Composite membranes and methods of making and use thereof

A composite membrane having a top portion and a bottom portion, the top portion being hydrophilic in air and oleophobic under water and the bottom portion being omniphobic, the composite membrane comprising:

• an omniphobic substrate having a hierarchical reentrant structure;
• wherein the omniphobic subtrate comprises a plurality of electrospun polymer fibers and a plurality of pores, the plurality of electrospun polymer fibers being coated with a plurality of particles, the plurality of pores and the plurality of particles forming the hierarchical reentrant structure;
• wherein the plurality of electrospun polymer fiber comprise a hydrophobic polymer and a surface charge dopant, the hydrophobic polymer comprising poly(vinylidene fluoride-co-heafluoropropylene) (PVDF-HFP) and the surface charge dopant comprising cetyltrimethylammonium bromide (CTAB);
• wherein the plurality of particles comprise a plurality of fluorinated silicon dioxide particles;
• wherein the omniphobic substrate has a surface, the surface being coated with a dual functional layer that is hydrophilic in air and oleophobic under water, the coated surface of the omniphobic substrate being the top portion of the composite membrane;
• wherein the dual functional layer comprises a surface roughness component, a hydrophilic component, and a low surface energy material;
• wherein the surface roughness component comprises a plurality of silicon dioxide particles;
• wherein the hydrophilic component comnprises chitosan;
• and
• wherein the low surface energy material comprises a fluorinated compound, the fluorinated compoound comprising perfluorooctanoate.