Project B3: Shear-induced instabilities and structure formation in colloidal nano-rods.

In the present project we plan to investigate the behavior of sheared rod-like
particles via a combination of our dynamic equations and a systematic bifurcation
analysis using continuation software AUTO. As a starting point we aim to better
understand the nature of and the transition into the bistable states appearing in
the non-equilibrium phase diagrams of homogeneous sheared systems. In particular,
we are interested in the existence of hysteresis effects resembling those encountered
in equilibrium first-order phase transitions. We will then proceed towards spatially
inhomogeneous (e.g., confined) systems, which are, so far, poorly understood. We
focus on the occurrence of spatio-temporal patterns such as traveling interfaces.
Indeed, preliminary investigations of the dynamics resulting from the full GLdG
functional have already indicated the possibility of novel behavior such as time-
dependent orientational defect structures. In a later stage of the project we will
consider even more complex situations such as shear rates with a stochastic contri-
bution (to model, e.g., rough surfaces), and systems with more dynamic variables
(such as polar nano-rods). By combining the mesoscopic dynamic equations with the
coherent structure approach we hope not only to identify interesting parameter ranges,
but also to predict new non-equilibrium phenomena in sheared anisotropic systems.

Project leaders: Prof.Dr.  S. Klapp [1],  Prof.Dr.  H. Engel [2],  Prof.Dr.  H. Stark [3]