In a bowl of breakfast cereal, principles of attraction on display

May 17, 2013
In a bowl of breakfast cereal, principles of attraction on display
Credit: Shutterstock

Andong He saw a phenomenon at work in his breakfast bowl that he couldn't explain. It prompted this question: How does cereal shape influence the way cereals floating in the milk join?

The Yale postdoctoral student offers an answer, along with collaborators Khoi Nguyen and Shreyas Mandre of Brown University, in a new paper published May 14 in Europhysics Letters.

"Two floating objects, when they attract each other, will try to maximize the area of contact," said He, of Yale's Department of & Geophysics. "Think about two ellipses—instead of tip to tip, they will try to align so that they are side to side."

The main reason for this tendency is that floating objects (pieces of cereal, for example) experience the so-called capillary force, which emerges from the natural attraction of a liquid's molecules to the molecules of an adjacent solid. A lone object afloat on an infinite surface will not move, because the total force is zero. But when there are several objects in the liquid, a net force acting on each causes them to move and ultimately join.

As the capillary force brings objects together, the associated torque further tends to maximize contact by rotating the objects, although rotating is not the only way. "If the objects are smooth enough, they can slide along each other," said He. "But the overall trend is always to decrease the gap between the objects, maximizing shared surface area as much as possible."

In an experiment, the authors used thin plastic sheets, with and without polished edges, and observed rotating and sliding motion.

The results could help explain patterns formed by a wide variety of floating objects, including micrometer-sized colloidal particles, aquatic plant seeds, and water striders.

The Yale-Brown team also worked out the fundamental principle of attraction in a new regime—that is, when floating objects are very close to each other. This could serve as a conceptual basis for addressing problems in materials processing and microelectronics, such as self-assembly of objects by flotation and geometrically controlled coagulation.

The researchers detail their theory and experiment in the paper, "Capillary interactions between nearby interfacial objects."

Said He, "You will never think of your breakfast in the same way again."

Brown University and The Nordic Institute for Theoretical Physics provided support for the research.

Explore further: It's particle-hunting season! NYU scientists launch Higgs Hunters Project

More information: iopscience.iop.org/0295-5075/102/3/38001

Related Stories

One size cloaks all

Nov 21, 2012

A metamaterial invisibility cloak that can adapt to hide different sized objects is demonstrated by in Nature Communications this week. The findings represent a useful advance for more practical applications of metamaterial cloaki ...

Invisibility cloaking to shield floating objects from waves

Nov 19, 2012

A new approach to invisibility cloaking may one day be used at sea to shield floating objects – such as oil rigs and ships – from rough waves. Unlike most other cloaking techniques that rely on transformation optics, ...

Recommended for you

Particles, waves and ants

16 hours ago

Animals looking for food or light waves moving through turbid media – astonishing similarities have now been found between completely different phenomena.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

SolidRecovery
1 / 5 (2) May 17, 2013
"You will never think of your breakfast in the same way again."

Just goes to show you all the unknowns you interact with everyday. There is a lot of research out there to work on if you are more observant.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.