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Hello everyone,

I'm trying to model a system comprised of multiple overlapping graphene flakes. In the beginning, I am only interested in the DC electrical properties. I can easily introduce an anisotropic conductivity in COMSOL but I run into problems when the values of the in-plane and out-of plane conductivity differ too greatly.

Let's say, I'd like to model two overlapping graphene flakes. I cannot use the boundary layer method in this case so I model them as very thin 3d objects. I apply a voltage to the edges of the flakes and compute the current through the whole structure. I use a swept mesh with a thickness of 1 cell for each flake. Obviously, the overlapping part is the limiting portion of this model. However, when I go to very small out-of-plane conductivities such that no current should be able to flow, I end up with a finite total current. When analyzing the structure, I find that the current turns to a surface current and basically skips the overlap. It runs across the top of the lower flake into the bottom of the upper flake - despite the thickness of only one cell.

Do you have any idea how I could solve this problem? Can I set suited properties for the face where the two flakes are intesecting? I'd rather not insert an additional 3D layer between the two flakes since this would change the whole geometry...