Why simple salt water is so much more than it seems | Tim Duignan | TEDxUQ (2023)

Introduction

Humankind has only just touched the surface of salt water’s capabilities. It could provide an exciting solution to our environmental woes through its wide range of applications. Tim Duignan works on computer simulations and mathematical modelling of salt solutions. He received his PhD from the Australian National University in 2015 and has carried out postdoctoral research at Pacific Northwest National Laboratory in the United States. He has received a Discovery Early Career Researcher Award to work at the University of Queensland on predicting the properties of salt solutions for energy storage applications. In his talk, Tim emphasises the vital role of salt solutions and their unpredictable properties by suggesting different tools which will facilitate the design of electrolyte solutions to realise improved performance of important applications such as energy storage and CO2 capture. This talk was given at a TEDx event using the TED conference format but independently organized by a local community. Learn more at www.ted.com/tedx

Video

I study the most common substance on the surface of the earth salt water.

Now, salt water may seem to be a relatively mundane and unimportant substance, but nothing could be further from the truth salt water is actually a complex and mysterious substance that plays an important role in many of the challenges we face today.

So understanding it is incredibly important to see where this is.

We first need to know what salt water is so salt water is made up of molecules called ions that float around in water.

And just like a balloon, that's been rubbed against the carpet.

These ions carry an electrical charge sodium and chloride are among the most common ions.

But there are many others such as lithium and magnesium.

Now you've probably heard that your body is mostly water, but it's more accurate to say, your body is mostly salt water.

Our blood is about as quarter as salty as the ocean.

And without these ions complex life would actually be impossible that's because your body is a kind of electrical device constantly passing electrical signals back and forth between your brain and your body.

And these signals are carried by a flow of ions, which acts just like the electrons in a middle wire, in fact, every cell in your body has a small electrical voltage that you can measure just like the voltage of a battery in order to create these voltages, the body's developed a complex array of machines called ion pumps and ion channels to move the ions in and out of cells.

And when these break down the body can no longer move ions around as effectively and diseases can result like cystic fibrosis, a symptom of which is actually very salty sweat.

Because the body is unable to remove the ions from your sweat, adding different ions to your body can also have remarkable effects.

For example, lithium ions are somehow an effective treatment for bipolar disorder and remarkably used to be an ingredient in the soft drink seven up, presumably due to their effect on mood.

Similarly, aluminium ions are a component of vaccines that help to enhance our body's immune response.

Whereas potassium ions can be used to make a lethal injection that stops the heart from beating.

These ions aren't just important for our body, though they also play a crucial role in combating climate change by reducing our co2 emissions here, new and improved batteries are key to transitioning our economy away from our reliance on harmful fossil fuels, the main source of co2 emissions and just like our bodies batteries rely on salt water, or other salty solutions to work, and they help determine how fast a battery can charge how long it will last and how safe it will be here's.

Another example, the ocean actually absorbs around a third of the co2.

We emit each year, transforming it into carbonate ions.

And one promising idea is to build factories that harness the same mechanism to remove even more co2 from the air.

We could even improve on the ocean's ability to do this.

For example, potassium ions are more effective than the sodium ions that the ocean uses there are many many more examples like this where salt water is crucially important.

It really is everywhere.

So given how important it is, you might think that by now we must be able to predict and understand all of its fundamental properties.

But, in fact, we can't at all, we have to rely on experiments to determine almost everything we know about salt water.

For example, we can't use equations and theories to predict how much salt you can dissolve in water.

We have to rely on measurements instead, some of our predictions can even be catastrophically wrong.

For example, one study tried to predict how long it would take for salt to crystallize out of very salty water.

But the predictions turned out to be many trillions of times too fast.

This lack of understanding means that we can't predict what effect a given eye will have in a particular situation.

And this is a massive problem because it means we have to rely on luck to find the optimal ions for a given problem.

For example, lithium's ability to treat bipolar disorder, aluminium's ability to provoke an immune response and potassium's ability to accelerate co2 absorption were all discovered.

Essentially by accident.

There are almost certainly many other important uses for different ions out there, but they'll be much harder to discover so long as we can't, even explain and predict the most basic properties of saltwater.

So around a century ago, many amazing scientists, including several nobel laureates worked on this problem and developed many beautiful so-called classical theories to describe the important properties of saltwater.

But the problem with these theories is they're missing certain key pieces of information that we need to plug into them to make them work properly.

Things like the exact size of the ions in water.

And these pieces of information are the missing puzzle pieces.

We need to unlock the full potential of these classical theories.

Unfortunately, we can't get this information from experiment because to get it.

We need to be able to track precisely how the molecules move with time.

And these molecules are far too small and far too fast to see using light.

So we therefore need to use computers to make what are called molecular simulations, which allow us to track how these molecules move and make movies of it.

And this is one part of my research.

But instead of focusing on a full biological cell or a real battery I'm, starting in a much simpler place, just a single ion in pure water.

Now, this may seem to be far too simple a place to start.

But in fact, there's a great precedent for this approach.

And the inspiration from it comes from a scientist named erwin, schrodinger who solved a fundamental mystery of the universe by discovering a simple, and yet incredibly powerful equation.

This equation lies at the heart of quantum mechanics.

And it famously says that particles actually behave like waves.

But all we need to know about it is that it describes how protons electrons and neutrons move.

And because almost all matter is made up of a combination of these three things.

This equation can describe almost everything around you.

It predicts the properties of every element of the periodic table and every molecule made from them.

It can describe how every chemical reaction in your body will proceed and explains how every transistor in a computer works.

And to discover this equation, schrodinger didn't focus on the complex systems.

We ultimately wanted to understand.

But instead on a single hydrogen atom, just one proton.

And one electron once the simplest possible case was understood the same approach could be applied to larger and more complex systems.

So in principle, we should be able to use schrodinger's equation to make the molecular simulations of salt water that we need right after all salt water is just made up of molecules.

And I told you schrodinger's equation tells us everything.

We need to know about molecules, including how they move.

And while this is true in principle, it turns out it's incredibly difficult to do in practice because it needs, you need huge supercomputers to accurately solve schrodinger's equation, even for only a few molecules.

But thanks to the collective efforts of many amazing scientists and engineers, faster, algorithms and computers.

And now making it possible to actually make these simulations of salt water, using schroedinger's equation, my colleagues, and I are working on developing physical and computational techniques to make these simulations as fast as possible while still making them accurate.

For example, it turns out that even if we just focus on how roughly 100 molecules behave for a few trillionths of a second, we can extract the missing puzzle pieces that we need to understand saltwater.

We've recently shown that we can make these simulations with unprecedented accuracy.

Now so far, we've only done this for small ions and water.

But this is actually the perfect place to start, because just like the hydrogen atom, it's.

The simplest possible case once we understand it, the same approach can be applied to larger and more complex systems.

So thanks to these advances, the century-long struggle to understand seemingly simple salt water, may finally be achieved.

And this is incredibly exciting as it means.

We should no longer have to rely on luck to find the optimal ions for a given purpose.

And we can then harness for ourselves, the amazing abilities of saltwater to control the fundamental processes of life and combat climate change.

Thank you.