'Live tattoo' can glow to warn pollution

Not only does beauty help, this has many useful uses such as detecting contaminants in the environment or changes in body temperature and pH.

Tattoos are divided into sections containing live bacteria , capable of fluorescence when exposed to special compounds. When the patch on the skin comes into contact with these substances, the bacteria recognize the chemical that makes the branches on the tattoo light up.

Research and improvement of stimulant-sensitive materials to turn them into smart materials has been going on for decades. For example, a material that reacts to heat can be used to create self-assembled robots or moving robots. And a material capable of reacting to chemicals is used as a chemical sensor.

We all know that 3D printing is an easy way to create low-cost adjustable objects. So it is extremely popular among scientists when they want to create experimental objects in laboratory settings - including the creation of stimulating sensitive materials.

A group of engineers led by Professor Xuanhe Zhao of the Massachusetts Institute of Technology has realized that they can use living cells.

Create "live" tattoos.(Photo: Advanced Materials).

Previous studies in this area have shown that mammalian cells will not work in the way MIT scientists expect. They cannot exist in the harsh conditions of 3D printing, such as pressure during the process of being pushed out or exposed to ultraviolet light during cross-linking - this is the usual method. to create 3D printing materials.

The study's co-author Hyunwoo Yuk said: "During the experiment we found that these cells die slowly during the printing process. Because of mammalian cells. They are mainly made up of bubbles with simple double lipid layers, they are too weak and easily broken. '

On the other hand, bacterial cells also have protective cell walls, so it is more difficult to use them in making materials. However, these cells are compatible with most hydrogels - water and polymer materials used for many medical and laboratory applications.

Based on that, the team found a way to use genetically programmed bacterial cells capable of fluorescence when reacting to chemicals. Scientists have developed an ink made of hydrogel, cells, and a nutrient mixture to keep cells alive.

This ink provides very good results, which can be used to print objects up to 30 micrometers high. The team printed the test sample on an elastic substance, then applied it to the skin. After a few hours, parts of the plant model light up when bacteria are in turn exposed to chemical stimuli.

Researchers have also designed bacterial cells that can 'communicate' with each other and fluoresce when they receive a certain signal from another cell. They tested this 3D structure by combining a hydrogel fiber with a 3D printed glass coating. Tattoos only glow where they come in contact with cells and when they receive a 'contact' signal .

Researcher Yuk said: "This is a very potential project in the future, we hope to be able to print 'live' computing platforms that we can bring with people." In the short term, the team is seeking to produce chemical sensors as well as programmed drug delivery systems to transport drugs or glucose into the body.

"Live" tattoos have many applications and can be used to detect contaminants in the environment or changes in body temperature and pH.

The study was funded by the Naval Research Office, the National Science Foundation, the National Institutes of Health and the Military Nano Technology Institute at MIT. Research has been published in Advanced Materials.