KR101535917B1 - Torsional actuator and preparing method thereof - Google Patents

Abstract

The present invention relates to a rotatable actuator, in which a paraffin wax and a polystyrene-poly (ethylene-butylene) -polystyrene copolymer, which are viscoelastic materials having a large loss coefficient, are dispersed in nanofibers having a multilayer structure and a porous structure and a twist structure , And the critical damping or transient damping is induced by controlling the composition ratio, thereby minimizing the dynamic vibration generated during driving and exhibiting stable rotation behavior, so that the twist rotation and the position of the rotor can be precisely controlled and the response time can be shortened.
Therefore, it is possible to apply the micro mirror as a mirror display capable of controlling the rotation angle by installing the micro mirror at the center of the rotation type actuator, and furthermore, when applied to a medical field such as biomimetic artificial muscle, You can lead.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a rotary actuator,

The present invention relates to a rotatable actuator, and more particularly, to a rotatable actuator in which a paraffin wax and a polystyrene-poly (ethylene-butylene) -polystyrene copolymer are dispersed in nanofibers having a multilayered structure and a twisted structure. And a method for producing the same.

Carbon nanotube artificial muscles are able to rotate 1000 times per muscle length compared to conventional torsional actuators (Keefe, AC & Carman, GP Thermo-mechanical characterization of shape memory alloy torque tube actuators. SmartMater. Struct. 9,665-672 (2000). Kim, J. & Kang, B. Performance and improvement of piezoelectric torsional actuators, Smart Mater. Struct.10, 750-757 (2001) .Fang, Y., Pence, TJ & Tan, X. Fiber -directed conjugated-polymer torsional actuator: nonlinear elasticity modeling and experimental validation, IEEE / ASME Trans. Mechatronics 16, 656-664 (2011)). By varying the volume of the guest material trapped in the pores in the fiber through electrochemical, electrical, chemical and optical methods, twisting rotation due to volume change of the carbon nanotube fibers of the twisted structure resulted in contraction similar to that of the living muscle.

Thus, when heat is applied to the actuator including the paraffin wax, the rotor attached to the actuator rotates 40 msec at 2,000 degrees and has an average rotation speed of 11,500 rpm.

This paraffin wax is a well-known thermal deformation actuator material and can exhibit a volume increase of 30% due to the thermal expansion due to the solid-liquid phase transition. However, since the nanofiber containing paraffin wax has a high resistance to rotation, It is difficult to precisely control the position of the rotor. For example, if the angle of the rotor is changed stepwise rapidly, the position control of the rotor becomes unstable due to the low damping vibration of the rotor (Klintberg, L., Karlsson, M., Stenmark, L. Schweitz, (2002). Sant, HJ, Ho, T. & Gale, BK, In situ heater for a phase-change-material-based large-stroke, high-force paraffin phase transition actuator. Unger, G., Stenjy, J., Keller, A., Bidd, I. & Whiting, MC The crystallization of ultralong normal paraffins: The onset of actuation system. J.Micromech. Microeng., 20,085039-085046 of chain folding. Science 229, 386-389 (1985))

In order to solve the above problem, a shape memory actuator using nanofibers which does not have a twist structure and uses a carbon nanotube as a rotation motor is known as the prior art, but the twist rotation is not large and is reversibly operated (Fennimore, AM, Yuzvinsky, TD, Han, W. -Q., Fuhrer, MS, Cumings, J. & Zettl A. Rotational actuators based on carbon nanotubes, Nature 424, 408-410 (2003) Miaudet, P., Derr A., Maugey, M., Zakri, C., Piccione, PM, Inoubli, R. & Poulin, P. Shape and temperature memory of nanocomposites with broadened glass transition. Science 318, 12994-1296 (2007))

Therefore, the present invention relates to a method for producing a polypropylene wax having a high response speed and excellent dynamic control capability by controlling the composition ratio of paraffin wax and polystyrene-poly (ethylene-butylene) -polystyrene copolymer to induce critical attenuation or transient attenuation To provide a typical actuator.

It is another object of the present invention to provide a micro mirror array having excellent durability and position control capability by using the actuator.

In order to solve the above problems, the present invention provides a nanofiber comprising a nanofiber formed by twisting a carbon nanotube sheet in twisted twisted structure, wherein the nanofiber has an upper portion having a chirality Z-shaped structure and a chiral S Shaped structure, and paraffin wax and a polystyrene-poly (ethylene-butylene) -polystyrene copolymer are dispersed in the nanofiber pores at the lower end.

The weight ratio of the paraffin wax to the polystyrene-poly (ethylene-butylene) -polystyrene copolymer is 6-9: 4-1.

The average diameter of the nanofibers is 15 to 25 占 퐉, and the twist angle of the nanofibers is 20 to 30 °.

The rotary actuator is characterized in that it performs critical damping or overdamping behavior when a voltage is applied, and the rotary actuator has a maximum rotation angle of 70 to 100 ° / mm.

The rotation type actuator performs a overdense action when a voltage of 0.5 to 0.8 V / mm is applied, and a response time of the overdrive action is 0.05 to 0.1 second.

The present invention also provides a method of manufacturing a rotatable actuator including the following steps.

(I) extracting a carbon nanotube sheet from a carbon nanotube forest,

(Ii) twist-spinning the carbon nanotube sheet with a twin archemetene structure to produce a nanofiber having a chiral S-shaped structure,

(Iii) immersing the lower end of the nanofiber in the center of the nanofiber in a mixed solution containing a paraffin wax and a polystyrene-poly (ethylene-butylene) -polystyrene copolymer, followed by drying,

(Iv) providing a rotor at the center of the nanofibers and twisting the chirality S-shaped structure at the upper end to Z-shape.

Also, the present invention provides a micro mirror array in which micro-mirror pixels are provided at the center of the rotatable actuator.

According to the rotary actuator of the present invention, a paraffin wax and a polystyrene-poly (ethylene-butylene) -polystyrene copolymer, which are viscoelastic materials having a large loss coefficient, are dispersed in nanofibers having a multilayer structure and a porous structure and a twist structure, By controlling the composition ratio to induce critical attenuation or transient attenuation, the dynamic vibration generated during driving is minimized to exhibit stable rotational behavior, so that the twist rotation and the position of the rotor can be precisely controlled and the response time can be shortened.

Therefore, it is possible to apply the micro mirror as a mirror display capable of controlling the rotation angle by installing the micro mirror at the center of the rotation type actuator, and furthermore, when applied to a medical field such as biomimetic artificial muscle, You can lead.

1A is an FE-SEM photograph showing a process of manufacturing a rotatable actuator having a twisted structure from a carbon nanotube sheet according to the present invention.
FIG. 1B is a view showing the structure of a rotatable actuator manufactured according to Embodiment 1, and an FE-SEM photograph showing the chirality of nanofibers at the upper and lower ends of a rotatable actuator manufactured according to Embodiment 1. FIG.
FIG. 2A is a graph showing the degree of rotation according to the ON / OFF voltage to check the influence of the voltage applied to the rotary actuator manufactured according to the first embodiment on the rotation drive.
FIG. 2B is a graph showing the maximum rotation angle when the content of paraffin wax is changed in order to confirm the effect of the paraffin wax content of the rotary actuator manufactured according to Example 1 on rotational driving.
2C is a graph showing an average rotational speed according to the number of cycles of the rotatable actuator manufactured according to the first embodiment.
3A is a graph showing the relationship between the composition ratio of the paraffin wax and the polystyrene-poly (ethylene-butylene) -polystyrene copolymer in the rotational actuator manufactured according to Example 1, Off state according to the ON / OFF state of the ON / OFF state.
FIG. 3B is a graph showing a loss factor according to temperature of the polystyrene-poly (ethylene-butylene) -polystyrene copolymer composition ratio of the rotatable actuator manufactured according to Example 1. FIG.
FIG. 3C is a graph showing a damping ratio and a max loss factor according to the content of paraffin wax in a rotatable actuator manufactured according to Example 1. FIG.
FIG. 4A is a diagram showing the structure and operation principle of a micro mirror array manufactured according to Embodiment 2. FIG.
4B is a graph showing the rotation angle of the rotary actuator measured by varying the voltage applied to the micro mirror array manufactured according to the second embodiment.
4C is a graph showing the rotation angle of a mirror pixel measured by different voltages applied to the micro mirror array manufactured according to the second embodiment.
FIG. 4D is a view showing an operation example of a torsional micro mirror array manufactured according to Embodiment 2. FIG.

Hereinafter, the rotary actuator according to the present invention will be described in more detail.

In general, vibration damping, which is one of the important characteristics in motor mount sensors, hard drives, robots, noise and vibration suppression, can be classified according to vibration, and the damping ratio determined by the ratio of the maximum amplitude, ζ).

When the damping ratio (ζ) is 1, the critically damped state rapidly reaches the equilibrium position without overshoot or vibration when the magnetic pole changes stepwise. Overdamped is the case where the damping ratio (ζ) is 1 or more, but the response is slower than the critical attenuation, but no vibration occurs. In addition, under damping is a case where the damping ratio z is less than or equal to 1, and overshoot occurs and the amplitude gradually decreases to reach a stable equilibrium state.

Carbon nanotube fibers dispersed only with paraffin wax or polystyrene-poly (ethylene-butylene) -polystyrene copolymer exhibited typical low damping behavior and showed considerably longer response time when voltage with step change was applied. When the same voltage was applied to the carbon nanotube fibers, a low damping behavior was also exhibited, and the position of the rotor was not stabilized for more than one second due to dynamic vibration. Therefore, critical attenuation or overdamping behavior is required for rapid position control and non-vibration torsional rotation behavior.

The damping ratio (ζ) must be 1 or more for the damping behavior and the damping ratio (ζ) is closely related to the storage modulus and the loss factor. At this time, the maintenance durability of the storage modulus, the loss factor, and the change in temperature are largely influenced by the respective composition components and the composition ratios, so that nanofibers having excellent damping properties The selection of the composition and the composition of the guest material to be dispersed in the rotatable actuator should be given priority.

Accordingly, the present invention provides a nanofiber comprising a nanofiber formed by twisting a carbon nanotube sheet in a twin-arc Archimedean structure, wherein the nanofiber has an upper portion having a chiral Z-shaped structure and a lower portion having a chiral S- And a paraffin wax and a polystyrene-poly (ethylene-butylene) -polystyrene copolymer are dispersed in the nanofiber pores of the lower end portion.

More specifically, according to FIGS. 1A and 1B, a twin Archimedes type twisted structure is produced in a process of pulling out a sheet from a multi-layered carbon nanotube forest, and this double Archimedes type twisted structure is shown at the upper right of FIG. 1A.

Since both ends of the rotary actuator are fixed, rotation of both ends (green portion) is impossible, but the rotor installed at the center portion is rotated. Here, the arrow indicates the rotational direction of the rotor when a voltage is applied to the rotatable actuator. In addition, in the rotary actuator, the upper part of the nanofiber in which the paraffin wax and the polystyrene-poly (ethylene-butylene) -polystyrene copolymer are dispersed has a chiral Z-shaped structure and a lower end has a chiral S-shaped structure. Here, the nanofibers may have an average diameter of 15 to 25 mu m and an average twist angle of 20 to 30 DEG.

According to one embodiment of the present invention, the rotational actuator of the present invention may have a weight ratio of paraffin wax to polystyrene-poly (ethylene-butylene) -polystyrene copolymer of 6-9: 4-1. Since the damping ratio (ζ) is high between 1 and 2, it exhibits a high damping behavior. In particular, the performance degradation due to the number of cycles is negligible, so that the torsional rotational behavior can be stabilized in the long term.

The weight ratio of the paraffin wax to the polystyrene-poly (ethylene-butylene) -polystyrene copolymer may be 6-9: 4-1. When the composition of the paraffin wax is less than 6, the paraffin wax is trapped in the ethylene-butylene crystal and the change in volume upon heating is inhibited, so that the behavior as an actuator may not be exhibited. When the paraffin wax is more than 9, A phase separation phenomenon may occur between poly (ethylene-butylene) -polystyrene copolymers. Therefore, it is most preferable that the paraffin wax and the polystyrene-poly (ethylene-butylene) -polystyrene copolymer are contained within the above-mentioned composition range in order to stably perform the twisting rotational behavior of the actuator.

Also, in the rotary actuator, a damping ratio is 1 to 2 at an applied voltage of 0.5 to 0.8 V / mm, and a damping behavior without dynamic vibration is exhibited. Under these conditions, the response time of the rotary actuator is 0.05 to 0.1 second The response speed is about 10 times faster.

A rotor is installed at the center of the nanofibers, which can be fixed with a constant tensile load by using mylar paddles. At this time, the tensile load is preferably 0.2 to 0.4 MPa.

In another aspect of the present invention, there is provided a method of manufacturing a carbon nanotube sheet, comprising the steps of: (i) extracting a carbon nanotube sheet from a carbon nanotube forest; (ii) twisting the carbon nanotube sheet with a twin-archimedean structure to produce a chiral S- (Iii) immersing the lower end of the nanofiber on the basis of the center of the nanofiber in a mixed solution containing paraffin wax and a polystyrene-poly (ethylene-butylene) -polystyrene copolymer, and drying ) Providing a rotor at the center of the nanofibers and twisting the chirality S-shaped structure of the upper end to Z-shape.

To describe the manufacturing method of the rotatable actuator in more detail, FIG. 1A is a SEM photograph showing a process of manufacturing nanofibers from a carbon nanotube aerosol sheet. According to the present invention, the manufacturing process of the rotatable actuator according to the present invention is such that a carbon nanotube aerogel sheet is extracted from a CNT forest by a drawing method, Nanofibers having a chiral S-type structure can be prepared by twist spinning at 200 to 300 turns / cm so as to have an archimedean structure.

Next, the ends of the nanofibers are fixed while tension is applied to the manufactured nanofibers, and then a rotor having the same length of the upper and lower ends of the nanofibers is provided. And the torsional rotation and the overdamping behavior of the rotatable type actuator of the present invention.

Then, the lower end of the fixed nanofibers can be immersed in a mixed solution containing paraffin wax and a polystyrene-poly (ethylene-butylene) -polystyrene copolymer at 50 to 70 ° C for 20 to 30 hours. The immersed nanofibers completely evaporate the solvent at room temperature. After the solvent is completely evaporated at room temperature, the chirality S-type structure of the upper part of the nanofiber having the chiral S-type structure is twisted into Z-shape so as to have a heterochyrric structure You can give.

The upper end of the nanofiber serves as a return spring for restoring the structure of the upper end of the nanofibers when the voltage applied to the rotatable actuator is cut off.

The driving principle of the rotary actuator according to the present invention will be described. First, the rotary actuator is divided into an upper end portion and a lower end portion starting from the central portion, and a lower end portion is driven by volume change by paraffin wax and a polystyrene-poly (ethylene-butylene) -polystyrene copolymer. do. In the conventional rotary actuator, only one end is fixed, which has a large rotation angle because there is no return spring, but reversible drive is not performed.

More specifically, when the electrothermal driving force is applied to the nanofibers in which the paraffin wax and the polystyrene-poly (ethylene-butylene) -polystyrene copolymer as the guest materials are dispersed, the volume of the actuator expands and the nanofibers are stretched and the actuator having the twist torque It has a loosening torque to complement the role of the fiber and serves to return the paddle to its original rotational angle position when the polymer is not in the opposite direction. Therefore, the upper end of the nanofiber serves as a return spring for preventing the twist of the rotatable actuator from falling.

In addition, the rotatable actuator can be applied to a display device using micro mirror pixels by providing micro mirror pixels at the center of the nanofibers and fixing the rotatable actuator to two connecting portions diagonally. Referring to FIG. 4A, the rotary actuator having the micro mirror pillars may be driven by applying a voltage to the two connection portions. At this time, the size of the micro mirror pixels provided in the rotary actuator may be 3 mm x 3 mm.

The voltage applied to the rotatable actuator provided with the micro mirror pixels is preferably 0.25 to 0.4 V / mm, and the micro mirror pixels provided in the rotatable actuator are rotated according to the applied voltage on and off, The binary image of the micro mirror pixel can be determined. When the voltage is on or off, the micro mirror pixels provided in the rotatable actuator have a specific position. More specifically, when the applied voltage is off, the rotation angle of the micro mirror becomes 'dark image' at 0 °, When the voltage is on, the angle of rotation of the micro mirror is 90 °, which is a 'bright image'. Figure 4d shows an example of the operation of a multiple micro-mirror display using a torsional micro-mirror array operated on the same principle as above.

Hereinafter, the present invention will be described in more detail with reference to specific examples.

Example  1. Rotating type Actuator  Produce.

A 1-3 nm catalyst layer was coated on a silicon wafer by electron beam evaporation and placed in a quartz tube preheated to 700 ° C in a gas atmosphere containing 750 sccm of argon and 100 sccm of hydrogen, And 50 sccm of acetylene was injected to produce a multiwalled carbon nanotube forest consisting of nine layers with a length of 400 μm or less and an outer diameter of 12 nm or less.

A multi-walled carbon nanotube sheet having a length of 11 cm was pulled out from one side wall of the multi-walled carbon nanotube forest. The nanotube was twisted by 228 rotations per cm to produce nanofibers having a length of 7 cm. At this time, the multi-walled carbon nanotube forest was fixed at 1 cm to have a fiber diameter of 20 μm.

Finally, both ends of the prepared nanofibers were fixed, and then paraffin wax and polystyrene-poly (ethylene-butylene) -polystyrene copolymer were dissolved in toluene in different ratios. Poly (ethylene-butylene) -polystyrene copolymer solution in a paraffin wax and a polystyrene-poly (ethylene-butylene) -polystyrene copolymer solution at 60 캜 for 24 hours from the center of the fixed nanofiber, Polystyrene copolymer, and then evaporated at room temperature, stretched using a motor attached to the upper end of the nanofibers having chirality of S type, and twisted again so that chirality becomes Z-shaped. As a result, a rotatable actuator having a hetero-chiral structure was fabricated. In order to confirm the structure of the rotatable actuator manufactured above, it was measured by FE-SEM and is shown in Fig.

Polystyrene-poly (ethylene-butylene) -polystyrene copolymer and paraffin wax were purchased from Sigma-Aldrich, and the paraffin wax and polystyrene-poly (ethylene-butylene) -polystyrene copolymer were styrene / The ethylene / butylene ratio was 29:71, the paraffin wax was crystalline in the solid state, the thermal expansion coefficient was several hundred ppm / K, and the volume expansion during melting was 10-20%.

Experimental Example Column 1  Mechanical Analysis TMA )

Both ends of the rotary actuator of about 4 cm manufactured according to Example 1 were fixed to a thermomechanical analyzer (TMA, Seiko TMA / SS7100). The upper end of the rotatable actuator was connected to the platinum wire using a silver paste, and the lower end was attached to the bottom of the silver paste, followed by sufficiently drying and connecting to a voltage meter (Keithley 2635).

A load of 0.35 MPa was applied to the rotary actuator and a 0.5 Hz square wave voltage of 50% duty cycle was applied. The behavior and rotation angle of the actuator were confirmed by thermomechanical analysis while varying the voltage and analyzed using a high - resolution high - speed camera. The results are shown in Fig.

FIG. 2 is a graph showing the behavior of the rotary actuator manufactured according to the first embodiment. FIG. 2 (a) is a graph showing the behavior of the rotary actuator manufactured according to the first embodiment, FIG. 2B is a graph showing the rotation angle depending on the voltage. FIG. 2B is a graph showing the maximum rotation angle when the content of paraffin wax is changed in order to examine the effect of the paraffin wax content of the rotary actuator manufactured in Example 1 on the rotation drive And FIG. 2C is a graph showing an average rotational speed according to the number of cycles of the rotatable actuator manufactured according to the first embodiment.

2A, measurement was conducted using a rotary actuator in which a paraffin wax having a weight ratio of 8: 2 prepared in Example 1 and a polystyrene-poly (ethylene-butylene) -polystyrene copolymer were dispersed. As a result, The nanofiber portion in which the paraffin wax and the polystyrene-poly (ethylene-butylene) -polystyrene copolymer are dispersed rotates in the negative direction, which means that it is loosened. At the time of cooling, it can be confirmed that the nanofiber portion in which the paraffin wax and the polystyrene-poly (ethylene-butylene) -polystyrene copolymer are dispersed is rotated in the opposite direction. In other words, the maximum rotational force at about 0.75 V / mm was 80 ° / mm and reversibly behaved. This means that it is about 25 times faster than the conventional nanofiber.

2B, a rotary actuator having a paraffin wax having a weight ratio of 8: 2 and a polystyrene-poly (ethylene-butylene) -polystyrene copolymer dispersed therein was used, and a paraffin wax and a polystyrene-poly (ethylene- ) -Polystyrene copolymer dispersed therein, it was confirmed that the actuator can be controlled by varying the content of paraffin wax. Interestingly, it was found that the maximum rotation rapidly increased when the paraffin content was 55 wt% Respectively. When the paraffin content was more than 60%, the maximum rotation was constant at 80 ° / mm. That is, when the content of paraffin wax is 50% or more, the maximum rotation sharply decreases to 10-15 ° / mm. This is because when the content of paraffin wax is increased, the volume change occurs due to the solid-liquid phase transition of the paraffin wax upon heating. In the case of the paraffin wax contained in the polystyrene-poly (ethylene-butylene) -polystyrene copolymer, The rotation behavior of the nanofibers in which the paraffin wax and the polystyrene-poly (ethylene-butylene) -polystyrene copolymer are dispersed has only a polystyrene-poly (ethylene-butylene) -polystyrene copolymer Which is not significantly different from that of nanofibers. However, when the content of paraffin wax is 50% or more, paraffin wax encapsulated in a polystyrene-poly (ethylene-butylene) -polystyrene copolymer in a polystyrene-poly (ethylene-butylene) -polystyrene copolymer is liberated, The rotational behavior of the rotor is greatly increased. The higher the content of paraffin wax, the more freely it is possible to expand upon heating. As a result, the rotation angle is affected not only by the volume expansion of the paraffin wax but also by the storage modulus (E ').

In addition, according to the graph inserted in FIG. 2B, it can be seen that the rotational angle can be adjusted according to the voltage through the rotational behavior according to the voltage change of the rotational actuator manufactured according to the first embodiment.

Referring to FIG. 2C, a 0.5 Hz square wave voltage was applied at 0.625 V / mm to the rotatable actuator manufactured according to Example 1, wherein the graph on the left side of the graph was 4 cm in length and 3.2 / / cm in weight The rotation angle and the rotation speed change in one cycle are shown by using square-wave voltage of 0.5 Hz, 0.625 V / mm, and 50% duty cycle in the rotary actuator. Each point described on the graph represents an average speed of 39,000 cycles with an average rotational speed of 9,800 rpm. When the paraffin content was 80%, it showed fast and reversible actuator behavior up to 40,000 cycles. At this time, the rotation speed was not decreased but stable, and the maximum rotation speed was about 9,800 rpm.

Experimental Example  2.

A dynamic analysis (DMA) of fibers 5 mm in length was performed using a perkin elmer device. The rotatable actuator having the heterochyrrhetic twist structure manufactured according to Example 1 was cooled to -70 캜 and heated to 70 캜 to 90 캜 at a rate of 5 캜 / min, where the measured values were stored The loss factor (tan δ = E '' / E ') was calculated from the storage modulus (E') and the loss modulus (E "). At this time, the nanofibers prepared in Example 1 were mounted vertically on a dynamic analyzer and 1 Hz vibration was continuously applied under a dry nitrogen gas at 50 mL / min. The measurement results are shown in FIG.

3A is a graph showing the effect of the weight ratio of the paraffin wax and the polystyrene-poly (ethylene-butylene) -polystyrene copolymer of the rotatable actuator produced according to Example 1 on the torsional rotational behavior, A graph showing the rotation angle according to the ON / OFF state of the voltage, wherein the applied voltage was 0.625 V / mm. Referring to this, the red line indicated on the graph shows a hyperdense behavior when the weight ratio of paraffin wax to polystyrene-poly (ethylene-butylene) -polystyrene copolymer is 8: 2, and a low damping behavior when the blue line is 2: 8 . The graph inserted in the graph represents the non-vibration torsional response for one cycle. In addition, it can be confirmed that the response time is 0.09 seconds, which is considerably faster than that of the conventional rotary actuator.

3B is a graph showing a loss factor (tan δ = E '' / E ') according to the temperature of polystyrene-poly (ethylene-butylene) -polystyrene copolymer composition ratio of the rotational actuator manufactured according to Example 1 At a temperature range of -70 to 90 占 폚. Actuators using nanofibers dispersed only in polystyrene-poly (ethylene-butylene) -polystyrene copolymer exhibit only one loss factor (tan δ) peak in the temperature range of -70 to 90 ° C., whereas in Example 1 Rotational actuators including nanofibers exhibit two loss factor (tan δ) peaks. That is, the loss factor (tan δ) at around -40 ° C. which is the phase transition temperature of the ethylene-butylene portion of the polystyrene-poly (ethylene-butylene) -polystyrene copolymer and around the phase transition temperature of 60 ° C. of the paraffin wax, . This means that the loss factor (tan δ) is highly temperature dependent.

FIG. 3c is a graph showing the damping ratio and the max loss factor according to the content of paraffin wax in the rotatable actuator manufactured according to Example 1. When the viscoelasticity is lost, the loss factor and the damping ratio are increased That is, when the content of paraffin wax is 60 to 90 wt%, the damping ratio is 2, indicating that the twist rotation behavior of the rotary actuator is stable and has a fast response time to the overdamped region. This means that there is a strong correlation between the loss factor and the damping response of the paraffin wax and the polystyrene-poly (ethylene-butylene) -polystyrene copolymer.

Taking all the above results into consideration, it is possible to obtain a rotary actuator having no dynamic vibration, fast response speed and stable overdamping behavior by optimizing the composition ratio of paraffin wax and polystyrene-poly (ethylene-butylene) -polystyrene copolymer.

Example  2

A micro mirror array was fabricated in which the rotatable actuator manufactured according to Example 1 was fixed diagonally across two connection portions of mirror pixels and the connection portions were electrically connected to rotate the fibers. At this time, the mirror pixels have a size of 3 x 3 mm and are installed at the center of the rotary actuator. From the binary image of the mirror pixel, the on and off voltages corresponding to the sagittal angle were determined. The results are shown in Figs. 4B and 4C.

FIG. 4B is a graph showing the rotation angle of the rotary actuator measured by varying the voltage applied to the micro mirror array manufactured according to Embodiment 2. FIG. 4C is a graph showing the voltage applied to the micro mirror array manufactured according to Embodiment 2 Is a graph showing the rotation angle of the mirror pixel measured in different ways.

Referring to FIG. 4B, when a voltage of about 0.34 V / mm is applied to the micro mirror array manufactured according to the second embodiment, since the nanofibers and the mirror pixels are rotated to have a 90 DEG rotation angle, Image, and the voltage is off so that the mirror pixels are back to 0 ° rotation angle, so that the micro mirror array shows a "dark" image.

According to FIG. 4C, when the on / off period of the applied voltage is fixed to 1 second and the voltage is fixed to 0.34 V / mm, the difference in rotation angle between on / off of the mirror pixels of the micro mirror array manufactured according to Embodiment 2 90 °, which means that the rotation angle of the mirror pixel can be controlled arbitrarily by controlling the applied voltage. Therefore, the feasibility of display using a micro mirror array is high.

Claims (9)

A carbon nanotube sheet includes a nanofiber formed by twisted spinning in a twin arcimeter structure,
The nanofibers are divided into an upper portion having a chiral Z-shaped structure and a lower portion having a chiral S-shaped structure on the basis of the center,
Wherein a paraffin wax and a polystyrene-poly (ethylene-butylene) -polystyrene copolymer are dispersed in the nanofiber pores at the lower end. The method according to claim 1,
Wherein the weight ratio of the paraffin wax to the polystyrene-poly (ethylene-butylene) -polystyrene copolymer is 6-9: 4-1. The method according to claim 1,
Wherein the average diameter of the nanofibers is 15-25 占 퐉. The method according to claim 1,
Wherein the twist angle of the nanofibers is 20 to 30 degrees. The method according to claim 1,
Wherein the rotary actuator performs critical damping or overdamping behavior when a voltage is applied. The method according to claim 1,
Wherein the maximum rotation angle of the rotary actuator is 70 to 100 占 퐉 / mm. The method according to claim 1,
Wherein the rotary actuator performs the overdense action when a voltage of 0.5 to 0.8 V / mm is applied, and the response time of the overdrive action is 0.05 to 0.1 second. (I) extracting a carbon nanotube sheet from a carbon nanotube forest;
(Ii) Twist-spinning the carbon nanotube sheet with a twin archemetene structure to produce a nanofiber having a chiral S-shaped structure;
(Iii) immersing the lower end of the nanofiber on the basis of the center of the nanofiber in a mixed solution containing a paraffin wax and a polystyrene-poly (ethylene-butylene) -polystyrene copolymer, followed by drying; And
(Iv) providing a rotor at the center of the nanofibers and twisting the chirally S-shaped structure at the upper end to Z-shape. A micro mirror array comprising micro-mirror pixels in the center of a rotatable actuator according to claim 1.

Images