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

O.H. Willemsen, M.M.E. Snel, S.J.T. van Noort, Kees van der Werf, B.G. de Grooth, Carl Figdor, Jan Greve

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    9 Citations (Scopus)

    Abstract

    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 nm2.
    Original languageUndefined
    Pages (from-to)133-144
    Number of pages12
    JournalUltramicroscopy
    Volume80
    Issue number2
    DOIs
    Publication statusPublished - 1999

    Keywords

    • IR-60709
    • Molecular recognition
    • METIS-128411
    • Instrumentation
    • Single molecules
    • Force mapping

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