Self-assembly of alumina nanowires into controllable micro-patterns by laser-assisted solvent spreading: towards superwetting surfaces

Self-assembly of nanowires into micro-scale patterns, especially in a controlled manner, has received increasing research interest because of the wide variety of potential applications, including micro-optics and electronic devices, as well as nanomaterials-based energy conversion systems. In this contribution, a novel laser-assisted solution spreading method was developed to fabricate and self-assemble alumina nanowires (ANWs) into large-scale 3-dimensional (3D) micro-patterned surfaces in one step. Here, sodium hydroxide (NaOH) solution played a dual role, both chemically etching the anodic aluminum oxide template (AAO) into ANWs and self-assembling the as-obtained ANWs into micro-patterns under capillary force. It is notable that the micro-scale patterns can be artificially controlled by introducing laser points before solution spreading on the AAO template, and thus the laser-etched area will act as the fixation point during the ANW assembly process. Moreover, the as-prepared micro-patterned ANW film exhibits typical micro-/nano-hierarchical surface topology and shows superhydrophilicity. The film can be transformed into a superhydrophobic surface by chemical modification with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS). Here, by taking advantage of wetting and dewetting processes of a solution on an AAO template, we propose a facile method that enables the fabrication of 3D micro-patterned ANW surfaces, which have superwetting properties. We envisage that this method could shed new light on the fabrication of functional micro-patterned devices where a one-dimensional nano-material and solution phase are involved.