Bio-Inspired Multi-gradient Structure Surfaces for Water Collection/Repellency

Y. Zheng
Beihang University, CN

Keywords: water collection, water repellency


Biological surfaces with micro- and nanostructures display unique wetting functions. Since spider silk collects water through a combination of multiple gradients in a periodic spindle-knot structure after wet-rebuilding process, a series of functional fibers with unique wettability have been designed and fabricated successfully by various improved techniques such as dip-coating, fluid-coating, tilt-angle coating, electrospun and self-assembly, to combine the Rayleigh instability theory. These geometrically-engineered thin fibers display a strong water capturing ability, directional driving of tiny droplets, a capable of intelligently responding to environmental changes in humidity, and also directional droplet transport in a long range. Otherwise, biological surfaces such as plant leaves and butterfly wings display water repellency. The suspending of microdroplets on a fresh lotus leaf is attributed to a gradient of wettable MNs along the exterior surface of papillae including nanohairs. The directional water repellency is achieved on wings of butterflies due to a flexibly oriented MN on wing. Also the MNs of wing generate low-temperature superhydrophobic properties. A MN thin flexible surface is fabricated, which displays excellent de-ice ability. In summary, these as-fabricated surfaces wil have promising applications in water-collecting, anti-icing, anti-frosting, or anti-fogging properties for practical applications in aerospace and industry.