Superhydrophobic polymeric films with hierarchical structures produced by nanoimprint (NIL) and plasma roughening

Abstract

The structuration of various polymeric films has been studied to create superhydrophobic surfaces. Nanoimprint lithography and/or plasma etching processes with CF4/Ar have been used on FEP, PMMA and PET polymer films. On the one hand, the effect of the CF4/Ar gases, the input power and the plasma treatment duration have been investigated in terms of etching and fluorination degree, and XPS analyses are precisely discussed. On the other hand, wettability performances were characterized. Relationships between the contact angle, the contact angle hysteresis and the surface structures have been investigated. The wetting behaviors and the transition between the Wenzel and the Cassie-Baxter states was discussed as a function of the roughness. We have prepared each studied polymer films in transparent and flexible superhydrophobic surfaces whose contact angle are ∼160° and hysteresis are ∼2°. A short plasma treatment time (10 s) is sufficient to obtain a superhydrophobic behavior on FEP and PMMA. Results indicate that hierarchical structures allow a more stable superhydrophobic state regarding inhomogeneities. Moreover, the use of plasma etching is suggested to overcome some limitations of the NIL in the case of structures with a high aspect ratio. Finally, a quick and large surface fabrication method for superhydrophobic films is detailed.