MIT Engineers Invent 3D Printed Tattoo Made of Living Cells

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Using a 3D printer, scientists have created a living tattoo which might be used for the next generation of wearable devices.

Engineers from the Massachusetts Institute of Technology (MIT) have generated a brand new ink out of genetically programmed living cells which are engineered to light up in reaction to many different stimuli.

The cells can be printed, layer by layer, to form 3D, lively structures and devices when combined with a slurry of hydrogen and nutrients.

“We discovered this new ink formula works very well and can print in a high resolution of about 30 micrometers per attribute,” Xuanhe Zhao, the Noyce Career Development Professor at MIT’s Department of Chemical Engineering, said in a statement. “That means each line we print comprises only a few cells. We can also print relatively large-scale structures, measuring several centimeters.”

The researchers could print a slim, transparent patch patterned with live bacteria cells in the form of a tree, in which each division is lined with cells sensitive to another chemical or molecular chemical.

The corresponding regions of the tree light up in reaction, when the Patch is stuck to skin that has been exposed to exactly the same compounds.

The new technique can be used to fabricate active substances for wearable sensors and interactive displays, where materials could be patterned with live cells engineered to feel environmental chemicals and pollutants as well as changes in pH and temperature.

The researchers also developed a model to predict the interactions between cells within a given 3D printed structure which can be used as a guide in designing usable living materials.

For many years, researchers have unsuccessfully attempted to use live mammalian cells to function as responsive materials for 3D-printed inks. The cells are too feeble and readily digestible.

However, the team discovered a hardier cell type in bacteria which has tough cell walls that can survive relatively harsh circumstances. The bacteria is also compatible with most hydrogels–gel-like materials that are made from a mixture of mostly water along with a polymer.

For the analysis, the investigators used a hydrogel using pluronic acid which exhibited an ideal consistency for 3D printing.

“This hydrogel has ideal flow attributes for printing through a nozzle,” Zhao said. “It is like squeezing out toothpaste. You need [the Ink] to stream out of a nozzle such as toothpaste, and it may maintain its Shape after it is published.”