What is glass and how does it shape our world?

From fiber optic cables to smartphones, glass plays a major role in the emerging technology. To learn more about how glass will shape the society of the future, we spoke with Katelyn Kirchner, a doctoral student at Penn State who is studying with John Mauro, the Dorothy Butt Enright Professor of Materials Science and Engineering at Penn State. Kirchner is the lead author and counter-author to Mauro on a recent review article on the unique properties of glass published in the journal Chemical Reviews.

The article, published last month and co-authored with an international team of scientists, is the first comprehensive look at the spatio-temporal fluctuations of glass. It is a review of experimental, computational and theoretical approaches to characterize and prove the effects of different types of fluctuations on physical properties and processes, with a primary focus on commercially relevant oxides.

Let’s start with the basics. What is glass?

This is a wonderfully complex question. The exact definition is something that is still being explored today. Glass is a non-equilibrium, amorphous state of matter that appears solid on a short time scale but continually relaxes towards the liquid state. Let’s break that down a bit. Glass is an unequilibrium material, which means that the atomic structure is not in its lowest energy, equilibrium configuration, which would be in a liquid or crystalline state. Thus, all bottles have two options: to continuously relax towards the liquid equilibrium state or to undergo a phase transition to the crystalline state.

This relaxation to the liquid state is so slow that from human observation time, the glasses appear to be solid. The fact that glass is amorphous means that the atomic structure lacks a long-range pattern, which adds additional complications when trying to predict how the atoms will be arranged. And there are many other “non-scientific” words that we could include for a more precise definition of “What is glass?” We understand glass for what it is not, but we have not fully understood what glass is. This complexity makes it exciting to be in the field of glassology, as there is still so much to explore.

Although we may not understand it, what are some of the ways in which the unique qualities of glass are being disseminated in society today?

Think of all the ways we interact with glass in our daily lives, in areas such as information technology, where glass is central to displays, augmented reality, memory storage, and optical data transmission. Then there are areas such as transportation and architecture, with vehicles and building materials, or the energy sector with photovoltaics and next-generation batteries. You can also seek healthcare with medication packaging, antimicrobial surfaces, and prescription lenses. The impact of glass on our world has been enormous.

What are you currently working on?

Right now I’m doing mostly experimental work trying to visualize the fluctuations in a glass. By “volatility” I mean spatial fluctuations, how properties vary in different areas of the glass, and I also mean temporal fluctuations, how the material changes over time.

One of the most fascinating things about glass is that these fluctuations (i.e., deviations) in the atomic composition directly affect the macroscopic properties. When I return to Penn State from a research fellowship at Hokkaido University to complete my Ph.D. With Dr. Mauro, I will work with the data I am collecting now to develop a computational framework to better understand how fluctuations in thin glass can be manipulated to achieve new proprietary behaviours.

What are some potential applications for what you’re discovering?

Optical fibers are good, because if we understand the fluctuations in the glass, we can better understand, predict, and optimize how an optical signal moves through a cable. When you think about the long distances these signals travel, we’re talking about ocean communications, and every little fluctuation has a big impact.

Every time an optical signal hits the silica walls of the cable, the local properties of the glass will affect how that signal propagates through the rest of the fibre, affecting the quality of signal transmission and the overall cost of the infrastructure. A deep understanding of how fluctuations affect glass has great potential for improving fiber optic technology, and this is just one example of the potential application.

What about the future? What new technology of the future do you think will be facilitated by glass?

This is the main part of this work. The possibilities are endless as we look to tomorrow’s applications for glass, such as developing and commercializing non-lithium-ion batteries, optimizing electronic memory storage devices, improving sustainable energy production, augmented reality interfaces, and so on.

The purpose of materials research is to better understand the basic science so that we can develop the next groundbreaking technologies, and there is no doubt that glass will play an essential role in that future.

I remember as a kid my uncle, who was a mineralogist, showing me pictures of the Hubble Space Telescope. He explained the geometry of the different materials used to facilitate the visualization of distant galaxies. Glass allowed us to see beyond our galaxy and explore the universe. It is exciting to think of all the future discoveries that will be made thanks to the glass.