(105a) Reduced-Order Model Development for Multiphase Flow Through Patterned, Orthotropic, and Structured Porous Materials

Flow through thin porous media occurs in many industrial and consumer processes.  One example of this is the nano-imprint lithography process, where picoliter size drops are squeezed under a porous template.  This template may have regions of closed pores, where liquid will be pulled into the template but not spread, and open pores such as channels, where liquid can spread through the template, often in specifically engineered directions.  These pores are structured, with length scales on the order of tens of nanometers, so capillary forces are incredibly strong, influencing the bulk flow under the template and the deformation of the template itself.

In this presentation we detail a mesoscale model for the porous and multiphase bulk flows, including fluid-structural interactions.  Bulk flow is modeled with multiphase lubrication hydrodynamics using a level-set field to track fluid-air interfaces.  The individual features of the porous material are coarse-grained and modeled by an analytical structure representation.  The porous flow model is based on Darcy flow, but with the order reduced by integrating through the thickness of the porous material, taking into account the representation of the structure.  The coupled problem is solved using the finite element method, with 2-D shell elements for the bulk and porous flows and 3-D continuum elements for the structural deformation.  This model is used to investigate model applications, including air entrapment and fill rate in nano-imprint lithography processes.

* Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under Contract DE-AC04-94AL85000.