I'm a Lewis-Sigler Theory Fellow at Princeton University. My interests include the physical properties and self-assembly of biological structures such as tissue and the cellular cytoskeleton. I use tools from soft matter physics and statistical mechanics to develop a quantitative understanding of the mechanical behavior of such systems to elucidate the function of this behavior in various biological processes.

Latest research

Updated: December 28, 2010 

Cross-link governed dynamics

One essential feature setting biopolymer networks apart from rubber-like materials is the intrinsic dynamics of their cross-links. This can have important implications for cells, where their internal networks are constantly remodeling, reflecting the transient nature of their cross-links. Recent experiments on actin networks with transient linkers provide evidence of a complex viscoelastic behavior.

To describe these systems we developed a microscopic model for the long time network relaxation that is controlled by cross-link dynamics. This cross-link governed dynamics (CGD) model describes the structural relaxation that results from many independent unbinding and rebinding events. We derived a set of nonlinear stochastic differential equations describing the time evolution of the dynamics of the polymers in the network. Using a combination of Monte Carlo simulations and a mean field approximation, we showed that this type of cross-link dynamics yields a novel power-law regime in the rheology. Our model is in excellent quantitative agreement with experiments.

Read more about this research in Physical Review Letters, 105: 238101 (2010).



Motor generated stiffening in actin networks

Reconstituted filamentous actin networks with myosin motor proteins form active gels, in which motor proteins generate forces that drive the network far from equilibrium. This motor activity can also strongly affect the network elasticity; experiments have shown a dramatic stiffening in in vitro networks with molecular motors. Here we study the effects of motor generated forces on the mechanics of simulated 2D networks of athermal stiff filaments. We show how heterogeneous internal motor stresses can lead to stiffening in networks that are governed by filament bending modes. The motors are modeled as force dipoles that cause muscle like contractions. These contractions "pull out" the floppy bending modes in the system, which induces a cross-over to a stiffer stretching dominated regime. Through this mechanism, motors can lead to a nonlinear network response, even when the constituent filaments are themselves purely linear. These results have implications for the mechanics of living cells and suggest new design principles for active biomemetic materials with tunable mechanical properties.

Read more about this paper in the MIT technology review. Or have a look at the paper itself on Arxiv.