Integrated simulation tools for fluid-structure interactions in bio-nano systems

The characterization and modeling of complex biological and nanoscale systems has reached a stage that various levels of details can be resolved. The immersed electrokinetic finite element method (IEFEM), which couples fluid-structure interaction problem with multiphysics features such as cell-cell interaction and electrokinetics, is proposed for solving a class of bio-nano-fluidics problems. In this method, independent solid meshes move in a fixed background field mesh that models the fluid and electric field. This simple strategy removes the need for expensive mesh-updates. Furthermore, the reproducing kernel particle functions enable efficient coupling of various immersed deformable solids with the surrounding viscous fluid in the presence of an applied electric field. We have applied this method to model the human cardiovascular system, especially to determine how cellular scale interactions influence the macroscopic property of the blood. Many of the complex rheological and mechanical properties observed in experiments, such as rouleau formation of deformable blood cells and shear-rate dependent viscoelasticity of blood have been effectively and efficiently modeled. In particular, the IEFEM is being used for modeling the electrokinetic-induced mechanical motion of particles in a fluid domain under an applied electric field. The electric force on a particle is calculated by the Maxwell stress tensor method. For the first time, three-dimensional assembly of particles of various geometries and electrical properties have been comprehensively studied using the new method. Simulation of the dynamic process of electro-manipulation of individual and multiple cells agrees well with experimental data. As a specific application, 3D dielectrophoretic assembly of nanowires across micro-electrodes has been studied. The various dynamic processes and assembled patterns are explored by comparing our simulation results with experimental observations. The simulations are being used to determine operating parameters for optimal deposition yield of nanoelectronic devices. The HEMS sensors will be used for the measurement of cell traction forces for the understanding of the focal adhesion and cell motility.