Bioinspired Wire-on-Pillar Magneto-Responsive Superhydrophobic Arrays

Abstract

Versatile surfaces demonstrating multiple interfacial functionalities are highly demanded as a surface typically serves various duties and faces multiple challenges in real practice. However, such versatile surfaces are rarely reported mainly due to the challenges in integrating multiple structural characteristics. Here, by mimicking lotus leaves, butterfly wing, and respiratory cilia, we develop a surface termed wire-on-pillar magneto-responsive superhydrophobic arrays (WP-MRSA), which possess interfacial properties of structural superhydrophobicity, anisotropicity, stimuli responsiveness, and flexibility. By combining soft lithography and self-alignment of iron-laden aerosols under a magnetic field, iron-laden wires are planted atop prefabricated pillar arrays, resulting in well-ordered, sparse, high-aspect-ratio, flexible, and superhydrophobic wires, which largely deflect in response to a magnetic field. This unique integration of structural properties and configurations enables various functionalities, such as on-demand control of droplet impact dynamics, real-time regulation of surface lateral adhesion force, fast removal and sorting of objects, and precise manipulation of droplets for selective reactions. Those functionalities benefit various applications especially droplet-based microfluidics and active self-cleaning surfaces.