Formation mechanism of a circumferential roller in a drying biofluid drop

Using the methods of theoretical thermohydromechanics, a model of protein roller formation at the periphery of a drying biofluid drop is constructed. As basic mechanisms of mass transfer-, temperature-, concentration-, and gravity-induced convections are considered, which produce a global toroidal flow with an ascending fluid filament at the center, dipping fluid along the free surface, and compensatory centripetal flow at the bottom. The shape of the protein roller is analyzed under the assumptions that the material deposition rate is proportional to the (i) material concentration and (ii) material flux.