Fabrication and self-aligned local functionalization of nanocups and various plasmonic nanostructures on flexible substrates for implantable and sensing applications
Methods for fabricating flexible substrate nanostructured devices are disclosed. The nanostructures comprise nano-pillars and metallic bulbs or nano-apertures. The nanostructures can be functionalized to detect biological entities. The flexible substrates can be rolled into cylindrical tubes for detection of fluidic samples.
1. A method comprising:
etching a silicon substrate to form silicon nanostructures on top of the silicon substrate;
oxidizing the silicon nanostructures to form silicon oxide nanostructures;
depositing a metallic layer on the silicon oxide nanostructures;
reflowing the metallic layer to form metallic bulbs on a top section of the silicon oxide nanostructures;
depositing a continuous flexible substrate on the metallic bulbs and on the silicon oxide nanostructures; and
removing the silicon substrate and the silicon oxide nanostructures.
2. The method of claim 1 , wherein the nanostructures are pillars.
3. The method of claim 1 , wherein the metallic layer is Au.
4. The method of claim 1 , wherein the continuous flexible substrate is polydimethylsiloxane.
5. The method of claim 1 , further comprising depositing a sacrificial layer between the silicon oxide nanostructures and the continuous flexible substrate.
6. The method of claim 1 , wherein the continuous flexible substrate is transparent to optical waves.
7. The method of claim 1 , further comprising reshaping the metallic bulbs prior to depositing the continuous flexible substrate.
8. The method of claim 7 , wherein reshaping comprises applying a focused ion beam with a different intensity for at least two metallic bulbs.
9. The method of claim 7 , wherein reshaping comprises ion milling the metallic bulbs.
10. The method of claim 7 , wherein reshaping comprises shadow evaporating at an angle.
11. The method of claim 10 , wherein shadow evaporating at an angle comprises shadow evaporating at an angle in successive steps, each step being at a different angle.
12. The method of claim 1 , further comprising bending the continuous flexible substrate with the nanostructures being on a concave side of the continuous flexible substrate.
13. The method of claim 12 , wherein bending the continuous flexible substrate comprises bending the continuous flexible substrate in a cylinder shape.
14. The method of claim 13 , wherein bending the continuous flexible substrate is carried out in a spiral fashion.
15. The method of claim 13 , wherein the continuous flexible substrate rolled in the cylinder shape is configured to contain a fluid sample flow within.
16. The method of claim 15 , wherein the continuous flexible substrate rolled in the cylinder shape is further configured to act as a waveguide for optical waves.
17. A method comprising:
etching a silicon substrate to form silicon nanostructures on top of the silicon substrate;
oxidizing the silicon nanostructures to form silicon oxide nanostructures;
depositing a metallic layer on the silicon oxide nanostructures and on the silicon substrate between the silicon oxide nanostructures;
reflowing the metallic layer to form metallic bulbs on a top section of the silicon oxide nanostructures while leaving parts of the metallic layer on the silicon substrate between the silicon oxide nanostructures;
removing the silicon oxide nanostructures to form nano-apertures between the parts of the metallic layer on the silicon substrate;
depositing a continuous sacrificial layer on the nano-apertures;
attaching a carrier chip to the continuous sacrificial layer;
removing the silicon substrate by etching;
depositing a continuous flexible substrate on a surface of the nano-apertures opposite to a surface with the continuous sacrificial layer; and
removing the continuous sacrificial layer and the carrier chip.
18. The method of claim 17 , further comprising inserting an adhesive layer between the continuous flexible substrate and the surface of the nano-apertures opposite to a surface with the continuous sacrificial layer, and wherein the removing the silicon oxide nanostructures is by etching or mechanical removal.
19. The method of claim 17 , wherein the nanostructures are pillars.
20. The method of claim 17 , wherein the metallic layer is Au.
21. The method of claim 17 , wherein the continuous flexible substrate is polydimethylsiloxane.
22. The method of claim 17 , further comprising depositing a sacrificial layer between the silicon oxide nanostructures and the continuous flexible substrate.
23. The method of claim 17 , wherein the continuous flexible substrate is transparent to optical waves.
24. The method of claim 17 , wherein removing the silicon oxide nanostructures to form nano-apertures comprises controlling a depth at which the nano-apertures are formed.
25. A method comprising:
etching a silicon substrate to form silicon nanostructures on top of the silicon substrate;
oxidizing the silicon nanostructures to form silicon oxide nanostructures;
depositing a metallic layer on the silicon oxide nanostructures;
reflowing the metallic layer to form metallic bulbs on a top section of the silicon oxide nanostructures;
depositing a photosensitive layer on the metallic bulbs and on the silicon oxide nano structures;
selecting an intensity for optical excitation to be above an excitation threshold only for the photosensitive layer between the metallic bulbs;
optically exciting at the selected intensity;
removing the excited photosensitive layer, thereby leaving gaps in the photosensitive layer between the metallic bulbs; and
functionalizing the gaps between the metallic bulbs.
26. The method of claim 25 , further comprising an adhesive layer attached to the continuous flexible substrate on a surface opposite the nanostructures.