The present application claims priority to Korean patent application number 10-2015-0176187 filed on Dec. 10, 2015, the entire disclosure of which is incorporated herein in its entirety by reference.
1. Field
An aspect of the present disclosure relates to an electronic device and a method of fabricating the same, and more particularly, to a stretchable electronic device using a conductive fiber pattern and a method of fabricating the same.
2. Description of the Related Art
Fiber-based electronic devices can be freely pulled or bent. Particularly, fibers have various advantages such as elongation, weaving feasibility, wide surface areas, various surface processing and easy composition of composite materials, and thus it will be highly likely that the fabrics will be applied to electronic devices. However, technologies related to this still stay at conceptual levels.
A majority of fibers are composed of polymer materials, and most of the polymer materials are materials having low electrical conductivities. Therefore, the fibers are typically used as electric insulators, and it is inappropriate that the fibers are used as conductive materials.
Conventionally, in order to overcome such a problem, a metallic material having an electrically conductive property was added to a polymer material constituting a fiber, thereby fabricating a fiber pattern having an electrical conductivity.
However, a conductive fiber or fabric fabricated in such a manner has excellent conductivity, and, on the other hands, the mechanical stretchability of the conductive fiber or fabric is weak. Therefore, it is difficult for the fiber or fabric to be directly used in electronic devices or to be used as a connection member for connecting electronic devices to each other.
Embodiments provide a stretchable electronic device using a conductive fiber pattern having excellent conductivity and stretchability, and a method of fabricating the stretchable electronic device.
According to an aspect of the present disclosure, there is provided a stretchable electronic device including: a flexible substrate; a conductive fiber pattern formed on the flexible substrate, the conductive fiber pattern having a repetitive circular structure; and a graphene material attached to the conductive fiber pattern.
According to an aspect of the present disclosure, there is provided a method of fabricating a stretchable electronic device, the method including: preparing a mixed solution in which a polymer material and a metallic material are dispersed; electrically spinning the mixed solution, thereby forming a conductive fiber pattern having a repetitive circular structure; annealing the conductive fiber pattern; and dipping the conductive fiber pattern into a graphene dispersion solution, thereby attaching a graphene material to a surface of the conductive fiber pattern.
Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the example embodiments to those skilled in the art.
In the drawing figures, dimensions may be exaggerated for clarity of illustration. It will be understood that when an element is referred to as being “between” two elements, it can be the only element between the two elements, or one or more intervening elements may also be present. Like reference numerals refer to like elements throughout.
Hereinafter, exemplary embodiments of the present disclosure will be described. In the drawings, the thicknesses and the intervals of elements are exaggerated for convenience of illustration, and may be exaggerated compared to an actual physical thickness. In describing the present disclosure, a publicly known configuration irrelevant to the principal point of the present disclosure may be omitted. It should note that in giving reference numerals to elements of each drawing, like reference numerals refer to like elements even though like elements are shown in different drawings.
Referring to
The substrate 10 may be a flexible substrate such as a rubber substrate. The electrode pattern 11 is formed of a conductive layer such as a metal, and may include a plurality of electrode layers spaced apart from each other at a predetermined distance. For example, the electrode pattern 11 may be a sensing electrode of a sensor. The conductive fiber pattern 12 is electrically connected to the electrode pattern 11, and may have a tangled structure. Here, the tangled structure may be a structure in which an amorphous overlapping structure such as a net, a web, or a skein is repeated, or may be a structure in which a circular overlapping structure such as a spring structure or a spiral structure is repeated.
According to the structure described above, the plurality of electrode layers included in the electrode pattern 11 are electrically connected to each other by the conductive fiber pattern 12. Even when the distance between the plurality of electrode layers is increased as the substrate 10 is stretched or when the substrate 10 is warped as the substrate is stretched, the conductive fiber pattern 12 can be stretched in a state in which the plurality of electrode layers are electrically connected to each other by the conductive fiber pattern 12 because of its structural characteristic. That is, if the substrate 10 is stretched, the overlapping structure of the conductive fiber pattern 12 is unfolded, and the connection state of the conductive fiber pattern 12 is maintained as it is. Thus, the electrical connection of the plurality of electrode layers can also be maintained.
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By applying the above-described structure, it is possible to implement a hybrid structure in which its lower portion is filled with the nanowire 21 and a conductive polymer, and a graphene material for biochemical material detection is attached to its upper portion. Here, the nanowire 21 at the lower portion of the hybrid structure may be a sensing electrode, and a biochemical detection device (sensor) may be fabricated using the sensing electrode. Thus, it is possible to fabricate stretchable detection device of which electrical characteristics are not changed even though it is warped or stretched.
For reference, in these figures, the mixed graphene flakes are called as the first graphene materials 22A and the second graphene materials 22B for convenience of description so as to distinguish the graphene flakes from each other, but the present disclosure is not limited thereto. In addition, the silver wire may have the above-described circular overlapping structure.
An ES process is a technique of spinning a polymer solution or polymer melt using an electrostatic force, thereby forming a fine pattern having a line width of a few tens to a few hundreds of nanometers. In the ES process, the fine pattern is spun using an electrostatic force generated by a high voltage of a few kV or more. Hereinafter, a method of fabricating a fiber pattern using ES with reference to
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First, a polymer material and a conductive metallic material are mixed together, thereby preparing a mixed solution. Here, the polymer material may be any one selected from the group consisting of polyvinyl alcohol (PVA), polyurethane (PU), polyimide (PI), polyethylene oxide (PEO), polyvinylpyrrolidone (PVP), polystyrene (PS), and polyacrylonitrile (PAN). The metallic material may have the form of a metal wire or metal flake. Also, the metallic material may be any one selected from the group consisting of silver (Ag), copper (Cu), gold (Au), platinum (Pt), molybdenum (Mo), tungsten (W), nickel (Ni), and chromium (Cr).
Subsequently, the mixed solution stored in the syringe is extruded in the form of a droplet from the nozzle 31. If a voltage applied in the vertical direction between the nozzle 31 and the substrate 40 becomes greater than the surface tension of the droplet, a conductive fiber pattern 50 is spun. At this time, the fiber pattern 50 is spun in a linear jet flow. If the force by which the droplet is to spread in the horizontal direction is equilibrated with the voltage applied in the vertical direction, the conductive fiber pattern 50 having a repetitive circular structure such as a vortex shape, a spiral shape, or a spring shape is spun. Subsequently, the conductive fiber pattern 50 is annealed. Accordingly, a polymer component included in the conductive fiber pattern 50 can be removed.
Here, the radius of curvature of the conductive fiber pattern 50 injected in a circular shape may be adjusted depending on a distance between the nozzle 31 and the substrate 40. When the distance between the nozzle 31 and the substrate 40 is relatively distant as shown in
As described above, the distance between the nozzle 31 and the substrate 40 is adjusted to 5 nm or less, a fiber pattern having a repetitive circular structure can be fabricated at a specific position. Further, if the above-described method is applied to the fabrication of an electronic device, an electrode pattern is previously formed on the substrate 40, and a spring-shaped fiber pattern is formed on only the electrode pattern, so that the electronic device can be driven by allowing current to be selectively introduced into only an electrode portion at which the fiber pattern is formed.
In addition, the magnitude of the applied voltage, the viscosity of the solution, the moving speeds of the nozzle 31 in X, Y, and Z directions, the size of a hole of the nozzle 31, through which the solution is discharged, and the like may be adjusted, thereby controlling the form and line width of the conductive fiber pattern 50. Particularly, the line width of the conductive fiber pattern 50 may be controlled to be within a few to a few tens of μm. For example, when the polymer solution has a viscosity of 10 to 50 cps, a fiber pattern having the form of a third-dimensional mat is formed on the surface of the substrate 40 as shown in
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For reference, although not shown in these figures, the conductive fiber pattern 80 may be annealed. In addition, the conductive fiber pattern 80 is dipped into a graphene dispersion solution, thereby attaching a graphene material to the conductive fiber pattern 80. For example, after the conductive fiber pattern 80 formed using the ES is annealed, the conductive fiber pattern 80 is transferred onto the flexible substrate 90, and a graphene material may be attached to the conductive fiber pattern 80 transferred onto the flexible substrate 90.
According to the above-described method, it is possible to fabricate an inter-connection electrode structure that can be freely bent or stretched, and a stretchable electronic device can be fabricated using the inter-connection electrode structure. Particularly, since the graphene material has a detection characteristic with respect to a biochemical material, the conductive fiber pattern 80 and the graphene material are formed on a flexible substrate having a sensing electrode pattern formed thereon, so that it is possible to fabricate a stretchable biochemical sensor having a hybrid structure with a conductive metal-fiber.
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According to the present disclosure, a conductive fiber pattern having a spring structure can be formed using the NFES. The conductive fiber pattern having the spring structure can be freely bent or stretched. Although the shape of the conductive fiber pattern is changed, a conductive fiber is not broken, and can maintain its unique characteristic. Accordingly, a stretchable electronic device can be fabricated using the conductive fiber pattern. For example, it is possible to fabricate an inter-connection electrode structure or an attachable flexible electronic device attached to a surface having a certain curvature, such as a helmet or a wrist. In addition, it is possible to fabricate an attachable flexible electronic device attached to an area in which the distance between two electrodes is varied, such as when an arm is folded or unfolded.
Further, a conductive fiber pattern is dipped into a solution in which graphene is uniformly dispersed, so that a graphene material can be uniformly attached on the surface of the conductive fiber pattern. Accordingly, the graphene material having a detection characteristic with respect to a biochemical material is attached to the conductive fiber pattern, so that it is possible to fabricate a hybrid structure of a conductive fiber and graphene. Also, it is possible to fabricate an electronic device such as a biochemical sensor using the hybrid structure
Example embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. In some instances, as would be apparent to one of ordinary skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise specifically indicated. Accordingly, it will be understood by those of skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present disclosure as set forth in the following claims.
Number | Date | Country | Kind |
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10-2015-0176187 | Dec 2015 | KR | national |