US Patent 8186210 Surface evaluation employing orthogonal force measurement

A method for evaluating a performance of a substrate surface including applying a normal force with a probe to a surface of a substrate, the normal force being substantially perpendicular to the surface, and moving the probe across the surface to generate a force against and to scratch the surface, the force being substantially parallel to the surface and comprising a coaxial force along the scratch and an orthogonal force perpendicular to the scratch. The method further includes measuring a magnitude of the orthogonal force as the probe moves across the coating, and determining a fracture point of the surface by the probe based on changes in the magnitude of the orthogonal force.