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Research Abstracts Online
January 2009 - March 2010

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University of Minnesota Twin Cities
Institute of Technology
Department of Civil Engineering

PI: Roberto Ballarini

Mechanics of Nano and Biological Structures

This research group focused on three project areas during this period. The first involves collagen mechanics. Collagen is an essential building block of many tissues. Owing to its hierarchical structure, it possesses superior properties. However, little is known about the mechanical properties of collagen substructures. The researchers are performing a systematic study of collagen fibrils upon uniaxial tension. To thoroughly understand collagen mechanisms, they plan to investigate the mechanical responses of collagen fibrils with stochastic distribution of cross-linking densities and defects under all kinds of loading conditions and to model collagen fibers in the future.

A second area of research is the mechanics of small-scale silicon structures. These structures are widely used in industry, but little attention is paid to investigate their failure mechanisms. Experimental results have shown that there exists brittle-to-ductile transition of small-scale silicon structures. Inspired by the findings, the researchers perform molecular dynamics simulations to probe the mechanical responses of the silicon particle with different diameters under nanoindentation. Different potential fields are applied, leading to material softening and hardening behaviors. The underlying mechanisms are associated with dislocations and phase transitions.

The third area involves the mechanics of lipid bilayer and protein channels. Mechanotransduction plays an important role in regulating cell functions and it is an active topic of research in biophysics. Recently, a continuum-mechanics-based hierarchical modeling and simulation framework has been established and applied to study the mechanical responses and gating behaviors of a prototypical mechanosensitive channel. However, the hydrophobic mismatch that might be an important source of gating is not considered. This research calibrates the mechanical properties of lipid bilayer using molecular dynamics simulations and incorporate its phenomenological continuum model in the existing continuum framework. The research is expected to give important physical insights to gating mechanisms of mechanosensitive channels

Group Members

Lucas Hale, Graduate Student
Yuye Tang, Research Associate