Weird effect: By unwinding an entire roll of tape in a vacuum the researchers were able to produce enough radiation to X-ray a finger.

Credit: UCLA/Juan Escobar

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SYDNEY: Unwinding household sticky tape in a vacuum emits radiation strong enough to X-ray a human figure, according to a new study in the British journal Nature.

Researchers at the University of California, Los Angeles (UCLA), have measured the energy emitted from peeling scotch tape off the roll and found that it peaked at 15-keV and was emitted in short, sharp bursts.

"We didn't believe it. We really didn't think it could be true," said co-author Carlos Camara, referring to the team's initial scepticism. "We took some pictures of our hands to see the bones and prove that it was possible. We have a whole collection (of pictures)... it is absolutely remarkable."

Older Soviet study

"We were happily surprised," added team-mate Juan Escobar, who said he wasn't sure what to expect from sticky tape and was initially sceptical about 60-year-old Russian work that hinted at the effect.

In the 1930's scientists investigating triboluminescence (the phenomenon observed when relative motion between two contacting surfaces emits visible light) documented light being emitted when sticky tape was unrolled.

Following this, Soviet scientists reported in the 1950s that sticky tape, when separated at the right speed, released pulses in the X-ray part of the energy spectrum, but nobody has since attempted to test the claims.

Now, the UCLA team have measured the energy using an X-ray detector and confirmed that the energy and the length of the flashes seen goes beyond anything recorded before. To create the effect, the team used a machine that unrolled the sticky tape at around three cm/s and placed it in a vacuum to reduce the interference of gas particles between the tape and the X-ray detector.

Cheaper X-ray machines

Escobar told Cosmos Online that unwinding sticky tape follows the basic principles of tribocharging. He says that as the tape peels, a charge builds between the opposite charges of the sticky adhesive and the tape and creates an electric field.

At reduced pressure in a vacuum, this accelerates electrons on the adhesive to very high speeds and when they whack into the positively-charged tape roll, X-rays result. The pulses last for a billionth of a second, with an intensity of 100 milliwatts.

The researchers argue that, baring the complications of requiring a vacuum, tribocharging could have practical applications, including the development of cheaper X-ray machines. "It could be possible to create inexpensive x-ray machines for third world countries where electricity is expensive," said Escobar.

"One gets electrical discharges from many kinds of frictional processes," commented Richard Welberry a physical chemist and radiation expert at the Australian National University in Canberra. This study helps to provide "a better understanding of basic physical processes," he said, though he doubted it could be used as a new way to generate X-rays for medical applications.