Superhydrophobic titania membranes of different adhesive forces fabricated by electrospinning

Large area superhydrophobic titania membranes with high adhesive forces were fabricated by electrospinning, followed by calcination and surface modification with 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane (POTS). Varied surface structures were realized by controlling precursor aging time (t _aging) and electrospinning time (t_{electrospinning}) and by combination of electrospinning and hydrothermal treatment. A close relationship was observed between the contact angle and pore size of membrane. Water droplets on the surface appear spherical, which adsorb firmly onto the substrate even when the substrate is turned upside down. We investigated the dependence of the maximum adhesive force on pore size, which further revealed the relationship of the maximum adhesive force with the ratio of the pore size/fiber diameter. We found that t_aging and hydrothermal treatment time (t _hydrothermal) significantly affects the fiber substructure, which in turn largely influences the surface properties of the membrane, especially its shedding angle. A good stability of superhydrophobicity is observed for the titania membranes, pointing to promising future applications.