Abstract:
A liquid lens includes a sealed shell, a gaseous material, a transparent carbon nanotube structure within the gaseous material, a liquid material, and a first electrode and a second electrode, a voltage being applied to the carbon nanotube structure causes rapid heating, which is transferred to the gaseous material to change the pressure thereof.

Description:
RELATED APPLICATIONS 
     This application claims all benefits accruing under 35 U.S.C. §119 from China Patent Application No. 201210180545.6, filed on Jun. 4, 2012 in the China Intellectual Property Office, entire contents of which is hereby incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to liquid lens, and particularly to a liquid lens with a carbon nanotube structure. 
     2. Description of Related Art 
     By controlling the meniscus (the surface of the liquid), a liquid lens uses one or more fluids to create a lens of infinitely variable shapes in relation to a focal length and other optical properties without any moving parts. There are two primary types of liquid lenses—transmissive and reflective, which are not to be confused with liquid-formed lenses that are created by placing a drop of plastic or epoxy on a surface and then allowed to be hardened into a lens shape. 
     According to different structures and principles, liquid lenses can be roughly classified into three types: (1) double liquid layer liquid lens based on electro-wetting principle; (2) single liquid layer liquid lens which shape can be changed by mechanical force; and (3) liquid crystal lens which reflective ratio can be changed by applying an electric field to change the alignment of the liquid crystals of the liquid crystal lens. 
     Compared with traditional variable-focus lenses, the liquid lens has less mechanical structures. Liquid lenses are small, quick responding, energy efficient, and durable. Therefore, liquid lenses have been widely applied in the fields of mobile phone, digital camera, as electronically controllable variable focus systems. 
     However, double liquid layer liquid lenses usually have complex structures, and high costs. Single liquid layer liquid lenses are difficult to control, and have poor stabilities. Liquid crystal lenses having high costs may limit the applications of the liquid crystal lenses. 
     Therefore, a liquid lens of a lower cost, higher precision, higher efficiency, and user friendly is desired within the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the embodiments can be better understood with reference 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 embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  shows a cross-sectional view of a liquid lens of one embodiment. 
         FIG. 2  shows one carbon nanotube structure of the liquid lens of  FIG. 1 . 
         FIG. 3  shows another carbon nanotube structure of the liquid lens of  FIG. 1 . 
         FIG. 4  shows one carbon nanotube structure of the liquid lens of  FIG. 1 . 
         FIG. 5  is a Scanning Electron Microscope (SEM) image of a drawn carbon nanotube film. 
         FIG. 6  shows a cross-sectional view of a liquid lens of another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean “at least one.” 
       FIG. 1  is one embodiment of a liquid lens  10 . The liquid lens  10  includes a sealed shell  110 , a gaseous material  120 , a liquid material  130 , a carbon nanotube structure  140 , a first electrode  150  and a second electrode  160 . The gaseous material  120  and the liquid material  130  are sealed in the sealed shell  110 , and separated with each other by a membrane  115 . The carbon nanotube structure  140  is sealed in the sealed shell  110 , and intermixed with the gaseous material  120 . The carbon nanotube structure  140  is spaced with the liquid material  130  by the membrane  115 . About 50% to 90% of the volume of the sealed shell  110  is filled with the liquid material  130 , and an air space is defined in the sealed shell  110 . The air space is full with the gaseous material  120 . The air space occupies about 10% to about 50% of the volume of the sealed shell  110 . The first electrode  150  and the second electrode  160  are separately located at two opposite sides of the sealed shell  110 , and are electrically connected to the carbon nanotube structure  140 . A voltage can be applied to the carbon nantotube structure  130  via the first electrode  150  and the second electrode  160  to cause heating of the gaseous material  120 . 
     The sealed shell  110  holds the gaseous material  120 , the liquid material  130  and the carbon nanotube structure  140 . The sealed shell  110  includes a hard portion  112  and a soft portion  114 . In one embodiment, the hard portion  112  is a cylinder; the soft portion  114  is half convex shape structure. 
     The hard portion  112  is made of rigid materials, such as glass, quartz, plastic or resin. The rigid materials of the hard portion  112  make sure the hard portion  112  would not easy to deform, the efficiency and stability of liquid lens  10  is maintained. In one embodiment, the hard portion  112  is made of a transparent non-conductive hard glass. The soft portion  114  is made of flexible materials. The flexible material make sure the soft portion  114  can be deformed under small pressure, to achieve the purpose of changing the focus length of the liquid lens  10 . The flexible material can be a flexible polymer material, such as polytene, polypropylene, polymethylmethacrylate. In one embodiment, the soft portion  114  is made of a polymethylmethacrylate membrane. In one embodiment, the soft portion  114  has a convex shape, and defines a convex surface  113 . The diameter of the sealed shell  110  can be in a range from about 10 millimeter to about 10 centimeters. 
     The material of the liquid material  130  is not limited to a single material or type of material, and can be electrolyte solution, solution of non-electrolyte, organic solution, inorganic solution, hydrophilic solution and oleophylic solution. In one embodiment, the liquid material  130  is preferable an oleophylic solution with high viscosity. When the liquid material  130  has a high viscosity, a contacting angle between the liquid material  130  and the sealed shell  110  is great, so the liquid lens  10  can have a wide focus length adjustable range. In one embodiment, the viscosity of the oleophylic solution greater than 10 12  Pa·s. 
     The liquid material  130  is located in the soft portion  114  of the sealed shell  110 . The volume of the liquid material  130  is equal to or less than the volume of the soft portion  114 . In one embodiment, the volume of the liquid material  130  is equal to the volume of the soft portion  114 . 
     The gaseous material  120  is a nonoxidizing gas, such as nitrogen, hydrogen, or inert gas. In one embodiment, the gaseous material  120  is argon. The pressure of the gaseous material  120  is in a range from 0.5 atmospheres to 1.5 atmospheres. 
     The membrane  115  is a transparent thin flexible film used to separate the gaseous material  130  with the liquid material  130 . The membrane  115  can be made of plastic, resin, or polymer. 
     The first electrode  150  and the second electrode  160  are in electrical contact with the carbon nanotube structure  140 , and a voltage can be applied to the carbon nanotube structure  140  via the first electrode  150  and the second electrode  160 . The first electrode  150  and the second electrode  160  are made of conductive material. The shapes of the first electrode  150  and the second electrode  160  are not limited and can be lamellar, rod, wire, and block like, among other shapes. A material of the first electrode  150  and the second electrode  160  can be metal, conductive adhesive, carbon nanotube, and indium tin oxide, among other conductive materials. In one embodiment, the first electrode  150  and the second electrode  160  are lamellar metal. 
     The carbon nanotube structure  140  has a low heat capacity per unit area, which is less than or equal to about 1.7×10 −6  J/cm 2 *K. The temperature of carbon nanotube structure  140  changes rapidly in response to voltage changes applied to the carbon nanotube structure  140 . 
     The carbon nanotube structure  140  is transparent and free-standing sheet structure which is also flexible. The carbon nanotube structure  140  can be permeated by the gaseous material  120  and supported by the first electrode  150  and the second electrode  160 . In one embodiment, opposite sides of carbon nanotube structure  140  are fixed on the first electrode  150  and the second electrode  160  by a conductive adhesive. The size of the carbon nanotube structure  140  is not limited, provided there is complete physical contact with the liquid material  130 . The thickness of the carbon nanotube structure can be in a range from about 10 nanometers to about 50 micrometers. The heat capacity per unit area of the carbon nanotube structure  140  can be less than 2×10 −4  J/cm 2 *K. In one embodiment, the heat capacity per unit area of the carbon nanotube structure  140  is less than or equal to about 1.7×10 −6  J/cm 2 *K. 
     Referring to  FIG. 2  to  FIG. 5 , the carbon nanotube structure  140  can be a single drawn carbon nanotube film  132 , or more than one drawn carbon nanotube films  132  stacked on each other. The drawn carbon nanotube film  132  can be obtained by pulling from a carbon nanotube array. The drawn carbon nanotube film  132  includes a plurality of carbon nanotubes joined end to end by van der Waals force along a same direction. The drawn carbon nanotube film  132  includes a plurality of successive and ordered carbon nanotubes  134  joined end-to-end lengthwise by van der Waals force therebetween. The thickness of the drawn carbon nanotube film  132  can be in a range from about 10 nanometers to about 500 nanometers. The drawn carbon nanotube film  132  is a free-standing film. The term “free-standing” includes, but is not limited to, a structure that does not require support from or by a substrate or other foundation and can sustain its own weight when it is hoisted by a portion thereof without damage to the structural integrity of the whole film. 
     The carbon nanotube structure  140  can include a plurality of carbon nanotube drawn films  132  stacked with each other. Adjacent drawn carbon nanotube films  132  combine by van der Waals force. An angle between the aligned directions of the carbon nanotubes in two adjacent carbon nanotube films  132  can range from about 0 degrees to about 90 degrees. When the carbon nanotube structure  140  includes more than one drawn carbon nanotube films  132  stacked on each other, the mechanical strength and toughness of the carbon nanotube structure  140  is increased, but the transparency of the carbon nanotube structure  140  is decreased. Therefore, the number of layers of the carbon nanotube films  132  should be limited to less than 10 layers. In one embodiment, the carbon nanotube structure  140  includes three layers of drawn carbon nanotube films  132 .  FIG. 3  shows that in one embodiment, the carbon nanotube structure  140  includes three layers of drawn carbon nanotube films  132 . The angle between the aligned directions of the carbon nanotubes in two adjacent carbon nanotube films  132  is 0 degrees. Referring to  FIG. 4 , in one embodiment, the angle between the aligned directions of the carbon nanotubes in two adjacent carbon nanotube films  132  is 90 degrees. 
     The carbon nanotubes  134  of the drawn carbon nanotube film  132  are aligned lengthwise along a same direction. The carbon nanotubes  134  of at least one drawn carbon nanotube film  132  of the carbon nanotube structure  140  are aligned in line from the first electrode  150  to the second electrode  160 . The high electrical conductivity of the carbon nanotubes  134  along the lengthwise direction promotes the efficient working of the liquid lens  10 . 
     The liquid lens  10  has a fixed focal length when there is no voltage applied on the carbon nanotube structure  140 .  FIG. 1  shows that when a voltage is applied on the carbon nanotube structure  140 , the temperature of the carbon nanotube structure  140  is increased. The carbon nanotube structure  140  transfers heat to the gaseous material  120 , and the temperature of the gaseous material  120  increases. The gaseous material  120  will be heated by the carbon nanotube structure  140  and thus expand. Therefore, a pressure would be applied on the liquid material  130 , and the shape of the soft portion  114  changes. The focus length of the liquid lens  10  changes with the shape change of the soft portion  114 . Therefore the focal length of the liquid lens  100  can be adjusted by changing the voltage applied to the carbon nanotube structure  140 . 
       FIG. 6  shows that another embodiment of present disclosure provides a liquid lens  20 . The liquid lens  20  includes a sealed shell  210 , a gaseous material  120 , a carbon nanotube structure  140 , a first electrode  150 , a second electrode  160 , a membrane  115 , a first liquid material  230 , and a second liquid material  232 . The gaseous material  120 , the first liquid material  230 , the second liquid material  232  and the carbon nanotube structure  140  are located inside of the sealed shell  210 . The carbon nanotube structure  140  is embedded in the gaseous material  120 , and spaced with the first liquid material  230  and the second liquid material  232 . The gaseous material  120  is separated by the first liquid material  230  and the second liquid material  232  via the membrane  115 . The first electrode  150  and the second electrode  160  are electrically connected with the carbon nanotube structure  140 . 
     The sealed shell  210  holds the gaseous material  120 , the first liquid material  230 , the second liquid material  232 , and the carbon nanotube structure  140 . The sealed shell  210  is made of a rigid material, such as glass, quartz, plastic, or resin, for example. The rigid materials of the sealed shell  210  make sure the sealed shell  210  does not easily deform, the efficiency and stability of liquid lens  20  is maintained. In one embodiment, the sealed shell  210  is made of a transparent non-conductive hard glass. 
     The sealed shell  210  can be a tube shape, such as cylinder. The diameter of the sealed shell can be in a range from about 1 millimeter to about 10 centimeters. In one embodiment, the diameter of the sealed shell is 1 centimeter. 
     Further, an internal surface  213  of the sealed shell  210  is hydrophilic and lipophobic. 
     The first liquid material  230  and the second liquid material  232  are transparent. The density of the first liquid material  230  is less than the density of the second liquid material  232 . The first liquid material  230  is oleophylic. The second liquid material  232  is hydrophilic. The first liquid material  230  is located between the gaseous material  120 , and the second liquid material  232 . The first liquid material  230  is contacted with the second liquid material  232 . 
     The first liquid material  230  is oleophylic, and the second liquid material  232  is hydrophilic. Because the internal surface  213  of the sealed shell  210  is hydrophilic and lipophobic, the interface between the first liquid material  230  and the second liquid material  232  forms a convex surface. Therefore, the focus length of the liquid lens  20  can be adjusted by the interface between the first liquid material  230  and the second liquid material  232 . 
     It is to be understood that the above-described embodiments are intended to illustrate rather than limit the disclosure. Variations may be made to the embodiments without departing from the spirit of the disclosure as claimed. It is understood that any element of any one embodiment disclosed can be incorporated with any other embodiment. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.