We are exploring a novel technique for AFM sensing, where we do sense drag in tapping mode but need to convert it into amplitude. We understand we need to characterize the cantilever mechanical parameters (essentially, I understand force constant K and quality factor Q). However, when purchasing one cantilever typically specs loosely speak of parameters and are such imprecise as 10 to 130, so no reliable force to displacement conversion may be done in practice.
Is there any provider of fully characterized cantilevers? Is there any simple method for cantilever characterization, or a drag-to-displacement model well established not sensitive to changes in the mechanical parameters of the cantilever?
Thanks in advance!
Typical probe parameters given by the supplier are simply calculated from average cantilever dimensions and the elastic modulus. As you noticed, this values spread as much as the uncertainties in probe production.
Characterization of vertical cantilever sensitivity and spring constant is state of the art the "thermal noise" or "equipartition method" is most famous among. Depending on which literature you refer to, the uncertainty varies from 20% to 5% (http://www.physics.uwo.ca/~hutter/calibration/afmcal.html and reference below). The error can be strongly reduced by using state-of-the-art laser doppler vibrometry (LDV). Bruker offers tipless probes calibrated by this method for usage with the reference cantilever method (http://www.brukerafmprobes.com/p-3242-clfc-nobo.aspx).
Calibration of lateral spring constants is still challenging. You may use Sader's method on rectangular probes (http://www.ampc.ms.unimelb.edu.au/afm/calibration.html), but still have to determine the lateral sensitivity (http://repository.upenn.edu/cgi/viewcontent.cgi?article=1084&context=meam_papers).
Article Inter laboratory round robin on cantilever calibration for A...
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