Controllable Bubble Transport on Bioinspired Heteromorphic Magnetically Steerable Microcilia

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.