Physics Team Makes Breakthrough on Abrupt Aging Soft Materials

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June 26, 2017 — Georgetown College physics professor Emanuela Del Gado landed a paper in the prestigious journal Nature Communications last week.
“Elastically driven intermittent microscopic dynamics in soft solids,” the culmination of years of research at Georgetown’s Institute of Soft Matter Synthesis and Metrology, found fascinating new properties in the aging of soft materials. Del Gado and her coauthors discovered a “snapping back” reaction that occurs when incredibly soft materials — gelatin or yogurt, for example — rupture at a microscopic level.
Some background: Molecules in soft materials, even seemingly solid ones, “wiggle” at a level imperceptible to the human eye. As time passes, this wiggling can change the material, frequently rupturing or consolidating its structure. Del Gado’s paper noted an interesting reaction to this process.
“Over those very small length scales, these materials can act as a micro rubber-band that snaps back when a microscopic rupture happens, Del Gado said. “The weaker the wiggling motion is, the stronger the rubber band snapping.”
To conduct these studies, Del Gado’s team used coarse grained Molecular Dynamics (MD), an advanced technique that uses computational physics to investigate material properties at the microscopic level. This technique had been used in this context before, but this specific study involved a new simulation strategy — one in which the MD data was combined with understanding of forces at work at different points in the structure to guess where ruptures would happen.
According to Del Gado, this represents a major development for a question that had stumped researchers for years.
“Why does this abrupt aging happen in certain materials and not in others? How do we explain apparently contradictory observations in different materials that are all, in some sense, soft? These are questions that have been around for more than 10 years — and our work managed to answer the questions and address all contradictions,” she said.
Del Gado has ...

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