Richard Brutchey of chemistry and his colleagues have created a parallel reactor to improve the manufacture of nanoparticles. Image courtesy of Richard Brutchey.

Researchers find way to produce nanomaterials on a larger scale

Researchers create a system that can scale-up production of the smallest — but among the most useful — materials of this century.

ByRobert Perkins March 1, 2016

Nanoparticles — tiny particles 100,000 times smaller than the width of a strand of hair — can be found in everything from drug delivery formulations to pollution controls on cars to high-definition TV sets. With special properties derived from their tiny size and subsequently increased surface area, they’re critical to industry and scientific research.

They’re also expensive and tricky to make.

Now, researchers at USC have created a new way to manufacture nanoparticles that will transform the process from a painstaking, batch-by-batch drudgery into a large-scale, automated assembly line.

The method, developed by a team led by Richard Brutchey, associate professor of chemistry, and Noah Malmstadt of the USC Viterbi School of Engineering, was published in Nature Communications on Feb. 23.

Associate Professor of Chemistry Richard Brutchey. Photo by Matt Meindl.

Consider, for example, gold nanoparticles. They have been shown to easily penetrate cell membranes without causing any damage — an unusual feat, given that most penetrations of cell membranes by foreign objects can damage or kill the cell. Their ability to slip through the cell’s membrane makes gold nanoparticles ideal devices for delivering medications directly to cells.

However, a single milligram of gold nanoparticles currently costs about $80 (depending on the size of the nanoparticles). That places the price of gold nanoparticles at $80,000 per gram. A gram of pure, raw gold goes for only about $50.

Right now, the process of manufacturing a nanoparticle typically involves a technician mixing up a batch of chemicals by hand in traditional lab flasks and beakers. Making large amounts this way can get extremely expensive.

Brutchey and Malmstadt’s new technique instead relies on microfluidics — technology that manipulates tiny droplets of fluid in narrow channels.

“In order to go large scale, we have to go small,” Brutchey said. Really small.

The team 3D printed tubes that are about 250 micrometers in diameter. They believe them to be the smallest, fully enclosed 3D printed tubes anywhere. For reference, your average-sized speck of dust is 50 micrometers wide.

They then built a parallel network of four of these tubes, side-by-side, and ran a combination of two non-mixing fluids (like oil and water) through them. As the two fluids fought to get out through the openings, they squeezed off tiny droplets. Each of these droplets acted as a micro-scale chemical reactor in which materials were mixed and nanoparticles were generated. Each microfluidic tube can create millions of identical droplets that perform the same reaction.

This sort of system has been envisioned in the past, but scaling up has proven impossible. The parallel structure meant that if one tube got jammed, it would cause a ripple effect of changing pressures along its neighbors, knocking out the entire system. Like losing a single Christmas light in one of the old-style strands, lose one, and you lose them all.

Brutchey and Malmstadt bypassed this problem by altering the geometry of the tubes themselves, shaping the junction between the tubes such that the particles come out a uniform size and the system is immune to pressure changes.

Brutchey and Malmstadt collaborated with USC Dornsife graduate student Emily Roberts, and Malancha Gupta and Carson Riche of USC Viterbi. Their work was supported by National Science Foundation grant CMMI-1436872.

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