Manipulating molecules with fluids

Fluids are fiendishly unpredictable, but fluid dynamics is a very useful area of science. With a machine called a Vortex Fluidic Device, it’s possible to manipulate molecules in very neat and specific ways – like refolding proteins to unboil an egg.

“How fluid flows is one of the grand challenges of science,” says Colin Raston, a professor of nanotechnology at Flinders University in Adelaide.

Raston’s Vortex Fluidic Device (VFD), which he started developing 10 years ago, uses precise flows to control molecules – both their reactivity and the structures they form. It won Raston an Ig Nobel award in 2015 for egg-unboiling.

“I had a hunch that by rotating this tube not vertically, or horizontally, there would be fluid flow in there which we could harness to do chemistry,” he says.

The Vortex Fluidic Device is a tube about the length of a forearm. When filled with a liquid solution, and rotated at a 45° angle, the liquid and gas within the device ripple in precise, predictable patterns. It is these patterns that allow the researchers to control molecules and proteins.

The device has already been used to make a range of useful chemicals (including the anaesthetic lidocaine). But up until recently, Raston and his colleagues didn’t fully understand how the fluid moved within the device. “The question was always: ‘how does it do what it does?’,” says Raston.

“You can’t measure from the outside what’s happening on the inside, because it’s moving relative to you.”

Now, a paper published in Nanoscale Advances uses data from over 100,000 experiments to show precisely how fluids move within the device.

“There’s only one unique answer, but it took all those experiments to find out what’s going on,” says Raston.

The researchers were able to establish that the device uses three different flowing motions to change molecules, shown in the animation above: a ‘spinning top’ flow, a double helical flow and specular flow.

“It was a real Eureka moment,” says Raston.

“Now we understand it, we’re in a very unique position. We can actually predict, for any application, what’s the starting point, what’s the right solvent mixture, what’s the right solvent. So the power of the Vortex Fluidic Device has gone up exponentially.”

Raston says there will be more applications for the VFD in medical and pharmaceutical research, food processing, and green chemistry.

A second paper published in Chemical Communications expands on this, showing how the device can coat particles without generating waste – something that could be useful in drug-coating. The second paper shows that the device can be used to coat polystyrene beads with fullerene (C₆₀) in an efficient and waste-free way.

“This could be beneficial towards the pharmaceutical companies which coat drugs with significant lower yield, thus leading to run off of dangerous chemicals into freshwater streams and the air,” says Matt Jellicoe, a PhD candidate at Flinders and first author on the paper.

He adds that the VFD could possibly be used as a drug-coating device. “This is what excites me the most. The potential impact, especially on the environment and the economy, could be unfathomable.”

“When I started down this path, many colleagues were saying ‘It’s just a rotating tube. It’s not going to do anything,” says Raston. “But from a practical point of view I knew things were happening immediately, because the very first experiment we did was to formulate graphene, just in a rotating tube.”

He says that developing and working with the device is “the craziest thing I’ve ever done.”

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