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Shape-shifting clusters move beyond ‘hardware’

A Rubik’s Cube-like arrangement of nanoparticles could lead to a form of wet information storage, a team of Michigan engineers and collaborators at New York University have shown.| Medium Read

A Rubik’s Cube-like arrangement of nanoparticles could lead to a form of wet information storage, a team of Michigan engineers and collaborators at New York University have shown.

Getting away from hard and electronic silicon computing could lead to machines that work more naturally with biological systems, opening new pathways for medicine, robotics and bio-engineering.

The research team simulated how a solution of nanoparticle clusters in a liquid could work as computer information storage and made the simplest, one-bit cluster from plastic particles.

“We came up with an idea to use stuff that’s in principle easy and cheap to make, that could be made by the bucket full, and that would let us read and write information,” said Sharon Glotzer, the Stuart W. Churchill Professor of Chemical Engineering at U-M.

A conventional computer bit has two information storage states – 0 and 1. In the researchers’ new scheme, unique configurations of particles stand for different states. A memory cluster of four particles connected to a central sphere can have two states like a conventional bit. But a 12-particle cluster, for example, could have nearly 8 million unique states, representing 2.86 bytes of data or 22.9 conventional bits.

The simulation group, led by Glotzer, showed that a tablespoon of a solution containing 12-nanoparticle clusters could store a terabyte of data, at a concentration of just 3 percent, compared with a smartphone-size external hard drive it takes to store that much data electronically.

The idea for using particle clusters to store data arose from simulations of the particles performed by Carolyn Phillips and Eric Jankowski, formerly students in Glotzer’s lab but now post doctoral researchers at Argonne National Laboratory and the National Renewable Energy Lab, respectively.

“These clusters reminded me of Rubik’s Cubes and how you can solve them from one pattern to another. You can use the same mathematics that describes a Rubik’s Cube to show that every rearrangement of the cluster’s spheres is possible and reachable,” said Phillips.

How it works

In the team’s scheme, nanoparticles are attached to a central sphere. If the sphere is small, the outer particles trap one another in place, and the data is stored. If the sphere is just large enough, the particles can be reconfigured in a controlled way to store different information, using patterns of movement similar to those on a Rubik’s Cube.

The experiment, led by David Pine, a professor of physics at New York University and Stefano Sacanna, a professor of chemistry at NYU, achieved the simplest scenario for the clusters – four particles on a central sphere, all made of polymers. Kazem Edmond, a postdoctoral researcher in Pine’s group, made an unlocked cluster and observed the particles shifting between the two unique states, following the path predicted by Glotzer’s team. Color-coding the particles with fluorescent molecules to make the two states instantly distinguishable is the group’s next goal.

The team stresses that this is but a first step toward a new kind of computing. “We need to look at ways of reading and writing information to these clusters reproducibly,” said Jankowski.


The clusters could potentially be used to detect pollutants in water, among other applications. While Glotzer notes that the most interesting uses are distant, they could be revolutionary. Wet computing techniques may allow medical information processing to occur inside the body. For instance, she proposes immunity enhancers that could recognize threats and attack them or mobilize the body’s own immune system.

Likewise, the memory clusters could enable sensing and control in “soft robotics,” a branch of robotics that dispenses with the traditional metal, hinges and electronics in favor of more flexible and water-friendly materials.

More immediately, Glotzer says that the clusters could serve as a barcode of sorts for liquid materials, making it easier to track controlled substances such as fuels, explosives and precursor chemicals for illegal drugs. “If you take a droplet out and read its state, you immediately know where the material came from,” said Glotzer.

A paper describing this work, titled “Digital Colloids: Reconfigurable Clusters as High Information Density Elements” is published in the journal Soft Matter.

The research was supported by the U.S. Army Research Office, the U.S. Department of Energy, the National Science Foundation, Argonne National Laboratory and the Simons Foundation. Glotzer is also a professor of materials science and engineering, macromolecular science and engineering, physics, and applied physics.

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