When you get a tattoo, when the tattoo needle pierces your skin up to 200 times per second, and under the guidance of a skilled artist, it can carve the dragon or lotus you’ve always wanted. Strictly speaking, however, the needle does not inject the ink into your body. Instead, as the needles are removed from the skin, each one opens a gap and sucks in the ink.
“This discovery is not new, but it could be used in this new way to develop certain vaccines.” Idera Lawal, a chemical engineer at Texas Tech University, reported at the March meeting of the American Physical Society.
Hollow hypodermic needles typically rely on positive pressure to inject vaccines. The needle penetrates under the skin or into the muscle, and the person injecting the vaccine then pushes the needle’s plunger, propelling the fluid through the needle’s resting tip.
However, Lawal says this method may not work for all types of vaccines. For example, vaccines being developed that consist of DNA are often too thick to pass through a standard hypodermic needle.
“It might be possible to deliver this vaccine through a tattoo.” That’s because the physics of a tattoo needle is very different from a hypodermic needle, Lawal said.
Unlike hypodermic needles, tattoo needles do not inject liquid after entering the skin. Instead, when the solid, ink-coated needle is lowered, it opens a small hole 2 millimeters deep. Only when the needle is pulled out of the skin does the vacuum in the small hole suck the ink into the skin.
In a video shown by Lawal, a clear gel acts as a substitute for meat. He said he could find no reference to this effect in the scientific literature – although tattoo artists are familiar with it.
“It’s a very beautiful video.” Thomas Sykes, an Oxford physicist who was not involved in the study, said Skyes noted that the data provided by Lawal showed that 10 of the 50 injections injected half of the ink. This means that for an injection volume like the vaccine, the optimal number of injections might be less. Whether your friends think vaccinations via tattoos are cool, though, remains to be seen.