简介:Frequency modulation atomic force microscopy FM-AFM is rapidly evolving as the technique of
choice in the pursuit of high resolution imaging of biological samples in ambient environments. The
enhanced stability affor简介:Frequency modulation atomic force microscopy FM-AFM is rapidly evolving as the technique of
choice in the pursuit of high resolution imaging of biological samples in ambient environments. The
enhanced stability afforded by this dynamic AFM mode combined with quantitative analysis enables
the study of complex biological systems, at the nanoscale, in their native physiological environment.
The operational bandwidth and accuracy of constant amplitude FM-AFM in low Q environments is
heavily dependent on the cantilever dynamics and the performance of the demodulation and
feedback loops employed to oscillate the cantilever at its resonant frequency with a constant
amplitude. Often researchers use ad hoc feedback gains or instrument default values that can result
in an inability to quantify experimental data. Poor choice of gains or exceeding the operational
bandwidth can result in imaging artifacts and damage to the tip and/or sample. To alleviate this
situation we present here a methodology to determine feedback gains for the amplitude and
frequency loops that are specific to the cantilever and its environment, which can serve as a
reasonable “first guess,” thus making quantitative FM-AFM in low Q environments more accessible
to the nonexpert. This technique is successfully demonstrated for the low Q systems of air Q
40 and water Q1. In addition, we present FM-AFM images of MC3T3-E1 preosteoblast cells
acquired using the gains calculated by this methodology demonstrating the effectiveness of this
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