Preprint at http://arxiv.org/abs/1605.07750 (2016)
Accurate calibration of cantilevers for atomic force microscopy (AFM) is imperative for making robust force measurements. There are a number of methods for calibrating the torsional spring constant of a cantilever for AFM. However, these calibrations are not made using a global standard so no simple method exists for comparing data from AFM labs around the world. Now, John Sader and colleagues from The University of Melbourne, along with researchers from institutions in Australia, Ireland and Sweden, have developed an online tool to standardize the calibration of cantilevers.
The Global Calibration Initiative (GCI) is an online tool (sadermethod.org) for AFM users to compare force measurements. Users upload their AFM thermal method measurements for the spring constant, resonant frequency and quality factor for a given cantilever. Their data is then averaged to reduce the uncertainty in the measured spring constant. To illustrate the initiative, calibration data from five labs were compared and large variations on individual cantilevers were observed. However, on averaging the acquired dataset, the GCI was used to accurately determine the hydrodynamic function (and thus enable calibration) of a series of unknown cantilevers. As the dataset is widened, the calibration should become more accurate, allowing calibration of any cantilever geometry.