Scientists have found a way to turn ordinary biopolymer into a high-tech, 3D-printable building material. 

The secret ingredient is sodium alginate, the exact same seaweed-derived biopolymer that makes ice cream creamy and gives popping boba its snap.

A new study led by researchers at the University of Colorado Boulder and Columbia University shows that adding a tiny amount of this food-grade ingredient to local clay and sand makes the mixture incredibly smooth for 3D printing. It also makes the final structure remarkably strong.

It was found that sodium alginate alters the electrical charges of clay particles. This causes them to repel each other, keeping the mixture stable and allowing it to flow smoothly through a 3D-printer nozzle.

“From termite mounds to adobe buildings, humans and animals have been building with earth since the dawn of time,” said Wil Srubar, professor in the Department of Civil, Environmental and Architectural Engineering. “But there hasn’t been a lot of science to how earthen builders design the materials. So, we wanted to use scientific knowledge and tools to understand it.”

Move over concrete

To change that, the team looked to nature. Termites, wasps, and honeycomb worms all build complex, durable structures without a single bag of concrete. The structures are made using biological molecules found in their own saliva to glue the earth together.

The researchers tested five different natural binders, including everyday kitchen thickeners like xanthan gum and guar gum. Most of them acted like heavy glue, binding the soil so tightly that it clogged the 3D printer.

Sodium alginate did the exact opposite. Rather than acting like glue, it changed the electrical charges on the clay particles. It made them repel one another like the matching poles of two magnets. The particles glided past each other effortlessly. It flowed like liquid, then set like stone.

Notably, the perfect recipe was unlocked by adding just 0.12 percent of the seaweed extract to raw earth dug from a Colorado quarry. The new mixture can be printed 33 percent faster than standard dirt and can withstand 25 percent more pressure.

Shows promise in testing

To prove it, a 8-millimeter-thick (0.3-inch) thin, dramatic wall was printed that slants outward at a 60-degree angle. It stood perfectly stable. For comparison, that is far steeper than the Leaning Tower of Pisa.

The environmental implications are also huge. Construction sites routinely dig up tons of soil for basements and foundations. Right now, most of that dirt is trucked away to landfills. This new method allows builders to recycle that exact waste onsite, turning a disposal headache into structurally sound walls.

Furthermore, earthen walls are natural air conditioners, which regulate indoor humidity, trap pollutants, and insulate rooms against extreme heat and cold.

Since clay and sand are widely available, the technology can be deployed anywhere. It swaps heavy, carbon-intensive concrete for the very ground beneath our feet.

While this study primarily tackles printability, the researchers note that their framework can now be used to test other natural biopolymers. This opens the door to discovering new organic additives that could further maximize the strength and long-term durability of 3D-printed earthen structures.

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