Crassula-inspired surface architecture for programmable liquid navigation

The directional transport of liquids is ubiquitous in natural energy transfer processes and essential for microfluidics and flexible electronics. However, achieving stable and programmable control over liquid transport remains a challenge. Here, we developed a 3D-printed Crassula-inspired surface architecture (CISA) that enables switching of preferential liquid spreading between longitudinal and transverse directions by tuning its structural parameters. Experiments spanning varied liquid surface tension and surface wettability reveal that transport behavior is controlled by the coupled effects of structural parameters and solid-liquid interfacial wettability, rather than structural parameters alone. To further extend transport capabilities to high surface tension liquid metals, the CISA was modified with CuGa₂, where the combined effects of metallic-bond-enabled wetting and in situ oxide layer dissolution trigger a controllable wettability switch, allowing precise directional transport of eutectic gallium-indium (EGaIn) fluids. Notably, CISA demonstrates significant potential in anti-gravity transport, programmable routing, and microfluidic reactions, providing a versatile design strategy for next-generation flexible devices and integrated microfluidic systems.