JP2018129959A - Liquid crystal droplet actuator using flow in liquid crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal droplet actuator utilizing flow in a liquid crystal capable of moving a liquid crystal by direct current voltage.SOLUTION: Liquid crystal droplets 8A, a moving medium 2 having a pair of opposed wall surfaces 2a, 2b and including a flow path 2h in which the liquid crystal droplets 8 are arranged between the pair of opposed wall surfaces 2a, 2b, a pair of electrode portions 6a, 6b arranged so as to sandwich the liquid crystal droplets 8 in the flow path 2h of the moving medium 2, and a control unit 7 for applying a direct current voltage capable of forming an electric field which causes flow caused by electrohydrodynamic instability in the liquid crystal droplets 8 between the pair of electrode portions 6a, 6b are provided. When a DC voltage is applied between the pair of electrode portions 6a, 6b, the pair of electrode portions 6a, 6b are disposed so that an electric field intersecting the axial direction of the flow path 2h is generated.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a liquid crystal droplet actuator using a flow in liquid crystal.

Since the optical properties of liquid crystals change as liquid crystal molecules are aligned, liquid crystals are used in information display devices such as liquid crystal displays by utilizing these properties.
The viscosity of the liquid crystal changes when the orientation direction of the liquid crystal molecules is changed by applying an electric field or a magnetic field. That is, since the liquid crystal also has a property as an electrorheological fluid, bearings, dampers, and the like using this property have been developed.

Patent Document 1 discloses a configuration in which electrode portions and insulating portions are alternately arranged along the circumferential direction of a tubular tube body, and the electrode portion to which a voltage is applied can be moved along the circumferential direction. For example, it is disclosed that the liquid crystal flows along the moving direction of the electrode portion.
However, the technique of Patent Document 1 is a technique for generating liquid crystal flow by pulling liquid crystal molecules to an electrode portion. That is, the technique of Patent Document 1 is merely a technique for moving the liquid crystal by a phenomenon similar to the phenomenon in which metal is attracted to the magnet, and does not cause the liquid crystal to flow.

  On the other hand, by applying an electric field or a magnetic field to liquid crystal molecules, a liquid crystal flow is actually generated, and techniques using this liquid crystal flow have been developed (Patent Documents 2 to 6).

  The techniques of Patent Documents 2 to 6 are based on the principle of generating a liquid crystal flow due to a velocity gradient generated around the liquid crystal molecules due to the rotation of the liquid crystal molecules. Can be generated. And in patent documents 2-6, the structure using this liquid crystal flow is also disclosed.

  Patent Document 7 discloses a technique for realizing movement of a liquid crystal drop by applying an electric field or magnetic field to the liquid crystal drop. By using this technique, the liquid crystal drop can be moved in various situations. Has been realized.

JP 2006-42430 A Japanese Patent No. 3586734 Japanese Patent No. 4273341 JP 2009-185993 A JP 2009-185994 A JP 2010-183754 A JP2015-96765A

  In the techniques of Patent Documents 2 to 7, the liquid crystal flow is generated by applying a pulse voltage to the liquid crystal. If the liquid crystal can be moved by applying a DC voltage, the movement of the liquid crystal is used. This is preferable.

  In view of such circumstances, an object of the present invention is to provide a liquid crystal droplet actuator using a flow in a liquid crystal that can move a liquid crystal by a DC voltage.

The liquid crystal droplet actuator using the flow in the liquid crystal of the first invention applies an electric field to the liquid crystal droplet, a moving medium in which the liquid crystal droplet is movably disposed, and the liquid crystal droplet in a state of being disposed on the moving medium. An electric field generating unit having a pair of electrode units and a DC voltage capable of forming an electric field that causes a flow due to electrohydrodynamic instability in the liquid crystal droplets are applied between the pair of electrode units of the electric field generating unit. And a control unit.
According to a second aspect of the present invention, there is provided the liquid crystal droplet actuator using the flow in the liquid crystal according to the first aspect, wherein the moving medium has a pair of opposed wall surfaces and the liquid crystal droplets are disposed between the pair of opposed wall surfaces. The pair of electrode portions sandwich the liquid crystal droplet in the flow path of the moving medium, and when a DC voltage is applied between the pair of electrode portions, the shaft of the flow path It is arranged to generate an electric field that intersects the direction.
According to a third aspect of the present invention, in the liquid crystal droplet actuator using the flow in the liquid crystal, the moving medium has a liquid in which the liquid crystal droplet is immersed.
According to a fourth aspect of the present invention, in the first, second or third aspect of the invention, the control unit has a function of changing the magnitude of the DC voltage applied between the pair of electrode units. It is characterized by having.
According to a fifth aspect of the present invention, there is provided the liquid crystal droplet actuator using the flow in the liquid crystal according to the first, second, third or fourth aspect, wherein the control unit changes the direction of the electric field generated between the pair of electrode units. It is characterized by having.
According to a sixth aspect of the present invention, in the first, second, third, fourth, or fifth invention, the electric field generating unit includes a plurality of electrode units, and the control unit includes: A function of applying a DC voltage between selected electrode portions among the plurality of electrode portions is provided.

According to the first invention, an electric field that causes a flow due to electrohydrodynamic instability is generated in the liquid crystal droplets, so that the liquid crystal droplets can be moved in a direction orthogonal to the direction of the electric field. Therefore, if the movement of the liquid crystal droplet is used as a driving force, the object can be moved.
According to the second invention, when an electric field is applied to the liquid crystal droplets, the liquid crystal droplets can be moved along the flow path.
According to the third invention, the movement of the liquid crystal droplets in the liquid can be adjusted by adjusting the direction of the electric field applied to the liquid crystal droplets.
According to the fourth invention, the moving speed can be changed by changing the applied voltage.
According to the fifth aspect of the present invention, the direction in which the liquid crystal flows can be changed by changing the direction of the electric field.
According to the sixth aspect, since the electric field formed can be adjusted by adjusting the electrode portion to which the voltage is applied, the movement of the liquid crystal droplets can be adjusted.

It is explanatory drawing of the liquid crystal droplet actuator 1 using the flow in a liquid crystal of this embodiment, Comprising: (A) is a top view, (B) is a schematic side view. It is the figure which showed the flow which generate | occur | produces in the liquid-crystal droplet 8 when the voltage EF is applied, Comprising: (A) is an AA line schematic sectional drawing of (B), (B) is a schematic plan view. . It is explanatory drawing of the liquid crystal droplet actuator 1 in which the electrode part 6a has a some electrode. It is explanatory drawing of the liquid crystal droplet actuator 1 of the structure by which the liquid crystal droplet 8 is immersed in the moving medium 2A which has the liquid 2L. It is a schematic explanatory drawing of the actuator used for experiment, (A) is a top view, (B) is a side view. (A) It is a schematic diagram of the liquid crystal droplet which image | photographed the liquid crystal droplet in an actuator, (B) The conceptual diagram at the time of binarizing the image | photographed liquid crystal droplet image is shown. This is a binarized image obtained by photographing the movement of a liquid crystal droplet when an electric field formed by a pulse voltage is applied to the liquid crystal droplet. This is a binarized image obtained by photographing the movement of a liquid crystal droplet when an electric field formed by a DC voltage is applied to the liquid crystal droplet. (A) is a graph showing the relationship between the amount of movement of liquid crystal droplets and time when an electric field formed by a pulse voltage and a DC voltage is applied to the liquid crystal droplets, and (B) is the voltage value of the DC voltage and the liquid crystal. It is a graph showing the relationship with the moving speed of a droplet. It is the image which image | photographed the movement condition of the liquid crystal droplet which mixed the microparticle. It is the image which image | photographed the movement condition of the liquid crystal droplet which mixed the microparticle. It is the figure which showed the movement condition of a microparticle in the liquid crystal droplet which mixed the microparticle. It is the figure which showed the movement condition of a microparticle in the liquid crystal droplet which mixed the microparticle.

Next, an embodiment of the present invention will be described with reference to the drawings.
In FIG. 1 to FIG. 4, the relative dimensions of each part do not match the actual ones in order to make the configuration of each part easier to understand.

(Liquid Crystal Drop Actuator 1 Utilizing Flow in Liquid Crystal of this Embodiment)
First, based on FIG. 1, the liquid crystal droplet actuator 1 using the flow in the liquid crystal of the present embodiment will be described.

(Liquid crystal droplet 8)
In FIG. 1, reference numeral 8 indicates a liquid crystal droplet serving as a moving body of the liquid crystal droplet actuator 1 (hereinafter sometimes simply referred to as the liquid crystal droplet actuator 1) using the flow in the liquid crystal of the present embodiment. As shown in FIG. 1, the liquid crystal droplet 8 is arranged so as to be able to move in a flow path 2 h of a moving medium 2 described later. Specifically, it is arranged so that it can move in the flow path 2h along the axial direction of the flow path 2h (the left-right direction in FIG. 1).

  In addition, the liquid crystal droplet 8 used for the liquid crystal droplet actuator 1 using the flow in the liquid crystal of the present embodiment is not particularly limited. For example, a nematic liquid crystal, a smectic liquid crystal, a cholesteric liquid crystal, a discotic liquid crystal, or the like is not particularly limited as long as the liquid crystal generates a flow due to electrohydrodynamic instability when an electric field is applied.

(Moving medium 2)
As shown in FIG. 1, the moving medium 2 includes a flow path 2 h in which the liquid crystal droplet 8 is disposed. Specifically, the moving medium 2 includes a pair of parallel opposing walls 2a and 2b facing each other, and a flow path 2h is provided between the pair of opposing walls 2a and 2b. For example, as shown in FIG. 1, a pair of spacers 2s, 2s are arranged between a pair of flat plates 2p, 2p, and the moving medium 2 is formed so that a gap is formed between the pair of flat plates 2p, 2p. be able to. In this case, a space surrounded by the pair of opposing walls 2a and 2b and the inner surfaces of the pair of spacers 2s and 2s becomes the flow path 2h.

  The pair of opposing walls 2a and 2b do not necessarily have to be parallel, and the distance may be different at the axial position of the flow path 2h. Further, the pair of opposing walls 2a and 2b are not necessarily flat surfaces, and the surfaces may be uneven.

(Alignment film 4)
As shown in FIG. 1, an alignment film 4 is formed on the surfaces of the pair of opposing walls 2a and 2b. The alignment film 4 aligns liquid crystal molecules in the liquid crystal droplets 8 in a predetermined direction. Specifically, the surface of the alignment film 4 is rubbed so that the liquid crystal molecules in the liquid crystal droplets 8 are aligned parallel to the surface of the moving medium 2 (or parallel to the axial direction of the flow path 2h). It has been broken.

  The reason why the liquid crystal molecules in the liquid crystal droplets 8 are aligned is to generate a predetermined flow in the liquid crystal droplets 8 when an electric field EF is applied to the liquid crystal droplets 8 as will be described later.

(Control unit 7)
As shown in FIG. 1, the pair of electrode parts 6a and 6b is electrically connected to a control part 7 having a power source by wiring. The control unit 7 has a function of applying a DC voltage between the pair of electrode units 6a and 6b.

  For example, the control unit 7 controls the magnitude and timing of the DC voltage applied between the pair of electrode units 6a and 6b to form the electric field EF or form the electric field EF between the pair of electrode units 6a and 6b. The timing for adjusting the intensity of the electric field EF to be formed is adjusted.

  The control unit 7 also has a function of controlling the direction of the electric field EF formed by a DC voltage applied between the pair of electrode units 6a and 6b. Specifically, it has a function of switching between a state in which the electrode portion 6a is at a high voltage with respect to the electrode portion 6b and a state in which the electrode portion 6b is at a high voltage with respect to the electrode portion 6ab. Yes.

(Operation of Liquid Crystal Drop Actuator 1 Utilizing Flow in Liquid Crystal of This Embodiment)
Since it is the above structure, in the liquid crystal droplet actuator 1 using the flow in the liquid crystal of the present embodiment, when a voltage is applied between the pair of electrode portions 6a and 6b (that is, the electrode portion 6a has a higher voltage than the electrode portion 6b). ), An electric field EF is generated between the pair of electrode portions 6a and 6b. For example, in FIGS. 1 and 2, an electric field EF perpendicular to the axial direction of the flow path 2h is generated. Then, since an electric field EF is applied to the liquid crystal droplet 8, a flow as shown in FIG. 2 is generated in the liquid crystal droplet 8 due to electrohydrodynamic instability. Specifically, a rightward flow occurs in the vicinity of the center of the liquid crystal droplet 8 in FIG. 2B, a counterclockwise swirling flow occurs in the upper left portion of the liquid crystal droplet 8, and a clockwise rotation occurs in the lower left portion of the liquid crystal droplet 8. A swirling flow is generated. In addition, a counterclockwise swirling flow is generated in the upper part of the liquid crystal droplet 8, and a clockwise swirling flow is generated in the lower part. On the right side of the liquid crystal droplet 8, a swirl flow with the y-axis as the rotation axis is generated (see FIG. 2A). That is, in the liquid crystal droplet 8, a vertically symmetric and macroscopic rightward flow in FIG. 2B occurs, so that the liquid crystal droplet 8 moves in the flow direction of the central portion, that is, rightward.

  Therefore, if the movement of the liquid crystal droplet 8 is used as a driving force, the object can be moved. For example, if one end of the shaft-shaped member is immersed in the liquid crystal droplet 8, the shaft-shaped member moves together with the liquid crystal droplet 8, so that the movement of the other end of the shaft-shaped member can be used. If an object to be transported is mixed in the liquid crystal droplet 8, the object can be transported to a predetermined position.

  Further, if the voltage value of the applied DC voltage is changed by the control unit 7 in the range of the DC voltage that can form the electric field EF that causes the flow caused by the electrohydrodynamic instability in the liquid crystal droplet 8, Since the flow speed in the liquid crystal droplet 8 changes, the moving speed of the liquid crystal droplet 8 can be changed. That is, if the applied DC voltage is increased, the moving speed of the liquid crystal droplet 8 can be increased, and if the applied DC voltage is decreased, the moving speed of the liquid crystal droplet 8 can be decreased.

  Furthermore, if the direction of the electric field EF is changed by the control unit 7, the moving direction of the liquid crystal droplet 8 can be changed. For example, in FIG. 1, when the electric field EF is generated by applying a voltage so that the electrode portion 6a has a higher voltage than the electrode portion 6b, the liquid crystal droplet 8 moves to the right in FIG. In this case, the liquid crystal droplet 8 can be moved in the left direction in FIG. 1 by applying the electric field EF so that the electrode section 6b has a higher voltage than the electrode section 6a.

  The control unit 7 may have a function of applying a pulse voltage in addition to a function of applying a DC voltage. In this case, the movement state of the liquid crystal droplet 8 can be variously changed by adjusting whether to apply a DC voltage or a pulse voltage.

(Manufacturing method of a pair of electrode parts 6a and 6b and alignment film 4)
As described above, the moving medium 2 has a pair of electrode portions 6a and 6b and an alignment film 4 on the pair of opposing walls 2a and 2b, but a pair of the opposing walls 2a and 2b of the moving medium 2 has a pair. The method for forming the electrode portions 6a and 6b and the alignment film 4 is not particularly limited.
For example, it can be formed by the following method.

  First, a film of ITO or the like is formed on the surface of the pair of opposing walls 2a and 2b of the moving medium 2 by a method such as sputtering or vacuum deposition to form a pair of electrode portions 6a and 6b. Next, the alignment film 4 is formed on the surfaces of the pair of opposing walls 2a and 2b on which the pair of electrode portions 6a and 6b are formed by a spin coating method or the like. Then, the alignment film 4 can be formed on the surfaces of the pair of opposing walls 2a and 2b so as to cover the pair of electrode portions 6a and 6b and the pair of electrode portions 6a and 6b.

  When forming the ITO film, a wiring for connecting the pair of electrode portions 6a, 6b and the control portion 7 may be formed on the surfaces of the pair of opposing walls 2a, 2b. In this case, the wiring shape may be masked on the surfaces of the pair of opposing walls 2a and 2b of the moving medium 2.

  In addition, liquid crystal molecules in the liquid crystal droplet 8 can be aligned in a predetermined direction, and a flow of a predetermined form can be generated in the liquid crystal droplet 8 when an electric field is applied to the liquid crystal droplet 8. The alignment film 4 is not necessarily provided. For example, a known rubbing-less process or a weak anchoring process may be performed on the pair of opposing walls 2a and 2b. The weak anchoring process is an anchoring process described in Japanese Patent No. 4053530 “Zero-plane anchoring liquid crystal alignment method and liquid crystal device thereof”, that is, horizontal or oblique alignment is forced, but in-plane (horizontal For example, anchoring without an alignment forcing force in the direction in the horizontal plane where the axis of the molecule is located.

(When the electrode part 6 has a plurality of electrodes)
In the above example, the case where the pair of electrode portions 6a and 6b are provided on the surfaces of the pair of opposing walls 2a and 2b of the base member 2 so as to sandwich the flow path 2h has been described. In this case, each electrode part 6a, 6b may be formed with one electrode, and each electrode part 6a, 6b may be formed with a plurality of electrodes. For example, FIG. 3 shows an electrode portion 6a having a plurality of electrodes, but the electrode portion 6a is formed by arranging a plurality of electrodes in a grid pattern. In this case, the opposing electrode portion 6b is also formed by arranging the electrodes in a grid like the electrode portion 6a, and the electrodes 6a and 6b are arranged so as to face each other. Then, in the pair of electrode portions 6a and 6b, the liquid crystal droplet 8 can be moved in a direction orthogonal to the electric field EF formed between the electrodes by applying a DC voltage between the selected opposing electrodes. Therefore, the movement direction of the liquid crystal droplet 8 can be controlled by appropriately selecting an electrode to which a DC voltage is applied. For example, in the pair of electrode portions 6a and 6b, the liquid crystal droplet 8 can be moved in the direction of the arrow X by applying a DC voltage between the electrodes arranged along the dotted line LL in FIG. . Further, in the pair of electrode portions 6a and 6b, the liquid crystal droplet 8 can be moved in the direction of arrow Y by applying a DC voltage between the electrodes arranged along the dotted line SL in FIG. .

(Shape of moving medium 2)
The shape of the moving medium 2 is not particularly limited. For example, as shown in FIG. 1, a moving medium 2 can be formed by arranging a pair of flat plates 2p and 2p so that a gap is formed between them. Further, a moving medium 2 may be formed by forming a groove or the like in a block-shaped member. That is, if it has the structure provided with the flow path which has a pair of opposing wall which moves a liquid crystal, it can be used as the moving medium 2. FIG.

  Moreover, the flow path 2h of the moving medium 2 may not be linear, may be curved, may be crank-shaped, or the like. Since the liquid crystal droplet 8 can be freely deformed, the liquid crystal droplet 8 can move along the flow channel 2h while being deformed even in the flow channel 2h as described above.

  The moving medium 2 may be formed of a flexible member that can be bent or bent. That is, the moving medium 2 that can change its shape by bending or bending may be used. Even in that case, since the liquid crystal droplet 8 can be freely deformed, the liquid crystal droplet 8 can move along the moving medium 2 while being deformed.

(Moving medium 2 of other configuration)
Further, the moving medium 2 does not necessarily need to be a solid, and may be any medium that can hold the liquid crystal droplet 8 in a movable state while maintaining the form of the droplet. For example, as shown in FIG. 4, a liquid 2L or the like that does not mix with liquid crystal such as water may be accommodated in a container 2p such as a container or a pipe as the moving medium 2A. In this case, as shown in FIG. 4, a pair of electrode portions 6a and 6b are disposed outside (or inside) the container 2p with respect to the liquid 2L in which the liquid crystal droplet 8 is immersed, and the pair of electrode portions 6a and 6b. DC voltage is applied to Then, since the electric field EF can be formed in the liquid 2L positioned between the pair of electrode portions 6a and 6b, the liquid crystal droplet 8 in the liquid 2L can be moved along the direction intersecting the electric field EF.

  In this configuration, there is no alignment film or the like that contacts the liquid crystal droplets 8. However, since the alignment of the liquid crystal molecules in the liquid crystal droplet 8 is determined by the interface effect determined by the physical properties of the liquid crystal constituting the liquid crystal droplet 8 and the liquid 2L, the liquid crystal droplet 8 is aligned in the alignment direction when the electric field EF is applied. You will move accordingly. In addition, the orientation of the liquid crystal molecules in the liquid crystal droplets 8 can be adjusted by applying a magnetic field to the liquid crystal droplets 8 immersed in the liquid 2L. Then, the moving direction of the liquid crystal droplet 8 can be controlled to some extent from the outside.

In order to confirm the operation of the liquid crystal droplet actuator of the present invention, it was confirmed that the liquid crystal droplets arranged in a uniform electric field move continuously.
In the experiment, the actuator shown in FIG. 5 was manufactured, and the movement of the liquid crystal droplets in this actuator was confirmed.

  The actuator was composed of a cell arranged so as to form a gap between two glass substrates (20 mm × 20 mm) and a liquid crystal arranged in the gap between the cells.

  A glass substrate used for a cell is provided with an electrode portion (ITO electrode) formed of an ITO film on its surface (surfaces facing each other). In addition, a horizontal alignment film (JALS-2021-R25 manufactured by JSR Corporation) is provided on the surface of the glass substrate on which the ITO electrode is formed so that liquid crystal molecules are aligned horizontally with respect to the surface of the glass substrate by spin coating. Formed.

  A liquid crystal (nematic liquid crystal (4-Cyano-4'-n-penty-biphenll (5CB)) was placed in the gap between the glass substrates of the cell using a micropipette. When viewed from the orthogonal direction, an amount that the diameter of the liquid crystal droplets was 100 μm was supplied (see FIG. 5B and FIG. 6).

  In this actuator, a direct current voltage and a pulse voltage were applied between the ITO electrodes of the two glass substrates to confirm the behavior of the liquid crystal droplets. The pulse voltage was applied at a frequency of 1, 10, 100 Hz and a duty ratio (duty ratio) of 50%.

  When the pulse voltage was applied, the movement of the liquid crystal droplet was photographed at 200 fps (pixel resolution 512 × 512) using a high speed camera (manufactured by IDT) from the direction orthogonal to the glass substrate (see FIG. 5B). ). When a DC voltage was applied, the image was taken at 30 fps (pixel resolution 1028 × 768) using a USB camera (manufactured by Imaging Source: model number DFK 61AUC02) from a direction orthogonal to the glass substrate (see FIG. 5B). ). FIG. 6 shows a schematic diagram (FIG. 6A) of the photographed liquid crystal droplet and a conceptual diagram (FIG. 6B) when the photographed liquid crystal droplet image is binarized.

The results are shown in FIGS.
7 and 8, the initial barycentric position of the liquid crystal droplet is indicated by a white x mark, and the barycentric position at each time t is indicated by a black x mark. In addition, the movement analysis of the gravity center position was performed using commercially available moving image analysis software (manufactured by DITECT: DipMotion).

  FIG. 7 shows a case where a pulse voltage (90 V: frequency f = 10 Hz) is applied (interval of ITO electrodes is 6 μm). However, by applying a voltage, liquid crystal droplets are negative in the x-axis direction (in FIG. 7). It can be confirmed that it is driving in the left direction.

  FIG. 8 shows a case where a DC voltage (40 V) is applied (ITO electrode interval is 18 μm). By applying a voltage, liquid crystal droplets are driven in the negative direction of the x axis (left direction in FIG. 8). Can be confirmed. That is, it was confirmed that the liquid crystal droplets can be driven by applying a DC voltage, as in the case of applying a pulse voltage.

  FIG. 9A is a diagram comparing the movement of liquid crystal droplets during a period in which a voltage is applied. The experiment was performed under the condition that the interval between the ITO electrodes was 6 μm, and the applied voltage was 90 V for both DC voltage and pulse voltage.

  As shown in FIG. 9A, when a pulse voltage is applied, the movement amount L of the center of gravity position from the initial state (t = 0 s) becomes smaller as the frequency increases. It is confirmed that On the other hand, it is confirmed that the value of the movement amount L at t = 4 s is almost the same regardless of the frequency.

  On the other hand, in the case of a DC voltage, the value of the movement amount L at t = 4 s is longer than that when a pulse voltage is applied, and it can be confirmed that driving is continuous.

  That is, when moving the liquid crystal droplets, it can be confirmed that the DC voltage can be driven more smoothly and efficiently.

(Confirmation of voltage influence)
In addition, the influence of the voltage value of the DC voltage on the movement of the liquid crystal droplets was confirmed by changing the applied voltage between 0 and 140V.
In the experiment, using the same actuator as in Example 1, the moving amount L of the center of gravity position was measured 10 times at each voltage, and the moving speed was confirmed based on the moving amount L and the voltage application time.

  The results are shown in FIG. In FIG. 9B, the average value of 10 movement speeds is indicated by a black circle, and the standard deviation is indicated by an error bar.

  As shown in FIG. 9B, it can be confirmed that the liquid crystal droplet starts moving when the voltage is 30 V or higher, and the moving speed increases as the voltage increases. The voltage of 30 V at which the liquid crystal droplet starts to move is equal to or higher than the voltage at which flow due to electrohydrodynamic instability occurs in the nematic liquid crystal used. From this, it was speculated that a flow due to electrohydrodynamic instability may occur in the liquid crystal droplets, and this flow affects the movement of the liquid crystal droplets.

(Confirmation of flow in liquid crystal droplets)
It was speculated that the flow caused by electrohydrodynamic instability occurred in the liquid crystal droplets when a DC voltage was applied. Therefore, it was confirmed that a flow caused by electrohydrodynamic instability actually occurred in the liquid crystal droplets and the flow state thereof.

  In the experiment, in the same actuator as in Example 1, a nematic liquid crystal mixed with fine particles is arranged in the gap between the glass substrates of the cell to form liquid crystal droplets, and a direct current voltage is applied to the liquid crystal droplets. The flow was confirmed. In the experiment, the interval between the ITO electrodes was 18 μm, and a DC voltage (40 V) was applied.

The results are shown in FIGS.
As shown in FIGS. 10 and 11, it can be confirmed that when a DC voltage is applied, the positions of the fine particles (black dots dispersed in the liquid crystal) mixed in the liquid crystal droplets for visualization are changed. For example, if attention is paid to fine particles surrounded by a circle, it can be confirmed that the positions of the fine particles in the liquid crystal droplets are different depending on the time. From this, it can be confirmed that flow is generated in the liquid crystal droplets by application of the DC voltage.

  Moreover, the result of having confirmed the movement of the microparticles | fine-particles of each part in a liquid crystal droplet is shown in FIG. 12, FIG. In FIGS. 12 and 13, the left and right are reversed from those in FIGS. 10 and 11 due to image processing. That is, the leftward movement in FIGS. 10 and 11 is the rightward movement in FIGS. 12 and 13.

  As shown in FIGS. 12 and 13, it was confirmed that the fine particles in each part in the liquid crystal droplets moved as indicated by arrows.

  From this result, it was guessed that the flow as shown in FIG. That is, as shown in FIG. 2, a flow in the same direction as the liquid crystal droplet traveling direction occurs in the vicinity of the center of the liquid crystal droplet (the flow in the right direction in FIGS. 12 and 13 and the flow in the left direction in FIGS. 10 and 11). . A counterclockwise swirling flow is generated at the upper left portion of the liquid crystal droplet in FIG. 2B, and a clockwise swirling flow is generated at the lower left portion of the liquid crystal droplet in FIG. In the upper part of the liquid crystal droplet in FIG. 2B, a counterclockwise swirl is generated, and in the lower part in FIG. 2B, a clockwise swirl is generated. On the right side of the liquid crystal droplet in FIG. 2B, a swirl flow having the y axis as the rotation axis is generated. As a result, in the liquid crystal droplet, a flow that is vertically symmetrical and macroscopically rightward in FIG. 2B (a rightward flow in FIGS. 12 and 13 and a leftward flow in FIGS. 10 and 11) occurs. It was speculated that this flow led to the driving of liquid crystal droplets. In summary, since the flow in the positive x-axis direction (the right direction in FIGS. 12 and 13, the left direction in FIGS. 10 and 11) has occurred, the liquid crystal droplets are in the positive x-axis direction (FIGS. 12 and 12). This is considered to be driven in the right direction in FIG. 13 and in the left direction in FIGS. 10 and 11.

  The liquid crystal droplet actuator using the flow in the liquid crystal of the present invention can be used for moving an object such as a shaft-shaped member or a plate.

DESCRIPTION OF SYMBOLS 1 Liquid crystal drop actuator 2 Moving medium 2L Liquid 2a Opposite wall surface 2b Opposite wall surface 2h Flow path 4 Alignment film 6 Electrode part 7 Control part 8 Liquid crystal EF Electric field

Claims (6)

Liquid crystal drops,
A moving medium in which the liquid crystal droplets are movably disposed;
An electric field generating unit having a pair of electrode units for applying an electric field to the liquid crystal droplets arranged in the moving medium;
A control unit that applies a DC voltage capable of forming an electric field that generates a flow caused by electrohydrodynamic instability in the liquid crystal droplets between the pair of electrode units of the electric field generation unit. A liquid crystal drop actuator that uses the flow in the liquid crystal. The moving medium is
A moving medium having a pair of opposing wall surfaces and having a flow path in which the liquid crystal droplets are disposed between the pair of opposing wall surfaces;
The pair of electrode portions includes:
When the liquid crystal droplets are sandwiched in the flow path of the moving medium and a DC voltage is applied between the pair of electrode portions, an electric field that intersects the axial direction of the flow path is generated. The liquid crystal droplet actuator using the flow in the liquid crystal according to claim 1. The moving medium is
3. A liquid crystal droplet actuator using a flow in liquid crystal according to claim 1, wherein the liquid crystal droplet has a liquid into which the liquid crystal droplet is immersed. The controller is
4. A liquid crystal droplet actuator using a flow in liquid crystal according to claim 1, wherein the liquid crystal droplet actuator has a function of changing the magnitude of a DC voltage applied between the pair of electrode portions. The controller is
5. A liquid crystal droplet actuator using liquid crystal according to claim 1, wherein the liquid crystal droplet actuator has a function of changing the direction of an electric field generated between the pair of electrode portions. The electric field generating unit includes a plurality of electrode units;
The controller is
6. The flow in liquid crystal according to claim 1, 2, 3, 4, or 5 having a function of applying a DC voltage between selected electrode portions among the plurality of electrode portions. Liquid crystal drop actuator.