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Noon Edition

What Makes Tape Sticky?

scotch tape dispenser

Here's a simple question: what makes tape sticky?

Being able to produce tape that works isn't the same as understanding the basic physics involved, but two physicists from France, named Gay and Liebler, think they've come up with an answer.

Bubbles.

It turns out, that if you view the surface of a piece of tape with a powerful microscope, it isn't flat at all. In fact, it has peaks and valleys invisible to the naked eye.

When the tape's surface is pressed down, pockets of air are trapped between the tape and whatever it's touching. Those air pockets work like a million tiny suction cups.

To pull the surface away again you'd have to stretch those air pockets. Because they are sealed off and no air can get in, the air pressure inside each bubble will decrease as its size increases. That means the greater air pressure in the room is trying to push that tape back down, and keeping it stuck. With enough force, though, you can cause a break that allows air to rush in under the tape, and that's when the tape tears away!

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