Achieving well-controlled directional steering of liquids is of great significance for both fundamental study and practical applications, such as microfluidics, biomedicine, and heat management. Recent advances allow liquids with different surface tensions to select their spreading directions on a same surface composed of macro ratchets with dual reentrant curvatures. Nevertheless, such intriguing directional steering function relies on 3D printed sophisticated structures and additional polishing process to eliminate the inevitable microgrooves-like surface deficiency generated from printing process, which increases the manufacturing complexity and severally hinders practical applications. Herein, we developed a simplified dual-scale structure that enables directional liquid steering via a straightforward 3D printing process without the need of any physical and chemical post-treatment. The dual-scale structure consists of macroscale tilt ratchet equipped with a reentrant tip and microscale grooves that decorated on the whole surface along a specific orientation. Distinct from conventional design requiring the elimination of microgrooves-like surface deficiency, we demonstrated that the microgrooves of dual-scale structure play a key role in delaying or promoting the local flow of liquids, tuning of which could even enable liquids select different spreading pathways. This study provides a new insight for developing surfaces with tunable multi-scale structures, and also advances our fundamental understanding of the interaction between liquid spreading dynamics and surface topography.

Engineering materials serving in marine surroundings are inevitably corroded. The corrosive marine conditions can also be utilized to harvest kinetic ocean wave energy to solve this problem. Leveraging water–solid triboelectrification to harvest low-frequency wave energy for active anticorrosion is promising. Existing techniques are efficient in harnessing environmental energy with frequencies higher than 3 Hz, whereas the dominated ocean waves with optimal wave spectral density fluctuate from 0.45 to 1.5 Hz. Herein, we proposed a highly efficient and sustainable blue energy-powered cathodic protection (BECP) strategy by fusing water–solid triboelectric nanogenerators and cathodic protection technology. Leveraging the highly efficient triboelectrification between the moving water and hydrophobic fluorinated ethylene propylene tube, we developed the built-in power module, enabling the harvest of ocean wave energy lower than 1.5 Hz. The generated volumetric current density is 28.9 mA·m⁻³, 5–20 times higher than the values of the reported devices. Moreover, the proposed BECP performs comparably to conventional cathodic protection in corrosion inhibition. Significantly, the proposed approach can be easily applied to ships, buoys, and other offshore platforms to simultaneously realize blue energy harvesting and engineering material protection, providing an alternative to traditional active protection technology.

Friction is a fundamental force that impacts almost all interface-related applications. Over the past decade, there is a revival in our basic understanding and practical applications of the friction. In this review, we discuss the recent progress on solid–liquid interfacial friction from the perspective of interfaces. We first discuss the fundamentals and theoretical evolution of solid–liquid interfacial friction based on both bulk interactions and molecular interactions. Then, we summarize the interfacial friction regulation strategies manifested in both natural surfaces and artificial systems, focusing on how liquid, solid, gas, and hydrodynamic coupling actions mediate interfacial friction. Next, we discuss some practical applications that are inhibited or reinforced by interfacial friction. At last, we present the challenges to further understand and regulate interfacial friction.