There's biomimetic and then there's biomimetic. Dan Luo of Cornell University and colleagues have taken the notion of materials mimicking nature to a new extreme. They have used DNA to create a life-like, dynamic material that has a kind of artificial metabolism and acts like a simulant of a biological machine. [Hamada, S. et al., Sci. Robotics (2019) DOI: 10.1126/scirobotics.aaw3512]

The team's DASH approach, DNA-based Assembly and Synthesis of Hierarchical, materials, endows their systems not only with metabolism-like traits but the fact that it forms through self-assembly and organization makes it even more life-like. As with a living organism where biosynthesis and biodegradation are key elements of self-sustainability for form and function, the new systems can carry out these tasks in a limited way that closely resembles truly living systems.

"We are introducing a brand-new, lifelike material concept powered by its very own artificial metabolism," Luo explains. "We are not making something that's alive, but we are creating materials that are much more lifelike than have ever been seen before."

DASH allows the team to take a 55-nucleotide base DNA sequence and multiply it hundreds of thousands of times to create repeating chains a few millimeters in size. This intermediate was then fed into a microfluidic device that provided a liquid flow and additional building blocks for a kind of biosynthesis to take place. The team explains that as the liquid washes over the material, the DNA begins to harvest "nutrients" from the stream and synthesize its own new strands with the front end of the material growing and the tail end degrading in an optimized balance. The material creeps forward against the flow through the device in a manner resembling the locomotion of slime molds.

Metabolic instructions programmed into the DNA is perhaps the key innovation in this work. Once initiated, however, the material is on its own and the team has even pitted one against another in biomimetic slime races. The team makes a quite strong allusion to the origins of life: "Everything from its ability to move and compete, all those processes are self-contained," Luo says. "There's no external interference." He adds that "Life began billions of years from perhaps just a few kinds of molecules. This might be the same."