Method of contact coating a microneedle array

1. A method of coating a microneedle array comprising:

providing a microneedle array having a substrate and a plurality of microneedles;

applying a coating solution comprising a carrier fluid and a coating material onto a first major surface of a flexible film;

performing a transfer step of bringing the first major surface of the flexible film into contact with the microneedles and removing the flexible film from contact with the microneedles, wherein at least a portion of the coating solution is transferred to the microneedle array during the transfer step, and wherein the flexible film is moved in a linear direction across the microneedles while the coating solution on the first major surface of the flexible film is in contact with the microneedles; and

allowing the carrier fluid to evaporate to leave a dried coating on the microneedle array.

2. A method as claimed in claim 1 , wherein the flexible film and the microneedle array define an angle of flexure during the transfer step that is between 0 and 90 degrees.

3. A method as claimed in claim 2 wherein the angle of flexure is between 5 and 15 degrees.

4. A method as claimed in claim 1 wherein the linear direction is selected from the group consisting of generally parallel to the plane of the microneedle array and generally perpendicular to the plane of the microneedle array.

5. A method as claimed in claim 1 wherein more than one transfer step is performed.

6. A method as claimed in claim 4 wherein more than one transfer step is performed and in between repeated transfer steps the microneedle array is rotated with respect to the flexible film in a plane generally parallel to the plane of the microneedle array substrate.

7. A method as claimed in claim 1 wherein the amount of coating solution transferred to the microneedles during a transfer step is between 0.1 μL and 10 μL.

8. A method as claimed in claim 1 wherein more than 50% by weight of the dried coating applied to the microneedle array is present on the needles.

9. A method as claimed in claim 1 wherein the dried coating material is preferentially deposited onto the microneedles.

10. A method as claimed in claim 1 wherein the dried coating material is preferentially deposited onto the upper half of the microneedles.

11. A method as claimed in claim 1 wherein the coating solution comprises a therapeutic agent.

12. A method as claimed in claim 11 wherein the therapeutic agent is present in the coating solution as a dispersed or suspended material.

13. A method as claimed in claim 1 wherein the coating solution comprises water.

14. A method as claimed in claim 1 wherein the coating solution comprises a vaccine, vaccine adjuvant, or mixture thereof.

15. A method as claimed in claim 1 wherein the surface of the microneedles is hydrophilic.

16. A method as claimed in claim 1 wherein the surface of the microneedles is coated with a thin film of diamond-like glass.

17. A method of coating a microneedle array comprising:

providing a microneedle array having a substrate and a plurality of microneedles;

applying a coating solution comprising a carrier fluid and a coating material onto a first major surface of a flexible film;

performing a transfer step of bringing the first ma or surface of the flexible film into contact with the microneedles and removing the flexible film from contact with the microneedles, wherein at least a portion of the coating solution is transferred to the microneedle array during the transfer step, and wherein the flexible film and the microneedle array define an angle of flexure during the transfer step that is between 5 and 15 degrees; and

allowing the carrier fluid to evaporate.

18. A method of coating a microneedle array comprising:

providing a microneedle array having a substrate and a plurality of microneedles, wherein the surface of the microneedles is coated with a thin film of diamond-like glass;

applying a coating solution comprising a carrier fluid and a coating material onto a first major surface of a flexible film;

performing a transfer step of bringing the first ma or surface of the flexible film into contact with the microneedles and removing the flexible film from contact with the microneedles, wherein at least a portion of the coating solution is transferred to the microneedle array during the transfer step; and

allowing the carrier fluid to evaporate.

19. A method of coating a microneedle array comprising:

providing a microneedle array having a substrate and a plurality of microneedles;

providing a coating solution comprising a carrier fluid and a coating material;

providing a coating apparatus comprising a coating substrate and a supporting member for the microneedle array, wherein at least one of the coating substrate and the microneedle array is flexibly mounted within the coating apparatus;

applying the coating solution onto a first major surface of the coating substrate to form a layer of applied coating solution having a thickness equal to or less than the height of at least one of the microneedles, wherein the coating solution is applied to the first major surface of the coating substrate with a pickup plate or an extrusion die;

performing a transfer step of bringing the first major surface of the coating substrate into contact with the microneedles and removing the coating substrate from contact with the microneedles, thereby transferring at least a portion of the coating solution to the microneedle array; and

allowing the transferred carrier fluid to evaporate.

20. A method as claimed in claim 19 wherein the coating substrate is flexibly mounted.

21. A method as claimed in claim 20 wherein the coating substrate is a flexible film.

22. A method as claimed in claim 21 wherein the first major surface of the coating substrate has a leading edge and a trailing edge and wherein the trailing edge of the flexible film is brought into contact with the microneedles during the transfer step.

23. A method as claimed in claim 21 wherein the microneedle array is oriented so that the microneedles are facing upward and the coating solution on the flexible film is facing downwards when it is brought into contact with the microneedles.

24. A method as claimed in claim 19 wherein the microneedle array is flexibly mounted.

25. A method as claimed in claim 24 wherein the coating substrate is a fixed surface.

26. A method as claimed in claim 25 wherein an excess of coating solution is applied to the coating substrate and a doctoring step is performed to provide the layer of applied coating solution having a thickness equal to or less than the height of at least one of the microneedles.

27. A method as claimed in claim 24 wherein the coating substrate is flexibly mounted.

28. A method as claimed in claim 19 wherein at least a portion of the first major surface of the coating substrate is hydrophilic.

29. A method as claimed in claim 19 wherein the entire portion of the first major surface of the coating substrate is hydrophilic.