Testing surface properties in the nano range at the University of Hamburg

Bio-mechanical characterization of materials is achieved via instrumented indentation tests. Universal nanomechanical tester UNAT's two fully independent measuring heads allow it to operate as a tensile testing instrument and profilometer, in addition to being a hardness, wear and scratch tester.

Measuring instruments for testing the bio-mechanical properties of surfaces and materials are used in research and higher education institutes as well as in industry. The Mammals Department of the Zoological Museum of the University of Hamburg is currently studying the diet of herbivorous mammals. Many food plants form biogenic opal, which is deposited in cells. These opal phytoliths, as they are known, wear teeth down and are therefore the focus of a specialized area of research financed by the German Research Foundation (DFG), in which the determination of indentation hardness is of considerable importance. Up to now far too little has been known about the wear processes accompanying chewing. To enable analysis of the properties of opal phytoliths in the micro and nano-ranges and determine the corresponding parameter sets, use is made of an Asmec nanomechanical tester.

The UNAT universal nanomechanical tester is designed for mechanical characterization of surfaces and thin coatings in the micro and nano ranges up to a maximum force of 2N. What makes this solution special is the use of two completely independent measuring heads for the measurement of normal and of lateral force-displacement curves, with resolution in the nanometer range. This allows this instrument to be used as a tensile testing instrument and profilometer as well as for hardness, wear and scratch tests. Indentation tests on opal phytoliths are carried out using a diamond Berkovich indenter, with an indentation force of 5mN. The surface is subsequently recorded at 500x magnification.

The UNAT nanoindenter enables high-productivity, fully automatic measurements, as well as measurements on large and generally flat surfaces without the need to divide them up. This is made possible by a mobile measuring head which can be mounted on an instrument frame for automatic measurements, or simply dismounted for mobile measurements. It additionally possesses integrated passive vibration damping. This has the advantage that precise, high-resolution measurements are possible without active vibration damping or containment