Engineers 3-D Print A ‘Living Tattoo’

MIT engineers have devised a 3-D printing technique that uses a new kind of ink made from genetically programmed living cells. The cells are engineered to light up in response to a variety of stimuli. When mixed with a slurry of hydrogel and nutrients, the cells can be printed, layer by layer, to form three-dimensional, interactive structures and devices. The team has then demonstrated its technique by printing a ‘living tattoo’ – a thin, transparent patch patterned with live bacteria cells in the shape of a tree. Each branch of the tree is lined with cells sensitive to a different chemical or molecular compound. When the patch is adhered to skin that has been exposed to the same compounds, corresponding regions of the tree light up in response. The researchers, led by Xuanhe Zhao, the Noyce Career Development Professor in MIT’s Department of Mechanical Engineering, and Timothy Lu, associate professor of biological engineering and of electrical engineering and computer science, say that their technique can be used to fabricate active materials for wearable sensors and interactive displays. Such materials can be patterned with live cells engineered to sense environmental chemicals and pollutants as well as changes in pH and temperature.  What’s more, the team developed a model to predict the interactions between cells within a given 3-D-printed structure, under a variety of conditions. The team says researchers can use the model as a guide in designing responsive living materials. Lu provided the team with bacterial cells engineered to light up in response to a variety of chemical stimuli. The researchers then came up with a recipe for their 3-D ink, using a combination of bacteria, hydrogel, and nutrients to sustain the cells and maintain their functionality. “We found this new ink formula works very well and can print at a high resolution of about 30 micrometers per feature,” Zhao says. “That means each line we print contains only a few cells. We can also print relatively large-scale structures, measuring several centimeters.” Yuk says in the future, researchers may use the team’s technique to print “living computers” – structures with multiple types of cells that communicate with each other, passing signals back and forth, much like transistors on a microchip.

-Source: www.sciencedaily.com        

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