Thermally driven Marangoni surfers

We study autopropulsion of an interface particle that is driven by the Marangoni stress arising from a self-generated asymmetric temperature or concentration field. We calculate separately the long-range Marangoni flow vI due to the stress discontinuity at the interface and the short-range velocity field vP imposed by the no-slip condition on the particle surface. Both contributions are evaluated for a spherical floater with temperature monopole and dipole moments. We find that the self-propulsion velocity is given by the amplitude of the 'source doublet' that belongs to the short-range contribution vP. Hydrodynamic interactions, on the other hand, are determined by the long-range Marangoni flow vI . Its dipolar part results in an asymmetric advection pattern of neighbouring particles, which in turn may perturb the known hexatic lattice or even favour disordered states