Deterministic fabrication of hierarchically ordered, monolithic nanotextures by directional photofluidization lithography and example of its use in superhydrophobic surface

Abstract

Over the last decade, the fabrication of hierarchically ordered, monolithic nanotextures have attracted a great interest due to its promising application such as advanced photonics and interface sciences. Even if many impressive results have been achieved, most of established methods still suffer from several drawbacks including low throughput, inherently having defects, and multistep process. Herein, to overcome such limitations, we have suggested a new strategy for the generation of hierarchically ordered, monolithic nanotextured surfaces by directional photofluidization lithography (DPL).1-6 DPL enable the fabrication of a variety of nanostructural motifs with precisely controlled structural features in a very unique way. The key of DPL is to use the photo-reconfigurable polymer (i.e., azopolymer) arrays instead of a conventional colloidal nanosphere, photoresist arrays, and polydimethylsiloxane (PDMS) arrays. By taking advantages of DPL, the structural features of hierarchically ordered nanotexture (i.e., shapes and modulation heights) could be precisely and simply tuned by adjusting the beam variables including polarization, irradiation time, and incident angle. Furthermore, in a more practical point of view, this method also can provide an effective tool for the control of the wettability due to its advantage of simple and deterministic tuning of the structural features. Besides the fabrication of diverse hierarchically ordered, monolithic nanotextures, we believe that this clever experimental strategy and resulting phenomenological finding can give us an important experimental clue for the better understanding of underlying mechanism of surface relief gratings formation onto photo-reconfigurable azopolymer film, which has been a long-lasting question. Therefore, this work can beat the limitation of our current understanding about photo-induced azopolymer movement during light irradiation and, in turn, will greatly extend our ability to fabricate diverse nanotextured structures.