Thickness-dependent attraction or repulsion between defects on a thin elastic film.

We examine elastic interaction between two defects on one side or two sides of an isotropic thin film. We show that the tangential and normal forces contribute to the interaction in a coupled manner. Our finding is that the attraction or repulsion between two defects exhibiting twofold symmetry is dependent on the film thickness. The result is of particular importance for probing elastic interaction between adherent cells which have been commonly treated as twofold surface defects.