Fig. 3: Total interaction potential obtained from optical tweezer experiments in the absence and the presence of attraction. | Nature Communications

Fig. 3: Total interaction potential obtained from optical tweezer experiments in the absence and the presence of attraction.

From: Determining intrinsic potentials and validating optical binding forces between colloidal particles using optical tweezers

Fig. 3

Panel (a): Grey-filled circles denote experimental data for U(r) obtained for polystyrene beads with a diameter of 2R = 500 nm suspended in a water-based buffer (PBS 1X, λD ≈ 0.7 nm)46. The blue dash-dotted line shows the optical tweezer (OT) harmonic potential Utrap(r) determined experimentally. The red solid line shows the fit of the optical binding potential Utrap(r) + UOB(r) using Eq. (2) and α, ϕ-values taken from Fig. 2. UOB(r) from the fit is shown as a purple dashed line. Subtracting both contributions (OT+OB), we obtain the intrinsic particle-particle (PP) potential \({U}_{{{{{{{{\rm{intr}}}}}}}}}(r)\) shown by green solid squares. These results reproduce the data shown in Fig. 2a) (∥ polarization). b Same analysis after adding 2 mM of the blockcopolymer pluronic F108 which are forming micelles and induce depletion attraction. The dash-dotted lines have been vertically offset for clarity. In both cases, the laser power settings differ, impacting the parameter ‘A’ in Eq. (2).

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