Researchers have created what they call a “living tattoo” using ink made from bacteria cells.

The hi-tech body art contains microbe cells that have been genetically modified, allowing it to act as a sensor by glowing green when it detects a change in the environment.

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The researchers say these living tattoos could be used as a wearable device to sense pollutants in the air or track changes in the temperature.

Developed by MIT engineers, the tattoo was “printed” layer-by-layer on a patch before being adhered to the skin.

The researchers designed the tattoo to make it more tree-like, with each section of the tree’s branches containing bacteria sensitive to certain types of chemicals.

World's first living tattoo.
The engineers designed the tattoo in the shape of a tree (MIT/Advanced Materials/YouTube screenshot)

To demonstrate the bioink’s abilities, the team used those chemicals on a person’s skin and placed the “living tattoo” on top.

When the branches came in contact with the chemicals, the bacteria in them were triggered to glow a fluorescent green.

The team say their technique can be used to create “active materials” for wearable sensors – to perform functions such as sense environmental chemicals and pollutants as well as changes in pH and temperature.

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The concept of 3D printing cells isn’t new. In recent years, scientists have tried to print genetically engineered cells of mammals without much success.

Study author Hyunwoo Yuk said: “It turns out those cells were dying during the printing process, because mammalian cells are basically lipid bi-layer balloons.

World's first living tattoo.
The team genetically engineered bacteria cells to glow a fluorescent green (MIT/Advanced Materials/YouTube screenshot)

“They are too weak, and they easily rupture.”

The MIT team decided to revisit the concept using bacterial cells instead because they are hardier and able to survive relatively harsh conditions.

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Yuk says their technology could be developed further to, one day, build “living computers” made up of different types of bacteria cells that communicate with each other by passing signals back and forth – “much like transistors on a microchip”.

He said: “This is very future work, but we expect to be able to print living computational platforms that could be wearable.”

He also believes that technology could have other uses as well, like, for example, produce drugs.

Yuk added: “We can use bacterial cells like workers in a 3D factory. They can be engineered to produce drugs within a 3D scaffold, and applications should not be confined to epidermal devices.

“As long as the fabrication method and approach are viable, applications such as implants and ingestibles should be possible.”

The research is published in the journal Advanced Materials.

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