Measurement of pull-off force for planar contact at the microscale

During micro-assembly processes, surface forces influence the behavior of micro-objects more than volumic forces. Generally contacts happen between a microgripper and a micro-objet or a substrate and a micro-object. The pull-off force which represents the force required to break a contact is one of the predominant problem in micro-assembly. Now, current force measurements are mostly focused on sphere-plane geometries and models are based on nanoscale theories. The aim of this article is to propose a measurement setup able to evaluate the pull-off force for a planar contact (most frequent kind of contact in micro-assembly). Experimental force measurements based on a capacitive microforce sensor and micro/nano robotic system are carried out. The proposed device enables the study of pull-off forces according to the preload force and the contact angle. Finally experimental results are discussed and compared with a model.