Micro-needle arrays having non-planar tips and methods of manufacture thereof
A micro-needle array having tips disposed along a non-planar surface is formed by shaping the wafer surface into a non-planar surface to define the tips of the micro-needles. A plurality of trenches are cut into the wafer to form a plurality of columns having tops corresponding to the non-planar surface. The columns are rounded and sharpened by etching to form the micro-needles.
1. A method of fabricating an array of micro-needles having tips disposed along a non-planar surface comprising:
providing a wafer which is non-flexible;
shaping a top surface of the wafer into a non-planar surface;
cutting a first plurality of trenches into the non-planar surface, wherein the first plurality of trenches are uniformly spaced;
cutting a second plurality of trenches into the non-planar surface to intersect the first plurality of trenches to form a plurality of columns having tops defined by the non-planar surface and wherein the second plurality of trenches are uniformly spaced such that the plurality of columns have a uniform width; and
etching the plurality of columns to round the columns and sharpen the tops into needle tips to form the array of micro-needles such that tips of the micro-needles are disposed substantially along the non-planar surface, wherein the tip surface is a three-dimensional curve and the micro-needles are electrically conductive and electrically insulated from each other, and wherein the three-dimensional curve is a continuous function defined by z=f(x,y) where z is a height of the micro-needles as a function of horizontal location x and y, and the micro-needles are solid throughout.
2. The method of claim 1 wherein at least one of cutting a first plurality of trenches and cutting a second plurality of trenches comprises varying a depth of the trenches so that bases of the columns define a second non-planar surface.
3. The method of claim 2 wherein cutting a first plurality of trenches and cutting a second plurality of trenches each comprise varying a depth of the trenches so that bases of the columns define a second non-planar surface.
4. The method of claim 1 wherein shaping the top surface of the wafer into the non-planar surface comprises:
cutting a plurality of trenches of varying depth into the top surface, the depth of the trenches corresponding to the non-planar surface; and
etching the top surface to remove material left between the trenches to form the non-planar surface.
5. The method of claim 1 wherein shaping a top surface of the wafer into a non-planar surface comprises forming a three-dimensional surface curved in two different directions.
6. The method of claim 1 wherein the first plurality of trenches and the second plurality of trenches are cut at angles of substantially 90 degrees to each other.
7. The method of claim 1 further comprising:
cutting a third plurality of trenches into a back surface of the wafer; and
filling the third plurality trenches with an insulating material.
8. The method of claim 7 wherein the insulating material is glass.
9. The method of claim 7 wherein cutting a plurality of trenches into a back surface of the wafer comprises varying depth of the trenches to correspond to the non-planar surface.
10. The method of claim 9 wherein cutting the first plurality of trenches into the non-planar surface and cutting the second plurality of trenches into the non-planar surface each comprise cutting to a depth sufficient to intersect the third plurality of trenches.
11. The method of claim 1 further using the wafer to form a mold.
12. The method of claim 1 , wherein the three-dimensional curve is concave or convex.
13. A micro-needle array having tips disposed in a non-planar arrangement comprising:
a substrate which is non-flexible; and
a plurality of micro-needles each having a base and a tip, and are solid throughout each micro-needle, the bases of the micro-needles being supported by the substrate and the tips of the micro-needles defining a non-planar tip surface said tip surface being a three-dimensional curve which is a continuous function defined by z=f(x,y) where z is a height of the micro-needles as a function of horizontal location x and y, wherein the micro-needles are electrically conductive and electrically insulated from each other.
14. The micro-needle array of claim 13 , wherein the plurality of micro-needles are substantially parallel.
15. The micro-needle array of claim 13 , wherein the substrate is formed of glass and the micro-needles are formed of silicon.
16. The micro-needle array of claim 13 , wherein the substrate is formed of biodegradable plastic.
17. The micro-needle array of claim 13 , further comprising a conductive coating disposed on the micro-needles.
18. The micro-needle array of claim 17 , further comprising a non-conductive coating disposed over the conductive coating except at a tip portion of the micro-needles.
19. The micro-needle array of claim 13 , wherein the substrate and the micro-needles are formed of a common material.
20. The micro-needle array of claim 13 , wherein the bases of the micro-needles define a non-planar base surface.
21. The micro-needle array of claim 13 , wherein the non-planar tip surface is convex.
22. The micro-needle array of claim 13 , wherein the non-planar tip surface is concave.
23. The micro-needle array of claim 13 , wherein the plurality of micro-needles have a uniform base width.