A team of German and Dutch scientists have discovered an unknown state of matter, liquid glass, in which individual particles are able to move but are unable to rotate. This will have a long-reaching effect in the field of material science.
Glass as a material is truly peculiar. Although solid, its components are not organized in a neat crystalline structure like those of other solids. The fact that its molecules get frozen in place before they can organize themselves into a crystal has long interested scientists. And now, the quest to understand glass has led to the discovery a new state of matter: liquid glass.
A team of scientists from Germany and the Netherlands were able to create this unexpected state of matter using a technique called confocal microscopy. They managed to achieve the state of liquid glass with particles that were able to flow, but couldn’t rotate. As reported in the Proceedings of the National Academy of Sciences, this new state gives insight into how regular glass might form.
The investigation started out focusing on the use of colloids. These are mixtures of “large” particles dispersed through a second substance – gels and emulsions are a good example. This type of substances can experience many phenomena that occur in glass-forming material, so they are a good proxy to study how glass transitions.
However, the research team involved in this study attempted something new. Instead of using spherical particles in their colloid, as previous studies did, they manufactured special elliptical (egg-shaped) particles. They eventually discovered the unusual liquid glass behavior by changing the concentration of these in the mixtures.
“Due to their distinct shapes our particles have orientation – as opposed to spherical particles – which gives rise to entirely new and previously unstudied kinds of complex behaviors,” senior author Professor Andreas Zumbusch, from the University of Konstanz, said in a statement. “At certain particle densities orientational motion froze whereas translational motion persisted, resulting in glassy states where the particles clustered to form local structures with similar orientation.”
What the researchers saw in this particular substance were two competing glass transitions. One was a regular phase transformation, which is reversible. The other was a non-equilibrium one, which is irreversible. This combination might be what produces the peculiar properties of glass.
“This is incredibly interesting from a theoretical vantage point,” says Dr Matthias Fuchs, professor of soft condensed matter theory at the University of Konstanz and the other senior author on the paper. “Our experiments provide the kind of evidence for the interplay between critical fluctuations and glassy arrest that the scientific community has been after for quite some time.”
Theoretical investigations of liquid glass have been going on for at least two decades. The scientific community agrees that this new result will have a long-reaching effect in the field of material science.
We can’t wait to see it.