Bio-Inspired Anisotropic Wettability Surfaces from Dynamic Ferrofluid Assembled Templates

The biomimetic principle of harnessing topographical structures to determine liquid motion behavior represents a cutting-edge direction in constructing green transportation systems without external energy input. Here, inspired by natural Nepenthes peristome, a novel anisotropic wettability surface with characteristic structural features of periodically aligned and overlapped arch-shaped microcavities, formed by employing ferrofluid assemblies as dynamic templates, is presented. The magnetic strength and orientation are precisely adjustable during the generation process, and thus the size and inclination angle of the ferrofluid droplet templates could be tailored to make the surface morphology of the resultant polymer replica achieve a high degree of similarity to the natural peristome. The resultant anisotropic wettability surface enables autonomous unidirectional water transportation in a fast and continuous way. In addition, it could be tailored into arbitrary shapes to induce water flow along a specific curved path. More importantly, based on the anisotropic wettability surface, novel pump-free microfluidic devices are constructed to implement multiphase flow reactions, which offer a promising solution to building low-cost, portable platform for lab-on-a-chip applications.