Physics of Fluids Group and Max Plank Center Twente. Mesa + Institute and Faculty of Science and Technology, J.M. Burgers Centre for Fluid Dynamics and Max Plank Center Twente for Complex Fluid Dynamics, University of Twente, P.O. Box 217, 7500 AE, Enschede, The Netherlands.
Nat Commun. 2019 Sep 2;10(1):3947. doi: 10.1038/s41467-019-11850-1.
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.
毫米大小的物体在液体表面受重力影响而发生变形,这转而又会使它们相互吸引。这种普遍存在的现象,俗称“Cheerios 效应”,在早餐碗中麦片结块的现象中可见一斑,而它实际上是在水面上控制胶体粒子自组装的很有前途的途径。在这里,我们研究了在液氮上方的反 Leidenfrost 状态下悬浮的液滴之间的毛细吸引力。我们揭示了液滴会自发地相互环绕——这反映了一个微型天体系统。在这种摩擦力可以忽略不计的独特情况下,轨迹完全由 Cheerios 相互作用势能决定,我们可以直接从液滴的动力学中获得该势能。我们的发现为无接触和无污染的液滴冷冻保存处理提供了一个新视角,其中 Leidenfrost 效应和毛细作用将协同作用以将生物样本玻璃化并运输。