Researchers at MIT have developed a “living ink” that responds to its surroundings. Basically, it is a 3D printed tattoo (based on hydrogel) that can sense and respond to stimuli. The hydrogel consists of bacteria, which could be made to glow as it meets certain chemicals.

3D Printed tattoo
Image Source: Advanced Science News/YouTube (screenshot)

Commercial uses of this 3D printed tattoo

In the demonstration, the MIT researchers inked the hydrogel in a tree pattern, and every tree branch consisted of bacteria, which were sensitive to different types of chemicals. The chemicals were then applied on a person’s skin before putting the tree-shaped hydrogel on it. As the branches contacted the chemicals, the bacteria glowed.

The 3D printed tattoo could be used in various applications like drug delivery and surgical implants, where cells could be engineered to produce compounds such as glucose, which could be siphoned in to the body as and when it’s required.

According to the researchers, Professor Xuanhe Zhao and Dr. Timothy Lu, the technique can be used in fabricating the active materials for wearable sensors and interactive displays. These bacteria can work together with the live cells to identify the environmental chemicals and pollutants along with the alterations in the pH and temperature, they said.

“This is very future work, but we expect to be able to print living computational platforms that could be wearable,” said Hyunwoo Yuk, one of the researchers.

Giving examples of commercial applications for the technology, another researcher, Xinyue Liu, stated that bacteria cells can be used like workers in a 3-D factory to produce drugs with a 3D scaffold. Liu further noted that it could also be used beyond epidermal devices, and as long as the fabrication method and approach were viable, applications such as implants and ingestibles could be possible.

How is it better than earlier experiments?

While MIT researchers are not the first to experiment with 3D printing genetically engineered cells, they have by far attained maximum success in the area. Talking of the mammalian cells used in the earlier experiments, Yuk noted that mammalian cells are lipid layer balloons and thus are unfit for the printing process.

In comparison, “Bacterial cells have tough cell walls that are able to survive relatively harsh conditions, such as the forces applied to ink as it is pushed through a printer’s nozzle,” the researcher explained.

Researchers also mentioned that bacteria works well with most of the hydrogels, a gel-like material consisting of water and a polymer. MIT researchers used hydrogel with pluronic acid that has an ideal consistency for 3D printing. One of the researchers noted that the hydrogel has the right amount of flow for printing through a nozzle.

“It’s like squeezing out toothpaste,” Zhao said, adding that the ink flows out of the nozzle like toothpaste, and maintains its shape after it is printed.

This living ink technology, however, is still in its early stages, and it remains to be seen when it will become a reality and have real-world applications. The research was published in Advanced Materials, and for more information you can check out this video.