New 3D printed 'living tattoo' developed

MIT scientists have developed a 3D- printed 'living tattoo' by using a new kind of ink made from genetically programmed biological cells.
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 researchers demonstrated the technique by printing a "living tattoo" - 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 or molecular compound.

When the patch is adhered to skin that has been exposed to the same compounds, corresponding regions of the tree light up in response.
"We found this new ink formula works very well and can print at a high resolution of about 30 micrometres per feature," said Professor Xuanhe Zhao from Massachusetts Institute of Technology (MIT) in the US.

"That means each line we print contains only a few cells. We can also print relatively large-scale structures, measuring several centimetres," said Zhao.
The technique, published in the journal Advanced Materials, can be used to fabricate "active" materials for wearable sensors and interactive displays, researchers said.

Such materials can be patterned with live cells engineered to sense environmental chemicals and pollutants as well as changes in pH and temperature, they said.
The team developed a model to predict the interactions between cells within a given 3D-printed structure, under a variety of conditions.
The researchers said that they can use the model as a guide in designing responsive living materials.