Two-Photon Polymerization of Butterfly Wing Scale Inspired Surfaces with Anisotropic Wettability

Abstract

Wings of Morph aega butterflies are natural surfaces that exhibit anisotropic liquid wettability. The direction-dependent arrangement of the wing scales creates orientation-turnable microstructures with two distinct contact modes for liquid droplets. Enabled by recent developments in additive manufacturing, such natural surface designs coupled with hydrophobicity play a crucial role in applications such as self-cleaning, anti-icing, and fluidic manipulation. However, the interplay among resolution, architecture, and performance of bioinspired structures is barely achieved. Herein, inspired by the wing scales of the Morpho aega butterfly, full-scale synthetic surfaces with anisotropic wettability fabricated by two-photon polymerization are reported. The quality of the artificial butterfly scale is improved by optimizing the laser scanning strategy and the objective lens movement path. The corresponding contact angles of water on the fabricated architecture with various design parameters are measured, and the anisotropic fluidic wettability is investigated. Results demonstrate that tuning the geometrical parameters and spatial arrangement of the artificial wing scales enables anisotropic behaviors of the droplet's motion. The measured results also indicate a reverse phenomenon of the fabricated surfaces in contrast to their natural counterparts, possibly attributed to the significant difference in equilibrium wettability between the fabricated microstructures and the natural Morpho aega surface. These findings are utilized to design next-generation fluid-controllable interfaces for manipulating liquid mobility on synthetic surfaces.