Now scientists have developed a way to avoid these deterrents: a tattoo patch containing microscopic needles that can quickly color skin without causing pain or drawing blood. These single-use microneedle tattoo patches work for both color images and for markings visible only with ultraviolet illumination, according to a study published September 14 in iScience. “We’ve miniaturized the needle so that it’s painless but still effectively deposits tattoo ink in the skin,” said the senior study author, Mark Prausnitz, PhD, of the School of Chemical and Biomolecular Engineering at Georgia Institute of Technology in Atlanta, in a statement. “This could be a way not only to make medical tattoos more accessible, but also to create new opportunities for cosmetic tattoos because of the ease of administration,” said Dr. Prausnitz, an inventor of the patches who cofounded Micron Biomedical to test them and bring them to market. Up to about one-third of U.S. adults have at least one tattoo, research published in the December 2019 issue of the Journal of the European Academy of Dermatology and Venereology suggests. And so do nearly half of adults under 40 years old. Though tattoo inks are injected into the skin, they’re not regulated as medical products by the U.S. Food and Drug Administration. Instead, they’re subject to less-stringent regulations used for cosmetics. Risks of tattoos include infection — especially when needles or inks are contaminated — as well as allergic reactions. The new study wasn’t designed to test the safety or efficacy of microneedle tattoos compared with traditional application processes. Microneedles are already used for a variety of cosmetic and anti-aging products. For years, scientists have also tested microneedles as a potential needle-free way to administer medicines and vaccines, Prausnitz said. Medical tattoos are currently used to cover scars, target radiation for cancer treatments, and restore the appearance of nipples after breast surgery. There’s potential, too, to use tattoos instead of medical alert bracelets to identify people with severe allergies or serious medical conditions like diabetes or epilepsy. Tattoos normally require large needles to repeatedly puncture the skin to deposit enough ink for a good image. The new microneedles are themselves made of tattoo ink, with a dissolvable casing that enables them to create a lasting image after they’re pressed to the skin just once. To apply these microneedle tattoos, scientists crafted small molds with the microneedles arranged in a pattern forming the desired image. Then they filled the molds with tattoo ink and added a patch backing. Tattooing with these microneedles is as simple as applying the patch to the skin for a few minutes — long enough for the microneedles to dissolve and release the ink. In early tests of this approach, tattoos lasted for a full year, suggesting that this approach is likely to create permanent images. This held true for traditional tattoo ink as well as invisible inks that appear under ultraviolet light or higher temperatures — an approach that may offer more privacy to patients who want the images to be visible only under certain circumstances. It’s also possible that microneedle tattoos could be used to apply temporary ink for short-term medical needs — for example to identify the correct arm or leg for a procedure — or for cosmetic images that people don’t want to keep for a lifetime. Animals might also get microneedle patch tattoos instead of having their ears clipped or tagged for tracking. “The goal isn’t to replace all tattoos, which are often works of beauty created by tattoo artists,” Prausnitz said. “Our goal is to create new opportunities for patients, pets, and people who want a painless tattoo that can be easily administered.”
