A Bioinspired Surface with Synergistic Effect of Anisotropy and Gradient Microstructures for Controllable Fluid Transportation

Abstract

The fluid on micro-nanostructures with anisotropy or gradient can exhibit highly inducible wettability that can be found in both nature and artificiality. In this study, inspired by the anisotropic and gradient micro-nanostructures on rice leaf and cactus spine, respectively, we fabricated a wedgy polydimethylsiloxane with ordered micropit arrays (WPOMA) by a rapid strategy to strengthen the property of directional water transportation as a result of their synergistic effect. The unit structure in the array exhibits anisotropy under stretched stress, whereas the unit structure in the long range along the WPOMA shows an arrangement of gradient. Therein, the anisotropic elliptical micropit arrays generated by stretched stress contribute to the axial flow, whereas the gradual change of micropit arrays with morphology gradient contributes to the directional flow. The concurrent axial and directional flows have a great performance in fluid transportation and collection. Additionally, the anisotropic and gradient synergistic micro-nanostructures can be controlled in real time by reversible mechanical stress, which was revealed at the stretched state and hidden at the released state. Meanwhile, the flexible texture effectuated the flow-induced capacity even at the bending state. On the basis of the synergistic effect and switchable wettability, the flexible material paves a way in the potential applications in anti-drag wearable devices, droplet manipulators, and controllable fluid transportation.