Unidirectional Wetting Properties on Multi‐Bioinspired Magnetocontrollable Slippery Microcilia

Abstract

Here, a smart fluid-controlled surface is designed, via the rational integration of the unique properties of three natural examples, i.e., the unidirectional wetting behaviors of butterfly's wing, liquid-infused "slippery" surface of the pitcher plant, and the motile microcilia of micro-organisms. Anisotropic wettability, lubricated surfaces, and magnetoresponsive microstructures are assembled into one unified system. The as-prepared surface covered by tilted microcilia achieves significant unidirectional droplet adhesion and sliding. Regulating by external magnet field, the directionality of ferromagnetic microcilia can be synergistically switched, which facilitates a continuous and omnidirectional-controllable water delivery. This work opens an avenue for applications of anisotropic wetting surfaces, such as complex-flow distribution and liquid delivery, and extend the design approach of multi-bioinspiration integration.

Magnetoresponsive Surfaces for Manipulation of Nonmagnetic Liquids: Design and Applications

“…[4,50,[69][70][71] On the other hand, the conical shape is beneficial for droplet transport, directional rebound, switchable adhesion, and fog harvesting. On the one hand, the conical microstructures can be fabricated using facile methods, e.g., by magnetic particle-assisted molding (MPAM).…”

“…[72] Magnetic Microcilia: Living systems employ cilia to manipulate and sense the flow of fluids for locomotion, feeding, and tissue morphogenesis. [53,71,76] The widely used method for fabricating magnetic microcilia is called MPAM, which is an ingenious technique without using any molds. [53,71,76] The widely used method for fabricating magnetic microcilia is called MPAM, which is an ingenious technique without using any molds.…”

“…[75] Inspired by these motile cilia, MRSs with magnetic microcilia have also been constructed. [4,50,[69][70][71] Figure 5a gives a scheme of MPAM. [4,50,[69][70][71] Figure 5a gives a scheme of MPAM.…”

“…[71] On the superhydrophobic microcilium surface, a droplet rolled off easily along the tilt direction of microcilia, but stuck to the surface when moving against the tilt direction ( Figure 5c-c1, inclined angle ≈10°). [71] In contrast, when the microcilium surface was in the slippery state, a droplet could slide against the tilt direction of the microcilia, but could not slide in the opposite direction ( Figure 5c-c2, inclined angle ≈60°). [71] In contrast, when the microcilium surface was in the slippery state, a droplet could slide against the tilt direction of the microcilia, but could not slide in the opposite direction ( Figure 5c-c2, inclined angle ≈60°).…”

“…Figure 6f,g shows the directional advancing and propulsion behaviors of an aqueous droplet on the inclined scales. [71] Copyright 2017, Wiley-VCH. Funct.…”