Optimization of adhesion mode atomic force microscopy resolves individual molecules in topography and adhesion

The force sensor of an atomic force microscope (AFM) is sensitive enough to measure single molecular binding strengths by means of a force–distance curve. In order to combine high-force sensitivity with the spatial resolution of an AFM in topography mode, adhesion mode has been developed. Since this...

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Bibliographic Details
Published in:	Ultramicroscopy Vol. 80; no. 2; pp. 133 - 144
Main Authors:	Willemsen, O.H, Snel, M.M.E, van Noort, S.J.T, van der Werf, K.O, Grooth, B.G.de, Figdor, C.G, Greve, J
Format:	Journal Article
Language:	English
Published:	Amsterdam Elsevier B.V 01-10-1999 Elsevier Science
Subjects:	Atomic force microscopes Evaluation Studies as Topic Exact sciences and technology Force mapping Humans Instrumentation Instruments, apparatus, components and techniques common to several branches of physics and astronomy Intercellular Adhesion Molecule-1 - metabolism Intercellular Adhesion Molecule-1 - ultrastructure Microscopy, Atomic Force - instrumentation Microscopy, Atomic Force - methods Molecular recognition Physics Scanning probe microscopes, components and techniques Single molecules Surface Properties Molecular recognition Instrumentation Force mapping 07.79.Lh 018 Single molecules Atomic force microscopy Image recognition Fixation Molecular bending Mapping Experimental study
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Summary:	The force sensor of an atomic force microscope (AFM) is sensitive enough to measure single molecular binding strengths by means of a force–distance curve. In order to combine high-force sensitivity with the spatial resolution of an AFM in topography mode, adhesion mode has been developed. Since this mode generates a force–distance curve for every pixel of an image, the measurement speed in liquid is limited by the viscous drag of the cantilever. We have equipped our adhesion mode AFM with a cantilever that has a low viscous drag in order to reach pixel frequencies of 65 Hz. Optimized filtering techniques combined with an auto-zero circuitry that reduces the drift in the deflection signal, limited high- and low-frequency fluctuations in the height signal to 0.3 nm. This reduction of the height noise, in combination with a thermally stabilized AFM, allowed the visualization of individual molecules on mica with an image quality comparable to tapping mode. The lateral resolution in both the topography and the simultaneously recorded adhesion image are only limited by the size of the tip. Hardware and software position feedback systems allows individual molecules to be followed in time during more than 30 min with scan sizes down to 60×60 nm 2
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0304-3991 1879-2723
DOI:	10.1016/S0304-3991(99)00099-6