Surfaces directing fluid flows Although surfaces can be made to attract or repel liquids using coatings, surface textures with specific curvature can also be used to achieve the same effect. However, fluid transport is usually limited by the specific pattern that only drives flow at the surface itself. Feng et al . created a dual-reentrant surface that has an asymmetric profile so that fluids spread out at the surface and subsurface layers. Furthermore, these surfaces can be designed so that different liquids will naturally steer in opposing directions simply because of their specific interactions with the surface. —MSL

Despite their simplicity, water droplets manifest a wide spectrum of forms and dynamics, which can be actuated using special texture at solid surfaces to achieve desired functions. Along this vein, natural or synthetic materials can be rendered water repellent, oleophobic, antifogging, anisotropic, etc.—all properties arising from an original design of the substrate and/or from the use of special materials promoting capillary or elastic forces at the droplet scale. Here, we report an original phenomenon occurring at the tip of asymmetric (half-flat, half-curved) pillars: Droplets reconfigure and get oriented on the curved side of these Janus tips. This local, geometry-driven effect, namely, tip-induced flipping of droplets, is found to be generic and have spectacular global consequences: Vast assemblies of Janus pillars enable a continuous, long-range, and fast self-transport of water harvested from fogs, which makes it possible to collect and concentrate droplets at different scales.

A kind of superhydrophobic magnetic nano/micropillar array (MNA) with optimized intrinsic dynamic wetting property has characteristics of magnetically induced dynamic tilt‐angle changes, which achieves the controlling of the directional droplet transport effectively. It is revealed that MNA has a low adhesive gradient along the direction of magnetically induced tilt‐angles. A tilt‐angles of nano/micropillars in the range of 0°–59° is realized by controlling the magnetic field intensity (0–490 mT), so that a droplet (10 µL) can be transported on MNA from one pillar to the next along the tilt‐angle direction. It is proposed that the continuous changes of magnetically induced dynamic tilt‐angles on MNA induce a gradient driving force to act on the droplet, in addition to cooperation with the low adhesive direction that results from unidirectional gradient discontinuous solid–liquid–gas three phase contact lines. The finding offers insight into designing of surface materials that can be extended into microfluidics for controlling of droplet motion and others.