Solve 1D-diffusion equation on each individual 3D cell
 

I want to solve a 1D-diffusion equation on every individual cell on my 3D mesh.
(I have 3 regions, and I want this submodel to be solved in 2 of the 3.)
I was thinking of using submesh, but it seems that selected cells are all connected which is not my case.
I want all cells to be independent while the 1D-diffusion problem is being solved.

Any good ideas? :confused: