Controllable Bubble Transport on Bioinspired Heteromorphic Magnetically Steerable Microcilia

Abstract

Controllable transport of underwater gas bubbles is essential in various fields such as gas energy, drug delivery, and heat transfer. Although anisotropic structures are used to transport bubbles, their motion direction can only be adjusted to a limited extent because of weak structural anisotropy and small responsive deformation. Here, anisotropic bubble transport is found on microcilia surfaces of diving beetle's elytra with regular inclination and heteromorphic structure of microcilia, which have hooked tips and crescent‐shaped roots. Inspired by these, a magnetically steerable microcilia surface with large‐range inclination adjustment is proposed for highly controllable bubble transport via a heterogeneous configuration strategy. The dynamic in situ microscopic behavior shows a novel shifting phenomenon of the maximum bubble pinning position from bubble back interface for hydrophobic cilia to front interface for hydrophilic cilia under different cilium wettabilities. This shift varies the bubble shapes from unstable stretching to stable compression, thus increasing the difference in anisotropic transport by three times for hydrophilic cilia. Moreover, bioinspired heteromorphic structures can further enhance such difference by 5.5 times. Based on the proposed theory, several smart functional microcilia are designed to achieve more complex bubble manipulation, thus improving their suitability for widespread application.

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“…The transportation of gas in aqueous environments holds significant importance in scientific and industrial domains, including applications in microbioreactors, , catalytic reactions, , oxygen resupply, tunable flotation, electrolytic hydrogen production, and other related areas. Most techniques for manipulating underwater bubbles primarily focus on altering the shape of the solid surface, such as planes, − wires, , or cones, − as well as adjusting the surface’s wettability. − These particular solid surfaces create conditions of either attraction or constraint on bubbles, which are then subject to various driving forces to achieve directional bubble transport. These forces can be broadly categorized into three main groups: buoyancy, ,, Laplace pressure, ,− and external force. , The buoyancy driving force in the first category can be easily controlled by altering the inclined angle of the substrate .…”

“…Most techniques for manipulating underwater bubbles primarily focus on altering the shape of the solid surface, such as planes, − wires, , or cones, − as well as adjusting the surface’s wettability. − These particular solid surfaces create conditions of either attraction or constraint on bubbles, which are then subject to various driving forces to achieve directional bubble transport. These forces can be broadly categorized into three main groups: buoyancy, ,, Laplace pressure, ,− and external force. , The buoyancy driving force in the first category can be easily controlled by altering the inclined angle of the substrate . Moreover, the effective length of the three-phase contact line is the determining factor in bubble manipulation .…”