KR101053196B1 - Bidirectional temperature sensitive sensor and its manufacturing method - Google Patents

Abstract

The present invention relates to a bidirectional temperature sensitive sensor using a unidirectional shape memory polymer. Bidirectional temperature sensitive sensor according to the present invention It includes a unidirectional shape memory polymer and a tension feeder coupled to the unidirectional shape memory polymer to supply a tension of a certain size, wherein the unidirectional shape memory polymer coupled to the tension supply is reversible in length with temperature change It is characterized by being changed.

The bidirectional temperature sensitive sensor of the present invention is reversibly changed in length according to the change in temperature, and has excellent processability, and thus can be applied to various fields such as actuators and artificial muscles.

Unidirectional shape memory polymer, bidirectional shape memory behavior, temperature sensitive sensor, elastic supply body

Description

Thermo-mechanical sensor showing two-way shape memory behavior and method for manufacturing technique

The present invention relates to a bidirectional temperature sensitive sensor using a unidirectional shape memory polymer. Specifically, the present invention relates to a bidirectional temperature sensitive sensor that can be reversibly changed the length of the unidirectional shape memory polymer in response to external temperature changes.

Shape memory refers to the restoration of the original shape by a certain stimulus after the material of a certain shape is changed by an external force. Shape memory can be largely divided into unidirectional shape memory and bidirectional shape memory. One-way shape memory means that an object of a certain shape can be restored to its original shape by a constant magnetic pole after the shape is changed by an external force, but the shape does not change again in the reverse direction. On the contrary, bidirectional shape memory means that shape change in two directions can be reversibly made by a constant magnetic pole.

1 (a) and (b) are diagrams for explaining the concepts of unidirectional shape memory and bidirectional shape memory, respectively. Referring to (a) of FIG. 1, the unidirectional shape memory material may recover its original shape by heating the deformed shape material, but may not recover its shape again by subsequent cooling. Referring to (b) of FIG. 1, the bidirectional shape memory material may be reversibly changed in shape as the heating and cooling are repeated.

A representative material having a shape memory effect is a shape memory alloy. The shape memory effect of shape memory alloys is due to structural changes called martensitic deformation. Shape memory alloys are used in medical applications such as vascular stents, medical guide wires, or orthodontic wires to artificially expand blood vessels, vibration dampers, pipe connections, electrical joints, thermostats, etc. It is applied to various fields such as an actuator, an eyeglass frame or a bra under wire. However, shape memory alloys are relatively expensive, and additional processes or devices are required to give a bidirectional shape memory effect. Therefore, there are limitations in the field of use and related markets.

Another material having a bidirectional shape memory effect is a liquid crystal elastomer. Liquid crystal elastomer is a material that exhibits a permanent bidirectional shape memory behavior using the mechanical properties of the polymer network and the anisotropy of the liquid crystal. However, liquid crystal elastomers have problems of practical use and industrialization due to instability of molding materials due to incomplete crosslinking, processing complexity, and high cost.

Bidirectional shape memory materials are used in industrial applications such as flow control valves or switch elements. Korean Laid-Open Patent Publication No. 2006-128358, which relates to a flow control valve, uses a shape memory alloy to change the elastic force of the shape memory alloy according to the temperature of the fluid, and thus the opening and closing of the opening and closing opening due to the change of the repulsive force against the hydraulic pressure. Disclosed is a flow regulating valve for generating a gas. However, since the present invention uses the shape memory alloy, as described above, the production cost is high and the deformation recovery rate is relatively low.

Korean Patent Laid-Open Publication No. 2007-106268, which is a prior art document relating to a switch element using a shape memory material, is a first bimetal disk in which two kinds of metal pieces having different expansion coefficients are bonded to each other and the metal pieces having small expansion coefficients are bent when sensing a temperature above a certain temperature. And two kinds of metal pieces having different expansion coefficients are joined together, and the metal pieces having small expansion coefficients of the first bimetal disc face each other. Disclosed is a power supply interrupting device comprising a second bimetal disk in electrical contact with and in contact therewith. However, the bimetal used in the power supply shutoff device has a problem in that the deformation in the bending direction is difficult and the deformation in the longitudinal direction is difficult, thereby limiting the application field.

The first object of the present invention is to provide a temperature sensitive sensor capable of bidirectional shape memory behavior using a unidirectional shape memory polymer and a tension supply.

The second object of the present invention is to provide an actuator and artificial muscle using the bidirectional temperature-sensitive sensor.

A third object of the present invention is to provide a method of manufacturing the bidirectional temperature sensitive sensor.

In order to solve the first problem, the present invention provides a bidirectional temperature sensitive sensor comprising a tension supply for supplying a tension of a certain size is coupled to the one-way shape memory polymer and one-way shape memory polymer. At this time, the unidirectional shape memory polymer coupled to the tension supply is characterized in that its length is changed bidirectionally with temperature change.

According to one embodiment of the present invention, the present invention may include a unidirectional shape memory polymer may include a soft segment and a hard segment.

According to another embodiment of the present invention, the present invention may be made by changing the length of the unidirectional shape memory polymer at least a part of the material forming the soft segment from the crystalline phase to the amorphous phase or from the amorphous phase to the crystalline phase.

According to another embodiment of the present invention, the present invention may comprise a soft segment of poly (e-caprolactone) and a hard segment of 4,4-diphenylmethylene diisocyanate.

According to another embodiment of the present invention, the present invention has a number average molecular weight of 3,000 poly (e-caprolactone) To 5,000.

According to another embodiment of the present invention, the present invention may be an elastic body of the tension supply.

According to another embodiment of the present invention, the present invention may be a rubber.

According to another embodiment of the present invention, the elastic body may be a spring.

According to another embodiment of the present invention, the tension supply body may be a gravity weight.

According to another embodiment of the present invention, the length change according to the temperature of the unidirectional shape memory polymer may be made in the range of the melting point ± 20 ℃ of the soft segment.

According to another embodiment of the present invention, the present invention may be a one-way shape memory polymer is an electrical conductor.

According to another embodiment of the present invention, the present invention may include the unidirectional shape memory polymer may be electrically conductive particles.

In order to solve the second problem, the present invention provides an actuator or artificial muscle including the temperature-sensitive sensor.

In order to solve the third problem, the present invention comprises the steps of heating a polymer comprising a soft segment and a hard segment to a temperature 15 to 30 ℃ higher than the melting point of the soft segment, and extending the heated polymer to a predetermined length, Cooling the stretched polymer to a temperature of 15 to 30 ℃ lower than the melting point of the soft segment, and a method of manufacturing a bidirectional temperature-sensitive sensor comprising the step of coupling a tension supply for supplying a constant amount of tension to the cooled polymer to provide.

According to one embodiment of the present invention, the present invention may comprise a soft segment of poly (e-caprolactone) and a hard segment of 4,4-diphenylmethylene diisocyanate.

According to another embodiment of the present invention, the present invention has a number average molecular weight of 3,000 poly (e-caprolactone) To 5,000.

The bidirectional temperature sensitive sensor according to the present invention is coupled to the unidirectional shape memory polymer and the tension supply, showing a bidirectional shape memory behavior that the length of the unidirectional shape memory polymer can be reversibly changed with temperature change. In addition, the bidirectional temperature sensitive sensor of the present invention has an advantageous effect that can be applied to various fields such as actuators or biomedical fields because it uses a free-form polymer material.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings based on embodiments. The examples presented are exemplary and are not intended to limit the scope of the invention.

The unidirectional shape memory polymer used in the present invention may be changed irreversibly, that is, unidirectional in accordance with temperature change. The unidirectional shape memory of the shape memory polymer is made by the following principle.

Figure 2 shows the shape memory behavior of the unidirectional shape memory polymer. Referring to FIG. 2, the (a) state of the polymer includes a crystalline hard segment 201, a crystalline soft segment 202, and an amorphous soft segment 203. When the polymer in the (A) state is heated to a specific temperature T _{high that} is higher than or equal to the melting temperature of the soft segment, the crystalline soft segment 202 becomes amorphous and changes to the (B) polymer. Subsequently, when tension is applied to the polymer in the (b) state, the amorphous soft segments 203 are changed into the polymer in the (c) state arranged in the tension direction. Subsequently, when the polymer in the (C) state is cooled to a specific temperature T _{low which} is equal to or lower than the melting temperature of the soft segment, some of the amorphous soft segment 203 is crystallized to change into the polymer in the (D) state. At this time, the crystalline soft segment contained in the polymer in the (d) state is a crystalline soft segment formed long in the tension direction different from the crystalline soft segment in the (a) state. The polymer in (D) state relieves the stress itself after a certain period of time, and becomes shorter in length. When the polymer in the (e) state is heated to T _high again, the crystallized part of the crystalline soft segment 202 is amorphous and has elasticity, so that the polymer in the (bar) state has the same shape as that of the (b) state of the original shape. Is changed. In this way, the unidirectional shape memory polymer can remember the original shape by the hard segment acting as a net-point and the soft segment which changes to the amorphous phase in the crystal phase with increasing temperature.

The soft segment included in the unidirectional shape memory polymer of the present invention may be made of poly (e-caprolactone), the hard segment may be made of 4,4-diphenylmethylene diisocyanate, and may be a chain extender. 1,4-butanediol can be used. The molecular weight of poly (e-caprolactone) is important for the polymer of the composition to effectively form hard and soft segments. In the present invention, the number average molecular weight of poly (e-caprolactone) is 3,000 It is preferably from 5,000 to 5,000, in which case an effective shape memory behavior has been observed.

In the bidirectional temperature sensitive sensor of the present invention, the length of the unidirectional shape memory polymer is reversibly changed in accordance with the temperature change by combining the unidirectional shape memory polymer and the tension supply described above.

3 (a) and (b) are views for explaining the operation of the bidirectional temperature sensitive sensor of the present invention. Referring to FIG. 3, one end of the rod-shaped unidirectional shape memory polymer 301 is fixed to the support wall 304a, and the elastic supply body 302 is coupled to the other end so that the one-way shape memory has a constant tension. The polymer 301 is pulled and the other end of the rubber 302 which is an elastic supply body is fixed to the opposite support wall 304b. As shown in (a) of FIG. 3, the unidirectional shape memory polymer 301 maintains a relatively short length under the condition that the temperature is T _high , and when the temperature is changed to T _low as shown in FIG. The length of the storage polymer 301 is increased, and the relative position of the marking portion 303 which marks the boundary between the unidirectional shape memory polymer 301 and the elastic feed body 302 is changed.

4 is a view for explaining that the phase of the unidirectional shape memory polymer is changed in accordance with the temperature change in the bidirectional temperature sensitive sensor of the present invention. Referring to Figure 4, T _high conditions, and hard segments 401 and the amorphous one-way shape memory polymer ((D in Fig. 2) state) comprising a soft segment (403) is under a constant tension, T _low crude In the gun, the unidirectional shape memory polymer including the hard segment 401, the crystalline soft segment 402, and the amorphous soft segment 403 is under constant tension. T _high condition, one-way shape memory polymer is under tension of a predetermined size, but because the amorphous soft segment 403 corresponds to the tensile force have a certain elasticity and to maintain a short length, the T _low condition one-way shape memory polymer is selected from The crystalline soft segments 402 are cooled and arranged in the tension direction by a constant tension, and the elasticity corresponding to the external tension is lost.

The bidirectional temperature sensitive sensor of the present invention can be manufactured through the following steps. First, the polymer including the soft segment and the hard segment is heated to a temperature higher than the melting point of the soft segment. The heated polymer is then stretched to a certain length and the stretched polymer is cooled to a temperature below the melting point of the soft segment. Subsequently, a tension supply is applied to the cooled polymer to supply a constant amount of tension. At this time, the temperature higher than the melting point of the soft segment is preferably selected to a temperature 15 to 30 ℃ higher than the melting point, the temperature lower than the melting point of the soft segment is preferably selected to a temperature 15 to 30 ℃ lower than the melting point. This is because the phase change of the polymer occurs in a constant temperature range, and the temperature range is a temperature range sufficient for the phase change to occur.

The temperature at which the bidirectional temperature sensitive sensor of the present invention can operate is determined. This is because the unidirectional shape memory function of the unidirectional shape memory polymer is caused by the phase change, and the phase change occurs based on the melting point of the soft segment. It is preferable that this temperature is +20 degreeC of melting | fusing point of a soft segment. That is, T _high is preferably a specific temperature higher than the melting point of the soft segment and lower than the melting point of the soft segment + 20 ° C., and T _low is a specific temperature lower than the melting point of the soft segment and higher than the melting point of the soft segment-20 ° C. Is preferably. If out of the temperature range, the shape memory capacity of the one-way shape memory polymer is limited.

In the present invention, the tension supply for supplying a constant size tension to the unidirectional shape memory polymer may be formed in various ways. The tension supply may be an elastic body. Since the elastic body is deformed by an external force and has an elastic force that is a force to recover to its original shape by elasticity, the elastic body may provide a unidirectional shape memory polymer with a predetermined size. At this time, the elastic body should be coupled to the one-way shape memory polymer in a state having a constant elastic force after being deformed by an external force. In order for the length of the unidirectional shape memory polymer used in the present invention to change linearly in proportion to the temperature change, it is preferable that the tension supplied by the tension supply in the temperature range in which the bidirectional temperature sensitive sensor operates is constant. Therefore, the elastic feed body is advantageously elastically deformed in a range capable of supplying a substantially constant tension. The elastic body may be a rubber or metal spring made of a polymer material. In addition, the tension supply may be a gravity weight capable of supplying a constant tension by gravity. Gravity weights have a certain magnitude of gravity on the ground and are suitable for use as tension feeders.

Figure 5 shows an example of the bidirectional temperature sensitive sensor of the present invention. Referring to FIG. 5, the bidirectional temperature sensitive sensor 500 of the present invention includes a unidirectional shape memory polymer 501, an elastic rubber 502, a marker 503, a support wall 504, and a temperature ruler 505. It includes. At this time, the one-way shape memory polymer 501 has a predetermined length and one end is fixed to the support wall 504, the other end of the one-way shape memory polymer 501, the marker portion 503 is coupled The elastic portion 502 is coupled to the mark portion 503 so that one end thereof is fixed to the support wall 504. In addition, the support wall 504 is provided with a temperature ruler 505 in parallel along the extending direction of the one-way shape memory polymer 501, the relative position change with respect to the temperature ruler 505 of the marker portion 503 The temperature scale can be read. The bidirectional temperature sensitive sensor 500 may change the length of the unidirectional shape memory polymer 501 according to the change of the ambient temperature, and sense the temperature by a change in relative position of the marker 503 relative to the temperature ruler 505. Can be.

6A to 6D are views for explaining a process of deriving an optimized tension condition in which the bidirectional temperature sensitive sensor of the present invention operates. 6A and 6B show stress and temperature profiles under various conditions, respectively. 6C illustrates bidirectional shape memory behavior under the conditions of FIGS. 6A and 6B. Referring to Figure 6c, the strain of the unidirectional shape memory polymer (strain) varies in accordance with a given stress, when the stress is 0.63Mpa bidirectional shape memory behavior tends to be inconsistent with the repetition of the cycle, As stress decreases to 0.445Mpa, 0.29Mpa and Mpa0.14, the ideal bidirectional shape memory behavior is shown. However, the smaller the stress, the smaller the change in strain, which is disadvantageous in terms of the application of the temperature sensor. 6D shows an optimized strain profile through repeated experiments. Referring to FIG. 6D, the most ideal bidirectional shape memory behavior without creep at 0.338 Mpa is observed and shows a high strain change. As described above, the temperature-sensitive sensor of the present invention can find a condition showing an optimum deformation behavior according to various sizes and shapes through an accurate design process.

The bidirectional temperature sensitive sensor of the present invention can be operated by an electrical stimulus. To this end, the unidirectional shape memory polymer should be an electrical conductor having a certain size of electrical resistance. When current flows through the conductive unidirectional shape memory polymer, heat is generated by the electrical resistance. This heat is proportional to the magnitude of the current, which can be applied to the bidirectional temperature sensitive sensor of the present invention as a sensor sensitive to current. As described above, the bidirectional temperature sensitive sensor which is sensitive to electric current may be used in various fields such as an actuator or artificial muscle.

There are various methods of imparting conductivity to the unidirectional shape memory polymer. The conductive particles may be added to the polymer material including the hard segment and the soft segment to impart conductivity, or the impurities may be doped to mix and impart conductivity by mixing a conductive polymer having conductivity. In the method using the conductive particles, carbon nanotubes or graphite particles may be used as the conductive particles.

Although the present invention has been described in detail using the embodiments, those skilled in the art will be able to make various modifications and modifications to the embodiments without departing from the spirit of the invention. The invention is not limited by these variations and modifications.

1 (a) and (b) are diagrams for explaining the concepts of unidirectional shape memory and bidirectional shape memory, respectively.

Figure 2 shows the shape memory behavior of the unidirectional shape memory polymer.

3 (a) and (b) are views for explaining the operation of the bidirectional temperature sensitive sensor of the present invention.

4 is a view for explaining that the phase of the unidirectional shape memory polymer is changed in accordance with the temperature change in the bidirectional temperature sensitive sensor of the present invention.

Figure 5 shows an example of the bidirectional temperature sensitive sensor of the present invention.

6A to 6D are views for explaining a process of deriving an optimized tension condition in which the bidirectional temperature sensitive sensor of the present invention operates.

Claims (17)

Unidirectional shape memory polymer; And And a tension supplier coupled to the unidirectional shape memory polymer such that tension is supplied in the longitudinal direction of the unidirectional shape memory polymer. Bidirectional temperature-sensitive sensor, characterized in that the unidirectional shape memory polymer coupled to the tension supply shrinks and expands in the longitudinal direction in response to temperature change. The method of claim 1, The unidirectional shape memory polymer, characterized in that it comprises a soft segment and a hard segment. 3. The method of claim 2, The change in length according to the temperature of the unidirectional shape memory polymer, And at least a portion of the material forming the soft segment is changed from a crystalline phase to an amorphous phase or from an amorphous phase to a crystalline phase. 3. The method of claim 2, Wherein said soft segment is comprised of poly (e-caprolactone) and said hard segment is comprised of 4,4-diphenylmethylene diisocyanate. The method of claim 4, wherein The bi-directional temperature sensitive sensor, characterized in that the number average molecular weight of the poly (e-caprolactone) is 3,000 to 5,000. The method of claim 1, The tension supply body is a bidirectional temperature sensitive sensor, characterized in that the elastic body. The method of claim 6, The elastic body is a bidirectional temperature sensitive sensor, characterized in that the rubber. The method of claim 6, The bidirectional temperature sensitive sensor, characterized in that the elastic body is a spring. The method of claim 1, The tension supply body is a bidirectional temperature sensitive sensor, characterized in that the gravity weight. The method of claim 1, The length change according to the temperature of the unidirectional shape memory polymer, the bidirectional temperature-sensitive sensor, characterized in that made in the range of ± 20 ℃ melting point of the soft segment. The method of claim 1, The one-way shape memory polymer is bidirectional temperature sensitive sensor, characterized in that the electrical conductor. The method of claim 11, Bidirectional temperature sensitive sensor, characterized in that the unidirectional shape memory polymer that is the electrical conductor comprises an electrically conductive particle. An actuator comprising the bidirectional temperature sensitive sensor of claim 1. 13. Artificial muscles comprising the bidirectional temperature sensitive sensor of any one of claims 1 to 12. Heating a polymer including a soft segment and a hard segment to a temperature of 15 to 30 ° C. higher than the melting point of the soft segment; Stretching the heated polymer to a predetermined length; Cooling the stretched polymer to a temperature of 15 to 30 ° C. lower than the melting point of the soft segment; And Coupling a tension supply to the cooled polymer to supply tension in the elongated longitudinal direction; The polymer coupled to the tension supply is a method of manufacturing a bidirectional temperature-sensitive sensor, characterized in that the length is changed in both directions by shrinkage expansion in the longitudinal direction according to the temperature change. The method of claim 15, The soft segment is made of poly (e-caprolactone), and the hard segment is made of 4,4-diphenylmethylene diisocyanate. The method of claim 15, The number average molecular weight of the poly (e-caprolactone) is a manufacturing method of the bidirectional temperature sensitive sensor, characterized in that 3,000 to 5,000.

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