Method to fabricate hollow microneedle arrays
View Patent ↗An inexpensive and rapid method for fabricating arrays of hollow microneedles uses a photoetchable glass. Furthermore, the glass hollow microneedle array can be used to form a negative mold for replicating microneedles in biocompatible polymers or metals. These microneedle arrays can be used to extract fluids from plants or animals. Glucose transport through these hollow microneedles arrays has been found to be orders of magnitude more rapid than natural diffusion.
1. A method to fabricate a hollow microneedle array, comprising:
exposing a photoetchable glass wafer to ultraviolet light through a first patterned mask to define a latent image of a bore of at least one hollow microneedle in the glass wafer;
heating the glass wafer to a temperature in excess of the glass transformation temperature to transform the amorphous material in the exposed latent image of the bore of the at least one microneedle to a crystalline material, thereby providing a crystallized image of the bore of the at least one microneedle in the glass wafer;
exposing the glass wafer to ultraviolet light through a second patterned mask to define a latent image of the regions between the at least one hollow microneedle, wherein the exposing to define the between regions is performed before or after the exposing to define the bore;
heating the glass wafer to a temperature in excess of the glass transformation temperature to transform the amorphous material in the exposed latent image of the between regions to a crystalline material, thereby providing an crystallized image of the between regions in the glass wafer; and
etching the glass wafer in an etchant to remove the crystallized image regions, thereby providing a glass hollow microneedle array comprising the at least one hollow microneedle.
2. The method of claim 1 , wherein the photoetchable glass comprises lithium-aluminum-silicate glass containing silver and germanium ions.
3. The method of claim 1 , wherein the bore of the at least one hollow microneedle has a cross-sectional dimension of greater than 25 microns.
4. The method of claim 1 , wherein the tip of the at least one hollow microneedle has a cross-sectional dimension of greater than 100 microns.
5. The method of claim 1 , wherein the height of the at least one hollow microneedle is less than 1 millimeter.
6. The method of claim 1 , wherein the etchant comprises hydrofluoric acid.
7. The method of claim 1 , wherein the wavelength of the ultraviolet light corresponds to the absorption band of a sensitizing impurity in the photoetchable glass.
8. The method of claim 1 , further comprising depositing a mold material onto the glass hollow microneedle array to provide a negative mold, removing the negative mold from the glass hollow microneedle array, casting a liquid polymer into the negative mold, solidifying the polymer in the negative mold, and removing the solidified polymer from the negative mold to provide a polymeric hollow microneedle array.
9. A method to fabricate a hollow microneedle array, comprising:
exposing a photoetchable glass wafer to ultraviolet light through a first patterned mask to define a latent image of the regions between at least one hollow microneedle in the glass wafer;
exposing the glass wafer to ultraviolet light through a second patterned mask to define a latent image of a bore of the at least one hollow microneedle,
heating the glass wafer to a temperature in excess of the glass transformation temperature to transform the amorphous material in the exposed latent image of the between regions and the bore of the at least one microneedle to a crystalline material, thereby providing a crystallized image of the between regions and the bore of the at least one microneedle in the glass wafer; and
etching the glass wafer in an etchant to remove the crystallized image regions, thereby providing a glass hollow microneedle array comprising the at least one hollow microneedle.
10. The method of claim 9 , wherein the photoetchable glass comprises lithium-aluminum-silicate glass containing silver and germanium ions.
11. The method of claim 9 , wherein the bore of the at least one hollow microneedle has a cross-sectional dimension of greater than 25 microns.
12. The method of claim 9 , wherein the tip of the at least one hollow microneedle has a cross-sectional dimension of greater than 100 microns.
13. The method of claim 9 , wherein the height of the at least one hollow microneedle is less than 1 millimeter.
14. A method to fabricate a hollow microneedle array, comprising:
forming a glass negative mold of the hollow microneedle array, the mold forming comprising:
exposing a photoetchable glass wafer to ultraviolet light through a first patterned mask to define a latent image of the regions between at least one hollow microneedle in the glass wafer,
heating the glass wafer to a temperature in excess of the glass transformation temperature to transform the amorphous material in the exposed latent image of the between regions to a crystalline material, thereby providing a crystallized image of the between regions in the glass wafer,
exposing the glass wafer to ultraviolet light through a second patterned mask to define a latent image of the wall regions of the at least one hollow microneedle, wherein the exposing to define the wall regions is performed before or after the exposing to define the between regions,
heating the glass wafer to a temperature in excess of the glass transformation temperature to transform the amorphous material in the exposed latent image of the wall regions to a crystalline material, thereby providing an crystallized image of the wall regions in the glass wafer, and
etching the glass wafer in an etchant to remove the crystallized image regions, thereby providing a glass negative,
molding a structural material into the glass negative mold; and
removing the glass negative mold to provide a microneedle array comprising the at least one hollow microneedle of the structural material.
15. The method of claim 14 , wherein the photoetchable glass comprises lithium-aluminum-silicate glass containing silver and germanium ions.
16. The method of claim 14 , wherein the structural material comprises a polymer.
17. The method of claim 14 , wherein the structural material comprises a metal.
18. The method of claim 14 , wherein the bore of the at least one microneedle has a cross-sectional dimension of greater than 25 microns.
19. The method of claim 14 , wherein the tip of the at least one hollow microneedle has a cross-sectional dimension of greater than 100 microns.
20. The method of claim 14 , wherein the height of the at least one hollow microneedle is less than 1 millimeter.
21. The method of claim 14 , wherein the etchant comprises hydrofluoric acid.
22. The method of claim 14 , wherein the wavelength of the ultraviolet light corresponds to the absorption band of a sensitizing impurity in the photoetchable glass.
23. A method to fabricate a hollow microneedle array, comprising:
forming a glass negative mold of the hollow microneedle array, the mold forming comprising:
exposing a photoetchable glass wafer to ultraviolet light through a first patterned mask to define a latent image of the regions between at least one hollow microneedle in the glass wafer,
exposing the glass wafer to ultraviolet light through a second patterned mask to define a latent image of the wall regions of the at least one hollow microneedle,
heating the glass wafer to a temperature in excess of the glass transformation temperature to transform the amorphous material in the exposed latent image of the between regions and the wall regions to a crystalline material, thereby providing crystallized images of the between regions and the wall regions in the glass wafer, and
etching the glass wafer in an etchant to remove the crystallized image regions, thereby providing a glass negative,
molding a structural material into the glass negative mold; and
removing the glass negative mold to provide a microneedle array comprising the at least one hollow microneedle of the structural material.
24. The method of claim 23 , wherein the photoetchable glass comprises lithium-aluminum-silicate glass containing silver and germanium ions.
25. The method of claim 23 , wherein the structural material comprises a polymer.
26. The method of claim 23 , wherein the structural material comprises a metal.
27. The method of claim 23 wherein the bore of the at least one microneedle has a cross-sectional dimension of greater than 25 microns.
28. The method of claim 23 , wherein the height of the at least one hollow microneedle is less than 1 millimeter.