Abstract:
A liquid lens includes a sealed shell, a liquid material, a transparent carbon nanotube structure within the 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 liquid material to change the density thereof, and the refractive index of the liquid material is thus changed.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims all benefits accruing under 35 U.S.C. §119 from China Patent Application No. 201210180562.X, filed on Jun. 4, 2012 in the China Intellectual Property Office, entire contents of which is hereby incorporated by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to liquid lens, and particularly to a liquid lens with a carbon nanotube structure. 
         [0004]    2. Description of Related Art 
         [0005]    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. 
         [0006]    According to different structures and principles, liquid lenses can be roughly classified into three types: (1) double liquid layer liquid lens based on electrowetting 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. 
         [0007]    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. 
         [0008]    However, double liquid layer liquid lenses usually have complex structures, and high costs. Single liquid layer liquid lenses are hard to control, and have poor stabilities. Liquid crystal lenses having high costs may limit the applications of the liquid crystal lenses. 
         [0009]    Therefore, a liquid lens of a lower cost, higher precision, higher efficiency, and easies to control may be desired within the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    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. 
           [0011]      FIG. 1  shows a cross-sectional view of a liquid lens of one embodiment. 
           [0012]      FIG. 2  shows one carbon nanotube structure of one embodiment of the liquid lens of  FIG. 1 . 
           [0013]      FIG. 3  shows another carbon nanotube structure of another embodiment of the liquid lens of  FIG. 1 . 
           [0014]      FIG. 4  shows one carbon nanotube structure of one embodiment of the liquid lens of  FIG. 1 . 
           [0015]      FIG. 5  is a Scanning Electron Microscope (SEM) image of a drawn carbon nanotube film used in the liquid lens of  FIG. 1 . 
           [0016]      FIG. 6  shows a cross-sectional view of the liquid lens of  FIG. 1  in an application. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    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.” 
         [0018]      FIG. 1  is one embodiment of a liquid lens  10 . The liquid lens  10  includes a sealed shell  110 , a liquid material  120 , a carbon nanotube structure  130 , a first electrode  140  and a second electrode  150 . The liquid material  120  and the carbon nanotube structure  130  are sealed in the sealed shell  110 , and intermixed with each other. About 50% to 100% of the volume of the sealed shell  110  is filled with the liquid material  120 , and an air space  112  is defined in the sealed shell  110 . The air space  112  occupies about 0% to about 50% of the volume of the sealed shell  110 . In one embodiment, The air space  112  occupies about 10% to about 50% of the volume of the sealed shell  110 . The first electrode  140  and the second electrode  150  are separately located at two opposite sides of the sealed shell  110 , and are electrically connected to the carbon nanotube structure  130 . A voltage can be applied to the carbon nantotube structure  130  via the first electrode  140  and the second electrode  150  to cause heating of the liquid material  120 . 
         [0019]    The sealed shell  110  holds the liquid material  120  and the carbon nanotube structure  130 . The sealed shell  110  is transparent and made of rigid materials, such as glass, quartz, plastic or resin. In one embodiment, the sealed shell  110  is made of a transparent non-conductive hard glass. The shape of the sealed shell  110  is variable, and the sealed shell  110  can be used to focus light. In one embodiment, the sealed shell  110  has a convex shape, and includes two opposite convex surfaces  113  opposite to each other. The diameter of the sealed shell  110  can be in a rage from about 10 millimeter to about 10 centimeters. The thickness of the sealed shell  110  can be in a range from about 5 millimeters to about 1 centimeter. In one embodiment, the diameter of the convex shaped sealed shell  110  is about 1 centimeter, and the thickness of the sealed shell  110  is about 3 millimeters. 
         [0020]    The material of the liquid material  120  is not limited to a single material or type of material, and the resistivity of the liquid material  120  is greater than the resistivity of the carbon nanotube structure  130 . The carbon nanotube structure  130  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  130  changes rapidly in response to voltage changes applied to the carbon nanotube structure  130 . The focal length of the liquid lens  10  changes with the voltage applied on the carbon nanotube structure  130 . Thus, the response speed of the liquid lens  10  is almost instantaneous. In one embodiment, the resistivity of the liquid material  120  is greater than 0.01 Ohm*M. 
         [0021]    The liquid material  120  can be a solution of non-electrolyte, water, or organic solvent. The water can be pure water, tap water, or sea water. The organic solvent can be methanol, ethanol or acetone. In one embodiment, liquid material  120  is pure water. The refractive index of liquid material  120  is sensitive to temperature or density change. 
         [0022]    The first electrode  140  and the second electrode  150  are in electrical contact with the carbon nanotube structure  130 , and a voltage can be applied to the carbon nanotube structure  130  via the first electrode  140  and the second electrode  150 . The first electrode  140  and the second electrode  150  are made of conductive material. The shapes of the first electrode  140  and the second electrode  150  are not limited and can be lamellar, rod, wire, and blocklike, among other shapes. A material of the first electrode  140  and the second electrode  150  can be metal, conductive adhesive, carbon nanotube, and indium tin oxide, among other conductive materials. In one embodiment, the first electrode  140  and the second electrode  150  are lamellar metal. 
         [0023]    The carbon nanotube structure  130  is transparent and free-standing sheet structure which is also flexible. The carbon nanotube structure  130  can be embedded in the liquid material  120  and supported by the first electrode  140  and the second electrode  150 . In one embodiment, opposite sides of carbon nanotube structure  130  are fixed on the first electrode  140  and the second electrode  150  by a conductive adhesive. The size of the carbon nanotube structure  130  is not limited, provided there is complete physical contact with the liquid material  120 . 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  130  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  130  is less than or equal to about 1.7×10 -6  J/cm 2 *K. 
         [0024]    Referring to  FIG. 2  to  FIG. 5 , the carbon nanotube structure  130  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 attractive 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 attractive 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. 
         [0025]    The carbon nanotube structure  130  can include a plurality of carbon nanotube drawn films  132  stacked with each other. Adjacent drawn carbon nanotube films  132  combine by just the van der Waals attractive force therebetween. 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  130  includes more than one drawn carbon nanotube films  132  stacked on each other, the mechanical strength and toughness of the carbon nanotube structure  130  is increases, but the transparency of the carbon nanotube structure  130  is decreased. Therefore, the number of layers of the carbon nanotube films  132  should limited to  10  layers. In one embodiment, the carbon nanotube structure  130  includes three layers of drawn carbon nanotube films  132 . Referring to  FIG. 3 , in one embodiment, the carbon nanotube structure  130  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. 
         [0026]    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  130  are aligned in line from the first electrode  140  to the second electrode  150 . The high electrical conductivity of the carbon nanotubes  134  along the lengthwise direction promote the efficient working of the liquid lens  10 . 
         [0027]    The liquid lens  10  has a fixed focal length when there is no voltage applied on the carbon nanotube structure  130 . Referring to  FIG. 6 , when a voltage is applied on the carbon nanotube structure  130 , the liquid material  120  is heated, and the density of the liquid material  120  changes with the temperature. The refractive index of the liquid material  120  changes with the change in density. Therefore the focal length of the liquid lens  100  can be adjusted by changing the voltage applied to the carbon nanotube structure  130 . 
         [0028]    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.