A 3D printing method which uses a new type of ink made from genetically programmed living cells for creating a “living tattoo” has been developed by the researchers from MIT. 

Electronic tattoos and smart ink technology have a tremendous potential in a wide range of various scientific fields. Lately, the researchers have been studying a big amount of materials which serve as 3D-printed ink's basis. Polymers, for example, were a great option for heat-responsive objects printing. While many experts are experimenting with materials to create the best wearable sensor device, the team of engineers from the MIT has decided to use the living cells.

The first step was to find out which type of organic cells can be used in the appropriate device because this is the key reference as the bacterium should survive in the 3D printer. These cells are engineered in such way to become activated in response to a diversity of stimuli. After the process of mixing with a sludge of nutrients and hydrogel, the cells can be printed, layer upon layer, to create three-dimensional, interactive structures and mechanisms.

The scientists have shown its technique by printing a "living tattoo", a delicate, translucent patch patterned with live bacteria tree-shaped cells. To test the patch, they spread some constituent chemicals onto the back of a person's hand, after that they pressed the hydrogel patch over the exposed skin. The bacteria in each tree branch had different functions, responding to various chemical stimuli.

At the moment this technique has not reached the peak of its development, there is a big amount of work to do. However, eventually, these bacteria can be used both for the standard of health measurement and for the developing of peculiar computer microchips. The team of engineers supposes that it is also possible to use the bacteria-printed plates for creating stickers which respond to change in temperature and concentrations of air pollutants. In conclusion, it will help the doctors to monitor their patients.