Multimodal liquid transport enabled by <i>Crassula muscosa</i> shoot inspired ratchet-shaped leaves channel

Abstract

Despite advances in bioinspired liquid transport systems, most reported surfaces relying on static wettability gradients or asymmetric structures are limited to single-mode transport, while multimodal transport within a single channel remains largely unexplored. Inspired by Crassula muscosa shoots, we propose a multimodal liquid transport channel (MLTC) that integrates asymmetric curvature and tilt features to enable on-demand switching among four liquid transport modes: (I) unidirectional transport in channel, (II) bidirectional transport in channel, (III) unidirectional transport with a protruding liquid film on channel, and (IV) transport failure. The surface-tension responsiveness mechanism is elucidated, where the synergy between curvature-induced Laplace pressure asymmetry and tilt-driven meniscus dynamics governs transport behavior, allowing liquids with surface tensions ranging from 22.8 to 72.8 mN/m to autonomously select transport modes. Leveraging the tunable flow direction and liquid height differences among modes, a real-time surface-tension sensor is demonstrated, capable of distinguishing liquids within three ranges: 22.8–31.5, 35–42.5, and ∼55 mN/m. Furthermore, assembled MLTCs further function as droplet separators, achieving &amp;gt;95% efficiency for both oil–water and oil–oil separations. This work introduces a multimodal liquid manipulation strategy, offering new opportunities for adaptive microfluidics, smart diagnostics, and precise liquid separation.