Method for creating topographical patterns in polymers via surface energy patterned films and the marangoni effect
Using a broadband light source and a photomask, surface energy gradients can be directly transferred into polymer films. The Marangoni effect causes high surface energy regions to rise upon heating the film. This leads to the formation of three-dimensional topography that can be locked in by quenching the polymer by cooling.
1. A method of forming a topographical pattern in a polymer substrate, comprising:
exposing the polymer substrate in its solid state to a pattern of activating light for a time sufficient to cause at least a portion of the polymer substrate exposed to the light to undergo a change in surface energy; and
heating the polymer substrate to a temperature sufficient to liquefy the polymer substrate after exposure to activating light, wherein the temperature is selected such that the polymer substrate adopts a topography that corresponds to the pattern of activating light.
2. The method of claim 1 , further comprising cooling the liquefied polymer substrate to solidify the polymer substrate.
3. The method of claim 1 , further comprising solidifying the liquefied polymer substrate by crosslinking the polymer substrate.
4. The method of claim 1 , wherein the polymer substrate is a thin film deposited on a substrate.
5. The method of claim 1 , wherein the pattern of activating light is formed by shining light through a mask that is proximate to the polymer substrate.
6. The method of claim 5 , wherein the mask is removed from the proximity of the polymer substrate prior to heating the polymer substrate.
7. The method of claim 1 , further comprising forming a liquid layer on a surface of the polymer substrate prior to exposing the polymer substrate to the pattern of activating light.
8. The method of claim 7 , wherein the liquid layer is removed from the surface after the polymer substrate is exposed to the pattern of activating light.
9. The method of claim 7 , wherein the liquid layer remains on the surface when the polymer substrate is heated to liquefy the polymer substrate.
10. The method of claim 1 , further comprising depositing a metal layer or other inorganic or vapor deposited compounds on a surface of the polymer substrate prior to exposing the polymer substrate to the pattern of activating light.
11. The method of claim 1 , further comprising depositing a metal layer or other inorganic or vapor deposited compounds on the surface of the activating light exposed polymer substrate prior to heating the polymer substrate to liquefy the polymer substrate.
12. The method of claim 1 , further comprising depositing a second polymeric layer on a surface of the polymer substrate prior to exposing the polymer substrate to the pattern of activating light.
13. The method of claim 1 , wherein the polymer substrate comprises a mixture of a polymer and one or more photosensitizers.
14. The method of claim 1 , wherein the polymer substrate comprises a polymer coupled to one or more photosensitizers.
15. The method of claim 2 , further comprising heating the cooled polymer substrate to liquefy the polymer at a temperature and time sufficient to remove at least a portion of the pattern.
16. The method of claim 1 , wherein the activating light is UV light.
17. The method of claim 1 , wherein the activating light is actinic light, visible light, or infrared light.
18. The method of claim 1 , wherein the polymer substrate comprises polystyrene.
19. The method of claim 1 , wherein the polymer substrate comprises poly(para-trimethylsilylstyrene), poly(methyl methacrylate), poly(isobutyl methacrylate), or poly(t-butoxycarbonyloxy styrene).
20. A method of transferring a topographical pattern from a patterned substrate, comprising:
contacting the patterned substrate with a liquid lithography mask material, and curing the material,
wherein the patterned substrate is a topographical patterned polymer substrate prepared by
exposing a polymer substrate in its solid state to a pattern of activating light for a time sufficient to cause at least a portion of the polymer substrate exposed to the light to undergo a change in surface energy; and
heating the polymer substrate to a temperature sufficient to liquefy the polymer substrate after exposure to activating light, wherein the temperature is selected such that the polymer substrate adopts a topography that corresponds to the pattern of activating light.