if it is circular (perfect circle or ellipse). However, the size of the hole pattern must be such that it fits within the short side. If the laminate has a rectangular pattern, it is preferable that the hole pattern be arranged so that the distance D from the short side is 1 / 5 or less of the long side.

[0034] After forming a pattern by lithography, the thin film layer outside the pattern is removed by dry etching as shown in FIG. 3A. For example, if the constituent materials of the sacrificial layer, two-dimensional atomic layer, and dielectric layer are calcium alginate, graphene, and parylene, respectively, the thin film layer outside the pattern can be removed by oxygen plasma treatment. Other conditions may be used depending on the purpose. If a thin film material that cannot be removed by oxygen plasma treatment is used, it can be removed by physical etching such as ion beam etching. After this dry etching, the structure 100 of this embodiment is obtained as shown in FIGS. 1A, 1B, and 1C.

[0035] As described above, in the structure 100 of this embodiment, by forming through-holes in a portion of the outer periphery of the laminate, the self-assembly direction of the thin film of the laminate can be controlled when the sacrificial layer is dissolved. For example, if the thin film has a rectangular pattern, by having through-holes arranged in the short side, the sacrificial layer on the short side dissolves more quickly than on the long side, resulting in preferential cylindrical self-assembly with the short side as the axial direction. If the thin film has a square pattern, self-assembled cylindrical shapes can be obtained with high efficiency. This makes it possible to control the self-assembly direction of the thin film surrounding the thin wires or particles, which is expected to be effective in evaluating the electrical properties of the thin wires and increasing the encapsulation efficiency of the particles.

[0036] The effects of the present invention will be more clearly understood from the following examples. Note that the present invention is not limited to the following examples and can be practiced with appropriate modifications within the scope of the present invention.

[0037] Example 1 In accordance with the above embodiment, a stack of rectangular thin film patterns having through holes was self-assembled.

[0038] Figure 4A is a photograph of the formed laminate before self-assembly (before dissolution of the sacrificial layer). A rectangular thin film pattern measuring 200 μm x 400 μm was formed, with through-holes on both short sides. From the top, the laminate had a dielectric layer made of parylene, a conductor layer made of single-layer or multi-layer graphene (multi-layer consisting of 4-100 layers), and a sacrificial layer made of calcium alginate. The hole pattern (through-hole) was a rectangle measuring 10 μm x 20 μm, with a center-to-center distance of 30 μm between the hole patterns.

[0039] Figure 4B is a photograph of the laminate after self-assembly (after dissolving the sacrificial layer). When EDTA (0.5 M) was dropped to dissolve the sacrificial layer, the laminate self-assembled into a double-roll shape with the short side as the axial direction. In this example, the laminate self-assembled into a double-roll shape, but if a thick dielectric layer is added, a single-roll cylindrical shape bent in the short axis direction can be obtained.

[0040] Comparative Example 1 Self-assembly of a laminate of rectangular thin film patterns without through holes was carried out.

[0041] 5A is a photograph of the formed laminate before self-assembly (before dissolution of the sacrificial layer). The conditions were the same as in Example 1, except that no through-holes were provided.

[0042] 5B is a photograph of the laminate after self-assembly (after dissolution of the sacrificial layer). When the sacrificial layer was dissolved under the same conditions as in Example 1, the laminate self-assembled into a single roll shape with the long side direction as the axial direction.

[0043] These results show that by forming through holes, it is possible to achieve self-assembly by bending the short side direction into a cylindrical shape with the axial direction.

[0044] Example 2 In accordance with the above embodiment, self-assembly of a stack of square thin film patterns having through holes was carried out.

[0045] 6A is a photograph of the formed laminate before self-assembly (before dissolution of the sacrificial layer). The conditions were the same as in Example 1, except that a square thin film pattern (200 μm × 200 μm) was used and through-holes were formed along two opposing sides selected from the four sides.

[0046] 6B is a photograph of the laminate after self-assembly (after dissolving the sacrificial layer). When the sacrificial layer was dissolved under the same conditions as in Example 1, the laminate self-assembled into a single roll shape with the selected two sides as the axial direction.

[0047] Comparative Example 2 Self-assembly of a square thin film pattern laminate without through holes was carried out.

[0048] 7A is a photograph of the formed laminate before self-assembly (before dissolution of the sacrificial layer). The conditions were the same as in Example 2, except that no through-holes were provided.

[0049] 7B is a photograph of the laminate after self-assembly (after dissolution of the sacrificial layer). When the sacrificial layer was dissolved under the same conditions as in Example 2, the laminate was curved in a complex manner in random directions.

[0050] These results show that by forming through holes, it is possible to realize self-assembly in which the through holes are provided and the material is bent into a cylindrical shape with the directions of two selected sides as the axial directions.

[0051] REFERENCE SIGNS 100 Structural body 101 Substrate 101a One main surface of the substrate 102 Sacrificial layer 103 Laminated body 104 Conductive layer 105 Dielectric layer 106 Through hole 107 Resist L Lamination direction R １ Curved area R ２ Non-curved area

Claims

1. A structure having a self-assembling structure, comprising: a substrate; a sacrificial layer formed on one main surface of the substrate; and a laminate formed by laminating a conductor layer and a dielectric layer on the sacrificial layer, wherein an outer peripheral portion of the laminate has a curved region that curves with the self-assembly and a non-curved region that does not curve, and the laminate has a plurality of through holes that are arranged along the non-curved region of the outer peripheral portion and penetrate in the lamination direction.

2. The structure according to claim 1, wherein in a plan view from the lamination direction, the laminate is rectangular, and the non-curved region is a region along any one of the sides of the rectangle.

3. The structure according to claim 2, wherein in the plan view, the laminate is rectangular, and the non-curved region is a region along the short side of the rectangle.

4. The structure according to any one of claims 1 or 2, wherein an inner diameter of the through hole is 1 / 10 or less of a maximum diameter of the laminate.

5. The structure according to any one of claims 1 or 2, wherein the non-curved region is a region having a width of 1 / 5 or less of the length of the laminate from an outer peripheral end of the laminate toward the inside.

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