Aerial-aquatic robots capable of crossing the air-water boundary and hitchhiking on surfaces.

Many real-world applications for robots-such as long-term aerial and underwater observation, cross-medium operations, and marine life surveys-require robots with the ability to move between the air-water boundary. Here, we describe an aerial-aquatic hitchhiking robot that is self-contained for flying, swimming, and attaching to surfaces in both air and water and that can seamlessly move between the two. We describe this robot's redundant, hydrostatically enhanced hitchhiking device, inspired by the morphology of a remora (Echeneis naucrates) disc, which works in both air and water. As with the biological remora disc, this device has separate lamellar compartments for redundant sealing, which enables the robot to achieve adhesion and hitchhike with only partial disc attachment. The self-contained, rotor-based aerial-aquatic robot, which has passively morphing propellers that unfold in the air and fold underwater, can cross the air-water boundary in 0.35 second. The robot can perform rapid attachment and detachment on challenging surfaces both in air and under water, including curved, rough, incomplete, and biofouling surfaces, and achieve long-duration adhesion with minimal oscillation. We also show that the robot can attach to and hitchhike on moving surfaces. In field tests, we show that the robot can record video in both media and move objects across the air/water boundary in a mountain stream and the ocean. We envision that this study can pave the way for future robots with autonomous biological detection, monitoring, and tracking capabilities in a wide variety of aerial-aquatic environments.

Integrated Bundle Electrode with Wettability-Gradient Copper Cones Inducing Continuous Generation, Directional Transport, and Efficient Collection of H2 Bubbles.

The hydrogen evolution reaction (HER), as an efficient process of converting various energies into high-purity hydrogen, has attracted much attention from both scientific research studies and industrial productions. However, its wide applications still confront considerable difficulties, for example, bubble coverage on the electrode and bubble dispersion in the electrolyte, which will disturb current distribution and isolate active sites from reaction ions resulting in a high reaction overpotential and large Ohmic voltage drop. Consequently, timely removing the generated gas bubbles from the electrode as well as avoiding their direct release into the electrolyte can be an effective approach to address these issues. In this work, we have developed an elegant electrode, that is, the integrated bundle electrode with wettability-gradient copper cones, which is endowed with the multifunctions of continuous generation, direct transport, and efficient collection of hydrogen bubbles. All processes are proceeding on the electrode, which not only remove the generated hydrogen bubbles efficiently but also prevent the hydrogen bubbles from releasing into the electrolyte, which should greatly advance the development of water electrolysis and offer inspirations for people to fabricate more efficient HER devices.

Durable Underwater Superoleophobic Coatings via Dispersed Micro Particle-Induced Hierarchical Structures Inspired by Pomfret Skin.

Underwater superoleophobic materials due to its excellent antioil and self-cleaning performance have attracted tremendous attention. Current underwater superoleophobic surfaces usually use complex methods to construct the surface structure limiting the yield and not suitable for large-scale production. Here, inspired by the superoleophobicity of pomfret skin, we developed a strategy to fabricate superoleophobic coatings with hierarchical micro/nano structures by doping hydrophilic micro silica particle in calcium alginate hydrogel. The introduction of micro particles significantly reduces the adhesion of oil and improves the mechanical properties of the coatings. The prepared coatings also survived in high temperature and high salinity environment and the dried for free-standing films. The free-standing dry coating films can be used like wallpaper to decorate the targeted surface and endow them with underwater superoleophobicity. We expect that this work will provide a new method for designing underwater superoleophobic coatings and the wallpaper-like coating films allow large-scale production and will also promote the commercialization of oil-repellent materials.