Process and apparatus for inspecting microneedle arrays

1. A process of making a microneedle array comprising:

providing a microneedle array having a plurality of microneedles of a desired shape;

illuminating at least a portion of said microneedle array that comprises at least one microneedle;

capturing an observed image of said at least one microneedle using an optical device, wherein the observed image is at least one shadow projected onto a surface of the microneedle array from the at least one microneedle;

electronically processing said observed image and determining at least one shape parameter for said at least one microneedle based upon the processed observed image;

accepting said microneedle array if said at least one shape parameter is within an acceptable range;

thereby providing a microneedle array that comprises a known shape of the plurality of microneedles.

2. The process of claim 1 , wherein said at least one microneedle is coated with a material.

3. The process of claim 2 , further comprising determining an amount of material on said at least one microneedle.

4. The process of claim 3 , wherein the step of determining an amount of material on said at least one microneedle further comprises;

defining a coated region from a shadow of an individual microneedle;

rotating a two-dimensional profile of the coated region around a microneedle tip's central axis to form a solid of revolution;

calculating an amount of a first material comprising the solid of revolution;

calculating an amount of a second material comprising an underlying microneedle structure for the coated region;

subtracting the amount of the second material from the first material;

thereby determining the amount of said material on said at least one microneedle.

5. The process of claim 1 , wherein the step of illuminating further comprises illuminating with a directed light source.

6. The process of claim 5 , wherein the light source projects light through the microneedle array at an acute angle of between about 10° and 75° to a surface of the microneedle array.

7. The process of claim 1 , wherein said shadows from said at least one microneedle do not project onto neighboring microneedles.

8. The process of claim 1 , wherein the optical device comprises a 2D array camera.

9. The process of claim 1 , wherein the optical device comprises a 1D linescan camera.

10. The process of claim 1 , wherein the optical device is positioned above the microneedle array and a linear line from the optical device through the microneedle array is normal to the array.

11. The process of claim 1 , wherein the step of electronically processing said observed image and determining shape parameter further comprises calculating the difference between a theoretical shape of an individual microneedle and an observed shape of the individual microneedle.

12. The process of claim 1 , wherein the observed image is an 8-bit to 16-bit grayscale image comprising said at least one microneedle with at least one microneedle shadow projected on a surface of the microneedle array.

13. The process of claim 12 , further comprising horizontally flat-fielding the observed image to account for variable background intensity.

14. The process of claim 12 , further comprising a binary threshold which segments the plurality of microneedle shadows from said surface on the microneedle array.

15. The process of claim 12 , further comprising a blob extraction algorithm to isolate an individual microneedle shadow.

16. The process of claim 1 , wherein the shape parameter is at least one of microneedle height, width, angle, spacing, base area, or combinations thereof.

17. A process of inspecting a microneedle array comprising:

illuminating at least a portion of a microneedle array that comprises at least one coated microneedle with a directed light source;

capturing an observed image of said at least one coated microneedle using an optical device, wherein the observed image is at least one shadow projected onto a surface of the microneedle array from the at least one coated microneedle;

electronically processing said observed image; and

determining an amount of a material coating on said at least one coated microneedle.

18. The process of claim 17 , wherein the light source projects light through the microneedle array at an acute angle of between about 10° and 75° to a surface of the microneedle array.

19. The process of claim 17 , wherein determining the amount of material on the at least one coated microneedle further comprises:

defining a coated region from a shadow of an individual microneedle;

rotating a two-dimensional profile of the coated region around a microneedle tip's central axis to form a solid of revolution;

calculating an amount of a first material comprising the solid of revolution;

calculating an amount of a second material comprising an underlying microneedle structure for the coated region;

subtracting the amount of the second material from the first material;

thereby determining the amount of the material on the at least one coated microneedle.