If you're going to try "tattooing" a microscopic animal, it would make sense to select one of the toughest creatures on the planet. That's exactly what scientists have done with the tardigrade, and the tech they used could have some valuable real-world applications.
Also known as water bears and moss piglets, tardigrades are pudgy eight-legged micro-animals that typically grow no larger than half a millimeter in length. Along with having become a pop cultural sensation, they are widely known for their ability to withstand extreme cold, heat, dryness, and even the vacuum of outer space.
This reputation made the animals a natural choice for Ding Zhao, Min Qiu and colleagues at China's Westlake University, who wanted to test a method of printing patterns onto living microorganisms without harming them.
Among other things, the technology may one day be used to create cyborg micro-robots that perform biomedical functions via sensors or other electronics printed directly onto their bodies. The tech might also have applications in fields such as cryopreservation and astrobiology.
For their study, the scientists started by slowly dehydrating live tardigrades, thus putting them in a state of suspended animation. Each creature was then placed on a sheet of carbon-composite paper which got cooled to a temperature of -226 ºF (-143 ºC). Next, the tardigrade was covered with an organic liquid known as anisole, which froze into a thin layer of ice.
When an electron beam was subsequently focused onto specific areas of the animal's body, the frozen anisole in those locations reacted by forming into a new biocompatible chemical.
As the tardigrade was then warmed back to room temperature within a vacuum, that chemical firmly adhered to the creature's outer cuticle, forming a visible pattern. The rest of the anisole ice, which had not been exposed to the electron beam, disappeared by transforming directly into vapor.
When rehydrated, approximately 40% of the tardigrades survived and became active again, showing no signs of being bothered by the tattoos. It is believed that the survival rate should significantly improve as the technique is refined. And importantly, the markings remained stable even after stretching, immersion in solvent, rinsing and drying.
"Through this technology, we’re not just creating micro-tattoos on tardigrades – we’re extending this capability to various living organisms, including bacteria," says Zhao.
The research is described in a paper that was recently published in the journal Nano Letters.
Source: American Chemical Society
