58 th ILMENAU SCIENTIFIC COLLOQUIUM Technische Universität Ilmenau, 08 – 12 September 2014 URN: urn:nbn:de:gbv:ilm1-2014iwk:3 ©2014 - TU Ilmenau DEVELOPMENT OF A FORCE DISPLACEMENT MEASUREMENT DEVICE FOR THE DETERMINATION OF SPRING CONSTANTS C. Diethold, M. Kühnel and T. Fröhlich Institute of process measurement and sensor technology, Technische Universität Ilmenau, Ilmenau Germany ABSTRACT This paper discusses a measurement device for the determination of force displacement curves or spring constants respectively. Especially the calibration of spring constants of atomic force microscopes (short: AFM) cantilevers is an important field of investigation and concentration of this work. The spring constant can be measured with two measurement modes. One mode uses separate force and displacement measurement devices which correspond to the state of the art. The second measurement mode is more sophisticated using one sensor which measures force as well as the displacement simultaneously; a separate nanostage is not need. The measured sample is an AFM type cantilever, its determined spring constant is in both measurement modes approximately 50 Nm -1 with a very good repeatability of 0.02 %. Index Terms - spring constant, force measurement, AFM cantilever, EMFC load cells 1. INTRODUCTION The calibration of force displacement curves (spring constants) of AFM cantilevers and the determination of force-signal curves (force sensitivity) of cantilever type micro force sensors is a known field of investigation in metrology. There are several measurement setups and measurement strategies as well as performed calibrations and international comparisons described in literature [1 … 11]. The lowest measurement uncertainty was achieved by using a static force calibration described in [3]. The current investigations at TU Ilmenau are based on a preliminary setup described in [12] and it is also related to the international state of the art, especially described by the international comparison described in [9]. The spring constant of the sample is determined by using an electromagnetic force compensated (short: EMFC) load cell. A modification of the control loop enables the possibility to set the displacement of the weighing pan and measure the acting force simultaneously [12]. Additionally it is also possible to set the displacement with a commercial piezoelectric nanostage and using the EMFC load cell for force measurement only. This is similar to other to measurement setups as described in [2], [3] and [4]. This second measurement mode can be used to verify the results of measurement mode. Both measurement modes are supposed to be used for international comparison in this field of investigation in the future. Especially measurement mode two can be used for direct comparison, as it describes the state of the art. URN (Paper): urn:nbn:de:gbv:ilm1-2014iwk-092:6