Nanosecond laser induced glass particle deposition over steel mesh for long-term superhydrophilicity and gravity driven oil water separation

Highlights: • Laser textured metal mesh undergo wettability transition due to aging. • Such wettability transition renders the mesh unusable for oil water separation. • Use of a top glass plate during laser processing addresses the issue. • Mesh gets covered with glass particles which provide stable wettability. • Prepared mesh performs efficient oil water separation even after 8 months of storage. In this report we show that the laser textured stainless steel meshes which serve as excellent oil water separator immediately after laser processing, lose their oil water separation capability after storage in ambient air. This was possibly due to the reactive nature of the metal oxides formed during laser processing which resulted in transition of the wettability of processed metallic meshes from superhydrophilic to superhydrophobic during storage. To overcome this issue, we show that by using a glass cover plate over the metal mesh during laser processing, micron/submicron sized glass particles can be deposited on to the mesh via a process known as laser induced plasma assisted ablation. Since the glass is inherently hydrophilic and inert, and therefore the glass particles coating produced a stable superhydrophilic/underwater-superoleophobic surface which was observed to maintain its superhydrophilicity for the tested duration of ~8 months and perform oil/water separation with an efficiency of ~96% for various oils. Further, the glass particles coated mesh was found to sustain several cycles of sandpaper abrasion before losing its oil water separation capability.