Transdermal fluid delivery device

1. A transdermal fluid delivery device positionable on a patient's epidermis for delivering fluid into the patient's bloodstream, comprising:

a housing defining a longitudinal axis and having a proximal end and a distal end, the housing defining a passageway extending longitudinally therethrough and including a helical cam track disposed on an inner surface of the housing;

a fluid reservoir positionable within the passageway of the housing, the fluid reservoir adapted for retaining a fluid therein;

a base member positioned at the distal end of the housing; and

a microneedle assembly coupled to the fluid reservoir, the microneedle assembly including a hub and a plurality of microneedles extending distally from the hub, the hub including at least one protrusion extending outwardly therefrom that is engaged within the helical cam track, each microneedle of the plurality of microneedles including a lumen defined therethrough in communication with the fluid reservoir,

wherein rotation of the housing with respect to the microneedle assembly about the longitudinal axis of the housing in a first direction urges the at least one protrusion to move along the helical cam track, thereby translating the microneedle assembly longitudinally with respect to the housing from a retracted position, wherein the plurality of microneedles are disposed within the base member, to an extended position, wherein the plurality of microneedles are advanced distally to penetrate the base member and extend distally therefrom for puncturing the patient's epidermis and delivering the fluid into the patient's bloodstream, and

wherein rotation of the housing with respect to the microneedle assembly about the longitudinal axis of the housing in a second, opposite direction urges the at least one protrusion to move along the helical cam track, thereby translating the microneedle assembly longitudinally with respect to the housing from the extended position to the retracted position.

2. The transdermal fluid delivery device according to claim 1 , further comprising a latching mechanism for retaining the microneedle assembly in at least one of the retracted position and the extended position.

3. The transdermal fluid delivery device according to claim 1 , wherein the microneedle assembly is biased toward the retracted position.

4. The transdermal fluid delivery device according to claim 1 , wherein the microneedle assembly includes a first latch member and wherein the housing includes a second, complementary latch member such that, upon movement of the microneedle assembly to the extended position, the first and second latch members engage one another to retain the microneedle assembly in the extended position.

5. The transdermal fluid delivery device according to claim 4 , wherein at least one of the first and second latch members defines a pre-determined latching period, the at least one latch member configured to disengage the other latch member at the end of the pre-determined latching period to return the microneedle assembly under bias back towards the retracted position.

6. The transdermal fluid delivery device according to claim 1 , further comprising a skin adhesive disposed on a distal surface of the base member for adhering the base member to the patient's epidermis.

7. The transdermal fluid delivery device according to claim 6 , further comprising a peelable cover disposed about the skin adhesive to inhibit adhesion prior to removal of the peelable cover.

8. The transdermal fluid delivery device according to claim 1 , wherein, in the extended position, the plurality of microneedles extend distally from the base member by about 2 mm to about 3 mm.

9. The transdermal fluid delivery device according to claim 1 , wherein each microneedle of the plurality of microneedles includes a pointed distal end to facilitate at least one of penetrating the base member and puncturing the patient's epidermis.