Fabrication of Superhydrophobic and Oleophobic Surfaces with Overhang Structure by Reverse Nanoimprint Lithography

This work reports the fabrication of superhydrophobic and oleophobic surfaces with an overhang structure by reverse nanoimprint lithography. An overhang structure is difficult to fabricate by conventional lithography; however, it was conveniently formed by reverse imprint lithography, employed in conjunction with reactive ion etching. The obtained overhang structure was coated with a fluoroalkylsilane monolayer to reduce its surface energy. Further, four different types of nanopatterns were separately embedded on the surface of the obtained overhang structure by modified reverse imprint lithography to enhance its oil-repelling properties. The embedded nanopatterns resulted in different overhang angles, thereby enhancing the oil-repelling properties. The morphology and wetting characteristics of the overhang structure were investigated by scanning electron microscopy and contact angle measurements. This study demonstrates that an overhang structure can be successfully fabricated on a substrate by reverse nanoimprint lithography; moreover, oleophobic structures can be realized using materials with contact angles <90 degrees