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January 6, 2016

Sandcastles inspire new nanoparticle binding technique (Image 2)

Researchers have developed a technique to assemble nanoparticles into filaments in liquid, as seen here in this image. The filaments can be broken and then reassembled.

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Researchers at North Carolina State University (NC State) and the University of North Carolina-Chapel Hill have found if you want to form very flexible chains of nanoparticles in liquid in order to build tiny robots with flexible joints or make magnetically self-healing gels, you need to revert to childhood and think about sandcastles.

The researchers found that magnetic nanoparticles encased in oily liquid shells can bind together in water, much like sand particles mixed with the right amount of water can form sandcastles.

"Because oil and water don't mix, the oil wets the particles and creates capillary bridges between them so that the particles stick together on contact," said Orlin Velev, the INVISTA Professor of Chemical and Biomolecular Engineering at NC State and the corresponding author of a paper published about the study.

Adds Bhuvnesh Bharti, a research assistant professor of chemical and biomolecular engineering at NC State and first author of the paper, "We then add a magnetic field to arrange the nanoparticle chains and provide directionality."

The researchers found reducing the temperature from 45 degrees Celsius to 15 degrees Celsius freezes the oil and makes the bridges fragile, leading to breaking and fragmentation of the nanoparticle chains. Yet the broken nanoparticle chains will reform if the temperature is raised, the oil liquefies and an external magnetic field is applied to the particles.

The research was the result of a collaboration initiated by the National Science Foundation (NSF) Triangle Center for Excellence for Materials Research and Innovation: Programmable Assembly of Soft Matter, an NSF Materials Research Science and Engineering Center that facilitates interactions between Triangle universities (grant DMR 11-21107).

To learn more, see the NC State news story Sandcastles inspire new nanoparticle binding technique. (Date image taken: 2015; date originally posted to NSF Multimedia Gallery: Jan. 6, 2016) [See related image Here.]

Credit: Bhuvnesh Bharti and Orlin Velev, Chemical and Biomolecular Engineering, North Carolina State University

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