Gas-film levitated liquids: Shape fluctuations of viscous drops

A new, containerless method for measuring viscosity variations, as a function, e.g., of temperature or concentration, is described. Relative viscosities are extracted from the resonance quality factor near eigenfrequencies of deformation modes of gas-film levitated liquid drops. Both the geometrical aspect of the drop and the resonance profile are dissymmetric in general. This can be understood in terms of a parametric instability against nonlinear oscillations. The method could be useful for viscosity measurements under conditions where contact with walls should be avoided-in particular at high temperatures, in order to avoid corrosion or chemical contamination.