Fluid thinking saving the planet

The revolutionary vortex fluidic device (VFD) has the world of chemistry in a spin, writes COLIN RASTON Understanding how fluids flow has been one of the great unsolved questions of science.

Iwanted to make a difference and 25 years ago I completely embraced the concept of Green Chemistry. The idea says, “Let’s start all over again and make chemistry ‘benign by design’.”

As chemists, we can’t just keep doing more of the same without regard to the environment. Enough’s enough. And I think society finally gets it. Despite what some politicians were trying to tell us even a few years ago, climate change is real – it’s measurable. We’ve got bushfires and floods. And we’ve got plastics in the environment and in the oceans.

In chemistry, it’s gone from being almost like a moral obligation to go down that green path to a question of time before it’s a legal obligation.

The 12 Principles of Green Chemistry, laid out by Paul Anastas and John Warner, say that you don’t just tweak a process to make it cleaner, because you only get so far – you’re still going to generate waste if you use the same toxic reagents in your process.

Green

Chemistry is not a band-aid approach.

It’s making sure that we don’t create something that has a negative impact on the environment, and is sustainable. When it was first proposed, it was a paradigm shift, and as president of the Royal Australian Chemical Institute, I helped get a lot of people involved. That ultimately led to securing the Australian Research Council Centre of Excellence in Green Chemistry.

Globally, it’s now a big movement. These days, if you’re doing any kind of chemistry and applying to a funding agency, and you don’t take on board the principles of Green

Chemistry, it’s highly unlikely you will get that funding.

Early in my research in Green Chemistry I was interested in applying these green concepts into continuous flow processing. It’s a no-brainer: if you’re doing your research and you pass some liquid through a reactor and it’s flowing through and flowing out, then you can do all the fundamental science, and guess what? Unlike batch processing, it’s got scalability already factored into it from the outset, so that the same research device can be your processing device. This way you can fast-track production, potentially bypassing the pilot stages that you’d normally have to do for conventional batch processing.

I was thinking about trying to make nanomaterials under continuous flow, and

In 2015, Professor Raston was awarded an Ig Nobel Prize “for inventing a chemical recipe to partially un-boil an egg.” Today, the VFD (right) is being used in hundreds of applications, with no end in sight

I wanted to do it by applying clean mechanical energy rather than adding any kind of auxiliary chemical. And that ultimately led to the design of the vortex fluidic device – the VFD. This is the device that won me and my colleagues the Ig Nobel Prize in 2015.

Understanding how fluids flow has been one of the great unsolved questions of science. Now, by understanding how liquids flow in our vortex fluidic device, simply by applying mechanical energy, we take a huge step forward. The application potential is immense.

We recently published a paper in Chemical Science showing how immiscible liquids behave at very small dimensions. Immiscible liquids are the ones you don’t normally think of mixing – like oil and water. But we showed how the VFD can mix immiscible fluids down to nanometre dimensions. It took over 100,000 experiments to figure it out, but the consequences are huge. We’re making emulsions with implications for everything from drug delivery to salad dressings.

We published on this recently in Nature: Science of Food. We put nanoparticles of fish oil into apple juice. If you use a homogeniser, then everyone can taste and smell the fish oil. But if you make it at nanometre scale in the VFD, kids can’t tell the difference between drinking apple juice and drinking apple juice with all the good Omega 3 in it.

So, what’s the VFD? It’s basically a rotating test tube with a little lip at the top, and you tilt it off axis at 45°. You’ve got liquid in there, and then you introduce spinning mechanical energy into that liquid. Now you’ve got the maximum cross-factor gravity pushing down, and you have centrifugal force holding the liquid against the tube.

The device is only 20mm in diameter and about 20cm long, but you can build bigger units for high-volume processing. That’s all it is. You can have jet feeds delivering reagent liquids to the inside of the tube. And as they’re whirling up and coming out of the tube, they’re undergoing all these changes. This is your continuous flow process.

With this device, you get the formation of Faraday waves in the liquid, and you get Coriolis forces from the base of the tube. And all this mechanical energy is imparted down to less than one micron in dimension regimes. Knowing this is the key to all these other wonderful applications.

With the VFD we can partially unboil an egg, which we do by refolding proteins. Protein folding is a huge deal for the pharmaceutical industry. We’ve also been able to accelerate a variety of enzymatic reactions, which is another big deal.

A paper has just come out showing how we can make graphene oxide. There are lots of applications of graphene oxide, but the way they traditionally make it uses concentrated sulfuric acid and toxic metals. We’ve developed a process using our VFD with close to zero waste. All you need is aqueous hydrogen peroxide and graphite. We call it GGO – green graphene oxide. It’s trademarked.

We’ve also published work on using the VFD to extract DNA out of extinct species that have been preserved in formalin. Some of these species are over 150 years old.

We are using the VFD to amplify the detection of biomarkers. Initially, it was focused on COVID-19 – a test that took four hours comes down to four minutes in the VFD. In the future there are some good applications of the VFD in wine processing because you’re not adding chemicals. At certain processing parameters, we can cut carbon nanotubes down to specific lengths for applications in devices. That’s very big too.

Because we now understand the fluid flow in the device, it’s accelerating more and more applications. Even though we’ve published over 100 papers on applications of the VFD, we still haven’t got to the end of the beginning.

My interest in chemistry “exploded” in year 12 at John Curtin High School in Perth in 1967. My chemistry teacher blew my mind. He was very young – Mr Stockdale. He’d been teaching in the country, but he came to Curtin – and he just had it all together.

Our school overlooked Fremantle Harbour, and at the time they were blasting for a deep water channel. We would look out the classroom window and periodically see these massive plumes of water going up after these explosions. And he’d say, “Oh, I can do better than that.”

He’d then set up experiments that were very exciting. But afterwards we’d sit down and go through all the chemistry to explain it. It was then I realised that if you completely understand your chemistry, you understand your surroundings. I haven’t looked back.