Abstract
The accurate calibration of the force constant of the probe in atomic force microscopy and optical tweezers applications is extremely important for force spectroscopy. The commonly used silicon detectors exhibit a complex transfer function for wavelengths >850 nm, which limits the detection bandwidth leading to serious errors in the force constant determination. We show that this low-pass effect can be compensated for using the frequency response of the detector. This is applicable for calibrations in both atomic force microscopy and optical tweezers. For optical tweezers an additional correction method is discussed based on fitting an expression in which the low-pass characteristics are already accounted for.
Highlights
In addition to high resolution imaging applications the atomic force microscope (AFM) has proven its usefulness in force spectroscopy in thenN force range where the microscope is used to measure mechanical properties of biomolecules and polymers and the strength of interand intra-molecular bonds [1, 2, 3, 4, 5]
The same cantilever was transferred to a hybrid AFM-confocal optical microscope [17] that uses a 1050 nm laser diode to prevent induced photo bleaching during simultaneous fluorescence and topography measurements
Due to the low-pass effect of silicon position detectors large errors are found in the force constant determination in AFM and optical tweezers (OT) applications
Summary
In addition to high resolution imaging applications the atomic force microscope (AFM) has proven its usefulness in force spectroscopy in the (sub)nN force range where the microscope is used to measure mechanical properties of biomolecules and polymers and the strength of interand intra-molecular bonds [1, 2, 3, 4, 5]. J.H.G. Huisstede, B.D. van Rooijen, K.O. van der Werf, M.L. Bennink and V. K.O. van der Werf, C.A.J. Putman, B.G. de Grooth, F.B. Segerink, E.H. Schipper, N.F. van Hulst and J. This frequency response was used to compensate Sx. For optical tweezers an additional correction method is discussed based on fitting an expression in which the low-pass characteristics are already accounted for.
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