Slippery concepts: Tiny interactions explain massive phenomena

Posted on 06. Oct, 2011 by in Academic Departments, Annual Report, Issues, Materials Science and Engineering, Research

An earthquake conjures images of massive tectonic plates shifting and ocean waves heaving across the planet. To understand such interactions  better, Materials Science and Engineering Associate Professor Izabela Szlufarska is looking at them on the molecular level.

Szlufarska researches the phenomena that result from coupling chemistry and mechanics, with specific focus on adhesion and friction. For example, her group has discovered that dry nanoscale contacts follow different laws of friction from those typically encountered in larger engineering contacts. In small enough contacts, friction can be described as a sum of forces that arise from individual bonds formed across the sliding interface. Shallow tectonic earthquakes can be viewed as frictional instabilities. Since water is ubiquitous in these environments, understanding the effects of water and humidity on friction is of critical importance.

Szlufarska’s group is performing quantum mechanical molecular dynamics simulations of friction between quartz surfaces in the presence of water. The team discovered that in static, or non-sliding, contact, the rate of formation of chemical bridges across the quartz interface slows down with time because, once formed, these bridges interact with each other.

The phenomenon is particularly important because it implies that during the time when surfaces are stuck together, the strength with which the surfaces adhere to one another increases logarithmically with time—a dependence that has been observed for these systems in laboratory conditions and used as a phenomenological law in earthquake mechanics.

Szlufarska also is applying her expertise in mechano-chemistry to the effects of chemical environments on cell migration in the context of cancer research. In particular, she is exploring how chemical pathways inside a cell, as well external chemical stimuli, couple to the ability of the cell to adhere to a substrate and its ability to migrate. UW crest

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