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A team led by scientists at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) found a way to make a liquid-like state behave more like a solid, and then to reverse the process.

They put a droplet of a liquid containing iron oxide nanocrystals into an oily liquid containing tiny polymer strands.

They found that a chemical additive in the droplet can compete with the polymer -- like a tiny tug of war -- on nanoparticles at the intersection of the liquids.

They were able to cause the nanoparticles assembled here to jam, making it act like a solid, and then to unjam and return to a liquid-like state by the competitive push-pull action of the polymer and the additive.

"The ability to move between these jammed and unjammed states has implications for developing all-liquid electronics, and for interacting with cells and controlling cellular functions," said Tom Russell of Berkeley Lab's Materials Sciences Division, who co-led the study with Brett Helms, a staff scientist at Berkeley Lab's Molecular Foundry. The Molecular Foundry is a DOE Office of Science User Facility that specializes in nanoscience research.

"We were able to watch these droplets undergo these phase transformations in real time," Helms said. "Seeing is believing. We are looking at the mechanical properties of a 2D liquid and a 2D solid." The results were published online Aug. 3 in Science Advances.

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Category: Science