SKM 2023 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 33: Biologically Inspired Statistical Physics (joint session DY/BP)

DY 33.1: Vortrag

Mittwoch, 29. März 2023, 15:00–15:15, ZEU 250

Comparison of fitting strategies to extract the diffusion coefficient in microrheological experiments — •Sten Leipnitz, Christian Wagner, and Thomas John — Experimental Physics, Saarland University, Saarbrücken

Tracking of small particles undergoing a Brownian motion in liquids is a widespread method in passive microrheology to extract the diffusion coefficient D, the viscosity of the sample respectively. The mean-squared displacement (MSD) is determined from particle positions as a function of the timelag MSD(τ) = σ₀² + 2nDτ + v_drift²τ², where v_drift is a possible drift velocity and σ₀ is an offset due to position detection noise in experiments. We present: the extracted parameters depend strongly on the used number of fitting points in the MSD-relation. Surprisingly, considering only the beginning of the MSD-relation in the fitting procedure leads to the best expectation value of the diffusion coefficient. This is shown by numerical simulations of the Brownian motion as well as from experimental data.