Fig. 3: Raft asymmetry.
From: Clustering induces switching between phoretic and osmotic propulsion in active colloidal rafts
A Schematic overlayed to a microscope image indicating the asymmetry vector b and the angle β between b and the cluster velocity vc. The scale bar is 5 μm, however the location of the hematite in the scheme has been exaggerated (not on scale). B Experimentally measured asymmetry parameter χ = b/a versus cluster area A, being a the cluster radius. The continuous line is an inverse square root law from which we extract the prefactor κ = 0.858 ± 0.019 μm. Top left inset shows the distribution of angles β between vc and the vector b pointing from the cluster center to the hematite particle from experiments (filled symbols) and simulations (open circles). In both cases the continuous lines are wrapped normal distributions and the error bars results from the statistical average of different measurements. C Polar plot showing the probability distribution from the experimentally measured angle β (scattered red disks) for different clusters characterized by different number of shells ns, where each shell is made of passive particles encircling the active one. The continuous green line is a non-linear regression of the data assuming wrapped normal distributions with one or two peaks. The different graphs have been obtained from a total of 30 separate experiments.
