Abstract
Millimeter-sized objects trapped at a liquid surface distort the interface by their weight, which in turn attracts them towards each other. This ubiquitous phenomenon, colloquially called the “Cheerios effect” is seen in the clumping of cereals in a breakfast bowl, and turns out to be a highly promising route towards controlled self-assembly of colloidal particles at the water surface. Here, we study capillary attraction between levitating droplets, maintained in an inverse Leidenfrost state above liquid nitrogen. We reveal that the drops spontaneously orbit around each other – mirroring a miniature celestial system. In this unique situation of negligible friction, the trajectories are solely shaped by the Cheerios-interaction potential, which we obtain directly from the droplet’s dynamics. Our findings offer an original perspective on contactless and contamination-free droplet cryopreservation processing, where the Leidenfrost effect and capillarity would be used in synergy to vitrify and transport biological samples.
Highlights
The Cheerios effect is an everyday-life phenomenon that can be seen in the clumping of cereals in a bowl or that of bubbles at the surface of a sparkling liquid
The Cheerios effect offers a simple strategy for self-assembly of colloids[9,10], controlled by tuning the shape[11] or b wetting properties of the particles[12]
Capillary interactions play a crucial role in the life of water walking creatures and pond vegetation[4,5], and are used to reach food, escape predators[13] and disperse seeds[14]
Summary
1234567890():,; The Cheerios effect is an everyday-life phenomenon that can be seen in the clumping of cereals in a bowl or that of bubbles at the surface of a sparkling liquid. The origin a of the interaction between floating objects lies in the distortion of the liquid surface[1,2,3], which typically generates attractive forces[4,5,6,7,8]. The floating bodies form an intriguing microcosm that is reminiscent of general relativity. Such a comparison has been suggested before, and the long-range interaction between colloids has been proposed as a way to mimic the gravitational collapse of galaxies[15]. In by-passing the drag we push the comparison further: we show that levitating particles submitted to capillary attraction f follow a variety of intricate orbits. The trajectories, shaped by the Cheerios interaction potential fundamentally differ from the usual Newtonian conics.
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