Researchers from the University of South Carolina Viterbi School of Engineering are making use of living bacteria to create engineering materials that are robust, strong and resilient.

First revealed in the journal Advanced Materials, they are working with a special bacteria dubbed S.pasteurii which is known to secrete an enzyme dubbed urease. This urease when comes in contact with calcium ions and urea, it starts to form calcium carbonate — the very component found on our teeth and bones.

However, researchers have taken this further by guiding the bacteria to grow calcium carbonate minerals to achieve ordered microstructures identical to natural mineralised composites.

Inspired by a mantis shrimp

One of the cool things about a mineralised composite is that it can be made into different structures or patterns. Researchers observed the ability of a mantis shrimp (who are known to possess really strong claws to break into shells) and the structure of this component, only to discover that it was made in a bouligand structure — essentially a strong shape.

Wang, the Stephen Schrank Early Career Chair in Civil and Environmental Engineering and assistant professor of civil and environmental engineering in the Sonny Astani Department of Civil and Environmental Engineering explains, “ We have been amazed by the sophisticated microstructures of natural materials for centuries, especially after microscopes were invented to observe these tiny structures. Now we take an important step forward: We use living bacteria as a tool to directly grow amazing structures that cannot be made on our own.”

They trained the bacteria to develop the composite adhering to this shape to make it strong and robust. They 3D printed scaffolding with empty squares and lattice layers laid at different angles. The bacteria were then introduced in the scaffolding to help create the shape.

Crazy strength

An Xin, A CEE doctoral student who was part of the study revealed how strong the end result was, “We did mechanical testing that demonstrated the strength of such structures to be very high. They also were able to resist crack propagation—fractures—and help dampen or dissipate energy within the material.”