Low-friction rolling plunger for a wearable drug delivery device

1. A reservoir/pump mechanism comprising:

a rigid structure having an open end and a closed-end defining a fluid port;

a flexible sheet attached to an inner surface of the rigid structure;

a plunger, disposed in the open end of the rigid structure;

a motor; and

a linkage connected to the motor and configured to cause a linear translation of the plunger within the rigid structure, the linkage comprising:

a leadscrew rotationally driven by the motor; and

a drive nut coupled to the leadscrew such that rotation of the leadscrew causes a linear translation of the drive nut, wherein the drive nut is coupled to the plunger.

2. The mechanism of claim 1 wherein the flexible sheet is bonded to a head portion of the plunger.

3. The mechanism of claim 1 wherein movement of the plunger toward the closed end of the rigid structure causes the formation of a rolled corner of the flexible sheet between the head portion of the plunger and the inner surface of the rigid structure.

4. The mechanism of claim 1 wherein the rigid structure comprises:

a first portion defining the closed end of the rigid structure;

a second portion defining the open end of the rigid structure;

wherein the flexible sheet is attached to an inner surface of the rigid structure by being clamped between the first portion of the second portion when the first portion and second portion are joined together to form the rigid structure.

5. The mechanism of claim 4 wherein the first portion has a cross-sectional area smaller than the second portion such as to form a shoulder within the rigid structure that extends from an attachment point of the flexible sheet to the closed end of the rigid structure.

6. The mechanism of claim 1 wherein the flexible sheet has a high tensile modulus such as to minimize the stretchability of the flexible sheet.

7. The mechanism of claim 1 wherein the flexible sheet is attached to the inner surface of the rigid structure at the closed end of the rigid structure.

8. The mechanism of claim 1 wherein the flexible sheet forms a fluid barrier between an interior of the rigid structure and the plunger, thereby forming a pump chamber within the rigid structure which is only in fluid communication with the fluid port.

9. The mechanism of claim 8 wherein the plunger is able to be linearly translated within the rigid structure in a first direction toward the closed end of the rigid structure and in a second direction toward the open end of the rigid structure.

10. The mechanism of claim 9 wherein a linear translation of the plunger toward the closed end of the rigid structure forces a fluid contained in the pump chamber out of the rigid structure via the fluid port.

11. The mechanism of claim 9 wherein linear translation of the plunger toward the open end of the rigid structure causes a suction within the pump chamber to draw a fluid into the pump chamber.

12. The mechanism of claim 1 wherein the rigid structure defines a slot therein extending from the open end of the rigid structure to a point wherein the flexible sheet is attached to the inner surface of the rigid structure, the slot allowing passage of the linkage therethrough.

13. The mechanism of claim 8 wherein the rigid structure further defines an inlet port in fluid communication with the pump chamber and with a reservoir containing a fluid, such that a linear translation of the plunger toward the open end of the rigid structure causes a suction within the pump chamber to draw the fluid from the reservoir into the pump chamber.

14. The mechanism of claim 1 , wherein the leadscrew extends at most 50% longer than a length of the rigid structure.

15. A wearable drug delivery device, comprising:

the mechanism of claim 1 ; and

an adhesive configured to affix the wearable drug delivery device to a skin of a user.