PATENT ABSTRACT
A method and apparatus are disclosed wherein a battery comprises an electrode having at least one nanostructured surface. The nanostructured surface is disposed in a way such that an electrolyte fluid of the battery is prevented from contacting the electrode, thus preventing discharge of the battery when the battery is not in use. When a voltage is passed over the nanostructured surface, the electrolyte fluid is caused to penetrate the nanostructured surface and to contact the electrode, thus activating the battery. In one illustrative embodiment, the battery is an integrated part of an electronics package. In another embodiment, the battery is manufactured as a separate device and is then brought into contact with the electronics package. In yet another embodiment, the electronics package and an attached battery are disposed in a projectile that is used as a military targeting device.

PATENT DESCRIPTION
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to batteries and, more particularly, to batteries having at least one nanostructured electrode surface.  
       BACKGROUND OF THE INVENTION  
       [0002]     Many beneficial devices or structures in myriad applications rely on batteries as a power source. As shown in  FIG. 1 , illustrative liquid-cell battery  101 , is characterized by an electrolyte liquid  102  which provides a mechanism for an electrical charge to flow in direction  103  between a positive electrode  104  and a negative electrode  105 . When such a battery  101  is inserted into an electrical circuit  106  with illustrative load  108 , it completes a loop which allows electrons to flow uniformly in direction  107  around the circuit  106 . The positive electrode thus receives electrons from the external circuit  106 . These electrons then react with the materials of the positive electrode  104  in reduction reactions that generate the flow of a charge to the negative electrode  105  via ions in the electrolyte liquid  102 . At the negative electrode  105 , oxidation reactions between the materials of the negative electrode  104  and the charge flowing through the electrolyte fluid  102  result in surplus electrons that are released to the external circuit  106 .  
         [0003]     As the above process continues, the active materials of the positive and negative electrodes  104  and  105 , respectively, eventually become depleted and the reactions slow down until the battery is no longer capable of supplying electrons. At this point the battery is discharged. It is well known that, even when a liquid-cell battery is not inserted into an electrical circuit, there is often a low level reaction with the electrodes  104  and  105  that can eventually deplete the material of the electrodes. Thus, a battery can become depleted over a period of time even when it is not in active use in an electrical circuit. This period of time will vary depending on the electrolyte fluid used and the materials of the electrodes.  
       SUMMARY OF THE INVENTION  
       [0004]     We have realized that it would be extremely advantageous to be able to prevent the discharge of batteries while the batteries are not in use. Additionally, it would be advantageous to be able to variably control when the discharge of the batteries was initiated.  
         [0005]     Therefore, we have invented a method and apparatus wherein a battery comprises an electrode having at least one nanostructured surface. The nanostructured surface is disposed in a way such that an electrolyte fluid of the battery is prevented from contacting the electrode, thus preventing discharge of the battery when the battery is not in use. When a voltage is passed over the nanostructured surface, the electrolyte fluid is caused to penetrate the nanostructured surface and to contact the electrode, thus activating the battery. Accordingly, when the activated battery is inserted into an electrical circuit, electrons will flow along the circuit.  
         [0006]     In one illustrative embodiment, the battery is an integrated part of an electronics package. In another embodiment, the battery is manufactured as a separate device and is then brought into contact with the electronics package. In yet another embodiment, the electronics package and an attached battery are disposed in a projectile that is used as a military targeting device. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0007]      FIG. 1  shows a prior art liquid-cell battery as used in an electrical circuit;  
         [0008]      FIG. 2  shows a prior art nanopost surface;  
         [0009]      FIGS. 3A, 3B ,  3 C,  3 D and  3 E show various prior art nanostructure feature patterns of predefined nanostructures that are suitable for use in the present invention;  
         [0010]      FIG. 4  shows a more detailed view of the prior art nanostructure feature pattern of  FIG. 3C ;  
         [0011]      FIGS. 5A and 5B  show a device in accordance with the principles of the present invention whereby electrowetting principles are used to cause a liquid droplet to penetrate a nanostructure feature pattern;  
         [0012]      FIG. 6  shows the detail of an illustrative nanopost of the nanostructure feature pattern of  FIGS. 5A and 5B ;  
         [0013]      FIG. 7  shows an illustrative liquid-cell battery in accordance with the principles of the present invention wherein the electrolyte in the battery is separated from the negative electrode by nanostructures;  
         [0014]      FIG. 8  shows the illustrative battery of  FIG. 7  wherein the electrolyte in the battery is caused to penetrate the nanostructures and to thus contact the negative electrode;  
         [0015]      FIGS. 9A and 9B  show an illustrative embodiment of the use of the battery of  FIGS. 7 and 8 , respectively, in an electrical circuit having one or more lasers;  
         [0016]      FIGS. 10A and 10B  show how a plurality of the devices of the illustrative embodiment of  FIGS. 9A and 9B  can be disposed in a container, such as a projectile; and  
         [0017]      FIG. 11  shows how the projectiles of  FIGS. 10A and 10B  can be used as a laser designate targets. 
     
    
     DETAILED DESCRIPTION  
       [0018]      FIG. 2  shows an illustrative nanopost pattern  201  with each nanopost  209  having a diameter of less than 1 micrometer. While  FIG. 2  shows nanoposts  209  formed in a somewhat conical shape, other shapes and sizes are also achievable. In fact, cylindrical nanopost arrays have been produced with each nanopost having a diameter of less than 10 nm. Specifically,  FIGS. 3A-3E  show different illustrative arrangements of nanoposts produced using various methods and further show that such various diameter nanoposts can be fashioned with different degrees of regularity. Moreover, these figures show that it is possible to produce nanoposts having various diameters separated by various distances. An illustrative method of producing nanoposts, found in U.S. Pat. No. 6,185,961, titled “Nanopost arrays and process for making same,” issued Feb. 13, 2001 to Tonucci, et al, is hereby incorporated by reference herein in its entirety. Nanoposts have been manufactured by various methods, such as by using a template to form the posts, by various means of lithography, and by various methods of etching.  
         [0019]      FIG. 4  shows the illustrative known surface  401  of  FIG. 3C  with a nanostructure feature pattern of nanoposts  402  disposed on a substrate. Throughout the description herein, one skilled in the art will recognize that the same principles applied to the use of nanoposts or nanostructures can be equally applied to microposts or other larger features in a feature pattern. The surface  401  and the nanoposts  402  of  FIG. 4  are, illustratively, made from silicon. The nanoposts  402  of  FIG. 4  are illustratively approximately 350 nm in diameter, approximately 6 μm high and are spaced approximately 4 μm apart, center to center. It will be obvious to one skilled in the art that such arrays may be produced with regular spacing or, alternatively, with irregular spacing.  
         [0020]     As used herein, unless otherwise specified, a “nanostructure” is a predefined structure having at least one dimension of less than one micrometer and a “microstructure” is a predefined structure having at least one dimension of less than one millimeter. The term “feature pattern” refers to either a pattern of microstructures or a pattern of nanostructures. Further, the terms “liquid,” “droplet,” and “liquid droplet” are used herein interchangeably. Each of those terms refers to a liquid or a portion of liquid, whether in droplet form or not.  
         [0021]     The present inventors have recognized that it is desirable to be able to control the penetration of a given liquid into a given nanostructured or microstructured surface and, thus, control the contact of the liquid with the underlying substrate supporting the nanostructures or microstructures.  FIGS. 5A and 5B  show one embodiment in accordance with the principles of the present invention where electrowetting is used to control the penetration of a liquid into a nanostructured surface. Electrowetting principles are generally described in U.S. patent application Ser. No. 10/403,159 filed Mar. 31, 2003 and titled “Method And Apparatus For Variably Controlling The Movement Of A Liquid On A Nanostructured Surface,”-which is hereby incorporated by reference herein in its entirety.  
         [0022]     Referring to  FIG. 5A , a droplet  501  of conducting liquid (such as an electrolyte solution in a liquid-cell battery) is disposed on nanostructure feature pattern of cylindrical nanoposts  502 , as described above, such that the surface tension of the droplet  501  results in the droplet being suspended on the upper portion of the nanoposts  502 . In this arrangement, the droplet only covers surface area f 1  of each nanopost. The nanoposts  502  are supported by the surface of a conducting substrate  503 . Droplet  501  is illustratively electrically connected to substrate  503  via lead  504  having voltage source  505 . An illustrative nanopost is shown in greater detail in  FIG. 6 . In that figure, nanopost  502  is electrically insulated from the liquid ( 501  in  FIG. 5A ) by material  601 , such as an insulating layer of dielectric material. The nanopost is further separated from the liquid by a low surface energy material  602 , such as a well-known fluoro-polymer. Such a low surface energy material allows one to obtain an appropriate initial contact angle between the liquid and the surface of the nanopost. It will be obvious to one skilled in the art that, instead of using two separate layers of different material, a single layer of material that possesses sufficiently low surface energy and sufficiently high insulating properties could be used.  
         [0023]      FIG. 5B  shows that, by applying a low voltage (e.g., 10-20 volts) to the conducting droplet of liquid  501 , a voltage difference results between the liquid  501  and the nanoposts  502 . The contact angle between the liquid and the surface of the nanopost decreases and, at a sufficiently low contact angle, the droplet  501  moves down in the y-direction along the surface of the nanoposts  502  and penetrates the nanostructure feature pattern until it complete surrounds each of the nanoposts  502  and comes into contact with the upper surface of substrate  503 . In this configuration, the droplet covers surface area f 2  of each nanopost. Since f 2 &gt;&gt;f 1 , the overall contact area between the droplet  501  and the nanoposts  502  is relatively high such that the droplet  501  contacts the substrate  503 .  
         [0024]      FIG. 7  shows an illustrative battery  701  in accordance with the principles of the present invention whereby an electrolyte fluid  702  is contained within a housing having containment walls  703 . The electrolyte fluid  702  is in contact with positive electrode  704 , but is separated from negative electrode  708  by nanostructured surface  707 . Nanostructured surface  707  may be the surface of the negative electrode or, alternatively, may be a surface bonded to the negative electrode. One skilled in the art will recognize that the nanostructured surface could also be used in association with the positive electrode with similarly advantageous results. In  FIG. 7 , the electrolyte fluid is suspended on the tops of the nanoposts of the surface, similar to the droplet of  FIG. 5A . The battery  701  is inserted, for example, into electrical circuit  705  having load  706 . When the electrolyte liquid is not in contact with the negative electrode, there is substantially no reaction between the electrolyte and the electrodes  704  and  705  of the battery  701  and, therefore, there is no depletion of the materials of the electrodes. Thus, it is possible to store the battery  701  for relatively long periods of time without the battery becoming discharged.  
         [0025]      FIG. 8  shows the battery  701  of  FIG. 7  inserted into electrical circuit  705  wherein, utilizing the electrowetting principles described above, a voltage is passed over the nanostructured surface  707  thus causing the electrolyte fluid  702  to penetrate the surface  707  and to come into contact with the negative electrode  708 . One skilled in the art will recognize that this voltage can be generated from any number of sources such as, for example, by passing one or more pulses of RF energy through the battery. When the penetration of the electrolyte into the nanostructures occurs, electrons begin flowing in direction  801  along the circuit  705  as described above and the load  706  is powered. Thus, the embodiment of  FIGS. 7 and 8  show how a battery can be stored without depletion for a relatively long period of time and can then be “turned on” at a desired point in time to power one or more electrical loads in an electrical circuit.  
         [0026]      FIGS. 9A and 9B  show a cross section of an illustrative use of the battery of  FIGS. 7 and 8  in a small electronics package  901 . Specifically, referring to  FIG. 9A , package  901  has a battery portion (having a positive electrode  904 , negative electrode  908 , nanostructured surface  907 , and electrolyte fluid  902 ) electrically connected to an illustrative laser portion (having lasers  906 ). One skilled in the art will recognize that package  901  may be an integrated device formed entirely from one material, such as a silicon wafer or, alternatively, the battery portion may be formed separately and later connected in the manufacturing process to the laser portion of the package  901 . The package  901  shown in cross-section in  FIGS. 9A and 9B  can be illustratively manufactured as a device of any size in any desired geometric shape (e.g., a square, circle, rectangle, etc). Advantageously, the package  901  may be manufactured such that surface  910  has a surface area of 1 mm 2  to 100 mm 2 . One skilled in the art will recognize that a variety of shapes having a variety of surface areas will be advantageous in various applications.  
         [0027]     As described previously, referring to  FIG. 9B , when a voltage is passed over nanostructured surface  907 , the electrolyte fluid  902  penetrates the surface  907  and contacts electrode  908 . Once again, this voltage can be generated by an RF pulse generated external to the battery. Reactions between the electrodes  904  and  908  begin and an electrical current begins flowing along the electrical circuit connecting the battery to the lasers  906 . Thus, lasers  906  begin emitting light.  
         [0028]      FIGS. 10A and 10B  and  11  show one illustrative use for the electronics package of  FIGS. 9A and 9B . Specifically, referring to  FIG. 1A , a container  1001 , such as a projectile, is filled with an adhesive liquid  1002  in which a plurality of the electronics packages  901  of  FIGS. 9A and 9B  are disposed. The adhesive liquid is illustratively a gel that has a long shelf life (i.e., having a viscosity that will not change over a relatively long period of time) and which functions to maintain a separation distance between the plurality of electronics packages  901 . The projectile is, illustratively, formed from a polymeric material such as a common PVC or ABS plastic material. An illustrative liquid suitable for use in the embodiment of  FIGS. 10A and 10B  is a soft adhesive in the urethane-based elastomeric adhesive family. Prior to being used, the battery portions of the electronics packages  901  are not active and the lasers do not emit light, similar to the embodiment of  FIG. 9A  as described above. However, referring to  FIG. 10B , when it is desired that the lasers begin to emit light, device  1005  generates one or more RF energy pulses  1004  that are passed through the container  1001 , thus passing a voltage over the nanostructured surfaces  907  of  FIG. 9B  and causing the electrolyte in the batteries of packages  901  to contact both electrodes  904  and  908  of  FIG. 9B . Accordingly, as in the embodiment of  FIG. 9B , lasers  906  begin to emit light. One skilled in the art will recognize that, if the projectile of  FIGS. 10A and 10B  is a projectile fired from a gun, device  1005  may be a component of the gun that generates RF pulses to activate the lasers of the packages  901 . As used herein, gun is defined as a handgun, a rifle, a cannon, slingshot or any other such device suitable for launching a projectile toward a target. Alternatively, for example where the projectile is thrown by hand, any suitable RF energy-generating device may be used to active the lasers of the electronics packages  901 .  
         [0029]      FIG. 11  shows how, when the projectile  1001  of  FIGS. 10A and 10B  contacts a surface  1101 , illustratively the surface of a vehicle, the projectile breaks apart and the liquid  1002  adheres to the surface  1101 . Hence, the light emitting packages  901  within the liquid also adhere to the surface  1101  of the vehicle. Some military ordinance, particularly bombs and/or missiles dropped from airborne platforms, are adapted to home into laser light of a particular frequency. One skilled in the art will therefore recognize that the light-emitting packages  906  can thus be used as a military laser targeting device that these bombs or missiles can home into. One skilled in the art will also recognize that this form of laser targeting device have advantages over currently-used laser targeting systems. For example, one current system relies on manual “painting” of a target with a laser. In this case, a person on the ground must remain in proximity with the target and shine a laser onto the target, thus placing the person in jeopardy of being discovered or injured. Another current system relies on an aircraft to paint the target with the laser. However, this requires the aircraft to once again remain in the proximity of the target until the bomb or missile strikes the target. This is similarly undesirable.  
         [0030]     The projectiles of  FIGS. 10A and 10B  have the advantage that they can be fired at a vehicle and act as self-generating laser emitters. Thus neither a person nor an aircraft is required to paint the target with a laser. Additionally, one skilled in the art will recognize that the laser emitters of  FIGS. 10A and 10B  do not have to be activated prior to firing the projectile. Instead, the projectiles may be fired and the inactive emitters attached to a surface  1101 , as shown in  FIG. 11 . Then, at a later time an RF energy pulse can be generated by any suitable source that will activate the laser emitters. One skilled in the art will also recognize that different laser signals can be emitted by the laser packages in different projectiles, such as by using different encryption of the signals, thus allowing target differentiation by different ordinance.  
         [0031]     The foregoing merely illustrates the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are within its spirit and scope. For example, one skilled in the art, in light of the descriptions of the various embodiments herein, will recognize that the principles of the present invention may be utilized in widely disparate fields and applications. All examples and conditional language recited herein are intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting aspects and embodiments of the invention, as well as specific examples thereof, are intended to encompass functional equivalents thereof.