Blue phases on patterned surfaces
Stable, macroscopic single-crystal chiral liquid crystal compositions are described. The compositions include a single-crystal chiral liquid crystal material on a patterned surface. The patterned surface seeds a particular crystallographic orientation at the substrate-liquid crystal interface. Also described are methods of forming the single-crystal chiral liquid crystal compositions.
1. An article comprising:
a substrate having a surface, wherein the surface is patterned with a surface pattern that extends over a first area;
a monocrystalline liquid crystalline material that extends over the first area, wherein the surface pattern comprises regions that induce a first orientation of molecules in the monocrystalline liquid crystalline material and regions that a second orientation of molecules in the monocrystalline liquid crystalline material, wherein the first and second orientations are different.
2. The article of claim 1 , wherein the monocrystalline liquid crystalline material is a blue phase liquid crystal.
3. The article of claim 1 , wherein the monocrystalline material is a cholesteric liquid crystal.
4. The article of claim 1 , wherein the surface pattern is a stripe pattern or a hexagonal array pattern.
5. The article of claim 1 , wherein the first area is at least 1 mm 2 .
6. The article of claim 1 , wherein the monocrystalline material is at least 20 μm thick.
7. The article of claim 1 , wherein the surface pattern relieves elastic distortions that would be induced by a homogenous surface.
8. The article of claim 1 , wherein the surface pattern comprises topographical features.
9. The article of claim 1 , wherein the surface pattern comprises chemical and topographical features.
10. The article of claim 1 , wherein the surface pattern is a pattern of stripes, the pattern period L s is the width of two adjacent stripes, and the pattern period L s is equal to the lattice constant of a unit cell of the monocrystalline liquid crystalline material.
11. The article of claim 1 , wherein the surface pattern is a hexagonal array of features, the pattern period L s is the center-to-center distance of adjacent features, and the pattern period L s is equal to the square root of two times the lattice constant of a unit cell of the monocrystalline liquid crystalline material.
12. The article of claim 1 , wherein the surface is patterned with regions that induce a tilted orientation of molecules in the monocrystalline liquid crystalline material.
13. The article of claim 1 , wherein the monocrystalline liquid crystalline material is switchable on application of an external field.
14. A liquid crystal cell comprising:
the article according to claim 1 ;
a second substrate having a second substrate surface, wherein the monocrystalline liquid crystalline material is disposed between the surface and the second substrate surface.
15. The liquid crystal cell of claim 14 , wherein the second substrate surface is homogenous.
16. The liquid crystal cell of claim 14 , wherein the second substrate surface has a second surface pattern.
17. A method comprising:
providing a first substrate having a surface pattern that extends over a first area;
providing a second substrate;
disposing a liquid crystal mixture between the first substrate and the second substrate such that the liquid crystal mixture contacts the surface pattern; and
allowing the surface pattern to direct the self-assembly of the liquid crystal material to form a monocrystalline liquid crystal over the surface pattern to thereby form an article according to claim 1 .
18. An article comprising:
a substrate having a surface, wherein the surface is patterned with a surface pattern that extends over a first area;
a monocrystalline liquid crystalline material that extends over the first area, wherein the surface comprises a second surface pattern that extends over a second area and a monocrystalline liquid crystalline material that extends over the second area, wherein the monocrystalline liquid crystalline material that extends over the first area has a first unit cell orientation, the monocrystalline liquid material that extends over the second area has a second unit cell orientation and is separated by the monocrystalline liquid material that extends over the first area by a single defect line.
19. An article comprising:
a substrate having a surface, wherein the surface is patterned with a surface pattern that extends over a first area;
a monocrystalline liquid crystalline material that extends over the first area, wherein the monocrystalline liquid crystalline material overlies a surface that comprises patterned regions separated by an unpatterned region.