Calibration of optical tweezers with positional detection in the back focal plane
By S. Tolić-Nørrelykke, E. Schaeffer, J. Howard, F. Pavone, F. Juelicher, Henrik Flyvbjerg. 2006
326 citations recorded by the source corpus.
We explain and demonstrate a new method of force and position calibrations for optical tweezers with back-focal-plane photodetection. The method combines power spectral measurements of thermal motion and the response to a sinusoidal motion of a translation stage. It consequently does not use the drag coefficient of the trapped object as an input. Thus, neither the viscosity, nor the size of the trapped object, nor its distance to nearby surfaces needs to be known. The method requires only a low level of instrumentation and can be applied in situ in all spatial dimensions. It is both accurate and precise: true values are returned, with small error bars. We tested this experimentally, near and far from surfaces in the lateral directions. Both position and force calibrations were accurate to within 3%. To calibrate, we moved the sample with a piezoelectric translation stage, but the laser beam could be moved instead, e.g., by acousto-optic deflectors. Near surfaces, this precision requires an improved formula for the hydrodynamical interaction between an infinite plane and a microsphere in nonconstant motion parallel to it. We give such a formula.
Subfields: Atomic and Molecular Physics, and Optics, Biomedical Engineering
View Paper: https://www.semanticscholar.org/paper/0d91dfa3b93ce7fd263f1a8ef5eb0418140d9439
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Citations in the corpus
- Microrheology with optical tweezers: data analysis (2012, methodology): “using the power spectrum or the drag force [18, 56, 57]), equation (6) provides the only such measurement that is independent of the viscoelastic properties of the fluid under investigation and is thus essential for proper calibration.”