Patent Grant
11961632
This application claims priorities to Korean patent application No. 10-2020-0168464, filed on Dec. 4, 2020 and Korean patent application No 10-2021-0151155, filed on Nov. 5, 2021. The contents of the applications are incorporated herein by reference in their entirety.
The present disclosure relates to a fabrication method of conductive nanonetworks using a mastermold, and more specifically, to a fabrication method of conductive nanonetworks using a mastermold by which electrical properties and optical properties of the conductive nanonetworks are improved by excluding contact resistance between nanowires and minimizing surface roughness of the conductive nanonetworks and a nanoelectrode having a large area can be easily formed by applying a method of replicating the conductive nanonetworks on the mastermold to a substrate, in forming the conductive nanonetworks.
[National R&D Program Which Supports This Invention]
[Project Identification Number] 1711119623
[Project Number] 2020M3H4A1A02084906
[Ministry Name] Ministry of Science and ICT
[Project Management (Specialized) Agency Name] National Research Foundation of Korea
[Research Program Name] Source Technology Development of Future Nano-Material (R&D)
[Research Project Title] Development of technology for optimizing high-efficient material and element for 100%-or-more-stretchable material-specific stretchable organic solar cell
[Contribution Rate] 34/100
[Project Implementation Institute Name] Korea Advanced Institute of Science and Technology
[Research Period] Jul. 1, 2020 to Dec. 31, 2020
[National R&D Program Which Supports This Invention]
[Project Identification Number] 1711120360
[Project Number] 2020M3D1A2102869
[Ministry Name] Ministry of Science and ICT
[Project Management (Specialized) Agency Name] National Research Foundation of Korea
[Research Program Name] Future Material Discovery Support (R&D)
[Research Project Title] Development of new high-performance material and element for electrochromic transparent display for vehicle
[Contribution Rate] 33/100
[Project Implementation Institute Name] University of Seoul
[Research Period] Jul. 23, 2020 to Jan. 22, 2021
[National R&D Program Which Supports This Invention]
[Project Identification Number] 1711135134
[Project Number] 2020R1A4A1018516
[Ministry Name] Ministry of Science and ICT
[Project Management (Specialized) Agency Name] National Research Foundation of Korea
[Research Program Name] Group Research Support (R&D)
[Research Project Title] Development of stretchable solar cell with consistent performance
[Contribution Rate] 33/100
[Project Implementation Institute Name] Korea Advanced Institute of Science and Technology
[Research Period] Jun. 1, 2021 to Feb. 28, 2022
Indium tin oxide (ITO) having properties of optical transmittance of about 85% and sheet resistance of 15 Ω/sq is widely used for nanoelectrodes of various display modules. However, limited reserves and mines of an indium component in ITO result in unstable supply and demand and a relatively high price thereof. In addition, an ITO deposition process has to be performed by expensive and large-sized vacuum equipment with high maintenance costs, and the oxide has a property of brittleness and thus is not suitable to be applied to a flexible electrode.
Recently, research on a conductive nanofilm using flexible metal nanowires which can be produced through a low temperature process has been actively carried out. For example, Korean Patent Registration No. 1011447 discloses a technology of manufacturing a metal polymer film by drying a metal polymer solution, in which metal nanowires are dispersed, on a mold, and stretching the metal polymer film in one direction. In addition, U.S. patent Ser. No. 10/831,233 discloses a technology of patterning a conductive layer, the method including coating a substrate (matrix) with a conductive layer containing nanowires, over-coating a pattern with a peelable polymer layer in a state where a resister pattern is formed over the conductive layer, and then removing the conductive layer formed in a region in which the resist pattern is not formed, by removing the peelable polymer layer.
However, in the related art described above, the conductive nanofilm is formed with metal nanowires being overlapped on one another, and thus the technologies in the related art have drawbacks of unavoidable contact resistance between metal nanowires and high surface roughness. In addition, a post-processing treatment such as a thermal annealing or a laser treatment is required in order to reduce the contact resistance between metal nanowires, and the treatment is a process unsuitable for a flexible polymer substrate. Besides, a solution process according to the related art is difficult to apply to a very hydrophobic substrate.
The present disclosure is made to solve problems described above, and an object thereof is to provide a fabrication method of conductive nanonetworks using a mastermold by which electrical properties and optical properties of the conductive nanonetworks can be improved by excluding contact resistance between nanowires and minimizing surface roughness of the conductive nanonetworks in forming the conductive nanonetworks.
In addition, another object of the present disclosure is to provide a technology of enabling a nanoelectrode having a large area to be easily formed and waste of a conductive material to be reduced by applying a method of replicating conductive nanonetworks on a mastermold to a substrate.
A fabrication method of conductive nanonetworks using a mastermold according to the present disclosure to achieve the objects includes: preparing a mastermold that has a conductive nanonetwork replicating region patterned in relief; coating the mastermold with a conductive material; and forming conductive nanonetworks on an application target substrate by replicating a conductive material, with which the conductive nanonetwork replicating region is coated, onto the application target substrate.
The mastermold that has the conductive nanonetwork replicating region patterned in relief may be fabricated through a process of applying nanowire networks on a mastermold forming substrate, a process of patterning a region having the nanowire networks in relief by anisotropically etching the mastermold forming substrate on which the nanowire networks are applied, and a process of removing the nanowire networks. The region patterned in relief may correspond to the conductive nanonetwork replicating region patterned in relief of the mastermold.
The fabrication method of conductive nanonetworks using a mastermold may further include, before the coating of the mastermold with the conductive material: forming a hydrophilic thin film layer on the mastermold; and forming a hydrophobic surface treatment layer on the hydrophilic thin film layer, in sequence. The hydrophilic thin film layer may contain a hydrophilic group so as to be bonded to the hydrophobic surface treatment layer, and the hydrophobic surface treatment layer may contain a hydrophobic group so as to be inhibited from being bonded to a conductive material.
The nanowire networks may be formed through electrospinning.
A geometric shape of the nanowire networks may correspond to a geometric shape of the conductive nanonetworks formed on the application target substrate, and electrical properties and optical properties of the conductive nanonetworks may be controllable by changing the geometric shape of the conductive nanonetworks through adjustment of a geometric shape of nanowire networks which are applied.
The geometric shape of the nanowire networks which are to be formed on a substrate may be adjustable by adjusting at least one of a diameter of a needle of an electrospinning device, a voltage applied to the needle, and a concentration of a solution containing a material which is used to form the nanowire networks.
The conductive material may be any one of conductive metal, a carbon-based conductive material, conductive polymer, and conductive nanoparticles, or a combination thereof.
The above and other aspects, features and advantages of the disclosed example embodiments will be more apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Example embodiments are described more fully hereinafter. The example embodiments may, however, be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein. In the description, details of features and techniques may be omitted to more clearly disclose example embodiments.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. All methods described herein can be performed in a suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”), is intended merely to better illustrate the example embodiments and does not pose a limitation on the scope of the present disclosure unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the present disclosure as used herein.
The term “comprises” or “includes” as used herein throughout this specification, specifies presence of stated elements, but does not preclude presence or addition of one or more other elements unless the context clearly indicates otherwise.
The present disclosure provides a technology of fabricating conductive nanonetworks through a new process.
As described above in ‘Description of the Related Art’, a conductive nanofilm made of metal nanowires is provided to substitute for an ITO nanoelectrode of the related art, and the conductive metal-nanowire nanofilm is fabricated typically through using a nanowire solution. The solution process using a nanowire solution is a process of forming a conductive nanofilm having a configuration in which metal nanowires are connected to one another, by applying a solution containing dispersed metal nanowires on a substrate and removing a solvent. The conductive nanofilm made of metal nanowires can be fabricated through the process; however, the metal nanowires which are randomly dispersed in a solution are connected to one another in an overlapping manner. Hence, a finally fabricated conductive metal-nanowire nanofilm unavoidably has high surface roughness and contact resistance between nanowires, and it is not possible to adjust a height of the conductive metal-nanowire nanofilm.
According to example embodiments of the present disclosure, the conductive nanonetworks are fabricated using a mastermold, and thus a problem of contact resistance between nanowires is excluded, and the surface roughness of the finally fabricated conductive nanonetworks is minimized.
In addition, according to example embodiments of the present disclosure, the conductive nanonetworks on a mastermold are replicated to a substrate; thus, the invention is suitable for a process of forming a nanoelectrode having a large area, and unnecessary waste of a conductive material can be reduced.
Besides, example embodiments of the present disclosure provides a technology of selectively adjusting electrical properties and optical properties of conductive nanonetworks by adjusting a thickness of the conductive nanonetworks and controlling a material of nanowire networks used for patterning of the mastermold.
On the other hand, the ‘conductive nanonetwork’ in example embodiments of the present disclosure means that a conductive material forms a nanosized network. The ‘conductive nanonetwork’ in example embodiments of the present disclosure corresponds to the conductive nanofilm which is similar to ‘forming a mesh shape by metal nanowires’ in the related art; however, the term ‘conductive nanonetwork’ is used in example embodiments of the present disclosure, because there is a difference in configuration between example embodiments of the present disclosure and the related art using the metal nanowires. In the related art, connection between metal nanowires is induced; on the other hand, in example embodiments of the present disclosure, direct forming of the ‘nanosized network by the conductive material’ is performed without using metal nanowires, and thus the ‘conductive nanonetwork’ in example embodiments of the present disclosure can be described to have a technical configuration different from that of ‘forming the mesh shape by metal nanowires’ in the related art.
Figuratively and briefly describing, in the fabrication method of conductive nanonetworks according to example embodiments of the present disclosure, in a state where a shape corresponding to the conductive nanonetworks is patterned in relief on a mastermold, and the relief of the mastermold is coated with a conductive material, the conductive nanonetworks are formed on an application target substrate by replicating the coating material on the relief to the application target substrate.
Hereinafter, the fabrication method of conductive nanonetworks using a mastermold according to an embodiment of the present disclosure will be described in detail with reference to the drawings.
With reference to
First, the processes of fabricating the mastermold proceed as follows.
A mastermold forming substrate 110 is prepared, and nanowire networks 120 are formed on the mastermold forming substrate 110 (S101) (refer to (I) and (II) of
The nanowire networks 120 can be formed through an electrospinning process, for example, and the process of forming the networks is not limited thereto. In a case of using the electrospinning process, the nanowire networks 120 can be formed through electrospinning of a solution onto the mastermold forming substrate 110, the solution containing a material which forms the nanowire networks 120. Various polymer materials can be used as the material that forms the nanowire networks 120, and examples of the materials can include poly(methyl methacrylate) (PMMA), poly(N-vinylpyrrolidone) (PVP), and the like. For reference, actual nanowire networks 120 form a chaotically structured nanowire shape; however,
In a state where the nanowire networks 120 are formed on the mastermold forming substrate 110, anisotropic dry etching is performed on a front surface of the mastermold forming substrate 110 (refer to (II) of
Through the process, fabrication of the mastermold having the relief-patterned region with nanowire networks 120 is ended (S102) (refer to (III) of
In the state where fabrication of the mastermold having the relief pattern-shaped ‘conductive nanonetwork replicating region 110a’ is completed, the process of coating the mastermold with the conductive material 150 is performed.
As described above, example embodiments of the present disclosure employs a method of coating the mastermold with the conductive material 150 and replicating the conductive material onto an application target substrate 10 to form the conductive nanonetworks 150a. Hence, in order to smoothly replicate the conductive material 150, the conductive material 150 has to be easily attached and detached from the mastermold during replication of the conductive material 150. In this respect, before the mastermold is coated with the conductive material 150, the mastermold has to be hydrophobic.
In order for hydrophobization of the mastermold, a hydrophilic thin film layer 130 having a very thin thickness is formed on a front surface of the mastermold having the ‘conductive nanonetwork replicating region 110a’ (S103). Next, a hydrophobic surface treatment layer 140 is formed on the hydrophilic thin film layer 130 (S103) (refer to (IV) and (V) of
On the other hand, the hydrophilic thin film layer 130 fulfills a function of inhibiting the hydrophobic surface treatment layer 140 from being replicated together with the conductive material 150 during replication of the conductive material 150. When an amphiphilic material containing the above-described material is used as the hydrophobic surface treatment layer 140, the hydrophobic surface treatment layer has both a hydrophilic group and a hydrophobic group, and thus contact or bond between the hydrophilic group and the conductive material 150 has to be inhibited. In this respect, the hydrophilic thin film layer 130 is provided between the mastermold and the hydrophobic surface treatment layer 140 so as to induce the hydrophilic group of the hydrophobic surface treatment layer 140 to be bonded to the hydrophilic thin film layer 130. In this manner, the hydrophilic group of the hydrophobic surface treatment layer 140 and the hydrophilic thin film layer 130 are bonded together, and the hydrophobic group of the hydrophobic surface treatment layer 140 is in contact with the conductive material 150. Hence, only the conductive material 150 is replicated to the application target substrate 10 during the replication of the conductive material 150, and the hydrophobic surface treatment layer 140 is not to be replicated to the application target substrate 10. The hydrophilic thin film layer 130 can be formed by a ZnO layer but is not limited thereto.
In a state where the hydrophilic thin film layer 130 and the hydrophobic surface treatment layer 140 are sequentially formed on the mastermold, the hydrophobic surface treatment layer 140 is coated with the conductive material 150 (S104) (refer to (VI) of
In a state where the mastermold is coated with the conductive material 150, the application target substrate 10 is prepared, and the mastermold coated with the conductive material 150 is stamped on the application target substrate 10 such that the conductive nanonetworks 150a are replicated onto the application target substrate 10 (S105) (refer to (VII) and (VIII) of
On the other hand, stamping of the mastermold coated with the conductive material 150 on the application target substrate 10 and replicating the conductive nanonetworks 150a onto the application target substrate 10 can be performed through various methods. Examples of the methods can include a method of causing the mastermold and the application target substrate 10 to be in press contact with each other between two rollers such that the conductive nanonetworks 150a are replicated or a method of stamping the mastermold on the application target substrate 10 as engravings are printed.
When the conductive nanonetworks 150a are completely formed through replication, the conductive material 150 remains as a coating material on the mastermold except for the conductive nanonetwork replicating region 110a of the mastermold, and the remaining conductive material 150 can be collected and reused.
The conductive nanonetworks 150a can be formed on the application target substrate 10 by sequentially performing the process of fabricating the mastermold, the process of coating the mastermold with the conductive material 150, and the process of replicating conductive nanonetworks 150a onto the application target substrate 10.
As described above, the conductive nanonetworks are formed through a method of forming the conductive nanonetwork replicating region patterned in relief on the mastermold, coating the conductive nanonetwork replicating region patterned in relief with the conductive material, and then replicating the conductive material onto the application target substrate. Hence, a property of surface roughness of the conductive nanonetworks can be improved, and the problem of the ‘contact resistance between nanowires’ in the related art can be fundamentally excluded such that the electrical properties and the optical properties of an element, to which the conductive nanonetworks are applied, can be improved.
Additionally, in example embodiments of the present disclosure, the electrical properties and the optical properties of the conductive nanonetworks are controllable by adjusting a geometric shape such as a diameter or a size of the nanowire networks. As described above, since the conductive nanonetwork replicating region of the mastermold corresponds to the region patterned in relief which is the region with the nanowire networks, and the conductive nanonetworks have a shape corresponding to the nanowire networks, a change in geometric shape of the nanowire networks means a change in geometric shape of the conductive nanonetworks. Since the change in geometric shape of the conductive nanonetworks is directly associated with the electrical properties and the optical properties, the electrical properties and the optical properties of the conductive nanonetworks can be controlled by adjusting the geometric shape such as a diameter or a size of the nanowire networks.
The geometric shape of the nanowire networks is changed by adjusting a material or an electrospinning process condition of the nanowire networks. As described above, examples of materials of the nanowire networks include poly(methyl methacrylate) (PMMA), poly(N-vinylpyrrolidone) (PVP), and the like A diameter, a size, and a structure of the nanowire networks are changed depending on a type of material or a mixing ratio of materials of the nanowire networks. In addition, the diameter, the size, and the structure of the nanowire networks are changed depending on a diameter of a needle, through which spinning of a solution is performed during electrospinning of nanowire networks, or a voltage applied to the needle. For reference, an electrospinning device is configured to include a needle through which spinning of a solution is performed and a high-voltage generator that applies a voltage to the needle. Further, an alignment direction of the nanowire networks can also be controlled through disposition of electrodes of the electrospinning device.
In this manner, since the geometric shape of the nanowire networks corresponds to a geometric shape of the conductive nanonetworks, the electrical properties and the optical properties of the conductive nanonetworks can be controlled by inducing a change in geometric shape of the nanowire networks through adjustment of the material of the nanowire networks and the electrospinning process condition.
In addition to control of the electrical properties and the optical properties of the conductive nanonetworks through adjustment of the material and the electrospinning process condition of the nanowire networks, the electrical properties and the optical properties of the conductive nanonetworks can be controlled through adjustment of a thickness of the conductive material with which the conductive nanonetwork replicating region of the mastermold are coated.
The fabrication method of conductive nanonetworks using a mastermold according to the example embodiments of the present disclosure is described as above. Hereinafter, the example embodiments of the present disclosure will be more specifically described with experimental examples.
A poly(methyl methacrylate) (PMMA) solution having a concentration of 0.06 g/mL is prepared by dissolving 0.36 g of PMMA in a solution obtained by mixing N,N-dimethylformamide and acetone by a volume ratio of 2 to 1, and then electrospinning of PMMA on a silicon substrate is performed. As electrospinning conditions, a syringe tip is set to 23G, a voltage is set to 9.8 kV, a distance between a substrate and a needle is set to 16 cm, and a flow rate is set to 0.6 mL/hr.
Inductively coupled plasma-reactive ion etching (ICP-RIE) is performed on the silicon substrate coated with PMMA, and a region which is not coated with PMMA are etched. Next, PMMA is removed.
After ZnO is formed on the silicon substrate patterned in relief by a sol-gel process or a sputtering process, 1H,1H,2H,2H-perfluorodecyl-trichlorosilane (FDTS) is applied on ZnO. Next, FDTS is coated with Ag at a thickness of 50 nm, 100 nm, or 200 nm. Replication of Ag on the silicon substrate onto a PET substrate is performed by using a gravure printing method.
Ag conductive nanonetworks are formed using a mastermold having a structure of silicon substrate/Zno/FDTS patterned in relief which is fabricated in accordance with Experimental Example 1, and properties of optical transmittance of the formed Ag conductive nanonetworks are compared with those of ITO.
With reference to
In addition, properties of sheet resistance and optical transmittance depending on a thickness of the Ag conductive nanonetworks fabricated in accordance with Experimental Example 1 are checked, and the properties are compared with those of the conductive nanofilm, that is, Ag nanowires (AgNW), Cu nanothrough, graphene, and nanonetworks, fabricated in accordance with the related art. Here, AgNW is fabricated by coating a substrate with an AgNW dispersed solution through spin-coating or spray-coating, Cu nanothrough is fabricated by a method of depositing metal (Cu) on polymer nanowire networks formed through electrospinning and of replicating metal deposited nanowire networks onto a target substrate, and a graphene nanoelectrode is fabricated by a method of replicating graphene synthesized through CVD onto a substrate by using an adhesive material.
With reference to
In addition, as a result of checking, with figure of merit (FoM) values, the properties of the optical transmittance and direct current conductance of the Ag conductive nanonetworks fabricated in accordance with the example and those of the conductive nanofilm according to the related art, the Ag conductive nanonetworks may be observed to have higher performance than that of the conductive nanofilm of the related art. For reference, FoM (=σDC/σOp, σDC: direct current conductivity, and σOp: optical conductivity) is, as a performance evaluating index of the nanoelectrode, an index for complex evaluation of the optical transmittance property and the direct current conductance property which are in a trade-off relationship.
The electric resistance depending on time and temperature is observed, the electric resistance being properties of the Ag conductive nanonetworks fabricated in accordance with Experimental Example 1 and AgNW fabricated in accordance with the related art.
With reference to
In addition, with reference to
The fabrication method of conductive nanonetworks using a mastermold according to the example embodiments of the present disclosure has the following effects.
According to the fabrication method, the conductive nanonetworks are formed by coating the conductive nanonetwork replicating region patterned in relief on the mastermold with the conductive material and replicating the conductive material to the application target substrate, and thus a nanonetwork-shaped conductive nanofilm may be easily fabricated and may be applied as a conductive nanofilm having a large area by increasing a size of the mastermold. Besides, the conductive nanofilm may have better electric and optical properties than a nanonetwork-shaped conductive nanofilm in the related art, and the electric and optical properties may be controlled by changing a geometric shape of the conductive nanonetworks.
While the present disclosure has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2020-0168464 | Dec 2020 | KR | national |
| 10-2021-0151155 | Nov 2021 | KR | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 10831233 | Dodds et al. | Nov 2020 | B2 |
| 20120325545 | Higashitani | Dec 2012 | A1 |
| 20220181047 | Lee | Jun 2022 | A1 |
| Number | Date | Country |
|---|---|---|
| 2594941 | May 2020 | GB |
| 10-2006-0018466 | Mar 2006 | KR |
| 101011447 | Jul 2010 | KR |
| 10-2011-0138447 | Dec 2011 | KR |
| 10-2015-0116063 | Oct 2015 | KR |
| 10-2017-0123504 | Nov 2017 | KR |
| Entry |
|---|
| English Translation of Korean Office Action from Korean Application No. 10-2021-0151155, dated Sep. 5, 2023, 4 pages. |
| Number | Date | Country | |
|---|---|---|---|
| 20220181048 A1 | Jun 2022 | US |
