# Patent

## Title
CNT-based actuator, lens module using same and camera module using same

## Abstract

An exemplary CNT-based actuator includes a first electrode, a second electrode opposite to the first electrode, and a CNT layer sandwiched between the first electrode and the second electrode. The CNT layer includes two opposite surfaces in contact with the first and the second electrodes respectively, and a plurality of CNTs substantially parallel to each other. The first electrode and the second electrode are configured for cooperatively creating therebetween an electric field with an electric field direction substantially parallel to the CNTs so as to adjust a thickness of the CNT layer, thereby moving the second electrode relative to the first electrode.

## Background
BACKGROUND
1. Technical Field
The present invention relates to actuators, and particularly to a carbon nanotube (CNT) based actuator.
2. Description of Related Art
Camera modules use actuators to achieve a zooming or auto-focusing function. Typical actuators include, for example, stepper motors. When employing such actuators, it is usually necessary to use a gear assembly to transform the rotational movement of the actuators into a linear movement. However, the existence of the gear assembly generally renders the camera modules unduly bulky. Furthermore, the occurrence of backlash/recoil in the gear assembly may result in degraded focusing accuracy.
Therefore, a new actuator is desired to overcome the above mentioned problems.
SUMMARY
An exemplary CNT-based actuator includes a first electrode, a second electrode opposite to the first electrode, and a CNT layer sandwiched between the first electrode and the second electrode. The CNT layer includes two opposite surfaces in contact with the first and the second electrodes respectively, and a plurality of CNTs substantially parallel to each other. The first electrode and the second electrode are configured for cooperatively creating therebetween an electric field with an electric field direction substantially parallel to the CNTs so as to adjust a thickness of the CNT layer, thereby moving the second electrode relative to the first electrode.



BRIEF DESCRIPTION OF THE DRAWINGS
Many aspects of the embodiments can be better understood with references to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
FIG. 1 is a schematic, side cross-sectional view of a CNT-based actuator in accordance with a first embodiment.
FIG. 2 is a schematic view of a CNT-based actuator system in accordance with a second embodiment.
FIG. 3 is a schematic, side cross-sectional view of a lens module in accordance with a third embodiment.
FIG. 4 is a schematic, perspective view of a CNT-based actuator in accordance with a fourth embodiment.
FIG. 5 is a schematic, side cross-sectional view of a camera module in accordance with a first embodiment.



DETAILED DESCRIPTION OF THE EMBODIMENTS
Embodiments will now be described in detail below with reference to the drawings.
Referring to FIG. 1, a CNT-based actuator 10 is shown. The actuator includes a first electrode 102, a second electrode 106, and a CNT layer 104 sandwiched between the first electrode 102 and the second electrode 106. The CNT layer 104 includes a first surface and an opposite second surface. The first and the second surfaces contact with the first electrode 102 and the second electrode 106, respectively. The CNT layer 104 includes a plurality of CNTs 108.
When a voltage is applied to the first electrode 102 and the second electrode 106, an electric field is formed therebetween. In the present embodiment, the first electrode 102 and the second electrode 106 are plate electrodes with a planar surface facing each other. The direction of the electric field at any given point between the electrodes 102, 106 is substantially perpendicular to the surface of the first electrode 102. That is, the direction of the electric field is substantially parallel to the Z axis. The CNTs 108 undergo an electrostrictive deformation under the electric field. Hence, the CNT layer 104 extends along the Z axis, and then drives the first electrode 102 to move away from the second electrode 106. When the second electrode 106 is fixed, the CNT layer 104 drives the first electrode 102 to move along a positive direction of the Z axis. When the voltage is removed from the first and second electrodes 102, the CNT layer 104 restores to an initial thickness, and the first electrode 102 returns to an original position relative to the second electrode 106.
The voltage can be in an approximate range from 0.1 Voltages (V) to 100 V, and particularly in a range from 0.5 V to 4 V The amount of elongation of the CNT-based actuator 10 can be in a range from 50 μm to 500 μm, and, particularly in a range from 100 μm-400 μm. In other words, the distance the first electrode 102 moves relative to the second electrode 106 is in a range from 50 μm to 500 μm. In the present embodiment, the elongation range of the CNT-based actuator 10 is from 100 μm-400 μm.
The first electrode 102 and the second electrode 106 can be made of a material selected from a group consisting of aluminum, copper, silver, copper aluminum alloy, and silver copper alloy. The thickness of the CNT layer 104 is in a range from 0.1 millimeters to 10 centimeters. The CNT layer 104 can be a single layer of CNT array or a plurality of stacked layers of CNT array. In the present embodiment, the CNT layer 104 is a single layer of CNT array. The CNT 108 can be a single-walled CNT or a multi-walled CNT. A central axis of the CNT 108 is substantially perpendicular to the surface of the first electrode 102, and substantially parallel to the Z axis. The CNT 108 has a high elastic modulus. Accordingly, the reliability of the CNT-based actuator 10 is high.
A method for making the CNT-based actuator 10 is also provided.
Firstly, a CNT array is grown. The CNT array can be made employing the method as below: providing a substrate; depositing a catalyst (e.g., iron, cobalt, or nickel) on a surface of the substrate; placing the substrate with the catalyst in a furnace; heating the furnace to a temperature of 500° C. to 750° C.; supplying a mixture of a carbon containing gas (e.g., C2H2, C2H4, or C2H6) and a protecting gas into the furnace; growing a plurality of CNTs on the substrate such that the CNT array is formed on the substrate. The height of the CNT 108 is in a range from 100 μm-500 μm.
Secondly, the CNT array is pulled off from the substrate using a pulling tool (e.g., a tweezer).
Thirdly, the CNT array is directly disposed on the surface of the first electrode 102, thus forming the CNT layer 104.
Finally, the second electrode 106 is placed directly on a surface of the CNT layer 104, and pressed hard towards the first electrode 102.
Referring to FIG. 2, a CNT-based actuator system 30 includes a CNT-based actuator 20, a drive circuit 304, and a controller 306.
The CNT-based actuator 20 includes a first electrode 202, a second electrode 206, a CNT layer 204 sandwiched between the first electrode 202 and the second electrode 206, a two actuator heads 208 formed on the first electrode 208.
An input of the drive circuit 304 is electrically connected with the controller 306, and is configured for receiving a control signal from the controller 306. The output of the drive circuit 304 is electrically connected with the first electrode 202 and the second electrode 206, respectively. The drive circuit 304 is configured for applying a direct voltage to the first electrode 202 and the second electrode 206.
In operation, when the second electrode 206 is fixed, the controller 306 sends a control signal to the drive circuit 304 based on a distance that the first electrode (or the actuator heads 208) needs to move. In response to the control signal, the drive circuit 304 applies a voltage to the first electrode 202 and the second electrode 206. The voltage generates an electric field between the first electrode 202 and the second electrode 206. Then the CNT layer 204 extends along the Z axis, and drives the first electrode 202 and the actuator head 208 to move a predetermined distance along the Z axis.
Referring to FIG. 3, a lens module 40 according to a third embodiment is shown. The lens module 40 includes a barrel 402, a first lens 404, a plurality of CNT-based actuators 10, and a second lens 406. The first lens 404 is secured in the barrel 402, and the second lens 406 is movably disposed in the barrel 402. The first lens 404 includes a first optically active part 4042 and a first optically inactive part 4044 surrounding the first active part 4042. The second lens 406 includes a second optically active part 4062 and a second optically inactive part 4064 surrounding the second optically active part 4062. The CNT-based actuators 10 are symmetrically arranged between the first optically inactive part 4044 and the second optically inactive part 4064. The first electrode 102 and the second electrode 106 are firmly connected with first optically inactive part 4044 and the second optically inactive part 4064 respectively. The CNT-based actuator 10 is configured for driving the second lens 406 to move along a negative direction of the Z axis, changing a distance between the first lens 404 and the second lens 406, thus achieving a zooming function.
In the third embodiment, the lens module 40 employs a plurality of CNT-based actuators 10. Alternatively, the lens module 40 can use a single CNT-based actuator 50 shown in FIG. 4. The CNT-based actuator 50 is similar to the CNT-based actuator 10, except that the CNT-based actuator 50 is annular with a through hole 502 defined therein. The outer diameter of the CNT-based actuator 50 is less than or equal to the inner diameter of the barrel 402. The through hole 502 aligns with the first optically active part 4042 and the second optically active part 4062. The through hole 502 allows light passing therethrough.
The CNT-based actuator 10 performs a linear movement. Therefore, there is no need to use a gear assembly to convert a rotation movement to a linear movement. Furthermore, the occurrence of backlash/recoil in the gear assembly is eliminated.
Referring to FIG. 5, a camera module 60 according to a fifth embodiment is shown. The camera module 60 includes a barrel 602, a first lens 604, a spacer 606, a second lens 608, a plurality of CNT-based actuator 10, a holder 610, and an image sensor 612. The first lens 604, the spacer 606 and the second lens 608 are sequentially received in the barrel 602, and cooperatively form a lens module with the barrel 602. The barrel 602 has an annular flange 6022 extending outward from an outer surface of a sidewall thereof. The image sensor 612 is received in the holder 610. Each CNT-based actuator 10 is sandwiched between one end of the holder 610 and the annular flange 6022. The first electrode 102 and the second electrode 106 are firmly connected to the annular flange 6022 and the end of the holder 610. The CNT-based actuator 10 is configured for driving the lens module to move along the positive direction of the Z axis, and changing a distance between the lens module and the image sensor 612, thus achieving an auto-focusing function.
In the above fifth embodiment, the camera module 60 includes a plurality of CNT-based actuators 10. Alternatively, the camera module can adopt a single CNT-based actuator similar to the CNT-based actuator 50. In this case, the inner diameter of the CNT-based actuator should be larger than or equal to the outer diameter of the barrel 602, and the barrel 602 is nested in the CNT-based actuator.
While certain embodiments have been described and exemplified above, various other embodiments from the foregoing disclosure will be apparent to those skilled in the art. The present invention is not limited to the particular embodiments described and exemplified but is capable of considerable variation and modification without departure from the scope of the appended claims.

## Claims

1. A CNT-based actuator comprising:
a first electrode;
a second electrode opposite to the first electrode; and
a CNT layer sandwiched between the first electrode and the second electrode, the CNT layer comprising two opposite surfaces in contact with the first and the second electrodes respectively and a plurality of CNTs substantially parallel to each other, wherein the first electrode and the second electrode are configured for cooperatively creating therebetween an electric field with an electric field direction substantially parallel to the CNTs, the CNTs generating an electrostrictive deformation along the electric field direction under the electric field, thereby moving the second electrode relative to the first electrode.

2. The CNT-based actuator as claimed in claim 1, wherein the CNT layer is a single layer of a CNT array.

3. The CNT-based actuator as claimed in claim 1, wherein the CNT layer is a plurality of stacked layers of CNT arrays.

4. The CNT-based actuator as claimed in claim 1, wherein each CNT is a single-walled CNT or a multi-walled CNT.

5. The CNT-based actuator as claimed in claim 1, wherein each of the first and the second electrodes is a plate electrode with a planar surface.

6. The CNT-based actuator as claimed in claim 5, wherein the electric field direction is substantially perpendicular to the planar surface of the first electrode.

7. The lens module as claimed in claim 1, wherein the CNT-based actuator is annular with a through hole defined therein.

8. A lens module comprising:
a barrel;
a first lens fixedly disposed in the barrel, the first lens comprising a first optically active part and a first optically inactive part surrounding the first optically active part;
a second lens movably received in the barrel, the second lens comprising a second optically active part and a second optically inactive part surrounding the second optically active part; and
a CNT-based actuator sandwiched between the first and the second optically inactive parts, the CNT-based actuator comprising:
a first electrode;
a second electrode opposite to the first electrode; and
a CNT layer sandwiched between the first electrode and the second electrode, the CNT layer comprising two opposite surfaces in contact with the first and the second electrodes respectively and a plurality of CNTs substantially parallel to each other, wherein the first electrode and the second electrode are configured for cooperatively creating therebetween an electric field with an electric field direction substantially parallel to the CNTs, the CNTs generating an electrostrictive deformation along the electric field direction under the electric field, thereby moving the second electrode relative to the first electrode.

9. The lens module as claimed in claim 8, wherein the CNT-based actuator is annular with a through hole defined therein, and the through hole aligns with the first optically active part and the second optically active part.

10. The lens module as claimed in claim 8, wherein the first and the second electrodes are fixedly connected with the first and the second optically inactive part respectively.

11. The CNT-based actuator as claimed in claim 8, wherein the CNT layer is a single layer of a CNT array.

12. The CNT-based actuator as claimed in claim 8, wherein the CNT layer is a plurality of stacked layers of CNT arrays.

13. A camera module comprising:
a barrel;
a lens received in the barrel;
a holder;
an image sensor accommodated in the holder; and
a CNT-based actuator sandwiched between the barrel and the holder, the CNT-based actuator comprising:
a first electrode in contact with the barrel;
a second electrode opposite to the first electrode and in contact with the holder; and
a CNT layer sandwiched between the first electrode and the second electrode, the CNT layer comprising two opposite surfaces in contact with the first and the second electrodes respectively and a plurality of CNTs substantially parallel to each other, wherein the first electrode and the second electrode are configured for cooperatively creating therebetween an electric field with an electric field direction substantially parallel to the CNTs, the CNTs generating an electrostrictive deformation along the electric field direction under the electric field, thereby driving the barrel to move relative to the holder.

14. The camera module as claimed in claim 13, wherein the barrel comprises a cylindrical side wall and an annular flange extending outwardly from an outer surface of the side wall, the CNT-based actuator is sandwiched between the holder and the annular flange.

15. The camera module as claimed in claim 14, wherein the first and the second electrodes are fixedly connected with the annular flange and the holder respectively.

16. The camera module as claimed in claim 13, wherein the CNT-based actuator is annular with a through hole defined therein, and the barrel is surrounded by the CNT-based actuator.

17. The camera module as claimed in claim 13, wherein the CNT layer is a single layer of a CNT array.

18. The camera module as claimed in claim 13, wherein the CNT layer is a plurality of stacked layers of CNT arrays.

19. The CNT-based actuator as claimed in claim 1, wherein the CNT layer extends along a direction perpendicular to the first electrode and the second electrode, the CNT layer moves the second electrode away from the first electrode along the direction.

20. The lens module as claimed in claim 8, wherein the CNT layer extends along a direction perpendicular to the first electrode and the second electrode, the CNT layer moves the second electrode away from the first electrode along the direction.