Patent Publication Number: US-2009217963-A1

Title: Photovoltaic apparatus for charging a portable electronic device and method for making

Description:
FIELD 
     The present invention generally relates to portable electronic devices and more particularly to photovoltaic cells for charging a portable electronic device and a method for making the photovoltaic cells. 
     BACKGROUND 
     The market for personal portable electronic devices, for example, cell phones, laptop computers, personal digital assistants (PDAs), digital cameras, and music playback devices (MP3), is very competitive. Manufacturers, distributors, service providers, and third party providers have all attempted to find features that appeal to the consumer. For example, manufacturers are constantly improving their product with each model in the hopes it will appeal to the consumer more than a competitor&#39;s product. Battery life is one area in which improvements are sought. 
     Rechargeable batteries are currently the primary power source for cell phones and various other portable electronic devices. The energy stored in the batteries is limited. Energy storage is determined by the energy density (Wh/L) of the storage material, its chemistry, and the volume of the battery. For example, a typical Li ion cell phone battery with a 250 Wh/L energy density, and a 10 cc battery would store 2.5 Wh of energy. Depending upon usage, the energy could last for a few hours to a few days. Recharging often requires access to an electrical outlet. The limited amount of stored energy and the frequent recharging are major inconveniences associated with batteries. Accordingly, there is a need for longer lasting cell phone power sources that are recharged easily. One approach to fulfill this need is to have a hybrid power source with a rechargeable battery and a method to trickle-charge the battery. Important considerations for an energy conversion device to recharge the battery include power density, size, and the efficiency of energy conversion. 
     Energy harvesting methods such as solar cells, thermoelectric generators using a temperature gradient, and mechanical/kinetic generators using mechanical motion are very attractive power sources to trickle charge a battery. However, the energy generated by these methods is often small, usually only a few milliwatts to approximately a few hundred milliwatts depending on size, efficiency, nature of the energy source, etc. In the regime of interest, namely, a few hundred milliwatts to a few watts, this dictates that a sizeable volume or area is required to generate sufficient power for trickle charge. Such methods include coupling the battery to a solar panel (photovoltaic cell). See for example, U.S. Pat. No. 5,898,932 issued on 27 Apr. 1999. 
     Photovoltaic cells are well known for providing electricity from solar panels in both small scale distributed power systems and centralized megawatt scale power plants. Photovoltaic cells also have found applications in consumer electronics, e.g., portable electronic equipment such as calculators and watches. The cells operate without toxic or noise emissions, and require little maintenance. These cells may also be used as sensors for detection of a wide band of radiation. 
     Photovoltaic cells originally developed by the Bell Telephone Laboratories in the 1950&#39;s were, and most of the larger cells produced today are, crystalline silicon based because of the availability of high quality silicon which is produced in large quantities by the semiconductor industry. Amorphous silicon may be found in low power sources in portable electronic devices, even though solar conversion efficiency is limited. 
     There are several key issues in the use of photovoltaic (PV) cells for portable applications. These issues include cost, robustness, stability, toxicity of materials used, and efficiency (for example, electron transport). 
     Accordingly, it is desirable to provide an apparatus for charging a battery of a portable electronic device efficiently. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and 
         FIGS. 1-4  are cross sectional views of the exemplary embodiment illustrating fabrication process steps; 
         FIG. 5  is a top view of the exemplary embodiment of  FIG. 4  taken along line  5 - 5 ; 
         FIG. 6-7  are cross sectional views of another exemplary embodiment illustrating fabrication process steps; 
         FIG. 8  is a top view of the exemplary embodiment of  FIG. 7  taken along line  8 - 8 ; 
         FIG. 9  is a flow chart of the process steps for fabricating the exemplary embodiment; 
         FIG. 10  is an isometric view of a portable communication device configured to incorporate the exemplary embodiments; 
         FIG. 11  is an isometric back view of the portable communication device taken along line  11 - 11  of  FIG. 10  and in accordance with an exemplary embodiment; 
         FIG. 12  is a block diagram of one possible portable communication device of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description. 
     Using a photovoltaic cell to trickle-charge the portable electronic device battery is attractive because it extends the battery life and enables emergency use of the phone in situations when the portable electronic device battery is depleted and the outlet charging capability is not readily available. Additionally, using a photovoltaic cell for trickle charging the portable electronic device battery may also find use in situation when power from the electrical grid is not available in the developing countries. However, one of the most important issues in photovoltaic cells is the transport of electrons and holes upon photo-excitation. For example, in the traditional dye-sensitized photovoltaic technology, the photo-excited electrons have to migrate on an average of several micron-meters in the porous TiO 2  layer before reaching the electrodes. As such, the probability of those electrons recombining with holes is high. In order to improve the efficiency, the transport of photo-excited electrons needs to be improved. 
     The exemplary embodiment described herein overcomes electron/hole transport efficiency issues found in the dye-sensitized photovoltaic cells. When feature sizes ranging from nanometers to micrometers, volumetrically interdigitated electrodes reduce distances between electrodes significantly, resulting in improved electron/hole transport. Dry or wet processes, or a combination thereof, may be used in the exemplary self-assembly process. The self-assembly manufacturing process is cost effective compared to lithographic methods. The interdigitated electrodes may also help to guide light deep in the cells in addition to conducting charges, thereby improving optical absorption efficiency. 
     One exemplary embodiment of the photovoltaic cell includes the interdigitated electrodes formed by anodizing a material such as a layer of tin metal foil formed on a substrate (bottom electrode), which is preferably conducting, to create a porous non-absorptive conducting layer (for example, tin oxide or fluorinated tin oxide) having a plurality of fingers defining a plurality of pores, or cavities, having sidewalls over either a layer of active charge transport material, for example, an oxide such as titanium oxide or zinc oxide. An insulating material, for example, silicon oxide, magnesium oxide, or aluminum oxide, is formed over the tin oxide covering the conducting and active transparent materials while exposing the pores. The active charge transport material on the sidewalls is then coated with a sensitizer material, for example dye molecules and/or Quantum dots, for absorbing light and creating electron/hole pairs. The sensitizer material is then coated with an electrolyte material, for example a polymer based electrolyte, and the space remaining within the pores is filed with a conducting electrode material, which may be either transparent or non-light absorbing, having catalyst particles embedded therein, for example, indium tin oxide nano-particles mixed with a small amount of platinum particles either by layering or by uniformly mixing the two. A capping electrode material, for example, indium tin oxide, is formed over the insulating material and the top of the sensitizer material, the electrolyte material, and the transparent conducting electrode material within the pores. Light enters the photovoltaic cell through either the top or bottom electrode, or both sides, and/or the electrode material, and impacts the sensitizer material. A voltage appears across, and a current flows from, the capping electrode material and the bottom electrode. 
     While the above described exemplary embodiment forms layers from the conducting material towards the center of the pore, another exemplary embodiment includes forming the conducting material as a post and forming the layers on and away from the post. 
       FIGS. 1-5  describe the process steps for forming the photovoltaic cell in accordance with the exemplary embodiment. Referring to  FIG. 1 , a conductive material  102  is formed on a substrate  104  and anodized to form a plurality of fingers  106  having a top surface  108  and sidewalls  110  defining a plurality of pores  112 . While the shape of the pores is shown as cylindrical (circular), it should be understood the shape may comprise any shape, for example, square or rectangular, and the size and shape of the pores can be optionally changed by chemical etching and/or other patterning methods. The substrate  104  may be transparent and may be conductive. After anodization, in which the treatment material  102  is oxidized, it becomes a conductive material. Optionally, after the anodizing step, a chemical treatment step may be carried out to enhance the conductivity of the anodized oxide. When anodized and treated, the fingers  106  comprise an oxide, preferably tin oxide, doped tin oxide, or indium tin oxide. 
     The sidewalls  110  are coated with an active transport material  114  such as titanium oxide or zinc oxide. The active transport material  114  formed may have a thin film morphology with smooth or rough surface, or a particle morphology with particle size ranging from 1 nm to 50 nm, or a combination of both. The active transport material  114  may be formed by vapor phase (such as Atomic layer deposition, CVD), chemical (such as layer-by-layer, sol-gel) or electrochemical (such as electrodeposition, and electrophoretic) deposition methods, preferably by immersing the structure  100  in a solution with oxide precursors for a period of time. 
     An insulating layer  116  ( FIG. 2 ) is formed on the top surface  108  of the fingers  106  and the exposed top portion  118  of the active transport material  114 . The insulating layer  116  may be, for example, silicon oxide, aluminum oxide, and magnesium oxide. The structure  200  is immersed in another solution to coat a sensitizer material  122  on the active transport material  114 . Alternatively, the sensitizer material  122  may also be coated by vapor phase processes. The sensitizer material  122  is a material that converts light for generating electron/hole pairs. 
     The sensitizer material  122  is preferably organic dye molecules and/or quantum dots, which are sometimes called semiconductor nanocrystallites, whose radii are smaller than the bulk exciton Bohr radius and constitute a class of materials intermediate between molecular and bulk forms of matter. The organic molecules and quantum dots efficiently absorb light, e.g., sun light, and generate electron/hole pairs upon light absorption, they can also be dissolved into various solutions prior to being applied to the structure  200 . The sensitizer layer  122  is formed on the active transport layer  114 , preferably by, but not limited to, immersing the structure  200  in a solution containing dye complexes and/or quantum dots. The time of immersion can vary from a few minutes to a few days depending on temperature and solution concentration. The dye molecules can be ruthenium complexes where one of the ligands is typically 4,4′-dicarboxy-2,2′-bipyridyl. The quantum dots may be groups of II-VI, III-V, IV, or IV-VI materials, for example, CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, GaAs, GaP, GaAs, GaSb, HgS, HgSe, HgTe, InAs, InP, InSb, AlAs, AlP, AlSb. Alternative quantum dots that may be used include but are not limited to tertiary microcrystals such as InGaP and ZnSeTe, ZnCdS, ZnCdSe, and CdSeS. Multi-core structures are also possible such as ZnSe/ZnXS/ZnS, where X represents Ag, Sr, Te, Cu, or Mn. The inner most core is made of ZnSe, followed by the second core layer of ZnXS, completed by an external shell made of ZnS. 
     The structure  200  is then immersed in a solution to coat the sensitizer material  122  with an electrolyte material  124  ( FIG. 3 ). Alternatively, the thin electrolyte layer  124  can also be formed on the sensitizer material using the vapor-phase based processes. The remaining area of the pores  112  is then filled with a material  126  comprising a conductive electrode material that is either transparent or non-absorbing to light (non-light absorbing) and a small amount of catalysts used for electrochemical reactions. In the preceding steps, any of the active transparent material  114 , sensitizer material  122 , electrolyte material  124 , and mixture of transparent conductive electrode material and catalysts ( 126 ) forming on the top surface  108  or insulating layer  116  may be removed in any manner known in the industry, such as applying an ion beam at a grazing angle to strike the undesired accumulation. The electrolyte material  124  may be, for example, an electrolyte gel such as the ionic liquid electrolyte gels described by Wang, et al. ( Chem. Commun.  2002, 2972-2973), or a polymer gel electrolyte with or without metal oxide nanoparticles fillers such as described by Akhtar et al. ( IEEE Proceedings,  2006, 1568-1571), or sol-gel based electrolyte gels such as described by An et al. ( Electrochem. Commun.  2006, 8(1), 170-172) and Joseph, et al. ( Semiconductor Sci. and Technol.  2006, 21, 697-701). The transparent conductive electrode material  126  may be, for example, indium tin oxide, doped tin oxide or other forms of transparent conducting materials. The catalyst can be platinum, carbon, mixture of platinum and carbon, for example, but preferably is platinum nano-particles. 
     A capping electrode material  132  is formed over the insulating material  116  and the exposed sensitizer material  122 , electrolyte material  124 , and conductive electrode material and catalyst  126 . The capping electrode material  132  may comprise any conductive material; however, preferably is transparent indium tin oxide. An optional protective layer  134  may be formed over the capping electrode material  132 . The protective layer  134  may be, for example, glass or a transparent polymer with anti-reflective property.  FIG. 5  is a top view of the structure photovoltaic cell  400  taken along the lines  5 - 5  of  FIG. 4 . Although there are only eight photovoltaic cells shown, it is understood there may be many more in one device. 
     In this exemplary embodiment, the active transport material  114 , electrolyte material  124 , and mixture of conductive electrode material and catalyst  126 , and one or both of the conductive material  102  (including the substrate  104 ) and the capping electrode material  132  (including the protective layer  134 ) are formed as a transparent or non-light absorbing material. In operation, the photovoltaic cell is exposed to light, or radiation which may be outside of the visible spectrum. Light enters the structure  400  through either or both the transparent conductive material  102  (including the optional substrate  104 ) and the capping electrode material  132  (including the optional protective layer  134 ). This light passes through the conductive electrode material  126  and the electrolyte material  124  to strike the sensitizer material  122 , creating electron/hole pairs. The electrons migrate to the conductive material  102  via the active transport material  114 , while the holes migrate to the capping electrode material  132  via the electrolyte material  124  and the conductive electrode material  126 . The transparent conductive materials  106  and  126  formed in this manner provide a volumetrically interdigitated structure. 
     In another exemplary embodiment, the substrate  104  or protective layer  134  is opaque so that light and radiation enter only from one side of structure  400 . 
     In yet another exemplary embodiment, the polymer-based electrolyte  124  is replaced by a sacrificial layer of polymer that serves as a spacer layer between the sensitizer material  122  and the transparent conducting electrode material  126 . The sacrificial polymer layer provides the space necessary for the electrolyte. Upon completion of the filling the transparent or non-light absorbing conducting electrode material  126  inside the pores, the sacrificial polymer layer is replaced by electrolyte through an exchange process. 
     Referring to  FIG. 6 , in still another embodiment, a conductive material  202  is formed on a substrate  204  to form a top surface  208  and sidewalls  210  defining a plurality of posts  211 . While the shape of the posts  211  is shown as cylindrical (circular), it should be understood the shape may comprise any shape, for example, square or rectangular, and the size and shape of the posts can be optionally changed by chemical etching and/or other patterning methods. The substrate  204  may be transparent and may be conducting. After an oxidation treatment, material  202  becomes a transparent or non-light absorbing conductive material. Optionally, after the oxidation step, a chemical treatment step may be carried out to enhance the conductivity of the oxide. When oxidized and treated, the posts  211  comprise an oxide, preferably tin oxide, doped tin oxide, or indium tin oxide. 
     The sidewalls  210  are coated with an active transport material  214  such as titanium oxide or zinc oxide. The active transport material  214  formed may have a thin film morphology with smooth or rough surface, or a particle morphology with particle size ranging from 1 nm to 50 nm, or a combination of both. The active transport material  214  may be formed by vapor phase (such as Atomic layer deposition, CVD), chemical (such as layer-by-layer, sol-gel) or electrochemical (such as electrodeposition, and electrophoretic) deposition methods, preferably by immersing the structure  600  in a solution with oxide precursors for a period of time. 
     An insulating layer  216  is formed on the top surface  208  of the posts  211  and the exposed top portion  218  of the active transport material  214 . The insulating layer  216  may be, for example, silicon oxide, aluminum oxide, and magnesium oxide. The structure  600  is immersed in another solution ( FIG. 7 ) to coat a sensitizer material  222  on the active transport material  214 . Alternatively, the sensitizer material  122  may be formed by a vapor phase processes. The sensitizer material  122  is a material that converts light for generating electron/hole pairs. 
     The sensitizer material  222  is preferably organic dye molecules and/or quantum dots, which are sometimes called semiconductor nanocrystallites, whose radii are smaller than the bulk exciton Bohr radius and constitute a class of materials intermediate between molecular and bulk forms of matter. The organic molecules and quantum dots efficiently absorb light, e.g., sun light, and generate electron/hole pairs upon light absorption, they can also be dissolved into various solutions prior to being applied to the structure  600 . The sensitizer layer  222  is formed on the active transport layer  214 , preferably by, but not limited to, immersing the structure  200  in a solution containing dye complexes and/or quantum dots. The time of immersion can vary from a few minutes to a few days depending on temperature and solution concentration. The dye molecules can be ruthenium complexes where one of the ligands is typically 4,4′-dicarboxy-2,2′-bipyridyl. The quantum dots may be groups of II-VI, III-V, IV, or IV-VI materials, for example, CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, GaAs, GaP, GaAs, GaSb, HgS, HgSe, HgTe, InAs, InP, InSb, AlAs, AlP, AlSb. Alternative quantum dots that may be used include but are not limited to tertiary microcrystals such as InGaP and ZnSeTe, ZnCdS, ZnCdSe, and CdSeS. Multi-core structures are also possible such as ZnSe/ZnXS/ZnS, where X represents Ag, Sr, Te, Cu, or Mn. The inner most core is made of ZnSe, followed by the second core layer of ZnXS, completed by an external shell made of ZnS. 
     The structure  700  is then immersed in a solution to coat the sensitizer material  222  with an electrolyte material  224  ( FIG. 7 ). Alternatively, the thin electrolyte layer  224  can also be formed on the sensitizer material using the vapor-phase based processes. The remaining area surrounding the posts  211  is then filled with a material  226  comprised mostly transparent or non-light absorbing conductive electrode material and a small amount of catalysts used for electrochemical reactions. In the preceding steps, any of the active transport material  214 , sensitizer material  222 , electrolyte material  224 , and mixture of transparent conductive electrode material and catalysts  226  forming on the top surface  208  or insulating layer  216  may be removed in any manner known in the industry, such as applying an ion beam at a grazing angle to strike the undesired accumulation. The electrolyte material  224  may be, for example, an electrolyte gel such as the ionic liquid electrolyte gels described by Wang, et al. ( Chem. Commun.  2002, 2972-2973), or a polymer gel electrolyte with or without metal oxide nanoparticles fillers such as described by Akhtar et al. ( IEEE Proceedings,  2006, 1568-1571), or sol-gel based electrolyte gels such as described by An et al. ( Electrochem. Commun.  2006, 8(1), 170-172) and Joseph, et al. ( Semiconductor Sci. and Technol.  2006, 21, 697-701). The transparent conductive electrode material  226  may be, for example, indium tin oxide, doped tin oxide or other forms of transparent conducting materials. The catalyst can be platinum, carbon, mixture of platinum and carbon, etc. but preferably is platinum nano-particles. 
     A capping electrode material  232  is formed over the insulating material  216  and the exposed sensitizer material  222 , electrolyte material  224 , and conductive electrode material and catalyst  226 . The capping electrode material  232  may comprise any conductive material; however, preferably is transparent indium tin oxide. An optional protective layer  234  may be formed over the capping electrode material  232 . The protective layer  234  may be, for example, glass or a transparent polymer with anti-reflective property.  FIG. 8  is a top view of the structure photovoltaic cell  800  taken along the lines  8 - 8  of  FIG. 7 . Although there are only eight photovoltaic cells shown, it is understood there may be many more in one device. 
     In this exemplary embodiment, the active transport material  214 , electrolyte material  224 , and mixture of conductive electrode material and catalyst  226 , and one or both of the conductive material  202  (including the substrate  204 ) and the capping electrode material  232  (including the protective layer  234 ) are formed as a transparent or non-light absorbing material. In operation, the photovoltaic cell is exposed to light, or radiation which may be outside of the visible spectrum. Light enters the structure  800  through either or both the transparent conductive material  202  (including the optional substrate  204 ) and the capping electrode material  232  (including the optional protective layer  234 ). This light passes through the conductive electrode material  226  and the electrolyte material  224  to strike the sensitizer material  222 , creating electron/hole pairs. The electrons migrate to the conductive material  202  via the active transport material  214 , while the holes migrate to the capping electrode material  232  via the electrolyte material  224  and the conductive electrode material  226 . The transparent conductive materials  206  and  226  formed in this manner provide a volumetrically interdigitated structure. 
     In another exemplary embodiment, the substrate  204  or protective layer  234  is opaque so that light and radiation enter only from one side of structure  800 . 
     In yet another exemplary embodiment, the polymer-based electrolyte  224  is replaced by a sacrificial layer of polymer that serves as a spacer layer between the sensitizer material  222  and the transparent conducting electrode material  226 . The sacrificial polymer layer provides the space necessary for the electrolyte. Upon completion of the filling the transparent or non-light absorbing conducting electrode material  226  inside the pores, the sacrificial polymer layer is replaced by electrolyte through an exchange process. 
     The process of the exemplary embodiments is shown in the flow chart of  FIG. 9 . A conductive material is formed  902  having a top surface  108 ,  208  of a conductive material  106 ,  211  and sidewalls  110 ,  210 . The sidewalls  110 ,  210  are coated  904  with an active transport material  114 ,  214 . The top surface  108 ,  208  of the conductive material  106 ,  206  is coated  906  with an insulating material  116   216  and the active transport material  114 ,  214  on the sidewall  110 ,  210  is coated  908  with a sensitizer material  122 ,  222 . The sensitizing material  122 ,  222  is coated  910  with an electrolyte material  124 ,  224  and the remaining unoccupied area within the pore  112  or around the post  211  is filled  912  with conductive electrode material mixed with a catalyst  126 ,  226 . A capping electrode material  134 ,  234  is formed  914  over the top of the structure  900 . 
       FIG. 10  is an isometric view of an electronic device  1010  comprising a display  1012 , a control panel  1014  including a plurality of touch keys  1016 , and a speaker  1018 , all encased in a housing  1020 . The electronic device  1010  may be any type of device requiring a battery as the main source of power or as a back-up source of power. For the exemplary embodiment of a mobile communication device, a Lithium ion battery is preferred; however, any type of rechargeable battery may be charged by the method described herein. Some electronic devices  1010 , e.g., a cell phone, may include other elements such as an antenna, a microphone, and a camera (none shown). Furthermore, while the preferred exemplary embodiment of an electronic device is described as a mobile communication device, for example, cellular telephones, messaging devices, and mobile data terminals, other embodiments are envisioned, for example, personal digital assistants (PDAs), computer monitors, gaming devices, video gaming devices, cameras, and DVD players. 
       FIG. 11  is an isometric view of the electronic device  1110  taken along line  2 - 2  of  FIG. 1 . In accordance with an exemplary embodiment, photovoltaic cells  1112  are disposed within the housing  1020  and contiguous to the back side  1114  of the housing  1020 . 
     Referring to  FIG. 12 , a block diagram of an electronic device  1210  such as a cellular phone is depicted. Though the exemplary embodiment is a cellular phone, the display described herein may be used with any electronic device in which information, colors, or patterns are to be presented through light emission. The portable electronic device  1210  includes an antenna  1212  for receiving and transmitting radio frequency (RF) signals. A receive/transmit switch  1214  selectively couples the antenna  1212  to receiver circuitry  1216  and transmitter circuitry  1218  in a manner familiar to those skilled in the art. The receiver circuitry  1216  demodulates and decodes the RF signals to derive information therefrom and is coupled to a controller  1220  for providing the decoded information thereto for utilization in accordance with the function(s) of the portable communication device  1210 . The controller  1220  also provides information to the transmitter circuitry  1218  for encoding and modulating information into RF signals for transmission from the antenna  1212 . As is well-known in the art, the controller  1220  is typically coupled to a memory device  1222  and a user interface  1014  to perform the functions of the portable electronic device  1210 . Power control circuitry  1226  is coupled to the components of the portable communication device  1210 , such as the controller  1220 , the receiver circuitry  1216 , the transmitter circuitry  1218  and/or the user interface  1014 , to provide appropriate operational voltage and current to those components. The user interface  1014  includes a microphone  1228 , a speaker  1018  and one or more touch key inputs  1016 . The user interface  1014  also includes a display  1012  which could receive touch screen inputs. The photovoltaic cells  812  are coupled to charge the battery  1230  and may be coupled in series or parallel depending on the voltage and current requirements. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.