Patent Document

CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Patent Application Ser. No. 61/842,055, filed Jul. 2, 2013 and entitled WATERPROOFED DIGITAL DETECTOR, the entirety of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates generally to the field of medical imaging and more particularly relates to apparatus and methods for providing a portable wireless digital radiographic detector that is highly resistant to bodily liquids and moisture during normal handling and operation. 
       BACKGROUND 
       [0003]    With the advent of portable wireless digital radiography (DR) detectors, hospitals and other healthcare facilities now have expanded capability for obtaining x-ray images, including images obtained at the patient bedside. Unlike conventional radiographic image detectors, the wireless DR detectors can be positioned about the patient in a number of positions, without the concern for extending wires between the detector and image acquisition and power electronics. Portability with wireless operation also makes these devices suitable for use in veterinary imaging, since the DR detector can be flexibly positioned and there are no external wires that could be chewed or otherwise damaged during handling and positioning about the animal subject. It is also possible to use the DR detector in various outdoor environments, under a range of weather conditions. 
         [0004]    In conventional use as well as in veterinary, outdoor, and industrial and security imaging environments, however, the portable DR detector can be susceptible to ingress of bodily liquids, chemical liquids in the imaging area, and moisture. Even with careful sealing and liquid ingress prevention techniques, there still exists some risk to the detector if moisture or bodily fluids are able to seep into the housing interior and interfere with internal detector circuitry. To combat this problem, DR detector design may make use of a number of seals, o-rings, gaskets, and similar features intended to prevent moisture ingress. This adds cost and complexity to the mechanical design of the DR detector. Gasketed surfaces, for example, need to be meticulously ground and polished and mating surfaces must meet tight tolerances for uniformity, with a significant number of fasteners properly tightened in order that seals function properly. Reassembly requires considerable care in the event that the detector is disassembled for replacement of a battery or other component. 
         [0005]    Encasement of the detector in a plastic envelope or other waterproof sleeve is a poor solution to the problem. Conventional liquid-tight sealing methods are also air-tight, sealing in heat and potentially causing an overheating condition that can degrade the life of electronic components and performance. In addition, some methods for obtaining a liquid-tight seal can compromise wireless signal transmission and reception. 
         [0006]    Conventional liquid-proofing methods may be unsatisfactory solutions for a number of reasons. Gaskets and seals exhibit wear over time and their performance can be degraded by various factors, such as by disinfectant solutions and exposure to ultraviolet (UV) light, for example. Encasement of the detector within a container or envelope is not a suitable solution for every environment and would require constant replacement of the containment device. Standard sealant coatings would have a limited applicability and lifetime, subject to damage from scratching and abrasion. Moreover, a complete seal would not be feasible with many DR detectors, because there may be some type of input/output port provided for connecting data transfer wires, power cables, and connectors for other functions. 
         [0007]    Levels of water resistance for electrical equipment and components are typically described by an IPX-rating, as defined in ANSI/IEC (American National Standards Institute/International Electrotechnical Commission) test specification ANSI/IEC 60529-2004 entitled “Degrees of Protection Provided by Enclosures”. In the IPX rating system, a scale of values indicates relative protection from moisture, with higher values indicating correspondingly higher levels of protection. For example, a value of IPX-0 indicates virtually no protection from water. A value of IPX-4 indicates protection against splashing. A value of IPX-6 indicates protection against a high-pressure water stream. A value of IPX-8 indicates protection under continuous submersion. It can be appreciated that it would be beneficial to provide a high level of protection against liquid ingress for a DR detector, without adding significant cost, weight, or complexity to the device. At the same time, waterproofing and liquid proofing methods should have little or no impact on performance and functional requirements of the DR detector device related to sensitivity, image quality, interoperability, cooling, electrical connection, and component accessibility. 
       SUMMARY 
       [0008]    An aspect of this application is to advance the art of medical digital radiography and to address, in whole or in part, at least the foregoing and other deficiencies of the related art. 
         [0009]    It is another aspect of this application to provide in whole or in part, at least the advantages described herein. 
         [0010]    Certain exemplary embodiments of the application address the need for a waterproofing solution that enables the portable DR detector to be used in environments where there may be liquids from the patient or other source that need to be restricted from entry into internal portions of the detector. Advantageously, embodiments of the application can eliminate at least some of the gasketing and sealing concerns for protecting the DR detector from liquid damage. 
         [0011]    These objects are given only by way of illustrative example, and such objects may be exemplary of one or more embodiments of the invention. Other desirable objectives and advantages inherently achieved by the may occur or become apparent to those skilled in the art. The invention is defined by the appended claims. 
         [0012]    According to one aspect of the disclosure, there is provided a radiographic imaging detector that includes first and second covers seating against each other along a mating surface when the imaging detector is assembled. A detector panel is disposed between the covers and a hydrophobic coating applied to at least the mating surface. 
         [0013]    According to another aspect of the disclosure, there is provided a digital radiographic detector having a plurality of photoimaging pixels disposed in an array. Control electronics control operation of the array to capture radiographic images. A voltage source powers the array of photoimaging pixels and the control electronics. A housing encloses at least the array and the control electronics. The housing may provide seating for the voltage source. A first part of the housing comprises a first mating surface and a second part of the housing comprises a second mating surface. The mating surfaces are disposed adjacent to each other and define a gap therebetween wherein a hydrophobic material is deposited along at least one of the mating surfaces. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of the embodiments of the invention, as illustrated in the accompanying drawings. 
           [0015]    The elements of the drawings are not necessarily to scale relative to each other. 
           [0016]      FIG. 1  is an exploded view that shows some of the components of a digital radiography (DR) detector. 
           [0017]      FIG. 2  is an exploded view that shows an alternate embodiment for DR detector packaging. 
           [0018]      FIG. 3  is a side view that shows a conventional scheme for gasketing along mating surfaces and sealing of fasteners. 
           [0019]      FIGS. 4A ,  4 B,  4 C, and  4 D show the droplet-surface interface having various contact angles. 
           [0020]      FIG. 5A  is an enlarged side view that shows a portion of mating surfaces and a fastener having a hydrophobic surface treatment. 
           [0021]      FIG. 5B  is an enlarged side view that shows a portion of mating surfaces and a fastener, with a hydrophobic surface treatment applied to one of the mating surfaces. 
           [0022]      FIG. 5C  is an enlarged side view that shows a portion of mating surfaces and a fastener, with a layer of hydrophobic material sandwiched between mating surfaces. 
           [0023]      FIG. 6A  is an exploded view that shows some of the components of a DR detector according to an embodiment of the present disclosure. 
           [0024]      FIG. 6B  shows a number of surfaces and interfaces of the DR detector that have hydrophobic treatment. 
           [0025]      FIG. 6C  shows the assembled DR detector of  FIGS. 6A and 6B . 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0026]    The following is a description of exemplary embodiments, reference being made to the drawings in which the same reference numerals identify the same elements of structure in each of the several figures. 
         [0027]    Where they are used in the present disclosure, the terms “first”, “second”, and so on, do not necessarily denote any ordinal, sequential, or priority relation, but are simply used to more clearly distinguish one element or set of elements from another, unless specified otherwise. 
         [0028]    The exploded view of  FIG. 1  shows, in simplified form, some of the electrically active internal components of a DR detector  10  that are protected within an enclosure or housing  14  formed using multiple parts, including top and bottom covers  16  and  18 . A detector array  20  includes a scintillator and imaging pixels for capturing image signals from received radiation. A circuit board  22  provides supporting control electronics components for image data acquisition and wireless transmission to an external host system. A battery  24  provides power, acting as the voltage source for detector  10  operations. A port  26  extending through bottom cover  18  is provided to allow electrical connection for receiving and transmitting data, and/or receiving power such as from a voltage supply. The port may have an optional sealing cap  28 , which may be a rubber seal or other liquid-proofing material. In addition to the illustrated components, a number of interconnecting cables, supporting fasteners, cushioning materials, connectors, and other elements may be used for packaging and protecting the DR detector circuitry. An optional antenna and transmitter for wireless communication may alternately be provided within or as part of the housing  14 . Top and bottom housing covers  16  and  18  may be fastened together along a mating surface  48 . 
         [0029]    The exploded view of  FIG. 2  shows an alternate embodiment of DR detector  10 , in which detector array  20 , circuit board  22 , and battery  24 , along with interconnection and other support components, slide into an encased cavity in an enclosure or housing  30  through an open end thereof. A lid  32  may be fastened to cover  30  to provide a protective seal. 
         [0030]    Moisture and other liquid ingress is a concern for either of the  FIG. 1  or  FIG. 2  embodiments. Typically, as shown in the partial side view of  FIG. 3 , a gasket or O-ring  12  is provided to fit within a groove along mating surface  48  between covers  16  and  18  of the enclosure or housing  14  of DR detector  10  as shown in  FIG. 1  or, with the alternate embodiment of  FIG. 2 , along the mating surface where lid  32  joins cover  30 . Fasteners  34 , such as a screw for securing top  16  and bottom  18  covers, require secure mating connections to keep out moisture and other liquids. In order to properly seat O-rings or gaskets, mating surfaces  48  of covers  16  and  18  must be machined to a fine finish, with very low tolerances. It can be appreciated that, over time, some degradation of gaskets and seals is likely to occur, such as with standard handling of the detector, after disassembly for battery replacement or for firmware upgrade, or for other maintenance function, and with repeated connection and disconnection at port  26 . 
         [0031]    Embodiments of the present invention address the need for improved moisture protection of the DR detector using hydrophobic treatment of various surfaces and interfaces of the DR detector device enclosure. Hydrophobic surfaces provide an interface that is highly repellent to bodily fluids and water. On a hydrophobic surface, water and water-based liquids tend to bead rather than to spread across such a surface because the liquids are repelled by the surface. The hydrophobic surface is thus often described as having low “wettability”. 
         [0032]    Hydrophobic behavior is quantified in terms of a contact angle θc at the liquid/surface interface, based on a formula known as Young&#39;s equation.  FIGS. 4A ,  4 B,  4 C, and  4 D illustrate, for a droplet  40  on a surface  42 , how contact angle θc is measured for an increasing hydrophobic property of the surface  42 , from the relatively low contact angle θc of  FIG. 4A  that is typical of most untreated surfaces along which water spreads freely, to the highly hydrophobic surfaces shown in  FIGS. 4C and 4D , where the interface energy that relates to reduced wettability causes water to bead. By definition, hydrophobic behavior begins when the contact angle θc of water is about 90 degrees, as shown in  FIG. 4B . As a familiar point of reference, poly(tetrafluorethene) (PTFE, commercially provided as Teflon (R) material, a registered trademark of E. I. du Pont de Nemours and Company) has a water contact angle near 110 degrees. As the contact angle θc increases toward 120 degrees, as shown in  FIG. 4C , the wettability of the surface decreases due to its greater hydrophobic property. When hydrophobicity provides extreme contact angles θc (such as that of a bird feather) in the superhydrophobic 150 degree contact angle example of  FIG. 4D , the surface is considered to be highly resistant to the spread of moisture thereover. 
         [0033]    Embodiments of the present invention use a hydrophobic coating or other treatment on selected surfaces of, and interfaces of, the DR detector  10  in order to prevent or significantly limit liquid ingress along mating surfaces, such as where top and bottom covers  16 ,  18  are adjacent or where they may partially abut or contact each other in some regions of the mating surfaces, and along connector interfaces. Where a hydrophobic treatment or a coating is used on one or both surfaces that define a gap in the housing that is defined between two covers or other components, the resulting hydrophobic property can be sufficient to keep water or other liquid from entering the DR detector through the gap. This can help to obviate the requirement for an additional gasket or sealant material to seal the gap. The need for precision adjustment and fitting of mating surfaces, mounting screws, and other hardware can also be significantly reduced. 
         [0034]    Referring to  FIG. 5A , mating covers  16  and  18  of the enclosure are treated with a hydrophobic coating  50  along one or more mating surfaces  48 . In addition, screw holes and other features for accepting fasteners  34  are also conditioned with a suitable treatment such as coating  50 . Optionally, fasteners  34  themselves may have an applied coating. With hydrophobic coatings that provide a contact angle in excess of about 100 degrees, a small airspace distance d in gap  52  may be tolerated between treated mating surfaces while still preventing ingress of liquids and moisture therethrough. A treated gap  52  with distance d smaller than about 0.010 to about 0.020 inches, or preferably smaller than about 0.005 in., for example, can be sufficient to prevent liquid flow between two treated surfaces or along the surfaces of screws or other fasteners that are fitted into orifices of the covers  16 ,  18 . Components such as sealing cap  28  ( FIG. 1 ) can be at least partially coated with a hydrophobic coating to obviate the need for seals or gasketing around electrical or data connectors. 
         [0035]    Other alternative arrangements for hydrophobic treatment of gap  52  are shown in  FIGS. 5B and 5C .  FIG. 5B  is an enlarged side view that shows a portion of mating surfaces and a fastener, with a hydrophobic surface treatment applied to one of the mating surfaces. The mating surface  48  of cover  16  has an applied hydrophobic coating; cover  18  is not treated in the  FIG. 5B  example. Using fastener  34 , which may include a machine screw, for example, gap  52  can be kept small enough that fluid ingress through gap  52  is prevented. 
         [0036]    A pre-formed hydrophobic film, gasket, or other hydrophobic material can alternately be pressed within the gap between cover portions.  FIG. 5C  is an enlarged side view that shows a portion of mating surfaces and a fastener, with a layer  60  of hydrophobic material sandwiched between mating surfaces. Layer  60  can be applied in partially cured form or have an adhesive backing or may be conditioned and inserted to adhere to either or both mating surfaces  48 , effectively forming a coated surface under compressive force exerted by tightening fastener  34 . 
         [0037]    One advantage of hydrophobic coatings for waterproofing gaps relates to air flow, such as for cooling or venting. Using conventional gasket and sealing techniques, both air/gas and liquid flow across the interface are constrained. However, using conventional machining practices and following close tolerances, a selected coating thickness, positioned within air passages or passages or vents for other gases can be liquid-proofed and yet allow air passage without requiring air-tight sealing. Thus, for example, the use of hydrophobic coatings can allow venting of the DR detector battery  24  ( FIGS. 1 and 2 ) using small sized orifices for air passage, while keeping out liquid and/or moisture at the same time. 
         [0038]    In one embodiment, hydrophobic coated surfaces (e.g., mating surfaces) can provide air passages or conduits (e.g., internal, or internal extending to an exterior surface) for the DR detector  10  that can block liquid (e.g., liquid-proof) yet allow gases to pass therethrough (e.g., not air-tight). 
         [0039]    A number of hydrophobic coating materials use nanoparticles, which, by definition, are generally between 1 and 100 nm in diameter, in various arrangements. Some of the nanoparticle-based hydrophobic coatings can exhibit contact angles in a range of 120 degrees or more. Superhydrophobic materials can have contact angles of 150 degrees or more. A contact angle in excess of 150 degrees provides a hydrophobic treatment that is particularly advantageous for the DR detector. A contact angle in excess of 120 degrees can also provide good performance. A contact angle in excess of about 100 degrees provides a measure of protection but may constrain allowable tolerances related to gap distance of the housing. The choice of a particular material to be applied as a hydrophobic treatment depends on factors such as a selected design tolerance between mating surfaces. A number of types of hydrophobic materials are applied under high energy conditions, such as using plasma-assisted deposition under vacuum for various carbon-based materials, such as materials formed from carbon nanotubes, for example. Coatings can be applied to covers  16  and  18  or to individual components of housing  14  separately, to selected portions or surfaces thereof, or to the assembled DR detector  10  in order to render the assembled DR detector  10  hydrophobic. 
         [0040]    Hydrophobic materials that can be used as coatings include polysiloxanes and other organosilicon polymers, poly(tetrafluorethene) (PTFE) or polypropylene (PP); coatings formed from reactive inorganic nanoparticles; compositions that comprise a plurality of nano-fillers dispersed within a fluoroelastomer matrix; compositions with a nano-filler having a core-shell structure with a silica shell over a metal oxide core; multilayered film coatings such as the polyelectrolyte layers described in US Patent Application Publication No. 2006/0029808 A1 entitled “Superhydrophobic coatings” by Zhai et al., which is incorporated by reference herein in its entirety; sol-gel foam coatings, and sol-gel alumina coatings. 
         [0041]    Nano-fillers used within the hydrophobic material can have any of a variety of structures, including nanospheres, nanotubes, nanofibers, nanoshafts, nanopillars, nanowires, nanorods, nanoneedles, and nanowhiskers, for example. Coatings formed using nanoparticles appear to be particularly promising, since a number of coatings of this type provide treated hydrophobic surfaces with high water repellent contact angles, with some materials exceeding 120 degrees. 
         [0042]    A variety of deposition techniques can be used to provide exemplary embodiments of hydrophobic coatings on components and/or surfaces of the DR detector  10 . Coating methods can include spin-coating, dip-coating, brush or roller application, gap coating, extrusion coating, aerosol spraying, ink jet printing, and doctor blade-casting, in which the coating solution is deposited on a substrate and a straight edge then used to spread the solution. For a number of coating types, the coating or a precursor is applied using a vacuum chamber. Application steps for many of these coating techniques can include baking, sintering, and other methods for curing or otherwise conditioning the applied coating. Application may require one or more base coatings including an adhesion promoting resin to pre-condition the surface, followed by one or more applications of the hydrophobic material itself. Various curing agents can be incorporated in the nanoparticle formulation, including monomer and fluoroelastomer materials, for example. The surface of interest may also be plasma treated, which may help to remove organic contamination and increase surface reactivity. Plasma treatment can include air plasma, oxygen plasma, or carbon dioxide plasma, for example. 
         [0043]    Advantageously, the use of nanotechnology and coatings with substantial nanoparticulate content can reduce the weight of the DR detector and can help to eliminate at least a portion of seals, gaskets, and other preventive devices and treatments that have previously been used for protection of DR detectors from liquids. These coatings can withstand heat, cleaning, and abrasion, and allow disassembly of the DR detector, such as for battery replacement, upgrade, or repair, for example. In one embodiment, hydrophobic coatings can be re-applied to selected surfaces of the housing or to the detector or detector components. For example, hydrophobic coatings can be repeatedly or periodically applied to help renew water repellent behavior, such as when the detector is disassembled for service or battery replacement. 
         [0044]    While coatings that are hydrophobic can be particularly useful with DR detectors, these coatings can also be-used for properly designed film or computed radiography (CR) cassettes that use a removable medium that is developed, scanned, or otherwise processed to obtain image data following exposure. 
         [0045]    The applied hydrophobic material can include any of a number of solvents to help disperse the nanoparticles or other components along the surface to be treated. Solvents can include water or organic solvents, such as methyl isobutyl keytone, acetone, methyl ethyl ketone, and other solvent materials. 
         [0046]    The DR detector covers  16  and  18  ( FIG. 1 ) may be metal, such as aluminum, magnesium or their alloys, or some other metal or metal alloy; alternatively, one or both covers  16  and  18  can be a composite material, such as a plastic or carbon fiber material. The area of concern for moisture ingress into the housing is at the interface between the covers  16  and  18 , where gap  52  has been described herein; the covers  16 ,  18  themselves are impervious to moisture and may not require hydrophobic treatment except near the gap  52 . By hydrophobic treatment of areas adjacent to gap  52 , embodiments of the present disclosure reduce or eliminate the need for gaskets, o-rings, seals, and sealants as features for keeping moisture from seeping into the DR detector. Hydrophobic treatment can also allow relaxed mechanical tolerances for covers, particularly with respect to mating surfaces. This, in turn, reduces or eliminates machining costs and may allow the use of cast or molded plastic or composite materials for covers, instead of requiring more costly metal materials. 
         [0047]    According to an exemplary embodiment of the present disclosure, as shown in the partial exploded view of  FIG. 6A , a DR detector  10  may have a number of parts, including covers  16  and  18 , for protecting the photoimaging detector array  20  and control electronics of circuit board  22 . Battery  24  may be removably mounted against the outside of cover  18 . Battery  24  may be seated against one of covers  16  and  18  and may be held in place by a clamp or other suitable fastener (not shown). 
         [0048]      FIG. 6B  shows a number of surfaces and interfaces of the DR detector of  FIG. 6A  that have hydrophobic treatment. The treated surfaces are highlighted in  FIG. 6B , using expanded lines. Treated areas can include: mating surfaces  48  of covers  16  and  18 ; exposed portions of port  26  and along the periphery of this connection port; along a connector interface  62  for battery  24 ; and within and along vent orifices  64  that are located along one or more edges of battery  24 . One or more optional vent orifices  66  can also be provided in detector housing  14 . 
         [0049]    In an exemplary embodiment of the present disclosure, the hydrophobic treatment that is used is applied in a multi-stage process, using dipping where practicable, in order to achieve full coverage of the highlighted areas. First, a base coat is applied in one or more applications. Dry time between base coat applications at room temperature is on the order of about 15 minutes. 
         [0050]    The base coat provides a suitable adhesive that conditions the treated area for better adhesion of the top coat. The top coating layer, applied to surfaces treated with the base coat, can be added in one or more applications. 
         [0051]    The top coating layer includes a nanoparticle-based hydrophobic material that is capable of providing superhydrophobic performance, with contact angles of up to 165 degrees. With contact angles in this range, vent openings of small enough diameter, such as less than about 0.020 in. diameter, are able to allow cooling air flow or allow exhaust gas passage, while at the same time fluid ingress through the same orifices is blocked. Advantageously, the hydrophobic treatment can be applied at the parts fabrication stage, such as just after covers  16  and  18  are machined or molded and before they are used to form housing  14 , rather than following later stages of DR detector assembly. 
         [0052]      FIG. 6C  shows the assembled DR detector of  FIGS. 6A and 6B , with battery  24  fitted into position against the housing  14 . It can be appreciated that the fluid protection approach that is used in embodiments of the present disclosure has advantages over conventional gasketing and sealing techniques. The treated areas are along interfaces that offer some measure of protection against abrasion and damage, rather than extending across broad areas where a coating or other hydrophobic treatment could easily be scratched or worn away. Venting areas are unobstructed to gases but block water and other fluids. Disassembly and re-assembly can be performed without requiring renewal of the hydrophobic treatment. If necessary to remove and renew the treatment, mild solvents such as mineral spirits or xylene can be used, with light abrasion, to restore the original surface of the housing components preparatory to re-application. Advantageously, the base coating and hydrophobic top coating can be reapplied to mating and connector surfaces without requiring separate high-energy application or vacuum equipment. 
         [0053]    As noted previously, there are a number of different materials that can be used for providing hydrophobic behavior along mating surfaces between parts of the DR detector housing and along electrical contacts, signal ports, and ventilation orifices. There are, similarly, a number of different application technologies and methods that can be used for depositing hydrophobic materials at suitable locations along mating surfaces and interfaces for providing increased protection from moisture ingress. 
         [0054]    Electrical contacts for data signals or power signal connection can also be provided with hydrophobic treatment, along and adjacent to the point of contact. Hydrophobic treatment can be used with various types of pin connectors, including connections that employ spring-loaded pins that require only a minimal contact area between conductors. 
         [0055]    Embodiments of the application provide a radiographic imaging detector including: a first cover; a second cover that seats against the first cover along a mating surface when the imaging detector is assembled; a detector panel that lies between the first and second cover; and a hydrophobic coating applied to at least one mating surface. The radiographic imaging detector may further comprise an input/output port that is accessible within at least one of the first and second covers; a removable cover plate that seals against the input/output port, wherein at least one of the cover plate or an edge of the input/output port further have the applied hydrophobic coating. The radiographic imaging detector may further comprise one or more fasteners that have an applied hydrophobic coating. The applied hydrophobic coating can be formed from carbon-based nanoparticles and can also be applied to one or more fasteners of the imaging detector. The coating can be applied to both the first and a second mating surface that seats against the first mating surface. The detector panel may alternately house a computed radiography or a film medium. The hydrophobic coated mating surface of the digital radiographic detector  10  is liquid-proof and not air-tight between the first cover and the second cover. 
         [0056]    Embodiments of the present invention provide a method for fabricating a digital radiography detector, the method comprising conditioning mating surfaces of first and second housing covers by applying one or more coating materials under vacuum; and fastening the first and second housing covers wherein a gap between the first and second housing covers is greater than about 0.005 and less than about 0.020 inches when the digital radiography detector is assembled. The one or more coating materials may comprise carbon nanotubes. 
         [0057]    The invention has been described in detail, and may have been described with particular reference to a suitable or presently preferred embodiment, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. In addition, while a feature(s) of the invention can have been disclosed with respect to only one of several implementations/embodiments, such feature can be combined with one or more other features of other implementations/embodiments as can be desired and/or advantageous for any given or identifiable function. The term “at least one of” is used to mean one or more of the listed items can be selected. The term “about” indicates that the value listed can be somewhat altered, as long as the alteration does not result in nonconformance of the process or structure to the illustrated embodiment. Finally, “exemplary” indicates the description is used as an example, rather than implying that it is an ideal. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims, and all changes that come within the meaning and range of equivalents thereof are intended to be embraced therein.

Technology Category: 3