Strain sensor comprising magnetoplasmonic nanoparticles and manufacturing method therefor

Abstract

A strain sensor according to the present invention comprises: a photo-alignment layer comprising photo-aligned magnetoplasmonic nanoparticles; and an elastic film layer, wherein the magnetoplasmonic nanoparticles comprise a silver (Ag) core and an iron oxide shell.

Description

Strain sensor including magnetoplasmonic nanoparticles and method for manufacturing the same

[0001] The present invention relates to a strain sensor including magnetoplasmonic nanoparticles and a method for manufacturing the same.

[0002] Rapid advancements in embedded devices and wireless communication technologies are driving the development of smart sensing systems for monitoring physiological parameters in diverse fields, including healthcare, sports, and recreational activities. Physiological signals often exist at frequencies and intensities that enhance the human ability to accurately perceive them. Well-established, commercially available electronic devices, such as stethoscopes and digital accelerometers, are specifically designed to detect and record these signals for medical purposes. Recently, interest in utilizing mechano-responsive materials to track body movements, heartbeats, and blood flow has grown rapidly, leading to the development of wearable devices capable of precisely recording these physiological signals. However, wearable devices that transmit physiological signals face limitations, such as low durability and sensor reliability.

[0003] In particular, conventional wearable sensors for human applications have been monitored by dispersing conductive materials on a polymer base that can be attached to the human body and observing changes in electrical conductivity due to stretching. However, in these cases, in addition to the sensor itself, a means for measuring changes in electrical conductivity must be electrically connected, which leads to significant problems such as increased sensor device bulk and user inconvenience. Furthermore, because the electronic device must be worn on the body, it is difficult to apply in environments with electromagnetic interference or where electrical safety is required.

[0004] Accordingly, there is a need to develop a strain sensor that monitors human body movements without requiring any secondary equipment attached to the human body other than the sensor, and that enables stable monitoring even in environments with electromagnetic interference.

[0005] The purpose of the present invention is to provide a strain sensor that can be applied to various fields by visualizing deformation caused by scattering and inter-particle resonance coupling of magnetoplasmonic nanoparticles included in the strain sensor.

[0006] Another object of the present invention is to provide a strain sensor capable of independently measuring strain without separately including a power supply device and a signal transmission device.

[0007] Another object of the present invention is to provide a strain sensor that can exhibit high stability even in changes in the external environment.

[0008] A strain sensor according to the present invention comprises a photo-array layer including photo-arrayed magneto-plasmonic nanoparticles and an elastic film layer, wherein the magneto-plasmonic nanoparticles are characterized by including a silver (Ag) core and an iron oxide shell.

[0009] A strain sensor according to one embodiment of the present invention may be characterized in that a color change occurs in the optical array layer according to the stretching of the sensor.

[0010] A strain sensor according to one embodiment of the present invention may be characterized in that it does not require a power supply device, a wired signal transmission device, or a wireless signal transmission device.

[0011] In a strain sensor according to one embodiment of the present invention, the magnetoplasmonic nanoparticles may be characterized by having an average particle size of 50 to 500 nm.

[0012] In a strain sensor according to one embodiment of the present invention, the elastic film layer may be characterized by including one or two or more selected from polydimethylsiloxane, polyurethane, polyurethane acrylate, polyvinyl alcohol, and polyimide.

[0013] In a strain sensor according to one embodiment of the present invention, the elastic film layer may be characterized by having a thickness of 10 to 1000 ㎛.

[0014] The present invention also provides a method for manufacturing a strain sensor, and the method for manufacturing a strain sensor according to the present invention comprises a first step of forming an optical array layer by applying a magneto-plasmonic nanoparticle dispersion on a membrane under a magnetic field and drying the dispersion;

[0015] A second step of applying and curing a partially cured elastic polymer on the above-mentioned optical array layer to form an elastic film layer; and

[0016] A third step of removing the membrane after the second step is included.

[0017] In a method for manufacturing a strain sensor according to one embodiment of the present invention, the magnetic field may be characterized as satisfying 400 to 800 G.

[0018] In a method for manufacturing a strain sensor according to one embodiment of the present invention, the magneto plasmonic nanoparticle dispersion may be characterized in that it contains 3 to 8 mg of magneto plasmonic nanoparticles per 1 ml.

[0019] The strain sensor according to the present invention comprises a photo-array layer including photo-arrayed magneto-plasmonic nanoparticles and an elastic film layer, wherein the magneto-plasmonic nanoparticles are characterized by including a silver (Ag) core and an iron oxide shell, so that the stretching of the strain sensor can be visually monitored, and has the advantage of being able to independently measure strain without separately including a power supply and a signal transmission device, and exhibiting high stability even with changes in the external environment.

[0020] FIG. 1 schematically illustrates the operation process of a sensor including magnetoplasmonic nanoparticles according to one embodiment of the present invention.

[0021] FIG. 2 illustrates a method for manufacturing a sensor including magnetoplasmonic nanoparticles according to one embodiment of the present invention, and the results of observing the sensor after manufacturing using a SEM (Scanning Electron Microscope).

[0022] FIG. 3 illustrates an optical array layer formed on a membrane (left) and a membrane surface (right) observed after the optical array layer is transferred from the membrane to an elastic film layer in a method for manufacturing a strain sensor according to one embodiment of the present invention.

[0023] Figure 4 shows and illustrates the color difference according to the particle size of magnetoplasmonic particles according to one embodiment of the present invention.

[0024] Figure 5 is a view showing the color change according to the stretching of a strain sensor according to one embodiment of the present invention.

[0025] Figure 6 is a diagram illustrating a change in color according to the distance between particles in magnetoplasmonic particles according to one embodiment of the present invention.

[0026] Figure 7 illustrates various application methods of a strain sensor according to one embodiment of the present invention.

[0027] Advantages and features of embodiments of the present invention, and methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

[0028] When describing embodiments of the present invention, detailed descriptions of known functions or configurations will be omitted if they are deemed to unnecessarily obscure the gist of the invention. Furthermore, the terms described below are defined in light of their functions in the embodiments of the present invention and may vary depending on the intent or custom of the user or operator. Therefore, their definitions should be based on the overall content of this specification.

[0029] The strain sensor according to the present invention comprises an optical array layer including optically arrayed magnetoplasmonic nanoparticles and

[0030] Contains an elastic film layer,

[0031] The above magnetoplasmonic nanoparticles are characterized by comprising a silver (Ag) core and an iron oxide shell.

[0032] The strain sensor according to the present invention has a characteristic in that the color of the optical array layer changes according to the stretching of the sensor. Specifically, the spacing between magnetoplasmonic nanoparticles included in the optical array layer changes according to the stretching of the sensor, thereby causing a color change.

[0033] The strain sensor of the present invention monitors elasticity through color changes, so it does not require separate data measurement and analysis devices, such as electrical conductivity measurement, and thus has the unique advantage of not requiring wired or wireless signal transmission devices. Furthermore, since it does not require separate data measurement and analysis, it has the advantage of not requiring a battery or power supply. Due to these advantages, the strain sensor of the present invention can ensure significantly improved convenience when applied to the human body.

[0034] The magnetoplasmonic nanoparticles can have an average particle size of 50 to 500 nm, preferably 70 to 330 nm, and more preferably 160 to 190 nm, and can measure changes in the sensor with high sensitivity by satisfying this range. In addition, the optical array layer can have a structure in which the magnetoplasmonic nanoparticles are laminated in 1 to 7 layers, preferably 1 to 5 layers, and accordingly, the thickness of the optical array layer can be 0.1 to 1.5 ㎛, preferably 0.1 to 0.8 ㎛.

[0035] Specifically, the magnetoplasmonic nanoparticles include a silver (Ag) core and an iron oxide shell, wherein the iron oxide may be Fe3O4. Hereinafter, such magnetoplasmonic nanoparticles are referred to as Ag@Fe3O4.

[0036] The elastic film layer may include one or more selected from polydimethylsiloxane, polyurethane, polyurethane acrylate, polyvinyl alcohol, and polyimide, and preferably polydimethylsiloxane or polyvinyl alcohol may be used. The elastic film layer may have a thickness of 10 to 1000 ㎛, preferably 200 to 800 ㎛, and more preferably 250 to 500 ㎛. If the thickness of the elastic film layer is too thin, a problem may occur with respect to sensor durability, and if the thickness of the elastic film layer is too thick, a problem may occur with respect to lowering the sensor sensitivity.

[0037]

[0038] The present invention also provides a method for manufacturing a strain sensor. The method for manufacturing a strain sensor according to the present invention may be a method for manufacturing a strain sensor including an optical array layer containing the magnetoplasmonic nanoparticles described above.

[0039] The method for manufacturing a strain sensor according to the present invention comprises the following steps: a first step of forming an optical array layer by applying a magneto-plasmonic nanoparticle dispersion on a membrane under a magnetic field and drying the dispersion;

[0040] A second step of applying and curing a partially cured elastic polymer on the above optical array layer; and

[0041] A third step of removing the membrane after the second step is included.

[0042] The method for manufacturing a strain sensor according to the present invention has the advantage of being able to manufacture a stable strain sensor in a simple manner without damaging the optical array layer manufactured by including the first to third steps.

[0043] First, a method for manufacturing magnetoplasmonic nanoparticles will be described in detail. In a method for manufacturing a strain sensor according to one embodiment of the present invention, the magnetoplasmonic nanoparticles may include a silver (Ag) core and an iron oxide (Fe3O4) shell.

[0044] First, an iron precursor solution is prepared by adding 30 to 50 mmol of iron precursor per 100 ml of ethylene glycol. After adding sodium acetate and a silver precursor, a reaction can be performed. At this time, sodium acetate can be added in an amount of 6 to 7.5 mol per 1 mol of iron precursor, and the silver precursor can be added in an amount of 0.1 to 0.2 mol per 1 mol of iron precursor. The reaction can be performed including a step of heating at 190 to 230°C for 5 to 20 hours after adding sodium acetate and a silver precursor. The iron precursor can preferably be iron nitrate or iron nitrate hydrate, and the silver precursor can use silver nitrate. After the completion of the reaction, a step of washing and drying the manufactured nanoparticles with water or alcohol can be further included.

[0045] In the first step, the magnetoplasmonic nanoparticles can be stabilized with citrate and then mixed with water to prepare a dispersion. Specifically, the citrate stabilization can be performed by dispersing 50 to 150 mg of magnetoplasmonic nanoparticles per 100 ml of a citrate aqueous solution prepared at a concentration of 0.1 to 10 mg / ml, preferably 0.1 to 2 mg / ml, followed by ultrasonic treatment for 1 to 5 hours and repeated washing with deionized water three or more times. This citrate stabilization significantly improves the dispersion stability of the magnetoplasmonic nanoparticles and ensures uniformity of arrangement in the optical array layer. Additionally, the magneto-plasmonic nanoparticle dispersion may be a dispersion of previously manufactured magneto-plasmonic nanoparticles in water, and the dispersion may contain 3 to 8 mg of magneto-plasmonic nanoparticles per 1 ml of water.

[0046] In the method for manufacturing a strain sensor according to the present invention, the first step is a step of forming an optical array layer by applying a magnetoplasmonic nanoparticle dispersion onto a membrane under a magnetic field and drying the dispersion. At this time, the magnetic field can be formed by a magnet, and the magnetic field strength can satisfy 400 to 800 G, preferably 500 to 700 G.

[0047] The second step is to apply and cure a partially cured elastic polymer on the optical array layer. At this time, the elastic polymer may include one or more selected from polydimethylsiloxane, polyurethane, polyurethane acrylate, polyvinyl alcohol, and polyimide, and preferably, polydimethylsiloxane can be used. Specifically, the polydimethylsiloxane elastomer mixture is partially polymerized under curing conditions to reach a semi-cured state, and then applied onto the optical array layer and further cured. Through this second step, a portion of the optical array layer can be incorporated into the elastic polymer, thereby exhibiting high durability and preventing a decrease in sensor sensitivity due to the surrounding environment.

[0048] After the second step, a structure in which a membrane, an optical array layer, and an elastic film layer are sequentially laminated is shown, and then in the third step, the membrane is removed to finally manufacture a strain sensor in which the optical array layer is transferred to the elastic film layer.

[0049] The strain sensor manufactured through the above steps 1 to 3 can be applied to the human body to monitor human movement as well as to monitor strain occurring in architectural and civil engineering structures.

[0050]

[0051] Hereinafter, the present invention will be specifically described through examples and comparative examples. The examples below are provided solely to aid understanding of the present invention, and the scope of the present invention is not limited by the examples below.

[0052] Synthesis of magnetoplasmonic particles and fabrication of sensors

[0053] An iron precursor solution was prepared by mixing 4 mmol of Fe(NO3)3·9H2O with 40 mL of ethylene glycol. 25 mmol of sodium acetate and 0.59 mmol of AgNO3 were added, and the mixture was stirred vigorously until the reactants completely disappeared. The resulting suspension was transferred to an autoclave and heated at 210°C for approximately 8 hours. After removing the reactants from the autoclave, the mixture was naturally cooled to room temperature, and the precipitate was magnetically collected, washed twice or more with deionized water and absolute ethanol, and dried in a vacuum for 24 hours to prepare Ag@Fe3O4 magnetoplasmonic nanoparticles.

[0054] A 15 × 15 mm polyethersulfone (PES) membrane (pore size: 0.2 μm) was placed 10 mm apart from a neodymium magnet. The magnetic field strength on the surface of the PES film was maintained at 600 G. 25 μl of an aqueous dispersion of citrate-stabilized Ag@Fe3O4 magnetoplasmonic nanoparticles was pipetted onto the PES film and dried under atmospheric pressure. After complete drying, the film was maintained under a magnetic field for 1 h to form a stable film of structurally colored amorphous photonic arrays (APAs) of Ag@Fe3O4 magnetoplasmonic nanoparticles. Simultaneously, a polydimethylsiloxane (PDMS) elastomer mixture was prepared. The elastomer mixture was poured onto a flat petri dish and polymerized at 50 °C for 40 min to reach a semi-cured state. The semi-cured PDMS elastomer was then transferred onto the APA and further cured at 50°C. Afterwards, the PES membrane was peeled off and the elastomer was cut to produce a magnetoplasmonic elastomer (MPE).

[0055] Figure 2 illustrates the manufacturing process of APA and MPE, and Figure 2b shows the results of observing the arrangement of Ag@Fe3O4 magnetoplasmonic nanoparticles using a Scanning Electron Microscope (SEM). Through this, it can be confirmed that the Ag@Fe3O4 magnetoplasmonic nanoparticles have a constant arrangement even after being transferred to PDMS, and at this time, the thickness of the PDMS was confirmed to be 340 ㎛. Figure 3 shows a colored amorphous light-array layer formed on a polyethersulfone membrane (left) and an observation of the surface of the membrane after the light-array layer was transferred to PDMS (right). In addition, it was confirmed that the optical array layer formed 1 to 3 layers of magneto plasmonic nanoparticles and had an average thickness of about 0.2 to 0.6 ㎛. When observing the membrane after transfer, it was confirmed that almost all magneto plasmonic nanoparticles were transferred, so it can be seen that the thickness of the optical array layer transferred on the PDMS was also about 0.2 to 0.6 ㎛.

[0056] At this time, the citrate-stabilized Ag@Fe3O4 magnetoplasmonic nanoparticle aqueous dispersion was prepared by dissolving 100 mg of the manufactured Ag@Fe3O4 magnetoplasmonic nanoparticle powder in 0.6 mg / ml -1 The nanoparticles were prepared by stabilizing the citric acid functional groups by redispersing them in 100 ml of a citric acid solution, ultrasonicating them for 2 hours, and then washing them three or more times with deionized water. After stabilization, the final magnetoplasmonic nanoparticle aqueous dispersion was prepared to contain 5 mg of Ag@Fe3O4 magnetoplasmonic nanoparticles per ml. The Ag@Fe3O4 magnetoplasmonic nanoparticles stabilized by the negative charge of the citrate salt are expected to have the effect of enhancing the dispersion stability due to the repulsive force between particles and improving the uniformity of the arrangement when forming an amorphous photonic array film.

[0057]

[0058] Confirmation of the color change characteristics of magnetoplasmonic nanoparticle layers

[0059] Core-shell particles such as Ag@Fe3O4 magnetoplasmonic nanoparticles exhibit different optical scattering behaviors as the thickness of the shell increases, and the color of the Ag@Fe3O4 magnetoplasmonic nanoparticle layer according to particle diameter was observed and the results are shown in Fig. 4. Referring to Fig. 4, it can be confirmed that various color spectra are exhibited depending on the change in particle diameter.

[0060] Figure 5 observes and illustrates changes in MPE depending on strain. Figure 5a confirms that color changes due to strain occur at the same strain of 50%, and this color change appears to be completely reversible.

[0061] Each reflection spectrum of the MPE was measured using a fiber-optic-based reflection / scattering probe, and it was confirmed that a low-range peak of 400 to 600 nm and a high-range peak of 700 to 900 nm were observed. Hereinafter, the low-range is referred to as λ s , high region λ d and these are λ dip It was divided into .

[0062] MPEs containing nanoparticles manufactured with different diameters are compared as shown in Fig. 5b, where λ s and λ d The value increased in proportion to the diameter of the nanoparticles. In particular, the most rapid change occurred when the diameter of the nanoparticles increased from 145 nm to 200 nm, which is consistent with the color change of the fabricated MPE. The chromaticity of the MPE is λ s , λ d and λ dip can be interpreted as a specific combination of . In particular, when there is a mechanical discoloration phenomenon, the change in these spectral elements can be converted into each color change of the MPE. Referring to Fig. 5c, the largest λ of 46 nm in the film containing particles with a diameter of 176 nm dipMovement was observed.

[0063] The operating mechanism of the fabricated MPE device was further observed and is shown in Fig. 6. The light absorption and scattering behavior of the magnetoplasmonic dimer and the hexagonally packed unit cell with a diameter of 176 nm were calculated according to the Mie solution according to Maxwell's equations at various interparticle distances of 10 to 50 nm. Referring to Fig. 6b, as the interparticle distance increases, λ d It can be confirmed that the LSPR (localized surface plasmon resonance) peak also shifts significantly toward the blue. Based on these results, the MPE working mechanism as shown in Fig. 6a was established, and compared to existing stretch sensors based on electric conductors, capacitors, or piezoelectric systems, the MPE device can operate completely independently of the power supply, so it has the advantage of being applicable to environments with electromagnetic interference or situations where electrical safety is important.

[0064]

[0065] Applications of sensors using magnetoplasmonic particles

[0066] The discoloration of the strain sensor according to one embodiment of the present invention can be observed using a reflectance spectrophotometer, the naked eye, or a smartphone camera application, and an estimated strain value can be derived through this. Such a strain sensor can monitor the movement of joints such as the neck, knees, and elbows, as shown in FIG. 7a, and can also monitor small movements such as heartbeats, eye blinks, and convulsions. By applying the mechanical discoloration of the device, structural joints can be monitored in buildings, civil engineering structures, and industrial systems, as shown in FIG. 7b, and problems arising therefrom can be prevented. In addition, as shown in FIG. 7f, there is an advantage that it can be applied to an MPE-based morphing display device.

Claims

1. An optical array layer comprising optically aligned magnetoplasmonic nanoparticles and Contains an elastic film layer, A strain sensor characterized in that the magnetoplasmonic nanoparticles include a silver (Ag) core and an iron oxide shell.

2. In paragraph 1, The above strain sensor is a strain sensor characterized in that the color of the optical array layer changes according to the stretching of the sensor.

3. In paragraph 1, A strain sensor characterized in that the strain sensor does not require a power supply, a wired signal transmission device, or a wireless signal transmission device.

4. In paragraph 1, A strain sensor characterized in that the magnetoplasmonic nanoparticles have an average particle size of 50 to 500 nm.

5. In paragraph 1, A strain sensor characterized in that the elastic film layer comprises one or more selected from polydimethylsiloxane, polyurethane, polyurethane acrylate, polyvinyl alcohol, and polyimide.

6. In paragraph 1, A strain sensor characterized in that the elastic film layer has a thickness of 10 to 1000 ㎛.

7. A first step of forming an optical array layer by applying a magneto-plasmonic nanoparticle dispersion onto a membrane under a magnetic field and drying it; A second step of applying and curing a partially cured elastic polymer on the above-mentioned optical array layer to form an elastic film layer; and A method for manufacturing a strain sensor, comprising a third step of removing the membrane after the second step.

8. In paragraph 7, A method for manufacturing a strain sensor, characterized in that the magnetic field satisfies 400 to 800 G.

9. In paragraph 7, A method for manufacturing a strain sensor, characterized in that the magneto plasmonic nanoparticle dispersion contains 3 to 8 mg of magneto plasmonic nanoparticles per 1 ml.

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