Feasibility of Miniaturized Viscosity Sensors for the Characterization of Suspensions

For many applications the viscosity of a complex fluid sample is interesting to control the process and reactions. These fluids can for instance be suspensions of different types of microorganisms, e.g., bacteria or fungi. Macroscopic viscosity measurement systems would only be able to measure the global, averaged viscosity. Miniaturized TSM resonators, however, are probing only a very thin fluid film (typically only a few µm thick, depending on frequency and viscosity) on their surface. Earlier investigations with water-in-oil micro-emulsions have shown that the influence of water droplets in oil is dependent of their size. In this paper we focus on a similar effect, i.e. the influence of the surface roughness. It turns out that the sensor behaves differently if the dimension of the inclusions or particles is in the order of the surface roughness.