Researchers create 3D-printed living soil walls that can sustain plant development

Assistant professor Ji Ma, research professor David Carr, and assistant professor Ehsan Baharlou from the University of Virginia came together to make these 3D-printed walls. They have proven it is possible to 3D-printing geometrically complicated structures made from soil and seed, introducing substantial development in bio-based building and construction.

Spencer Barnes, a student involved in the research project, explored soil-based inks. Utilizing a desk-sized 3D printer, he tried two approaches. The first approach was printing soil and seed in sequential layers, and the second approach was integrating dirt and seed prior to printing. Both approaches worked. Barnes produced a round model that looked like a Chia pet.

The researchers' prototypes start to look like common raw-earth structures. After a few days, the structures grew sprouts of greenery over their surface.

“We moved to soil-based ‘inks’ to gain the benefits from circular additive manufacturing,” Baharlou said.

“We are working with local soils and plants mixed with water; the only electricity we need is to move the material and run a pump during printing. If we don’t need a printed piece or if it isn’t the right quality, we can recycle and re-use the material in the next batch of inks.”

"3D-printed soil tends to lose water faster and keeps a more powerful hold on the water it has," Ma says. "Because 3D printing makes the environment around the plant drier, we need to integrate plants that like drier environments. The factor we believe this holds true is that the soil gets compressed. When the soil is squeezed through the nozzle, air bubbles are pressed out. When the soil loses air bubbles, it keeps water more firmly."

Next the researchers will think about connecting the 3D printing device to a moving robot to produce constructions that are taller and more complex with many sides.

The scientists anticipate that the added height will cause issues like soil splitting even worse in this next phase, hence they will require an improved recipe for their "soil inks."

“Regardless of the material – plastic, metal, clay, soil, or plant life – in the end, it’s a materials problem,” Ma describes. “The additive manufacturing process creates uncertainties and opportunities within the material system you’re working with that’s different from conventional systems. You can approach this in different ways. You can try to avoid it and be afraid of it. Or you can try to control it and take advantage. That’s the long-term goal of our research program.”