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Hydrogel remembers its shape -- just add water

Hydrogel seen under electron microscope
Hydrogel seen under electron microscopeLuo Lab / Cornell University
Hydrogels made in the form of the letters D, N and A collapse into a liquid-like state on their own but return to the original shape when surrounded by water.Luo Lab / Cornell University

Scientists have created a shape-remembering material out of synthetic DNA that is eerily reminiscent of T-1000, the liquid metal assassin in the hit sci-fi film Terminator 2.

“It is almost as soft as water and it is still gel. And water you cannot stretch, but this gel can stretch. That is why it is very, very unusual,” Dan Luo, a professor of biological and environmental engineering at Cornell University, told NBC News.

The material is a new kind of hydrogel, a mesh of organic molecules with many empty spaces that can absorb water like a sponge. Hydrogels are found everywhere from self-healing contact lenses to an instrument on a NASA spacecraft that gathered flecks of comet dust

Luo and his colleagues created their hydrogel out of synthetic DNA, a building block for self-assembling materials that they make with the assistance of special enzymes. 

“This is a very long strand of DNA. They are so long that they entangle into each other and become a gel,” he explained. 

The gel is waterlike, but stretchable. When poured into a mold, it takes the shape of the mold. Remove the gel from the liquid, though, and it collapses into a liquid-like blob. When the gel is put back into water, “it’s like a rubber band, it snaps back into the original shape,” Luo said.

Click here to see a video of the hydrogel snapback into the letters D N A. 

Why, exactly, it behaves this way is unknown, Luo added. The team suspects the gel is so weak it is unable to hold its shape under gravity. In water, buoyancy cancels out the gravity, so it is able to rebound to the shape of the mold.

“Snapback is the current understanding, but this is the first time it has ever been made, so we are still working on (understanding) the mechanism,” he said.

The gel is unlikely to take the form of a metallic assassin anytime soon. Rather, the team envisions using the hydrogel as perhaps a drug delivery vehicle. 

“It can remember its own first shape. In that sense, it remembers the history. And it flows. So you can predict what shape it takes … that kind of control is very, very good in many applications such as drug delivery,” Luo explained.

A paper on the material appeared in the Dec. 2 issue of Nature Nanotechnology

John Roach is a contributing writer for NBC News Digital. To learn more about him, check out his website. For more of our Future of Technology series, watch the featured video below.