KR102147276B1 - Manufacturing method of suspended nanowire using MEMS platform and electrospinning - Google Patents

Abstract

The present invention relates to a method of manufacturing a suspended nanowire using a MEMS platform and electrospinning, comprising: forming a nano-level polymer wire by electrospinning a polymer solution on a MEMS platform having a microgap; Depositing a nanowire material on the nanoscale polymer wire; Forming a nanowire by removing the nano-grade polymer wire with a solvent; And forming a nanowire by drying the solvent to aggregate the plurality of nanowires. In the method of manufacturing a suspended nanowire according to the present invention, the position at which the nanowire is formed can be adjusted by using the surface tension of the solvent generated in the step of drying the solvent. In addition, in the method of manufacturing a suspended nanowire according to the present invention, since the entire process is performed at a low temperature, not only a nanowire can be formed on a substrate that should not be applied to a high temperature, but also a high temperature is not applied to the nanowire material. Therefore, it is possible to form nanowires from a wider variety of materials, and the entire process is a batch process to reduce manufacturing cost.

Description

Manufacturing method of suspended nanowire using MEMS platform and electrospinning {Manufacturing method of suspended nanowire using MEMS platform and electrospinning}

The present invention relates to a method of manufacturing a nanowire using a MEMS platform and an electrospinning method, and more particularly, to form a nano-level polymer wire by electrospinning a polymer solution on the MEMS platform, and depositing a nanowire material on the polymer wire. After removing the polymer wire through a solvent and using the surface tension generated in the process of drying the solvent, the present invention relates to a method of manufacturing a nanowire capable of controlling the position at which the nanowire is formed.

Nanowires are widely used as gas sensors, biosensors, and catalysts because of their high surface area and unique physical properties. In particular, a gas sensor using a suspended nanowire has a higher surface area to volume ratio, so it has better sensitivity than a gas sensor using a general nanowire.

In addition, since the shape and number of nanowires directly affect the performance of a device such as a gas sensor, it is necessary to control the position where the nanowires are formed and the number of formed nanowires.

Conventional nanowire fabrication methods include vapor-liquid-solid (VLS) growth, chemical vapor deposition (CVD), sol-gel processing, laser pyrolysis, atomic or molecular Condensation (atomic or molecular condensation), layer-by-layer self assembly (layer-by-layer self assembly), molecular self assembly (molecular self assembly), etc., as top-down techniques X-ray lithographt, electron beam lithography (e-beam lithography), ion-beam lithography, printing and imprinting.

Since these conventional methods are planar techniques, it is difficult to make three-dimensional nanowires (suspended nanowires, etc.) having a desired shape, high-temperature processes cost a lot, and materials of nanowires that can be manufactured are limited.

On the other hand, as a more recent method of manufacturing nanowires, there is a method of manufacturing nanowires using electrospinning, which is a method of manufacturing metal oxide nanowires using sintering or calcinations, and other materials in a polymer template. There is a method of vapor deposition.

The conventional nanowire fabrication method using electrospinning allows the fabrication of suspended nanowires, but it is impossible to control the position where the nanowires are formed, and the material of the nanowires is limited.

Hollow ZnO Nanofibers Fabricated Using Electrospun Polymer Templates and Their Electronic Transport Properties, ACS Nano, Vol. 3, pp. 2623-2631, 2009.

In the present invention, in order to more effectively solve the problems of the prior art, not only can the suspension type nanowires be selectively manufactured, but also the suspension type nanowires capable of adjusting the thickness of the formed nanowires while performing the entire process at a low temperature. To provide a method of manufacturing a wire. In addition, the method of manufacturing a suspended nanowire of the present invention can form a nanowire from a variety of materials.

In an embodiment of the present invention, forming a nano-level polymer wire by electrospinning a polymer solution on a MEMS platform having a microgap; Depositing a nanowire material on the nanoscale polymer wire; Forming a nanowire by removing the nano-grade polymer wire with a solvent; And drying the solvent to aggregate the nanowires to form nanowires.

In the present invention, the term "nanowire" refers to a single-stranded metal wire of nanoscale, and "nanowire" refers to a state in which such a plurality of nanowires are aggregated to form a single nanowire.

The MEMS platform is preferably formed by having a silicon electrode spaced apart from each other with a microgap, and the diameter of the nano-level polymer wire may be 100 to 1000 nm.

In addition, the polymer solution is a solution prepared by dissolving a polymer capable of forming nano-level polymer wires by electrospinning in a solvent, for example, polyethylene oxide, polyurethane, polyethylene, polypropylene, polystyrene, polyvinyl chloride, and It may be a polymer solution containing at least one or more from the group consisting of polybutadiene.

The nanowire material is a material capable of evaporation, for example, silver (Ag), aluminum (Al), gold (Au), palladium (Pd), copper (Cu), iron (Fe), nickel (Ni), chromium (Cr), magnesium (Mg), manganese (Mn), molybdenum (Mo), phosphorus (P), lead (Pb), platinum (Pt), ruthenium (Ru), titanium (Ti), tungsten (W), zinc (Zn), and may contain at least one or more from the group consisting of oxides thereof.

As the solvent, a solvent capable of removing the nano-level polymer wire and not damaging the deposited nanowire material and the MEMS platform may be used.For example, the solvent may be a chloroform solution, acetone solution, or dimethyl foam. It may be amide (dimethylformamide) or purified water.

The diameter of the formed nanowires may be controlled by adjusting the conditions of the electrospinning (electrospinning time, electrospinning voltage, electrospinning distance, electrospinning solution).

In addition, the step of depositing the nanowire material may be performed by e-beam evaporation, thermal evaporation, or sputtering, and depositing the nanowire material to a thickness of 10 to 30 nm. It is desirable to make it.

Drying the solvent to aggregate the nanowires to form the nanowires may be performed at room temperature.

In the method of manufacturing a suspended nanowire according to the present invention, the position at which the nanowire is formed can be adjusted by using the surface tension of the solvent generated in the step of drying the solvent.

In addition, the thickness of the nanowire can be adjusted using electrospinning, and the nanowire can be formed from various materials.

In addition, in the method of manufacturing a suspended nanowire according to the present invention, since the entire process is performed at a low temperature, not only a nanowire can be formed on a substrate that should not be applied to a high temperature, but also a high temperature is not applied to the nanowire material. Therefore, nanowires can be formed from more diverse materials.

In addition, the manufacturing method of the suspended nanowire according to the present invention can be made in a batch process to reduce manufacturing cost.

1 schematically shows a method of manufacturing a suspended nanowire according to an embodiment of the present invention.
2 is a side view of a MEMS platform according to an embodiment of the present invention.
3 is a front view of a MEMS platform according to an embodiment of the present invention.
4 is a schematic diagram showing a principle of forming a nanowire according to an embodiment of the present invention.
5 is an image of an SEM observation of a nanowire according to an embodiment of the present invention.
6 is an image of an SEM observation of nanowires manufactured by varying the electrospinning time.

Hereinafter, the present invention will be described in more detail with reference to embodiments of the present invention and drawings. These examples are only illustratively presented to explain the present invention in more detail, and it will be apparent to those of ordinary skill in the art that the scope of the present invention is not limited by these examples. will be.

In addition, it should be noted that terms or words used in the present specification and claims should not be interpreted as being limited to a conventional or dictionary meaning, but should be interpreted as meanings and concepts consistent with the technical idea of the present invention.

In order to clearly describe the invention proposed in the drawings, parts not related to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification. And when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components unless specifically stated to the contrary.

In the present invention, the term "nanowire" refers to a single-stranded metal wire of nanoscale, and "nanowire" refers to a state in which such a plurality of nanowires are aggregated to form a single nanowire.

1 is a step-by-step view showing a method of manufacturing a suspended nanowire according to an embodiment of the present invention.

Referring to FIG. 1, a method of manufacturing a suspended nanowire according to an embodiment of the present invention includes the steps of forming a nano-level polymer wire by electrospinning a polymer solution on a MEMS platform having a microgap (S100); Depositing a nanowire material on a nano-level polymer wire (S200); Forming a nanowire by removing the nano-grade polymer wire with a solvent (S300); And forming a nanowire by drying the solvent to aggregate a plurality of nanowires (S400). The method of manufacturing a suspended nanowire of the present invention can control the position where the nanowire is formed and the diameter of the nanowire. In addition, since the entire process is performed at a low temperature, nanowires can be formed not only on substrates that should not be subjected to high temperatures, but also nanowires can be formed from a wider variety of materials because high temperatures are not applied to nanowire materials. . Further, the manufacturing method of the suspended nanowire according to the present invention can be made in a batch process to reduce manufacturing cost.

The step of electrospinning a polymer solution on a MEMS platform having a microgap to form a nano-level polymer wire (S100) is a step of electrospinning the polymer solution to form a plurality of nano-class polymer wires on the MEMS platform, wherein the microgap is formed. Through this, a nano-level polymer wire is formed in a suspended form.

The MEMS platform is preferably formed so that the silicon electrode 110 is spaced apart from each other with a micro gap 130 of 3 to 15 μm, as shown in FIG. 2. The silicon electrode 110 is manufactured using a silicon on insulator (SOI) wafer, and may have a structure in which a SiO ₂ insulating layer 170 is formed between the silicon layers 150.

In addition, as shown in FIG. 3, the silicon electrode 110 has a shape of a triangular tip protruding sharply, and it is preferable that the protruding portions are positioned to face each other.

The surface of the silicon electrode 110 may be partially treated with hydrophobicity. In this way, when the surface of the silicon electrode 110 becomes partially hydrophobic, the position at which the solvent is condensed in the step (S400) of forming a nanowire by drying a solvent to be described later to aggregate the nanowires is determined. It can be adjusted (solvent condenses onto the non-hydrophobic surface), so the formation position of the nanowires can be controlled.

The polymer solution is not particularly limited as long as it is a polymer solution capable of forming nano-class polymer wires by electrospinning and removing nano-class polymer wires with a solvent. For example, the polymer solution preferably contains at least one or more from the group consisting of polyethylene oxide, polyurethane, polyethylene, polypropylene, polystyrene, polyvinyl chloride and polybutadiene, and more preferably polyethylene oxide. I can.

The diameter of the formed nanowires may be adjusted by adjusting the conditions of the electrospinning (electrospinning time, electrospinning voltage, electrospinning distance, electrospinning solution) . Specifically, as the electrospinning time increases, the number of nano-level polymer wires to be formed increases, and the number of nano-wires to be formed increases, and accordingly, the number of nanowires to be aggregated increases, so that the resulting nanowires become thicker. In addition, when the diameter of the nano-grade polymer wire formed by controlling the electrospinning conditions increases, the direct hit of the finally generated nanowire increases.

The electrospinning may be performed through a general electrospinning method. The general principle of electrospinning is that the polymer solution is radiated on the MEMS platform through the ejection nozzle of the syringe to form nano-level polymer wires. Two collector electrodes can be used to align the nano-class polymer wires. At this time, power is applied to the syringe through a high-voltage power supply. Through this process, polymer wires of almost constant thickness can be obtained on the MEMS platform. This electrospinning time may be about 2 to 10 seconds.

The diameter of the nano-grade polymer wire is not particularly limited, but is preferably about 100 to 1000 nm in order to facilitate the formation of the nanowires described later and facilitate aggregation of the formed nanowires.

In the step of depositing a nanowire material on a nano-level polymer wire (S200), the nanowire material is not particularly limited as long as it is a material capable of evaporation. For example, the nanowire material is silver (Ag), aluminum (Al), gold (Au), palladium (Pd), copper (Cu), iron (Fe), nickel (Ni), chromium (Cr), and magnesium. (Mg), manganese (Mn), molybdenum (Mo), phosphorus (P), lead (Pb), platinum (Pt), ruthenium (Ru), titanium (Ti), tungsten (W), zinc (Zn) and these It may include at least one or more of the group consisting of oxides of.

Such a nanowire material may be deposited on a nanoscale polymer wire through evaporation. As such evaporation, e-beam evaporation, thermal evaporation, sputtering, or the like may be used.

The deposition of the nanowire material may be performed by being slanted at a predetermined angle, as shown in FIG. 1. The predetermined angle is preferably 35 to 55°, and more preferably 45°.

When the nanowire material is slanted and deposited, nanowires having a thinner diameter can be created, and the nanowire material is well attached to the MEMS platform, so that the nano-grade polymer wire is used as a solvent to be described later. In the step of removing and forming a nanowire (S300), the nanowire material is not removed like a polymer wire, and a nanowire is easily formed.

The thickness of the nanowire material deposited in the step (S200) of depositing the nanowire material on the nano-level polymer wire is preferably about 10 to 30 nm, more preferably 10 to 20 nm. If the thickness of the deposited nanowire material is less than 10 nm, it is difficult to form a nanowire because it is easily broken in the process of removing the nano-level polymer wire, and if the thickness exceeds 30 nm, the nanowire, which will be described later, does not clump together.

In the step S300 of forming a nanowire by removing the nanowire material with a solvent, the MEMS platform on which the nanowire material is deposited is immersed in a solvent to remove the nanoclass polymer wire formed on the MEMS platform. When the nano-class polymer wire is removed, only the nanowire material deposited on the nano-class polymer wire remains, thereby forming a plurality of nanowires.

As such a solvent, any solvent that can remove the nano-grade polymer wire and does not damage the deposited nanowire material and the MEMS platform may be used without any particular limitation. For example, as the solvent, a chloroform solution, acetone solution, dimethylformamide, or purified water may be used.

In the step of forming a nanowire by drying a solvent to bundle a plurality of nanowires (S400), a plurality of nanowires are agglomerated into one by the surface tension of the solvent generated while the solvent is dried. Is the step of forming.

4 is a conceptual diagram showing the principle that a plurality of nanowires are united into one by the surface tension of a solvent. When described with reference to this, surface tension is generated in the process of drying the solvent, so that the solvent is evaporated while condensing to a predetermined position. At this time, as the plurality of nanowires are pulled to a predetermined position where the solvent is condensed by surface tension, the nanowires are united into one to form nanowires.

By controlling the location at which the solvent is condensed during the drying process, the location at which the nanowires are formed can be controlled. Specifically, in the case of using the MEMS platform in the shape of a sharply protruding tip as shown in FIG. 4(b), the solvent is condensed and evaporated at the tip of the sharply protruding tip during the drying process, and accordingly, A nanowire is formed at the end of the protruding tip.

This drying process may be performed at room temperature (about 15 to 25°C).

If necessary, before the step (S400) of forming nanowires by drying the solvent to aggregate the nanowires (S400), a step of replacing the nanowires with a different solvent having a different force to aggregate the nanowires may be performed in the process of drying the solvent. Nanowires do not aggregate when the force to aggregate the nanowires is low compared to the physical properties and thickness of the nanowires, and when the solvent has a higher force to aggregate the nanowires compared to the physical properties and thickness of the nanowires, the nanowires aggregate. Since it can break in the process, a suitable level of cohesive force can be replaced by a solvent.

For example, after using DI water to remove polyethylene oxide (PEO) polymer wires, isopropyl alcohol (IPA) may be used as a solvent for coagulating nanowires.

[ Example One]

Nanowires were manufactured through the method of manufacturing the nanowires of the present invention described above.

A MEMS platform having a structure in which silicon electrodes having flat surfaces are spaced apart from each other at intervals of 10 μm was fabricated. The silicon electrode was fabricated using an SOI (Silicon on Insulator) wafer. A polyethylene oxide (PEO) solution was electrospun on the MEMS platform for 5 seconds to form a plurality of nano-level PEO polymer wires. The nozzle used at this time was a 26 gauge needle, and a voltage of 9kV was applied to the syringe for electrospinning.

Palladium (Pd) was deposited to a thickness of 10 nm on the MEMS platform on which the PEO polymer line was formed by e-beam evaporation. The deposition of palladium (Pd) was performed by slanting at an angle of 45°.

Thereafter, the MEMS platform was immersed in purified water (DI water) to remove the PEO polymer wire, and purified water (DI water) was replaced with isopropyl alcohol (IPA). Next, isopropyl alcohol (IPA) was dried at room temperature (25°C) to prepare a nanowire.

[ Example 2]

Nanowires were prepared in the same manner as in Example 1, but nanowires were prepared using a MEMS platform in which silicon electrodes in the shape of sharp protruding tips were spaced apart from each other at intervals of 10 μm.

[ Experimental example One: Nano wire Creation Confirm]

In order to confirm the generation of nanowires, Examples 1 and 2 were observed with a scanning electron microscope (SEM) and the results are shown in FIG. 5 (the results of Example 1 are shown in FIG. 5(a), The results of Example 2 are shown in Fig. 5(b)).

As can be seen in Figure 5, it was confirmed that the nanowires were formed by uniting the nanowires into one due to the surface tension generated in the evaporation process of isopropyl alcohol (IPA). In particular, through FIG. 5(b), it was confirmed that the position at which the nanowires are generated can be controlled (nanowires are generated at the tip of the mems platform's sharply protruding tip).

[ Experimental example 2: according to the electrospinning time Nano wire Adjust thickness]

In order to check the thickness of the nanowires finally formed according to the electrospinning time, nanowires were prepared in the same manner as in Example 2, but the nanowires were prepared with the electrospinning time set to 2 and 5 seconds, respectively, and then injected. Observation with an electron microscope (Scanning Electron Microscope, SEM) and the results are shown in FIG. 6 ((a), (b) and (c) of FIG. 6 are observation results of nanowires manufactured by performing electrospinning for 2 seconds. 6(d), (e) and (f) are observation results of nanowires manufactured by performing electrospinning for 5 seconds).

As can be seen in FIG. 6, it was confirmed that the thickness of the nanowires generated when the electrospinning time was 5 seconds was thicker than when the electrospinning time was 2 seconds. As a result, it was found that the longer the electrospinning time, the thicker the finally generated nanowires, and the thickness of the generated nanowires can be adjusted by controlling the electrospinning time.

100: MEMS platform 110: silicon electrode
130: microgap 150: silicon layer
170: insulating layer

Claims (10)

Electrospinning a polymer solution on a MEMS platform having a microgap to form nano-level polymer wires;
Depositing a nanowire material on the nanoscale polymer wire;
Forming a nanowire by removing the nano-grade polymer wire with a solvent; And
Drying a solvent to aggregate a plurality of nanowires to form nanowires; a method of manufacturing a suspended nanowire comprising.
The method of claim 1,
The MEMS platform is a method of manufacturing a suspended nanowire, wherein silicon electrodes are formed to have a microgap and are spaced apart from each other.
The method of claim 1,
The diameter of the nano-grade polymer wire, characterized in that the 100 ~ 1000nm, the method of manufacturing a suspension type nanowire.
The method of claim 1,
The polymer solution, comprising at least one or more from the group consisting of polyethylene oxide, polyurethane, polyethylene, polypropylene, polystyrene, polyvinyl chloride and polybutadiene, a method of manufacturing a suspended nanowire.
The method of claim 1,
The nanowire material is silver (Ag), aluminum (Al), gold (Au), palladium (Pd), copper (Cu), iron (Fe), nickel (Ni), chromium (Cr), magnesium (Mg) , Manganese (Mn), molybdenum (Mo), phosphorus (P), lead (Pb), platinum (Pt), ruthenium (Ru), titanium (Ti), tungsten (W) and at least from the group consisting of zinc (Zn) A method of manufacturing a suspension type nanowire comprising one or more.
The method of claim 1,
The solvent is a chloroform solution, acetone (acetone) solution, dimethylformamide (dimethylformamide) or purified water, characterized in that, the manufacturing method of the suspension type nanowires.
The method of claim 1,
The step of depositing the nanowire material is characterized in that it is performed by e-beam evaporation, thermal evaporation, or sputtering.A method of manufacturing a suspended nanowire.
The method of claim 1,
The step of depositing the nanowire material, characterized in that depositing the nanowire material to a thickness of 10 ~ 30nm, the method of manufacturing a suspension type nanowire.
The method of claim 1,
The step of forming a nanowire by drying the solvent to aggregate a plurality of nanowires is carried out at room temperature.
Suspension type nanowire manufactured by the manufacturing method according to any one of claims 1 to 9.

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