Comment on "Print your atomic force microscope" [Rev. Sci. Instrum. 78, 075105 (2007)]

The paper of Kühner et al. [Rev. Sci. Instrum. 78, 075105 (2007)], presents a sound realization of a very nice idea. Namely, to design and prepare (via rapid prototyping) a custom head for atomic force microscope (AFM). Custom AFM heads are essential for various applications, which include the AFM force spectroscopy modes and convenient AFM coupling with other techniques. Our comment concerns the deflection data for a thermally driven AFM cantilever obtained by Kühner et al. using their AFM setup (Figure 3 therein). The results of Kühner et al. imply that a thermally excited AFM cantilever vibrates with aberrantly large amplitudes. Namely, the deflection noise amplitudes for the MLCT-D cantilever are 60-100 times larger than what is typically observed in our lab and by others. As we argue, the author's mistake is likely attributed to an improper usage of the AFM bandwidth. We explain the necessary correction and discuss the issue of bandwidth for the AFM force spectroscopy measurements.