Sandcastles inspire new nanoparticle binding technique

August 5, 2015 by Mick Kulikowski, North Carolina State University
NC State researchers develop a technique to assemble nanoparticles into filaments (left) in liquid. The filaments can be broken (middle) and then re-assembled (right). Credit: Bhuvnesh Bharti.

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.

In a paper published this week in Nature Materials, researchers from North Carolina State University and the University of North Carolina-Chapel Hill show 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, INVISTA Professor of Chemical and Biomolecular Engineering at NC State and the corresponding author of the paper.

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

Chilling the oil is like drying the sandcastle. 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 chains will re-form if the temperature is raised, the oil liquefies and an is applied to the particles.

"In other words, this material is temperature responsive, and these soft and flexible structures can be pulled apart and rearranged," Velev said. "And there are no other chemicals necessary."

"This research was the result of collaboration initiated by the NSF Materials Research Science and Engineering Center that facilitates interactions between Triangle universities." said Michael Rubinstein, John P. Barker Distinguished Professor of Chemistry at UNC and one of the co-authors of the paper.

Explore further: Environmentally friendly lignin nanoparticle 'greens' silver nanobullet to battle bacteria

More information: Nanocapillarity-mediated magnetic assembly of nanoparticles into ultraflexible filaments and reconfigurable networks, Nature Materials (2015) DOI: 10.1038/nmat4364

Related Stories

'Supercool' material glows when you write on it

May 13, 2015

A new material developed at the University of Michigan stays liquid more than 200 degrees Fahrenheit below its expected freezing point, but a light touch can cause it to form yellow crystals that glow under ultraviolet light.

Researchers create 'nanofiber gusher'

March 19, 2015

Creating large amounts of polymer nanofibers dispersed in liquid is a challenge that has vexed researchers for years. But engineers and researchers at North Carolina State University and one of its start-up companies have ...

Recommended for you

Bright colors produced by laser heating

January 15, 2019

Most of the colors on today's paper and fabric are made using dyes or pigments. But colors can also be produced by modifying a material's surface at the nanoscale, causing the surface to reflect or scatter different frequencies ...

Pore size influences nature of complex nanostructures

January 15, 2019

Building at the nanoscale is not like building a house. Scientists often start with two-dimensional molecular layers and combine them to form complex three-dimensional architectures. And instead of nails and screws, these ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.