Lateral force calibration of an atomic force microscope with a diamagnetic levitation spring system

A novel diamagnetic lateral force calibrator (D-LFC) has been developed to directly calibrate atomic force microscope (AFM) cantilever-tip or -bead assemblies. This enables an AFM to accurately measure the lateral forces encountered in friction or biomechanical-testing experiments at a small length...

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Bibliographic Details
Published in:Review of scientific instruments 2006-06, Vol.77 (6), p.065105-065105-13
Main Authors: Li, Q., Kim, K.-S., Rydberg, A.
Format: Article
Language:English
Subjects:
ACCURACY
ANISOTROPY
ATOMIC FORCE MICROSCOPY
CALIBRATION
COMPARATIVE EVALUATIONS
DATA PROCESSING
DEFORMATION
FRICTION
GRAPHITE
INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
LEVITATION
MAGNETS
MOLECULES
TESTING
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Summary:A novel diamagnetic lateral force calibrator (D-LFC) has been developed to directly calibrate atomic force microscope (AFM) cantilever-tip or -bead assemblies. This enables an AFM to accurately measure the lateral forces encountered in friction or biomechanical-testing experiments at a small length scale. In the process of development, deformation characteristics of the AFM cantilever assemblies under frictional loading have been analyzed and four essential response variables, i.e., force constants, of the assembly have been identified. Calibration of the lateral force constant and the “crosstalk” lateral force constant, among the four, provides the capability of measuring absolute AFM lateral forces. The D-LFC is composed of four NdFeB magnets and a diamagnetic pyrolytic graphite sheet, which can calibrate the two constants with an accuracy on the order of 0.1%. Preparation of the D-LFC and the data processing required to get the force constants is significantly simpler than any other calibration methods. The most up-to-date calibration technique, known as the “wedge method,” calibrates mainly one of the two constants and, if the crosstalk effect is properly analyzed, is primarily applicable to a sharp tip. In contrast, the D-LFC can calibrate both constants simultaneously for AFM tips or beads with any radius of curvature. These capabilities can extend the applicability of AFM lateral force measurement to studies of anisotropic multiscale friction processes and biomechanical behavior of cells and molecules under combined loading. Details of the D-LFC method as well as a comparison with the wedge method are provided in this article.
ISSN:0034-6748
1089-7623
DOI:10.1063/1.2209953