Evaluation of adhesion in microsystems using equivalent rough surfaces modeled with spherical caps

• A tool for the evaluation of adhesion energy in microsystems (or MEMS) is proposed in this paper.
• The proposed is model is based on a simple but effective description of surface roughness by means of spherical caps.
• Capillary attraction, van der Waals interaction forces and elasto-plastic behaviour of the asperities are included in the model.
• The proposed model is validated by means of experimental results.

The correct evaluation of adhesion energy is a challenging task and even more difficulties are found when dealing with real-life surfaces in Micro-Electro-Mechanical Systems (MEMS). In this paper, we devise an effective tool for such a computation, on the basis of an innovative, yet simple, geometrical model for the description of rough surfaces by means of spherical caps. A mechanical model is devised for the adhesive contact of spherical surfaces: the model accounts for the presence of elastic and plastic deformation and introduces the effects of both van der Waals forces and capillary attraction. The correctness of the geometrical description has been checked with reference to several measurements on realistic surfaces. The obtained results, in terms of adhesion energy, have been compared with experimental data, which are available in the literature. The agreement between measurements and numerical outcomes is satisfactory and by far better than for previously proposed models.