Hollow microneedle arrays

1. A method comprising:

displacing a microneedle array in a direction perpendicular to a first major surface of an applicator, wherein the first major surface of the applicator comprises the microneedle array;

opening an openable end of a drug cartridge;

establishing fluid communication between the openable end and the microneedle array; and

forcing fluid from the drug cartridge into the microneedle array through the openable end; wherein the drug cartridge, the applicator, and the microneedle array are components of an apparatus further comprising:

a housing;

the drug cartridge, the drug cartridge comprising a tubular member, a piston movable within the tubular member, and a fluid, wherein the drug cartridge has the openable end sealed by a septum and the piston is in sliding and sealing relationship with interior walls of the tubular member;

a manifold carrier fixedly attached to the microneedle array;

a pathway communicable between the openable end and the microneedle array, the pathway passing through the manifold carrier;

the housing supporting the applicator and the drug cartridge;

a first stored energy device actuatable for applying force to the applicator to accelerate the applicator in a direction generally normal to the first major surface; and

a second stored energy device actuatable for automatically opening the openable end, such that the openable end and the pathway are in fluid communication, and wherein the second stored energy device includes a spring member that moves the piston relative to the housing so that the actuated second stored energy device forces the fluid through the openable end, the pathway, and the microneedle array; and

wherein the housing includes an actuator for actuating the first and second stored energy devices.

2. The method of claim 1 , wherein the microneedle array includes an array of hollow microneedles.

3. The method of claim 2 , wherein the first stored energy device drives the array of hollow microneedles at a velocity ranging from between about 2 and 20 m/sec.

4. The method of claim 2 , wherein the first stored energy device is supported on the applicator so that upon full release of the first stored energy device the first stored energy device decouples therefrom and is allowed to freely recoil and vibrate.

5. The method of claim 2 , wherein the housing includes a portion thereof that restrains movement of the applicator, thereby minimizing recoil and retraction of the array of hollow microneedles upon full release of the first stored energy device.

6. The method of claim 2 , wherein the first stored energy device continuously maintains positive pressure on the applicator upon full release of the first stored energy device.

7. The method of claim 2 , wherein the hollow microneedles of the array of hollow microneedles have a length of from about 500 μm to about 1000 μm.

8. The method of claim 1 , wherein the first stored energy device comprises a spring that has leg portions that straddle the drug cartridge, and a portion that contacts the applicator and the spring has a generally U-shape, and when unstressed lies adjacent the drug cartridge and generally parallel to a longitudinal axis of the drug cartridge.

9. The method of claim 1 , wherein the drug cartridge is removably replaceable in the housing.

10. The method of claim 1 , wherein the applicator includes a piercing needle operable to penetrate the septum.

11. The method of claim 1 , wherein the second stored energy device automatically displaces the drug cartridge along an axis generally parallel to the first major surface.

12. The method of claim 1 , wherein the second stored energy device includes first and second spring members, wherein the first spring member moves the drug cartridge to open the openable end, and the second spring member moves the piston to force the fluid from the drug cartridge when the openable end is opened.

13. The method of claim 1 , wherein the applicator is releasably held in a primed condition by a releasable latching mechanism cooperating with the first stored energy device.

14. The method of claim 1 , wherein the applicator comprises a releasable adhesive layer.