Superhydrophobic surfaces have promised tremendous applications in living and industrial areas for the past two decades. Real applications, however, meet challenges, with the central concern being the robustness to resist mechanical abrasions and impacts. Here, a revolutionary strategy is proposed to create a microskeleton-nanofiller (MSNF) film with exceptionally mechanical superstable superhydrophobicity. The strategy is conceptually different from the traditional superhydrophobic 3D microskeleton, because a 3D microskeleton is used to completely fill in the infused superhydrophobic medium. The resulting MSNF film can reserve superhydrophobicity under not only continuous abrasion before the complete wearing off the film, but also Taber abrasion, knifescratch, and cyclic tape peels. In addition, the MSNF film enables damage resistance to heavy impact at least up to a kinetic energy of ≈40.2 J. Furthermore, the MSNF film is also superamphiphobic to prevent oil contamination and can reserve the superhydrophobicity under large bending or torsion. Together with robustness and scalability, the MSNF film will be useful in automobiles, ships, aircraft, and houses in harsh environments and the strategy can extend to various inexpensive structured materials (such as porous iron).

A falling liquid drop, after impact on a rigid substrate, deforms and spreads, owing to the normal reaction force. Subsequently, if the substrate is nonwetting, the drop retracts and then jumps off. As we show here, not only is the impact itself associated with a distinct peak in the temporal evolution of the normal force, but also the jump-off, which was hitherto unknown. We characterize both peaks and elucidate how they relate to the different stages of the drop impact process. The time at which the second peak appears coincides with the formation of a Worthington jet, emerging through flow focusing. Even low-velocity impacts can lead to a surprisingly high second peak in the normal force, even larger than the first one, namely when the Worthington jet becomes singular due to the collapse of an air cavity in the drop.

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Smart textiles are attracting great interest. Particularly, airconditioning textiles are highly desired for their merits in energy conservation and personal temperature/humidity management. Currently, airconditioning textiles can be fabricated by two strategies. One uses infrared-radiation-adaptive materials, and the other uses moisture-responsive actuators that can regulate temperature and humidity simultaneously. Here, the fabrication of a silk-yarn switch comprising electrospun highly aligned nanofibers is reported and its application in airconditioning textiles is demonstrated. Silk yarn rotates in contact with liquid, and can be recovered by drying. The different responses and wetting behaviors of the switch to H 2 O and C 2 H 6 O is investigated. It is argued that alignment and surface hydrophilicity of nanofibers play important roles in this term. To elaborate, actuating trait is mainly controlled by reduction of the surface free energy of aligned silk nanofibers, during the wetting process. As proof of concept, the application of the sweat-driven silk-yarn switch in regulating the temperature/ humidity of the human body is demonstrated in this work. Considering the large production, versatile processibility, and good biocompatibility, silk actuator may have practical applications in designing smart switches (or valves) for intelligent textiles, artificial muscles, and other application scenarios.

An analytical model is proposed for the Young-Laplace equation of two-dimensional (2D) drops under gravity. Inspired by the pioneering work of Landau & Lifshitz (1987), we derive analytical expressions of the profile of drops on flat surfaces, for arbitrary contact angles and drop volume. We then extend our theory for drops on inclined surfaces and reveal that the contact line plays a key role on the wetting state of the drops: (1) when the contact line is completely pinning, the advancing and receding contact angles and the shape of the drop can be uniquely determined by the predefined droplet volume, sliding angle and contact area, which does not rely on the Young contact angle; (2) when the drop has a movable contact line, it would achieve a wetting state with a minimum free energy resulting from the competition between the surface tension and gravity. Our theory is in excellent agreement with numerical results.