Microscopic animals inspire innovative glass research
Prof. Juan de Pablo's 20-year exploration of the unusual properties of glass began, oddly enough, with the microscopic animals known as water bears.
These creatures have a remarkable ability to withstand extreme environments of hot and cold, and even the vacuum of space. When de Pablo read about what happens when scientists dry out tardigrades, then revive them with water years later, his interest was piqued.
"When you remove the water, they very quickly coat themselves in large amounts of glassy molecules," says de Pablo, the Liew Family Professor in Molecular Engineering at the University of Chicago. "That's how they stay in this state of suspended animation."
His passion to understand how glass forms in such exotic settings helped lead de Pablo and his fellow researchers to the unexpected discovery of a new type of glass.
"These are intriguing materials. They have the structure of a liquid, and yet they're solids. They're found everywhere, and we still do not understand how this process of turning from a liquid into a solid occurs," says de Pablo.
Their results potentially offer a simple way to improve the efficiency of electronic devices such as light-emitting diodes, optical fibers, and solar cells. They also could have important theoretical implications for understanding the still surprisingly mysterious materials called glasses.
Surprisingly ordered molecules
The molecular order that the researchers found came as a big surprise. "Randomness is almost the defining feature of glasses," de Pablo says. "At least we used to think so. What we have done is to demonstrate that one can create glasses where there is some well-defined organization. And now that we understand the origin of such effects, we can try to control that organization by manipulating the way we prepare these glasses."
De Pablo and five researchers from UChicago, Wisconsin, and France show how the vapor-deposition process can create new glassy materials by manipulating their molecular orientation.
Using vapor deposition, Wisconsin's Mark Ediger and his team create glasses in a vacuum chamber by heating a sample material, which vaporizes, condenses, and grows atop an experimental surface.
In their latest work, the researchers compared three data sets with each other: the simplified computer model of their earlier paper; a new, much more sophisticated computer model; and the experimental results.
But in the atomic-scale simulations rendered by UChicago's Midway Computing Cluster, "we can exactly specify the molecular configuration," Lyubimov says. "The area of uncertainty now is whether the model is accurate or not. Running these two models allows us to improve the certainty that this mechanism which we found is probably real."
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