Simultaneous Friction and Topographic Data

The NanoTest can be used to investigate sliding interactions between a surface and a single asperity in the form of a probe tip. To study mechanisms of friction, information can be obtained on asperity interlocking, particle adhesion and stick-slip phenomena.

Movement of the specimen causes a small deflection of a calibrated piezoresistive transducer. The resulting transducer resistance change and the probe position are measured simultaneously as the specimen is moved normal to the probe axis. The probe position is determined with a resolution better than 0.1 nm by means of the NanoTest capacitive transducer, and the normal load can be varied across the usual NanoTest range. Specimen levelling is performed automatically using a tilting specimen stage.

The example illustrated was obtained with an alumina probe sliding on a DLC surface. The correlation between the two curves indicates that mechanical interlocking is primarily responsible for variations in the frictional force, although this is superimposed on a constant frictional force.