For all the world’s technological progress, tattooing has remained largely unchanged: you use a needle to puncture the skin and inject ink, creating the desired design and color in the process. Now, Dutch researchers have developed a micro-injection tattoo machine that doesn’t require any needles at all. It’s clean, non-painful, and produces less waste than traditional methods.

Futuristic tattoos

Humanity’s desire for tattoos goes back a long time. Ötzi the Iceman, who’s over 5000 years old, had dozens of simple tattoos on his body. More than a third of the global population (38%) has at least one tattoo — and 3/4 of those who do, have more than one. However, tattooing is still insufficiently regulated. The ink can produce dangerous reactions, many parlors don’t provide proper hygiene, and needles damage the skin, producing pain and potentially localized injuries. Scientists’ interest in tattoos also follows a different avenue: in the not-too-distant future, tattoos might be used for medical purposes.

With all this in mind, researchers of the University of Twente have developed a micro-jet injection technology that doesn’t use needles at all. Instead, an ultrafast liquid jet the thickness of a human hair is used to penetrate the skin. In a new paper, David Fernández Rivas and his colleagues compare this new approach with classic needle technology, using high-speed imagery.

The technique starts with a laser that rapidly heats a fluid inside a microchannel on a glass chip. This fluid is heated above its boiling point, causing a vapor bubble to forms and grows, pushing the liquid out at speeds of up to 100 meters per second (360 km/h). The jet is capable of going through the human skin, and yet it produces almost no pain.

“You don’t feel much of it, no more than a mosquito bite”, say Fernandez Rivas. A short video interview with him can be found here.

Painless and eco-friendly

The researchers worked with a number of commercially available inks, finding that their method minimizes skin damage. Not only was the device relatively painless, but it also used less energy than conventional needles, and produced less waste, as there is no loss of fluids. The risk of contaminated needles is also eliminated.

Of course, this is still the early stages. The volume of the delivered jet needs to be increased, and so far, the technique can only deliver a single color. However, the results are quite promising. Researchers are confident they can produce a reliable and useful needle-free tattoo machine in a reasonable period of time.

In addition to aesthetic purposes, researchers also want to use tattoos for medical applications. The ink could serve as a sort of sensor, responding to substances or stimuli, indicating health hazards. In a separate study, researchers have also suggested that tattoos could be used in vaccination.

The study ‘High speed imaging of solid needle and liquid micro-jet injections’, by Loreto Oyarte Gálvez, Maria Brió Péreze en David Fernández Rivas, was published in Journal of Applied Physics