unedsoftmatter / pfmcal

Calibration of optical tweezers in the high-resolution detection of the Brownian motion of spherical probes

PFMCal

https://doi.org/10.1016/j.cpc.2017.07.019

The present software is an update of the previously published MatLab code for the calibration of optical tweezers in the high-resolution detection of the Brownian motion of non-spherical probes [1]. In this instance, an alternative version of the original code, based on the same physical theory [2], but focused on the automation of the calibration of measurements using spherical probes, is outlined. The new added code is useful for high-frequency microrheology studies, where the probe radius is known but the viscosity of the surrounding fluid maybe not. This extended calibration methodology is automatic, without the need of a user’s interface. A code for calibration by means of thermal noise analysis [3] is also included; this is a method that can be applied when using viscoelastic fluids if the trap stiffness is previously estimated [4]. The new code can be executed in MatLab and using GNU Octave.

[1] A. Butykai, F. Mor, R. Gaál, P. Domı́nguez-Garcı́a, L. Forró, J. S., Cali- bration of optical tweezers with non-spherical probes via high-resolution detection of brownian motion, Comput. Phys. Commun. 196 (2015) 599 – 610.

[2] M. Grimm, T. Franosch, S. Jeney, High-resolution detection of brownian motion for quantitative optical tweezers experiments, Phys. Rev. E 86 (2012) 021912.

[3] E.-L. Florin, A. Pralle, E. H. K. Stelzer, J. K. H. Hörber, Photonic force microscope calibration by thermal noise analysis, Appl. Phys. A 66 (1998) S75–S78.

[4] P. Domı́nguez-Garcı́a, L. Forró, S. Jeney, Interplay between optical, vis- cous, and elastic forces on an optically trapped brownian particle im- mersed in a viscoelastic fluid, Appl. Phys. Lett. 109 (14) (2016) 143702.