Multimodal liquid transport enabled by crassula muscosa shoot inspired rachet-shaped leaves channel

Abstract Despite significant advances in bioinspired liquid transport systems, existing surfaces relying on static wettability gradients or asymmetric structures remain limited to single-mode transport, while achieving multimodal transport in a single channel has been overlooked. Here, inspired by the Crassula muscosa shoots, a multimodal directional ratchet channel (MDRC) is proposed, which integrates asymmetric curvature and tilt features to enable on-demand switching among four liquid transport modes: unidirectional transport in channel, bidirectional transport in channel, unidirectional transport on channel, and transport failure. The underlying mechanism of surface-tension responsiveness is revealed, where the synergy between curvature-induced Laplace pressure asymmetry and tilt-driven meniscus dynamics enables liquids (with surface tensions of 22.8 ~ 72.8 mN/m) to dictate transport modes. Crucially, by strategically leveraging the tunable flow direction and liquid height difference characteristics between transport modes, we developed a real-time surface tension sensor capable of identifying liquid surface tension across three distinct ranges: 22.8 ~ 31.5 mN/m, 35 ~ 42.5 mN/m, and approximately 55 mN/m. And the assembled MDRCs further serve as a multiphase droplet separator achieving > 95% efficiency in both oil-water and oil-oil separations. This work establishes new strategies of liquid manipulation for adaptive microfluidics, smart diagnostics, and precise separations.