Instead of the mammalian cells that have been used so far in laboratories for similar experiments and which die off during the printing process, a research team at the Massachusetts Institute of Technology (MIT) uses bacteria. These are compatible with a printable hydrogel blend that also contains nutrients for the bacteria. The cells light up when stimulated by certain stimuli and thus act as detectors. The MIT scientists have already demonstrated the technology by 3D printing a "living tattoo," a thin, transparent plaster in which the cells are housed in the shape of a tree. Each branch responds to another chemical or molecular compound.

Researchers ultimately want to use the process to develop sensors or interactive displays that capture environmental chemicals and contaminants as well as changes in pH level and temperature. In the long term, they are even thinking of a kind of "living computer" on the skin.