Discussion Forum

Dear all,

I am a begginer in COMSOL and I need some help in my model.

I have a geometry that you can see in the attachments. The idea is to have a "cilium" that bends with a fluid and, in its base, a thin-film that will change its resistence with the deformation of the base. I am using the physics Fluid-Structure Interaction and Electric Current and I know that my model works because I can compute it and see variations in the thin-film resistence with the displacement of the mechanical struture. My problem is that this only works if I choose a thickness of some um for my thin-film and my desired thickness is 200nm. When I change to the desired thickness, I can not generate the mesh and I got an error because the value is too small.

So, I try to use the Electrical Current Shell to overcome this problem. The thin-film is not extruded (it is only a work plane) and I set the 200nm in the shell thinkness definition of the Electrical Current Shell physics. I now compute the model and get the deformation of the base, however, now the electrical resistance do not change. I think this is happening because the Linear Elastic Material of the Fluid-structure Interaction is responsable for the deformation set of the materials. However, it is only for domains and my thin film is not a domain anymore (it is set as a work plane). So without the Linear Elastic Material, maybe the displacement is not computed for the thin film? I also tried to use the Thin Elastic Layer for Boundaries, but I cannot select the thin-film.

Summing up: In my first model, I cannot generate a mesh with a thickness of 200nm of my thin-film. In my second model, I use a Shell option for my thin-film but I think I cannot compute its displacement because I cannot include it in the Linear Elastic Material of the Fluid-Structure Interaction.

Hope you can give me some help of what I should do, or what I am not doing right. Thank you very much.