Tardigrades take extreme living to another level, thriving in the toughest conditions. These animals (nicknamed “water bears” for their rotund figure) live practically everywhere and can endure any ordeal thrown their way, from subzero temperatures to cosmic radiation. This unparalleled durability is what makes them the perfect candidate for microscopic tattoos, as shown in a new study published in the American Chemical Society’s Nano Letters.

In this study, researchers have revealed a way for tardigrades to be tattooed, but not just for style points. The tiny tattoos given to the creatures were meant to test a procedure that could create micro- and nanoscale devices for living matter, a crucial advancement for biomedical fields.

Read More: Can the Cute Tardigrade Survive in Space?

Creating Micro-Tattoos on Tardigrades

The researchers involved with the study depended on tardigrades’ top-notch survivability to see how a living creature would react to a manufacturing process at the microscopic level, called microfabrication.  

Microfabrication has been used to build miniature structures, like microchips, solar cells, and even biosensors that can detect cancerous cells, according to a statement on the study. It could also play a crucial role in medical technology, aiding drug delivery and tissue engineering. However, efforts to make this technology biocompatible are still underway — and that’s where the tardigrade tattoos come in.

To test microfabrication on tardigrades, the researchers turned to ice lithography, a process that uses an electron beam to carve a pattern into a thin layer of ice coating the living tissue. Once the ice sublimates (changes into a gaseous state), the tissue is left bearing the freshly engraved design. 

“Through this technology, we’re not just creating micro-tattoos on tardigrades — we’re extending this capability to various living organisms, including bacteria,” said co-author Ding Zhao, a researcher at Westlake University in China, in a press release. 

Tardigrades in Cryptobiosis

The researchers started the tattooing process by first dehydrating tardigrades so that they would enter cryptobiosis, a state in which all metabolic processes stop and the organism is rendered entirely inactive. They then put an individual tardigrade on a sheet of carbon-composite paper, which they cooled below negative 226 degrees Fahrenheit before blanketing the dormant water bear with a layer of anisole (an organic compound that smells like anise). 

As an electron beam hit the anisole and drew a pattern, it created another chemical compound that adhered to the tardigrade at higher temperatures. The tardigrade subsequently warmed to room temperature and was rehydrated, coming back to life with a brand new tattoo. 

An Exciting Era for Microfabrication

The resulting tattoos came in several shapes, such as squares, dots, and lines. The ice lithography procedure left around 40 percent of the tardigrades alive, leading the researchers to state that it could improve with more testing. 

However, it seems the surviving tardigrades weren’t bothered at all by their tattoos, since they displayed no changes in behavior. The success of this technique brings encouraging results for microfabrication on living tissue, even beyond tardigrades. 

“It is challenging to pattern living matter, and this advance portends a new generation of biomaterial devices and biophysical sensors that were previously only present in science fiction,” said Gavin King, a University of Missouri physicist credited with inventing the ice lithography technique, who was not involved in this study, in the press release.

Read More: Tardigrades, or Water Bears, May Help Unlock Slowing the Aging Process in Humans

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Jack Knudson is an assistant editor at Discover with a strong interest in environmental science and history. Before joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously interned at Recycling Today magazine.