The MIDAS experiment for the Rosetta mission (original) (raw)
Related papers
Dynamic properties of AFM cantilevers and the calibration of their spring constants
Journal of Micromechanics and Microengineering, 2006
A hybrid method is introduced for the calibration of the spring constants of atomic force microscopy cantilevers. It is based on the minimization of the difference between the modelled and experimentally determined full-field displacement maps of the surface of the cantilever in motion at several resonant frequencies. The dynamic mechanical response of the cantilever to periodic motion is measured in a vacuum by means of a scanning vibrometer. Given the dimensions of the cantilever, the obtained surface displacements together with analytical or numerical models are used to resolve the physical unknowns of the probe. These are the elastic properties of the cantilever, and the residual stress state built up during the deposition of the reflective coating on the backside of the cantilever. The scanning vibrometry experiment allows the precise determination of the first ten resonant frequencies and the modes associated. After optimization of the elastic properties and the surface stress, the relative agreement between all resonant frequencies is better than 1% with the finite element model and 2% with the Timoshenko beam equation. The agreement between surface displacements is also excellent when the damping constant of the system has been determined, except for the first lateral mode, which exhibits strong coupling to a reflection of the first torsional mode. Because all the displacements at resonance are known, it is possible to decouple these modes, and the result is shown to compare well with the model. The cantilever being fully characterized (geometry, materials, residual stress state and boundary conditions), it is straightforward to deduce all its spring constants, in the linear and nonlinear elastic regimes.
Error quantification in calibration of AFM probes due to non-uniform cantilevers
Structural Dynamics, Volume 3, 2011
For more than two decades, the Atomic Force Microscope (AFM) has provided valuable insights in nanoscale phenomena, and it is now widely employed by scientists from various disciplines. AFMs use a cantilever beam with a sharp tip to scan the surface of a sample both to image it and to perform mechanical testing. The AFM measures the deflection of the probe beam so one must first find the spring constant of the cantilever in order to estimate the force between the sample and the probe tip. Commonly applied calibration methods regard the probe as a uniform cantilever, neglecting the tip mass and any nonuniformity in the thickness along the length of the beam. This work explores these issues, recognizing that dynamic calibration boils down to finding the modal parameters of a dynamic model for a cantilever from experimental measurements and then using those parameters to estimate the static stiffness of a probe; if the modes of the cantilever are not what was expected, for example because the non-uniformity was neglected, then the calibration will be in error. This work explores the influence of variation in the thickness of a cantilever probe along its length on its static stiffness as well as its dynamics, seeking to determine when the uniform beam model that is traditionally employed is not valid and how one can ascertain whether the model is valid from measurable quantities. The results show that the Sader method is quite robust to non-uniformity so long as only the first dynamic mode is used in the calibration. The thermal method gives significant errors for the non-uniform probe studied here.
Monitoring of an atomic force microscope cantilever with a compact disk pickup
Review of Scientific Instruments, 1999
In the present study we test a compact disk pickup as the cantilever position sensor in an atomic force microscope ͑AFM͒. The pickup is placed on top of the optical microscope used for the visual inspection and alignment of the specimen. The AFM is also equipped with its own cantilever movement sensor system. Both the built-in and the new detection devices are simultaneously active for comparison purposes. Two different measurements are performed in sequence on the same sample each using one sensor at a time as the error signal source for the AFM feedback loop. The pickup has demonstrated good sensitivity as well as excellent performance in terms of compactness, reliability, and cost.
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 %.
Applications based on cantilever sensor technology like atomic force microscopy, mass spectroscopy, magnetic resonance force microscopy, and other physical or chemical sensing techniques demand theoretical understanding of sensing and actuation mechanism. Moreover reliable calibration of any instrumentation is necessary in order to enable comparison of obtained results between various laboratories. When mass or force investigations are performed in nanoscale the reliable system calibration is even more difficult due to the lack of appropriate references and established metrological techniques. In this article we present the calibration methodology of thermally driven piezoresistive cantilevers which were used for mass and force measurements. We adapt the mass loading spring constant calibration method and compare the results obtained in this way with the method which was based on the resonance frequency detection. Additionally we will present results of the cantilever deflection sensitivity measurement and low-frequency noise properties.
Exact solutions of AFM scanning probes subjected to tip-sample forces
Journal of Mechanics of Materials and Structures, 2007
In this study, an analytical method for the static deflection of an AFM nonuniform probe subjected to tip-sample forces is presented. The effects of the Lennard-Jones and electrostatic noncontact forces and a contact force on the deflection of a cantilever are investigated. The contact force is simulated by the Derjaguin-Muller-Toporov model. In general, when an atomic force microscopy is used to measure a sample's topography and properties, a jump phenomenon of a cantilever usually exists. Unfortunately, there is a lack of a complete and precise description about this jump phenomenon. This proposed analytical method is helpful to investigate precisely the jump phenomenon. Moreover, the effects of several parameters on the jump phenomenon are studied. Finally, several simple and general relations between the deflection of beam and the tip-sample distance are presented.
An interferometric platform for studying AFM probe deflection
Precision Engineering, 2011
This paper describes an interferometric platform for measuring the full-field deflection of atomic force microscope (AFM) probes and generic cantilevers during quasi-static loading. The platform consists of a scanning white light interferometer (SWLI), holders for the cantilevers, a translation stage, a rotation (tip-tilt) stage, and an adapter plate to connect these items to the SWLI table. Visualization of cantilever bending behavior is demonstrated for snap-in against a rigid surface, cantilever-on-cantilever tests, and a damaged AFM probe. A new approach to normal force calculation using a polynomial fit to the cantilever deflection profile is also presented and verified experimentally. The method requires only the coefficient for the third order (cubic) term from the fit to the deflection profile, the elastic modulus, and the area moment of inertia for the cantilever under test.