The effect of shape and size in micro-/nanodimples adhesion

Stiction is of major concern in the design of micro-nanoscale systems as microelectromechanical switches, micromotors, and hard-disk drives, affecting both manufacturing (release stiction) and operation (in use stiction). A current strategy to alleviate stiction relies on the microfabrication of dimples of different shape and size distributed over the interacting surfaces. In this paper, the interaction of an axisymmetric dimple with a half-space is modeled using a Lennard-Jones potential. The traction distribution at the interface is derived as a function of (i) the approach between the dimple and the half-space, (ii) the material properties (elastic modulus E and surface energy γ), and (iii) the dimple geometry. It is shown that, for a fixed tip radius, the pull-off force reduces dramatically as the lateral surface of the dimple becomes steeper. Even a small deviation from the classical parabolic profile leads to a 50% drop of the pull-off force, alleviating stiction, and to a smoother transition from the no-contact to the contact conditions (jump into contact).