WO2025141772A1 - Structural body - Google Patents

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

The present invention relates to a structure having a laminate capable of self-assembly.

　Micro-three-dimensional shapes using so-called self-assembly, in which thin films patterned on a substrate spontaneously assemble into three-dimensional shapes using tension or stress, are being applied to the fabrication of three-dimensional electrodes that contain biological tissues such as cells and nerve bundles and measure their electrical activity. Micro-three-dimensional shapes have attracted attention because they make it possible to deform thin films into a variety of shapes when contacting three-dimensional electrodes to conform to the shapes of flexible structures with curved surfaces such as cells and biological tissues.

In particular, the self-assembly technique, which forms a thin-film pattern consisting of graphene and a thin polymer film on a sacrificial layer and utilizes the stress released when the sacrificial layer is dissolved, can be used for cell culture and the evaluation of its electrical properties, because the thin-film material used is low-cost, highly biocompatible, and easy to process into various patterns (Non-Patent Document 1).

However, in the conventional technology, there is a problem that it is difficult to control the direction of self-assembly. For example, a rectangular thin film pattern 10 (L ₁ ×L ₂ , L ₁ >L ₂ ) (FIG. 8A) self-assembles into a cylindrical shape, but unless a skilled operation such as using a heat-sensitive thin film and temperature control is performed (Non-Patent Document 1), in self-assembly using the dissolution of a sacrificial layer, the rectangular thin film pattern 10 is almost always cylindrical in the long axis direction (cylindrical with the long side direction as the axial direction) (FIG. 8B). Self-assembly gradually begins from the melted part of the sacrificial layer, in this case the edge part of the rectangle, but since 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 in the short axis direction (cylindrical with the short side direction as the axial direction) (FIG. 8C).

As an example, when considering wrapping a rectangular thin film pattern 10 around a fiber-like biological tissue 11, it is inconvenient to wrap it in a cylindrical shape in the long axis direction (Figure 9A). When self-assembling a rectangular thin film pattern as if wrapping a fiber, it is preferable to assemble it in a cylindrical shape in the short axis direction (Figure 9B). This is because wrapping a fiber in a cylindrical shape in the long axis direction requires a side (long side) longer than the length (short side) required for wrapping, resulting in a thin film with a large area. The larger the thin film area, the greater the risk of measurement noise and damage to the thin film, so it is preferable to perform electrical measurements in which the rectangular thin film self-assembles in the short axis direction to form a cylindrical thin film that comes into contact with the thin wire over the minimum necessary area.

However, as mentioned above, rectangular thin film patterns tend to self-assemble into cylinders along the long axis, making electrical measurements in living organisms difficult in this state. It is possible to use a square pattern instead of a rectangle, but a square pattern has a low probability of self-assembling into a cylinder and cannot be used as is. As described above, even when simply forming a cylinder from a rectangular thin film pattern, control of the direction of cylindrical formation becomes important for sample evaluation and micro-sample creation.

Non-Patent Document 2 discloses a technology for controlling the self-assembly direction of such thin films. Non-Patent Document 2 discloses a technology 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. This technology is able to control the direction of self-assembly, but it is intended for sizes of mm or more, and since the gel thin film self-assembles in a way that 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.

S. Chen et al., “Kirigami/origami: unfolding the new regime of advanced 3D microfabrication/nanofabrication with “folding”” Light: Science & Applications (2020) J. C. 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.

The present invention was made in consideration of the above circumstances, and aims to provide a structure that allows for self-assembly and directional control.

To solve the above problems, the present invention adopts the following measures.

The structure according to one aspect of the present invention is a structure having a laminate capable of self-assembly, 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 laminated thereon, the outer periphery of the laminate having a curved region that curves with the self-assembly and a non-curved region that does not curve, and the laminate has a number of through holes aligned along the non-curved region of the outer periphery and penetrating in the stacking direction.

The present invention provides a structure that allows for self-assembly and directional control.

1 is a cross-sectional view of a structure according to one embodiment of the present invention. FIG. FIG. FIG. 2 is a plan view of a laminate constituting the same structure. 5A to 5C are cross-sectional views of the same structure during the manufacturing process. 1A to 1C are plan views of the same structure during the manufacturing process. 1 is a photograph of the laminate obtained in Example 1 before self-assembly. 13 is a photograph of the same laminate after self-assembly. 1 is a photograph of the laminate obtained in Comparative Example 1 before self-assembly. 13 is a photograph of the same laminate after self-assembly. 1 is a photograph of the laminate obtained in Example 2 before self-assembly. 13 is a photograph of the same laminate after self-assembly. 1 is a photograph of the laminate obtained in Comparative Example 2 before self-assembly. 13 is a photograph of the same laminate after self-assembly. FIG. 1 shows a stack obtained according to the prior art before self-assembly. FIG. 2 is a view of the laminate after self-assembly in the longitudinal direction. FIG. 13 is a view of the laminate after self-assembly in the short axis direction. FIG. 13 is a diagram showing the state in which a biological tissue is brought close to the laminate and the laminate self-assembles in the longitudinal direction. FIG. 13 is a diagram showing the state in which a biological tissue is brought close to the laminate and the laminate self-assembles in the minor axis direction.

Below, structures according to embodiments 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 enlarged characteristic parts for the sake of convenience in order to make the features easier to understand, and the dimensional ratios of each component may not necessarily 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 to them, and may be modified as appropriate within the scope of the present invention.

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 layering direction L. FIG. 1C is a perspective view of the structure 100. The structure 100 is a self-assembling structure, and includes a substrate 101, a sacrificial layer 102, and a self-assembling layered structure 103.

The substrate 101 is a plate-like member having a flat surface 101. The constituent material of the substrate 101 may be any material that can be used in normal 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).

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

The laminate 103 is a thin film layer formed on the sacrificial layer 102, and is formed by laminating a conductive layer 104 and a dielectric layer 105. In this embodiment, the conductive layer 104 and the dielectric layer 105 are laminated one by one in this order, but the number of layers of the conductive layer 104 and the dielectric layer 105 and the order of lamination are not limited. For example, the layer structure may be one in which the dielectric layer 105 is sandwiched between two conductive layers 104, or one in which the conductive layer 104 is sandwiched between two dielectric layers 105. However, in either layer structure, the structure is assumed to be self-assembling, that is, the structure in which all layers are curved in the same direction. Such a layer structure can be obtained, for example, by configuring the Young's modulus to be smaller in the upper layers farther from the substrate 101.

The conductive layer 104 is preferably a two-dimensional atomic layer composed of atoms aligned along one plane, such as graphene or _MoS2 . The dielectric layer 105 can be composed of, for example, parylene (polyparaxylylene), a type of polymer.

2 is a plan view of the laminate 103 viewed from the lamination direction L. The outer periphery of the laminate 103 has a curved region R1 that curves as the laminate 103 self-assembles, and a non-curved region _R2 that does not curve. The curved region _R1 is a region in _which the dissolution of the sacrificial layer 102 progresses relatively quickly during self-assembly, causing the laminate to curve. The non-curved region _R2 is a region in which the dissolution of the sacrificial layer 102 progresses relatively slowly, and the curvature of the non-curved region R2 is suppressed by the curved region _R1 , which curves first.

When the laminate 103 is rectangular in plan view from the stacking direction L, the non-curved region _R2 is a region along any side of the 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).

The laminate 103 has a plurality of through holes (hole patterns) 106 arranged along a non-curved region R ₂ (here, a region near the short side) of the outer periphery and penetrating in the lamination direction L. The shape of the through holes 106 in a plan view from the lamination 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 (inner diameter) of the long side of the through holes 106 is preferably one tenth or less of the length of the long side (maximum diameter) of the laminate.

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 preferably one fifth (1/5) or less of the length _L1 (here, the length of the long side) of the laminate 103. The through holes 106 are preferably formed within this outer periphery. In other words, the non-curved region _R2 is a region having a width from the outer periphery edge of the laminate 103 to the inside, which is 1/5 or less of the length of the laminate 103.

The structure 100 can be fabricated by the following steps.

(Substrate cleaning)
The substrate 101 is cleaned with piranha, oxygen plasma, etc. If it is not possible to treat it with a strong acid such as piranha, it may be treated with an organic solvent such as ethanol, acetone, IPA, etc.

(Sacrificial layer formation)
A sacrificial layer 102 is formed on one of the main surfaces 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 by using photolithography or the like in combination. When the sacrificial layer 102 is made of metal or calcium alginate, it can be used as the sacrificial layer even after the photoresist pattern is removed with acetone.

(Conductor layer formation)
On the substrate 101 (here, one of the main surfaces 101a) on which the sacrificial layer 102 has been formed, for example, a two-dimensional atomic thin film is transferred as the conductive layer 104. 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 about 0.1 nm to 50 nm.

(Dielectric layer formation)
A dielectric layer 105 is formed. When parylene is used as the material of 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 two-dimensional thin film of a π-conjugated system such as graphene by π-π conjugation. Therefore, it is possible to prevent the formed dielectric layer 105 from being easily peeled off from the two-dimensional thin film of a π-conjugated system. When parylene is used, the thickness of the dielectric layer 105 is preferably 100 nm to 3000 nm.

(Patterning)
The resulting thin film of stack 103 is then patterned by lithography: Figure 3A shows a cross-sectional view of structure 100 during patterning, and Figure 3B shows a top view of structure 100 after patterning.

For example, as shown in FIG. 3A, resist 107 is spin-coated onto laminate 103. Resist 107 may be either positive or negative, but it is made so that resist 107 after development is formed in the areas where it is desired to leave a pattern. It is preferable that resist 107 forming the pattern 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.

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.

When bending and self-assembling a rectangular pattern to form a cylinder with the long side in the axial direction, hole patterns are provided on both short sides of the rectangular pattern. In this case, both long sides become curved sections and both short sides become non-curved areas. When bending and self-assembling a square pattern to form a cylinder, hole patterns are provided on both opposing ends that intersect with the axial direction of the cylinder.

The number, size, and position of the hole pattern can be adjusted according to the purpose. For example, if it is desired to obtain a self-assembled cylinder by bending a rectangle so that the long side direction is the axial direction, it is better to suppress the maximum size (maximum diameter) L of the hole pattern to within 1/10 of the size _L1 of the long side. For example, if the laminate is a rectangular pattern of 200 μm x 400 μm, the hole pattern is preferably up to 40 μm x 40 μm if it is a rectangle (square or rectangle), and is preferably up to 40 μm in diameter if it is a circle (perfect circle or ellipse). However, the size of the hole pattern is assumed to be a size that fits within the short side. If the laminate is a rectangular pattern, it is preferable that the hole pattern is arranged so that it fits within an area where the distance D from the short side is 1/5 or less of the long side.

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, the two-dimensional atomic layer, and the 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. After this dry etching, the structure 100 of this embodiment is obtained as shown in FIGS. 1A, 1B, and 1C.

As described above, in the structure 100 of this embodiment, by forming through holes in part of the outer periphery of the laminate, it is possible to control the self-assembly direction of the thin film of the laminate when the sacrificial layer is dissolved. For example, when the thin film has a rectangular pattern, by having through holes arranged in the short side, the sacrificial layer on the short side melts more quickly than on the long side, and as a result, cylindrical self-assembly with the short side direction as the axial direction can be preferentially caused. When the thin film has a square pattern, a self-assembled cylindrical shape can be obtained with high efficiency. This makes it possible to control the direction in which the thin film self-assembles in the direction surrounding the thin wires or particles, which is expected to have the effect of improving the evaluation of the electrical properties of the thin wires and the inclusion efficiency of the particles.

The effects of the present invention will be made clearer by the following examples. Note that the present invention is not limited to the following examples, and can be modified as appropriate without departing from the spirit of the present invention.

Example 1
According to the above embodiment, self-assembly of a laminate of rectangular thin film patterns having through holes was carried out.

Figure 4A is a photograph of the laminate formed before self-assembly (before the sacrificial layer was dissolved). A rectangular thin film pattern of 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 is 4-100 layers), and a sacrificial layer made of calcium alginate. The hole pattern (through hole) was a rectangle of 10 μm x 20 μm, and the center-to-center distance between the hole patterns was 30 μm.

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 direction as the axial direction. In this example, it is self-assembled into a double-roll type, but if the dielectric layer is laminated thickly, a single-roll cylindrical shape bent in the short axis direction can be obtained.

(Comparative Example 1)
Self-assembly of a laminate of rectangular thin film patterns without through holes was performed.

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

Figure 5B 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 long side direction as the axial direction.

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

Example 2
According to the above embodiment, self-assembly of a stack of square thin film patterns having through holes was carried out.

Figure 6A is a photograph of the laminate formed before self-assembly (before the sacrificial layer was dissolved). The conditions were the same as in Example 1, except that a laminate with 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.

Figure 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 axial direction aligned along the two selected sides.

(Comparative Example 2)
Self-assembly of a square thin film pattern laminate without through holes was performed.

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

Figure 7B 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 2, the laminate curved in a complex manner in random directions.

These results show that by forming through holes, it is possible to achieve self-assembly by creating through holes and bending the material into a cylindrical shape with the axial direction of two selected sides.

REFERENCE SIGNS LIST 100 Structure 101 Substrate 101a One main surface of substrate 102 Sacrificial layer 103 Laminate 104 Conductive layer 105 Dielectric layer 106 Through hole 107 Resist L Lamination direction R ₁ Curved region R ₂ Non-curved region

Claims (5)

A structure having a self-assembly structure,
A substrate;
A sacrificial layer formed on one main surface of a substrate;
a laminate formed on the sacrificial layer and including a conductive layer and a dielectric layer;
an outer periphery of the laminate has a curved region that curves as the laminate self-assembles and a non-curved region that does not curve;
A structure characterized in that the laminate has a plurality of through holes aligned along the non-curved region of the outer periphery and penetrating in the stacking direction. When viewed in a plan view from the stacking direction, the stack is rectangular,
2. The structure of claim 1, wherein the non-curved region is along one side of the rectangle. In the plan view, the laminate is rectangular,
3. The structure of claim 2, wherein the non-curved region is along a short side of the rectangle. The structure described in either 1 or 2, characterized in that the inner diameter of the through hole is 1/10 or less of the maximum diameter of the laminate. The structure described in either claim 1 or 2, characterized in that the non-curved region is a region extending inward from the outer peripheral edge of the laminate and having a width of 1/5 or less of the length of the laminate.

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