Method of fabricating microneedles

1. A method of fabricating a microneedle, said method comprising the steps of:

(a) providing a substrate;

(b) forming a metal-containing seed layer on the top surface of the substrate;

(c) forming a nonconductive pattern on a portion of the seed layer;

(d) plating a first metal layer on the seed layer and over the edge of the nonconductive pattern to create a micromold with an opening that exposes a portion of the nonconductive pattern;

(e) plating a second metal onto the micromold to form a microneedle in the opening;

(f) separating the micromold with the microneedle formed therein from the seed layer and the nonconductive pattern; and

(g) selectively etching the micromold to release the microneedle.

2. The method as recited in claim 1 , wherein the plating in step (e) is carried out until the second metal fills the opening, thereby forming a solid microneedle.

3. The method as recited in claim 1 , wherein the plating in step (e) forms a metal coating on the sidewall surface of the opening, thereby forming a hollow microneedle.

4. The method as recited in claim 1 , wherein the separating step (f) is performed by peeling.

5. The method as recited in claim 1 , wherein the separating step (f) is performed with the aid of ultrasonic agitation.

6. The method as recited in claim 1 , wherein the seed layer is a bilayer comprised of a chrome layer and a stainless steel layer.

7. The method as recited in claim 1 , wherein the nonconductive pattern is formed of a material comprising silicon carbide.

8. The method as recited in claim 7 , wherein the first metal layer comprises nickel.

9. The method as recited in claim 1 , further comprising the steps of re-using the substrate with the seed layer and nonconductive pattern formed thereon and repeating steps (d)–(g) to fabricate another microneedle.

10. A method of fabricating a microneedle, said method comprising the steps of:

(a) providing a substrate;

(b) forming a metal-containing seed layer on the top surface of the substrate;

(c) forming a nonconductive pattern on a portion of the seed layer;

(d) plating a first metal layer on the seed layer and over the edge of the nonconductive pattern to create a micromold with an opening that exposes a portion of the nonconductive pattern;

(e) separating the micromold from the seed layer and the nonconductive pattern, the separated micromold having exposed top and bottom surfaces;

(f) plating a second metal onto the micromold to fill the opening and to coat the exposed top and bottom surfaces of the micromold;

(g) selectively etching the micromold to release the plated second metal, whereby the plated second metal has the configuration of a microneedle structure attached to an excess layer; and

(h) separating the microneedle structure from the excess layer.

11. A method of fabricating an array of microneedles, said method comprising the steps of:

(a) providing a substrate;

(b) forming a metal-containing seed layer on the top surface of the substrate;

(c) forming an array of nonconductive patterns on the seed layer;

(d) plating a first metal layer on the seed layer and over the edges of the nonconductive patterns to create a micromold with a plurality of openings, each opening exposing a portion of a corresponding nonconductive pattern;

(e) plating a second metal onto the micromold to form an array of microneedles in the openings;

(f) mechanically separating the micromold with the microneedles formed therein from the seed layer and the nonconductive patterns; and

(g) selectively etching the micromold to release the array of microneedles.

12. The method of claim 11 , wherein the plating in step (d) is electroplating.

13. The method as recited in claim 11 , wherein the separating step (f) is performed by peeling.

14. The method as recited in claim 11 , wherein the separating step (f) is performed with the aid of ultrasonic agitation.

15. A method of fabricating a microneedle, said method comprising the steps of:

(a) providing a substrate with a recess in the top surface of the substrate, the recess having an apex;

(b) forming a metal-containing seed layer on the top surface including the recess;

(c) forming a nonconductive pattern on the seed layer so that a portion of the nonconductive pattern is in the recess;

(d) plating a first metal layer on the seed layer and over the edge of the nonconductive pattern to create a micromold with an opening that exposes a portion of the nonconductive pattern in the recess;

(e) plating a second metal onto the micromold to form a microneedle in the opening;

(f) separating the micromold with the microneedle formed therein from the seed layer and the nonconductive pattern; and

(g) selectively etching the micromold to release the microneedle.

16. The method as recited in claim 15 , wherein the plating in step (e) is carried out until the second metal fills the opening, thereby forming a solid microneedle.

17. The method as recited in claim 15 , wherein the plating in step (e) forms a metal coating on the sidewall surface of the opening, thereby forming a hollow microneedle.

18. The method as recited in claim 15 , wherein the recess is a pyramidal etched pit which defines the contour of the tip of the microneedle.

19. The method as recited in claim 15 , wherein the opening in the micromold is laterally aligned with the apex of the recess.

20. The method as recited in claim 15 , wherein the opening in the micromold is vertically aligned with the apex of the recess.

21. The method as recited in claim 15 , wherein the etched pit has an apex and the opening in the micromold is laterally offset from the apex.

22. The method as recited in claim 15 , wherein the etched pit has an apex and a sloped sidewall, and the opening in the micromold is offset from the apex and exposes a portion of the sloped sidewall, thereby forming a mold for a microneedle with a slanted tip.

23. The method as recited in claim 22 , wherein the plating in step (e) forms a metal coating on the sidewall surface of the opening, thereby producing a hollow microneedle with a slanted tip.