WO2009123624A1

WO2009123624A1 - Method and system for coating an article

Info

Publication number: WO2009123624A1
Application number: PCT/US2008/059029
Authority: WO
Inventors: John Liebeskind; Craig A. Olbrich; Darin K. Luse; Chuck Metge; Wayne E. Gisel; Casey Miller; David R. Otis
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2008-04-01
Filing date: 2008-04-01
Publication date: 2009-10-08
Also published as: TW200946247A

Abstract

A method of coating an article including obtaining an image of the article with the image being limited to an area fraction of the article. A coating is applied onto the area fraction.

Description

METHOD AND SYSTEM FOR COATING AN ARTICLE

Background

Cardiovascular disease exacts a heavy toll on the human race. For a long time, cardiac failure commonly resulted in death or long-term impairment. For those fortunate to survive a heart attack, open chest surgery to repair the damage was almost a certainty. However, the introduction of modern interventional surgery has greatly expanded the options for treating cardiac patients. In many cardiac patients, one or more arteries are occluded, which limits blood flow to the heart. In this situation, one interventional treatment includes placing a stent within the occluded artery after dilating the occluded portion with an angioplasty balloon. In many instances, a therapeutic coating is provided on a surface of the stent to deliver one or more drugs to arteries in which the stent is mounted.

Different strategies are employed for coating a stent. In some instances, an attempt is made to coat all surfaces of a stent, which is accomplished via dipping or spraying. However, in other instances, it is desired to coat just one side of a stent, such as the outer surface or abluminal side of the stent. This latter process is considerably more difficult to accomplish due to the accuracy and precision required to coat just one side of the stent. In addition, conventional methods of coating are time consuming and cumbersome when applied to the often, complex structure of a stent. Yet another factor complicating the accurate coating of a stent is the small, but identifiable variances that occur from stent to stent.

Besides stents, many other implantable medical devices have coatings that are applied to their outer surfaces. For example, dental implants, orthopedic implants, and ocular implants are just a few of the types of medical appliances that receive a coating prior to implantation. Like the stent, these implantable medical devices also demand precise and accurate applications of the coating material. For these reasons, surgeons and medical device manufacturers still strive to find accurate and efficient techniques to coat a stent and/or other medical appliances insertable into a body.

Brief Description of the Drawings

Figure 1 is schematic illustration of a method and system for coating a medical appliance, according to one embodiment of the present disclosure.

Figure 2 is block diagram illustrating an applicator manager, according to one embodiment of the present disclosure. Figure 3 A is a schematic illustration, including an end view of a medical appliance, of a method of imaging an area fraction of the medical appliance, according to one embodiment of the present disclosure.

Figure 3B is a schematic representation of an image of a top view of the medical appliance of Figure 3A, according to one embodiment of the present disclosure.

Figure 4 A is a schematic representation of an image pixel map of the area fraction shown in Figure 3B, according to one embodiment of the present disclosure.

Figure 4B is a schematic illustration of a centerline pattern of the image pixels of the struts of the area fraction of the medical appliance shown in Figure 3B, according to one embodiment of the present disclosure.

Figure 4C is a schematic illustration of an array of nozzle scan paths mapped relative to the centerline pattern of image pixels shown in Figure 4B, according to one embodiment of the present disclosure. Figure 5A is a diagram illustrating a method of selecting target firing points relative to a minimum separation distance between adjacent potential firing points, according to one embodiment of the present disclosure.

Figure 5B is a diagram illustrating another aspect of a method of selecting target firing points relative to a minimum separation distance between adjacent potential firing points, according to one embodiment of the present disclosure. Figure 6 is top view schematically illustrating movement of a printhead in a method of coating an array of medical appliances, according to one embodiment of the present disclosure.

Figure 7 is top view schematically illustrating movement of a printhead in a method of coating an array of medical appliances, according to one embodiment of the present disclosure.

Figure 8A is a schematic illustration of an array of nozzle scan paths mapped relative to centerline image pixels of the struts of an area fraction of a medical appliance, according to one embodiment of the present disclosure. Figure 8B is a schematic illustration of a shifted position of the array of nozzle scan paths mapped relative to the centerline image pixels of Figure 8A, according to one embodiment of the present disclosure.

Figure 9 is a flow diagram of a method of coating a medical appliance, according to one embodiment of the present disclosure. Figure 10 is a flow diagram of a method of coating a medical appliance, according to one embodiment of the present disclosure.

Figure 11 is a diagram illustrating a method of coating a three- dimensional object, according to one embodiment of the present disclosure.

Detailed Description

In the following Detailed Description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. In this regard, directional terminology, such as "top," "bottom," "front," "back," "leading," "trailing," etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments of the present disclosure can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following Detailed Description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims. Embodiments of the present disclosure relate to a method and system for coating a medical appliance, such as a stent or other implantable medical device. In one embodiment, instead of conventionally coating one medical appliance at a time, in one embodiment, an array of medical appliances are both imaged and coated simultaneously. In particular, an image is obtained of an area fraction of each medical appliance and then that area fraction is coated via ejection of drops from a printhead onto a top surface of the area fraction of each respective medical appliance. Accordingly, one area fraction (of each medical appliance) is imaged at a time and then application of the coating material is limited to partial or complete coating of that area fraction before another area fraction is imaged and coated (partially or completely coated).

In one aspect, the application of the coating material is limited to an abluminal side (i.e., outer surface) of the stent or other implantable medical appliance. A few non-limiting examples of implantable medical appliances suitable for coating via embodiments of the method and system include dental implants, ocular implants, non-stent drug delivery structures, sensors for monitoring blood pressure, glucose or other parameters, orthopedic implants (e.g., screws, artificial joints, etc.), cochlear implants, and electrical leads (e.g., cardiac leads). In one embodiment, prior to applying the coating material to an area fraction of the respective medical appliances, a target coating pattern is identified for the outer surface of the medical appliances for each respective area fraction. Using this target coating pattern, a set of target firing points (on which drops will be deposited) is produced based on an intersection of the target coating pattern with nozzle scan paths of the printhead. In one embodiment, the target firing points elected for drop deposition are limited to those target firing points that are separated from each other by a minimum distance. The non- elected target firing points are chosen as active target firing points in a later pass of the printhead over the medical appliances. In one embodiment, the implantable medical appliance comprises a stent including a network of struts and the target coating pattern comprises a centerline pattern of the struts of the stent. In one aspect, ejecting drops onto the target coating pattern results in accurate and precise coating limited to a top surface of the medical appliance without seepage of the coating material onto non-target portions of the medical appliance. In one embodiment in which the medical appliance comprises a stent, ejecting drops onto the target coating pattern that corresponds to a centerline of the struts (i.e., a centerline pattern) results in accurate and precise coating limited to a top surface of the struts of the stent (or other medical appliance) without seepage of the coating material onto the edges of the struts. After ejecting drops in a first alignment position of the printhead, in subsequent passes over the medical appliances, the printhead is shifted into alignment with image pixels that fall between the original nozzles scan paths (i.e., the position of the nozzle scan paths in the first alignment position). This arrangement increases the accuracy and precision in depositing drops on the target coating pattern (e.g., the centerline pattern) of the components of the medical appliances. In one embodiment, the method includes determining the centerline pattern with a resolution greater than a resolution of the image of the area fraction. This arrangement results in an intermediate bitmap with smaller pixel size. If the pixel size of this intermediate bitmap is smaller than spacing between adjacent nozzles (i.e., the nozzle spacing), then a series of bitmaps are generated by finding the intersection of the nozzle scan paths with the centerline pattern. The different bitmaps in the series are generated by shifting the nozzle scan paths by distances less than the nozzle spacing. In one aspect, if the resulting coverage on the appliance for each drop of coating material (e.g., a drop size) is larger than the nozzle shifting distance, then one need not shift the nozzles to every possible position on the centerline pattern to get a continuous coating. In another aspect, the resolution along the scanning path is sufficient to place the drops close to the intended centerline.

Once a desired amount of coating material has been applied to a first area fraction of the respective medical appliances, the medical appliances are rotated simultaneously to enable imaging and coating a second area fraction of the medical appliance. In one aspect, the second area fraction overlaps the first area fraction. In one embodiment, the degree of overlap is about 50 percent, while in other embodiments the degree of overlap can be more or less than 50 percent.

Further, this iterative process is repeated one or more times about the circumference of the medical appliance until the desired thickness of coating material is achieved uniformly in the target coating pattern over the top surface of each of the medical appliances.

In one aspect, the overlap between the first area fraction and the second area fraction provides some intended variability in drop placement because the portion of the first area fraction that overlaps with the second area fraction becomes part of the image obtained of the second area fraction. Accordingly, this "overlapping" portion of the first area fraction is re-imaged as part of the second area fraction, and hence, will be re-coated in a limited fashion providing some overlap between previously coated firing points and newly coated firing points. When considered in aggregate, this overlap of firing points between the first area fraction and the second area fraction facilitates producing a substantially continuous coating over the target coating pattern of the top surface of the stent or other implantable medical appliance.

In one embodiment, the substantially continuous coating is applied to substantially the entire abluminal side or outer surface of the medical appliance. In other embodiments, the application of the substantially continuous coating is limited to target portions (according to the target coating pattern) of the outer surface of the medical appliance. In a few non-limiting examples, the targeted portion(s) comprise a spiral pattern, one or more islands, or a more complex pattern. In each case, the respective targeted portion (e.g., each spaced apart segment) receives a substantially continuous coating while non-targeted portions of the outer surface of the medical appliance (between the spaced apart segments) do not receive any coating. Accordingly, in each place where the coating is applied, the coating is substantially continuous. However, as illustrated by these examples, application of this substantially continuous coating does not require coating of the entire outer surface of the medical appliance.

In one embodiment, these methods enable high throughput coating of a large number of medical appliances. In one instance, a quantity of medical appliances that is simultaneously coated via these methods is on the order of at least two orders of magnitude (e.g., 10-99 or more), while in other instances, the quantity is on the order of at least three orders of magnitude (e.g., 100-999 or more). In one aspect, this high throughput capacity is achieved while maintaining accuracy in depositing drops in a pattern limited to a top surface of the medical appliances because just one area fraction (of the respective medical appliances) at a time is imaged and coated, and in light of other parameters (e.g., centerline determination, an expanded bitmap, etc.) described in more detail throughout the present disclosure. While the preceding description focuses on implantable medical appliances, the method (and system) of applying coating materials by area fractions also are applicable to other types of three-dimensional objects that are not medically related and/or not implantable.

Accordingly, the method and system according to the present disclosure provides coordinated control over the time between, and the location of, fired drops of coating material for a large number of medical appliances or other three-dimensional objects to result in a highly accurate, high throughput coating treatment.

These embodiments, as well as others, are described and illustrated in association with Figures 1-10.

A system 20 for coating an array 50 of medical appliances 52 according to one embodiment of the present disclosure is shown in Figure 1. System 20 includes an applicator 30 configured to coat medical appliances 52 via an array 40 of nozzles 42 of a printhead 44. The printhead 44 comprises a drop-on- demand fluid ejection device. In one embodiment, the printhead 44 comprises a thermal inkjet printhead. In some other embodiments, the printhead 44 comprises any one of a piezoelectric printhead, a bubble jet printhead, or other suitably accurate printhead.

In one embodiment, system 20 is limited to a single printhead 44. In other embodiments, system 20 includes more than one printhead 44.

In one aspect, the printhead 44 includes at least one row 41 of nozzles 42 aligned generally in series across one dimension (e.g., a length) of the single printhead 44. However, it is understood that in some instances, the nozzles 42 are arranged with some degree of stagger (e.g., micro-stagger) while still generally being aligned in series relative to a length of the printhead 44. Each nozzle 42 is individually controllable via a controller 60 of applicator 40 so that the respective nozzles 42 can be activated one at a time or in groups.

In one non-limiting configuration, the longitudinal axes of the respective medical appliances 52 are aligned generally parallel to each other. In one aspect, as illustrated in Figure 1, the medical appliances 52 are arranged in side-by-side pattern underneath a path of printhead 44 with their longitudinal axes generally parallel to a longitudinal axis of the row 41 of nozzles 42.

In another aspect, applicator 30 includes a positioner 62 configured to movably position printhead 44 relative to medical appliances 52. As represented by the directional arrows x and y shown in Figure 1, positioner 62 is capable of moving printhead 44 in a first direction (e.g., represented by directional arrow x) generally perpendicular to a longitudinal axis of the respective medical appliances 52 as well as in a second direction (e.g., represented by directional arrow y) generally parallel to the longitudinal axis of the respective medical appliances 52.

In another aspect, each medical appliance 52 is slidably mounted onto a mandrel 54. A rotational mechanism 58 controlled by controller 60 is operatively coupled to each mandrel 54 via a linkage 59 and configured to selective rotate each mandrel 54 to thereby control a rotational position of each medical appliance 52 relative to printhead 44 and/or an imager 70. In one embodiment, rotational mechanism 58 and linkage 59 are configured to rotate the mandrels 54 (and therefore the associated medical appliances 52) in concert. In another embodiment, rotational mechanism 58 and linkage 59 are configured to rotate each mandrel 54 separately from the other respective mandrels 52 or to rotate some mandrels 54 in groups.

In one embodiment, system 20 includes an imager 70 configured to obtain an image of the medical appliances 52. In one aspect, imager 70 is positionable, via cooperation with positioner 62, over the array 50 of medical appliances 52. While represented schematically as illustrated in Figure 1, imager 70 is sized and shaped to capture an image encompassing a portion of all of the medical appliances 52. In one aspect, the imager 70 captures a top view of an area fraction of each medical appliance 52 with the area fraction of the respective medical appliances 52 being substantially identical in its general parameters (i.e., length, width, scope of magnification, etc.) for each medical appliance 52.

The obtained image of the area fraction of the respective medical appliances 52 is used to develop a target map of firing points to enable printhead 44 to make a single pass over the array 50 of medical appliances while depositing drops of coating material onto a selected subset of the mapped firing points (of the area fraction of the respective medical appliances), as further described in association with Figures 3A-5B.

Upon completing application of a predetermined volume of coating material to the first area fraction, rotational mechanism 58 rotates all of the medical appliances 52 (via rotation of the mandrels 54) to expose another portion of the medical appliances to the imager 70. After obtaining a single image of a second area fraction of the medical appliances 52, the process of determining firing points and applying the coating material to the second area fraction is performed as previously described. In one aspect, the second area fraction overlaps the first area fraction. Upon completion of treatment of the second area fraction, this process is repeated iteratively until the entire circumference of the respective medical appliances 52 has been coated one or more times.

In one embodiment, the imager 70 comprises an area scanning camera while in other embodiments; the imager 70 comprises a line scan camera.

Figure 2 is a block diagram of a manager 100 of system 20, according to one embodiment of the present disclosure. In one embodiment, manager 100 is stored within a memory of controller 60 (Figure 1) while in other embodiments, manager 100 is stored in a memory of a computing unit associated with applicator 30 of system 20. As illustrated in Figure 2, manager 100 comprises a user interface 102, an appliance module 110, a printhead module 112, an imaging module 114, and a firing module 116. In one aspect, the user interface 102 comprises a graphical user interface configured to display, and enable operation of, the various parameters, components, and functions of the respective modules 110, 112, 114, and 116. Accordingly, via user interface 102, manager 100 represents the display of parameter, components, and functions of modules 110, 112, and 114 and/or a vehicle for activating those respective parameters, components, and functions.

In one embodiment, the appliance module 110 of manager 100 is configured to specify the particular parameters of the array 50 of medical appliance 52 to controller 60 and printhead 44. These parameters enable accurate, reproducible ejection of drops from the printhead 44 onto targeted locations of the medical appliances 52. In one embodiment, as illustrated in Figure 2, the appliance module 110 includes a dimension parameter 122, a quantity parameter 124, a row parameter 126, and a column parameter 128. The dimension parameter 122 enables identification of the length, width, and/or other dimensional parameters of each respective medical appliance 52. The quantity parameter 124 enables identification of a quantity of medical appliances 52 to be imaged and/or coated. In one aspect, this quantity information is used by controller 60 to coordinate the duration of passes made by printhead 44 and/or the duration of drying time between successive passes over the same set of medical appliances. The row parameter 124 and the column parameter 126 enable identification of, and control over, the number of rows and columns, respectively of medical appliances 52 to be coated. This row and column information is used to coordinate the direction of passes made by printhead 44, via positioner 62, over multiple rows and/or multiple columns of medical appliances 52. One example of an array of medical appliances 52 having multiple columns and rows is later described in more detail in association with Figures 6 and 7.

In one embodiment, the printhead module 112 of manager 100 is configured to enable control over the operations of printhead 44 generally and to control individual nozzles 52. In cooperation with positioner 62, the printhead module 112 also enables control to move nozzles 52 of printhead 44 in a strategic pattern over the array 50 of medical appliances 52. In one embodiment, as illustrated in Figure 2, the printhead module 112 comprises a grouping parameter 140, a spacing parameter 142, a shift parameter 144, and a direction parameter 146. The grouping parameter 140 enables identification of, and control over, how various nozzles 42 are grouped together for firing a group of nozzles at one time. This grouping parameter 140 is operated in conjunction with the spacing parameter 142 which is configured to specify the spacing (i.e., the number of nozzles) that determines which nozzles form a group. In one non- limiting example, one group of nozzles comprises every fourth nozzle (in a row of nozzles) so that there is a spacing of three nozzles between the respective nozzles of the group. The spacing is generally selected to prevent coalescence between adjacently deposited drops (onto the top surface of the medical appliance) and insure sufficient drying time before a subsequent pass of the printhead deposits additional drops from another group of nozzles onto other target points of each medical appliance 52. Application of the grouping parameter 140 and the spacing parameter 142 are described later in more detail in association with Figures 4C-5B.

In another aspect, the shift parameter 144 of the printhead module 112 enables identification of, and control over, shifting printhead 112 a controlled distance to reposition the nozzle scan paths relative to components of the respective medical appliance 52 (e.g., relative to the struts of the stent). This repositioning aligns the nozzles scan paths into a position intermediate to previous nozzle scan paths, thereby insuring deposition of coating material onto target points not previously coated in prior passes of the printhead 44.

In one aspect, direction parameter 145 of the printhead module 112 enables identification of, and control over, moving printhead in a forward or rearward direction (represented by directional arrow x in Figure 1), as well as a side-to-side direction (represented by directional arrow y in Figure 1) to place the nozzles 42 in a position to eject drops at targeted locations of the medical appliances 52. Referring again to Figure 2, the imaging module 114 is configured to control obtaining images of the medical appliances 52. In one embodiment, the imaging module 114 enables obtaining an image of a top view of an array of medical appliances 52. In one embodiment, the imaging module 114 comprises an area fraction parameter 160, a pixel function 161, and a centerline parameter 162. The area fraction parameter 160 enables taking an image of the medical appliances 52, as seen from the top view, and isolating a portion of the image. This isolated portion of the image corresponds to an area fraction of each of the respective medical appliances 52. In one example, the area fraction corresponds to a radial sector or portion of an outer surface of a generally tubular medical appliance, such as a stent. In other embodiments, a substantially similar type of image is obtained of area fractions of an array of other types of three- dimensional objects. However, the shape of the area fraction in other embodiments is not limited to a radial sector of a tubular member.

In one aspect, the area fraction parameter 160 enables simultaneously identifying a substantially similar portion of each medical appliance 52. Via the image, this arrangement further enables simultaneously applying a coating regimen to a multitude of medical appliances 52 with each pass of the printhead 44 (e.g., array of nozzles) instead of applying a coating just a single medical appliance as occurs in many conventional systems and methods. By limiting the application of coating material to one targeted area of the respective medical appliances 52 at a time, a greater precision and accuracy is achieved in ejecting drops of the coating material, which ultimately results in a more accurate and uniform coating over each of the entire medical appliances, as later described in more detail in association with Figures 3A- 10.

In one embodiment, the pixel function 161 enables tracking a resolution of the image obtained of the area fraction of the medical appliances and/or a resolution (i.e., nozzle spacing) of the nozzles 42 of the printhead 44. Accordingly, the pixel function 161 facilitates scaling of the printable bitmap associated with printhead 44 relative to the image processing resolution.

In one embodiment, the centerline parameter 162 enables activation of, and control over, automatic determination of a centerline pattern of struts (or other portions) of an area fraction of the respective medical appliances 52 using the image of the medical appliances 52 obtained via imager 70 (Figure 1). Determining a centerline pattern is described later in more detail in association with Figures 3A-4C. In other embodiments, the centerline parameter 162 is adapted to determine other types of target coating patterns of an outer surface of a medical appliance, or of other three-dimensional objects that are not implantable and/or not medically related. The firing module 116 of manager 100 enables automatic control over developing a series of firing maps for an area fraction of the respective medical appliances 52. In one embodiment, as illustrated in Figure 2, the firing module 116 comprises a target point parameter 170, a minimum distance parameter 172, an election parameter 174, an exclusion parameter 176, and a tracking function 178. The target point parameter 170 enables automatic control over which image pixels correspond to a target point for ejection of a drop of coating material. The distance parameter 172 enables automatic control over a minimum distance of separation between adjacent firing points on a given pass of the printhead over an area fraction of the respective medical appliances 52. The election parameter 174 enables automatic election of possible firing points as active firing points when those firing points are spaced apart from each other by at least the minimum distance. The exclusion parameter 176 enables automatic exclusion of possible firing points that are spaced apart from each other by less than the minimum distance. In some embodiments, the tracking function 178 enables automatic tracking of the excluded firing points for reassignment as active firing points in later passes of the printhead 44. Alternatively, the excluded firing points are not tracked, and any uncoated locations are identified in later imaging steps as a new target firing point.

It is also understood that the manager 100 does not exclusively define all parameters, functions, and components of the various modules of applicator 30, as various aspects of applicator 30 are identified in association with a method of coating medical appliances, as described in association with Figures 3A- 10 and throughout the present disclosure.

Figure 3A includes an end view of one of the respective medical appliances 52 and a schematic representation of the imager 70 (Figure 1) in position to obtain an image of a top view of one of the medical appliances 52. Figure 3B is just one longitudinal segment of the top view of one of the many medical appliances 52 obtained via imager 70. Accordingly, it is understood that Figures 3A-3B are merely representative of imager 70 obtaining an image of an area fraction of all the medical appliances 52 of the array 50 of medical appliances. Figure 3 A further illustrates that the area fraction 218 corresponds to a radial sector of an outer surface 53 of the generally tubular medical appliance 52. In one aspect, the extent of the arc defining the radial sector corresponds to a pie-shaped portion (represented by angle α). Accordingly, one can effectively choose a width (W2) of the area fraction 218 (or extent of the radial sector) shown in Figure 3 B by selecting the size of the angle (α) shown in Figure 3 A. Once the angle is selected, the imager 70 automatically obtains area fractions 218 having a corresponding width (W2) to the selected angle.

As illustrated in Figure 3B, in one non-limiting example, medical appliance 52 includes a latticework or pattern 208 of struts 210. As further illustrated in Figures 3A-3B, edge lines 215 represent the lateral boundaries of the full top view of medical appliances 52 and define a full width (Wl) of the medical appliances 52. Meanwhile, demarcation lines 220 represent the lateral boundaries of an area fraction of the top view of each medical appliance 52 and define a second width (W2), which is a portion of first width (Wl). Accordingly, this second width (W2) generally defines a width of the area fraction 218.

While Figure 3 B illustrates a partial length (L2) of a medical appliance 52, it is understood that the area fraction 218 typically has a length corresponding to a full length of each respective medical appliance 52. Nevertheless, in other embodiments, an area fraction 218 could comprise a partial length of the respective medical appliances 52. Finally, because imager 70 obtains a single image including all the medical appliances 52 of the array 50, the single image includes a separate area fraction 218 for each medical appliance 52. In one aspect, the single image obtained of the area fraction of the respective medical appliances 52 comprises a two dimensional projection of a generally cylindrical member. Moreover, because just one area fraction (for all the respective medical appliances) is coated at a time, then a two dimensional coordinate system is used to control movements of the printhead 44 (in coordination with positioner 62 and controller 60) to eject drops onto desired target firing points (which are further described in association with Figures 4A- 8B). This arrangement provides a greatly simplified method of applying a coating material onto medical appliances, as compared to working in three dimensional coordinate systems for an entire surface of a medical appliance.

In one embodiment, imager 70 obtains images of various types of three- dimensional objects (other than medical appliances) for employing a method of coating to those objects according to principles of the present disclosure.

In another embodiment, imager 70 comprises more than one imaging device. In one non-limiting example, in which system 20 comprises two imagers 70, the first imager obtains a first image of a set of first three-dimensional objects with the first image limited to a first area fraction of each respective first object. The second imager obtains a second image of a set of second three- dimensional objects with the second image limited to a first area fraction of each respective second object. As later described in more detail in association with Figures 4A- 10, coating material is applied to the first area fractions of both of the respective first objects (from the first image) and the respective second objects (from the second image) in single pass or linear path of a printhead. In one embodiment, the first image is coupled to the second image to form one composite image including the first area fractions of the first objects and the first area fractions of the second appliances. The composite image excludes portions of the first and second appliances located external to the respective first area fractions. In one aspect, the set of first appliances and the set of second medical appliances are aligned generally parallel to each other along a linear path.

In one embodiment, the first image and the second image are obtained with the same imager, wherein a controlled relative motion between the imager and the array of medical appliances positions the imager for obtaining the first image separately from the first image.

In yet another embodiment, once the first image is obtained, the first area fraction of the first appliances is coated before obtaining the second image. In this embodiment, the set of first appliances have a quantity of at least two orders of magnitude.

Figure 4 A is an enlarged view of the image of area fraction 218 of the medical appliance of Figure 3B that illustrates a map 250 of pixels (schematically represented by dots 252 for illustrative clarity) defining the image of the area fraction 218. As understood by those skilled in the art, each dot 252 corresponds to just one pixel in a grid of pixels and each pixel does not generally correspond to the shape of the dot illustrated in Figure 4A. In one embodiment, the resolution of the image is on the order of 1 to 15 microns. In another aspect, the image pixel resolution is less than or equal to a size of the drops to be deposited on the medical appliance.

Using techniques known to those skilled in the art (such as contrasting techniques, edge detection techniques, skeletonization techniques, pruning techniques, etc.) the image pixels 252 are filtered to isolate those image pixels 252 corresponding to the centerline of the struts 210 of the medical appliance 52, as illustrated in Figure 4B. As shown in Figure 4B, the resulting pattern of isolated image pixels yields a pattern 260 of centerline image pixels 262 that corresponds exclusively to the centerline of the struts 210 of medical appliance 52. It is also understood that the centerline pattern 260 is not limited to the shape, size, and orientation shown in Figure 4B. Rather, the size, shape, and orientation of a Genterline pattern can vary with the size, shape, and orientation of the component members of the medical appliance to be coated.

In one aspect, the centerline pattern 260 is obtained to insure accuracy and precision in ejecting drops onto the struts 210 of the medical appliance 208. When coupled with an appropriate volume for each ejected drop, this accuracy and precision enables coating a top surface 270 of the struts 210 of medical appliance 208 without the coating material dripping onto the edges 272 of the struts 210 of the medical appliance 208.

In other embodiments in which something other than the struts of a stent are being coated, a target coating pattern is identified for that implantable medical appliance or other three-dimensional object using techniques known to those skilled in the art that are suitable for the particular target coating pattern of interest.

With the centerline pattern 260 established, each scan path of the nozzles 42 of the nozzle array 40 (Figure 1) is mapped relative to the centerline pattern 260 as illustrated in Figure 4C. In one embodiment, each scan path corresponds to one of multiple groups of nozzles. For example, as illustrated in Figure 4B₅ scan paths A₃ B, C, D, represent the path of groups A, B, C, and D of nozzles, respectively.

As illustrated in Figure 4C, each nozzle scan path intersects with at least some of the centerline image pixels 262 of centerline pattern 260 resulting in an array 280 of possible firing points 282 at which the coating material could be deposited as the printhead 44 passes over the area fraction 218 of medical appliance 52. However, in one embodiment, instead of merely ejecting the coating material onto all firing points 282 with each pass of printhead 44, coating material will be ejected onto selected firing points 282 with each pass of printhead 44. This selective firing prevents coalescence between adjacently deposited drops, as will be further described in association with Figures 5A and 5B.

In one embodiment, a large number (e.g., 100) of passes are made by printhead 44 over a first area fraction in which a first group (e.g., group A), with sufficient drying time between each pass, of nozzles is fired and then a large number of passes are made over the first area fraction by a second group (e.g. group B) of nozzles, and so on. In another embodiment, just one pass is made by printhead using a first group (e.g., group A) of nozzles before a single pass is made using a second group (e.g. group B) of nozzles, and so on. In this latter embodiment, just one pass is made before rotating to the next group of nozzles, with this rotation being automatically continued until the desired number of passes for each nozzle group is made.

In one embodiment, a diameter of a drop of coating material ejected onto a firing point (e.g., target location) is about 75 percent of the width of the strut (or other component) onto which is it deposited. This relationship insures that the drop does not seep over the edges 272 of the strut 210 but remains on the top surface 270 of the strut 210. Complete coverage of the top surface 270 of the struts 210 is provided by the overlap of subsequently ejected drops at nearby or overlapping firing points, in subsequent passes of the prϊnthead 44 (Figure 1).

In one embodiment, the methods described and illustrated in association with Figures 4A-4C, Figures 5A-5B, Figures 6-7, and Figures 8A-8B, respectively are performed using the parameters, functions, and components of application manager 100 of Figure 2 that correspond to the various aspects of the method being performed.

In another embodiment, the aspects of the method described in association with Figures 4B-4C are performed using a target coating pattern other than a centerline pattern. Accordingly, the nozzle scan paths are compared to the target coating pattern to identify image pixels that intersect with the target coating pattern, and then determine sets of target firing points based on the intersection of "target coating pattern" image pixels with the nozzle scan paths of the printhead 44. Otherwise, the aspects of the method remain generally the same.

In yet another embodiment, the aspects of the method described in association with Figures 4A-4C are also applicable to implantable medical appliances other than stents and to three dimensional objects that are not implantable and/or not medically related. In those instances, the target coating pattern is not limited to the centerline pattern.

Figures 5A and 5B schematically illustrate a firing map 290 including a centerline pattern 294 of a portion of a medical appliance (not shown) and possible firing points 296 produced via the intersection of multiple nozzle scan paths (represented by directional arrows A, B₅ C, D) for four different groups of nozzles. In order to obtain a firing pattern that will prevent coalescence of adjacently deposited drops of a coating material, certain possible firing points 296 will be excluded in at least one pass of the printhead 44 (Figure 1).

In one embodiment, a minimum distance between adjacently firing drops is established and then a radius R corresponding to that minimum distance is identified about each possible firing point 296. In one aspect, the minimum distance corresponds to the distance at which adjacent drops will not coalesce together. Next, with a pattern 297 of radii (R) mapped out for the respective possible firing points 296, any possible firing point falling within a radius of another possible firing point 296 will be excluded. For example, Figure 5A illustrates several excluded firing points (represented by blank circles 300) that fall between other adjacent firing points 296.

In one aspect, the pattern 297 of radii R act as a banishment filter in which certain possible firing points will be banished from being fired in at least one pass of printhead 44 while the remaining possible firing points 296 for a particular firing map 290 will be fired. Firing map 290 is just one of tens, hundreds, or thousands of firing maps applied in strategic sequence to deposit drops of coating material onto a medical appliance to obtain a substantially continuous and uniform coating. While each firing map varies, when all of the successive firing maps are completed all of the possible firing points corresponding to a centerline of the struts of a medical appliance will be used, thereby covering (with the coating material) substantially all exposed areas of top surface 270 (Figure 4C) of the struts 210 of the respective medical appliances 52.

In another aspect, as illustrated in Figure 5A₅ the excluded firing points 300 fall within nozzle scan paths (e.g., scan paths A or C) adjacent to other nozzle scan paths (e.g., B or D) of the active target firing points 296. However, the active firing points 296 that are adjacent to each other and falling along the same nozzle scan path (e.g., B or D) are retained because their radii R do not overlap the other respective firing point. Accordingly, multiple firing points along the same nozzle scan path are retained. This arrangement is generally a consequence of the particular geometry of the medical appliance being coated. Medical appliances having other geometries will yield differently shaped patterns of possible firing points, and therefore, different patterns of excluded firing points and of active firing points.

For example, in one non-limiting example as illustrated in Figure 5B, a firing map 320 is produced for a medical appliance 322 for which a centerline 330 already has been identified and for which possible firing points (represented by black dots 340) have been determined, in a manner substantially the same as previously described in association with Figure 5A. However, in this example, the medical appliance 322 has a different geometry than the medical appliance 290 of Figure 5A such that some possible firing points 340 along a single nozzle path, such as nozzle scan path C₅ have conflicting radii R. In other words, some of the adjacent possible firing points are close enough to each other to potentially cause coalescence. Accordingly, using the minimum distance parameter, some of these possible firing points will be excluded on a first or second pass of printhead 44 and printed in a later pass. In this manner, complete coverage will be obtained but while avoiding coalescence of adjacently deposited drops. In particular, as illustrated in Figure 5B, certain firing points will be excluded (represented by blank circles 342) which fall within the radius of adjacent possible firing points 340 at which coating will be deposited on a first pass of printhead 44. In one aspect, the particular geometry of the medical appliance 322 in which a central strut 324 extends along one of the nozzle scan paths results in several adjacent possible firing points 340 being too close to each other. Accordingly, one aspect of the present disclosure includes banishing or excluding some possible firing points 342 along a single nozzle scan path (e.g., path C in Figure 5B) as opposed to excluding some possible firing points between adjacent nozzle scan paths (e.g., paths B, C, D in Figure 5A). Moreover, some of the possible firing points 342 extending along struts

326, 327, 328, and 329 are subject to exclusion in a manner substantially the same as was demonstrated for the centerline pattern 294 for the firing map 290 illustrated in Figure 5 A.

In another embodiment, the aspects of the method described in association with Figures 5A-5B are also applicable to implantable medical appliances other than stents and to three dimensional objects that are not implantable and/or not medically related. In this instance, a target coating pattern other than the centerline pattern is used. Otherwise, the other aspects of the method remain generally the same. Figure 6 is a top view of a method 350 of applying a coating to an array

360 of medical appliances 362, according to one embodiment of the present disclosure. In one aspect, method 350 employs substantially the same features and attributes as previously described in association with Figures 1-5B. In particular, this aspect of the method includes simultaneously imaging an area fraction of each medical appliance 362 by obtaining a single image of all the medical appliances 362. After identifying a centerline of the struts 364 (or other target coating pattern) of the respective medical appliances 362 from the single image, a universe of possible firing points is established and then a series of firing maps is developed using the minimum distance parameter. In each firing map, certain firing points are excluded so that after completion of all the firing maps, the complete universe of firing points has been executed. As illustrated in Figure 6, method 350 includes moving printhead 44 including one or more rows 41 of nozzles 42 over the array 360 of medical appliances 362. In one aspect, as supported via the positioner 62 and controller 60 (Figure 1), printhead 44 travels along a path 365 enabling repeated passes over the medical appliances 362. In one non-limiting example, the array 360 includes two columns of medical appliances 362 and n number of rows of medical appliances. This configuration enables a loop shaped pattern of path 365 to move over each one of the medical appliances 362, thereby avoiding wasted motion of printhead 44 during application of the coating. Path 365 includes a first application zone (represented by dashed lines 370), a second application zone (represented by dashed lines 372), a first transition zone (represented by dashed lines 374), and a second transition zone (represented by dashed lines 376).

In another aspect, array 360 is arranged so that the longitudinal axes of the medical appliances 362 extend generally parallel to a longitudinal axis of rows 41 of nozzles 42 of printhead 44, in a manner substantially the same as the arrangement of medical appliances 52 and printhead 44 illustrated in Figure 1. However, in this embodiment, the array 360 of medical appliances 362 is arranged in two columns 380, 382. In addition, the first column 380 generally corresponds to the first application zone 370 of path 365 of printhead 44 and the second column 382 generally corresponds to the second application zone 372 of path 365 of printhead 44. Accordingly, in one complete path 365, the printhead 44 moves through first application zone 370 to partially coat the first column 380 of medical appliances 362 and through the second application zone to partially coat the first column 380 of medical appliances 362. After completing the single pass through first application zone 370, the printhead 44 is maneuvered laterally through first transition zone 374 without ejecting any coating material until the printhead 44 is positioned to travel through the second application zone 372. In each of the first and second application zones 370, 372, the printhead 44 ejects drops of coating material in successive strategic passes according to a multitude of firing maps configured to deposit the coating material (onto the area fractions 218 of the medical appliances 362) in a non-coalescing manner while achieving a final substantially uniform coating. After completing partial coating of the second column 382 of medical appliances 362, the printhead 44 is maneuvered through the second transition zone 376 to the origin 371 to ready the printhead 44 for a subsequent loop through path 365. Of course, as each subsequent loop is performed, a different firing map is executed to cover previously excluded firing points of the area fractions until all possible firing points have been executed at least once. Subsequent loops are performed as appropriate to achieve a targeted thickness of the coating material. In another aspect, the nozzles 42 of the printhead 44 are cleaned during their passage through the first and second transition zones 374, 376 to ready the nozzles 42 for ejecting drops in the next column of medical appliances 362.

Once a complete coating is obtained for a first area fraction, all of the medical appliances 362 are rotated a selected amount via rotation of the mandrels 364. In general terms, the next area fraction will overlap the first area fraction. The degree of overlap can vary, ranging from a 5 percent overlap up to a 90 percent overlap. After rotation of the mandrels 364, and consequently the medical appliances 362, to the position of the next area fraction, this area fraction of each medical appliance 362 is imaged. As in the prior iteration, a centerline is established, a universe of possible firing points is established, and then a series of firing programs is developed to enable successive passes of printhead 44 to coat this second area fraction of the medical appliances 362. Once all of the firing programs are executed for this second area fraction, drops will have been deposited in the full universe of target firing points.

This process of rotating the medical appliances 362 (via rotation of mandrels 361) a discrete amount and then coating the new area fraction via the universe of target firing points (via sequential firing programs of spaced apart deposited drops) is repeated iteratively until the complete circumference of the medical appliance has been coated.

Moreover, in some other embodiments, more than one complete circumferential cycle is performed to thicken the layer of coating material, to insure uniform coating, and/or to apply a different coating material. For example, in a first circumferential coating cycle, there can be a first degree of overlap of adjacent area fractions. In subsequent circumferential coating cycles, a lesser or greater degree of overlap is used between adjacent area fractions. Performing a second (or more) circumferential coating cycle provides the opportunity to re-image the medical appliance, one area fraction at a time, to identify any potential target firing points that were not coated on an earlier circumferential cycle.

In one embodiment, medical appliances 362 have a generally elongate shape substantially the same as medical appliances 52 shown in Figure 1, although with a different arrangement of struts or other component elements. In one aspect, each row 41 of nozzles 42 (shown in Figure 6) has a length greater than the length of each respective medical appliance 362. This arrangement simplifies coating of the respective area fractions of one column 380 of medical appliances because the printhead 44 can move along a single axis while coating those medical appliances 362.

In another aspect, row 41 includes hundreds of nozzles 42 to insure adequate deposition coverage of the coating material onto the medical appliances 362 while maintaining operational performance of the printhead 44 by providing a substantial stable of available nozzles. Figure 7 is a top view of a method 400 of applying a coating to an array

410 of medical appliances 412, according to one embodiment of the present disclosure. In one aspect, method 400 employs substantially the same features and attributes as previously described in association with Figures 1-6. However, in this instance, the array 410 is arranged so that the longitudinal axis of the rows 41 of nozzles 42 of printhead 44 is aligned to be generally perpendicular to the longitudinal axis of the medical appliances 412. In one aspect, the array 410 includes a first column 420 and a second column 422. In each respective column 420, 422 several rows 430 of medical appliances 412 are arranged in a side-by- side relationship with each row 430 of medical appliances 412 being supported on a mandrel 442. Accordingly, each row 430 of medical appliances 412 extends generally perpendicular to the longitudinal axis of the row 41 of nozzles 42 of printhead 44.

In another aspect, the medical appliances 412 in the first column 420 are side by side relative to the medical appliances 412 in the second column 422, and within each row 420 of the respective columns 420, 422, the medical appliances are arranged end-to-end on one mandrel 442 with several mandrels 442 positioned side-by-side to each other. In this instance, the area fraction for each medical appliance 412 also extends generally perpendicular to the longitudinal axis of the row 41 of nozzles 42.

In a manner substantially the same as previously described in association with Figure 6, printhead 44 is moved through the path 365 including the first application zone 372, the first transition zone 374, the second application zone 376, and the second transition zone 376 to complete a single pass over an area fraction of all the medical appliances 412 of array 410. Again, as in the method illustrated in Figure 6, an iterative process carried out in which each step of the process includes imaging an area fraction and then carrying out a selective firing program for that area fraction before rotating all the medical appliances 412 into another position for imaging and coating the next area fraction.

In one aspect, overall drying time is reduced by making many successive passes in which in each pass a set of differently positioned set of drops is deposited. In addition, by depositing drops over many medical appliances 412 in a single pass, the drops on the first medical appliance 412 are drying while other subsequent medical appliances 412 are being coated so that by the time the printhead 44 returns along path 365 to the first medical appliance 412 that was partially coated, the first set of drops are dry.

As illustrated in Figures 6 and 7, by imaging and coating one area fraction (of multiple medical appliances 362 or 412) at a time, a very large number of medical appliances (362, 412) are treated in a single batch because each medical appliance 362 or 412 is simultaneously coated with a single pass of the printhead 44. Accordingly, even though multiple passes are made on each area fraction, and each area fraction is coated separately, a high throughput rate is still achieved because the large number of medical appliances is image and coated simultaneously in concert. Moreover, precision and accuracy are maintained in this high throughput scheme because just one area fraction (of the many respective medical appliances) at a time is imaged and coated.

In another embodiment, the aspects of the method described in association with Figures 6 and 7 are performed to coat target portions of three- dimensional objects other than medical appliances.

Figure 8 A schematically illustrates a firing map 450 defined by a scan pattern of several nozzle scan paths (represented by A, B, C, D) that intersect a centerline pattern 460 of a strut (or other component) within an area fraction of a medical appliance (not shown). The intersection of each one of the respective nozzle scan paths with the centerline pattern 460 defines a target firing point 462. Accordingly, in one pass of printhead 44 (along the scan axis), coating material will be ejected onto these target firing points 462, provided that they are separated by a minimum distance to avoid the ejected drops from coalescing. In one aspect, the nozzles groups are selected to maintain this minimum distance of separation between adjacently ejected drops of coating material. However, if necessary, some of the target firing points are excluded from a first pass of the printhead to avoid coalescence and are printed on a subsequent pass of printhead 44.

As illustrated in Figure 8A, several centerline image pixels 462 fall intermediate between adjacent nozzle scan paths and therefore between adjacent target firing points 462 for the first position of the printhead 44. For example, Figure 8A illustrates four target firing points 464 (for each strut of the medical appliance) that lay intermediate to the target firing points intersecting the nozzles scan paths for nozzle one (Group A) and nozzle two (Group B). Accordingly, in order to eject coating material onto these currently intermediate centerline images pixels 464, positioner 62 is used to shift the printhead 44 over a small distance to realign the nozzles scan paths to intersect with some of these intermediate centerline image pixels 464, as illustrated in Figure 8B. This realignment will be generally referred to as shifting the nozzle scan paths. Accordingly, a new firing program is provided with the new target firing points 466 positioned intermediate to the target firing points 462 of the preceding firing program. In this manner, the method and system of the present disclosure deposits coating material onto some of the previously excluded target firing points 464. This shifting process is repeated iteratively to account for all of the target firing points intermediate to the first or original nozzle scan paths until a full universe of target firing points corresponding to all of the centerline image pixels 461 is executed. In one embodiment, this shifting process is executed until the full universe of target firing points (along the centerline pattern 460) is coated within a single area fraction prior to rotation of the medical appliances (via rotation of the mandrels) to a subsequent area fraction. In another embodiment, this shifting process is executed so that just some of the target firing points (of the full universe of target firing points) are coated within an area fraction prior to rotation of the medical appliances (via rotation of the mandrels) to a subsequent area fraction. In this latter embodiment, any non-coated firing points will be identified and coated in a subsequent imaging and coating of area fractions as successive circumferential coating passes are made about the respective medical appliances.

In another embodiment, the aspects of the method described in association with Figures 8A-8B are also applicable to implantable medical appliances other than stents and to three dimensional objects that are not implantable and/or not medically related. In this instance, a target coating pattern other than the centerline pattern is used. Otherwise, the other aspects of the method remain generally the same. Figure 9 is a flow diagram illustrating a method 500 of applying a coating to an array of medical appliances. In one embodiment, method 500 is performed using any one or more of the systems and methods previously described in association with Figures 1-8B. As illustrated in Figure 9, method 500 comprises obtaining a single image of an array of medical appliances with the single image limited to an area fraction of each respective appliance, as illustrated at block 502 in Figure 9. At block 504, each respective area fraction is coated one at a time. In one aspect, the method includes isolating the image pixels that correspond to a centerline of each strut (or other component) of each respective medical appliance, as illustrated at block 506. In one embodiment, a centerline pattern of the respective struts of the medical appliance is identified prior to isolating the centerline image pixels. In one aspect, after identifying the centerline pattern a bitmap of the image is expanded so that a later set of firing points is at a higher resolution than the resolution of the nozzles of the printhead or the original captured image. This arrangement also increases the accuracy of determining the centerline pattern, which facilitates locating firing points at the centerline of a strut of an appliance to prevent seepage of the coating material onto the edges of the strut.

At block 508, a universe of target firing points for the area fraction is determined based on an intersection of the isolated centerline image pixels with a set of nozzle scan paths of an array of nozzles of a single printhead. In some embodiments as illustrated at block 510, determining the target firing points further includes electing a subset of the target firing points within an area fraction by temporarily excluding target firing points that are not separated by a minimum distance. In other words, the elected target firing points are separated from each other by a minimum distance. This minimum separation distance acts to prevent coalescence between adjacently deposited drops of coating material. Any temporarily excluded target firing points become elected for deposition in one or more of latter passes of the array of nozzles over this area fraction of the respective medical appliances. As illustrated at block 512, the method further includes moving the single printhead in a first linear path over all the medical appliances to eject drops of a coating material, via the array of nozzles, at the target firing points.

In one embodiment, as illustrated at block 514, on each pass of the single printhead, the ejection of drops is limited to the elected firing points that intersect with nozzle scan paths of the array of nozzles. Any elected firing points that are not coated in a first pass, become coated in subsequent passes of the single printhead over that area fraction of the respective medical appliances.

Figure 10 is a flow diagram illustrating a method 600 of applying a coating to a medical appliance, according to one embodiment of the present disclosure. In one embodiment, the method 550 is performed using any one or more the systems, components, or methods previously described in association with Figures 1-9. For instance, in this method, it is understood that a single image has been obtained of an area fraction of an array of medical appliances in a manner consistent with the methods and systems previously described in association with Figures 1-9.

As illustrated at block 602 in Figure 10, the method 600 includes choosing rows of image pixels that align with nozzle scan paths according to a generally uniform spacing between adjacent nozzles of a row of nozzles. At block 604, the nozzles are apportioned into a repeating pattern of n groups so that members of each group are spaced apart by the minimum distance. The method further includes creating n firing programs with one firing program being uniquely associated with each nozzle group, as illustrated at block 606. At block 608, each of the n firing programs are executed (i.e., drops are ejected onto the respective target firing points) separately m times while providing sufficient drying time between successive passes. In one aspect, each drop comprises a volume less than the final desired coating volume for each target firing point so that upon depositing multiple drops at that target firing point, the final desired coating volume is achieved. This aspect of depositing several drops in successive steps, with sufficient drying time between each drop, enables the coating to uniformly cover the top surface of the struts of the medical appliances without seeping or spilling over the edge of the struts. In this aspect, each successive drop onto the same firing point slightly increases the diameter or covered area at the target firing point.

At decision point 610, a query is performed to determine if there are any remaining temporarily excluded target firing points. If the answer is affirmative, then the method proceeds to block 522 at which the array of nozzles is shifted to enable depositing coating material onto previously excluded target firing points. The shifting is generally executed in a manner substantially the same as previously described in association with Figures 8A-8B. This process of imaging and coating an area fraction, followed by shifting the array of nozzles before making another pass of the nozzles over that area fraction to cover previously excluded firing points, is repeated until all the target firing points along a centerline pattern are coated. At this point, as illustrated at block 614, all of the stents or medical appliances are rotated to provide the next area fraction for imaging and coating according to the process illustrated by blocks 602-612. In one aspect, the next area fraction overlaps the prior area fraction. Finally, the entire process illustrated via blocks 602-614 is executed until one or more complete circumferential coating cycles about the respective medical appliances is executed.

In another embodiment, the aspects of the method described in association with Figures 9-10 are also applicable to implantable medical appliances other than stents and to three dimensional objects that are not implantable and/or not medically related. In this instance, a target coating pattern other than the centerline pattern is used. Otherwise, the other aspects of the method remain generally the same. Figure 11 is a diagram illustrating a method 650 of coating a three- dimensional object, according to one embodiment of the present disclosure. In one embodiment, in a manner substantially the same as the methods and systems previously described in association with Figures 1-10, a substantially continuous coating is applied to an outer surface of a three-dimensional object, such as an implantable medical appliance.

In one aspect, the substantially continuous coating is applied to one or more isolated target portions of the outer surface of the object. With this in mind, Figure 11 illustrates a three-dimensional object 660 having an outer surface 662. In one embodiment, the target portion comprises islands 664 of coating material located on the outer surface 662.

In one embodiment, the target portion comprises an interrupted stripe pattern 670 (including spaced apart individual segments 672) of coating material located on the outer surface 662. In another embodiment, the striped pattern 670 is formed as a contiguous stripe (i.e., not having interrupted, spaced apart segments) that extends about the circumference of the object 660.

In yet another embodiment, the target portion comprises a more complex coating pattern 680 of coating material. In one non-limiting example, the complex coating pattern defines an H-shaped pattern as illustrated in Figure 11.

In each case, the coating material is substantially continuous for the target portion of the object that is coated and no coating material is present on the portions of the object surrounding the target portions. Accordingly, the coating is substantially continuous as to the target portions but non-continuous as to the entire outer surface of the object 660.

Moreover, in one embodiments,_the target coating pattern for an object is limited to one type of coating pattern (e.g., stripes) while in other embodiments, the target coating pattern for an object includes several different types of coating patterns.

In one aspect, as illustrated in Figure 11, the target coating pattern is limited to a portion of the object rather than covering the entire object. With this in mind, the area fractions in the region of the target coating pattern are identified. Images are obtained, one-at-a-time, of the respective identified area fractions with each area fraction being coated prior to obtaining an image of the next area fraction. This process is repeated until coating material is applied to the target coating pattern. Accordingly, as in the other embodiments, additional images of the object are not obtained for successive area fractions until the area fraction corresponding to the first area fraction is coated. However, because the target coating pattern comprises less than the entire outer surface of the object, the method also employs rotational mechanism 58 (Figure 1) to rotate objects into positions in which each image that is obtained will include at least some part of the target coating pattern. Likewise, rotational mechanism 58 will maneuver the objects so that imager 70 avoids imaging area fractions in which no portion of the target coating pattern is present, thereby avoiding the coating of non-target portions of the objects. In one embodiment, the three-dimensional object 660 illustrated in

Figure 11 comprises an implantable medical appliance while in other embodiments, the three-dimensional object 660 comprises a non-medical, non- implantable article. Moreover, while object 660 is illustrated as a generally tubular member, in other embodiments object 660 comprises other three- dimensional shapes.

Embodiments of the present disclosure enable accurate, high throughput coating of implantable medical appliances as well as other three-dimensional objects. These embodiments treat one area fraction of an array of appliances at a time by obtaining a single image of the respective area fractions, applying image processing tools to the single image to develop a firing map, and then using a single pass of a printhead to eject drops of coating material onto each area fraction of the respective medical appliances according to the firing map. Repeated passes are made to insure deposition of drops at all of the locations of the firing map. This process is repeated iteratively until the entire top surface of each medical appliance is uniformly coated, resulting in high speed treatment of a large number of medical appliances without sacrificing accuracy of the deposited drops onto the top surface.

Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

WHAT IS CLAIMED IS:

1. A method of coating an implantable medical appliance, the method comprising: obtaining an image of an array of implantable medical appliances, the image limited to a first area fraction of each respective appliance; applying a coating on the respective first area fractions via: isolating pixels of each first area fraction corresponding to a target coating pattern of each appliance; determining a first set of firing points based on intersection of the isolated pixels with a scan path of each nozzle of an array of nozzles of a printhead; and moving the printhead in a first linear path over all of the respective appliances to eject drops of a coating material onto the first area fractions, via the array of nozzles, at the first set of firing points.

2. The method of claim 1 wherein each respective implantable medical appliance comprises a stent including a network of struts, wherein the target coating pattern comprises a centerline pattern of each strut of the network of struts of each respective stent, and wherein applying the coating comprises applying a substantially continuous coating that is limited to a portion of each respective appliance that corresponds to the first set of firing points.

3. The method of claim 1 wherein the array of nozzles includes a quantity of nozzles having at least two orders of magnitude.

4. The method of claim 1 , comprising: arranging the array of appliances to include a quantity of appliances of at least two orders of magnitude.

5. The method of claim 1 wherein a longitudinal axis of the array of nozzles is aligned generally perpendicular to a longitudinal axis of each appliance, and arranging the array of appliances in an array of rows and columns, each row including a side-by-side arrangement of the appliances and each column including an end-to-end arrangement of the appliances.

6. The method of claim 1, comprising: arranging the array of appliances in a first column in a side-by-side relationship to align a longitudinal axis of the array of nozzles to be generally parallel to a longitudinal axis of each appliance of the first column, wherein a length of the array of nozzles is at least coextensive with a length of the respective appliances.

7. The method of claim 6, comprising: arranging the array of appliances to further include a second column of appliances in a side-by-side relationship to align the longitudinal axis of the array of nozzles to be generally parallel to a longitudinal axis of each appliance of the second column; and arranging the linear firing path to include a loop pattern comprising a first firing zone, in a first direction, over the first column of appliances and a second firing zone, in a second direction opposite the first direction, over the second column of appliances.

8. The method of claim 7, comprising: arranging the loop pattern to include a first transition zone between the first firing zone and the second firing zone to move the printhead from alignment with the first column into alignment with the second column and a second transition zone between the second firing zone and the first firing zone to move the printhead from alignment with the second column into alignment with the first column, wherein the first and second transition zones are spaced apart from each other at opposite ends of the array of appliances to extend generally perpendicular to the first and second directions, wherein firing of the respective nozzles is omitted in the respective first and second transition zones; and performing repeating cycles of the loop pattern.

9. The method of claim 1 , comprising: designating the nozzles into n groups of nozzles, with each group corresponding to a subset of nozzles spaced apart by n nozzles, wherein firing includes iteratively firing each one of the n groups in sequence, one at a time, until all n groups of nozzle have been fired onto the firing points of the appliance, further wherein the firing includes firing coating material simultaneously from every nozzle of the selected group at the firing points within a path of the respective nozzles of the selected group.

10. The method of claim 1, comprising: shifting the printhead, laterally in a direction generally parallel to a longitudinal axis of the array of nozzles, across the area fraction by a distance less than a spacing between adjacent nozzles to define a second linear path generally parallel to the first linear path; determining a second set of firing points based on an intersection of the isolated pixels with a scan path of each nozzle of the array of nozzles according to the second linear path; and moving the printhead in the second linear path over all of the respective appliances to fire drops of the coating material, via the array of nozzles, at the second set of firing points onto the respective area fractions of the appliances.

11. The method of claim 1 , comprising: rotating the array of appliances; obtaining a second image of the array of appliances, the second image limited to a second area fraction of each respective appliance, the second area fraction overlapping the first area fraction; producing a coating on the respective second area fractions via: isolating image pixels of each second area fraction that corresponds to a target coating pattern of each appliance; determining a second set of firing points based on an intersection of the isolated image pixels of the respective second area fractions with the scan path of each nozzle of the array of nozzles; and moving the printhead in the first linear path over all of the respective appliances to fire drops of the coating material onto the second area fractions, via the array of nozzles, at the second set of firing points.

12. The method of claim 1, comprising: moving the printhead in multiple passes over all of the respective appliances to fire drops of the coating material, via the array of nozzles, at the firing points of each appliance wherein upon each pass a different subset of the array of nozzles is fired simultaneously, the respective subset selected to provide sufficient spacing between adjacent fired nozzles to prevent coalescence of fired drops on an outer surface of each respective appliance.

13. The method of claim 1 wherein obtaining the image of the array of appliances comprises: obtaining a first image of a set of first implantable medical appliances with the first image limited to the first area fraction of each respective first appliance; and obtaining a second image of a set of second implantable medical appliances with the second image limited to the first area fraction of each respective second appliance, wherein applying the coating on the respective first area fractions includes applying the coating to the first area fractions of both of the respective first appliances and the respective second appliances in the first linear path, and wherein the set of first medical appliances and the set of second medical appliances are aligned generally parallel to each other along the first linear path.

14. A system for coating an array of three-dimensional articles, the system comprising: an imager configured to obtain a single image of a first area fraction of each article of the array of articles; a printhead including at least one row of nozzles; a positioner coupled to the printhead and configured to move the at least one row of nozzles in a linear path over the array of the articles; and an application manager including; a target coating pattern parameter configured to identify a target coating pattern of image pixels on a top surface of the respective articles within the first area fraction; and a firing map module configured to identify target firing points defined by an intersection of scan paths of the respective nozzles and the target coating pattern image pixels.

15. The system of claim 14 wherein each three-dimensional article comprises an implantable medical appliance.

16. The system of claim 15 wherein the firing map module includes a minimum distance parameter configured to specify a minimum distance between adjacent target firing points, wherein the firing map module is configured elect target firing points that are spaced apart by at least the minimum distance and to exclude from the firing map other target firing points that are separated from elected target firing points by a distance less than the minimum distance.

17. The system of claim 16 wherein the firing map module is configured to elect the previously excluded target firing points for inclusion into a subsequent firing map as elected target firing points.

18. The system of claim 15 wherein the printhead module of the manager includes a shift parameter configured to cause shifting a position of the printhead to re-align the nozzle scan paths with the target coating pattern image pixels, in cooperation with the firing map module, to identify a second set of target firing points different than the first set of target firing points, wherein the respective target firing points of the second set are disposed intermediate to the respective target firing points of the first set.

19. The system of claim 15 wherein firing manager includes a printhead module configured to apportion the respective nozzles into n groups of nozzles wherein each group is defined by nozzles that are spaced apart from each other by n-1 nozzles, wherein the firing map module is further configured to direct ejection of drops of coating material via one group at a time for each pass of the printhead over the array of the objects until drops have been ejected onto the first area fraction from all n groups.

20. The system of claim 19, comprising: a rotational mechanism configured to rotate all of the objects a predetermined degree of rotation to provide a second area fraction that overlaps the first area fraction.

21. The system of claim 20 wherein the at least one row of nozzles has a length greater than a length of the articles, and the at least one row of nozzles has a quantity of nozzles of at least two orders of magnitude, and the array of articles includes a quantity of articles of at least two orders of magnitude.

22. A method of coating a three-dimensional object comprising: imaging an area fraction of the object; producing a two-dimensional bitmap representative of the area fraction; printing material, prior to obtaining additional images of the object, via a drop on demand fluid ejection device onto the object at the area fraction; and repeating the method for successive area fractions of the object until the material is printed onto a targeted area of the object.

23. The method of claim 22 wherein the three-dimensional object includes a plurality of implantable medical appliances, and wherein a quantity of the respective appliances is at least two orders of magnitude.

24. The method of claim 23 wherein each respective appliance comprises a generally tubular stent and the area fraction comprises a radial sector of an outer surface of the stent, wherein the radial sector comprises less than a 180 degree arc of the outer surface of the stent, and wherein the successive area fractions overlap each other.

25. The method of claim 22 wherein the targeted area comprises at least one isolated area of an outer surface of the object, and wherein printing the material comprises limiting application of a substantially continuous coating of the material to the at least one isolated area.