Observation of viscoelastic solutions with ferromagnetic stirrers

Viscoelasticity in fluids is present in many common substances, from paints and glues to ketchup and mayonnaise. The rheological behavior of fluids can be accurately studied with laboratory equipment and encompasses an active area of research. However, instead of precisely analyzing the viscoelastic parameters, some applications simply require the detection of presence of viscoelastic behavior in fluid. This is desirable in online biofilm monitoring, for instance, where it is important to discern inorganic accumulation (shown as purely Newtonian behavior) from biofilms (viscoelastic behavior). Therefore, this study presents a simple method for potentially detecting the presence of viscoelastic behavior in a fluidic sample. Two sample solutions were compared: glycerol as the Newtonian fluid and a solution of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) as the viscoelastic fluid. They were compared by observing the rotational response of a magnetic particle in a rotating magnetic field, where the presence of underdamped oscillations was attributed to the viscoelasticity of the fluid. According to these preliminary results, the setup may be used to detect the presence of viscoelastic behavior in the fluid.