Compositions and methods to fabricate a photoactive substrate suitable for shaped glass structures
This invention provides an inexpensive and rapid method for fabricating a high-anisotropic-etch ratio, shaped glass structures using a novel photosensitive glass composition. Structures of the photosensitive glass may include micro-channels, micro-optics, microposts, or arrays of hollow micro-needles. Furthermore, such shaped glass structures can be used to form a negative mold for casting the shape in other materials.
1. A method to fabricate a shaped glass structure comprising:
preparing a photosensitive glass substrate having a glass transformation temperature and having a composition comprising:
60-76 weight % silica,
6 weight %-16 weight % of a combination of K 2 O and Na 2 O with at least 3 weight % K 2 O,
0.001-1 weight % Ag 2 O,
0.75 weight %-7 weight % B 2 O 3 , and
5-8 weight % Al 2 O 3 , wherein the combination of
B 2 O 3 , and Al 2 O 3 not exceeding 13 weight %,
8-15 weight % Li 2 O, and
0.04-0.1 weight % CeO 2 ; and
patterning a structure in a surface of the photosensitive glass substrate;
exposing at least a first portion of the photosensitive glass substrate to an activating energy source while leaving at least a second portion of said glass substrate unexposed;
heating the glass substrate to a temperature near the glass transformation temperature to transform at least part of the exposed glass to a crystalline material; and
etching the glass substrate in an etchant, wherein an etch ratio of exposed portion to said unexposed portion is at least 30:1 to provide a shaped glass structure with an aspect ratio of at least 30:1.
2. The method of claim 1 , wherein the glass composition is essentially germanium-free.
3. The method of claim 1 , wherein the glass composition comprises at least 1.25 weight % B 2 O 3 .
4. The method of claim 1 , wherein the glass composition comprises at least 0.3 weight % Sb 2 O 3 or As 2 O 3 .
5. The method of claim 1 , wherein the glass composition comprises 0.003-1 weight % Au 2 O.
6. The method of claim 1 , wherein the glass composition comprises 1-18 weight % of an oxide selected from the group consisting of CaO, ZnO, PbO, MgO and BaO.
7. The method of claim 1 , wherein the glass composition comprises 0-5 weight %, iron (Fe 2 O 3 ) to make the composition paramagnetic and/or to use iron (II) and iron (III) to quench intrinsic autofluorescence.
8. The method of claim 1 , wherein the glass composition comprises up to 2 weight % Copper Oxide.
9. The method of claim 1 , wherein an anisotropic-etch ratio of exposed portion to said unexposed portion is 30-45:1.
10. The method of claim 1 , wherein an anisotropic-etch ratio of exposed portion to said unexposed portion is at least one of 10-20:1; 21-29:1; 30-45:1; 20-40:1; 41-45:1; and 30-50:1.
11. The method of claim 1 , wherein the etchant comprises hydrofluoric acid.
12. The method of claim 1 , wherein the activating energy source comprises an ultraviolet light having a wavelength of about 308-312 nm.
13. The method of claim 1 , further comprising depositing a mold material onto the shaped glass structure to provide a negative mold, removing the negative mold from the glass structure, casting a non-glass material into the negative mold, solidifying the non-glass material in the negative mold, and removing the solidified non-glass material from the negative mold to provide a non-glass casting with an anisotropic-etch ratio of at least 30:1.
14. The method of claim 1 , wherein the activating energy source comprises a broad spectrum mid-ultraviolet flood lamp.
15. The method of claim 1 , wherein the activating energy source comprises a high powered energy source.