A TEAM OF engineers at MIT university have developed a new 3D printing technique by genetically modifying cells to create a “living tattoo” that can respond to a variety of stimuli.

The cells are engineered to light up in response to a variety of stimuli. When mixed with a slurry of hydrogel and nutrients, the cells can be printed, layer by layer, to form three-dimensional, interactive structures and devices.

The team has demonstrated its breakthrough by printing a living tattoo onto the skin of people.

The living tattoos are a thin, transparent patch patterned with live bacteria cells in the shape of a tree. Each branch of the tree is lined with cells sensitive to a different chemical compound.

When the patch is printed on someone’s skin that has been exposed to the same compounds, areas of the tree light up in response.

The researchers say their technique can be used to fabricate “active” materials for wearable sensors and interactive displays. These materials can be used to sense environmental chemicals and pollutants as well as changes in pH and temperature.

From tattoos to living computers

The researchers also engineered bacteria to communicate with each other. For instance, they programmed some cells to light up only when they receive a certain signal from another cell.

Researcher Hyunwoo Yuk said in the future, researchers may use the team’s technique to print “living computers” – structures with multiple types of cells that communicate with each other, passing signals back and forth, much like transistors on a microchip.

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

For more near-term applications, the researchers are aiming to fabricate customised sensors in the form of flexible patches and stickers that could be engineered to detect a variety of chemical and molecular compounds.

They also hope their technique may be used to manufacture drug capsules and surgical implants, containing cells engineered to produce compounds such as glucose, to be released therapeutically over time.

The research has been published in the Advanced Materials journal.

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