Flow Patterns Induced by the Thermocapillary Effect and Resultant Structures of Suspended Particles in a Hanging Droplet

We focus on the flow patterns and resultant structures of suspended solid particles in a hanging droplet caused by the thermocapillary effect. A droplet is hung on a heated cylindrical rod facing downward, and another cooled rod is placed just beneath the droplet to create the temperature difference between both ends of the droplet. As the temperature difference increases, the induced flow exhibits transitions from an axisymmetric time-independent steady state to three-dimensional time-dependent oscillatory states. These flow states are judged through detecting spatiotemporal correlations between the behaviors of the particles and the variation of the temperature over the droplet surface. We find that the particle accumulation structures are realized in this geometry and that their structures vary as a function of the intensity of the thermocapillary effect.