Preparation of asymmetric porous materials
As asymmetric porous film structure formed by depositing a porous material film on a flexible substrate, and applying an anisotropic stress to the porous media on the flexible substrate, where the anisotropic stress results from a stress such as an applied mechanical force, a thermal gradient, and an applied voltage, to form an asymmetric porous material.
1. A porous film structure, comprising:
a post-stressed, relaxed substrate comprising one of a piezoelectric material, a glass material, a Si material, a metal, or a shape memory alloy;
an anisotropically-stressed microporous film upon and in contact with the post-stressed, relaxed substrate;
wherein said anisotropically-stressed microporous film comprises a plurality of asymmetric pores; and
wherein the porous film structure is formed by a process comprising:
applying an anisotropic stress to a substrate, said anisotropic stress being applied by applying a mechanical force, a thermal stress, or a voltage to said substrate:
depositing a microporous film on a surface of the anisotropically-stressed substrate;
and removing the applied anisotropic stress from the substrate, thereby forming the post-stressed, relaxed substrate, anisotropically stressing the microporous film, and forming the plurality of asymmetric pores within the microporous film.
2. The structure of claim 1 , wherein the porous film has a thickness between approximately 10 nm and 100 nm.
3. The structure of claim 1 , wherein said piezoelectric material is aluminum nitride.
4. The structure of claim 1 wherein said microporous film comprises a material selected from the group consisting of silica, alumina, aluminosilicate, titania, an organic material, and an organic-inorganic hybrid material.
5. The structure of claim 1 wherein said microporous film comprises a zeolite.
6. The structure of claim 1 , wherein the asymmetric pore structure comprises asymmetric chiral pores.