Electronic tattoos and “smart” ink technologies have enormous potential for the creation of specialized sensors, diagnostic and therapeutic medical devices. Many researchers around the world are experimenting with various “responsive” materials used in such technologies, and researchers from the Massachusetts Institute of Technology decided to use genetically modified bacteria as the active component of “ink. Printed with the help of such bacteria “living tattoo” is able to react in a certain way to a number of predetermined factors, and the type of these factors and the reaction to them is set during the process of genetic modification of the base species of bacteria used.
In the first stage, researchers from Massachusetts identified a number of microbial species that can be used as “fillers” for ink. The main criterion was the safety of these bacteria for the human body and the second one was the thickness of the cell membrane wall which had to withstand serious mechanical stresses acting on it when it exits the nozzle of the inkjet or three-dimensional printer. Besides, the selected microorganisms must survive in the environment of hydrogels, which are the basis of ink for three-dimensional printing.
To test the performance of the technology they developed, the researchers printed something resembling wood on a small piece of plastic-elastomer. Three different kinds of bacteria reacted to specific chemical stimuli. When this “living tattoo” was applied to a human hand, the bacteria successfully detected their stimuli and reacted by changing their color.
Further prospects for the development of this technology look absolutely futuristic. Researchers suggest that it can be used to create a “living computer” consisting of complex structures, each containing many types of specially designed bacterial cells. These cells can communicate with each other chemically or otherwise, like transistors on the chip of an ordinary processor, in addition, the bacteria will be able to produce certain substances that will become the basis of unique medicines, ideally suited for each individual.
But from a more down-to-earth perspective, the “living ink” technology could be used to make various “wearable” sensors that would respond to changes in human health or environmental conditions.