KR101943519B1 - Composite, manufacturing method thereof, and flexible temperature sensor including the composite - Google Patents

Abstract

The present invention relates to a composite, a manufacturing method thereof, and a temperature sensor formed with the composite, wherein the composite comprises: polyvinylidene fluoride (PVDF); a reduced graphene oxide (rGO) mixed in the PVDF; and a semi-crystalline polymer. Therefore, the composite can realize a supersensitive temperature sensor as resistance is sensitively changed in accordance with a temperature.

Description

TECHNICAL FIELD The present invention relates to a composite material, a manufacturing method thereof, and a flexible temperature sensor including the composite material.

The present invention relates to a composite material, a manufacturing method thereof, and a flexible temperature sensor including the composite material, and more particularly, to a flexible temperature sensor including a polyvinylidene fluoride (PVDF) having a ferroelectric property, a reduced graphene oxide And polyolefin oxide (PEO) which is a semi-crystalline polymer, a method for producing the composite material, and a temperature sensor made of a composite material. The composite material has a characteristic that resistance changes according to thermal stimulation and thus can be utilized as a temperature sensor, and can be used as an artificial electronic skin, a biosensor, and the like.

Composite material composed of PVDF and rGO has a characteristic that resistance changes according to temperature by the effect of graphene's negative temperature coefficient of temperature (NTC). PVDF is a material forming a polymer matrix, and rGO is a conductive material and a temperature sensing material. When the composite material is heated, the electrical conductivity of the rGO dispersed in the polymer matrix is increased to decrease the resistance, which can be used to detect the temperature change. Therefore, a temperature sensor can be manufactured using such a composite material.

Polymer materials are generally inexpensive and have properties that are easier to process and handle than metal or ceramic materials. As a result, the frequency of use of polymer materials is gradually increasing. However, polymers do not have properties such as electric conduction, heat conduction, and magnetism, and therefore, applicable fields are limited. In recent years, various composite materials have been made by adding a filler having properties to be imparted to the polymer matrix to overcome such disadvantages.

As one example, a conductive composite material produced by adding an electrically conductive filler to an insulator polymer is disclosed. As the electrically conductive filler, carbon black, carbon nanotubes, graphene or metal particles can be used.

However, in the case of currently developed composite materials, there is a problem that the filler particles added to the polymer matrix over time become entangled with each other, and the characteristics are deteriorated by moving below the liquid matrix.

Further, as the amount of the filler added to the polymer matrix is increased, the characteristics of the composite material become similar to the intrinsic properties of the filler, but conversely, the inherent characteristics of the matrix may disappear, It is necessary to make a material by mixing an amount that can be realized.

Temperature sensors implemented in PVDF and rGO composites can be used as artificial electronic skin. Therefore, the temperature sensing sensitivity due to the thermal stimulation should be high in a temperature range similar to the skin temperature.

Also, it should not be affected by mechanical stimuli such as pressure and bending.

Korean Patent Laid-Open No. 10-2016-0109266 relates to a reduced oxidized graphene / PVDF composite material, a method for manufacturing the same, and a thermistor sensor using the same, and relates to a composite material including PVDF and oxidized graphene for a thermistor sensor .

The present invention has been made to solve the problems of the prior art, and it is an object of the present invention to provide a composite material capable of improving the sensitivity to temperature sensing by adding a semi-crystalline polymer to a composite material composed of PVDF and rGO, The present invention relates to a flexible temperature sensor including a temperature sensor.

Specifically, a composite material having a temperature sensitive sensitivity characteristic of 10 times or more as compared with a composite material made of conventional PVDF and rGO by adding PEO, which is a semi-crystalline polymer, into a composite material composed of conventional PVDF and rGO, A flexible temperature sensor including a material can be provided.

The composite material according to the present invention may include polyvinylidene fluoride (PVDF); Reduced oxidized graphene (rGO) mixed uniformly in the PVDF; And a semi-crystalline polymer uniformly mixed in the PVDF and the rGO.

The semi-crystalline polymer may be polyethylene oxide (PEO).

Wherein the composite material comprises PVDF 100- (x + y) wt%, rGO x wt% and PEO y wt%, wherein x is from 1 to 2 and y is from 20 to 30.

The molecular weight of the PEO may range from 1k to 4k.

Wherein the composite material comprises a temperature sensitive color layer on one side and the temperature responsive color layer comprises a material selected from the group consisting of polydimethylsiloxane (PDMS); And at least one temperature sensitive color changing pigment uniformly mixed in the PDMS.

The temperature sensor according to the present invention comprises the composite material; And electrodes disposed parallel to the left and right of the upper portion of the composite material.

Depending on the molecular weight of the semi-crystalline polymer, the temperature sensing sensitivity of the temperature sensor may be different from the higher temperature range.

The temperature sensor may have a film form.

Wherein the composite material comprises a temperature sensitive color change layer coated on one side and the temperature sensitive color change layer comprises at least one temperature sensitive color change pigment uniformly mixed in PDMS and PDMS, It can output color due to pigment.

A composite material manufacturing method according to the present invention includes: a first mixing step of mixing PVDF with a solvent; A second mixing step of mixing rGO with the mixture mixed in the first mixing step; A third mixing step of mixing PEO with the mixture mixed in the second mixing step; And curing the mixed mixture in the third mixing step by evaporating the solvent of the mixed mixture in the third mixing step.

The solvent may be dimethylformamide (DMF).

In the first mixing step, the PVDF is mixed with 100- (x + y) wt%, the rGO is mixed with x% by weight in the second mixing step, y% by weight is mixed with the PEO in the third mixing step , X may be 1 to 2, and y may be 20 to 30.

And coating a temperature sensitive coloring layer on one side of the composite material produced by curing the mixture.

According to the present embodiment, the temperature can be sensed more sensitively (about 10 times or more) than the conventional composite material made of PVDF and rGO.

The temperature sensor using the composite material according to the present invention can detect a small temperature change of 0.1 ° C.

In addition, the composite material according to one embodiment of the present invention has improved durability as compared with the conventional composite material.

In addition, the composite material and the temperature sensor using the composite material according to an embodiment of the present invention exhibit a constant resistance change with respect to a temperature change even under a mechanical stimulus such as pressure or bending and a plurality of mechanical stimulation conditions, There is an advantage that measurement can be done.

In addition, the composite material according to an embodiment of the present invention further includes a temperature sensitive coloring pigment. Therefore, it is possible to output a change in temperature as a change in hue, thereby enabling the measurer to visually observe a change in temperature.

FIG. 1 is a structural view of a composite material according to an embodiment of the present invention.
2 is a graph showing a change in resistance of a composite material with respect to the molecular weight of rGO contained in the composite material according to an embodiment of the present invention.
FIG. 3 is a graph showing a resistance change of a composite material with respect to a concentration of rGO contained in a composite material according to an embodiment of the present invention.
4 is an SEM image of composite materials containing different concentrations of rGO in a composite material according to an embodiment of the present invention.
FIG. 5 is a graph illustrating physical properties of a composite material according to a variation of concentration of PEO according to an embodiment of the present invention. FIG.
6 is a graph showing a minimum temperature sensing range of a composite material containing PEO at a concentration of 30 wt% in a composite material according to an embodiment of the present invention.
7 is a graph of temperature sensing sensitivity measurements for mechanical stimulation of a composite material in accordance with an embodiment of the present invention.
FIG. 8 is a graph showing a temperature sensing sensitivity measurement for a bending condition of a composite material according to an embodiment of the present invention.
9 is an image showing a temperature sensing characteristic of a composite material coated with a temperature sensitive coloring layer in a composite material according to an embodiment of the present invention.
10 is a flowchart briefly showing a method of manufacturing a composite material according to an embodiment of the present invention.

Hereinafter, a composite material according to an embodiment of the present invention, a manufacturing method thereof, and a flexible temperature sensor including the composite material will be described in detail with reference to the accompanying drawings. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing. In the accompanying drawings, the dimensions of the structures are enlarged to illustrate the present invention in order to clarify the present invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a part or a combination thereof is described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

1 is a configuration diagram of a composite material according to the present embodiment.

Hereinafter, one embodiment of the present invention will be described with reference to FIG.

The temperature sensing mechanism using the composite material according to an embodiment of the present invention utilizes the Negative Temperature Coefficient of Temperature (NTC) effect of graphene composing composite material composed of PVDF and rGO. The resistance of composites made of PVDF and rGO varies with temperature. The resistance value of composite material composed of PVDF and rGO is decreased by the NTC effect of rGO when the temperature is increased. By using this characteristic of the composite material, the temperature change can be detected.

The present invention relates to a composite material having a temperature sensitivity higher than that of a conventional composite material made of PVDF and rGO by tens of times. To a composite material containing a semi-crystalline polymer mixed with a conventional composite material

Referring to FIG. 1, when the temperature is changed by heating, changes in constituent materials in the composite material according to an embodiment of the present invention can be grasped. The composite material according to one embodiment of the present invention comprises a polymer matrix 102, a conductive filler 104, and a semi-crystalline polymer 106. Illustratively, the polymer matrix 102 may be PVDF, the conductive filler 104 may be rGO (reduced graphene oxide), and the semi-crystalline polymer 106 may be PEO. The composite material according to an embodiment of the present invention has a structure in which rGO, which is the conductive filler 104, and PEO, which is one of the semi-crystalline polymers 106, are uniformly distributed in the polymer matrix 102

PVDF is a resin in which a hydrogen atom is partially substituted by a hydrogen atom in the molecular structure of an aliphatic hydrocarbon, and has excellent chemical resistance, mechanical, thermal and electrical properties of a fluororesin and high mechanical strength It is possible to impart excellent physical properties to the composite material.

rGO can achieve high withstand voltage strength while having excellent thermal conductivity and electrical conductivity. rGO can exhibit high compatibility in the thermosetting resin and can be added to the polymer matrix to be used as a conductive material and a temperature sensing material.

Composite materials composed of PVDF and rGO have NTC characteristics and can be used as temperature sensing materials, thermistor sensors, and so on.

However, the composite material composed only of PVDF and rGO has a difficulty to be applied to a temperature sensor having a high accuracy due to a low temperature sensitivity because the change of the resistance value according to the temperature is not large. In order to solve this problem, in the present invention, PEO, which is a semi-crystalline polymer 106, is mixed with PVDF and rGO to produce a composite material. PEO is a semi-crystalline polymer that has the property of expanding or contracting in volume depending on temperature. PEO is uniformly distributed in a composite material composed of PVDF and rGO. By this distribution, the temperature sensing sensitivity of composite materials made of PVDF, rGO and PEO can be greatly improved.

Specifically, the semi-crystalline polymer forms a thermodynamic single phase at a temperature higher than the melting point. The crystallinity disappears from the vicinity of the melting point and the particles expand. Specifically, the semi-crystalline polymer starts to expand from below about 20 ° C of the melting point, and it is continuously expanded as the temperature increases.

In the composite material composed of PVDF, rGO and PEO before heating, the rGO (104) sheets and the PEO (106) particles in the matrix 102 are distributed at a certain distance. In particular, although the rGO 104 sheets form a passage through which electrons can move, the sheets are dispersed rather than in contact with each other, so that the electrical conductivity between the sheets is low, and therefore the resistance of the composite material is high.

When a composite material composed of PVDF, rGO and PEO is heated, the PEO particles expand as the temperature increases. The expanded PEO particles 108 may pressurize the surrounding matrix 102 and rGO 104 sheets and increase the contact area of the rGO 104 sheets to change the electrical properties of the composite material. That is, as the composite material is heated, the mobility of electrons through the rGO 104 sheets increases, thereby reducing the resistance of the composite material.

That is, the temperature sensing sensitivity is greatly improved by using the NTC effect of rGO and the expansion and contraction characteristics according to the temperature of PEO compared to the composite material made of PVDF and rGO using only the NTC effect of the conventional rGO.

2 to 9 are experimental examples using composite materials prepared by specifying the concentrations of PVDF, rGO, and PEO, and are not limited to the composition ratios of the composite materials shown in this Experimental Example. , The PVDF may have a composition ratio of 79 wt% to 45 wt%, the rGO may have a composition ratio of 1 wt% to 5 wt%, the PEO may be 20 wt% to 50 wt% , Various composite materials can be produced within this range.

FIG. 2 is a graph showing the resistance change of the composite material with respect to the molecular weight of rGO according to the present embodiment.

Hereinafter, one embodiment of the present invention will be described with reference to FIG.

The semi-crystalline polymer has the property of increasing the melting point as the molecular weight increases. 2, melting point change and temperature sensing mechanism according to molecular weight of PEO constituting a composite material composed of 79 wt% of PVDF, 20 wt% of PEO and 1 wt% of rGO can be confirmed. The composition ratios of PEO, PVDF and rGO are not limited to those shown in Fig. Due to the nature of the semi-crystalline polymer, PEO, the volume change is larger at the melting point near the melting point, so the temperature range at which the temperature can be sensitively sensed may vary depending on the molecular weight. The larger the molecular weight, the higher the melting point.

2, melting point 202 of PEO having a molecular weight of 1 k is about 38 캜, melting point 204 of PEO having a molecular weight of 1.5 k is about 45 캜, melting point 206 of PEO having a molecular weight of 4 k is about 55 캜 . As the molecular weight of PEO increases, the melting point of PEO gradually increases.

Referring to FIG. 2, the resistance change rate of the composite material with temperature is the largest within a temperature range close to the melting point of PEO having a specific molecular weight, and temperature sensing within a temperature range adjacent to the melting point of PEO It can be seen that it is more sensitive.

In composite materials containing PEO having a molecular weight of 4k or more, the resistance decreases with increasing temperature. However, if the molecular weight of PEO exceeds 4k, even if the molecular weight increases, the difference in melting point of PEO is not large , And the molecular weight of the PEO to be mixed with the composite material is preferably 1k to 4k.

In addition, in the case of the composite material according to one embodiment of the present invention, the temperature change from 25 ° C to 60 ° C can be sensed sensitively. In addition, composite materials can be fabricated using PEO with a molecular weight that meets the temperature range that needs to be sensitively sensed, and a temperature sensor with optimized sensing in a specific temperature range can be implemented.

3 is a graph showing the resistance change of the composite material with respect to the concentration of rGO according to the present embodiment.

Hereinafter, one embodiment of the present invention will be described with reference to FIG.

The sensitivity of the temperature sensing of the composite material according to the concentration of rGO (302) shows that the sensitivity of temperature sensing of the composite material varies with the concentration of rGO. Composite materials with the highest temperature sensing sensitivity were composed of PVDF (78wt%), rGO (2wt%) and PEO (20wt%) composites. PVDF (75wt%) composites showed the lowest temperature sensitivity, , rGO (5 wt%) and PEO (20 wt%).

The resistances of PVDF (78wt%), rGO (2wt%) and PEO (20wt%) are compared with those of PVDF (75wt%), rGO (5wt%) and PEO (20wt%). (78wt%), rGO (2wt%) and PEO (20wt%), which are higher than the resistance of the composite material made of PVDF (79wt%) and rGO (1wt% ), The sensitivity of each composite is lower than that of composite material.

That is, it may be desirable to find an appropriate composition ratio of the composite material to produce a composite material having a measurable temperature range required by the user.

According to one embodiment of the present invention, when 20 wt% of PEO is used in the production of a composite material, rGO may be preferably 1 wt% to 5 wt%, and PVDF may be preferably 75 wt% to 79 wt% . The sum of the composition ratios of the composite material composed of PVDF, rGO and PEO is 100% by weight.

Specifically, it is preferable that the concentration of rGO is 1 wt% to 2 wt%. When the rGO concentration is less than 1 wt%, conduction characteristics of the composite material composed of PVDF, rGO and PEO may not be exhibited, I have a problem. When the rGO concentration exceeds 2 wt%, the rGO sheets added to the composite material are not dispersed, and the rGO sheets are completely in contact with each other. As a result, there is a problem that the effect of improving the temperature sensing sensitivity of the composite material made of PVDF, rGO, and PEO is reduced due to the expansion and contraction of the PEO.

4 is an SEM image of the composite material with respect to the concentration of rGO according to the present embodiment.

Hereinafter, one embodiment of the present invention will be described with reference to FIG.

4, the composite material 402 having the highest temperature sensing sensitivity of PVDF (78 wt%), rGO (2 wt%) and PEO (20 wt%) and the PVDF having the lowest temperature sensing sensitivity (75 wt% ), rGO (2 wt%), and PEO (20 wt%) were observed with a scanning electron microscope (SEM) The PEO phase does not appear clearly in the cross section of the composite material 404 made of PVDF (75 wt%), rGO (5 wt%), and PEO (20 wt%), unlike the composite material 402 made of rGO .

If the PEO phase is not clearly visible in the matrix, the temperature sensing sensitivity of the composite may deteriorate due to the small number of PEO particles that can change in volume even as the temperature of the composite increases as the shape of the PEO is not maintained.

That is, the shape-retained PEOs must be uniformly distributed in the matrix to achieve the intended effect in one embodiment of the present invention.

Also, the concentration of rGO may affect the PEO phase present in the matrix, and it may be desirable to add rGO at an appropriate concentration to improve the temperature sensitive sensitivity of the composite.

FIG. 5 is a graph illustrating physical properties of a composite material according to a variation of concentration of PEO according to an embodiment of the present invention. FIG. Hereinafter, one embodiment of the present invention will be described with reference to FIG.

In the production of the composite material according to the present invention, when rGO is 2 wt%, PEO may be 20 wt% to 50 wt%, and PVDF may be 48 wt% to 78 wt%. The total composition ratio is 100% by weight.

A graph 502 showing the temperature sensing sensitivity of a composite material made of PVDF, rGO and PEO according to the concentration of PEO shows that the concentration of PVDF in the composite material ranges from 48% by weight to 78% by weight and PEO in the range from 20% by weight to 50% The composite material having the largest amount of change in resistance with temperature is a composite material in which PEO is added in an amount of 20% by weight to 30% by weight. That is, the composition ratio of PEO in the composite material is preferably 20% by weight to 30% by weight.

When the concentration of PEO is less than 20% by weight, the effect obtained by mixing PEO can not be obtained because the number of PEO particles present in the matrix is small. That is, in the composite material according to an embodiment of the present invention, the PEO is mixed with the rGO in the matrix to uniformly distribute the rGO and the PEO, and then the PEO is expanded to reduce the resistance of the material. If the concentration of PEO is less than 20% by weight, such a mechanism will not work properly. Conversely, when the concentration of PEO exceeds 30 wt%, the form of PEO may not be maintained and may be mixed with the matrix. In this case, when the temperature rises, the PEO particles and the matrix are expanded together to increase the volume of the composite material as a whole. Rather, the distance between the rGO sheets becomes longer, and the resistance may increase. If the PEO particles expand while retaining their shape, they can compress the rGO or matrix around the PEO particles. Thus, the spacing between the rGO sheets is reduced, and consequently, the electrical conductivity can be increased and the resistance can be reduced. However, if the volume of the PEO particles and the matrix are increased together, the spacing between the rGO sheets may be rather distant and the temperature sensitive sensitivity of the composite material made of PVDF, rGO and PEO may be reduced.

Thus, composite materials with good temperature sensitive sensitivity may be preferred for 20 wt% to 30 wt% of PEO and 68 wt% to 78 wt% of PVDF when rGO is 2 wt%. The sum of the composition ratios of the composite material composed of PVDF, rGO and PEO is 100% by weight.

The temperature sensing sensitivity (502) of the composite material composed of PVDF, rGO, and PEO (502) according to the PEO concentration was found to be the most sensitive to the temperature sensing sensitivity of the composite material composed of PVDF (68 wt%), rGO (2 wt%) and PEO High. The temperature sensitive sensitivity of composites composed of PVDF (68 wt%), rGO (2 wt%) and PEO (30 wt%) may be more than 10 times higher than the temperature sensitive sensitivity of composites composed of PVDF and rGO without PEO .

The TCR value (504) indicating the temperature sensing sensitivity of the composite material composed of PVDF (68 wt%), rGO (2 wt%) and PEO (30 wt%) was calculated (504) .

The TCR (Temperature Coefficient of Resistance) is a temperature coefficient of resistance, which can be derived from the following formula, and the unit can be expressed in%.

Also, as a result of analyzing the hysteresis curve 506, it can be confirmed that the resistance value of the composite material changes similarly as the temperature increases or decreases during heating and cooling. That is, it is possible to display the same measurement value both when the temperature increases and when the temperature decreases. In the case of the conventional composite material, there is a problem that the temperature at the time of increasing the temperature differs from the temperature at the time of decreasing the temperature when applied to the temperature sensor. In the composite material according to an embodiment of the present invention, the hysteresis curve showing the change of the resistance value according to the temperature increase and the hysteresis curve showing the change in the resistance value due to the temperature decrease are almost the same.

2 to 9 are experimental examples using composite materials prepared by specifying the concentrations of PVDF, rGO, and PEO, but are not limited to the composition ratios of the composite materials shown in this Experimental Example. As described above, the composite material according to one embodiment of the present invention has a composition ratio of 79 wt% to 68 wt% for PVDF, a composition ratio of 1 wt% to 2 wt% for rGO, and a concentration of PEO of 20 wt% By weight and a composition ratio of 100% by weight. That is, PVDF, rGO, and PEO can vary in a wide range within the above-described numerical ranges. That is, various composite materials can be produced within the above-mentioned numerical range.

That is, the composition ratio of PVDF, rGO and PEO may be PVDF 100- (x + y) wt%, rGO x wt% and PEO y wt%. Where x can be from 1 to 2 and y can be from 20 to 30. The sum of the composition ratios of the composite material composed of PVDF, rGO and PEO is 100% by weight.

6 is a graph showing a minimum temperature sensing range measurement of a composite material composed of PVDF (68 wt%), rGO (2 wt%) and PEO (30 wt%) of the composite materials according to the present embodiment.

Hereinafter, one embodiment of the present invention will be described with reference to FIG.

As a result of the experiment in FIG. 5, the resistance value change of the composite material having PVDF (68wt%), rGO (2wt%) and PEO (30wt%) having the highest temperature sensing sensitivity was measured in real time 602), and it is possible to detect a temperature changing in the range of 0.1 ° C to 1 ° C.

The composite material made of PVDF (68 wt%), rGO (2 wt%), and PEO (30 wt%) was measured at a temperature of 0.1 DEG C It can be seen that the change can be detected. According to the graph 604, as the temperature is decreased by 0.1 ° C, the resistance of composites made of PVDF (68 wt%), rGO (2 wt%) and PEO (30 wt%) is decreasing to an identifiable level. That is, even if the temperature is changed by 0.1 ° C, the difference in resistance value is distinct and the change of 0.1 ° C can be distinguished. Accordingly, when using the composite material according to one embodiment of the present invention, it is possible to realize a temperature sensor that can detect a change of 0.1 ° C and greatly improve the temperature sensitivity.

The composite material according to one embodiment of the present invention, which can detect a change in temperature between 32 ° C and 33 ° C and 0.1 ° C as a temperature of the skin surface of a human, can be applied to artificial skin. That is, if a composite material according to an embodiment of the present invention is applied to a material of an artificial skin, artificial skin having a considerable temperature sensitivity can be realized.

7 is a graph of temperature sensing sensitivity measurements for mechanical stimulation of a composite material in accordance with an embodiment of the present invention.

Hereinafter, one embodiment of the present invention will be described with reference to FIG.

When the composite material according to this embodiment is used as a temperature sensor, the response to mechanical stimulation such as pressure and bending is an important consideration in independent temperature sensing.

The temperature or pressure condition that can be sensed by the temperature sensor made of the composite material according to this embodiment is different according to the attachment form 701 of the electrode attached to the composite material. It is preferable to arrange the electrodes parallel to the left and right of the upper portion of the composite material so that the temperature sensor according to the present embodiment reacts only with the temperature under the conditions that the pressure and the temperature are changed. A graph 702 showing the response of the temperature sensor to the pressure according to the arrangement of the electrodes shows that the response to the pressure of the sensor varies depending on the arrangement of the electrodes. Unlike a temperature sensor made up of electrodes arranged in parallel, a temperature sensor made up of electrodes vertically arranged on the upper and lower surfaces of the composite material has different resistances when the pressure changes.

That is, it is preferable that the electrode attached to the composite material is attached parallel to the left and right of the upper portion of the composite material so that only the temperature change except the pressure is detected through the temperature sensor according to the present embodiment.

The temperature sensor according to this embodiment may be in the form of a film-like composite material and an electrode attached with a copper tape. The copper tape has excellent electric conductivity and does not cause a problem of deteriorating the performance of the temperature sensor.

In addition, the electrode and the composite material can be adhered to each other by silver paste, thereby reducing the contact resistance between the composite material and the electrode.

As a result of measuring the temperature sensing sensitivity by varying the pressure while maintaining the temperature sensor according to the present embodiment at a constant temperature (703), it can be confirmed that the resistance of the temperature sensor is kept constant under the condition that the pressure is changed.

That is, the temperature sensor according to the present embodiment can detect temperature change only.

When a load is applied to the temperature sensor using an object capable of changing the temperature of the temperature sensor according to the present embodiment, the resistance can be increased or decreased by the temperature.

For example, when a part of the body is touched by the temperature sensor, the resistance may change due to the temperature change.

While measuring the resistance change of the temperature sensor according to the load (704), the load can be measured through the electronic balance. The temperature sensing sensitivity of the temperature sensor according to the present embodiment is measured by a load of 100 g, 200 g, and 500 g (705). As a result, a signal corresponding to a resistance change is generated at the moment when the load is applied. No signal changes occur while the load is applied to the temperature sensor.

In addition, the resistance is changed at the instant of removing the load applied to the temperature sensor, and a signal is generated.

That is, the instant when the load is applied to the temperature sensor and the moment when the load is removed can be known through the generated signal.

For example, when the finger is touched by the temperature sensor, the resistance of the temperature sensor may be changed by the heat of the finger.

In the graph 706 of the resistance change when the temperature sensor is touched with a finger, it can be seen that the temperature of the temperature sensor rises and the resistance decreases as soon as the temperature sensor is touched. While the temperature sensor is being touched, the temperature of the temperature sensor is maintained and no resistance change occurs. When the touch of the temperature sensor is interrupted, the temperature sensor starts to cool, and accordingly the resistance of the temperature sensor gradually increases. When the temperature sensor is restored to its pre-touch temperature, the resistance can be equal to the resistance before touching.

That is, the temperature sensor according to the present embodiment can detect whether or not it is touched through the temperature change.

FIG. 8 is a graph showing a temperature sensing sensitivity measurement for a bending condition of a composite material according to an embodiment of the present invention.

Hereinafter, one embodiment of the present invention will be described with reference to FIG.

As a result of measuring the temperature sensing sensitivity of the composite material according to the present embodiment according to the presence or absence of the substrate (802), it can be seen that the composite material without the substrate does not change resistance to bending. In the composite material including the substrate, stress may be concentrated between the substrate and the composite material due to the substrate subjected to bending stress, resulting in a resistance change.

As a result of measuring the sensitivity of the temperature sensing in the bent state of the composite material according to the present embodiment (804), it is found that the rate of resistance change according to the temperature when the composite material is not bent and the degree of bending is 3 mm to 14 mm is similar have.

In addition, the temperature sensing sensitivity of the composite material according to the number of bending times was measured (806), and the resistance change rate with respect to the temperature of the composite material having the bending stimulus of 0 to 1,000 times was similar.

That is, the composite material according to the present embodiment is not affected by mechanical stimulation. Also, the rate of change in resistance with temperature change can be kept constant, and the durability against physical stimulation is excellent.

9 is an image showing a temperature sensing characteristic of a composite material coated with a temperature sensitive coloring layer in a composite material according to an embodiment of the present invention.

The composite material according to an embodiment of the present invention may further include a discoloration layer whose color changes depending on the temperature. In other words, the temperature can be visually displayed by coating the composite material with a discoloration layer including a dye that makes a specific color appear at a specific temperature.

That is, the composite material according to an exemplary embodiment of the present invention may further include a temperature sensitive color layer coated on one side thereof. The temperature responsive discoloration layer may comprise polydimethylsiloxane (PDMS) and at least one temperature sensitive discolouration dye mixed in the PDMS. Here, the temperature sensitive coloring dye has a characteristic in which the color changes depending on the temperature.

For example, the composite material 902 including a temperature-sensitive coloring layer made of one temperature-sensitive color-changing pigment may change color when the temperature of the temperature-sensitive color-changing pigment reaches a temperature at which the color changes.

Further, in the composite material 904 including the temperature sensitive coloring layer composed of two or more temperature sensitive coloring dyes, the sensible temperature range or the number of temperature sensing can be changed depending on the number of added coloring dyes.

The composite material 906 may be made of a temperature sensing film and laminated thinly on one side of the temperature sensor, and may be applied to an artificial electronic skin, a biosensor, and the like.

10 is a flowchart briefly showing a method of manufacturing a composite material according to an embodiment of the present invention.

Each step of the manufacturing method can be performed by an apparatus for producing a composite material.

According to FIG. 10, the first mixture may be prepared through mixing (1020) PVDF with the solvent. The solvent here is a highly soluble solvent for PVDF, rGO and PEO so that both PVDF, rGO and PEO can be uniformly mixed. For example, such a solvent may be dimethylformamide (DMF).

A second mixture may be prepared through mixing rGO to the first mixture (1040), and a third mixture may be prepared (1060) by mixing the second mixture with PEO.

By sequentially mixing PVDF, rGO, and PEO in a solvent, rGO and PEO can be uniformly distributed in the matrix without any aggregation or sinking.

The composition ratio of PVDF, rGO and PEO mixed in the solvent may be PVDF 100- (x + y) wt%, rGO x wt% and PEO y wt%. Where x can be from 1 to 2 and y can be from 20 to 30. The sum of the composition ratios of the composite material composed of PVDF, rGO and PEO is 100% by weight.

If the concentration of rGO is less than 1% by weight, the electrical conductivity of the composite material may be low and the temperature sensing may not be performed. When the concentration of rGO is more than 2% by weight, the rGO and the matrix may be combined so that the rGO phase can be mixed without any apparent appearance. Therefore, the electrical conductivity of the composite material produced may be lowered.

When the concentration of PEO is less than 20% by weight, even when the temperature of the composite material is raised, the number of expanded PEO particles is small. When PEO is more than 30% by weight, PEO and PVDF can be combined and mixed. When the temperature is raised, the composite matrix and the PEO produced may be simultaneously expanded to increase the total volume. Therefore, the distance between the rGO sheets distributed in the matrix is increased, and the resistance of the composite material is increased. Through step 1080 of evaporating the solvent of the third mixture, the composite material can be prepared by evaporating the DMF and curing the mixture. The composite material may be in the form of a film and may be easily attached to a part of the body.

The temperature responsive coloring layer may be coated on one surface of the composite material according to the present embodiment. The temperature responsive discoloration layer may comprise polydimethylsiloxane (PDMS) and at least one temperature sensitive discoloration dye, and the temperature sensitive discoloration dye may be uniformly distributed within the PDMS.

The composite material coated with the temperature sensitive color change layer can show the result of temperature sensing by changing electrical characteristic and color change. That is, the user can know the temperature change numerically and visually.

The thickness of the temperature sensor made of composite material according to an embodiment of the present invention may be less than 50um. Accordingly, the manufactured temperature sensor has a flexible characteristic and can be applied to a wearable device.

The description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features presented herein.

102: Matrix
104: Conductive filler
106: Semi-crystalline polymer (solid)
108: a semi-crystalline polymer (molten)
200: Graph showing melting point of composite material according to molecular weight of PEO
202: Graph showing melting point of composite material containing PEO of 1k molecular weight
204: Graph showing melting point of composite material containing PEO of 1.5k molecular weight
206: Graph showing melting point of composite material containing PEO of molecular weight 4k
300: Graph of resistance change of composite material to rGO concentration
302: Graph showing sensitivity of temperature sensing of composite materials according to rGO concentration
304: Graph showing resistance change of composite material with rGO concentration
400: SEM image of composite material for rGO concentration
402: SEM image of composite material composed of PVDF (78 wt%), rGO (2 wt%) and PEO (20 wt%)
404: SEM image of composite material consisting of PVDF (75 wt%), rGO (5 wt%) and PEO (20 wt%)
500: Graph of physical properties of composite material with PEO concentration
502: Temperature Sensitivity Sensitivity Graph for Composites with PEO Concentration
504: TCR graph of composite material consisting of PVDF (68 wt%), rGO (2 wt%) and PEO (30 wt%)
506: Hysteresis graph of composite material composed of PVDF (68 wt%), rGO (2 wt%) and PEO (30 wt%)
600: Minimum temperature sensing range measurement graph of composite material composed of PVDF (68 wt%), rGO (2 wt%) and PEO (30 wt%)
602: Resistance of a composite material made of PVDF (68 wt%), rGO (2 wt%) and PEO (30 wt%) was measured at 0 캜 to 175 캜
604: The minimum sensing temperature range of composite material composed of PVDF (68 wt%), rGO (2 wt%) and PEO (30 wt%) was measured in the range of 32 캜 to 40 캜
700: Temperature Sensitivity Sensitivity Graphs and Images for Mechanical Stimulation of Composites
701: An image showing the arrangement of electrodes
702: graph showing resistance change amount to pressure according to arrangement type of electrodes and whether or not PEO is added
703: Graph showing the temperature sensing sensitivity while increasing the pressure from 0 kPa to 30 kPa while the composite material is maintained at a constant temperature in the range of 20 to 40 캜
704: An image that measures load and resistance change by applying a load to a composite material
705: Graph showing resistance change during loading and removal of composite material
706: Graph showing the resistance change of a composite material while being touched with a finger
715: Signal change when applying pressure to composite material
725: Signal changes when pressure is removed from composite material
800: Temperature Sensitivity Sensitivity Graph for Composite Bending
802: The sensitivity of temperature sensing to the bending of the composite is measured according to the presence of the substrate
804: Temperature Sensitivity Sensitivity Measured with Composite Bending
806: Sensitivity of temperature sensing of composite material with the number of bending times
900: Image showing the temperature sensing characteristics of a composite material including a temperature sensitive color layer
902: A composite material coated with a temperature sensitive color-changing layer containing PDMS and one temperature-sensitive coloring pigment
904: PDMS and a composite material coated with a temperature sensitive color-changing layer consisting of two or more temperature sensitive coloring pigments
906: Electrical and color change measurement results of composite materials including temperature sensitive color change layer
1000: Composite material manufacturing method

Claims (13)

Polyvinylidene fluoride (PVDF);
Reduced oxidized graphene (rGO) mixed uniformly in the PVDF; And
And a semi-crystalline polymer uniformly mixed in the PVDF and the rGO,
Coated on one side with a temperature sensitive color change layer,
Composite material. The method according to claim 1,
The semi-crystalline polymer is polyethylene oxide (PEO)
Composite material. 3. The method of claim 2,
In the composite material,
PVDF 100- (x + y) wt.%, RGO x wt.% And PEO y wt.%,
X is 1 to 2,
Y is from 20 to 30,
Composite material. 3. The method of claim 2,
Wherein the molecular weight of the PEO is 1k to 4k,
Composite material. The method according to claim 1,
Wherein the temperature-sensitive color change layer comprises:
Polydimethylsiloxane (PDMS); And
And at least one temperature sensitive color changing pigment uniformly mixed in the PDMS.
Composite material. The composite material of claim 1; And
And electrodes disposed parallel to the left and right of the composite material top.
temperature Senser. The method according to claim 6,
Wherein the temperature sensing sensitivity of the temperature sensor is different according to the molecular weight of the semi-crystalline polymer,
temperature Senser. The method according to claim 6,
The temperature sensor has a film form,
temperature Senser. The method according to claim 6,
Wherein the temperature responsive coloring layer comprises at least one temperature sensitive color changing pigment uniformly mixed in PDMS and PDMS,
Wherein the temperature sensor outputs the measured temperature as a color due to the coloring matter,
temperature Senser. A first mixing step of mixing PVDF in a solvent;
A second mixing step of mixing rGO with the mixture mixed in the first mixing step;
A third mixing step of mixing PEO with the mixture mixed in the second mixing step;
Evaporating the solvent of the mixed mixture in the third mixing step to cure the mixed mixture in the third mixing step; And
And coating a temperature sensitive coloring layer on one side of the composite material prepared by curing the mixture.
Composite material manufacturing method. 11. The method of claim 10,
The solvent is dimethylformamide (DMF)
Composite material manufacturing method. 11. The method of claim 10,
In the first mixing step, the PVDF is mixed with 100- (x + y) wt%
Mixing rGO by x% by weight in the second mixing step,
Mixing the PEO in y wt% in the third mixing step,
X is 1 to 2,
Y is from 20 to 30,
Composite material manufacturing method. 11. The method of claim 10,
In the step of coating the temperature-sensitive color changing layer,
Said temperature responsive coloring layer comprising at least one temperature sensitive color changing pigment uniformly mixed in PDMS and PDMS,
Composite material manufacturing method.

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