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Dynamic particle interactions

Background: Long range physical interactions control many short-ranged specific reactions between diffusing particles in biology, chemistry or soft matter physics. Hydrodynamic coupling between two particles can reach interaction lengths of even several particle diameters and often control time-variant effects such as reactions kinetics or synchronization in biological processes.

Problem: Until recently it has been impossible to measure the coupling of two diffusing colloids contacting each other. It is unknown, how external forces and boundaries influence the particle interactions on different time scales.

Approach Using coherent light scattering of the trapping laser we track several particles in 3D with nanometer precision at 10 kHz. Our results confirm the hypothesis that inside living cells a dynamic change of the size of membrane compartments controls the collision rate between particles and thereby reaction efficiencies.



linetrap setup   Bead trajectories    positionhistogram

The experimental setup                                                The QPD data is used to extract the particle trajectories     ...and position histograms (scalebar: 1µm)


Tracking in Linetrap



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