Systems and methods for oleophobic composite membranes
Atomic layer deposition is utilized to deposit a coating on a membrane. The coated membrane exhibits a tightly bound hydration layer upon exposure to water. The resultant coated membrane is oleophobic.
1. A method of fabricating an oleophobic membrane comprising:
providing a membrane comprising a bulk material selected from the group of hydrophobic materials consisting of polyvinylidene fluoride (PVDF) and a hydrophilic additive comprising polyvinyl pyrrolidone (PVP) the membrane having a hydrophilic moiety exposed at a surface of at least a first side of the membrane, and depositing an oxide coating selected from the group consisting of SiO 2 , TiO 2 or SnO 2 on the surface of the first side of the membrane by atomic layer deposition by X cycles of the steps of:
performing A atomic layer deposition subcycles of a first ALD precursor at a first deposition temperature, wherein the first ALD precursor binds with the hydrophilic moiety; and
performing B atomic layer deposition subcycles of a second ALD precursor at a second deposition temperature;
where X is greater than 0, A is greater than 0 and B is greater than 0;
wherein a second side of the membrane, opposite the first side of the membrane, remains uncoated by the oxide coating.
2. The method of claim 1 , wherein the first temperature and the second temperature are less than 150° C.
3. The method of claim 1 , wherein the coating comprises TiO 2 and the first ALD precursor is titanium tetrachloride and wherein the second ALD precursor is water.
4. The method of claim 1 , wherein the coating comprises SnO 2 and the first ALD precursor is tetrakis(dimethylamino) tin(IV) and wherein the second ALD precursor is water.
5. The method of claim 1 , further comprising exposing the coated membrane to liquid water and forming a hydration layer adjacent the oxide coating.
6. The method of claim 1 , wherein the membrane includes a plurality of pores and further wherein the oxide coating extends into the plurality of pores.
7. A method of fabricating an oleophobic membrane comprising:
providing a membrane having a bulk hydrophobic polymer and a hydrophilic additive selected from the additive group consisting of polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG), piperazine, cellulose acetate phthalate (CAP), or malic acid, the membrane having a first side and a second side,
depositing an oxide coating directly on a first side of the membrane, binding with the hydrophilic additive, comprising an oxide selected from the group consisting of TiO 2 and SnO 2 by atomic layer deposition at a temperature less than 125° C. by the steps of:
a) performing atomic layer deposition of a first ALD precursor at a first deposition temperature, wherein the first ALD precursor binds with the hydrophilic moiety;
b) purging the first ALD precursor with an inert gas;
c) performing atomic layer deposition of a second ALD precursor at a second deposition temperature;
d) purging the second ALD precursor with an inert gas; and
repeating steps a), b), c), and d) until the oxide coating is at least 1-20 nm thick;
wherein a second side of the membrane, opposite the first side of the membrane, remains uncoated by the oxide coating.
8. The method of claim 7 , wherein the coating comprises TiO 2 or SnO 2 .
9. The method of claim 7 , wherein the coating comprises TiO 2 and the first ALD precursor is titanium tetrachloride and wherein the second ALD precursor is water.
10. The method of claim 7 , wherein the coating comprises SnO 2 and the first ALD precursor is tetrakis(dimethylamino) tin(IV) and wherein the second ALD precursor is water.
11. The method of claim 7 , further comprising exposing the coated membrane to liquid water and forming a hydration layer adjacent the oxide coating.