#self-propulsion

Icebergs have long served as a metaphor for not knowing what's going on beneath the surface. Studies like today's are a reminder of why that is.  (Image and research credit: M. Berhanu et al.; via APS)

Inspired by the roaming rocks of Death Valley, researchers went looking for ways to make ice discs self-propel. Leidenfrost droplets can self-propel on herringbone-etched surfaces, so the team used them here, as well. (Image and research credit: J. Tapochik et al.; via Ars Technica)

Drip some ethanol on a hot surface, and you'd expect it to spread into a thin layer and evaporate. But that doesn't always happen, and a recent study looks at why. (Image and research credit: P. Kant et al.; via APS Physics) Read the full article

Water droplets immersed in a mixture of oil and surfactants will move about, propelled by the Marangoni effect. Surfactant molecules congregate along the interface between the water and oil, but they do not do so uniformly. (Image credits: top - P. Godfrey, others - S. Suda et al.; research credit: S. Suda et al.; via APS Physics) Read the full article

Robust, self-cleaning surfaces are a holy grail for many engineers, but they're tough to achieve. One necessary ingredient for a self-cleaning surface is the ability to shed water, which is why superhydrophobic coatings and surface treatments are popular. Here, researchers prompt their droplets to move at speeds up to 16 cm/s by dropping them onto a thin layer of heated oil. (Image and research credit: V. Leon and K. Varanasi; via APS Physics) Read the full article

Flocks of birds and schools of fish swarm in complicated collective motions, but groups of non-living components can move collectively, too. In this Lutetium Project video, we learn about grains that, when vibrated, self-propel and form complex collective motions similar to those seen in groups of living organisms. (Video and image credit: The Lutetium Project; research credit: G. Briand et al.) Read the full article