Role reversal: Liquid “Cheerios” on a solid sense each other
Year: 2016
Type: article
Abstract: The Cheerios effect (1) refers to the common observation that floating objects (say, little toruses of Cheerios cereal floating on water or milk) tend to agglomerate either with each other or to the wall that contains the liquid. Floating objects distort the liquid–vapor interface due to a combination of wetting and gravity forces. The interfacial deflection due to one particle serves as a gravitational potential energy landscape for others, setting up interesting and sometimes counterintuitive long-range attraction that is potentially useful to direct interfacial self-assembly (2). In PNAS, Karpitschka et al. (3) report interesting experiments and theory in which the roles of the liquid and solid are reversed; that is, they show that liquid drops on a compliant solid surface experience attractive or repulsive interactions, a “reverse Cheerios effect.”
The Cheerios effect is an example from a class of phenomena driven by liquid–vapor surface tension interacting with solid objects. [The very fact of liquid surface tension has fascinated researchers over a long period (4, 5).] Generally, liquid contacting a solid object can wet it completely, not at all, or partially, in the last case forming an equilibrium contact angle that is governed by the surface energies of the liquid–vapor interface and the two solid–fluid interfaces. Usually, the solid in question is sufficiently stiff that its deformation plays a negligible role. On the other hand, when liquids interact with compliant structures (6), the deformability of the latter can result in large deformations of slender objects: capillary origami (7).
When the solid is deformable, its own surface stress can play an important and sometimes dominant role in many types …
[↵][1]1Email: anj6{at}lehigh.edu.
[1]: #xref-corresp-1-1
Author: Anand Jagota
Institution: Lehigh University
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Funder: U.S. Department of Energy
OpenAlex ID: W2468137693