Nanomaterials are increasingly found across a range of industries, from electronics and pharmaceuticals to biomedical devices and the automotive sector. However, their manufacture can be time consuming and expensive, with a gram of gold nanoparticles costing around £55,000, while a gram of raw gold is priced at just £35.
"It's not the gold that's making it expensive," said Noah Malmstadt of the USC Viterbi School of Engineering, one of the research leads. "We can make them, but it's not like we can cheaply make a 50 gallon drum full of them."
The new technique, described in Nature Communications, uses tiny 3D printed tubes just 250 micrometers in diameter, which the team believes are the smallest ever made in this way. These are built in a network of four parallel tubes, and a combination of two non-mixing fluid such as oil and water is passed through them.
As the immiscible fluids fight to get out of the tube openings, they form tiny droplets that act as micro-scale chemical reactors in which materials are mixed and nanoparticles are generated. According to the USC team, each microfluidic tube can create millions of identical droplets that perform the same reaction.
Systems similar to this have been attempted in the past, but pressure problems associated with the parallel tubes have prevented them from being scaled up. The researchers overcame this by shaping the junction between the tubes so that the particles come out a uniform size and the system is immune to pressure changes.