KR102604229B1 - Electrospinning-based hydrogen-bonded hybrid nanofibrous membrane and pressure sensor and method for manufacturing the same - Google Patents

Abstract

Electrospinning-based hydrogen bonded hybrid nanofiber membrane and pressure sensor and method for manufacturing the same are disclosed. A method of manufacturing a hybrid nanofiber membrane according to an embodiment includes the steps of dispersing 2D nanomaterials in distilled water to generate a precursor solution, adding a hydrophilic polymer using the precursor solution as a solvent, and then adding a hydrophilic polymer to the mixture using a hot plate. A step of creating a hydrophilic polymer-2D nanomaterial gel by stirring, adding an ionic salt to the hydrophilic polymer-2D nanomaterial gel and stirring on a hot plate to create an electrolyte solution, and electrospinning the electrolyte solution to create a 2D nanomaterial. /hydrophilic polymer/ionic salt hybrid nanofiber membrane.

Description

Electrospinning-based hydrogen-bonded hybrid nanofibrous membrane and pressure sensor and method for manufacturing the same}

The present invention relates to a hybrid nanofiber membrane and pressure sensor manufacturing technology using the same.

Nano fiber can be used in various devices and industrial fields to develop new technologies such as controlled drug delivery systems, various sensors, super capacitors, and energy harvesting. Existing hybrid nanofiber manufacturing methods have the problem of being unevenly distributed in the fiber matrix, resulting in a low surface area and easy aggregation.

Existing nanofiber membrane manufacturing methods have the problem of being unevenly dispersed in the fiber matrix, resulting in a low surface area and easy aggregation. This is a typical cause of deterioration of the mechanical and electrical properties of materials.

According to one embodiment, a nanofiber membrane and pressure sensor that significantly improve the sensitivity and linearity range of the sensor, and a method of manufacturing the same are proposed.

A method of manufacturing a hybrid nanofiber membrane according to an embodiment includes the steps of dispersing 2D nanomaterials in distilled water to generate a precursor solution, adding a hydrophilic polymer using the precursor solution as a solvent, and then adding a hydrophilic polymer to the mixture using a hot plate. A step of creating a hydrophilic polymer-2D nanomaterial gel by stirring, adding an ionic salt to the hydrophilic polymer-2D nanomaterial gel and stirring on a hot plate to create an electrolyte solution, and electrospinning the electrolyte solution to create a 2D nanomaterial. /hydrophilic polymer/ionic salt hybrid nanofiber membrane.

The 2D nanomaterial may be any one of MXene, graphene, GO (Graphene Oxide), rGO (Reduced Graphene Oxide), molybdenum disulfide (MoS ₂ ), and black phosphorus.

The hydrophilic polymer may be any one of poly(vinyl alcohol), poly(acrylamide), poly(ethylene glycol), and polyethylene oxide.

Ionic salts include lithium salt (Lithium bis(trifluoromethanesulfonyl)imide), potassium nitrate (KNO3), calcium nitrate (Ca(NO3)2), sodium chloride (NaCl), potassium bromide (KBr), cesium fluoride (CsF), and nitric acid. It may be either magnesium (Mg3N2) or calcium phosphate (Ca3P2).

A method of manufacturing a capacitive pressure sensor according to an embodiment includes the steps of electrospinning a mixture of a hydrophilic polymer, a 2D nanomaterial, and an ionic salt to create a hybrid nanofiber membrane dielectric layer, and focusing on the hybrid nanofiber membrane dielectric layer. It includes the step of creating a capacitive pressure sensor by placing electrodes in a sandwich shape on both sides.

The hybrid nanofiber membrane according to one embodiment is produced by electrospinning a mixture of a hydrophilic polymer, a 2D nanomaterial, and an ionic salt.

A capacitive pressure sensor according to one embodiment has a hybrid nanofiber membrane dielectric layer created by electrospinning a mixture of a hydrophilic polymer, 2D nanomaterial, and ionic salt, and a sandwich shape on both sides centered on the hybrid nanofiber membrane dielectric layer. It includes electrodes disposed as.

In the capacitive pressure sensor, in the initial state where no pressure is applied, the cation-anion pair of the ionic salt attaches to the functional group of the 2D nanomaterial of the hybrid nanofiber membrane through hydrogen bonds (H-bonds), thereby forming the interface between the hybrid nanofiber membrane and the electrode. The formation of an electric double layer can be suppressed and the initial capacitance value can be reduced.

In a capacitive pressure sensor, when pressure is applied, the distance between the two electrodes decreases, increasing the electric field strength and consequently starting the ion pumping process as the force applied to the particles affected by the electric field increases. As a result, the cation-anion pair of the ionic salt is separated on the surface of the 2D nanomaterial, forming an electric double layer of a certain thickness at the interface between the hybrid nanofiber membrane and the electrode.

According to the nanofiber membrane and pressure sensor according to one embodiment, by using a hybrid nanofiber membrane made of a solution of mixing an ionic salt of lithium sulfonamide and MXene in a polyvinyl alcohol elastic matrix as a sensing membrane, hydrogen bonding is induced. The functional layer on the MXene surface suppresses the formation of an electrical double layer (EDL) at the electrode, which can greatly reduce the initial capacitance value.

In addition, when external pressure is applied to a pressure sensor manufactured using a nanofiber membrane, a thick electric double layer is created on the electrode through an ion pumping process triggered by the external pressure, greatly improving the capacitance change, resulting in a pressure sensor with ultra-high sensitivity. can be provided.

Furthermore, by using a nanofiber polymer thin film manufactured by electrospinning technology, it is possible to obtain excellent performance over a wide range of pressures by having higher compressibility compared to existing micro-structured thin films.

1 is a diagram illustrating the flow of a hybrid nanofiber membrane manufacturing method according to an embodiment of the present invention;
Figure 2 is a diagram showing the concept of an MXene/PVA/LS hybrid nanofiber membrane according to an embodiment of the present invention;
Figure 3 is a diagram showing the flow of a capacitive pressure sensor manufacturing method according to an embodiment of the present invention;
4 is a diagram illustrating the PDMS electrode concept according to an embodiment of the present invention;
5 is a diagram showing the structure of a pressure sensor for capacitance according to an embodiment of the present invention;
Figure 6 is a diagram showing the interaction between MXene functional groups (-OH, -F and -O) and LS through hydrogen bonding in a hybrid nanofiber membrane-based pressure sensor according to an embodiment of the present invention;
Figure 7 is a diagram showing the operating principle of a hybrid nanofiber membrane-based pressure sensor under NP (No pressure) and UP (Under pressure) conditions according to an embodiment of the present invention;
Figure 8 shows (a) [TFSI-] anion characteristics, (b) [Li +] cation characteristics, and the immobilization of ion pairs on the MXene surface through the formation of hydrogen bonds and Coulomb attraction according to an embodiment of the present invention. Diagram showing hybrid nanospectral analysis,
Figure 9 shows (a) initial (NP) and final (UP) capacitance values of pressure sensors manufactured with different concentrations of lithium salts, (b) of pressure sensors manufactured with different concentrations of lithium salts, according to an embodiment of the present invention. This is a diagram showing the change in relative capacitance value according to various pressures.

The advantages and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. The present embodiments are merely provided to ensure that the disclosure of the present invention is complete and to provide common knowledge in the technical field to which the present invention pertains. It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

In describing the embodiments of the present invention, if it is judged that a detailed description of a known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted, and the terms described below will be used in the embodiments of the present invention. These are terms defined in consideration of the function of , and may vary depending on the intention or custom of the user or operator. Therefore, the definition should be made based on the contents throughout this specification.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments of the present invention illustrated below may be modified into various other forms, and the scope of the present invention is not limited to the embodiments detailed below. Examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

The present invention produces a hybrid nanofiber membrane by mixing an ionic salt of lithium sulfonamides and MXene in a poly (vinyl alcohol) elastomer matrix and then electrospinning. and use it as a sensing membrane.

A pressure sensor can be manufactured using a hybrid nanofiber membrane according to an embodiment, and the pressure sensor has a functional layer on the surface of MXene caused by hydrogen bonding with ion pairs of an ionic salt, forming an electrical double layer (EDL) at the electrode. It inhibits formation and greatly reduces the initial capacitance value.

When external pressure is applied to the pressure sensor according to one embodiment, the ion pumping process is triggered by the external pressure, and a thick electric double layer is created on the electrode through ion pumping, greatly improving the change in capacitance, resulting in ultra-high sensitivity. A pressure sensor can be provided.

Furthermore, the pressure sensor according to one embodiment uses a nanofiber membrane manufactured by electrospinning technology, so that it has higher compressibility than a conventional micro-structured thin film and can obtain excellent performance over a wide range of pressure.

Hereinafter, the hybrid nanofiber membrane and pressure sensor having the above-described characteristics will be described later.

Figure 1 is a diagram showing the flow of a hybrid nanofiber membrane manufacturing method according to an embodiment of the present invention.

Referring to Figure 1, 2D nanomaterial powder is dispersed in distilled water (DI Water) to generate a precursor solution (110). The 2D nanomaterial is one of MXene (Ti ₃ C ₂ T _x ), graphene, GO (Graphene Oxide), rGO (Reduced Graphene Oxide), molybdenum disulfide (MoS ₂ ), and black phosphorus. It can be.

Next, hydrophilic polymer powder is added using the transfer solution as a solvent and stirred on a hot plate to produce a hydrophilic polymer-2D nanomaterial gel (120). The hydrophilic polymer may be any one of poly(vinyl alcohol), poly(acrylamide), poly(ethylene glycol), and polyethylene oxide.

Next, an ionic salt is added to the hydrophilic polymer-2D nanomaterial gel at the desired concentration and stirred on a hot plate to produce an electrolyte (130). Ionic salts include lithium salt (Lithium bis(trifluoromethanesulfonyl)imide), potassium nitrate (KNO3), calcium nitrate (Ca(NO3)2), sodium chloride (NaCl), potassium bromide (KBr), cesium fluoride (CsF), and magnesium nitrate. (Mg3N2) or calcium phosphate (Ca3P2).

Next, the electrolyte solution is electrospun to create a 2D nanomaterial/hydrophilic polymer/ion salt hybrid nanofiber membrane (HNM) (140).

Nanofiber membranes manufactured using electrospinning technology have higher compressibility than existing micro-structured thin films, enabling excellent performance over a wide range of pressures.

Nanofiber membranes using ion salts can be used in various fields such as lithium-ion batteries, field effect transistors, super capacitors, and capacitive pressure sensors due to their excellent physical and chemical stability, high ionic conductivity, and high interfacial capacitance. do.

Figure 2 is a diagram illustrating the concept of an MXene/PVA/LS hybrid nanofiber membrane according to an embodiment of the present invention.

Referring to Figure 2, the PVA solution is mixed with MXene and LS, stirred, and then subjected to electrospinning to create a hybrid nanofiber membrane (HNM).

PVA is utilized for effective dissolution of LS and uniform dispersion of components throughout the polymer matrix, improving the ion transport properties of the sensing material and promoting the formation of an electrical double layer (EDL).

Ti ₃ C _{2 T} Due to the ion confinement effect, the cation-anion pairs ([Li ⁺ ]-[TFSI ^- ]) of LS are attached to the functional groups of MXene nanosheets embedded in the hybrid nanofiber membrane through hydrogen bonds (H-bonds).

Figure 3 is a diagram showing the flow of a capacitive pressure sensor manufacturing method according to an embodiment of the present invention.

Referring to Figure 3, a capacitive pressure sensor can be manufactured using a hybrid nanofiber membrane.

For this purpose, a hybrid nanofiber membrane produced by electrospinning a mixture of 2D nanomaterials and ionic salts is formed as a dielectric layer (310). Next, conductive flexible/flexible electrodes are placed in a sandwich form on both sides centered on the hybrid nanofiber membrane, thereby creating a capacitive pressure sensor (320). Flexible/soft electrodes may be composed of materials such as conductive thin films, conductive polymers, silver nanowires, CNTs, and conductive pastes. For example, a capacitive pressure sensor can be created by placing an MXene/PVA/LS hybrid nanofiber membrane in a sandwich structure between Au/M-PDMS (polydimethylsiloxane) electrodes.

A flexible pressure sensor can be manufactured using a hybrid nanofiber membrane. For example, a flexible pressure sensor can be manufactured in which the initial capacitance is reduced by hydrogen bonding in a hybrid nanofiber membrane and the final capacitance increases by triggering ion pumping when pressure is applied. Flexible pressure sensors have ultra-high sensitivity over a wide pressure range.

Wearable pressure sensors can be manufactured using hybrid nanofiber membranes. Hybrid nanofiber-based pressure sensors detect various physiological and physical signals such as pulse, breathing, voice, and touch, and are widely used in smart medicine/healthcare, sports, robots, automobiles, and defense industries.

Figure 4 is a diagram illustrating the PDMS electrode concept according to an embodiment of the present invention.

Referring to Figure 4, in order to manufacture electrodes for pressure sensors, PDMS was placed in an inexpensive sand paper template and spin-coated to create sandpaper covered in PDMS, and the M-PDMS film was peeled off ( Peeling off), a Ti/Au layer is deposited on the microstructured surface through electron beam evaporation to create an Au/M-PDMS electrode.

Figure 5 is a diagram showing the structure of a pressure sensor for capacitance according to an embodiment of the present invention.

In more detail, (a) is a photograph of the fabricated nanofiber membrane, (b) is a low-magnification FESEM image of the nanofiber membrane, and (c) is a low-resolution TEM image of single and multilayers of MXene inside a polymer matrix, inset. The inset figure is a high-resolution TEM image of MXene, (d) a schematic diagram of the fabricated device, and the inset figure is a cross-sectional FESEM image of the fabricated capacitive pressure sensor (microstructured PDMS/hybrid nanofiber membrane/microstructured PDMS). (e) A FESEM image of a PDMS electrode on which micro-structured Au was deposited using a sandpaper template, and (e) a photograph of the manufactured capacitive pressure sensor.

Figure 6 is a diagram showing the interaction between MXene functional groups (-OH, -F, and -O) and LS through hydrogen bonding in a hybrid nanofiber membrane-based pressure sensor according to an embodiment of the present invention.

Referring to Figure 6, the hybrid nanofiber membrane-based pressure sensor shows that the ([Li ⁺ ][TFSI ^- ]) ion pair of LS forms hydrogen bonds (H-bonds) with MXene functional groups (-OH, -F, and -O). are combined through Ion pairs are confined to the MXene surface through hydrogen bonds. As a result, the formation of an electric double layer at the interface between the hybrid nanofiber membrane and the electrode is suppressed, and the initial capacitance value of the limited pressure sensor is reduced.

Figure 7 is a diagram showing the operating principle of a hybrid nanofiber membrane-based pressure sensor under NP (No pressure) and UP (Under pressure) conditions according to an embodiment of the present invention.

The inset figure in FIG. 7 is a diagram schematically showing the process that occurs inside the nanofiber membrane.

Referring to Figure 7, in the hybrid nanofiber membrane-based pressure sensor, in the initial state where no pressure is applied, the ([Li ⁺ ][TFSI ^- ]) ion pair of LS forms hydrogen bonds (H-bonds) with the MXene functional group to form MXene. bonded to the surface. Then, when pressure is applied, the ([Li ⁺ ][TFSI ^- ]) ion pairs are separated on the MXene surface due to the ion pumping phenomenon, creating a thick electric double layer.

More specifically, the hybrid nanofiber membrane-based pressure sensor is a hybrid nanofiber membrane-based pressure sensor in which the [Li ⁺ ] cation of LS is bonded to the MXene surface containing MXene functional groups (-OH, -F, and -O) through hydrogen bonds (H-bonds). do. And the [TFSI ^- ] anion combines with the [Li ⁺ ] cation due to Coulomb's law, forming a pair of [Li ⁺ ] cation and [TFSI ^- ] anion. Before pressure is applied, the ([Li ⁺ ][TFSI ^- ]) ion pairs are confined to the MXene surface through hydrogen bonds. As a result, the formation of an electric double layer at the interface between the hybrid nanofiber membrane and the electrode is suppressed, and the initial capacitance value of the limited pressure sensor is reduced.

When pressure is applied, the pressure sensor decreases the distance between the two electrodes, increasing the electric field strength and consequently increasing the force applied to the particles affected by the electric field. Due to this phenomenon, the pressure sensor initiates an ion pumping process, where ([Li ⁺ ][TFSI ^- ]) ion pairs are separated from the MXene surface, forming a thick electric double layer at the hybrid nanofiber membrane and electrode interface. Accordingly, the relative change in capacitance increases.

The figure on the right of FIG. 7 is a diagram showing the Helmholtz model before and after introducing nanoparticles into an ionic electrolyte. The pressure sensor model (modified model) containing nanoparticles in ionic liquid shows low initial capacitance and high sensitivity compared to the previous model (traditional mode).

Figure 8 shows (a) [TFSI ^- ] anion characteristics, (b) [Li ⁺ ] cation characteristics, and the immobilization of ion pairs on the MXene surface through the formation of hydrogen bonds and Coulomb attraction according to an embodiment of the present invention. This is a diagram showing the hybrid nano spectrum analysis.

Referring to (a), the red-shifts of the expansion-contraction mode of the [ ^TFSI- ] anion at ~742 cm ^-1 assigned to the NSO, SN, CF and FCS vibrations can be The ([Li ⁺ ][TFSI ^- ]) ion pair is bound due to the electrostatic attraction between the ([Li ⁺ ][TFSI ^- ]) ion pair and the MXene functional group.

Referring to (b), blue-shifts of Li ⁺ Raman vibrational modes observed for LS(60)-MXene-PVA (SO ₂ stretching, CF ₃ stretching, N-CH stretching and CH ₂ stretching). further suggests the presence of hydrogen bonding interactions with the MXene functional group.

Figure 9 shows (a) initial (NP) and final (UP) capacitance values of pressure sensors manufactured with different concentrations of lithium salts, (b) of pressure sensors manufactured with different concentrations of lithium salts, according to an embodiment of the present invention. This is a diagram showing the change in relative capacitance value according to various pressures.

Referring to (a), ^all LS-MXene-PVA pressure sensors show negligible capacitance ^differences (e.g. LS For (60)-MXene-PVA, a low initial capacitance (C ₀ ) value of C ₀ = 20 ± 2.7 pF) is obtained.

However, under UP (Under Pressure) conditions (~200kPa), the C _p value is the C _p value for all LS-MXene-PVA pressure sensors (e.g., C _p = 8761.6 ± 178.7 pF for LS(60)-MXene-PVA). This becomes significantly higher than C ₀ . The entire sensor structure induced by the applied pressure eventually increases the electrostatic force exerted on the particles under the influence of the external electric field. This process triggers the cleavage of hydrogen bonds between ions and MXene functional groups, ultimately strengthening the EDL at the electrode/electrolyte interface.

Referring to (b), the relative capacitance change observed for the LS-MXene-PVA pressure sensor with LS concentrations of 20%, 40%, and 60%, with the highest output obtained from the LS(60)-MXene-PVA sensor. Demonstrates high pressure detection function.

So far, the present invention has been examined focusing on its embodiments. A person skilled in the art to which the present invention pertains will understand that the present invention can be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered from an illustrative rather than a restrictive perspective. The scope of the present invention is indicated in the claims rather than the foregoing description, and all differences within the equivalent scope should be construed as being included in the present invention.

Claims (9)

Dispersing the 2D nanomaterial in distilled water to create a precursor solution;
Adding a hydrophilic polymer using the transposition solution as a solvent and stirring on a hot plate to create a hydrophilic polymer-2D nanomaterial gel;
In order to combine or separate the cation-anion pair of the ionic salt and the 2D nanomaterial depending on whether pressure is applied, adding the ionic salt to the hydrophilic polymer-2D nanomaterial gel and then stirring on a hot plate to produce an electrolyte solution; and
Electrospinning an electrolyte solution to create a 2D nanomaterial/hydrophilic polymer/ion salt hybrid nanofiber membrane;
A hybrid nanofiber membrane manufacturing method comprising: The method of claim 1, wherein the 2D nanomaterial is
A method of manufacturing a hybrid nanofiber membrane characterized by any one of MXene, graphene, GO (Graphene Oxide), rGO (Reduced Graphene Oxide), molybdenum disulfide (MoS ₂ ), and black phosphorus. . The method of claim 1, wherein the hydrophilic polymer is
Hybrid nanofibers characterized in that they are any one of polyvinyl alcohol (poly(vinyl alcohol)), poly(acrylamide), poly(ethylene glycol), and polyethylene oxide. Membrane manufacturing method. The method of claim 1, wherein the ionic salt is
Lithium salt (Lithium bis(trifluoromethanesulfonyl)imide), potassium nitrate (KNO ₃ ), calcium nitrate (Ca(NO ₃ ) ₂ ), sodium chloride (NaCl), potassium bromide (KBr), cesium fluoride (CsF), magnesium nitrate ( Method for producing a hybrid nanofiber membrane, characterized in that any one of Mg ₃ N ₂ ) and calcium phosphate (Ca ₃ P ₂ ). Generating a hybrid nanofiber membrane dielectric layer by electrospinning a mixture of a hydrophilic polymer, a 2D nanomaterial, and an ionic salt; and
Creating a capacitive pressure sensor by placing electrodes in a sandwich shape on both sides of the hybrid nanofiber membrane dielectric layer; Includes,
A method of manufacturing a capacitive pressure sensor, characterized in that an ionic salt is added to a hydrophilic polymer-2D nanomaterial to bind or separate the cation-anion pair of the ionic salt and the 2D nanomaterial depending on whether pressure is applied. In the hybrid nanofiber membrane produced by electrospinning a mixture of 2D nanomaterials and ionic salts in a hydrophilic polymer,
A hybrid nanofiber membrane characterized in that an ionic salt is added to a hydrophilic polymer-2D nanomaterial for binding or separating the cation-anion pair of the ionic salt and the 2D nanomaterial depending on whether pressure is applied. A hybrid nanofiber membrane dielectric layer created by electrospinning a mixture of 2D nanomaterials and ionic salts in a hydrophilic polymer; and
Electrodes placed in a sandwich shape on both sides centered on the hybrid nanofiber membrane dielectric layer; Includes,
A capacitive pressure sensor characterized in that an ionic salt is added to a hydrophilic polymer-2D nanomaterial to bind or separate the cation-anion pair of the ionic salt and the 2D nanomaterial depending on whether pressure is applied. The method of claim 7, wherein the capacitive pressure sensor is
In the initial state where no pressure is applied, the cation-anion pair of the ionic salt attaches to the functional group of the 2D nanomaterial of the hybrid nanofiber membrane through hydrogen bonds (H-bonds), suppressing the formation of an electric double layer at the interface between the hybrid nanofiber membrane and the electrode. A capacitive pressure sensor characterized by reducing the initial capacitance value. The method of claim 8, wherein the capacitive pressure sensor is
When pressure is applied, the distance between the two electrodes decreases, increasing the electric field strength and consequently increasing the force exerted on the particles under the influence of the electric field, thus starting the ion pumping process, causing the cation-anion pairs of the ionic salt to form A capacitive pressure sensor that is separated from the surface of a 2D nanomaterial and forms an electric double layer of a predetermined thickness at the interface between the hybrid nanofiber membrane and the electrode.