(6cg) Multiscale Modeling of Viscoelastic Flow and Complex Fluids in Micro/nanofluidics

Conventional flow simulation based on constitutive equations (CE) cannot predict different viscoelastic flow behaviors because it does not establish the relationship between microscopic structure of polymer chain and macroscopic properties of viscoelastic fluids. A mesocopic concurrent multiscale approach named CONNFFESSIT (?Calculation of Non-Newtonian Flow: Finite Elements and Stochastic Simulation Technique') has been applied to solve this problem by combining the Brownian dynamics simulation (BDS) and the finite element method (FEM). Currently the simplest dumbbell model is used to mimic single linear polymer chain and has successfully achieved stable simulation results at a higher Weissenberg number than the conventional methods. More advanced models using bead-spring and bead-rod chains are under investigation in order to simulate viscoelastic flow in complex geometries with much higher Weissenberg number, which is commonly observed in polymer processing.

The coarse-grained Brownian dynamics simulations using the bead-spring and bead-rod chain models have also been used to simulate single polymer dynamics in micro/nanofluidics. Hydrodynamic and electrokinetic micro/nanofluidic flows are first solved by the macroscopic finite element method and the calculated flow and electric fields are imported as an input for Brownian dynamics simulation. Thus this is a hierarchical multiscale simulation. Previous work is concentrated on DNA dynamics in micro/nanofluidic flows and the quantitative and qualitative agreements have been obtained between the simulation and experimental results. Currently the simulation efforts are focus on the hydrodynamic interactions (HI) between DNA chain and the confined geometries using a concurrent multiscale simulation technique named SRD (?Stochastic Rotation Dynamics').

References:

1. X. Hu, Z. Ding, and L. J. Lee, ?Simulation of 2D Transient Viscoelastic Flow Using the CONNFFESSIT Approach?, Journal of Non-Newtonian Fluid Mechanics 127, 107-122 (2005).

2. X. Hu, C. Liu, G. Xu, and L. J. Lee, ?Viscoelastic Flow in Micro-Injection Molding?, Proceedings of Society of Plastic Engineers Annual Technical Conference, Paper #: 0450 (2007).

3. Y.-J. Juang, S. Wang, X. Hu, and L. J. Lee, ?Dynamics of Single Polymers in a Stagnation Flow Induced by Electrokinetics?, Physical Review Letters 93, 268105 (2004).

4. X. Hu, S. Wang, Y.-J. Juang, and L. J. Lee, ?A Five-Cross Microfluidic Network Design Free of Coupling between Electrophoretic Motion and Electroosmotic Flow?, Applied Physics Letters 89, 084101 (2006).

5. Y.-J. Juang, X. Hu, S. Wang, L. J. Lee, C. Lu, and J. Guan, ?Electrokinetic Interactions in Microscale Cross-Slot Flow?, Applied Physics Letters 87, 244105 (2005).

6. S. Wang, X. Hu, and L. J. Lee, ?Dynamic Assembly by Electrokinetic Microfluidics?, Journal of the American Chemical Society 129, 254-255 (2007).

7. H. C. Jung, W. Lu, S. Wang, L. J. Lee, and X. Hu, ?Etching of Pyrex Glass Substrates by Inductively Coupled Plasma Reactive Ion Etching for Micro/Nanofluidic Devices?, Journal of Vacuum Science & Technology B 24(6), 3162-3164 (2006).

8. X. Hu, S. Wang, and L. J. Lee, ?Single Molecular Dynamics in a Tapering Contraction-Expansion Microchannel with Electrophoresis?, (to be submitted).

9. S. Wang, X. Hu, and L. J. Lee, ?Electrokinetic Transport of Rigid Particles and DNA Molecules through Polymeric Nanonozzle Array?, (to be submitted).

10. Y. Yang, M. C. Cheng, X. Hu, D. Liu, R. Goyette, L. J. Lee, and M. Ferrari, ?Low Pressure Carbon Dioxide Enhanced Polymer Self-Diffusion Below the Glass Transition Temperature?, Macromolecules 40(4), 1108-1111 (2007).