KR20230067038A - Nanofluid sensor - Google Patents

Abstract

The present invention relates to nanofluidic sensors. The nanofluidic sensor according to the present invention utilizes a fluid to sensitively detect deformation caused by a user's motion or an external stimulus, and is coupled to a wearable device or an object that undergoes a deformable behavior such as the user's body to detect the object's deformation. A flexible board part formed of a material capable of deformation and shape restoration so that it is transformed according to the behavior and can be restored to its original shape after deformation; a fluid accommodating part formed in the form of a channel capable of accommodating nanofluids containing conductive nanoparticles inside the flexible substrate part; and a pair of electrodes, each of one side of which is inserted into the channel and electrically connected to the nanofluid, and the other side is exposed to the outside of the flexible substrate and is electrically connected to an external device.

Description

Nanofluid sensor {Nanofluid sensor}

The present invention relates to a nanofluid sensor, and more particularly, to utilize nanofluid to sensitively detect deformation caused by a user's motion or an external stimulus, and to provide mechanical properties that are not easily damaged or damaged even by repeated deformation. It relates to a nanofluid sensor having an improved structure so as to be able to have.

Machines have developed as tools that benefit human life, and today, along with the Fourth Industrial Revolution, they are facing a paradigm shift as machines interacting with humans. Robots are the most direct and representative examples in this flow. Existing robots were limited to repeatedly performing the same task without interaction, but recently, with the development of related basic technologies, many robotics studies and products have been conducted in the direction of cooperation and coexistence through human-robot interaction. are being presented. Wearable robots are the most popular type of interactive robots in that they recognize human motions and assist or sense external stimuli at the same time. To support this, a sensor system for reliable motion recognition and external stimulus detection must be established, and flexibility that can be attached to the nonlinear body must be secured for smooth human-robot cooperation. In relation to this, many wearable sensors are being developed, such as the direct circuit design method on a flexible substrate, as well as the production of conductive flexible polymers and hydrogels.

The method of designing a circuit for a sensor on a flexible board is the simplest, but there is a limit to securing elasticity for motion recognition and detection in that the material constituting the circuit is solid.

Korean Registered Patent Registration No. 10-2292220 Japanese Registered Patent Publication No. 6618546

Therefore, the present invention has been devised to solve the above problems, and an object of the present invention is to have robust physical properties that are highly responsive to deformation caused by a user's motion or external stimulus and are not easily damaged even by repeated deformation. It is intended to provide a nanofluid sensor.

In order to achieve the above object, the nanofluidic sensor according to the present invention utilizes a fluid to sensitively detect deformation caused by a user's motion or an external stimulus. A flexible board part formed of a material capable of being deformed and restored to its original shape after being coupled to being deformed according to the behavior of the target object, so that it can be restored to its original shape; a fluid accommodating part formed in the form of a channel capable of accommodating nanofluids containing conductive nanoparticles inside the flexible substrate part; and a pair of electrodes, each of one side of which is inserted into the channel and electrically connected to the nanofluid, and the other side is exposed to the outside of the flexible substrate and is electrically connected to an external device.

It is preferable that the channel of the fluid accommodating unit has a shape penetrating the center of the flexible substrate unit, and each electrode is inserted into both edges of the channel to be electrically connected to the nanofluid accommodated in the channel and at the same time open part of the channel. It is preferable to be configured to close.

Preferably, the nanofluid accommodated in the fluid accommodating part is formed by ultrasonic dispersion treatment of conductive particles.

The conductive particles are conductive or polar and magnetic nanoparticles dispersible in a fluid on a nanoscale, such as graphene, graphene oxide, and carbon-based nanoparticles based on carbon nanotubes and magnetic nanoparticles based on iron oxide, copper oxide, and aluminum oxide. It may be any one of them or a combination thereof .

The present invention obtains nanofluids having different colloidal structures and sensitivity according to the deformation range by applying the ultrasonic dispersion energy differently to the conductive particles according to the deformation range of the object undergoing the deformation behavior, and as a sensor. can be utilized For example, the present invention is a colloidal structure in a delaminated state having a first area with respect to the plane and a colloidal structure in an in-plane cut state having a second area smaller than the first area. It can be configured so that any one can be selected and used.

The flexible substrate includes a central deformable part having a first width and a pair of electrode connecting parts each extending from both side edges of the central deformable part and having a second width greater than the width of the central deformable part. It is also possible to do so.

The flexible substrate part may further include a tapered part interposed between the central deformable part and each electrode connection part in a gradually increasing width, and the nanofluid may be configured to be accommodated only in the central deformable part and the taper part. .

Of course, the present invention is coupled to each of the electrode connection parts, and may further include a curable polymer in which a through hole through which each electrode passes is formed and formed of a thermosetting resin material to suppress deformation.

The nanofluid sensor according to the present invention having the configuration as described above is configured such that a fluid receiving portion accommodating nanofluid containing conductive nanoparticles is formed in the flexible substrate portion to which external stimulation is applied, thereby receiving fluid by external stimulation. During negative deformation, the resistance change according to the dispersion state of the nanoparticles makes it possible to sensitively detect the physical stimulus, and has the effect of not being easily damaged even by repeated deformation due to the flexibility of a fluid rather than a solid.

In addition, according to an embodiment in which the nanofluid accommodated in the fluid accommodating unit is formed by dispersing nanoparticles using an ultrasonic dispersion treatment method, the nanofluid containing nanoparticles capable of ultrasonic dispersion treatment is accommodated in the fluid accommodating unit. As a result, the dispersion state and colloidal structure of particles can be changed according to the ultrasonic energy applied to the fluid during the fabrication process, even if it is a nanofluid of the same material and concentration, and thus the sensitivity of the nanofluid sensor can be optimized according to the use environment. Advantages are expected.

1 is a view showing a molding process and structure of a nanofluid sensor according to an embodiment of the present invention.
2 is a diagram for explaining a sensing principle according to an embodiment of the present invention;
3 is a view for explaining a colloidal structure between nanoparticles accommodated in a fluid accommodating unit, which is a part of an embodiment of the present invention, and a formation process thereof.
Figure 4 is a graph showing the sensitivity measurement results for the stretching mode according to the ultrasonic dispersion energy of an embodiment of the present invention.
5 is a perspective view of a nanofluid sensor according to another embodiment of the present invention
5 is a perspective view of a nanofluid sensor according to another embodiment of the present invention.

In order to clarify the understanding of the present invention in the following description, descriptions of known techniques for the features of the present invention will be omitted. The following examples are detailed descriptions to aid understanding of the present invention, and it will be natural that they do not limit the scope of the present invention. Therefore, equivalent inventions that perform the same functions as the present invention will also fall within the scope of the present invention.

And, in the following description, the same identification symbol means the same configuration, and unnecessary redundant descriptions and descriptions of known technologies will be omitted. In addition, the description of each embodiment of the present invention below, which overlaps with the description of the background technology of the present invention, will also be omitted.

Hereinafter, a nanofluid sensor according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing the forming process and structure of a nanofluid sensor according to an embodiment of the present invention, FIG. 2 is a view for explaining the sensing principle according to an embodiment of the present invention, and FIG. 3 is an embodiment of the present invention It is a diagram for explaining the colloidal structure between nanoparticles accommodated in the fluid accommodating unit, which is a part of the example, and the formation process thereof.

As shown in FIGS. 1 and 2, the nanofluid sensor according to an embodiment of the present invention utilizes fluid to sensitively detect deformation caused by a user's motion or an external stimulus, and a flexible substrate ( 1), a fluid accommodating part 2, and a pair of electrodes 3.

The flexible substrate unit 1 is coupled to an object that undergoes a deformable behavior such as a wearable device or a user's body and is deformed according to the behavior of the object. It is formed of a material capable of deformation and shape restoration so that it can be restored to its shape.

The fluid accommodating part 2 is formed in the form of a channel capable of accommodating the nanofluid A containing conductive nanoparticles inside the flexible substrate part 1 .

Here, the nanofluid (A) means a fluid in which nanoscale solid particles are dispersed in an existing fluid (water or oil, etc.), and examples of particles that can be utilized include conductive nanoparticles and polar and magnetic nanoparticles. Examples include carbon-based nanoparticles (graphene, graphene oxide, and carbon nanotubes), iron oxide, copper oxide, and aluminum oxide.

One side of the pair of electrodes 3 is inserted into the channel and electrically connected to the nanofluid A, and the other side is exposed to the outside of the flexible substrate 1 and electrically connected to an external device.

The operating principle of the nanofluid sensor according to an embodiment of the present invention having such a configuration is as follows.

In this embodiment, according to the deformation of the flexible substrate part 1 by an external stimulus, the fluid accommodation part 2 in which the nanofluid A is accommodated is deformed together. The driving principle of the nanofluid sensor according to an embodiment of the present invention is based on the change in the conducting path of particles in the nanofluid (A) according to the deformation of the fluid accommodating part (2). That is, the resistance of the fluid changes according to the degree to which the dispersed conductive nanoparticles or ionized nanoparticles secure a conducting path through interparticle contact or a conducting path for ion transfer in the fluid accommodating part 2 .

2 shows an example of fabrication of the nanofluid sensor according to the present embodiment and a schematic dispersion state of nanoparticles in a fluid according to various sensing modes. Sensing modes can be classified into Touching, Stretching, and Widening, and the dispersion state of nanoparticles in the unit volume of the fluid is changed by the deformation of the fluid accommodating part 2 according to each situation, resulting in the entire nanofluid ( The conducting path of A) increases or decreases.

Representatively, when the Touching mode is executed as shown in (b) of FIG. 2 in the state of (a) of FIG. 2, as the fluid accommodating part 2 is locally compressed, the nanoparticles of the compressed part follow the flow of the surroundings. Move to (Squeezing). Accordingly, the resistance of the sensor increases along with the reduction of the local conducting path. In the same principle, in the stretching mode as shown in (c) of FIG. 2, the pipe is stretched in the longitudinal direction and the cross section is contracted at the same time, the number of particles per unit area decreases, the distance between particles increases, and the resistance increases as the conducting path decreases. It increases. Conversely, in the widening mode as shown in (d) of FIG. 2, the pipe contracts slightly in the longitudinal direction while the cross section greatly increases. Accordingly, the number of particles per unit area increases, the conducting path is established, and the resistance of the sensor decreases. .

In this way, in the nanofluid sensor according to the present embodiment, the fluid accommodating part 2 is deformed by an external force or stimulus applied to the flexible substrate part 1, and accordingly, the fluid accommodating part 2 By changing the resistance of the nanofluid (A) by the change in the dispersion state of the accommodated nanoparticles, it is possible to sense the operation of the flexible substrate part (1) or an external physical stimulus.

A nanofluid sensor according to an embodiment of the present invention having such an operating principle has a fluid accommodating part 2 in which a nanofluid A containing conductive nanoparticles is accommodated in a flexible substrate part 1 to which external stimuli are applied. By being configured to be formed, it is possible to sensitively detect the physical stimulus by the change in resistance according to the dispersion state of the nanoparticles when the fluid receiving part 2 is deformed by the external stimulus, and to the flexibility of the non-solid fluid Therefore, it is possible to expect the advantage of not being easily damaged even by repeated deformation.

And, as well shown in (b) and (d) of FIG. 1, the channel of the fluid accommodating portion 2 is formed in a shape penetrating the center of the flexible substrate portion 1, and each electrode ( 3) is inserted into both edges of the channel to be electrically connected to the nanofluid (A) accommodated in the channel and to close the open portion of the channel, so that the electrode 3 connection process and the fluid receiving portion 2 It is possible to improve the efficiency of the closing process.

As well shown in FIG. It can be implemented by injection molding in a state in which the dragon mold M2 is inserted.

The conductive nanoparticles constituting the nanofluid (A) include conductive or polar and magnetic nanoparticles such as graphene, graphene oxide, and carbon nanotube-based carbon nanoparticles and iron oxide, copper oxide, and aluminum oxide-based magnetic nanoparticles. It may be any one of them or a combination thereof.

On the other hand, the nanofluid (A) accommodated in the fluid accommodating unit (2) can be implemented by various methods, but in one embodiment of the present invention, nanoparticles are dispersed and formed using an ultrasonic dispersion treatment method. .

The ultrasonic dispersion treatment is the most actively used method in manufacturing the nanofluid (A), and transmits ultrasonic energy to the fluid to disperse the particles through vibration and shock waves generated by cavitation. Depending on the degree of ultrasonic energy delivered to the fluid, the dispersion state of the nanoparticles changes, which determines the colloidal structure in the fluid.

Nanoparticles in a dense state separate and disperse between particles with an increase in transmitted ultrasonic energy, but when the energy exceeds the in-plane strength of the particles, it can induce breakage of the particles. In each separation and breakage situation, the colloidal structure can be uniquely formed according to the shape and characteristics of nanoparticles.

3 schematically shows a colloidal structure of carbon nanotubes in the form of one-dimensional tubes and graphene nanoparticles in the form of a two-dimensional thin film according to ultrasonic energy irradiated to the nanofluid A accommodated in the fluid accommodating part 2. has been

As shown in (a) of FIG. 3, the carbon nanotubes in the form of one-dimensional tubes have a large entangling state between particles in a dense state due to their high aspect ratio and flexible characteristics. In this case, when ultrasonic energy is transmitted, separation between particles starts and the carbon nanotubes can be dispersed in a debundling state. When ultrasonic energy is delivered to a greater extent than the in-plane strength of carbon nanotubes, the particles break, and a nano-cutting state with a relatively low aspect ratio can be obtained.

As shown in (b) of FIG. 3, the graphene in the form of a two-dimensional thin film has a nanoscale thickness compared to a large planar area, has interactions between particles in a plane direction in a dense state, and forms a stacked state. As ultrasonic energy is applied, graphene in a dense state is separated from each other and becomes a delaminated state. When energy is transferred greater than the in-plane strength of graphene, the particles break and an independent particle dispersion state (in-plane cut state) with a relatively small plane area can be obtained.

After all, the present embodiment is configured so that the nanofluid (A) containing nanoparticles capable of ultrasonic dispersion treatment is accommodated in the fluid accommodating part (2), so even if the nanofluid (A) of the same material and concentration is a fluid in the manufacturing process The dispersion state and colloidal structure of the particles according to the ultrasonic energy applied to the carbon nanotubes in the form of one-dimensional tubes as shown in (a) of FIG . 3 and graphene nanoparticles in the form of two-dimensional thin films as shown in (b) of FIG . As it can be composed of various colloidal structures , it is possible to expect the advantage of optimizing the sensitivity of the nanofluid sensor according to the use environment.

Figure 4 is a graph showing the sensitivity measurement results for the stretching mode according to the ultrasonic dispersion energy of an embodiment of the present invention.

The degree of ultrasonic dispersion energy was expressed as the energy applied per unit volume (J/s*mL), and the ultrasonic dispersion energy was obtained by giving a difference in the fabrication volume of each nanofluid (A). Then, stretching was applied to the sensor at 50, 100, 150, and 200% using the initial canal length. The performance of each sensor was evaluated by calculating the value of the resistance change according to the strain (ε) condition as the sensitivity (Gauge factor, GF). The calculation formulas for strain and gauge factor are shown in Equations 1 and 2 below.

,

는 각각 유관의 초기 길이와 길이 변화를 의미하며,

,

는 각각 센서의 저항 변화와 초기 저항을 의미한다. Gauge factor의 기계적 의미는 Strain의 양과 저항 변화의 양에 관한 상대적 비율을 뜻한다. 따라서 동일 Strain 조건에서 높은 Gauge factor를 갖는다는 것은 해당 조건에서 Sensor가 보다 큰 저항 변화의 폭을 가지며 민감히 반응한다는 것이다. 이것은 실제 활용에서 양가적 의미를 가지는데, 해당 Strain이 감지하고자 하는 범위에서 벗어나는 경우 Gauge factor가 높을수록 센서가 민감히 반응하며 측정에 있어 오히려 Noise를 얻을 수 있다. 반대로 해당 Strain이 감지하고자 하는 범위일 경우 Gauge factor가 높을수록 센서가 민감히 반응하며 측정에 있어서 높은 해상도를 얻을 수 있다.here,

,

denotes the initial length and length change of the duct, respectively,

,

denotes the resistance change and initial resistance of the sensor , respectively. The mechanical meaning of the gauge factor means the relative ratio between the amount of strain and the amount of resistance change. Therefore, having a high gauge factor under the same strain condition means that the sensor responds sensitively with a larger range of resistance change under that condition. This has ambivalent meaning in actual use. If the strain is out of the range to be detected, the higher the gauge factor, the more sensitively the sensor reacts, and rather noise can be obtained in measurement. Conversely, if the corresponding strain is within the range to be detected, the higher the gauge factor, the more sensitively the sensor responds and the higher resolution can be obtained in measurement.

Equation 1.

Equation 2.

As with the principle mentioned above, it can be confirmed that the distance between particles increases as the stretching strain increases, and the gauge factor increases at the same time. In particular, when a stretching strain of 150% or more is applied, the distance between particles becomes excessively large due to the relatively high cross-section reduction and length increase, resulting in graphene oxide-based nanofluids with dispersion energy of 0.1578, 0.2370, and 0.4738 J/s*mL (A) It can be seen that the Gauge factor increases sensitively to the increase in the inter-particle distance. In this case, the gauge factors of all graphene oxide-based nanofluids (A) have average values within a standard deviation range. On the other hand, when a stretching strain of 100% or less is applied, the graphene oxide-based nanofluids (A) have different Gauge factors depending on the degree of ultrasonic dispersion energy. The higher the ultrasonic dispersion energy, the more the colloidal structure in the in-plain cut state is obtained. In this case, the nanoparticles have a relatively high gauge factor for related pipe deformation due to the small particle size and high degree of freedom of dynamic motion of the nanoparticles along the flow. .

As a result, according to the wearable sensor according to an embodiment of the present invention, the ultrasonic dispersion energy is differently applied to the conductive particles according to the deformation range of the object undergoing deformation behavior, thereby resulting in a peeled state having a first area with respect to a plane ( It is configured to select and use any one of a colloidal structure in a delaminated state and a colloidal structure in an in-plane cut state having a second area smaller than the first area.

In this embodiment, in an operation with a large deformation range and an external stimulation environment, a colloidal structure in a delaminated state (intermediate structure b in FIG. While gaining sensitivity, it is possible to reduce the noise of small deformation , and on the contrary, in an operation with a relatively small deformation range and an external stimulation environment, the colloidal structure in the in-plane cut state (right structure in FIG. It has the advantage of being able to be configured to have high sensitivity to the target environment by using a colloidal structure with two areas).

Meanwhile, FIG. 5 is a perspective view of a nanofluid sensor according to another embodiment of the present invention.

The flexible substrate portion 100 employed in this embodiment includes a center deformable portion 101, an electrode connection portion 102, and a tapered portion 103.

The central deformable portion 101 is a portion at the center of the fluid accommodating portion and has a first width, and the electrode connection portions 102 extend from both side edges of the central deformable portion 101, respectively, and the central deformable portion It is formed with a second width greater than the width of (101), and the tapered portion 103 is interposed between the center deformable portion 101 and each electrode connection portion 102 in a shape in which the width gradually increases, The nanofluid is configured to be accommodated only in the central deformable portion 101 and the tapered portion 103 .

In this embodiment having such a configuration, the fluid accommodating portion and the electrode connection portion are configured to have different thicknesses so that stress due to deformation of the flexible substrate 100 due to external stimulation is concentrated in the fluid accommodating portion, thereby sensitively detecting external stimuli. It is possible to expect the advantage of securing structural safety as well as being able to do so.

6 is a perspective view of a nanofluid sensor according to another embodiment of the present invention.

--> In the case of other embodiments, it was determined that there was no need to add anything in particular.

Unlike the previous embodiments, this embodiment is coupled to each electrode connection part 202, and a through hole through which each electrode passes is formed and a curable polymer 300 formed of a thermosetting resin material to suppress deformation is further added. Including, the stress for the deformation of the flexible board portion is more concentrated in the fluid receiving portion, resulting in the advantage of being robust and having optimal sensitivity.

Although various embodiments of the present invention have been described above, this embodiment and the accompanying drawings only clearly show some of the technical ideas included in the present invention, and are included in the specification and drawings of the present invention. It will be apparent that all modified examples and specific embodiments that can be easily inferred by those skilled in the art within the scope of the technical idea are included in the scope of the present invention.

1: flexible board part 2: fluid accommodating part
3: Electrode A: Nanofluid

Claims (8)

By utilizing fluid, it is possible to sensitively detect the user's motion or deformation caused by external stimuli.
It is coupled to a wearable device or an object that undergoes the same deformable behavior as the user's body and is deformed according to the object's behavior, and is formed of a material that can be deformed and restored to its original shape after deformation. ;
a fluid accommodating part formed in the form of a channel capable of accommodating nanofluids containing conductive nanoparticles inside the flexible substrate part; and
A pair of electrodes, one side of which is inserted into the channel and electrically connected to the nanofluid, and the other side is exposed to the outside of the flexible substrate and is electrically connected to an external device. According to claim 1,
The channel of the fluid receiving portion is formed in a shape penetrating the center of the flexible substrate portion,
The nanofluid sensor, characterized in that each of the electrodes is configured to be inserted into both edges of the channel to be electrically connected to the nanofluid accommodated in the channel and to close the open portion of the channel. According to claim 1,
The nanofluid sensor characterized in that the nanofluid accommodated in the fluid accommodating part is formed by ultrasonic dispersion treatment of conductive particles. According to claim 3,
The conductive particle is a nanofluid sensor, characterized in that any one or a combination of carbon-based nanoparticles of graphene, graphene oxide, carbon nanotubes and magnetic nanoparticles of iron oxide, copper oxide, aluminum oxide series. According to claim 3,
A colloidal structure in a delaminated state having a first area with respect to a plane and a second area smaller than the first area by applying the ultrasonic dispersion energy differently to the conductive particles according to the deformation range of the object undergoing the deformation behavior. A nanofluidic sensor characterized in that it is configured to select and use any one of the colloidal structures in an independent particle dispersion state (in-plane cut state) having two areas. According to claim 1,
The flexible substrate includes a central deformable part having a first width and a pair of electrode connecting parts each extending from both side edges of the central deformable part and having a second width greater than the width of the central deformable part. A nanofluidic sensor characterized in that to do. According to claim 6,
The flexible substrate part further comprises a tapered part interposed between the central deformable part and each electrode connection part in a shape gradually increasing in width,
The nanofluid sensor, characterized in that configured to be accommodated only in the central deformation portion and the tapered portion. According to claim 6,
The nanofluid sensor further comprises a curable polymer coupled to each of the electrode connection parts, having through-holes through which each of the electrodes pass, and being formed of a thermosetting resin material to suppress deformation.

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