Tag: surface tension

Why Do Coffee Rings Form? Because the Grounds are Round

By Veronique Greenwood | August 17, 2011 1:00 pm

coffee ring
Those dark rings in the bottom of your cup arise from fundamental physics.

What’s the News: Some of the most mundane things in life—drinking through a straw, for instance, or washing your hands with soap—are the results of some really neat physics. Today, scientists are adding another item to that list: The ring that forms around a drying drop of coffee. A team at University of Pennsylvania has discovered that that brown ring is a result of the shape of the particles floating in your coffee—and if you squash them out a little, the coffee ring disappears.

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CATEGORIZED UNDER: Physics & Math, Top Posts

With a New Chip, Scientists Use Chemistry to Identify Fluids (And Write Secret Messages)

By Veronique Greenwood | August 4, 2011 1:38 pm

wink
Each fluid reveals a different letter.

What’s the News: Scientists have developed a chip that can instantaneously identify fluids applied to it, just from their unique surface tension. In a handheld device, it could help toxic site remediators figure out what that ominous clear liquid is. And there’s a bonus for the kids-in-the-treehouse user demographic: different secret messages can appear on the chip depending on what fluid is applied.

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CATEGORIZED UNDER: Technology, Top Posts
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