We demonstrate that tunable superoleophobic surfaces fabricated by a simple spin and spray coating methods of titania on silicon (Si) wafers and stainless steel (SS) mesh, which possess a hierarchical re-entrant structure consisting of nano meter sized particles on top of micron sized particle, are able to induce superoleophobicity on an oleophilic self assembled monolayer of 1H,1H,2H,2H-perflurodecyltrichlorosilane (FDTS). Though comparison between different coating methods, we show that spray coating on Si substrate and SS mesh can repel lower surface tension liquids than spin coating on Si substrates due to formation of half spherical micro-particles on the spray coated substrates which is confirmed by FESEM images. Subsequently, superoleophobic surfaces changes its super repellent property to complete wetting of any liquids under UV illumination by decomposing the FDTS molecules via photo catalytic property of titania particles. The superoleophobic property was regained by annealing followed by grafting of FDTS on the UV treated surface and the total process is repeatable over number of cycles.
Barman, Jitesh, Sumit Kumar Majumder, Krishnacharya Khare