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Ever Wonder How Bandaids Can Create Light?

One evening after gymnastics, my daughter opened a Band-Aid in the dark back seat of our car. She noticed, to her amazement, a brief glow of blue light. I didn't see it but I had seen something similar once, while unwrapping a nose strip in the dark, in the middle of the night. I wondered what was going on.

Many commenters of the above videos refer to this phenomenon as triboluminescence. The "tribo" comes from the Greek "tribein" meaning to rub. Related terms are fractoluminescence and mechanoluminescence, referring to generating light by breaking things apart or by similar mechanical means. They seem perhaps more appropriate, but triboluminescence seems to get more usage. But as physicist Richard Feynman has said, there is a "difference between knowing the name of something and knowing something."

Way back in the 17th century, philosopher Francis Bacon reported that crushing sugar crystals gives off light. This also occurs in quartz and other minerals. A more recent reboot involves Wint O Green lifesavers, in which the wintergreen oil (methyl salicylate) absorbs the higher frequency photons from the sugar reaction to give off the lower frequency blue-green light

In addition to the wrappers, triboluminescence occurs in certain brands of duct tape and Scotch tape. I have also seen it with Post-It Notes. Tape consists of four components: backing, which is the tape itself, a primer on the backing to help the adhesive stick to it, an adhesive for the sticking to the target thing, and a release coating, on top of the adhesive so it doesn't stick to itself when it's rolled up. Adhesives in tape are pressure sensitive. They need to stick to what's applied (adhesion) and to itself (cohesion). 

Van der Waals forces work at close proximity between molecules with different charges. When the adhesive gets pulled apart, electrons become excited and give off photons, similar to when the sugar gets crushed. These excite nitrogen molecules in the air and release light, some of it visible. It's not very bright, so you need to be in the dark with your eyes adjusted to see it happen. The light is brighter if you attach and pull apart the two sticky faces rather than off the roll, although that still works. Researchers at UCLA set up a mechanized device to unpeel a roll of Scotch tape in a vacuum (so no Nitrogen atoms get in the way) and found it released enough x-rays to x-ray a finger.

If you can shed some light on this subject, please share your comments below. To paraphrase Eleanor Roosevelt, "It is better to generate triboluminescence than curse the darkness." 

Still curious? Have you ever wondered about those air puff tests at the eye doctor?  Or have you wondered about fly swarms