Influence of geometrical parameters on capillary forces

As miniaturization of objects and systems is further carried on, adhesion appears to be one major problem during the assembly and/or fabrication of micro-components. This paper presents a model for the computation of capillary forces. For simple geometries, this model complies with literature results. In addition, it allows the computation of capillary force for non-axisymmetrical shapes. The complexity can arise from object shape (modelling for example an AFM tip) and/or from geometrical configuration. One very important result is the ability to compute the evolution of the capillary force depending on the tilt angle of the gripper with respect to the object. Using this results, it could be possible to manipulate small (a few tens of mum of characteristic dimension) objects with capillary condensation grippers. Currently the model takes into account the contact angles, the relative humidity, temperature and the geometrical description of the problem. It is shown that it is possible to reach forces up to a few hundreds of nanonewton in magnitude. This paper also presents a test bed developed in order to validate the models.