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Research Abstracts Online
January 2010 - March 2011

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University of Minnesota Twin Cities
College of Science and Engineering
Department of Civil Engineering

PI: Roberto Ballarini

Mechanics of Micro- and Nano-Structures

This research group focused on two project areas during this period. The first concerns breakdown mechanisms of oxide thin-film coating. Oxide films that form to protect metal substrates from corrosive environments can be severely damaged when subjected to considerable electric field. Theoretical and computational models that could describe the thinning and pitting breakdown of oxides, however, are lagging. In a preliminary study, these researchers developed a nonequilibrium thermodynamics framework to study the evolution of these films by considering the intimate coupling between the environment, the electric field, and elasticity. The study revealed the existence of a critical combination of electric field strength and initial film shapes leading to the breakdown of oxide layers. Currently, they are developing the finite element formulation based on this framework. By applying the computational framework, they can predict coatings’ responses and instantaneous morphologies considering anisotropy, finite deformation, the gradient fields, the residual stress, the substrate effects, the interaction between the fluid corrosive, the solid oxide coatings, and other factors.

The second project concerns the mechanics of lipid membrane structures. These structures are essential building blocks of cell and cellular organelles. Their material properties can significantly affect several membrane-mediated biological processes. For instance, the compressibility and bending modulus influence the ability of biomolecule binding. More accurate constitutive relationships of lipid membranes will provide a strong basis for these biological processes. In this study, the researchers are working on a more realistic phenomenological model of lipid membrane based on the result of molecular dynamic simulations and hyperelastic theories. The continuum constitutive built will be applied in the study of mechanosensitive channels in the future.

Group Members

Lucas M. Hale, Graduate Student
Minmao Liao, Graduate Student
Yuye Tang, Research Associate