24 March, 2015
When Professor Pat Unwin talks about a state of flux, he’s not thinking of political uncertainty or economic turmoil or any of the other problems besetting our planet—he’s thinking about very, very small interactions in the equally complex nano-world.
The UK Electrochemist has been focusing his sights on developing new ways of using different microscopy techniques, allied with nanoprobes, to explore the world of interfaces and what happens there. While on an Australasian sabbatical from Warwick University, he presented his work at the recent AMN-7 Conference, the seventh on Advanced Materials and Nanotechnology sponsored by the MacDiarmid Institute.
Many processes involve chemical flux, Pat explains, from industrial technologies, to the interactions between living cells, to the weathering of rocks. Nanoscale flux imaging provides a chance to take a new and different look at the nature and type of physiochemical processes which occur across surfaces at the nanoscale.
Flux involves the flow of a physical property in a defined area over time, such as heat flow or fluid dynamics, movement of particles or photons, or changes in electromagnetic fields. These flows can be modelled with complex mathematics and, for a long time, that has been the main way of describing changes happening at the microscopic level. While it is relatively easy to observe, say, the magnitude of a river’s current as the water passes by, flux at a much smaller scale has been difficult to quantify except by averaging it out and assuming that what we can observe at the bulk level—such as the change in current flow—actually mirrors what is happening between the individual molecules or atoms.
But that’s not necessarily the complete story. “It’s very important to understand the distribution of behaviour. For the first time we can work at the individual entity level, so as to investigate the electrochemistry of single carbon nanotubes or metal nanoparticles, where previously we’ve usually had to average over millions.”
Pat and his colleagues have developed nanoprobes which can be used to quickly measure and convey in minutes gigabytes of flux data from tiny surfaces. Unlike earlier techniques, these ‘intelligent’ probes can also define clearly where they are on a surface, allowing the local structure to be related to the flux data and providing an unprecedented look at what is happening in real-time. This sort of precision is important not only in learning more about the fundamental relationships between the electrochemical processes going on, but also has implications for the many possible applications of this technology.
For example, if you can better understand how a specific area on the surface of a cell is involved in the transfer of ions and other materials into and out of the cell, then you have a better chance of developing more suitable drug-delivery technologies or cancer-defeating techniques. “In some diseases the difference between single cells can be very important,” says Pat.
He’s been working with researchers at Tohoku University in Japan to use the probes for observing cellular processes in single cells. Single-cell microscopy has tended to rely on fluorescence microscopy, which has its limitations. “We can look at things that are quite difficult to look at [with fluorescence microscopy],” says Pat. He adds that his approach can easily be combined with other forms of microscopy to ‘really enhance’ what you get from these existing techniques. Knowing more about the chemical flux across a surface will assist in the rational design of new sensing systems to provide yet more information, precision and control.
From taking a closer look at how rust forms to seeing how bacteria cause tooth decay, this new approach provides a mix of fundamental knowledge and a broad array of practical applications. “We’re trying to make a platform that can be used from materials to life sciences.” As such, Pat has been involved with researchers across a range of disciplines, with maths and computer science playing as much of a role as chemistry and physics.
Electrochemist and MacDiarmid Principal Investigator Professor David Williams has been a long-standing contact and convinced Pat to come to the AMN-7 meeting, where his presentation was described as ‘inspirational’. It’s been 400 years since Dutch draper Antonie van Leeuwenhoek amazed the world by describing the tiny animacules he could see in a drop of water. Pat Unwin looks set to delve deeper. “We live in this amazing age of microscopy where we can visualise things in detail and probe the function of surfaces,” Pat enthuses. He sees himself at just the start of the journey to provide better explanations and greater understanding of that world.