Abstract:
A method for coating a device, such as an industrially or medically applicable device, with a polymer layer is provided. The method includes contacting the device with a grafting initiator comprising at least one photoinitiator group, exposing the device to radiation, contacting the device with a polymerizable monomer, and again exposing the device to radiation.

Description:
REFERENCE TO CO-PENDING APPLICATIONS 
     This application is a divisional application of U.S. patent application Ser. No. 10/371,043, entitled GRAFTING APPARATUS AND METHOD OF USING, filed Feb. 19, 2003, now U.S. Pat. No. 7,041,174, issued May 9, 2006, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This invention relates to coating a surface of a device. In particular, this invention relates to an apparatus, and methods of using such for coating a device, such as an industrially or medically applicable device. 
     BACKGROUND ART 
     Many devices, including medical devices, are becoming increasingly complex in terms of function and geometry. These devices frequently require a coating to provide a desired function or feature, such as providing the device with particular chemical or physical characteristics. However, traditional coating methods, such as dip coating, are often undesirable for coating complex geometries since the coating solution may get entrapped in the device structure. This entrapped solution can cause webbing or bridging of the coating and can hinder the function of the device. Other methods, such as spray coating, have also been used to apply coatings to these devices. However, current methods of spray coating often introduce operator error, and can also result in reduced coating consistency. In addition, traditional coating methods generally use costly reagents inefficiently and therefore are expensive for the user. 
     Improved coating methods and the apparatus to implement these methods are needed in this area. 
     SUMMARY 
     The present invention provides an apparatus and methods for coating an object. In some implementations the apparatus comprises a plurality of containers, a gas supply source, an irradiation station, and a conveyor mechanism. In another implementation, the present invention provides a process for coating an object comprising, for example, the steps of placing the object into a container, filling the container with a first solution of nonpolymeric grafting initiator, irradiating the container, removing the solution from the container, filling the container with a second solution of polymerizable monomer or macromer, bubbling gas through the solution, irradiating the container, and removing the object from the container. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1-6  serve to illustrate aspects of the invention that can be included in some implementations. However,  FIGS. 1-6  are only provided by way of example and thus do not serve to limit the scope of the present invention. 
         FIG. 1  is an illustration of a coating apparatus made in accordance with an implementation of the current invention. 
         FIG. 2  is an illustration of the gas supply source of the coating apparatus of  FIG. 1 . 
         FIG. 3  is an illustration of the container of the coating apparatus of  FIG. 1 . 
         FIG. 4  is an illustration of the irradiation station of the coating apparatus of  FIG. 1 . 
         FIG. 5  is an illustration of a solution maintenance station of the coating apparatus of  FIG. 1 . 
         FIG. 6  is an illustration of an alternative solution maintenance station of the coating apparatus of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In an embodiment, the invention provides an apparatus for coating a device with a photoactivatable compound and a polymerizable compound. “Photoactivatable compounds” includes compounds having two or more photoactivatable groups, the groups being same or different. The photoactivatable compound can also be referred to as a “grafting initiator”. The coating apparatus can be automated, semi-automated, or manually operated, and can provide a safe and efficient approach to coating devices using solutions having a photoactivatable compound and a polymerizable compound. 
     The coating apparatus of the current invention, in some embodiments, can reduce the exposure of the operator to potentially hazardous agents, which include electromagnetic radiation, such as ultraviolet radiation, or toxic compounds, such as neurotoxic polymerizable monomers. 
     The coating apparatus can, in some embodiments, provide a cost-effective approach to coating devices by including features that reduce the waste of compounds or solutions used as coating reagents. Such features may include, for example, optimized container size and solution recycling mechanisms. 
     In an embodiment, the invention is directed to methods for coating devices with a photoactivatable compound and a polymerizable compound. In this method, a device to be coated is placed in a container. The container may contain or can be filled with a solution having a photoactivatable compound having at least two photoactivatable groups. The container having the device and solution is brought into the proximity of a radiation source that provides electromagnetic radiation to the photoactivatable compound in the container. The electromagnetic radiation activates at least one photoactivatable group of the photoactivatable compound, allowing the photoactivated compound to couple to the surface of the device. “Electromagnetic radiation” includes any sort of energy propagated in the form of electromagnetic waves, including ultraviolet light, which may activate the photogroups of a photoactivatable compound. 
     Following binding of the photoactivatable compound to the device, one or more photoactivatable groups remain pendent from the photoactivatable compound and are able to be subsequently activated by irradiation. Following binding of the photoactivatable compound to the surface of the device, a polymerizable compound is added to the container. In addition, an inert gas is supplied to the container purging air from a solution having the polymerizable compound. The solution having the polymerizable compound is then brought into the proximity of a radiation source. The radiation source provides electromagnetic radiation to the surface of the device and activates at least one pendent photoactivatable group of the bound photoactivatable compound. The term “pendent” or “latent” refers to photoactivatable groups that can be activated to form covalent bonds, for example, with the surface of the device or to provide a radical to initiate polymerization of the polymerizable compound. Activation of the pendent photoactivatable group initiates polymerization of the polymerizable compound in the presence of the bound photoactivatable agent, thereby forming a polymer coating on the surface of the device. 
     To further illustrate features that can be included in embodiments of the present invention, the coating apparatus, followed by select individual components, will now be described in greater detail. 
     A. Coating Apparatus 
     The apparatus for coating an object often includes a plurality of containers, a gas supply source in communication with the plurality of containers, at least one irradiation station for irradiation of the containers, and a conveyor mechanism to direct the containers to and from the irradiation station. 
     One embodiment of the invention is shown in  FIG. 1  and it will be appreciated that other embodiments are also within the scope of the invention. In an embodiment, as illustrated in  FIG. 1 , the coating apparatus  10  includes a housing  12  on which a plurality of containers  14  are coupled to a conveyor track  16 . The containers  14  can travel along the path of the conveyor track  16  to be delivered to any particular area on the top of the coating apparatus  10 . The conveyor track  16  can allow the containers  14  to travel in either a clockwise or counter clockwise direction. The conveyor mechanism  17  can be driven by a conveyor motor  28  through a conveyor drive shaft  30  or other suitable motor mechanisms. Operation of the conveyor mechanism  17  can be controlled by a computerized control unit  46  or can be controlled manually. 
     In some embodiments, the coating apparatus can also include sensors for sensing the position of an object, for example, the position of the container, on the coating apparatus. Referring again to  FIG. 1 , the housing  12  can also include one or more conveyor sensors  15 , which can detect the position of a container  14  along the conveyor track  16 . Now referring to  FIG. 3 , which shows an embodiment of the container  14  and portion of the conveyor track  16  in greater detail, the container platform  31  also has a conveyor sensor trip  33  which can come into proximity of and actuate the conveyor sensor  15 . Actuation of the conveyor sensor  15  may be through mechanical or other means. Actuation of the conveyor sensor  15  can send a message to the computerized control unit  46  (not shown) to modulate movement of the conveyor track  16 . 
     According to the invention, the coating apparatus also includes a gas supply source that functions to supply the plurality of containers with an inert gas (i.e., the gas supply source is in gaseous communication with the containers). In one embodiment, the gas supply source functions to provide one or more containers with a source of gas while the containers are attached to the conveyor track and also when the containers are being moved by the conveyor track. The gas supply source can include a rotatable member that communicates gas to the containers while the containers are traveling on the conveyor mechanism. 
     Referring to  FIG. 2 , showing an example embodiment, the gas supply source  18  can include gas tank  20 , a gas pressure regulator  22 , and a plurality of gas supply lines  24 , each gas supply line  24  in gaseous communication with the container  14  (not shown). The gas supply lines can be any suitable device that can transport gas, including hoses, pipes, tubes, conduits, or ducts made from any suitable material such as rubbers, plastics, metals, or combinations thereof. The gas supply source  18  can include a rotating gas supply member  26  which allows the gas supply lines  24  to travel concurrently with the movement of the containers  14  as they are moved by the conveyor track  16 , typically in a clockwise or counterclockwise direction. The rotating gas supply member  26  allows the gas supply lines  24  to travel concurrently with the movement of the containers  14 . Typically, the gas tank  20  is stationary and does not rotate. However, in other embodiments portions of the gas supply source  18  can be rotatable and allow gas supply lines  24  to travel concurrently with the movement of the containers  14 . The gas supply source  18  can provide an inert gas such as nitrogen, helium, or the like, to the container  14 . 
     According to the invention, the coating apparatus also includes one or more irradiation stations. The irradiation stations generally function to provide electromagnetic energy to the containers having objects to be coated. The electromagnetic energy can activate the photoactivatable groups of the photoactivatable compound, the photoactivatable compound typically being in a solution in the container and surrounding the object to be coated. 
     The irradiation stations can be positioned at any place on the coating apparatus proximal to where the container is positioned. The irradiation stations can be placed inside or outside the conveyor track, and in some embodiments, and depending on the aspects of the housing of the coating apparatus, above or below the conveyor track. 
     In one embodiment, and as shown in  FIG. 4 , the irradiation station  32  can include a radiation emitter  40 , radiation emitter line  42 , and radiation power supply  44 . The radiation emitter  40  can be any suitable light source that emits electromagnetic energy in a wavelength sufficient to activate the photoactivatable compound used for the process of coating the device. Preferable light sources emit ultraviolet light at a wavelength that activates the photoactivatable groups of the photoactivatable compound. The wavelength range can be from 260-400 nm. Irradiation station  32  can also include one or more bandwidth or polarizing filters functioning to deliver a particular type of light to the container  14 . 
     In a one embodiment, radiation emitter  40  is the end of an optical fiber and the radiation emitter line  42  is an optical fiber able to transmit light from the radiation power supply  44  to the radiation emitter  40 . In another embodiment, the radiation emitter  40  is an ultraviolet light-emitting bulb and the radiation emitter line  42  is a wire that transmits electric current from the radiation power supply  44  to the radiation emitter  40 . The irradiation station  32  can include one or more radiation emitters  40  and associated emitter lines  42 . 
     The irradiation station  32  can provide light to the device in any desired manner. For example, the device can be irradiated for a defined period of time and at a desired light intensity. Function of the irradiation station  32  can also be coordinated with the movement of the containers  14  as they are moved by the conveyor mechanism  17 . For example, the radiation emitter  40  can be activated to provide ultraviolet light to the device when the container  14  is in proximity to the irradiation station  32 . Operation of the irradiation station  32  can be controlled by a computerized control unit  46  (shown in  FIG. 1 ) or can be controlled manually. 
     B. Container 
     Container  14  is typically attached to conveyor track  16  which can include a belt, rail, wire, or chain feature to drive the movement of the container  14 . In one embodiment, as illustrated in  FIG. 3 , container  14  can be mounted on top of a container platform  31  that is attached to conveyor track  16 . The container platform can include a conveyor sensor trip  33  which can trigger the conveyor sensor  15  (shown in  FIG. 1 ) to stop movement of the conveyor track  16 . The conveyor sensor  15  can be positioned at any position on the housing  12  (shown in  FIG. 1 ) in the path of the conveyor sensor trip  33  to stop movement of the conveyor track  16 . 
     In some embodiments, the container of the coating apparatus can also include valves or switches that function to regulate the flow of gas from the gas supply source to the container. In other embodiments the container includes valves or switches that function to regulate the flow of liquids, for example, solutions used in the coating process. In some embodiments the valves and switches are useful for regulating the flow of both liquids and solutions to and from the container. 
     Some of these embodiments are illustrated in reference to  FIG. 3 , which shows that container  14  is attached to a container valve  34  having valve switch  36  which can be operated to regulate the flow of gas or liquids to and from container  14 . Container valve  34  includes at least one container gas supply port  38  which is attached to gas supply line  24 . In another embodiment, container valve  34  can also include at least one container liquid supply port  39 . The liquid supply port  39  can be attached to a hose or a tube that can direct solution to or away from the container  14 . 
     In one embodiment, the valve switch  36  can be adjusted to allow the container  14  to be open or closed to gas flow from the gas supply source  18 . Gas can be supplied from the bottom of the container  14 . In another embodiment, valve switch  36  can be adjusted so that the container is closed to both gas and liquid flow, open to only gas flow, open to only liquid flow, or open to both gas and liquid flow. Operation of the valve switch  36  can be controlled by a computerized control unit  46  (shown in  FIG. 1 ) or can be controlled manually. For example, valve switch  36  can be actuated automatically when the container  14  reaches a certain position traveling along the conveyor mechanism  17 . Automated actuation can regulate the flow of gas and solution to and from the container  14  at any point during the operation of the coating apparatus  10 . 
     Container  14  can be composed of any suitable material that transmits light, for example, ultraviolet radiation, from the radiation emitter  40  to the device in the container  14 . Suitable materials include glass, Pyrex™ materials, and the like. Generally, the container  14  is made of compounds that do not have abstractable hydrogen ions or from compounds that contain a low percentage of compounds with abstractable hydrogen ions. In one embodiment, the container  14  can be, or can be a derivative of, a glass syringe commercially available from, for example, Popper and Sons, Inc. (Lincoln, R.I. 02865-4615) or Becton Dickinson (Franklin Lakes, N.J. 07417). An advantageous feature of the current invention is that glass syringes are commercially available in a variety of sizes and are easily removable from the container valve  34 . This offers the user a cost effective way of changing the container size to accommodate the device to be coated. Appropriate container size also reduces the amount of solution containing either the photoactivatable compound or polymerizable compound used to surround the device during the coating process. 
     In another embodiment, the container  14  can also include a container lid  48 . The container lid  48  can include a lid valve  50  which can be adjusted to allow the escape of gas from the inside of the container  14  when the internal pressure reaches a predetermined level. The container lid  48  can be attached to the container  14  by, for example, a hinge, to allow easy access to the container  14 . 
     C. Irradiation Station 
     As previously indicated, one or more irradiation stations can be positioned at any place on the coating apparatus proximal to where the container is positioned. In one embodiment, the irradiation station includes a shielding member and the shielding member functions to protect the user from radiation or increase the reflected radiation within the shielding member, or both. In another embodiment the shielding member is movable. Generally the shielding member can be moved on the irradiation station to encompass at least a portion of the container  14 . 
     Also, one or more portions of the irradiation station can function to emit electromagnetic radiation. In one embodiment, the radiation emitter portion of the irradiation station is attached to and movable with the radiation shield. In another embodiment, the radiation emitter portion of the irradiation station is not attached to the radiation shield. Generally, the radiation emitter can be positioned at any place on the irradiation station sufficient to provide a desired dose of electromagnetic energy to the container  14 . 
     Referring to the embodiment shown in  FIG. 4 , the irradiation station  32  includes a movable radiation shield  52  that is connected to one or more shield lifting posts  54  and a lift housing  56 . A cross section of the radiation shield  52  is illustrated encompassing a container  14 . The radiation shield  52  can be cylindrical shaped, for example, wherein the bottom portion of the radiation shield  52  is open to allow placement of the container  14  within. Other shapes of the radiation shield are also contemplated; these include cup and half cup-shaped shields that can be moved in a swinging or flipping movement on the irradiation station. The radiation shield  52  can also be connected to the radiation emitter  40  that is situated to direct light into and within the radiation shield  52 . One or more radiation emitters  40  can be connected to the radiation shield  52  at any desired location or angle. In some embodiments, optical fibers from the radiation emitter  40  can be distributed on the inside of the radiation shield  52 . The radiation emitter line  42  is of sufficient length to allow movement of the radiation shield up and down. 
     The radiation shield  52  can move vertically on the shield lifting post or posts  54 . The shield lifting post or posts  54  guide the movement of the radiation shield  52  up and down. The lift housing  56  typically includes a suitable device such as a motor or an air cylinder that drives the movement of the radiation shield  52 . In a down position, the radiation shield  52  encompasses the container  14  and light can be provided to the container  14 . In an up position, the container  14  is able to move away from the irradiation station  32  via the conveyor track  16 . 
     The radiation shield  52  can be fabricated from any suitable material. Suitable materials include those that do not transmit ultraviolet light including metals, such as aluminum or steel. An example of such a material is reflective aluminum. The interior of the radiation shield  52  can also be prepared, for example by coating or polishing, to provide an interior that is highly reflective to ultraviolet radiation. A highly reflective interior can be useful to achieve a high degree of uniform coating of the photoactivatable compound and polymerizable compound, and can also reduce the duration and intensity of the light emission during the step of irradiating the device. The radiation shield  52  also provides an increased level of safety to the user by minimizing or eliminating the amount of radiation exposed to the user during the step of irradiating. 
     Operation of the irradiation station  32  can be automated or can be controlled manually and can be coordinated with the operation of the conveyor track  16 . For example, the conveyor track  16  can bring the container  14  into the proximity of the irradiation station  32  via the conveyor track  16  when the radiation shield  52  is in the up position. When the container  14  is properly situated under the radiation shield  52 , the motor or air cylinder of the lift housing  56  can be actuated to lower the radiation shield  52  down the shield lifting post or posts  54  surrounding the container  14 . 
     The irradiation station  32  can include an upper sensor  55  and a lower sensor  57  to determine the location of the radiation shield  52  in the up and down positions, respectively. For example, proximity sensors can be used for the upper sensor  55  and a lower sensor  57 . Prior to the container  14  being positioned proximal to the irradiation station  32 , the radiation shield  52  is typically in the up position. When the container  14  becomes properly positioned (i.e., when the conveyor sensor is triggered by the conveyor trip and the movement of the conveyor track is stopped), the radiation shield  52  is lowered to a point where the lower sensor  57  is triggered. Upon triggering of the lower sensor  57 , the irradiation power supply  44  can be actuated to provide light or energy to the container  14  within the radiation shield  52 . After an amount of light is delivered to the container  14 , the radiation shield  52  can be raised to a level on the irradiation station  32  where the upper sensor  55  is activated and the container  14  is free to pass below the radiation shield  52 . 
     D. Solution Maintenance Station 
     In one embodiment of the invention, the coating apparatus can also include a solution maintenance station to provide a solution to, or remove a solution from, one or more containers. The solution maintenance station can generally function to provide or remove one or more solutions involved in the coating process. The solution maintenance station can be positioned at any place on the coating apparatus proximal to where the container is positioned. The solution maintenance station generally functions to establish a fluid connection between the container and one or more reservoirs that contain solutions involved in the coating process. 
     In one embodiment the solution maintenance station establishes a fluid connection between a portion of the container that includes valves or switches that can regulate the flow of liquid or gas in and out of the container. For example, a portion of the solution maintenance station can establish a fluid connection with the container that allows solution to be provided, removed, or both, from the lower portion (i.e., bottom) of the container. In another embodiment the solution maintenance station can provide solution to the top of the container. 
     Some of these embodiments are illustrated in reference to  FIG. 5 , which illustrates that solution maintenance station  60  includes a housing  62  having a pump  63  that is able to supply or withdraw solution from the container  14  through a series of lines. The movement of solution to and from the container  14  can be accomplished by attaching a container liquid supply line  66  to the container liquid supply port  39  via a container port adapter  68 , all of which are in fluid connection. A movable supply line insertion mechanism  70  can connect the container port adapter  68  to the container liquid supply port  39  when the container  14  is properly positioned next to the solution maintenance station  60 . Valve switch  36  of the container  14  can be actuated manually or automatically to allow the flow of solutions from the container  14  to the container liquid supply line  66  or from the container liquid supply line  66  to the container  14 . 
     The container liquid supply line  66  is in fluid connection with a solution maintenance station valve  64  that is in fluid connection with one or more reservoir lines. In one embodiment, as illustrated in  FIG. 5 , the solution maintenance station valve  64  is in fluid connection with a first reservoir line  74 , second reservoir line  76 , and third reservoir line  80 , which are in fluid connection with first reservoir  72 , second reservoir  78 , and third reservoir  82 , respectively. Solutions having the photoactivatable compound, the polymerizable compound, or a wash solution can be disposed in any of the reservoirs. Solution maintenance station valve  64  can be actuated, either manually or automatically, to direct liquid flow between the liquid supply line  66  and any of the first  74 , second  76 , or third reservoir line  80 . Optionally, solution maintenance station valve  64  can be actuated to a position for disposal of fluid withdrawn from the container  14 . 
     Operation of the solution maintenance station  60  can be automated or can be controlled manually and can be coordinated with the operation of the conveyor track  16  and the gas supply source  18  (not shown). For example, the conveyor track  16  can transport the container  14  into the proximity of the solution maintenance station  60  with the container port adapter  68  in a retracted position. When the container  14  is properly situated next to the solution maintenance station  60 , the supply line insertion mechanism  70  can move and insert the container port adapter  68  into the container liquid supply port  39 . The solution maintenance station  60  can include a sensor, for example, an optical sensor, to detect proper positioning of the container  14  in relation to the solution maintenance station  60 . 
     When the container port adapter  68  is properly fit into the container liquid supply port  39  and the valve switch  36  and solution maintenance station valve  64  are actuated to allow flow of solution in and out of the container, the pump  63  can be operated to withdraw fluid from any of the reservoirs and into the container  14 . The pump  63  can be operated to deliver an amount of liquid into the container  14  at a desired rate. If the container  14  is to be transported to another location on the coating apparatus  10  (shown in  FIG. 1 ), for example, the irradiation station  32 , the pump  63  can be stopped and the valve switch  36  and solution maintenance station valve  64  closed to prevent loss of fluid from the container. The movable supply line insertion mechanism  70  can disconnect and retract the container port adapter  68  from the container liquid supply port  39 . The container  14  can be moved away from the solution maintenance station  60  via the conveyor track  16 . 
     Removal of fluids from the container  14  can be achieved by operating the pump  63  in a reverse mode to either draw the liquids back into a reservoir for recycling of the solution, or to a disposal outlet. 
     In another embodiment, illustrated in  FIG. 6 , the solution maintenance station  60  is depicted in a top-dispensing configuration. When the valve switch  36  of the container  14  is closed to solution flow, pump  63  can allow the withdrawal of fluid from any reservoir, through the solution maintenance station valve  64  and container liquid supply line  66  and into the container  14 . The solution maintenance station valve  64  is in fluid connection with a first reservoir line  74 , second reservoir line  76 , and third reservoir line  80 , which are in fluid connection with first reservoir  72 , second reservoir  78 , and third reservoir  82 , respectively. Solutions having the photoactivatable compound, the polymerizable compound, or a wash solution can be disposed in any of the reservoirs. Solution maintenance station valve  64  can be actuated, either manually or automatically, to direct liquid flow between the liquid supply line  66  and any of the first  74 , second  76 , or third reservoir lines  80 . Removal of liquids from the container  14  can be accomplished by actuating the valve switch  36  to allow the flow of solution from the container  14  into a disposal unit. 
     E. Automated Control Unit 
     Referring to  FIG. 1 , coating apparatus  10  also includes a computerized control unit  46  to provide an automated system for operation of the conveyor track  16 , the gas supply source  18 , the irradiation station  32 , and, in some embodiments, the solution maintenance station  60  (shown in  FIGS. 5 and 6 ). The computerized control unit  46  can regulate and coordinate operation of parts of the coating apparatus  10 , for example: the speed, movement, and positioning of the conveyor track  16  in both clockwise and counterclockwise directions; the flow of gas from the gas supply source  18 , including pressure and duration of gas flow and the flow of gas; referring to  FIG. 4 , the movement of the radiation shield  52  of the irradiation station  32  and the emission of light by operation of the radiation power supply  44 ; and, referring to  FIG. 5 , the flow of fluids to and from the container  14  via the pump  63  of the solution maintenance station  60 . The computerized control unit can receive and integrate signals from the conveyor sensor  15 , and, referring to  FIG. 4 , the upper sensor  55 , and lower sensor  57 , of the irradiation station  32 . 
     In another embodiment, the coating apparatus can be manually operated, for example, by filling and dumping solutions from the container by hand. 
     F. Modes of Operation 
     According to the invention, a device to be coated is placed in the container  14 . Placement of the device into the container  14  can be carried out manually or by an automated or robotic system. The device placed into the container can be any device suitable for coating with the photoactivatable compound and polymerizable compound utilized in the invention. Such devices may be medical devices, including those adapted for use within or upon the body. Medical devices that are permanently implanted in the body for long-term use or short-term use are one general class of suitable devices. 
     Long-term devices include, but are not limited to, grafts, stents, stent/graft combinations, valves, heart assist devices, shunts, and anastomoses devices; catheters such as central venous access catheters; orthopedic devices such as joint implants, fracture repair devices, and artificial tendons, dental implants and dental fracture repair devices; intraocular lenses; surgical devices such as sutures and patches; synthetic prosthesis; and artificial organs such as artificial lung, kidney, and heart devices. 
     Short-term devices include, but are not limited to, vascular devices such as distal protection devices; catheters such as acute and chronic hemodialysis catheters, cooling/heating catheters, and percutaneous transluminal coronary angioplasty (PTCA) catheters; ophthalmic devices such as contact lenses and glaucoma drain shunts. 
     Other biomedical devices can also be coated, in whole or in part, using the apparatus and method of the present invention. These other biomedical devices include, but are not limited to, diagnostic slides such as gene chips, DNA chip arrays, microarrays, protein chips, and fluorescence in situ hybridization (FISH) slides; arrays, including cDNA arrays and oligonucleotide arrays; blood sampling and testing components; functionalized microspheres; tubing and membranes, e.g., for use in dialysis or blood oxygenator equipment; and blood bags, membranes, cell culture devices, chromatographic support materials, biosensors, and the like. 
     The apparatus and method for using the apparatus this invention are particularly well suited for coating devices such as distal protection devices (also known as emboli catching devices), e.g., of the type described in U.S. Pat. No. 6,245,089, the disclosure of which is incorporated herein by reference. 
     The devices to be coated by the apparatus and method of the invention can be made of any material that can suitably react with the photoactivatable compound. Examples of materials used to provide suitable device surfaces include polyolefins, polystyrenes, poly(alkyl)methacrylates and poly(alkyl)acrylates, polyacrylonitriles, poly(vinylacetates), poly(vinyl alcohols), chlorine-containing polymers such as poly(vinyl)chloride, polyoxymethylenes, polycarbonates, polyamides, polyimides, polyurethanes, polyvinylidene difluoride (PVDF), phenolics, amino-epoxy resins, polyesters, silicones, polyethylene terephthalates (PET), polyglycolic acids (PGA), poly-(p-phenyleneterephthalamides), polyphosphazenes, polypropylenes, parylenes, silanes, and silicone elastomers, as well as copolymers and combinations thereof, as well as cellulose-based plastics, and rubber-like plastics. See generally, “Plastics,” pp. 462-464, in  Concise Encyclopedia of Polymer Science and Engineering , Kroschwitz, ed., John Wiley and Sons, 1990, the disclosure of which is incorporated herein by reference. 
     Parylene is the generic name for members of a unique polymer (poly-p-xylylene) series, several of which are available commercially (e.g., in the form of “Parylene C”, “Parylene D” and “Parylene N”, from Union Carbide). For example, “Parylene C”, is a poly-para-xylylene containing a substituted chlorine atom, and can be used to create a moisture barrier on the surface of a medical device. Parylene C can be coated by delivering it in a vacuum environment at low pressure as a gaseous polymerizable monomer. The monomer condenses and polymerizes on substrates at room temperature, forming a matrix on the surface of the medical device. The coating thickness is controlled by pressure, temperature, and the amount of monomer or macromer used, in order to provide an inert, non-reactive barrier. In addition, materials such as those formed of pyrolytic carbon and silylated surfaces of glass, ceramic, or metal are suitable for coating according to the method of the invention. 
     According to the method of the invention, the device can be placed into container  14  that has been filed with a solution having a photoactivatable compound, or the solution can be added after the device has been placed into the container  14 . In one embodiment, the device is placed into the container  14  and then the container  14  is filled with a solution that contains a photoactivatable compound. In an alternate embodiment, the solution can be dispensed into the top of the container  14  manually in an amount sufficient to cover the device. 
     In another embodiment, the container  14  is brought into the proximity of a solution maintenance station  60 , as illustrated in  FIG. 5 , via the conveyor track  16 , and filled with a solution containing the photoactivatable compound. The container  14  can be properly positioned next to the solution maintenance station  60  following movement of the conveyor track  16  to where the conveyor sensor trip  33  (shown in  FIG. 3 ) actuates the conveyor sensor  15  (shown in  FIG. 1 ) and stops movement of the conveyor track  16 . When the container  14  is properly situated next to the solution maintenance station  60 , the supply line insertion mechanism  70  can move and insert the container port adapter  68  into the container liquid supply port  39 . The container port adapter  68  is then properly fit into the container liquid supply port  39  and the valve switch  36  is actuated to allow fluid into the container  14 . The solution maintenance station valve  64  is actuated to allow input of the solution that contains a photoactivatable compound from the first reservoir line  74  and the first reservoir  72 . The pump  63  can then be operated to withdraw solution that contains a photoactivatable compound from first reservoir  72  and ultimately into the container  14 . The pump  63  can be operated to deliver a selected amount of solution that contains a photoactivatable compound into the container  14 , generally in an amount sufficient to cover the device. 
     Suitable polymerizable monomer or macromer reagents are described, for instance, in PCT/US99/21247 entitled “Water-Soluble Coating Agents Bearing Initiator Groups And Coating Process” the disclosure of which is incorporated by reference. Such polymerizable monomers include hydrophilic monomers that are negatively charged, positively charged, or electrically neutral. Examples of suitable monomers containing electrically neutral hydrophilic structural units include acrylamide, methacrylamide, N-alkylacrylamides (e.g., N,N-dimethylacrylamide or methacrylamide, N-vinylpyrrolidinone, N-vinylacetamide, N-vinyl formamide, hydroxyethylacrylate, hydroxyethylmethacrylate, hydroxypropyl acrylate or methacrylate, glycerolmonomethacrylate, and glycerolmonoacrylate). Examples of suitable monomeric polymerizable molecules that are negatively charged at appropriate pH levels include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, AMPS (acrylamidomethylpropane sulfonic acid), vinyl phosphoric acid, vinylbenzoic acid, and the like. Examples of suitable monomeric molecules that are positively charged at appropriate pH levels include 3-aminopropylmethacrylamide (APMA), methacrylamidopropyltrimethylammonium chloride (MAPTAC), N,N-dimethylaminoethylmethacrylate, N,N-diethylaminoethylacrylate, and the like. 
     In an alternative embodiment, the polymerizable compounds of the present invention comprise macromeric polymerizable molecules. Suitable macromers can be synthesized from monomers such as those illustrated above. According to the present invention, polymerizable functional components (e.g., vinyl groups) of the macromer can be located at either terminus of the polymer chain, or at one or more points along the polymer chain, in a random or nonrandom structural manner. 
     The number of free-radical polymerizable groups per molecule can be varied according to the application. For example, it can be preferable to employ a macromer with just one free-radical polymerizable unit. In other instances, however, it can be preferable to employ a macromer with more than one, e.g., two or more polymerizable units per macromer. Additionally, the macromer of the present invention can contain structural features to provide improved affinity for water in a manner typically unavailable in small molecule structures (e.g., hydrophilic poly(ethylene glycol) materials). 
     Examples of suitable macromeric polymerizable compounds include methacrylate derivatives, monoacrylate derivatives, and acrylamide derivatives. Particularly preferred macromeric polymerizable compounds include poly(ethylene glycol)monomethyacrylate, methoxypoly(ethylene glycol)monomethacrylate, poly(ethylene glycol)monoacrylate, monomethyacrylamidopoly(acrylamide), poly(acrylamide-co-3-methacrylamidopropylacrylamide), poly(vinylalcohol)monomethacrylate, poly(vinylalcohol)monoacrylate, poly(vinylalcohol)dimethacrylate, and the like. 
     Such macromers can be prepared, for instance, by first synthesizing a hydrophilic polymer of the desired molecular weight, followed by a polymer modification step to introduce the desired level of polymerizable (e.g., vinyl) functional units. For example, acrylamide can be copolymerized with specific amounts of 3-aminopropylmethacrylamide comonomer, and the resulting copolymer can then be modified by reaction with methacrylic anhydride to introduce the methacrylamide functional units, thereby producing a useful macromer for purposes of this invention. 
     Poly(ethylene glycol) of a desired molecular weight can be synthesized or purchased from a commercial source, and modified (e.g., by reaction with methacrylyl chloride or methacrylic anhydride) to introduce the terminal methacrylate ester units to produce a macromer useful in the process of this invention. Some applications can benefit by use of macromers with the polymerizable units located at or near the terminus of the polymer chains, whereas other uses can benefit by having the polymerizable unit(s) located along the hydrophilic polymer chain backbone. 
     Such monomeric and macromeric polymerizable molecules can be used alone or in combination with each other, including for instance, combinations of macromers with other macromers, monomers with other monomers, or macromers combined with one or more small molecule monomers capable of providing polymeric products with the desired affinity for water. Moreover, the above polymerizable compounds can be provided in the form of amphoteric compounds (e.g., zwitterions), thereby providing both positive and negative charges. 
     The photoactivatable compound has at least one first photoactivatable group able to be activated by the irradiation provided by the irradiation station  32  and form a covalent bond with the surface of the device. The photoactivatable compound also has at least one second photoactivatable group able to be activated to initiate the polymerization of a polymerizable compound. The second photoactivatable group can also be activated by irradiation provided by the irradiation station. Photoactivatable groups that are able to be activated to, for example, form covalent bonds with the surface of the device or to provide a radical to initiate polymerization of the polymerizable compound, can also be referred to as “pendent” or “latent reactive” groups. These also include photoactivatable groups that have been activated but have returned to a ground state and capable of being subsequently activated. 
     According to one method of using the apparatus and the compounds described herein, upon irradiation of the photoactivatable compound in the presence of a device, the first photoactivatable group is capable of covalently bonding to the device surface, and upon bonding of the first photoactivatable groups to the surface, the second photoactivatable group is: i) restricted from reacting with either a spacer or the device surface, ii) capable of reverting to an inactive state, and iii) upon reverting to their inactive state, are thereafter capable of being reactivated in order to later initiate polymerization of a polymerizable compound, thereby forming a polymer on the surface. 
     The first and second photoactivatable groups can be of the same or different types, and the distinction between the two can be determined under the conditions, and at the time of use. Generally, the first photoactivatable group is defined (from amongst those originally present) as one or more photoactivatable groups of the photoactivatable compound that become attached to the surface of the device. This serves to define the second photoactivatable group (i.e., as pendent or latent reactive) as one or more photoactivatable groups of the bound photoactivatable compound that are not covalently attached to the surface of the device, and hence revert to an activatable form. According to the invention, it has been discovered that the second photoactivatable groups are particularly well suited to serve as photoinitiators for a polymerization reaction. Without intending to be bound by theory, it appears that the utility of such photoactivatable compounds for use in grafting is improved also by the photoactivatable compound&#39;s lack of solubility in polar solvent. The photoactivatable compound, or grafting initiator, of this type of invention can be selected from the group consisting of tetrakis(4-benzoylbenzyl ether), the tetrakis(4-benzoylbenzoate ester) of pentaerythritol, and an acylated derivative of tetraphenylmethane. 
     The apparatus can also utilize photoactivatable compounds comprising a nonpolymeric core molecule having attached thereto, either directly or indirectly, one or more substituents comprising negatively charged groups, and two or more photoactivatable species, wherein the photoactivatable species are provided as discrete photoactivatable groups. The photoactivatable species comprise one or more of the first photoactivatable groups adapted to attach the photoactivatable compound to a surface, and one or more second photoactivatable groups adapted to initiate photopolymerization of the polymerizable compound. Suitable reagents of this type are described, for instance, in U.S. Pat. No. 6,278,018 entitled “Surface Coating Agents” the disclosure of which is incorporated by reference. 
     The photoactivatable compound can comprise a conjugated cyclic diketone having attached thereto, either directly or indirectly, one or more substituents comprising negatively charged groups, and wherein each ketone group of the diketone is adapted to serve as a photoactivatable moiety capable of being activated in order to provide a free radical. The conjugated cyclic diketone can be a quinone selected from substituted and unsubstituted benzoquinone, camphorquinone, naphthoquinone, and anthraquinone. 
     Such photoactivatable compounds can comprise a nonpolymeric core molecule having attached thereto, either directly or indirectly, one or more substituents comprising negatively charged groups, and two or more photoactivatable groups. Such photoactivatable compounds can be selected from the group 4,5-bis(4-benzoylphenylmethyleneoxy)benzene-1,3,-disulfonic acid dipotassium salt, 2,5-bis(4-benzoylphenylmethyleneoxy)benzene-1,4-disulfonic acid dipotassium salt, 2,5-bis(4-benzoylphenylmethyleneoxy)benzene-1-sulfonic acid mono (or di-) sodium salt, a hydroquinone monosulfonic acid derivative, an anthraquinone sulfonic acid salt, and a camphorquinone derivative. Optimally, the photoactivatable compound is selected from 4,5-bis(4-benzoylphenylmethyleneoxy)benzene-1,3,-disulfonic acid dipotassium salt, 2,5-bis(4-benzoylphenylmethyleneoxy)benzene-1,4-disulfonic acid dipotassium salt, and 2,5-bis(4-benzoylphenylmethyleneoxy)benzene-1-sulfonic acid mono (or di-) sodium salt. 
     Photoactivatable compounds of this type can be selected from the group 4,5-bis(4-benzoylphenylmethyleneoxy)benzene-1,3-disulfonic acid dipotassium salt, and 2,5-bis(4-benzoylphenylmethyleneoxy)benzene-1,4-disulfonic acid dipotassium salt. 
     The photoactivatable compound of the present invention can be provided in the form of an initiator of the general formula:
 
X—Y—X
 
wherein each X is independently a photoactivatable group and Y is a portion of the photoactivatable compound that has one or more charged groups. Such initiators are described, for instance, in Applicant&#39;s U.S. Pat. No. 5,714,360, the disclosure of which is incorporated herein by reference.
 
     An initiator of this type includes one or more charged groups, and optionally one or more additional photoactivatable groups, included in the radical identified in the empirical formula as “Y.” A “charged” group, when used in this sense, refers to groups that are present in ionic form, i.e., carry an electrical charge under the conditions (e.g., pH) of use. The charged groups are present, in part, to provide the compound with the desired water solubility. 
     Preferred Y groups are nonpolymeric, that is, they are not formed by polymerization of any combination of monomers or macromers. Nonpolymeric agents are preferred since they will tend to have lower molecular mass, which in turn means that they can generally be prepared to have a higher ratio of photoactivatable groups per unit mass. In turn, they can generally provide a higher coating density of photoactivatable groups than comparable photoactivatable polymeric agents. 
     The type and number of charged groups of the photoactivatable compound are sufficient to provide the agent with a water solubility (at room temperature and optimal pH) of at least about 0.1 mg/ml, 0.5 mg/ml or up to 5 mg/ml. Given the nature of the surface coating process, photoactivatable compound solubility levels of at least about 0.1 mg/ml are generally adequate for providing useful coatings of target molecules on surfaces. 
     Examples of suitable charged groups include, but are not limited to, salts of organic acids (such as sulfonate, phosphonate, and carboxylate groups), onium compounds (such as quaternary ammonium, sulfonium, and phosphonium groups), and protonated amines, as well as combinations thereof. An example of an agent employing charged groups other than quaternary ammonium compounds is provided in Formula X of Table I of U.S. Pat. No. 5,714,360, the disclosure of which is incorporated herein by reference. By reference to the empirical formula provided above, it can be seen that R 3  in Formula X would be a lone pair of electrons, in order to provide a tertiary amine group, and R 2  would contain a charged sulfonate group in a radical of the formula —CH 2 —CH 2 —SO 3 Na. Sufficient overall charge to render the compound water soluble is provided by the negative charge of the remote sulfonate group. 
     A suitable charged group for use in preparing compounds of the present invention is a quaternary ammonium group. The term “quaternary ammonium,” as used herein, refers to organic derivatives of NH 4   +  in which the hydrogen atoms are each replaced by radicals, thereby imparting a net positive charge on the radical. The remaining counter-ion can be provided by any suitable anionic species, such as a chloride, bromide, iodide, or sulfate ion. 
     In an embodiment, two or more photoactivatable groups are provided by the X groups attached to the central Y portion of the photoactivatable compound. Upon exposure to a suitable light source, each of the photoactivatable groups are subject to activation. The term “photoactivatable group,” as used herein, refers to a chemical group that responds to an applied external ultraviolet or visible light source in order to undergo active specie generation, resulting in covalent bonding to an adjacent chemical structure (via an abstractable hydrogen). 
     Acceptable reagents of this type are selected from the group ethylenebis(4-benzoylbenzyldimethylammonium)dibromide (Diphoto-Diquat); hexamethylenebis(4-benzoylbenzyldimethylammonium)dibromide (Diphoto-Diquat); 1,4-bis(4-benzoylbenzyl)-1,4-dimethylpiperazineadiium dibromide (Diphoto-Diquat); bis(4-benzoylbenzyl)hexamethylenetetraminediium dibromide (Diphoto-Diquat); bis[2-(4-benzoylbenzyldimethylammonio)ethyl]-4-benzoylbenzyldimethylammonium)tribromide (Triphoto-Triquat); 4,4-bis(4-benzoylbenzyl)morpholinium bromide (Diphoto-Monoquat); ethylenebis[(2-(4-benzoylbenzyldimethylammonio)ethyl)-4-benzoylbenzylmethylammonium]tetrabromide (Tetraphoto-Tetraquat); 1,1,4,4-tetrakis(4-benzoylbenzyl)piperazinediium Dibromide (Tetraphoto-Diquat); and N,N-bis[2-(4-benzoylbenzyloxy)ethyl]-2-aminoethanesulfonic acid, sodium salt (Diphoto-Monosulfonate), and analogs (including those having alternative counter ions) thereof, corresponding to Compounds II through X, respectively, of the above-captioned &#39;360 patent. Terms such as “Diphoto-Diquat” are used herein to summarize the number of respective groups (e.g., photo groups, quaternary ammonium groups, etc.) per reagent molecule. 
     Photoactivatable groups respond to a specific applied external ultraviolet or visible light source to undergo active specie generation with resultant covalent bonding to an adjacent chemical structure, e.g., as provided by the same or a different molecule. Photoactivatable species are those groups of atoms in a molecule that retain their covalent bonds unchanged under conditions of storage but that, upon activation by a specific applied external ultraviolet or visible light source, form covalent bonds with other molecules. 
     Photoactivatable groups generate active species such as free radicals and particularly nitrenes, carbenes, and excited states of ketones upon absorption of electromagnetic energy. Photoactivatable groups can be chosen to be responsive to various portions of the electromagnetic spectrum, and photoactivatable species that are responsive to the ultraviolet and visible portions of the spectrum can be utilized and can also be referred to herein as a “photochemical group” or “photogroup.” 
     Photoactivatable aryl ketones can be used, such as acetophenone, benzophenone, anthraquinone, anthrone, and anthrone-like heterocycles (i.e., heterocyclic analogs of anthrone such as those having N, O, or S in the 10-position), or their substituted (e.g., ring substituted) derivatives. Examples of such aryl ketones include heterocyclic derivatives of anthrone, including acridone, xanthone, and thioxanthone, and their ring substituted derivatives. Thioxanthone, and its derivatives, having excitation energies greater than about 360 nm are utilized in some embodiments. 
     The functional groups of such ketones are readily capable of undergoing the activation/inactivation/reactivation cycle described herein. Benzophenone is an exemplary photoactivatable moiety, since it is capable of photochemical excitation with the initial formation on an excited singlet state that undergoes intersystem crossing to the triplet state. The excited triplet state can insert into carbon-hydrogen bonds by abstraction of a hydrogen atom (from a device surface, for example), thus creating a radical pair. Subsequent collapse of the radical pair leads to formation of a new carbon-carbon bond. If a reactive bond (e.g., carbon-hydrogen) is not available for bonding, the ultraviolet light-induced excitation of the benzophenone group is reversible and the molecule returns to ground state energy level upon removal of the energy source. Photoactivatible aryl ketones such as benzophenone and acetophenone are of particular importance inasmuch as these groups are subject to multiple reactivation in water and hence provide increased coating efficiency. 
     The photoactivatable compound is typically used in the range of 0.1-5 mg/ml. Solvents for the photoactivatable compound include water, alcohol, other suitable solvents, and mixtures thereof and are compatible with the device subject to the grafting/coating procedure. The solution containing the photoactivatable compound can be added to the container  14  in an amount sufficient to coat the device. 
     Once the container  14  is filled with the solution containing the photoactivatable compound in an amount sufficient to cover the device, the container  14  can be moved on the conveyor track  16  to the irradiation station  32 . The conveyor track  16  can be operated at a particular speed so that the device is immersed in the solution containing the photoactivatable compound for a predetermined time prior to exposure to the radiation source. 
     Irradiation of the device in the presence of the solution of photoactivatable compound is performed at the irradiation station  32 . The container  14  is transported to the irradiation station  32  when the radiation shield  52  is in the up position. The container  14  can be properly situated by the irradiation station  32  by any suitable mechanism, for example by a sensor on the irradiation station which causes the conveyor track  16  to pause, or by setting the conveyor track  16  to travel a defined distance and coordinating the positioning of the irradiation station  32  and the container  14 . The radiation shield  52  can then be lowered to surround the container  14 . The radiation power supply  44  is then activated to provide light via the radiation emitter  40 . 
     The device in the container  14  can be irradiated for an amount of time suitable to activate and covalently bind the photoactivatable compound to the device. The amount of ultraviolet light provided activates at least one photoactivatable group on the photoactivatable compound wherein the activated photoactivatable group reacts with the surface of the substrate and forms a covalent bond. Activated unreacted photoactivatable groups of a bound photoactivatable compound can return to a ground state and can be subsequently activated by irradiation. Typically, the device is irradiated for a period of 1-3 minutes, a dose of 1-3 mW/cm 2 . The device is typically maintained at a distance of approximately 4-12 inches from the light output. Generally, the device should not be subjected to excessive irradiation as it may alter the material of the device and alter its structure. 
     Following irradiation, the container  14  can be moved from or maintained at the irradiation station  32 . In one embodiment, the container  14  is maintained at the irradiation station  32  and, with the radiation emitter  40  in the off position, a solution containing a polymerizable compound is manually added to the container. Following the addition of the polymerizable compound, an inert gas is bubbled through the solution for a period of time sufficient to purge the majority of oxygen from the solution. This time can be approximately 10 minutes or more. After purging the radiation emitter  40  is turned on. 
     After the photoactivatable compound has been covalently bound to the device, in some embodiments the solution is removed from the container  14 . The solution can be removed manually, for example, by removing the container  14  from the apparatus and decanting the solution, or can be removed through use of a solution maintenance station  60 . Following bonding of the photoactivatable compound to the device, the container  14  can, for example, be transported away from the irradiation station  32  via the conveyor track  16  and to the solution maintenance station  60  where the solution can be removed. The container  14  can be connected to the liquid supply port  40  and the solution can be recycled into the first reservoir  72  or can be disposed of. 
     In some embodiments, the device can be washed after binding the photoactivatable compound to the device. In one embodiment, when the container  14  is connected to the solution maintenance station  60 , a wash solution from the second reservoir  78  can be pumped into the container  14 . The wash solution can be any liquid suitable for removing excess unbound photoactivatable compound from the device and container  14 . The wash solution can then be discarded, or recycled into the second reservoir  78 . The wash process can be repeated one or more times. In another embodiment, the wash step can be performed manually. 
     After the photoactivatable compound has been bound to the device, a solution containing a polymerizable compound can be added to the container  14  having the device. In some embodiments the solution can be added manually, for example by adding solution to the container  14  and decanting the solution. In other embodiments the solution can be added through use of a solution maintenance station  60  when the container  14  is connected to the solution maintenance station  60 . A solution containing a polymerizable compound from the third reservoir  82  can be pumped into the container  14 . The solution containing a polymerizable compound can be added to the container  14  in an amount sufficient to cover the device. 
     During or after the addition of the solution containing the polymerizable compound, gas can be bubbled through the container  14 . Valve switch  36  can be actuated to allow the flow of gas from the gas supply line  24  into the container  14  having the solution. According to the invention, gas is bubbled through the container  14  in an amount sufficient to purge oxygen from the solution. The solution can be purged for an amount of time sufficient to reduce oxygen content in the solution to a level wherein polymerization of the polymerizable compound is not inhibited. The container  14  can be transported on the conveyor track  16  while the gas is bubbling through the solution. The speed of the conveyor track  16  can be controlled so that gas is bubbled through the solution for a sufficient amount of time before the device is irradiated. 
     Irradiation of the device in the presence of the solution of polymerizable compound is also performed at the irradiation station  32 . Gas can be continuously bubbled through the solution in the container during this step. The device in the container  14  can be irradiated for an amount of time sufficient to activate the reactive photoactivatable groups of the bound photoactivatable compound and cause the polymerization of the polymerizable material on the surface of the device. 
     The polymerizable compound is provided to the container at a concentration in the range of 0.1-100%, depending on the grafting initiator used. The solvent for the solution is typically water. The amount of energy delivered in order to promote polymerization is typically more than the step of bonding the grafting initiator to the device. Irradiation time is approximately 1-5 minutes. 
     After coating the device with the polymerizable material the solution containing the polymerizable material can be recycled to a solution reservoir or can be discarded. 
     It will be apparent to those skilled in the art that many changes can be made in the embodiments described without departing from the scope of the present invention. Thus the scope of the present invention should not be limited to the embodiments described in this application, but only by embodiments described by the language of the claims and the equivalents of those embodiments.